Root bacterial endophytes alter plant phenotype, but not physiology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henning, Jeremiah A.; Weston, David J.; Pelletier, Dale A.

Plant traits, such as root and leaf area, influence how plants interact with their environment and the diverse microbiota living within plants can influence plant morphology and physiology. Here, we explored how three bacterial strains isolated from the Populus root microbiome, influenced plant phenotype. Here, we chose three bacterial strains that differed in predicted metabolic capabilities, plant hormone production and metabolism, and secondary metabolite synthesis. We inoculated each bacterial strain on a single genotype of Populus trichocarpa and measured the response of plant growth related traits (root:shoot, biomass production, root and leaf growth rates) and physiological traits (chlorophyll content, netmore » photosynthesis, net photosynthesis at saturating light–A sat, and saturating CO 2–A max). Overall, we found that bacterial root endophyte infection increased root growth rate up to 184% and leaf growth rate up to 137% relative to non-inoculated control plants, evidence that plants respond to bacteria by modifying morphology. However, endophyte inoculation had no influence on total plant biomass and photosynthetic traits (net photosynthesis, chlorophyll content). In sum, bacterial inoculation did not significantly increase plant carbon fixation and biomass, but their presence altered where and how carbon was being allocated in the plant host.« less

Root bacterial endophytes alter plant phenotype, but not physiology

DOE PAGES

Henning, Jeremiah A.; Weston, David J.; Pelletier, Dale A.; ...

2016-11-01

Plant traits, such as root and leaf area, influence how plants interact with their environment and the diverse microbiota living within plants can influence plant morphology and physiology. Here, we explored how three bacterial strains isolated from the Populus root microbiome, influenced plant phenotype. Here, we chose three bacterial strains that differed in predicted metabolic capabilities, plant hormone production and metabolism, and secondary metabolite synthesis. We inoculated each bacterial strain on a single genotype of Populus trichocarpa and measured the response of plant growth related traits (root:shoot, biomass production, root and leaf growth rates) and physiological traits (chlorophyll content, netmore » photosynthesis, net photosynthesis at saturating light–A sat, and saturating CO 2–A max). Overall, we found that bacterial root endophyte infection increased root growth rate up to 184% and leaf growth rate up to 137% relative to non-inoculated control plants, evidence that plants respond to bacteria by modifying morphology. However, endophyte inoculation had no influence on total plant biomass and photosynthetic traits (net photosynthesis, chlorophyll content). In sum, bacterial inoculation did not significantly increase plant carbon fixation and biomass, but their presence altered where and how carbon was being allocated in the plant host.« less

Physiological responses of planting frozen and thawed Douglas-fir seedlings

Treesearch

M. Anisul Islam; Kent G. Apostol; Douglass F. Jacobs; R. Kasten Dumroese

2008-01-01

We studied the short-term (7-day) physiological responses of planting thawed and frozen root plugs of Douglas-fir (Pseudotsuga menziesii) seedlings in 2 separate experiments under cool-moist and warm-dry growing conditions, respectively. Our results showed that shoot water potential, root hydraulic conductance, net photosynthesis (A), and...

Molecular Physiology of Root System Architecture in Model Grasses

NASA Astrophysics Data System (ADS)

Hixson, K.; Ahkami, A. H.; Anderton, C.; Veličković, D.; Myers, G. L.; Chrisler, W.; Lindenmaier, R.; Fang, Y.; Yabusaki, S.; Rosnow, J. J.; Farris, Y.; Khan, N. E.; Bernstein, H. C.; Jansson, C.

2017-12-01

Unraveling the molecular and physiological mechanisms involved in responses of Root System Architecture (RSA) to abiotic stresses and shifts in microbiome structure is critical to understand and engineer plant-microbe-soil interactions in the rhizosphere. In this study, accessions of Brachypodium distachyon Bd21 (C3 model grass) and Setaria viridis A10.1 (C4 model grass) were grown in phytotron chambers under current and elevated CO2 levels. Detailed growth stage-based phenotypic analysis revealed different above- and below-ground morphological and physiological responses in C3 and C4 grasses to enhanced CO2 levels. Based on our preliminary results and by screening values of total biomass, water use efficiency, root to shoot ratio, RSA parameters and net assimilation rates, we postulated a three-phase physiological mechanism, i.e. RootPlus, BiomassPlus and YieldPlus phases, for grass growth under elevated CO2 conditions. Moreover, this comprehensive set of morphological and process-based observations are currently in use to develop, test, and calibrate biophysical whole-plant models and in particular to simulate leaf-level photosynthesis at various developmental stages of C3 and C4 using the model BioCro. To further link the observed phenotypic traits at the organismal level to tissue and molecular levels, and to spatially resolve the origin and fate of key metabolites involved in primary carbohydrate metabolism in different root sections, we complement root phenotypic observations with spatial metabolomics data using mass spectrometry imaging (MSI) methods. Focusing on plant-microbe interactions in the rhizosphere, six bacterial strains with plant growth promoting features are currently in use in both gel-based and soil systems to screen root growth and development in Brachypodium. Using confocal microscopy, GFP-tagged bacterial systems are utilized to study the initiation of different root types of RSA, including primary root (PR), coleoptile node axile root (CNR) and leaf node axile root (LNR) during developmental stages of root formation. The root exudates also will be quantified and preliminary data will be used to engineer our microbial consortium to improve plant growth.

Pulpal status of human primary teeth with physiological root resorption.

PubMed

Monteiro, Joana; Day, Peter; Duggal, Monty; Morgan, Claire; Rodd, Helen

2009-01-01

The overall aim of this study was to determine whether any changes occur in the pulpal structure of human primary teeth in association with physiological root resorption. The experimental material comprised 64 sound primary molars, obtained from children requiring routine dental extractions under general anaesthesia. Pulp sections were processed for indirect immunofluorescence using combinations of: (i) protein gene product 9.5 (a general neuronal marker); (ii) leucocyte common antigen CD45 (a general immune cell marker); and (iii) Ulex europaeus I lectin (a marker of vascular endothelium). Image analysis was then used to determine the percentage area of staining for each label within both the pulp horn and mid-coronal region. Following measurement of the greatest degree of root resorption in each sample, teeth were subdivided into three groups: those with physiological resorption involving less than one-third, one-third to two-thirds, and more than two-thirds of their root length. Wide variation was evident between different tooth samples with some resorbed teeth showing marked changes in pulpal histology. Decreased innervation density, increased immune cell accumulation, and increased vascularity were evident in some teeth with advanced root resorption. Analysis of pooled data, however, did not reveal any significant differences in mean percentage area of staining for any of these variables according to the three root resorption subgroups (P > 0.05, analysis of variance on transformed data). This investigation has revealed some changes in pulpal status of human primary teeth with physiological root resorption. These were not, however, as profound as one may have anticipated. It is therefore speculated that teeth could retain the potential for sensation, healing, and repair until advanced stages of root resorption.

Physiological minimum temperatures for root growth in seven common European broad-leaved tree species.

PubMed

Schenker, Gabriela; Lenz, Armando; Körner, Christian; Hoch, Günter

2014-03-01

Temperature is the most important factor driving the cold edge distribution limit of temperate trees. Here, we identified the minimum temperatures for root growth in seven broad-leaved tree species, compared them with the species' natural elevational limits and identified morphological changes in roots produced near their physiological cold limit. Seedlings were exposed to a vertical soil-temperature gradient from 20 to 2 °C along the rooting zone for 18 weeks. In all species, the bulk of roots was produced at temperatures above 5 °C. However, the absolute minimum temperatures for root growth differed among species between 2.3 and 4.2 °C, with those species that reach their natural distribution limits at higher elevations also tending to have lower thermal limits for root tissue formation. In all investigated species, the roots produced at temperatures close to the thermal limit were pale, thick, unbranched and of reduced mechanical strength. Across species, the specific root length (m g(-1) root) was reduced by, on average, 60% at temperatures below 7 °C. A significant correlation of minimum temperatures for root growth with the natural high elevation limits of the investigated species indicates species-specific thermal requirements for basic physiological processes. Although these limits are not necessarily directly causative for the upper distribution limit of a species, they seem to belong to a syndrome of adaptive processes for life at low temperatures. The anatomical changes at the cold limit likely hint at the mechanisms impeding meristematic activity at low temperatures.

iTRAQ-based analysis of changes in the cassava root proteome reveals pathways associated with post-harvest physiological deterioration.

PubMed

Owiti, Judith; Grossmann, Jonas; Gehrig, Peter; Dessimoz, Christophe; Laloi, Christophe; Hansen, Maria Benn; Gruissem, Wilhelm; Vanderschuren, Hervé

2011-07-01

The short storage life of harvested cassava roots is an important constraint that limits the full potential of cassava as a commercial food crop in developing countries. We investigated the molecular changes during physiological deterioration of cassava root after harvesting using isobaric tags for relative and absolute quantification (iTRAQ) of proteins in soluble and non-soluble fractions prepared during a 96 h post-harvest time course. Combining bioinformatic approaches to reduce information redundancy for unsequenced or partially sequenced plant species, we established a comprehensive proteome map of the cassava root and identified quantitatively regulated proteins. Up-regulation of several key proteins confirmed that physiological deterioration of cassava root after harvesting is an active process, with 67 and 170 proteins, respectively, being up-regulated early and later after harvesting. This included regulated proteins that had not previously been associated with physiological deterioration after harvesting, such as linamarase, glutamic acid-rich protein, hydroxycinnamoyl transferase, glycine-rich RNA binding protein, β-1,3-glucanase, pectin methylesterase, maturase K, dehydroascorbate reductase, allene oxide cyclase, and proteins involved in signal pathways. To confirm the regulation of these proteins, activity assays were performed for selected enzymes. Together, our results show that physiological deterioration after harvesting is a highly regulated complex process involving proteins that are potential candidates for biotechnology approaches to reduce such deterioration. © 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.

Using low energy x-ray radiography to evaluate root initiation and growth of Populus

Treesearch

Ronald S., Jr. Zalesny; A. L. Friend; B. Kodrzycki; D.W. McDonald; R. Michaels; A.H. Wiese; J.W. Powers

2007-01-01

Populus roots have been studied less than aboveground tissues. However, there is an overwhelming need to evaluate root initiation and growth in order to understand the genetics and physiology of rooting, along with genotype x environment interactions.

Plant Survival and Mortality during Drought Can be Mediated by Co-occurring Species' Physiological and Morphological Traits: Results from a Model

NASA Astrophysics Data System (ADS)

Tai, X.; Mackay, D. S.

2015-12-01

Interactions among co-occurring species are mediated by plant physiology, morphology and environment. Without proper mechanisms to account for these factors, it remains difficult to predict plant mortality/survival under changing climate. A plant ecophysiological model, TREES, was extended to incorporate co-occurring species' belowground interaction for water. We used it to examine the interaction between two commonly co-occurring species during drought experiment, pine (Pinus edulis) and juniper (Juniperus monosperma), with contrasting physiological traits (vulnerability to cavitation and leaf water potential regulation). TREES was parameterized and validated using field-measured plant physiological traits. The root architecture (depth, profile, and root area to leaf area ratio) of juniper was adjusted to see how root morphology could affect the survival/mortality of its neighboring pine under both ambient and drought conditions. Drought suppressed plant water and carbon uptake, as well increased the average percentage loss of conductivity (PLC). Pine had 59% reduction in water uptake, 48% reduction in carbon uptake, and 38% increase in PLC, while juniper had 56% reduction in water uptake, 50% reduction in carbon and 29% increase in PLC, suggesting different vulnerability to drought as mediated by plant physiological traits. Variations in juniper root architecture further mediated drought stress on pine, from negative to positive. Different juniper root architecture caused variations in response of pine over drought (water uptake reduction ranged 0% ~63%, carbon uptake reduction ranged 0% ~ 70%, and PLC increase ranged 2% ~ 91%). Deeper or more uniformly distributed roots of juniper could effectively mitigate stress experienced by pine. In addition, the total water and carbon uptake tended to increase as the ratio of root area to leaf area increased while PLC showed non-monotonic response, suggesting the potential trade-off between maximizing resource uptake and susceptibility to cavitation. The results showed that co-occurring species' morphological traits could alleviate or aggravate stress imposed by drought and should therefore be considered together with plant physiological traits in predicting plant mortality and ecosystem structural shift under future climate conditions.

Numerical investigation on effect of aortic root geometry on flow induced structural stresses developed in a bileaflet mechanical heart valve

NASA Astrophysics Data System (ADS)

Abbas, S. S.; Nasif, M. S.; Said, M. A. M.; Kadhim, S. K.

2017-10-01

Structural stresses developed in an artificial bileaflet mechanical heart valve (BMHV) due to pulsed blood flow may cause valve failure due to yielding. In this paper, von-Mises stresses are computed and compared for BMHV placed in two types of aortic root geometries that are aortic root with axisymmetric sinuses and with axisymmetric bulb, at different physiological blood flow rates. With BMHV placed in an aortic root with axisymmetric sinuses, the von-Mises stresses developed in the valve were found to be up to 47% higher than BMHV placed in aortic root with axisymmetric bulb under similar physiological conditions. High velocity vectors and therefore high von-Mises stresses have been observed for BMHV placed in aortic root with axisymmetric sinuses, that can lead to valve failure.

Environmental and physiological effects on grouping of drought-tolerant and susceptible rice varieties related to rice (Oryza sativa) root hydraulics under drought

PubMed Central

Henry, Amelia; Wehler, Regina; Grondin, Alexandre; Franke, Rochus; Quintana, Marinell

2016-01-01

Background and Aims Root hydraulic limitations (i.e. intra-plant restrictions to water movement) may be related to crop performance under drought, and groupings in the hydraulic function of drought-tolerant and drought-susceptible rice (Oryza sativa) varieties have been previously reported. This study aimed to better understand the environmental and physiological relationships with rice root hydraulics under drought. Methods Xylem sap bleeding rates in the field (gsap g–1 shoot) were measured on seasonal and diurnal time frames, during which time environmental conditions were monitored and physiological measurements were conducted. Complementary experiments on the effects of vapour pressure deficit (VPD) on root hydraulic conductivity and on transpiration rates of de-rooted tillers were conducted in growth chambers. Key Results The diurnal effects on bleeding rate were more closely related to irradiance than VPD, and VPD effects on root hydraulic conductivity measured on 21-day-old plants were due to effects on plant growth including root surface area, maximum root depth and root:shoot ratio. Leaf osmotic potential was related to the grouping of drought-tolerant and drought-susceptible varieties in rice root hydraulics, and these groupings were independent of differences in phenology. Low single-tiller bleeding rates were observed under high evapo-transpirational demand, higher bleeding rates were observed at more negative leaf osmotic potentials in drought-susceptible varieties, and drought-tolerant and susceptible varieties differed in the VPD-induced increase in transpiration rates of de-rooted tillers. Low root suberin amounts in some of the drought-susceptible varieties may have resulted in higher ion transport, as evidenced by higher sap K+ concentration and higher bleeding rates in those varieties. Conclusions These results provide evidence of the environmental effects on shoots that can influence root hydraulics. The consistent groupings of drought-tolerant and susceptible varieties suggest that traits affecting plant osmotic status may regulate root hydraulic response to drought in rice. PMID:27192712

Root growth and physiology of potted and field-grown trembling aspen exposed to tropospheric ozone

Treesearch

M.D. Coleman; R.E. Dickson; J.G. Isebrands; D.F. Karnosky

1996-01-01

We studied root growth and respiration of potted plants and field-grown aspen trees (Populus tremuloides Michx.) exposed to ambient or twice-ambient ozone. Root dry weight of potted plants decreased up to 45% after 12 weeks of ozone treatment, and root system respiration decreased by 27%. The ozone-induced decrease in root system respiration of...

Transient physiological responses of planting frozen root plugs of Douglas-fir seedlings

Treesearch

M. Anisul Islam; Douglass F. JAcobs; Kent G. Apostol; R. Kasten Dumroese

2008-01-01

Short-term physiological responses of planting frozen (FR) and rapidly thawed (TR) root plugs of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings were examined through time series (0 h, 6 h, 12 h, 1 day, 3 days, and 7 days) measurements in two separate experiments: 10 C day: 6 C night, RH 75% and 30 C day: 20 C night, RH 50%, respectively...

MADS-box transcription factor AGL21 regulates lateral root development and responds to multiple external and physiological signals.

PubMed

Yu, Lin-Hui; Miao, Zi-Qing; Qi, Guo-Feng; Wu, Jie; Cai, Xiao-Teng; Mao, Jie-Li; Xiang, Cheng-Bin

2014-11-01

Plant root system morphology is dramatically influenced by various environmental cues. The adaptation of root system architecture to environmental constraints, which mostly depends on the formation and growth of lateral roots, is an important agronomic trait. Lateral root development is regulated by the external signals coordinating closely with intrinsic signaling pathways. MADS-box transcription factors are known key regulators of the transition to flowering and flower development. However, their functions in root development are still poorly understood. Here we report that AGL21, an AGL17-clade MADS-box gene, plays a crucial role in lateral root development. AGL21 was highly expressed in root, particularly in the root central cylinder and lateral root primordia. AGL21 overexpression plants produced more and longer lateral roots while agl21 mutants showed impaired lateral root development, especially under nitrogen-deficient conditions. AGL21 was induced by many plant hormones and environmental stresses, suggesting a function of this gene in root system plasticity in response to various signals. Furthermore, AGL21 was found positively regulating auxin accumulation in lateral root primordia and lateral roots by enhancing local auxin biosynthesis, thus stimulating lateral root initiation and growth. We propose that AGL21 may be involved in various environmental and physiological signals-mediated lateral root development and growth. © The Author 2014. Published by Oxford University Press on behalf of CSPB and IPPE, SIBS, CAS.

IN SITU RT-PCR WITH A SULFATE-REDUCING BACTERIUM ISOLATED FROM SEAGRASS ROOTS

EPA Science Inventory

Bacteria considered to be obligate anaerobes internally colonize roots of the submerged macrophyte Halodule wrightii. A sulfate reducing bacterium, Summer lac 1, was isolated on lactate from H. wrightii roots. The isolate has physiological characteristics typical of Desulfovibri...

Root based responses account for Psidium guajava survival at high nickel concentration.

PubMed

Bazihizina, Nadia; Redwan, Mirvat; Taiti, Cosimo; Giordano, Cristiana; Monetti, Emanuela; Masi, Elisa; Azzarello, Elisa; Mancuso, Stefano

2015-02-01

The presence of Psidium guajava in polluted environments has been reported in recent studies, suggesting that this species has a high tolerance to the metal stress. The present study aims at a physiological characterization of P. guajava response to high nickel (Ni) concentrations in the root-zone. Three hydroponic experiments were carried out to characterize the effects of toxic Ni concentrations on morphological and physiological parameters of P. guajava, focusing on Ni-induced damages at the root-level and root ion fluxes. With up to 300μM NiSO4 in the root-zone, plant growth was similar to that in control plants, whereas at concentrations higher than 1000μM NiSO4 there was a progressive decline in plant growth and leaf gas exchange parameters; this occurred despite, at all considered concentrations, plants limited Ni(2+) translocation to the shoot, therefore avoiding shoot Ni(2+) toxicity symptoms. Maintenance of plant growth with 300μM Ni(2+) was associated with the ability to retain K(+) in the roots meanwhile 1000 and 3000μM NiSO4 led to substantial K(+) losses. In this study, root responses mirror all plant performances suggesting a direct link between root functionality and Ni(2+) tolerance mechanisms and plant survival. Considering that Ni was mainly accumulated in the root system, the potential use of P. guajava for Ni(2+) phytoextraction in metal-polluted soils is limited; nevertheless, the observed physiological changes indicate a good Ni(2+) tolerance up to 300μM NiSO4 suggesting a potential role for the phytostabilization of polluted soils. Copyright © 2014 Elsevier GmbH. All rights reserved.

Carbon allocation to root and shoot systems of woody plants

Treesearch

Mark D. Coleman; J.G. Isebrands

1994-01-01

Carbon allocation to roots is of widespread and increasing interest due to a growing appreciation of the importance of root processes to whole-plant physiology and plant productivity. Carbon (C) allocation commonly refers to the distribution of C among plant organs (e.g., leaves, stems, roots); however, the term also applies to functional categories within organs such...

Environmental and physiological effects on grouping of drought-tolerant and susceptible rice varieties related to rice (Oryza sativa) root hydraulics under drought.

PubMed

Henry, Amelia; Wehler, Regina; Grondin, Alexandre; Franke, Rochus; Quintana, Marinell

2016-05-02

Root hydraulic limitations (i.e. intra-plant restrictions to water movement) may be related to crop performance under drought, and groupings in the hydraulic function of drought-tolerant and drought-susceptible rice (Oryza sativa) varieties have been previously reported. This study aimed to better understand the environmental and physiological relationships with rice root hydraulics under drought. Xylem sap bleeding rates in the field (g sap g -1 shoot ) were measured on seasonal and diurnal time frames, during which time environmental conditions were monitored and physiological measurements were conducted. Complementary experiments on the effects of vapour pressure deficit (VPD) on root hydraulic conductivity and on transpiration rates of de-rooted tillers were conducted in growth chambers. The diurnal effects on bleeding rate were more closely related to irradiance than VPD, and VPD effects on root hydraulic conductivity measured on 21-day-old plants were due to effects on plant growth including root surface area, maximum root depth and root:shoot ratio. Leaf osmotic potential was related to the grouping of drought-tolerant and drought-susceptible varieties in rice root hydraulics, and these groupings were independent of differences in phenology. Low single-tiller bleeding rates were observed under high evapo-transpirational demand, higher bleeding rates were observed at more negative leaf osmotic potentials in drought-susceptible varieties, and drought-tolerant and susceptible varieties differed in the VPD-induced increase in transpiration rates of de-rooted tillers. Low root suberin amounts in some of the drought-susceptible varieties may have resulted in higher ion transport, as evidenced by higher sap K + concentration and higher bleeding rates in those varieties. These results provide evidence of the environmental effects on shoots that can influence root hydraulics. The consistent groupings of drought-tolerant and susceptible varieties suggest that traits affecting plant osmotic status may regulate root hydraulic response to drought in rice. © The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Enzymatic adaptations to arsenic-induced oxidative stress in Zea mays and genotoxic effect of arsenic in root tips of Vicia faba and Zea mays.

PubMed

Duquesnoy, Isabelle; Champeau, Gabrielle Marie; Evray, Germaine; Ledoigt, Gérard; Piquet-Pissaloux, Agnès

2010-01-01

Agronomic plant species may display physiological and biochemical responses to oxidative stress caused by heavy metals and metalloids. Zea mays plants were grown hydroponically for eight days at different concentrations of As (0, 134 and 668 μM) and at different pH (4, 7 and 9). Metabolic variations in response to As toxicity were measured using physiological parameters and antioxidant enzymatic activities. A significant decrease in SOD activity was observed in the leaves and roots of Z. mays with the majority of As treatments. As decreased G-POX activity less in leaves than in roots. An increase in the concentration of As increased APX activity in leaves and roots, except As(V) at pH 4 and pH 9 in the leaves and As(III) at pH 9 in the roots, when there was a significant decrease in APX activity at low As concentrations. After exposure to As(V), CAT activity was the same as in the control. As(III) led to an increase in CAT activity in leaves and to a decrease in roots. With increasing concentrations of As(III), CAT activity increased in both leaves and roots whatever the pH. To obtain more detailed knowledge on the effects of arsenate and arsenite exposure on Vicia faba and Z. mays, root meristems were also examined. Roots were fed hydroponically with 134, 334, 534 and 668 μM arsenate or arsenite and 4 × 10(-3)M of maleic hydrazide as positive control, at three different pH. Physiological parameters, the mitotic index and micronuclei frequencies were evaluated in root meristems. At all three pH, the highest As(V) and As(III) concentrations induced a substantial modification in root colour, increased root thickness with stiffening, and reduced root length. High concentrations also caused a significant decrease in the mitotic index, and micronucleus chromosomic aberrations were observed in the root meristems of both species. 2010 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Morphological and Biological alteration of maize root architectures on drought stress

USDA-ARS?s Scientific Manuscript database

Drought tolerance is a complex agronomic trait and root characteristics logically play an important role in determining the response of plants to drought stress. Studies were conducted to investigate genotypic variations in morphological and physiological responses of roots to drought stress in corn...

Morphological and biological alteration of maize root architectures on drought stress

USDA-ARS?s Scientific Manuscript database

Drought tolerance is a complex agronomic trait and root characteristics logically play an important role in determining the response of plants to drought stress. Studies were conducted to investigate genotypic variations in morphological and physiological responses of roots to drought stress in corn...

Morphological and Physiological Factors Affecting Formation of Adventitious Roots on Sugar Maple Stem Cuttings

Treesearch

John R. Donnelly

1977-01-01

Sugar maple cuttings were collected twice a week throughout June from four mature trees. Some of the cuttings were analyzed for carbohydrate (starch and sugars) and nitrogen content; the others were stuck in rooting beds. Rooting response showed significant daily and clonal variations. Cuttings rooted best when their terminal leaves were mature, as judged by size and...

A novel morphological response of maize (Zea mays) adult roots to heterogeneous nitrate supply revealed by a split-root experiment.

PubMed

Yu, Peng; Li, Xuexian; Yuan, Lixing; Li, Chunjian

2014-01-01

Approximately 35-55% of total nitrogen (N) in maize plants is taken up by the root at the reproductive stage. Little is known about how the root of an adult plant responds to heterogeneous nutrient supply. In this study, root morphological and physiological adaptations to nitrate-rich and nitrate-poor patches and corresponding gene expression of ZmNrt2.1 and ZmNrt2.2 of maize seedlings and adult plants were characterized. Local high nitrate (LoHN) supply increased both lateral root length (LRL) and density of the treated nodal roots of adult maize plants, but only increased LRL of the treated primary roots of seedlings. LoHN also increased plant total N acquisition but not N influx rate of the treated roots, when expressed as per unit of root length. Furthermore, LoHN markedly increased specific root length (m g(-1)) of the treated roots but significantly inhibited the growth of the lateral roots outside of the nitrate-rich patches, suggesting a systemic carbon saving strategy within a whole root system. Surprisingly, local low nitrate (LoLN) supply stimulated nodal root growth of adult plants although LoLN inhibited growth of primary roots of seedlings. LoLN inhibited the N influx rate of the treated roots and did not change plant total N content. The gene expression of ZmNrt2.1 and ZmNrt2.2 of the treated roots of seedlings and adult plants was inhibited by LoHN but enhanced by LoLN. In conclusion, maize adult roots responded to nitrate-rich and nitrate-poor patches by adaptive morphological alterations and displayed carbon saving strategies in response to heterogeneous nitrate supply. © 2013 Scandinavian Plant Physiology Society.

Root endophytic fungus Piriformospora indica affected growth, cadmium partitioning and chlorophyll fluorescence of sunflower under cadmium toxicity.

PubMed

Shahabivand, Saleh; Parvaneh, Azar; Aliloo, Ali Asghar

2017-11-01

Cadmium (Cd) pollution in the soil threatens the quality of environmental health, and deleteriously affects physiological activities of crops. Symbiosis of endophytic fungi with various plants is a promising manner to improving numerous plant characteristics and remediating heavy metal-polluted soils. In this pot experiment, the influence of root endophyte fungus Piriformospora indica on growth, physiological parameters and organs Cd accumulation in sunflower cv. Zaria plants under the toxic levels of Cd (0, 40, 80 and 120mg/kg soil) were studied. Increasing Cd concentration in the soil reduced growth parameters, chlorophyll (Chl) a and Chl b contents, and Fv/Fm and ETR (electron transport rate) values, but increased root, stem and leaf Cd accumulation, and proline content. The presence of P. indica significantly enhanced growth, Chl a, Chl b and proline contents, and Fv/Fm and ETR values. Compared to non-inoculated ones, P. indica-inoculated plants had higher Cd accumulation in root, whereas lower Cd accumulation in stem and leaf. The present study strongly supports the established ability of P. indica to alleviate Cd toxicity by improving the physiological status in sunflower. Furthermore, this endophyte fungus can be useful for Cd phyto-stabilization in sunflower roots in contaminated soils. Copyright © 2017 Elsevier Inc. All rights reserved.

Impact of treated wastewater on growth, respiration and hydraulic conductivity of citrus root systems in light and heavy soils.

PubMed

Paudel, Indira; Cohen, Shabtai; Shaviv, Avi; Bar-Tal, Asher; Bernstein, Nirit; Heuer, Bruria; Ephrath, Jhonathan

2016-06-01

Roots interact with soil properties and irrigation water quality leading to changes in root growth, structure and function. We studied these interactions in an orchard and in lysimeters with clay and sandy loam soils. Minirhizotron imaging and manual sampling showed that root growth was three times lower in the clay relative to sandy loam soil. Treated wastewater (TWW) led to a large reduction in root growth with clay (45-55%) but not with sandy loam soil (<20%). Treated wastewater increased salt uptake, membrane leakage and proline content, and decreased root viability, carbohydrate content and osmotic potentials in the fine roots, especially in clay. These results provide evidence that TWW challenges and damages the root system. The phenology and physiology of root orders were studied in lysimeters. Soil type influenced diameter, specific root area, tissue density and cortex area similarly in all root orders, while TWW influenced these only in clay soil. Respiration rates were similar in both soils, and root hydraulic conductivity was severely reduced in clay soil. Treated wastewater increased respiration rate and reduced hydraulic conductivity of all root orders in clay but only of the lower root orders in sandy loam soil. Loss of hydraulic conductivity increased with root order in clay and clay irrigated with TWW. Respiration and hydraulic properties of all root orders were significantly affected by sodium-amended TWW in sandy loam soil. These changes in root order morphology, anatomy, physiology and hydraulic properties indicate rapid and major modifications of root systems in response to differences in soil type and water quality. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Plant roots use a patterning mechanism to position lateral root branches toward available water.

PubMed

Bao, Yun; Aggarwal, Pooja; Robbins, Neil E; Sturrock, Craig J; Thompson, Mark C; Tan, Han Qi; Tham, Cliff; Duan, Lina; Rodriguez, Pedro L; Vernoux, Teva; Mooney, Sacha J; Bennett, Malcolm J; Dinneny, José R

2014-06-24

The architecture of the branched root system of plants is a major determinant of vigor. Water availability is known to impact root physiology and growth; however, the spatial scale at which this stimulus influences root architecture is poorly understood. Here we reveal that differences in the availability of water across the circumferential axis of the root create spatial cues that determine the position of lateral root branches. We show that roots of several plant species can distinguish between a wet surface and air environments and that this also impacts the patterning of root hairs, anthocyanins, and aerenchyma in a phenomenon we describe as hydropatterning. This environmental response is distinct from a touch response and requires available water to induce lateral roots along a contacted surface. X-ray microscale computed tomography and 3D reconstruction of soil-grown root systems demonstrate that such responses also occur under physiologically relevant conditions. Using early-stage lateral root markers, we show that hydropatterning acts before the initiation stage and likely determines the circumferential position at which lateral root founder cells are specified. Hydropatterning is independent of endogenous abscisic acid signaling, distinguishing it from a classic water-stress response. Higher water availability induces the biosynthesis and transport of the lateral root-inductive signal auxin through local regulation of tryptophan aminotransferase of Arabidopsis 1 and PIN-formed 3, both of which are necessary for normal hydropatterning. Our work suggests that water availability is sensed and interpreted at the suborgan level and locally patterns a wide variety of developmental processes in the root.

In vitro evaluation of physiological spiral anastomoses for the arterial switch operation in simple transposition of the great arteries: a first step towards a surgical alternative?

PubMed

Sievers, Hans-Hinrich; Scharfschwerdt, Michael; Putman, Léon M

2015-08-01

The currently most frequently used technique for the arterial switch operation (ASO) in simple transposition of the great arteries (TGA) includes the transposition of the pulmonary artery anterior to the ascending aorta. This arterial arrangement is less anatomical, and although the initial results are excellent, some long-term data are indicating a certain risk of morbidity, encouraging the search for more physiological techniques. As a first step, we studied the feasibility of anatomical spiral anastomoses of the great vessels in vitro. A TGA model was constructed to simulate the different spatial positions of the great arteries followed by ASO with physiological spiral connections of the great arteries. It was possible to perform a physiological spiral connection of the great arteries without tension or torsion when the roots of the great vessels were arranged anterior-posterior and with up to 35° rotation of the aortic root to the right around the pulmonary root. With further rotation of the aorta, patch plasties were required for pulmonary artery elongation. The maximal width of the patch was 5 mm. In this TGA model, it was possible to perform tension- and torsion-free arterial anastomoses for ASO without artificial material, when the aortic root was positioned from 0° up to 35° to the right of the pulmonary root. Evaluation of coronary transfer is the next step. © The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Intraspecific variation in fine root respiration and morphology in response to in situ soil nitrogen fertility in a 100-year-old Chamaecyparis obtusa forest.

PubMed

Makita, Naoki; Hirano, Yasuhiro; Sugimoto, Takanobu; Tanikawa, Toko; Ishii, Hiroaki

2015-12-01

Soil N fertility has an effect on belowground C allocation, but the physiological and morphological responses of individual fine root segments to variations in N availability under field conditions are still unclear. In this study, the direction and magnitude of the physiological and morphological function of fine roots in response to variable in situ soil N fertility in a forest site were determined. We measured the specific root respiration (Rr) rate, N concentration and morphology of fine root segments with 1-3 branching orders in a 100-year-old coniferous forest of Chamaecyparis obtusa. Higher soil N fertility induced higher Rr rates, root N concentration, and specific root length (SRL), and lower root tissue density (RTD). In all fertility levels, the Rr rates were significantly correlated positively with root N and SRL and negatively with RTD. The regression slopes of respiration with root N and RTD were significantly higher along the soil N fertility gradient. Although no differences in the slopes of Rr and SRL relationship were found across the levels, there were significant shifts in the intercept along the common slope. These results suggest that a contrasting pattern in intraspecific relationships between specific Rr and N, RTD, and SRL exists among soils with different N fertility. Consequently, substantial increases in soil N fertility would exert positive effects on organ-scale root performance by covarying the Rr, root N, and morphology for their potential nutrient and water uptake.

Teaching Materials and Methods.

ERIC Educational Resources Information Center

Physiologist, 1987

1987-01-01

Contains abstracts of presented papers which deal with teaching materials and methods in physiology. Includes papers on preconceptual notions in physiology, somatosensory activity recorded in the dorsal root ganglion of the bull frog, and the use of the Apple Macintosh microcomputer in teaching human anatomy and physiology. (TW)

Aortic root dynamics and surgery: from craft to science.

PubMed

Cheng, Allen; Dagum, Paul; Miller, D Craig

2007-08-29

Since the fifteenth century beginning with Leonardo da Vinci's studies, the precise structure and functional dynamics of the aortic root throughout the cardiac cycle continues to elude investigators. The last five decades of experimental work have contributed substantially to our current understanding of aortic root dynamics. In this article, we review and summarize the relevant structural analyses, using radiopaque markers and sonomicrometric crystals, concerning aortic root three-dimensional deformations and describe aortic root dynamics in detail throughout the cardiac cycle. We then compare data between different studies and discuss the mechanisms responsible for the modes of aortic root deformation, including the haemodynamics, anatomical and temporal determinants of those deformations. These modes of aortic root deformation are closely coupled to maximize ejection, optimize transvalvular ejection haemodynamics and-perhaps most importantly-reduce stress on the aortic valve cusps by optimal diastolic load sharing and minimizing transvalvular turbulence throughout the cardiac cycle. This more comprehensive understanding of aortic root mechanics and physiology will contribute to improved medical and surgical treatment methods, enhanced therapeutic decision making and better post-intervention care of patients. With a better understanding of aortic root physiology, future research on aortic valve repair and replacement should take into account the integrated structural and functional asymmetry of aortic root dynamics to minimize stress on the aortic cusps in order to prevent premature structural valve deterioration.

Water Uptake along the Length of Grapevine Fine Roots: Developmental anatomy, tissue specific aquaporin expression, and pathways of water transport

USDA-ARS?s Scientific Manuscript database

To better understand water uptake patterns in root systems of woody perennial crops, we detailed the developmental anatomy and hydraulic physiology along the length of grapevine fine roots- from the tip to secondary growth zones. Our characterization included localization of suberized structures an...

Effects of peach tree root system morphology and transpiration on leaf nitrogen and phosphorus

USDA-ARS?s Scientific Manuscript database

Adequate mineral nutrition is critical for high fruit quality and sustained yield of fruit trees. It is likely that nutritional competence of a fruit tree depends on several physiological and morphological traits that affect nutrient uptake. Fruit trees with improved root systems (own-rooted or as ...

Association of proteomics changes with Al-sensitive root zones in switchgrass

USDA-ARS?s Scientific Manuscript database

In this paper, we report on aluminum (Al)-induced root proteomic changes in switchgrass. After growth in a hydroponic culture system supplemented with 400 uM of Al, plants began to show signs of physiological stress such as a reduction in photosynthetic rate. At this time, the basal 2-cmlong root ti...

Complex physiological and molecular processes underlying root gravitropism

NASA Technical Reports Server (NTRS)

Chen, Rujin; Guan, Changhui; Boonsirichai, Kanokporn; Masson, Patrick H.

2002-01-01

Gravitropism allows plant organs to guide their growth in relation to the gravity vector. For most roots, this response to gravity allows downward growth into soil where water and nutrients are available for plant growth and development. The primary site for gravity sensing in roots includes the root cap and appears to involve the sedimentation of amyloplasts within the columella cells. This process triggers a signal transduction pathway that promotes both an acidification of the wall around the columella cells, an alkalinization of the columella cytoplasm, and the development of a lateral polarity across the root cap that allows for the establishment of a lateral auxin gradient. This gradient is then transmitted to the elongation zones where it triggers a differential cellular elongation on opposite flanks of the central elongation zone, responsible for part of the gravitropic curvature. Recent findings also suggest the involvement of a secondary site/mechanism of gravity sensing for gravitropism in roots, and the possibility that the early phases of graviresponse, which involve differential elongation on opposite flanks of the distal elongation zone, might be independent of this auxin gradient. This review discusses our current understanding of the molecular and physiological mechanisms underlying these various phases of the gravitropic response in roots.

ASTROCULTURE (TM) root metabolism and cytochemical analysis

NASA Technical Reports Server (NTRS)

Porterfield, D. M.; Barta, D. J.; Ming, D. W.; Morrow, R. C.; Musgrave, M. E.

2000-01-01

Physiology of the root system is dependent upon oxygen availability and tissue respiration. During hypoxia nutrient and water acquisition may be inhibited, thus affecting the overall biochemical and physiological status of the plant. For the Astroculture (TM) plant growth hardware, the availability of oxygen in the root zone was measured by examining the changes in alcohol dehydrogenase (ADH) activity within the root tissue. ADH activity is a sensitive biochemical indicator of hypoxic conditions in plants and was measured in both spaceflight and control roots. In addition to the biochemical enzyme assays, localization of ADH in the root tissue was examined cytochemically. The results of these analyses showed that ADH activity increased significantly as a result of spaceflight exposure. Enzyme activity increased 248% to 304% in dwarf wheat when compared with the ground controls and Brassica showed increases between 334% and 579% when compared with day zero controls. Cytochemical staining revealed no differences in ADH tissue localization in any of the dwarf wheat treatments. These results show the importance of considering root system oxygenation in designing and building nutrient delivery hardware for spaceflight plant cultivation and confirm previous reports of an ADH response associated with spaceflight exposure.

Constituents and secondary metabolite natural products in fresh and deteriorated cassava roots.

PubMed

Bayoumi, Soad A L; Rowan, Michael G; Beeching, John R; Blagbrough, Ian S

2010-04-01

A phytochemical analysis of cassava (Manihot esculenta Crantz) fresh roots and roots suffering from post-harvest physiological deterioration (PPD) has been carried out. The first isolation and identification of galactosyl diacylglycerides from fresh cassava roots is reported, as well as beta-carotene, linamarin, and beta-sitosterol glucopyranoside. The hydroxycoumarin scopoletin and its glucoside scopolin were identified from cassava roots during PPD, as well as trace quantities of esculetin and its glucoside esculin. There is no isoscopoletin in cassava roots during PPD. Copyright 2009 Elsevier Ltd. All rights reserved.

Effect of the fungus Piriformospora indica on physiological characteristics and root morphology of wheat under combined drought and mechanical stresses.

PubMed

Hosseini, Fatemeh; Mosaddeghi, Mohammad Reza; Dexter, Anthony Roger

2017-09-01

This study was done to evaluate the effects of the root-colonizing endophytic fungus Piriformospora indica on wheat growth under combined drought and mechanical stresses. Inoculated (colonized) and non-inoculated (uncolonized) wheat (Triticum aestivum L. cv. Chamran) seedlings were planted in growth chambers filled with moist sand (at a matric suction of 20 hPa). Slight, moderate and severe mechanical stresses (i.e., penetration resistance, Q p , of 1.17, 4.17 and 5.96 MPa, respectively) were produced by a dead-load technique (i.e., placing a weight on the sand surface) in the root medium. Slight, moderate and severe drought stresses were induced using PEG 6000 solutions with osmotic potentials of 0, -0.3 and -0.5 MPa, respectively. After 30 days, plant physiological characteristics and root morphology were measured. An increase in Q p from 1.17 to 5.96 MPa led to greater leaf proline concentration and root diameter, and lower relative water content (RWC), leaf water potential (LWP), chlorophyll contents and root volume. Moreover, severe drought stress decreased root and shoot fresh weights, root volume, leaf area, RWC, LWP and chlorophyll content compared to control. Catalase (CAT) and ascorbate peroxidase (APX) activities under severe drought stress were about 1.5 and 2.9 times greater than control. Interaction of the stresses showed that mechanical stress primarily controls plant water status and physiological responses. However, endophyte presence mitigated the adverse effects of individual and combined stresses on plant growth. Colonized plants were better adapted and had greater root length and volume, RWC, LWP and chlorophyll contents under stressful conditions due to higher absorption sites for water and nutrients. Compared with uncolonized plants, colonized plants showed lower CAT activity implying that wheat inoculated with P. indica was more tolerant and experienced less oxidative damage induced by drought and/or mechanical stress. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Measurement of inclusive jet cross sections in Z/gamma*(-->e+e-) + jets production in pp[over ] collisions at square root s = 1.96 TeV.

PubMed

Aaltonen, T; Adelman, J; Akimoto, T; Albrow, M G; Alvarez González, B; Amerio, S; Amidei, D; Anastassov, A; Annovi, A; Antos, J; Aoki, M; Apollinari, G; Apresyan, A; Arisawa, T; Artikov, A; Ashmanskas, W; Attal, A; Aurisano, A; Azfar, F; Azzi-Bacchetta, P; Azzurri, P; Bacchetta, N; Badgett, W; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Baroiant, S; Bartsch, V; Bauer, G; Beauchemin, P-H; Bedeschi, F; Bednar, P; Behari, S; Bellettini, G; Bellinger, J; Belloni, A; Benjamin, D; Beretvas, A; Beringer, J; Berry, T; Bhatti, A; Binkley, M; Bisello, D; Bizjak, I; Blair, R E; Blocker, C; Blumenfeld, B; Bocci, A; Bodek, A; Boisvert, V; Bolla, G; Bolshov, A; Bortoletto, D; Boudreau, J; Boveia, A; Brau, B; Bridgeman, A; Brigliadori, L; Bromberg, C; Brubaker, E; Budagov, J; Budd, H S; Budd, S; Burkett, K; Busetto, G; Bussey, P; Buzatu, A; Byrum, K L; Cabrera, S; Campanelli, M; Campbell, M; Canelli, F; Canepa, A; Carlsmith, D; Carosi, R; Carrillo, S; Carron, S; Casal, B; Casarsa, M; Castro, A; Catastini, P; Cauz, D; Cavalli-Sforza, M; Cerri, A; Cerrito, L; Chang, S H; Chen, Y C; Chertok, M; Chiarelli, G; Chlachidze, G; Chlebana, F; Cho, K; Chokheli, D; Chou, J P; Choudalakis, G; Chuang, S H; Chung, K; Chung, W H; Chung, Y S; Ciobanu, C I; Ciocci, M A; Clark, A; Clark, D; Compostella, G; Convery, M E; Conway, J; Cooper, B; Copic, K; Cordelli, M; Cortiana, G; Crescioli, F; Cuenca Almenar, C; Cuevas, J; Culbertson, R; Cully, J C; Dagenhart, D; Datta, M; Davies, T; de Barbaro, P; De Cecco, S; Deisher, A; De Lentdecker, G; De Lorenzo, G; Dell'orso, M; Demortier, L; Deng, J; Deninno, M; De Pedis, D; Derwent, P F; Di Giovanni, G P; Dionisi, C; Di Ruzza, B; Dittmann, J R; D'Onofrio, M; Donati, S; Dong, P; Donini, J; Dorigo, T; Dube, S; Efron, J; Erbacher, R; Errede, D; Errede, S; Eusebi, R; Fang, H C; Farrington, S; Fedorko, W T; Feild, R G; Feindt, M; Fernandez, J P; Ferrazza, C; Field, R; Flanagan, G; Forrest, R; Forrester, S; Franklin, M; Freeman, J C; Furic, I; Gallinaro, M; Galyardt, J; Garberson, F; Garcia, J E; Garfinkel, A F; Gerberich, H; Gerdes, D; Giagu, S; Giakoumopolou, V; Giannetti, P; Gibson, K; Gimmell, J L; Ginsburg, C M; Giokaris, N; Giordani, M; Giromini, P; Giunta, M; Glagolev, V; Glenzinski, D; Gold, M; Goldschmidt, N; Golossanov, A; Gomez, G; Gomez-Ceballos, G; Goncharov, M; González, O; Gorelov, I; Goshaw, A T; Goulianos, K; Gresele, A; Grinstein, S; Grosso-Pilcher, C; Grundler, U; Guimaraes da Costa, J; Gunay-Unalan, Z; Haber, C; Hahn, K; Hahn, S R; Halkiadakis, E; Hamilton, A; Han, B-Y; Han, J Y; Handler, R; Happacher, F; Hara, K; Hare, D; Hare, M; Harper, S; Harr, R F; Harris, R M; Hartz, M; Hatakeyama, K; Hauser, J; Hays, C; Heck, M; Heijboer, A; Heinemann, B; Heinrich, J; Henderson, C; Herndon, M; Heuser, J; Hewamanage, S; Hidas, D; Hill, C S; Hirschbuehl, D; Hocker, A; Hou, S; Houlden, M; Hsu, S-C; Huffman, B T; Hughes, R E; Husemann, U; Huston, J; Incandela, J; Introzzi, G; Iori, M; Ivanov, A; Iyutin, B; James, E; Jayatilaka, B; Jeans, D; Jeon, E J; Jindariani, S; Johnson, W; Jones, M; Joo, K K; Jun, S Y; Jung, J E; Junk, T R; Kamon, T; Kar, D; Karchin, P E; Kato, Y; Kephart, R; Kerzel, U; Khotilovich, V; Kilminster, B; Kim, D H; Kim, H S; Kim, J E; Kim, M J; Kim, S B; Kim, S H; Kim, Y K; Kimura, N; Kirsch, L; Klimenko, S; Klute, M; Knuteson, B; Ko, B R; Koay, S A; Kondo, K; Kong, D J; Konigsberg, J; Korytov, A; Kotwal, A V; Kraus, J; Kreps, M; Kroll, J; Krumnack, N; Kruse, M; Krutelyov, V; Kubo, T; Kuhlmann, S E; Kuhr, T; Kulkarni, N P; Kusakabe, Y; Kwang, S; Laasanen, A T; Lai, S; Lami, S; Lammel, S; Lancaster, M; Lander, R L; Lannon, K; Lath, A; Latino, G; Lazzizzera, I; Lecompte, T; Lee, J; Lee, J; Lee, Y J; Lee, S W; Lefèvre, R; Leonardo, N; Leone, S; Levy, S; Lewis, J D; Lin, C; Lin, C S; Linacre, J; Lindgren, M; Lipeles, E; Lister, A; Litvintsev, D O; Liu, T; Lockyer, N S; Loginov, A; Loreti, M; Lovas, L; Lu, R-S; Lucchesi, D; Lueck, J; Luci, C; Lujan, P; Lukens, P; Lungu, G; Lyons, L; Lys, J; Lysak, R; Lytken, E; Mack, P; Macqueen, D; Madrak, R; Maeshima, K; Makhoul, K; Maki, T; Maksimovic, P; Malde, S; Malik, S; Manca, G; Manousakis, A; Margaroli, F; Marino, C; Marino, C P; Martin, A; Martin, M; Martin, V; Martínez, M; Martínez-Ballarín, R; Maruyama, T; Mastrandrea, P; Masubuchi, T; Mattson, M E; Mazzanti, P; McFarland, K S; McIntyre, P; McNulty, R; Mehta, A; Mehtala, P; Menzemer, S; Menzione, A; Merkel, P; Mesropian, C; Messina, A; Miao, T; Miladinovic, N; Miles, J; Miller, R; Mills, C; Milnik, M; Mitra, A; Mitselmakher, G; Miyake, H; Moed, S; Moggi, N; Moon, C S; Moore, R; Morello, M; Movilla Fernandez, P; Mülmenstädt, J; Mukherjee, A; Muller, Th; Mumford, R; Murat, P; Mussini, M; Nachtman, J; Nagai, Y; Nagano, A; Naganoma, J; Nakamura, K; Nakano, I; Napier, A; Necula, V; Neu, C; Neubauer, M S; Nielsen, J; Nodulman, L; Norman, M; Norniella, O; Nurse, E; Oh, S H; Oh, Y D; Oksuzian, I; Okusawa, T; Oldeman, R; Orava, R; Osterberg, K; Pagan Griso, S; Pagliarone, C; Palencia, E; Papadimitriou, V; Papaikonomou, A; Paramonov, A A; Parks, B; Pashapour, S; Patrick, J; Pauletta, G; Paulini, M; Paus, C; Pellett, D E; Penzo, A; Phillips, T J; Piacentino, G; Piedra, J; Pinera, L; Pitts, K; Plager, C; Pondrom, L; Portell, X; Poukhov, O; Pounder, N; Prakoshyn, F; Pronko, A; Proudfoot, J; Ptohos, F; Punzi, G; Pursley, J; Rademacker, J; Rahaman, A; Ramakrishnan, V; Ranjan, N; Redondo, I; Reisert, B; Rekovic, V; Renton, P; Rescigno, M; Richter, S; Rimondi, F; Ristori, L; Robson, A; Rodrigo, T; Rogers, E; Rolli, S; Roser, R; Rossi, M; Rossin, R; Roy, P; Ruiz, A; Russ, J; Rusu, V; Saarikko, H; Safonov, A; Sakumoto, W K; Salamanna, G; Saltó, O; Santi, L; Sarkar, S; Sartori, L; Sato, K; Savoy-Navarro, A; Scheidle, T; Schlabach, P; Schmidt, E E; Schmidt, M A; Schmidt, M P; Schmitt, M; Schwarz, T; Scodellaro, L; Scott, A L; Scribano, A; Scuri, F; Sedov, A; Seidel, S; Seiya, Y; Semenov, A; Sexton-Kennedy, L; Sfyria, A; Shalhout, S Z; Shapiro, M D; Shears, T; Shepard, P F; Sherman, D; Shimojima, M; Shochet, M; Shon, Y; Shreyber, I; Sidoti, A; Sinervo, P; Sisakyan, A; Slaughter, A J; Slaunwhite, J; Sliwa, K; Smith, J R; Snider, F D; Snihur, R; Soderberg, M; Soha, A; Somalwar, S; Sorin, V; Spalding, J; Spinella, F; Spreitzer, T; Squillacioti, P; Stanitzki, M; St Denis, R; Stelzer, B; Stelzer-Chilton, O; Stentz, D; Strologas, J; Stuart, D; Suh, J S; Sukhanov, A; Sun, H; Suslov, I; Suzuki, T; Taffard, A; Takashima, R; Takeuchi, Y; Tanaka, R; Tecchio, M; Teng, P K; Terashi, K; Thom, J; Thompson, A S; Thompson, G A; Thomson, E; Tipton, P; Tiwari, V; Tkaczyk, S; Toback, D; Tokar, S; Tollefson, K; Tomura, T; Tonelli, D; Torre, S; Torretta, D; Tourneur, S; Trischuk, W; Tu, Y; Turini, N; Ukegawa, F; Uozumi, S; Vallecorsa, S; van Remortel, N; Varganov, A; Vataga, E; Vázquez, F; Velev, G; Vellidis, C; Veszpremi, V; Vidal, M; Vidal, R; Vila, I; Vilar, R; Vine, T; Vogel, M; Volobouev, I; Volpi, G; Würthwein, F; Wagner, P; Wagner, R G; Wagner, R L; Wagner-Kuhr, J; Wagner, W; Wakisaka, T; Wallny, R; Wang, S M; Warburton, A; Waters, D; Weinberger, M; Wester, W C; Whitehouse, B; Whiteson, D; Wicklund, A B; Wicklund, E; Williams, G; Williams, H H; Wilson, P; Winer, B L; Wittich, P; Wolbers, S; Wolfe, C; Wright, T; Wu, X; Wynne, S M; Yagil, A; Yamamoto, K; Yamaoka, J; Yamashita, T; Yang, C; Yang, U K; Yang, Y C; Yao, W M; Yeh, G P; Yoh, J; Yorita, K; Yoshida, T; Yu, G B; Yu, I; Yu, S S; Yun, J C; Zanello, L; Zanetti, A; Zaw, I; Zhang, X; Zheng, Y; Zucchelli, S

2008-03-14

Inclusive jet cross sections in Z/gamma* events, with Z/gamma* decaying into an electron-positron pair, are measured as a function of jet transverse momentum and jet multiplicity in pp[over ] collisions at square root s = 1.96 TeV with the upgraded Collider Detector at Fermilab in run II, based on an integrated luminosity of 1.7 fb(-1). The measurements cover the rapidity region |y(jet)|<2.1 and the transverse momentum range p(T)(jet)>30 GeV/c. Next-to-leading order perturbative QCD predictions are in good agreement with the measured cross sections.

The relationship between root hydraulics and scion vigour across Vitis rootstocks: what role do root aquaporins play?

PubMed Central

McElrone, A. J.

2012-01-01

Vitis vinifera scions are commonly grafted onto rootstocks of other grape species to influence scion vigour and provide resistance to soil-borne pests and abiotic stress; however, the mechanisms by which rootstocks affect scion physiology remain unknown. This study characterized the hydraulic physiology of Vitis rootstocks that vary in vigour classification by investigating aquaporin (VvPIP) gene expression, fine-root hydraulic conductivity (Lp r), % aquaporin contribution to Lp r, scion transpiration, and the size of root systems. Expression of several VvPIP genes was consistently greater in higher-vigour rootstocks under favourable growing conditions in a variety of media and in root tips compared to mature fine roots. Similar to VvPIP expression patterns, fine-root Lp r and % aquaporin contribution to Lp r determined under both osmotic (Lp r Osm) and hydrostatic (Lp r Hyd) pressure gradients were consistently greater in high-vigour rootstocks. Interestingly, the % aquaporin contribution was nearly identical for Lp r Osm and Lp r Hyd even though a hydrostatic gradient would induce a predominant flow across the apoplastic pathway. In common scion greenhouse experiments, leaf area-specific transpiration (E) and total leaf area increased with rootstock vigour and were positively correlated with fine-root Lp r. These results suggest that increased canopy water demands for scion grafted onto high-vigour rootstocks are matched by adjustments in root-system hydraulic conductivity through the combination of fine-root Lp r and increased root surface area. PMID:23136166

Effect of Naphthalene Acetic Acid on Adventitious Root Development and Associated Physiological Changes in Stem Cutting of Hemarthria compressa

PubMed Central

Zhang, Xin-Quan; Yang, Wen-Yu; Wan, Yan; Ma, Ying-Mei; Zhu, Yong-Qun; Peng, Yan; Huang, Lin-Kai

2014-01-01

In order to find a way to induce rooting on cuttings of Hemarthria compressa cv. Ya’an under controlled conditions, a project was carried out to study the effect of naphthalene acetic acid (NAA) on rooting in stem cuttings and related physiological changes during the rooting process of Hemarthria compressa. The cuttings were treated with five concentrations of NAA (0, 100, 200 300, 400 mg/l) at three soaking durations (10, 20, 30 minutes), and cuttings without treatment were considered as control. Samples were planted immediately into pots after treatment. IAA-oxidase (IAAO) activity, peroxidase (POD) activity and polyphenol oxidase (PPO) activity were determined after planting. Results showed that NAA had positive effect on rooting at the concentration of 200 mg/l compared to other concentrations at 30 days after planting (DAP). Among the three soaking durations, 20 minutes (min) of 200 mg/l NAA resulted in higher percentages of rooting, larger numbers of adventitious roots and heavier root dry weight per cutting. The lowest IAAO activity was obtained when soaked at 200 mg/l NAA for 20 min soaking duration. This was consistent with the best rooting ability, indicating that the lower IAAO activity, the higher POD activity and PPO activity could be used as an indicator of better rooting ability for whip grass cuttings and might serve as a good marker for rooting ability in cuttings. PMID:24595064

Physiological and Comparative Proteomic Analysis Reveals Different Drought Responses in Roots and Leaves of Drought-Tolerant Wild Wheat (Triticum boeoticum)

PubMed Central

Liu, Hui; Sultan, Muhammad Abdul Rab Faisal; Liu, Xiang li; Zhang, Jin; Yu, Fei; Zhao, Hui xian

2015-01-01

To determine the proteomic-level responses of drought tolerant wild wheat (Triticum boeoticum), physiological and comparative proteomic analyses were conducted using the roots and the leaves of control and short term drought-stressed plants. Drought stress was imposed by transferring hydroponically grown seedlings at the 3-leaf stage into 1/2 Hoagland solution containing 20% PEG-6000 for 48 h. Root and leaf samples were separately collected at 0 (control), 24, and 48 h of drought treatment for analysis. Physiological analysis indicated that abscisic acid (ABA) level was greatly increased in the drought-treated plants, but the increase was greater and more rapid in the leaves than in the roots. The net photosynthetic rate of the wild wheat leaves was significantly decreased under short-term drought stress. The deleterious effects of drought on the studied traits mainly targeted photosynthesis. Comparative proteomic analysis identified 98 and 85 differently changed protein spots (DEPs) (corresponding to 87 and 80 unique proteins, respectively) in the leaves and the roots, respectively, with only 6 mutual unique proteins in the both organs. An impressive 86% of the DEPs were implicated in detoxification and defense, carbon metabolism, amino acid and nitrogen metabolism, proteins metabolism, chaperones, transcription and translation, photosynthesis, nucleotide metabolism, and signal transduction. Further analysis revealed some mutual and tissue-specific responses to short-term drought in the leaves and the roots. The differences of drought-response between the roots and the leaves mainly included that signal sensing and transduction-associated proteins were greatly up-regulated in the roots. Photosynthesis and carbon fixation ability were decreased in the leaves. Glycolysis was down-regulated but PPP pathway enhanced in the roots, resulting in occurrence of complex changes in energy metabolism and establishment of a new homeostasis. Protein metabolism was down-regulated in the roots, but enhanced in the leaves. These results will contribute to the existing knowledge on the complexity of root and leaf protein changes that occur in response to drought, and also provide a framework for further functional studies on the identified proteins. PMID:25859656

Changes in very fine root respiration and morphology with time since last fire in a boreal forest

NASA Astrophysics Data System (ADS)

Makita, Naoki; Pumpanen, Jukka; Köster, Kajar; Berninger, Frank

2016-04-01

We examined the physiological and morphological responses of individual fine root segments in boreal forests stands with different age since the last fire to determine changes in specific fine root respiration and morphological traits during forest succession. We investigated the respiration of fine roots divided into three diameter classes (<0.5, 0.5-1.0, and 1.0-2.0 mm) in a Finnish boreal Pinus sylvestris L. in forest stands with 5, 45, 63, and 155 years since the last fire. Specific respiration rates of <0.5 mm roots in 155-year-old stands were 74%, 38%, and 31% higher than in 5-, 45-, and 63-year-old stands, respectively. However, the respiration rates of thicker diameter roots did not significantly change among stands with respect to time after fire. Similarly, fire disturbance had a strong impact on morphological traits of <0.5 mm roots, but not on thicker roots. Root respiration rates correlated positively with specific root length (length per unit mass) and negatively with root tissue density (mass per unit volume) in all stand ages. The linear regression lines fitted to the relationships between root respiration and specific root length or root tissue density showed significantly higher intercepts in 63- and 155-year-old than in 5-year-old stands. Significant shifts in the intercept of the common slope of respiration vs. morphology indicate the different magnitude of the changes in physiological performance among the fire age class. Despite a specific small geographic area, we suggest that the recovery of boreal forests following wildfire induces a strategy that favors carbon investment in nutrient and water exploitation efficiency with consequences for higher respiration, length, and lower tissue density of very fine roots.

Interactions Between Pinus taeda (loblolly) Fine Roots and Soil Fungi: Impacts of Elevated CO2, N Availability, and Spatial Distribution of Fungi on Fine Root Persistence and Turnover

NASA Astrophysics Data System (ADS)

Strand, A.; Beidler, K.; McGlinn, D.; Pritchard, S. G.

2016-12-01

Fine root turnover represents the most significant mode of flux from plants into soil C pools. Unfortunately fine root senescence and decomposition, processes critical in turnover, are particularly understudied. For example, little is known about either the factors that influence fine-root decomposition or the fate of compounds they contain during root death. Better understanding fine root senescence and decomposition should reduce uncertainty associated with global climate models; including re-uptake of materials in dying leaves into these models has already been shown to increase their accuracy. Over 4400 individual fine-roots and 4734 rhizomorphs were tracked from initiation until disintegration over 12 years using minirhizotrons at the Duke FACE site. Image-based approaches such as minirhizotrons cannot directly assess fine-root physiological status. To assess fine-root function directly, we are now conducting manipulative experiments in P. taeda in which fine-root senescence is induced through two treatments, steam- and direct hand-girdling. Physiological status is then assessed by examining gene-expression, root anatomy and chemical composition of manipulated roots. Changing [CO2] did not change persistence times for roots, but did impact rhizomorph persistence. Both roots and rhizomorphs showed interactions between effects of N and CO2 on persistence. Most interesting is the interaction between fine-roots and rhizomorphs: fine root persistence times are reduced in the presence of rhizomorphs, but this effect depends on the amount of N available. Finally, we found experimentally inducing senescence via steam girdling to be very effective relative to hand-girdling. These results provide evidence of the importance of priming on function of soil fungi and the role of N availability on fine-root turnover. The ability to stimulate fine-root senescence provides a powerful experimental tool to examine the fates of resources contained in fine-root pools as these roots turn over.

The habits of roots: what's up down under?

NASA Technical Reports Server (NTRS)

Feldman, L. J.

1988-01-01

Defining interactions of roots with the surrounding soil environment has been the focus of many recent investigations. As a result of these efforts, we are gaining an appreciation of the varied and often surprising strategies whereby roots adjust to and condition their soil environment for optimal growth and development. This article summarizes current knowledge of the often complex interactions between roots and biotic and abiotic factors within the soil. These interactions are interpreted in terms of modifications in the development or the physiology of the root.

Root features related to plant growth and nutrient removal of 35 wetland plants.

PubMed

Lai, Wen-Ling; Wang, Shu-Qiang; Peng, Chang-Lian; Chen, Zhang-He

2011-07-01

Morphological, structural, and eco-physiological features of roots, nutrient removal, and correlation between the indices were comparatively studied for 35 emergent wetland plants in small-scale wetlands for further investigation into the hypothesis of two types of wetland plant roots (Chen et al., 2004). Significant differences in root morphological, structural, and eco-physiological features were found among the 35 species. They were divided into two types: fibrous-root plants and thick-root plants. The fibrous-root plants had most or all roots of diameter (D) ≤ 1 mm. Roots of D > 1 mm also had many fine and long lateral roots of D ≤ 1 mm. The roots of these plants were long and had a thin epidermis and a low degree of lignification. The roots of the thick-root plants were almost all thicker than 1 mm, and generally had no further fine lateral roots. The roots were short, smooth, and fleshy, and had a thick epidermis. Root porosity of the fibrous-root plants was higher than that of the thick-root plants (p = 0.001). The aerenchyma of the fibrous-root plants was composed of large cavities which were formed from many small cavities, and distributed radially between the exodermis and vascular tissues. The aerenchyma of the thick-root plants had a large number of small cavities which were distributed in the mediopellis. The fibrous-root plants had a significantly larger root biomass of D ≤ 1 mm, of 1 mm < D < 3 mm, above-ground biomass, total biomass, and longer root system, but shorter root longevity than those of the thick-root plants (p = 0.003, 0.018, 0.020, 0.032, 0.042, 0.001). The fibrous-root plants also had significantly higher radial oxygen loss (ROL), root activity, photosynthetic rate, transpiration rate, and removal rates of total nitrogen and total phosphorus than the thick-root plants (p = 0.001, 0.008, 0.010, 0.004, 0.020, 0.002). The results indicate that significantly different root morphological and structural features existed among different wetland plants, and these features had a close relationship to nutrient removal capacity. Copyright © 2011 Elsevier Ltd. All rights reserved.

Distinct physiological and molecular responses in Arabidopsis thaliana exposed to aluminum oxide nanoparticles and ionic aluminum.

PubMed

Jin, Yujian; Fan, Xiaoji; Li, Xingxing; Zhang, Zhenyan; Sun, Liwei; Fu, Zhengwei; Lavoie, Michel; Pan, Xiangliang; Qian, Haifeng

2017-09-01

Nano-aluminium oxide (nAl 2 O 3 ) is one of the most widely used nanomaterials. However, nAl 2 O 3 toxicity mechanisms and potential beneficial effects on terrestrial plant physiology remain poorly understood. Such knowledge is essential for the development of robust nAl 2 O 3 risk assessment. In this study, we studied the influence of a 10-d exposure to a total selected concentration of 98 μM nAl 2 O 3 or to the equivalent molar concentration of ionic Al (AlCl 3 ) (196 μM) on the model plant Arabidopsis thaliana on the physiology (e.g., growth and photosynthesis, membrane damage) and the transcriptome using a high throughput state-of-the-art technology, RNA-seq. We found no evidence of nAl 2 O 3 toxicity on photosynthesis, growth and lipid peroxidation. Rather the nAl 2 O 3 treatment stimulated root weight and length by 48% and 39%, respectively as well as photosynthesis opening up the door to the use of nAl 2 O 3 in biotechnology and nano agriculture. Transcriptomic analyses indicate that the beneficial effect of nAl 2 O 3 was related to an increase in the transcription of several genes involved in root growth as well as in root nutrient uptake (e.g., up-regulation of the root hair-specific gene family and root development genes, POLARIS protein). By contrast, the ionic Al treatment decreased shoot and root weight of Arabidopsis thaliana by 57.01% and 45.15%, respectively. This toxic effect was coupled to a range of response at the gene transcription level including increase transcription of antioxidant-related genes and transcription of genes involved in plant defense response to pathogens. This work provides an integrated understanding at the molecular and physiological level of the effects of nAl 2 O 3 and ionic Al in Arabidopsis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Vegetative Propagation and the Genetic Improvement of North American Hardwoods

Treesearch

R. E. Farmer

1973-01-01

Progress and problems in vegetative propagation of important North American hardwoods are reviewed with emphasis on rooting cuttings and the application of propagation techniques in breeding research. Some problems in rooting physiology are discussed.

Can differences in root responses to soil drying and compaction explain differences in performance of trees growing on landfill sites?

PubMed

Liang, Jiansheng; Zhang, Jianhua; Chan, Gilbert Y. S.; Wong, M. H.

1999-07-01

Two tropical woody species, Acacia confusa Merrill and Litsea glutinosa (Lour.) C.B. Robinson, were grown under controlled conditions in PVC pipes filled with John Innes No. 2 soil. To investigate root distribution, physiological characteristics and hydraulic conductivity, four soil treatments were imposed-well-watered and noncompacted (control), well-watered and compacted; unwatered and noncompacted, and unwatered and compacted. In L. glutinosa, rooting depth and root elongation were severely restricted when soil bulk density increased from around 1.12 to 1.62 g cm(-3), whereas soil compaction had little effect on these parameters in A. confusa. As soil drying progressed, root water potential and osmotic potential declined more slowly in L. glutinosa than in A. confusa. Both the soil drying and compaction treatments significantly stimulated the accumulation of root abscisic acid (ABA) in both species. Soil drying damaged the root cell membrane of A. confusa, but had little influence on the root cell membrane of L. glutinosa. Soil drying had a greater effect on root hydraulic conductivity (L(p)) in L. glutinosa than in A. confusa, whereas the effect of soil compaction on L(p) was less in L. glutinosa than in A. confusa. Soil drying enhanced the effects of soil compaction on root L(p). We conclude that soil drying and compaction have large species-specific effects on the distribution, growth and physiology of roots. The relationships of these root properties to the species' ability to tolerate unfavorable soil conditions were examined.

Impact of lead tolerant plant growth promoting rhizobacteria on growth, physiology, antioxidant activities, yield and lead content in sunflower in lead contaminated soil.

PubMed

Saleem, Muhammad; Asghar, Hafiz Naeem; Zahir, Zahir Ahmad; Shahid, Muhammad

2018-03-01

Present study was conducted to evaluate the effect of lead tolerant plant growth promoting rhizobacteria (LTPGPR) on growth, physiology, yield, antioxidant activities and lead uptake in sunflower in soil contaminated with lead under pot conditions. Three pre-characterized LTPGP strains (S2 (Pseudomonas gessardii strain BLP141), S5 (Pseudomonas fluorescens A506) and S10 (Pseudomonas fluorescens strain LMG 2189)) were used to inoculate sunflower growing in soil contaminated with different levels (300, 600 and 900 mg kg -1 ) of lead by using lead nitrate salt as source of lead. Treatments were arranged according to completely randomized design with factorial arrangements. At harvesting, data regarding growth attributes (root shoot length, root shoot fresh and dry weights), yield per plant, physiological attributes (Chlorophyll 'a', 'b' and carotenoids content), antioxidant activities (Ascorbate peroxidase, catalase, superoxide dismutase and glutathione reductase), proline and malanodialdehyde content, and lead content in root, shoot and achenes of sunflower were recorded. Data were analysed by standard statistical procedures. Results showed that lead contamination reduced the plants growth, physiology and yield at all levels of lead stress. But application of LTPGPR in soil contaminated with lead improved plant growth, physiology, yield, and antioxidant activities, proline, and reduced the malanodialdehyde content (that is reduced by the application of different strains in lead contamination) of sunflower as compared to plants grown in soil without inoculation. Inoculation also promoted the uptake of lead in root, shoots and reduced the uptake of lead in achenes of plants as compared to plants in lead contamination without inoculation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Plant responses to heterogeneous salinity: growth of the halophyte Atriplex nummularia is determined by the root-weighted mean salinity of the root zone

PubMed Central

Bazihizina, Nadia

2012-01-01

Soil salinity is generally spatially heterogeneous, but our understanding of halophyte physiology under such conditions is limited. The growth and physiology of the dicotyledonous halophyte Atriplex nummularia was evaluated in split-root experiments to test whether growth is determined by: (i) the lowest; (ii) the highest; or (iii) the mean salinity of the root zone. In two experiments, plants were grown with uniform salinities or horizontally heterogeneous salinities (10–450mM NaCl in the low-salt side and 670mM in the high-salt side, or 10mM NaCl in the low-salt side and 500–1500mM in the high-salt side). The combined data showed that growth and gas exchange parameters responded most closely to the root-weighted mean salinity rather than to the lowest, mean, or highest salinity in the root zone. In contrast, midday shoot water potentials were determined by the lowest salinity in the root zone, consistent with most water being taken from the least negative water potential source. With uniform salinity, maximum shoot growth was at 120–230mM NaCl; ~90% of maximum growth occurred at 10mM and 450mM NaCl. Exposure of part of the roots to 1500mM NaCl resulted in an enhanced (+40%) root growth on the low-salt side, which lowered root-weighted mean salinity and enabled the maintenance of shoot growth. Atriplex nummularia grew even with extreme salinity in part of the roots, as long as the root-weighted mean salinity of the root zone was within the 10–450mM range. PMID:23125356

Plant responses to heterogeneous salinity: growth of the halophyte Atriplex nummularia is determined by the root-weighted mean salinity of the root zone.

PubMed

Bazihizina, Nadia; Barrett-Lennard, Edward G; Colmer, Timothy D

2012-11-01

Soil salinity is generally spatially heterogeneous, but our understanding of halophyte physiology under such conditions is limited. The growth and physiology of the dicotyledonous halophyte Atriplex nummularia was evaluated in split-root experiments to test whether growth is determined by: (i) the lowest; (ii) the highest; or (iii) the mean salinity of the root zone. In two experiments, plants were grown with uniform salinities or horizontally heterogeneous salinities (10-450 mM NaCl in the low-salt side and 670 mM in the high-salt side, or 10 mM NaCl in the low-salt side and 500-1500 mM in the high-salt side). The combined data showed that growth and gas exchange parameters responded most closely to the root-weighted mean salinity rather than to the lowest, mean, or highest salinity in the root zone. In contrast, midday shoot water potentials were determined by the lowest salinity in the root zone, consistent with most water being taken from the least negative water potential source. With uniform salinity, maximum shoot growth was at 120-230 mM NaCl; ~90% of maximum growth occurred at 10 mM and 450 mM NaCl. Exposure of part of the roots to 1500 mM NaCl resulted in an enhanced (+40%) root growth on the low-salt side, which lowered root-weighted mean salinity and enabled the maintenance of shoot growth. Atriplex nummularia grew even with extreme salinity in part of the roots, as long as the root-weighted mean salinity of the root zone was within the 10-450 mM range.

Application of paclobutrazol affect maize grain yield by regulating root morphological and physiological characteristics under a semi-arid region.

PubMed

Kamran, Muhammad; Wennan, Su; Ahmad, Irshad; Xiangping, Meng; Wenwen, Cui; Xudong, Zhang; Siwei, Mou; Khan, Aaqil; Qingfang, Han; Tiening, Liu

2018-03-19

A field experiment was conducted to investigate the effects of paclobutrazol on ear characteristics and grain yield by regulating root growth and root-bleeding sap of maize crop. Seed-soaking at rate of 0 (CK1), 200 (S1), 300 (S2), and 400 (S3) mg L -1 , and seed-dressing at rate of 0 (CK2), 1.5 (D1), 2.5 (D2), and 3.5 (D3) g kg -1 were used. Our results showed that paclobutrazol improved the ear characteristics and grain yield, and were consistently higher than control during 2015-2016. The average grain yield of S1, S2 and S3 were 18.9%, 61.3%, and 45.9% higher, while for D1, D2 and D3 were 20.2%, 33.3%, and 45.2%, compared to CK, respectively. Moreover, paclobutrazol-treated maize had improved root-length density (RLD), root-surface area density (RSD) and root-weight density (RWD) at most of the soil profiles (0-70 cm for seed-soaking, 0-60 cm for seed-dressing) and was attributed to enhancing the grain yield. In addition, root-activity, root-bleeding sap, root dry weight, diameter and root/shoot ratio increased by paclobutrazol, with highest values achieved in S2 and D3 treatments, across the whole growth stages in 2015-2016. Our results suggested that paclobutrazol could efficiently be used to enhance root-physiological and morphological characteristics, resulting in higher grain yield.

Functional genomics of root growth and development in Arabidopsis

PubMed Central

Iyer-Pascuzzi, Anjali; Simpson, June; Herrera-Estrella, Luis; Benfey, Philip N.

2009-01-01

Summary Roots are vital for the uptake of water and nutrients, and for anchorage in the soil. They are highly plastic, able to adapt developmentally and physiologically to changing environmental conditions. Understanding the molecular mechanisms behind this growth and development requires knowledge of root transcriptomics, proteomics and metabolomics. Genomics approaches, including the recent publication of a root expression map, root proteome, and environment-specific root expression studies, are uncovering complex transcriptional and post-transcriptional networks underlying root development. The challenge is in further capitalizing on the information in these datasets to understand the fundamental principles of root growth and development. In this review, we highlight progress researchers have made toward this goal. PMID:19117793

Functional genomics of root growth and development in Arabidopsis.

PubMed

Iyer-Pascuzzi, Anjali; Simpson, June; Herrera-Estrella, Luis; Benfey, Philip N

2009-04-01

Roots are vital for the uptake of water and nutrients, and for anchorage in the soil. They are highly plastic, able to adapt developmentally and physiologically to changing environmental conditions. Understanding the molecular mechanisms behind this growth and development requires knowledge of root transcriptomics, proteomics, and metabolomics. Genomics approaches, including the recent publication of a root expression map, root proteome, and environment-specific root expression studies, are uncovering complex transcriptional and post-transcriptional networks underlying root development. The challenge is in further capitalizing on the information in these datasets to understand the fundamental principles of root growth and development. In this review, we highlight progress researchers have made toward this goal.

Early physiological flood tolerance is followed by slow post-flooding root recovery in the dryland riparian tree Eucalyptus camaldulensis subsp. refulgens.

PubMed

Argus, R E; Colmer, T D; Grierson, P F

2015-06-01

We investigated physiological and morphological responses to flooding and recovery in Eucalyptus camaldulensis subsp. refulgens, a riparian tree species from a dryland region prone to intense episodic floods. Seedlings in soil flooded for 88 d produced extensive adventitious roots, displayed stem hypertrophy (stem diameter increased by 93%) and increased root porosity owing to aerenchyma formation. Net photosynthesis (Pn) and stomatal conductance (gs) were maintained for at least 2 weeks of soil flooding, contrasting with previous studies of other subspecies of E. camaldulensis. Gradual declines followed in both gs (30% less than controls) and Pn (19% less). Total leaf soluble sugars did not differ between flooded and control plants. Root mass did not recover 32 d after flooding ceased, but gs was not lower than controls, suggesting the root system was able to functionally compensate. However, the limited root growth during recovery after flooding was surprising given the importance of extensive root systems in dryland environments. We conclude that early flood tolerance could be an adaptation to capitalize on scarce water resources in a water-limited environment. Overall, our findings highlight the need to assess flooding responses in relation to a species' fitness for particular flood regimes or ecological niches. © 2014 John Wiley & Sons Ltd.

Seasonal patterns of CO2 exchange in the shoot and root of loblolly pine seedlings

Treesearch

Allen P. Drew; F. Thomas Ledig

1981-01-01

Seedlings of six full-sib families of loblolly pine were grown outdoors in clay pots for two growing seasons. Dark respiration of shoot and root and CO2 exchange of the shoot in the light were measured periodically over a temperature range bracketing ambient conditions. Both shoot and root showed different physiological responses as seasonal...

Characterization of a calcium/calmodulin-dependent protein kinase homolog from maize roots showing light-regulated gravitropism

NASA Technical Reports Server (NTRS)

Lu, Y. T.; Hidaka, H.; Feldman, L. J.

1996-01-01

Roots of many species respond to gravity (gravitropism) and grow downward only if illuminated. This light-regulated root gravitropism is phytochrome-dependent, mediated by calcium, and inhibited by KN-93, a specific inhibitor of calcium/calmodulin-dependent protein kinase II (CaMK II). A cDNA encoding MCK1, a maize homolog of mammalian CaMK, has been isolated from roots of maize (Zea mays L.). The MCK1 gene is expressed in root tips, the site of perception for both light and gravity. Using the [35S]CaM gel-overlay assay we showed that calmodulin-binding activity of the MCK1 is abolished by 50 microM KN-93, but binding is not affected by 5 microM KN-93, paralleling physiological findings that light-regulated root gravitropism is inhibited by 50 microM KN-93, but not by 5 microM KN-93. KN-93 inhibits light-regulated gravitropism by interrupting transduction of the light signal, not light perception, suggesting that MCK1 may play a role in transducing light. This is the first report suggesting a physiological function for a CaMK homolog in light signal transduction.

Alterations of physiology and gene expression due to long-term magnesium-deficiency differ between leaves and roots of Citrus reticulata.

PubMed

Jin, Xiao-Lin; Ma, Cui-Lan; Yang, Lin-Tong; Chen, Li-Song

2016-07-01

Seedlings of Ponkan (Citrus reticulata) were irrigated with nutrient solution containing 0 (Mg-deficiency) or 1mM MgSO4 (control) every two day for 16 weeks. Thereafter, we examined magnesium (Mg)-deficiency-induced changes in leaf and root gas exchange, total soluble proteins and gene expression. Mg-deficiency lowered leaf CO2 assimilation, and increased leaf dark respiration. However, Mg-deficient roots had lower respiration. Total soluble protein level was not significantly altered by Mg-deficiency in roots, but was lower in Mg-deficient leaves than in controls. Using cDNA-AFLP, we obtained 70 and 71 differentially expressed genes from leaves and roots. These genes mainly functioned in signal transduction, stress response, carbohydrate and energy metabolism, cell transport, cell wall and cytoskeleton metabolism, nucleic acid, and protein metabolisms. Lipid metabolism (Ca(2+) signals)-related Mg-deficiency-responsive genes were isolated only from roots (leaves). Although little difference existed in the number of Mg-deficiency-responsive genes between them both, most of these genes only presented in Mg-deficient leaves or roots, and only four genes were shared by them both. Our data clearly demonstrated that Mg-deficiency-induced alterations of physiology and gene expression greatly differed between leaves and roots. In addition, we focused our discussion on the causes for photosynthetic decline in Mg-deficient leaves and the responses of roots to Mg-deficiency. Copyright © 2016 Elsevier GmbH. All rights reserved.

Corynebacterium glutamicum for Sustainable Bioproduction: From Metabolic Physiology to Systems Metabolic Engineering.

PubMed

Becker, Judith; Gießelmann, Gideon; Hoffmann, Sarah Lisa; Wittmann, Christoph

Since its discovery 60 years ago, Corynebacterium glutamicum has evolved into a workhorse for industrial biotechnology. Traditionally well known for its remarkable capacity to produce amino acids, this Gram-positive soil bacterium, has become a flexible, efficient production platform for various bulk and fine chemicals, materials, and biofuels. The central turnstile of all these achievements is our excellent understanding of its metabolism and physiology. This knowledge base, together with innovative systems metabolic engineering concepts, which integrate systems and synthetic biology into strain engineering, has upgraded C. glutamicum into one of the most successful industrial microorganisms in the world.

False Broomrape: A Physiological Disorder Caused by Growth-Regulator Imbalance 1

PubMed Central

Hamilton, James L.; Lowe, Richie H.; Skoog, Folke

1972-01-01

False broomrape on tobacco (Nicotiana tabacum) can be induced by applying cytokinins to the roots, by causing an increase in the cytokinin-auxin ratio in the roots, by removing the apical and auxillary buds, or by applying extracts from tobacco with false broomrape to the roots of healthy plants. It can be prevented by treating debudded plants with auxin. Images PMID:16658161

Bacterial physiological diversity in the rhizosphere of range plants in response to retorted shale stress. [Agropyron smithii Rydb; Atriplex canescens (Pursh) Nutt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metzger, W.C.; Klein, D.A.; Redente, E.F.

1986-10-01

Bacterial populations were isolated from the soil-root interface and root-free regions of Agropyron smithii Rydb. and Atriplex canescens (Pursh) Nutt. grown in soil, retorted shale, or soil over shale. Bacteria isolated from retorted shale exhibited a wider range of tolerance to alkalinity and salinity and decreased growth on amino acid substrates compared with bacteria from soil and soil-over-shale environments. Exoenzyme production was only slightly affected by growth medium treatment. Viable bacterial populations were higher in the rhizosphere and rhizoplane of plants grown in retorted shale than in plants grown in soil or soil over shale. In addition, a greater numbermore » of physiological groups of rhizosphere bacteria was observed in retorted shale, compared with soil alone. Two patterns of community similarity were observed in comparisons of bacteria from soil over shale with those from soil and retorted-shale environments. Root-associated populations from soil over shale had a higher proportion of physiological groups in common with those from the soil control than those from the retorted-shale treatment. However, in non-rhizosphere populations, bacterial groups from soil over shale more closely resembled the physiological groups from retorted shale.« less

Root growth and function of three Mojave Desert grasses in response to elevated atmospheric CO2 concentration

USGS Publications Warehouse

Yoder, C.K.; Vivin, P.; DeFalco, L.A.; Seemann, J.R.; Nowak, R.S.

2000-01-01

Root growth and physiological responses to elevated CO2 were investigated for three important Mojave Desert grasses: the C3 perennial Achnatherum hymenoides, the C4 perennial Pleuraphis rigida and the C3 annual Bromus madritensis ssp. rubens. Seeds of each species were grown at ambient (360 μl l−1) or elevated (1000 μl l−1) CO2 in a glasshouse and harvested at three phenological stages: vegetative, anthesis and seed fill. Because P. rigida did not flower during the course of this study, harvests for this species represent three vegetative stages. Primary productivity was increased in both C3 grasses in response to elevated CO2 (40 and 19% for A. hymenoides and B. rubens, respectively), but root biomass increased only in the C3 perennial grass. Neither above-ground nor below-ground biomass of the C4 perennial grass was significantly affected by the CO2 treatment. Elevated CO2 did not significantly affect root surface area for any species. Total plant nitrogen was also not statistically different between CO2treatments for any species, indicating no enhanced uptake of N under elevated CO2. Physiological uptake capacities for NO3 and NH4 were not affected by the CO2 treatment during the second harvest; measurements were not made for the first harvest. However, at the third harvest uptake capacity was significantly decreased in response to elevated CO2 for at least one N form in each species. NO3 uptake rates were lower in A. hymenoides and P. rigida, and NH4 uptake rates were lower in B. rubens at elevated CO2. Nitrogen uptake on a whole root-system basis (NO3+NH4uptake capacity × root biomass) was influenced positively by elevated CO2 only for A. hymenoidesafter anthesis. These results suggest that elevated CO2 may result in a competitive advantage forA. hymenoides relative to species that do not increase root-system N uptake capacity. Root respiration measurements normalized to 20 °C were not significantly affected by the CO2treatment. However, specific root respiration was significantly correlated with either root C∶N ratio or root water content when all data per species were included within a simple regression model. The results of this study provide little evidence for up-regulation of root physiology in response to elevated CO2 and indicate that root biomass responses to CO2 are species-specific.

Physiological and gene expression responses of sunflower (Helianthus annuus L.) plants differ according to irrigation placement.

PubMed

Aguado, Ana; Capote, Nieves; Romero, Fernando; Dodd, Ian C; Colmenero-Flores, José M

2014-10-01

To investigate effects of soil moisture heterogeneity on plant physiology and gene expression in roots and leaves, three treatments were implemented in sunflower plants growing with roots split between two compartments: a control (C) treatment supplying 100% of plant evapotranspiration, and two treatments receiving 50% of plant evapotranspiration, either evenly distributed to both compartments (deficit irrigation - DI) or unevenly distributed to ensure distinct wet and dry compartments (partial rootzone drying - PRD). Plants receiving the same amount of water responded differently under the two irrigation systems. After 3 days, evapotranspiration was similar in C and DI, but 20% less in PRD, concomitant with decreased leaf water potential (Ψleaf) and increased leaf xylem ABA concentration. Six water-stress responsive genes were highly induced in roots growing in the drying soil compartment of PRD plants, and their expression was best correlated with local soil water content. On the other hand, foliar gene expression differed significantly from that of the root and correlated better with xylem ABA concentration and Ψleaf. While the PRD irrigation strategy triggered stronger physiological and molecular responses, suggesting a more intense and systemic stress reaction due to local dehydration of the dry compartment of PRD plants, the DI strategy resulted in similar water savings without strongly inducing these responses. Correlating physiological and molecular responses in PRD/DI plants may provide insights into the severity and location of water deficits and may enable a better understanding of long-distance signalling mechanisms. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, M.; Caldwell, M.M.

Responses of leaf photosynthesis, root respiration and P uptake by Artemisia tridentata seedlings to study root physiological adjustments to utilize available nutrient resources in a changing soil environment. Root respiration was measured for intact root systems in split-root chambers. Increasing P in 0.2 [times] Hoagland's solution from 0.04 mmol to 2.0 mmol increased leaf photosynthesis by 6% in 3 days, increased nighttime leaf respiration rate by 8% and root respiration by 18%. After PPFD was reduced from 800 to 200 [mu]mol m[sup [minus]2]s[sup [minus]1] leaf photosynthesis deceased by 67%, and root respiration by 26% in the following day but thenmore » decreased by 35% over the next three days. Shading may limit root growth and nutrient uptake by lowering the carbohydrate supply to root systems.« less

Changes of Cyanide Content and Linamarase Activity in Wounded Cassava Roots 1

PubMed Central

Kojima, Mineo; Iwatsuki, Norio; Data, Emma S.; Villegas, Cynthia Dolores V.; Uritani, Ikuzo

1983-01-01

When cassava (Manihot esculenta Crantz) root was cut into blocks and incubated under laboratory conditions, the blocks showed more widespread and more even symptoms of physiological deterioration than those under natural conditions. Thus, the tissue block system has potential for biochemical studies of natural deterioration of cassava root. The changes in cyanide content and linamarase (linamarin β-d-glucoside glucohydrolase; EC 3.2.1.21) activity in various tissues during physiological deterioration were investigated. Total cyanide content increased in all parts of block tissue after 3-day incubation. The degree of increase in cyanide was most pronounced in white parenchymal tissue, 2 to 3 millimeters thick, next to the cortex (A-part tissue), where no physiological symptoms appeared. On the other hand, linamarase activity was decreased in all parts of block tissue after a 3-day incubation. A time course analysis of A-part tissue indicated a clear reciprocal relationship between changes in total cyanide and linamarase activity; total cyanide increased, while linamarase activity decreased. Free cyanide constituted a very small portion of the total cyanide and did not change markedly. Images Fig. 2 PMID:16662957

Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems

NASA Astrophysics Data System (ADS)

Weigand, Maximilian; Kemna, Andreas

2017-02-01

A better understanding of root-soil interactions and associated processes is essential in achieving progress in crop breeding and management, prompting the need for high-resolution and non-destructive characterization methods. To date, such methods are still lacking or restricted by technical constraints, in particular the charactization and monitoring of root growth and function in the field. A promising technique in this respect is electrical impedance tomography (EIT), which utilizes low-frequency (< 1 kHz)- electrical conduction- and polarization properties in an imaging framework. It is well established that cells and cell clusters exhibit an electrical polarization response in alternating electric-current fields due to electrical double layers which form at cell membranes. This double layer is directly related to the electrical surface properties of the membrane, which in turn are influenced by nutrient dynamics (fluxes and concentrations on both sides of the membranes). Therefore, it can be assumed that the electrical polarization properties of roots are inherently related to ion uptake and translocation processes in the root systems. We hereby propose broadband (mHz to hundreds of Hz) multi-frequency EIT as a non-invasive methodological approach for the monitoring and physiological, i.e., functional, characterization of crop root systems. The approach combines the spatial-resolution capability of an imaging method with the diagnostic potential of electrical-impedance spectroscopy. The capability of multi-frequency EIT to characterize and monitor crop root systems was investigated in a rhizotron laboratory experiment, in which the root system of oilseed plants was monitored in a water-filled rhizotron, that is, in a nutrient-deprived environment. We found a low-frequency polarization response of the root system, which enabled the successful delineation of its spatial extension. The magnitude of the overall polarization response decreased along with the physiological decay of the root system due to the stress situation. Spectral polarization parameters, as derived from a pixel-based Debye decomposition analysis of the multi-frequency imaging results, reveal systematic changes in the spatial and spectral electrical response of the root system. In particular, quantified mean relaxation times (of the order of 10 ms) indicate changes in the length scales on which the polarization processes took place in the root system, as a response to the prolonged induced stress situation. Our results demonstrate that broadband EIT is a capable, non-invasive method to image root system extension as well as to monitor changes associated with the root physiological processes. Given its applicability on both laboratory and field scales, our results suggest an enormous potential of the method for the structural and functional imaging of root systems for various applications. This particularly holds for the field scale, where corresponding methods are highly desired but to date are lacking.

Development of a Dynamic Biomechanical Model for Load Carriage: Phase 1 Part A: Equipment Upgrades to Accommodate Dynamic Biomechanical Modeling

DTIC Science & Technology

2005-08-01

of a magnetic tracking device to kinesiology studies. J. Biomech. 21(7), 613-620, 1988. Bryant, J.T. Stevenson, J.M., Pelot, R.P., Reid, S.A...kangaroos (Macropus rufus). Comparative Biochemistry and Physiology, Part B 120:41-49, 1998. Kram, R. Are efficiency and the cost of generating force both

Coordinated post-translational responses of aquaporins to abiotic and nutritional stimuli in Arabidopsis roots.

PubMed

di Pietro, Magali; Vialaret, Jérôme; Li, Guo-Wei; Hem, Sonia; Prado, Karine; Rossignol, Michel; Maurel, Christophe; Santoni, Véronique

2013-12-01

In plants, aquaporins play a crucial role in regulating root water transport in response to environmental and physiological cues. Controls achieved at the post-translational level are thought to be of critical importance for regulating aquaporin function. To investigate the general molecular mechanisms involved, we performed, using the model species Arabidopsis, a comprehensive proteomic analysis of root aquaporins in a large set of physiological contexts. We identified nine physiological treatments that modulate root hydraulics in time frames of minutes (NO and H2O2 treatments), hours (mannitol and NaCl treatments, exposure to darkness and reversal with sucrose, phosphate supply to phosphate-starved roots), or days (phosphate or nitrogen starvation). All treatments induced inhibition of root water transport except for sucrose supply to dark-grown plants and phosphate resupply to phosphate-starved plants, which had opposing effects. Using a robust label-free quantitative proteomic methodology, we identified 12 of 13 plasma membrane intrinsic protein (PIP) aquaporin isoforms, 4 of the 10 tonoplast intrinsic protein isoforms, and a diversity of post-translational modifications including phosphorylation, methylation, deamidation, and acetylation. A total of 55 aquaporin peptides displayed significant changes after treatments and enabled the identification of specific and as yet unknown patterns of response to stimuli. The data show that the regulation of PIP and tonoplast intrinsic protein abundance was involved in response to a few treatments (i.e. NaCl, NO, and nitrate starvation), whereas changes in the phosphorylation status of PIP aquaporins were positively correlated to changes in root hydraulic conductivity in the whole set of treatments. The identification of in vivo deamidated forms of aquaporins and their stimulus-induced changes in abundance may reflect a new mechanism of aquaporin regulation. The overall work provides deep insights into the in vivo post-translational events triggered by environmental constraints and their possible role in regulating plant water status.

Introgression of Novel Traits from a Wild Wheat Relative Improves Drought Adaptation in Wheat1[W

PubMed Central

Placido, Dante F.; Campbell, Malachy T.; Folsom, Jing J.; Cui, Xinping; Kruger, Greg R.; Baenziger, P. Stephen; Walia, Harkamal

2013-01-01

Root architecture traits are an important component for improving water stress adaptation. However, selection for aboveground traits under favorable environments in modern cultivars may have led to an inadvertent loss of genes and novel alleles beneficial for adapting to environments with limited water. In this study, we elucidate the physiological and molecular consequences of introgressing an alien chromosome segment (7DL) from a wild wheat relative species (Agropyron elongatum) into cultivated wheat (Triticum aestivum). The wheat translocation line had improved water stress adaptation and higher root and shoot biomass compared with the control genotypes, which showed significant drops in root and shoot biomass during stress. Enhanced access to water due to higher root biomass enabled the translocation line to maintain more favorable gas-exchange and carbon assimilation levels relative to the wild-type wheat genotypes during water stress. Transcriptome analysis identified candidate genes associated with root development. Two of these candidate genes mapped to the site of translocation on chromosome 7DL based on single-feature polymorphism analysis. A brassinosteroid signaling pathway was predicted to be involved in the novel root responses observed in the A. elongatum translocation line, based on the coexpression-based gene network generated by seeding the network with the candidate genes. We present an effective and highly integrated approach that combines root phenotyping, whole-plant physiology, and functional genomics to discover novel root traits and the underlying genes from a wild related species to improve drought adaptation in cultivated wheat. PMID:23426195

Forest Health in the Southeastern United States: Assessment of the State of the Science

DTIC Science & Technology

2008-06-01

pathogens, including imbalances in populations of in- sect pests and root-infesting fungi (e.g., Leptographium species), that may degrade tree physiological...reintroduction exacerbates stress levels and contributes to further root colonization by fungi such as Leptographium sp. Root disease caused by the...Coleoptera: Scolytidae), are likely vectors for the Leptographium/Ophiostomatoid fungi (Eckhardt et al. 2004). Spores of these fungi are not suited to

Integration of Cadmium Accumulation, Subcellular Distribution, and Physiological Responses to Understand Cadmium Tolerance in Apple Rootstocks

PubMed Central

Zhou, Jiangtao; Wan, Huixue; He, Jiali; Lyu, Deguo; Li, Huifeng

2017-01-01

Cadmium (Cd) is a nonessential and highly toxic element causing agricultural problems. However, little information is available about the variation in Cd tolerance among apple rootstocks and its underlying physiological regulation mechanisms. This study investigated Cd accumulation, subcellular distribution, and chemical forms as well as physiological changes among four apple rootstocks exposed to either 0 or 300 μM CdCl2. The results showed that variations in Cd tolerance existed among these rootstocks. Cd exposure caused decline in photosynthesis, chlorophyll and biomass in four apple rootstocks, which was less pronounced in M. baccata, indicating its higher Cd tolerance. This finding was corroborated with higher Cd tolerance indexes (TIs) of the whole plant in M. baccata than those in the other three apple rootstocks. Among the four apple rootstocks, M. baccata displayed the lowest Cd concentrations in roots, wood, and leaves, the smallest total Cd amounts as well as the lowest BCF. In apple rootstocks, it was found that to immobilize Cd in cell wall and soluble fraction (most likely in vacuole) and to convert it into pectate- or protein- integrated forms and undissolved Cd phosphate forms may be the primary strategies to reduce Cd mobility and toxicity. The physiological changes including ROS, carbohydrates and antioxidants were in line with the variations of Cd tolerance among four apple rootstocks. In comparison with the other three apple rootstocks, M. baccata had lower concentrations of ROS in roots and bark, H2O2 in roots and leaves and MDA in roots, wood and bark, but higher concentrations of soluble sugars in bark and starch in roots and leaves, and enhanced antioxidants. These results indicate that M. baccata are more tolerant to Cd stress than the other three apple rootstocks under the current experiment conditions, which is probably related to Cd accumulation, subcellular partitioning and chemical forms of Cd and well-coordinated antioxidant defense mechanisms. PMID:28638400

Petunia as model for elucidating adventitious root formation and mycorrhizal symbiosis: at the nexus of physiology, genetics, microbiology and horticulture.

PubMed

Druege, Uwe; Franken, Philipp

2018-05-17

Adventitious root formation in cuttings and establishment of arbuscular mycorrhizal symbiosis reflect the enormous plasticity of plants and are key factors in the efficient and sustainable clonal propagation and production of ornamental crops. Based on the high importance of Petunia hybrida for the European and US annual bedding plant markets and its suitability as a model for basic plant sciences, petunia has been established as an experimental system for elucidating the molecular and physiological processes underlying adventitious root formation and mycorrhizal symbiosis. In the present review, we introduce the tools of the Petunia model system. Then, we discuss findings regarding the hormonal and metabolic control of adventitious rooting in the context of diverse environmental factors as well as findings on the function of arbuscular mycorrhiza related to nutrient uptake and resistance to root pathogens. Considering the recent publication of the genomes of the parental species of P. hybrida and other tools available in the petunia scientific community, we will outline the quality of petunia as a model for future system-oriented analysis of root development and function in the context of environmental and genetic control, which are at the heart of modern horticulture. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Developmental Physiology of Cluster-Root Carboxylate Synthesis and Exudation in Harsh Hakea. Expression of Phosphoenolpyruvate Carboxylase and the Alternative Oxidase1

PubMed Central

Shane, Michael W.; Cramer, Michael D.; Funayama-Noguchi, Sachiko; Cawthray, Gregory R.; Millar, A. Harvey; Day, David A.; Lambers, Hans

2004-01-01

Harsh hakea (Hakea prostrata R.Br.) is a member of the Proteaceae family, which is highly represented on the extremely nutrient-impoverished soils in southwest Australia. When phosphorus is limiting, harsh hakea develops proteoid or cluster roots that release carboxylates that mobilize sparingly soluble phosphate in the rhizosphere. To investigate the physiology underlying the synthesis and exudation of carboxylates from cluster roots in Proteaceae, we measured O2 consumption, CO2 release, internal carboxylate concentrations and carboxylate exudation, and the abundance of the enzymes phosphoenolpyruvate carboxylase and alternative oxidase (AOX) over a 3-week time course of cluster-root development. Peak rates of citrate and malate exudation were observed from 12- to 13-d-old cluster roots, preceded by a reduction in cluster-root total protein levels and a reduced rate of O2 consumption. In harsh hakea, phosphoenolpyruvate carboxylase expression was relatively constant in cluster roots, regardless of developmental stage. During cluster-root maturation, however, the expression of AOX protein increased prior to the time when citrate and malate exudation peaked. This increase in AOX protein levels is presumably needed to allow a greater flow of electrons through the mitochondrial electron transport chain in the absence of rapid ATP turnover. Citrate and isocitrate synthesis and accumulation contributed in a major way to the subsequent burst of citrate and malate exudation. Phosphorus accumulated by harsh hakea cluster roots was remobilized during senescence as part of their efficient P cycling strategy for growth on nutrient impoverished soils. PMID:15122030

Reactive oxygen species triggering systemic programmed cell death process via elevation of nuclear calcium ion level in tomatoes resisting tobacco mosaic virus.

PubMed

Li, Yang; Li, Qi; Hong, Qiang; Lin, Yichun; Mao, Wang; Zhou, Shumin

2018-05-01

Programmed cell death (PCD) plays a positive role in the systemic response of plants to pathogen resistance. It has been confirmed that local tobacco mosaic virus (TMV) infecting tomato leaves can induce systemic PCD process in root-tip tissues. But up to now the underlying physiological mechanisms are poorly understood. This study focused on the detailed investigation of the physiological responses of root-tip cells during the initiation of systemic PCD. Physiological, biochemical examination and cytological observation showed that 1 day post-inoculation (dpi) of TMV inoculation there was an increase in calcium fluorescence intensity in root tip tissue cells. Then at 2 dpi, 4 dpi, 8 dpi and 15 dpi, the fluorescence intensity of calcium ion continued to increase. However, at 5 dpi, the reactive oxygen species (ROS) began to accumulate in the root-tip cells. And finally at 20 dpi, the obvious PCD reaction was detected. In addition, the experimental results also showed that the above process involved the elevation of two types of intracellular Ca 2+ , including cytoplasmic calcium ([Ca 2+ ] cyt ) and nuclear calcium ([Ca 2+ ] nuc ). The [Ca 2+ ] cyt , as a pilot signal could lead to the subsequent elevation of intracellular ROS concentration. Then, the high levels of ROS stimulated an increase of [Ca 2+ ] nuc and eventually caused PCD reactions in the root-tip tissues. In particular, the high level of nuclear calcium is an essential mediator in systemic PCD of plants. Copyright © 2018 Elsevier B.V. All rights reserved.

Root gravitropism: a complex response to a simple stimulus?

NASA Technical Reports Server (NTRS)

Rosen, E.; Chen, R.; Masson, P. H.

1999-01-01

Roots avoid depleting their immediate environment of essential nutrients by continuous growth. Root growth is directed by environmental cues, including gravity. Gravity sensing occurs mainly in the columella cells of the root cap. Upon reorientation within the gravity field, the root-cap amyloplasts sediment, generating a physiological signal that promotes the development of a curvature at the root elongation zones. Recent molecular genetic studies in Arabidopsis have allowed the identification of genes that play important roles in root gravitropism. Among them, the ARG1 gene encodes a DnaJ-like protein involved in gravity signal transduction, whereas the AUX1 and AGR1 genes encode proteins involved in polar auxin transport. These studies have important implications for understanding the intra- and inter-cellular signaling processes that underlie root gravitropism.

Characterization of the growth and auxin physiology of roots of the tomato mutant, diageotropica

NASA Technical Reports Server (NTRS)

Muday, G. K.; Lomax, T. L.; Rayle, D. L.

1995-01-01

Roots of the tomato (Lycopersicon esculentum, Mill.) mutant (diageotropica (dgt) exhibit an altered phenotype. These roots are agravitropic and lack lateral roots. Relative to wild-type (VFN8) roots, dgt roots are less sensitive to growth inhibition by exogenously applied IAA and auxin transport inhibitors (phytotropins), and the roots exhibit a reduction in maximal growth inhibition in response to ethylene. However, IAA transport through roots, binding of the phytotropin, tritiated naphthylphthalamic acid ([3H]NPA), to root microsomal membranes, NPA-sensitive IAA uptake by root segments, and uptake of [3H]NPA into root segments are all similar in mutant and wild-type roots. We speculate that the reduced sensitivity of dgt root growth to auxin-transport inhibitors and ethylene is an indirect result of the reduction in sensitivity to auxin in this single gene, recessive mutant. We conclude that dgt roots, like dgt shoots, exhibit abnormalities indicating they have a defect associated with or affecting a primary site of auxin perception or action.

Water consumption and water-saving characteristics of a ground cover rice production system

NASA Astrophysics Data System (ADS)

Jin, Xinxin; Zuo, Qiang; Ma, Wenwen; Li, Sen; Shi, Jianchu; Tao, Yueyue; Zhang, Yanan; Liu, Yang; Liu, Xiaofei; Lin, Shan; Ben-Gal, Alon

2016-09-01

The ground cover rice production system (GCRPS) offers a potentially water-saving alternative to the traditional paddy rice production system (TPRPS) by furrow irrigating mulched soil beds and maintaining soils under predominately unsaturated conditions. The guiding hypothesis of this study was that a GCRPS would decrease both physiological and non-physiological water consumption of rice compared to a TPRPS while either maintaining or enhancing production. This was tested in a two-year field experiment with three treatments (TPRPS, GCRPSsat keeping root zone average soil water content near saturated, and GCRPS80% keeping root zone average soil water content as 80-100% of field water capacity) and a greenhouse experiment with four treatments (TPRPS, GCRPSsat, GCRPSfwc keeping root zone average soil water content close to field water capacity, and GCRPS80%). The water-saving characteristics of GCRPS were analyzed as a function of the measured soil water conditions, plant parameters regarding growth and production, and water input and consumption. In the field experiment, significant reduction in both physiological and non-physiological water consumption under GCRPS lead to savings in irrigation water of ∼61-84% and reduction in total input water of ∼35-47%. Compared to TPRPS, deep drainage was reduced ∼72-88%, evaporation was lessened ∼83-89% and transpiration was limited ∼6-10% under GCRPS. In addition to saving water, plant growth and grain yield were enhanced under GCRPS due to increased soil temperature in the root zone. Therefore, water use efficiencies (WUEs), based on transpiration, irrigation and total input water, were respectively improved as much as 27%, 609% and 110% under GCRPS. Increased yield attributed to up to ∼19%, decreased deep drainage accounted for ∼75%, decreased evaporation accounted for ∼14% and reduced transpiration for ∼5% of the enhancement in WUE of input water under GCRPS, while increased runoff and water storage had negative influence on WUE (-7.5 and -3.7%, respectively) for GCRPS compared to TPRPS. The greenhouse experiment validated the results obtained in the field by simplifying the non-physiological water consumption processes, and thus confirming the relative importance of physiological processes and increased WUE under GCRPS.

Regeneration and productivity of aspen grown on repeated short rotations.

Treesearch

Donald A. Perala

1979-01-01

Regeneration and productivity of aspen cannot be sustained on rotations shorter than about 8 years. Productivity losses on short rotations are physiological and morphological rather than nutritional in nature. Stump and root collar sprouts, which are rare in mature stands, were more numerous than root suckers.

Adventitious root formation in tree species: involvement of transcription factors.

PubMed

Legué, Valérie; Rigal, Adeline; Bhalerao, Rishikesh P

2014-06-01

Adventitious rooting is an essential step in the vegetative propagation of economically important horticultural and woody species. Populus has emerged as an experimental model for studying processes that are important in tree growth and development. It is highly useful for molecular genetic analysis of adventitious roots in trees. In this short review, we will highlight the recent progress made in the identification of transcription factors involved in the control of adventitious rooting in woody species. Their regulation will be discussed. © 2014 Scandinavian Plant Physiology Society.

Inhibitory effects of KN-93, an inhibitor of Ca2+ calmodulin-dependent protein kinase II, on light-regulated root gravitropism in maize

NASA Technical Reports Server (NTRS)

Feldman, L. J.; Hidaka, H.

1993-01-01

Light is essential for root gravitropism in Zea mays L., cultivar Merit. It is hypothesized that calcium mediates this light-regulated response. KN-93, an inhibitor of calcium/calmodulin kinase II (CaMK II), inhibits light-regulated root gravitropism but does not affect light perception. We hypothesize that CaMK II, or a homologue, operates late in the light/gravity signal transduction chain. Here we provide evidence suggesting a possible physiological involvement of CaMK II in root gravitropism in plants.

Hairy root biotechnology--indicative timeline to understand missing links and future outlook.

PubMed

Mehrotra, Shakti; Srivastava, Vikas; Ur Rahman, Laiq; Kukreja, A K

2015-09-01

Agrobacterium rhizogenes-mediated hairy roots (HR) were developed in the laboratory to mimic the natural phenomenon of bacterial gene transfer and occurrence of disease syndrome. The timeline analysis revealed that during 90 s, the research expanded to the hairy root-based secondary metabolite production and different yield enhancement strategies like media optimization, up-scaling, metabolic engineering etc. An outlook indicates that much emphasis has been given to the strategies that are helpful in making this technology more practical in terms of high productivity at low cost. However, a sequential analysis of literature shows that this technique is upgraded to a biotechnology platform where different intra- and interdisciplinary work areas were established, progressed, and diverged to provide scientific benefits of various hairy root-based applications like phytoremediation, molecular farming, biotransformation, etc. In the present scenario, this biotechnology research platform includes (a) elemental research like hairy root-mediated secondary metabolite production coupled with productivity enhancement strategies and (b) HR-based functional research. The latter comprised of hairy root-based applied aspects such as generation of agro-economical traits in plants, production of high value as well as less hazardous molecules through biotransformation/farming and remediation, respectively. This review presents an indicative timeline portrayal of hairy root research reflected by a chronology of research outputs. The timeline also reveals a progressive trend in the state-of-art global advances in hairy root biotechnology. Furthermore, the review also discusses ideas to explore missing links and to deal with the challenges in future progression and prospects of research in all related fields of this important area of plant biotechnology.

Molecular and physiological strategies to increase aluminum resistance in plants.

PubMed

Inostroza-Blancheteau, Claudio; Rengel, Zed; Alberdi, Miren; de la Luz Mora, María; Aquea, Felipe; Arce-Johnson, Patricio; Reyes-Díaz, Marjorie

2012-03-01

Aluminum (Al) toxicity is a primary limitation to plant growth on acid soils. Root meristems are the first site for toxic Al accumulation, and therefore inhibition of root elongation is the most evident physiological manifestation of Al toxicity. Plants may resist Al toxicity by avoidance (Al exclusion) and/or tolerance mechanisms (detoxification of Al inside the cells). The Al exclusion involves the exudation of organic acid anions from the root apices, whereas tolerance mechanisms comprise internal Al detoxification by organic acid anions and enhanced scavenging of free oxygen radicals. One of the most important advances in understanding the molecular events associated with the Al exclusion mechanism was the identification of the ALMT1 gene (Al-activated malate transporter) in Triticum aestivum root cells, which codes for a plasma membrane anion channel that allows efflux of organic acid anions, such as malate, citrate or oxalate. On the other hand, the scavenging of free radicals is dependent on the expression of genes involved in antioxidant defenses, such as peroxidases (e.g. in Arabidopsis thaliana and Nicotiana tabacum), catalases (e.g. in Capsicum annuum), and the gene WMnSOD1 from T. aestivum. However, other recent findings show that reactive oxygen species (ROS) induced stress may be due to acidic (low pH) conditions rather than to Al stress. In this review, we summarize recent findings regarding molecular and physiological mechanisms of Al toxicity and resistance in higher plants. Advances have been made in understanding some of the underlying strategies that plants use to cope with Al toxicity. Furthermore, we discuss the physiological and molecular responses to Al toxicity, including genes involved in Al resistance that have been identified and characterized in several plant species. The better understanding of these strategies and mechanisms is essential for improving plant performance in acidic, Al-toxic soils.

GLO-Roots: an imaging platform enabling multidimensional characterization of soil-grown root systems

PubMed Central

Rellán-Álvarez, Rubén; Lobet, Guillaume; Lindner, Heike; Pradier, Pierre-Luc; Sebastian, Jose; Yee, Muh-Ching; Geng, Yu; Trontin, Charlotte; LaRue, Therese; Schrager-Lavelle, Amanda; Haney, Cara H; Nieu, Rita; Maloof, Julin; Vogel, John P; Dinneny, José R

2015-01-01

Root systems develop different root types that individually sense cues from their local environment and integrate this information with systemic signals. This complex multi-dimensional amalgam of inputs enables continuous adjustment of root growth rates, direction, and metabolic activity that define a dynamic physical network. Current methods for analyzing root biology balance physiological relevance with imaging capability. To bridge this divide, we developed an integrated-imaging system called Growth and Luminescence Observatory for Roots (GLO-Roots) that uses luminescence-based reporters to enable studies of root architecture and gene expression patterns in soil-grown, light-shielded roots. We have developed image analysis algorithms that allow the spatial integration of soil properties, gene expression, and root system architecture traits. We propose GLO-Roots as a system that has great utility in presenting environmental stimuli to roots in ways that evoke natural adaptive responses and in providing tools for studying the multi-dimensional nature of such processes. DOI: http://dx.doi.org/10.7554/eLife.07597.001 PMID:26287479

GLO-Roots: An imaging platform enabling multidimensional characterization of soil-grown root systems

DOE PAGES

Rellan-Alvarez, Ruben; Lobet, Guillaume; Lindner, Heike; ...

2015-08-19

Root systems develop different root types that individually sense cues from their local environment and integrate this information with systemic signals. This complex multi-dimensional amalgam of inputs enables continuous adjustment of root growth rates, direction, and metabolic activity that define a dynamic physical network. Current methods for analyzing root biology balance physiological relevance with imaging capability. To bridge this divide, we developed an integrated-imaging system called Growth and Luminescence Observatory for Roots (GLO-Roots) that uses luminescence-based reporters to enable studies of root architecture and gene expression patterns in soil-grown, light-shielded roots. We have developed image analysis algorithms that allow themore » spatial integration of soil properties, gene expression, and root system architecture traits. We propose GLO-Roots as a system that has great utility in presenting environmental stimuli to roots in ways that evoke natural adaptive responses and in providing tools for studying the multi-dimensional nature of such processes.« less

Physiological characters of soybean cultivars with application of nitrogen sources under dry land conditions

NASA Astrophysics Data System (ADS)

Hasanah, Y.; Nisa, T. C.; Hapsoh; Hanum, H.

2018-02-01

The objective of this study was to evaluate the influence of nutrient N management on physiological characteristics of three different soybean cultivars under dry land conditions. The study was conducted under dry lands of Desa Sambirejo (Langkat Regency) in the dry season. The study was conducted with a Randomize Block Design with two factors and three replication. The research was used a randomized block design with 2 factors and 3 replications. The first factor was soybean cultivars (Anjasmoro, Wilis, Sinabung). The second factor was N source, with Urea (50 kg/ha), Bradyrhizobium sp., farmyard manure (10 ton/ha), a combination of Bradyrhizobium sp. + farmyard manure (5 ton/ha) and a control with no N. The parameter observed in this study was the content of root N, shoot Nitrogen, shoot Phosphor, shoot Potassium and total of chlorophyll content. The results suggest that Anjasmoro and Sinabung cultivars had higher physiological characteristics (root N, shoot P and shoot K) compared to Wilis. Nitrogen source of Urea gave a higher physiological characteristics (content of root N, shoot Phosphor and shoot Potassium) compared to different treatment of N source in this study. The interaction between Anjasmoro cultivar and Urea gave the highest of content of shoot Phosphor and shoot Potassium, otherwise the interaction between Sinabung cultivar and Bradyrhizobium sp. gave the highest of content of shoot Nitrogen.

Through form to function: root hair development and nutrient uptake

NASA Technical Reports Server (NTRS)

Gilroy, S.; Jones, D. L.

2000-01-01

Root hairs project from the surface of the root to aid nutrient and water uptake and to anchor the plant in the soil. Their formation involves the precise control of cell fate and localized cell growth. We are now beginning to unravel the complexities of the molecular interactions that underlie this developmental regulation. In addition, after years of speculation, nutrient transport by root hairs has been demonstrated clearly at the physiological and molecular level, with evidence for root hairs being intense sites of H(+)-ATPase activity and involved in the uptake of Ca(2+), K(+), NH(4)(+), NO(3)(-), Mn(2+), Zn(2+), Cl(-) and H(2)PO(4)(-).

A Virtual Upgrade Validation Method for Software-Reliant Systems

DTIC Science & Technology

2012-06-01

3.4 Root Cause Areas of System-Level Faults 11 3.4.1 End-to-End Flow of Data Streams 11 3.4.2 Distributed Communicating State Machines 13 3.4.3...FlyByWire/FlyByWire_english.pdf (Accessed on November 11 , 2011.) [Apple 2005] Apple Support Communities , jazzman40. iTunes Crashes When Ripping...Strategies 39 7.1 Application Pattern Modeling Strategies 39 7.1.1 Control Loops 39 7.1.2 State Transition Communication 42 7.1.3 Sensor/Signal Fusion

Lessons Learned from the Space Shuttle Engine Cutoff System (ECO) Anomalies

NASA Technical Reports Server (NTRS)

Martinez, Hugo E.; Welzyn, Ken

2011-01-01

The Space Shuttle Orbiter's main engine cutoff (ECO) system first failed ground checkout in April, 2005 during a first tanking test prior to Return-to-Flight. Despite significant troubleshooting and investigative efforts that followed, the root cause could not be found and intermittent anomalies continued to plague the Program. By implementing hardware upgrades, enhancing monitoring capability, and relaxing the launch rules, the Shuttle fleet was allowed to continue flying in spite of these unexplained failures. Root cause was finally determined following the launch attempts of STS-122 in December, 2007 when the anomalies repeated, which allowed drag-on instrumentation to pinpoint the fault (the ET feedthrough connector). The suspect hardware was removed and provided additional evidence towards root cause determination. Corrective action was implemented and the system has performed successfully since then. This white paper presents the lessons learned from the entire experience, beginning with the anomalies since Return-to-Flight through discovery and correction of the problem. To put these lessons in better perspective for the reader, an overview of the ECO system is presented first. Next, a chronological account of the failures and associated investigation activities is discussed. Root cause and corrective action are summarized, followed by the lessons learned.

A framework for identifying plant species to be used as 'ecological engineers' for fixing soil on unstable slopes.

PubMed

Ghestem, Murielle; Cao, Kunfang; Ma, Wenzhang; Rowe, Nick; Leclerc, Raphaëlle; Gadenne, Clément; Stokes, Alexia

2014-01-01

Major reforestation programs have been initiated on hillsides prone to erosion and landslides in China, but no framework exists to guide managers in the choice of plant species. We developed such a framework based on the suitability of given plant traits for fixing soil on steep slopes in western Yunnan, China. We examined the utility of 55 native and exotic species with regard to the services they provided. We then chose nine species differing in life form. Plant root system architecture, root mechanical and physiological traits were then measured at two adjacent field sites. One site was highly unstable, with severe soil slippage and erosion. The second site had been replanted 8 years previously and appeared to be physically stable. How root traits differed between sites, season, depth in soil and distance from the plant stem were determined. Root system morphology was analysed by considering architectural traits (root angle, depth, diameter and volume) both up- and downslope. Significant differences between all factors were found, depending on species. We estimated the most useful architectural and mechanical traits for physically fixing soil in place. We then combined these results with those concerning root physiological traits, which were used as a proxy for root metabolic activity. Scores were assigned to each species based on traits. No one species possessed a suite of highly desirable traits, therefore mixtures of species should be used on vulnerable slopes. We also propose a conceptual model describing how to position plants on an unstable site, based on root system traits.

A Framework for Identifying Plant Species to Be Used as ‘Ecological Engineers’ for Fixing Soil on Unstable Slopes

PubMed Central

Ghestem, Murielle; Cao, Kunfang; Ma, Wenzhang; Rowe, Nick; Leclerc, Raphaëlle; Gadenne, Clément; Stokes, Alexia

2014-01-01

Major reforestation programs have been initiated on hillsides prone to erosion and landslides in China, but no framework exists to guide managers in the choice of plant species. We developed such a framework based on the suitability of given plant traits for fixing soil on steep slopes in western Yunnan, China. We examined the utility of 55 native and exotic species with regard to the services they provided. We then chose nine species differing in life form. Plant root system architecture, root mechanical and physiological traits were then measured at two adjacent field sites. One site was highly unstable, with severe soil slippage and erosion. The second site had been replanted 8 years previously and appeared to be physically stable. How root traits differed between sites, season, depth in soil and distance from the plant stem were determined. Root system morphology was analysed by considering architectural traits (root angle, depth, diameter and volume) both up- and downslope. Significant differences between all factors were found, depending on species. We estimated the most useful architectural and mechanical traits for physically fixing soil in place. We then combined these results with those concerning root physiological traits, which were used as a proxy for root metabolic activity. Scores were assigned to each species based on traits. No one species possessed a suite of highly desirable traits, therefore mixtures of species should be used on vulnerable slopes. We also propose a conceptual model describing how to position plants on an unstable site, based on root system traits. PMID:25105571

Root Hairs

PubMed Central

Grierson, Claire; Nielsen, Erik; Ketelaarc, Tijs; Schiefelbein, John

2014-01-01

Roots hairs are cylindrical extensions of root epidermal cells that are important for acquisition of nutrients, microbe interactions, and plant anchorage. The molecular mechanisms involved in the specification, differentiation, and physiology of root hairs in Arabidopsis are reviewed here. Root hair specification in Arabidopsis is determined by position-dependent signaling and molecular feedback loops causing differential accumulation of a WD-bHLH-Myb transcriptional complex. The initiation of root hairs is dependent on the RHD6 bHLH gene family and auxin to define the site of outgrowth. Root hair elongation relies on polarized cell expansion at the growing tip, which involves multiple integrated processes including cell secretion, endomembrane trafficking, cytoskeletal organization, and cell wall modifications. The study of root hair biology in Arabidopsis has provided a model cell type for insights into many aspects of plant development and cell biology. PMID:24982600

Engineering the expression level of cytosolic nucleoside diphosphate kinase in transgenic Solanum tuberosum roots alters growth, respiration and carbon metabolism.

PubMed

Dorion, Sonia; Clendenning, Audrey; Rivoal, Jean

2017-03-01

Nucleoside diphosphate kinase (NDPK) is a ubiquitous enzyme that catalyzes the transfer of the γ-phosphate from a donor nucleoside triphosphate to an acceptor nucleoside diphosphate. In this study we used a targeted metabolomic approach and measurement of physiological parameters to report the effects of the genetic manipulation of cytosolic NDPK (NDPK1) expression on physiology and carbon metabolism in potato (Solanum tuberosum) roots. Sense and antisense NDPK1 constructs were introduced in potato using Agrobacterium rhizogenes to generate a population of root clones displaying a 40-fold difference in NDPK activity. Root growth, O 2 uptake, flux of carbon between sucrose and CO 2 , levels of reactive oxygen species and some tricarboxylic acid cycle intermediates were positively correlated with levels of NDPK1 expression. In addition, NDPK1 levels positively affected UDP-glucose and cellulose contents. The activation state of ADP-glucose pyrophosphorylase, a key enzyme in starch synthesis, was higher in antisense roots than in roots overexpressing NDPK1. Further analyses demonstrated that ADP-glucose pyrophosphorylase was more oxidized, and therefore less active, in sense clones than antisense clones. Consequently, antisense NDPK1 roots accumulated more starch and the starch to cellulose ratio was negatively affected by the level of NDPK1. These data support the idea that modulation of NDPK1 affects the distribution of carbon between starch and cellulose biosynthetic pathways. © 2016 The Authors The Plant Journal © 2016 John Wiley & Sons Ltd.

Plant growth-promoting rhizobacteria and root system functioning

PubMed Central

Vacheron, Jordan; Desbrosses, Guilhem; Bouffaud, Marie-Lara; Touraine, Bruno; Moënne-Loccoz, Yvan; Muller, Daniel; Legendre, Laurent; Wisniewski-Dyé, Florence; Prigent-Combaret, Claire

2013-01-01

The rhizosphere supports the development and activity of a huge and diversified microbial community, including microorganisms capable to promote plant growth. Among the latter, plant growth-promoting rhizobacteria (PGPR) colonize roots of monocots and dicots, and enhance plant growth by direct and indirect mechanisms. Modification of root system architecture by PGPR implicates the production of phytohormones and other signals that lead, mostly, to enhanced lateral root branching and development of root hairs. PGPR also modify root functioning, improve plant nutrition and influence the physiology of the whole plant. Recent results provided first clues as to how PGPR signals could trigger these plant responses. Whether local and/or systemic, the plant molecular pathways involved remain often unknown. From an ecological point of view, it emerged that PGPR form coherent functional groups, whose rhizosphere ecology is influenced by a myriad of abiotic and biotic factors in natural and agricultural soils, and these factors can in turn modulate PGPR effects on roots. In this paper, we address novel knowledge and gaps on PGPR modes of action and signals, and highlight recent progress on the links between plant morphological and physiological effects induced by PGPR. We also show the importance of taking into account the size, diversity, and gene expression patterns of PGPR assemblages in the rhizosphere to better understand their impact on plant growth and functioning. Integrating mechanistic and ecological knowledge on PGPR populations in soil will be a prerequisite to develop novel management strategies for sustainable agriculture. PMID:24062756

CASIROZ: Root parameters and types of ectomycorrhiza of young beech plants exposed to different ozone and light regimes.

PubMed

Zeleznik, P; Hrenko, M; Then, C; Koch, N; Grebenc, T; Levanic, T; Kraigher, H

2007-03-01

Tropospheric ozone (O(3)) triggers physiological changes in leaves that affect carbon source strength leading to decreased carbon allocation below-ground, thus affecting roots and root symbionts. The effects of O(3) depend on the maturity-related physiological state of the plant, therefore adult and young forest trees might react differently. To test the applicability of young beech plants for studying the effects of O(3) on forest trees and forest stands, beech seedlings were planted in containers and exposed for two years in the Kranzberg forest FACOS experiment (Free-Air Canopy O(3) Exposure System, http://www.casiroz.de ) to enhanced ozone concentration regime (ambient [control] and double ambient concentration, not exceeding 150 ppb) under different light conditions (sun and shade). After two growing seasons the biomass of the above- and below-ground parts, beech roots (using WinRhizo programme), anatomical and molecular (ITS-RFLP and sequencing) identification of ectomycorrhizal types and nutrient concentrations were assessed. The mycorrhization of beech seedlings was very low ( CA. 5 % in shade, 10 % in sun-grown plants), no trends were observed in mycorrhization (%) due to ozone treatment. The number of Cenococcum geophilum type of ectomycorrhiza, as an indicator of stress in the forest stands, was not significantly different under different ozone treatments. It was predominantly occurring in sun-exposed plants, while its majority share was replaced by Genea hispidula in shade-grown plants. Different light regimes significantly influenced all parameters except shoot/root ratio and number of ectomycorrhizal types. In the ozone fumigated plants the number of types, number of root tips per length of 1 to 2 mm root diameter, root length density per volume of soil and concentration of Mg were significantly lower than in control plants. Trends to a decrease were found in root, shoot, leaf, and total dry weights, total number of root tips, number of vital mycorrhizal root tips, fine root (mass) density, root tip density per surface, root area index, concentration of Zn, and Ca/Al ratio. Due to the general reduction in root growth indices and nutrient cycling in ozone-fumigated plants, alterations in soil carbon pools could be predicted.

Physiological and biochemical responses of Salix integra Thunb. under copper stress as affected by soil flooding.

PubMed

Cao, Yini; Ma, Chuanxin; Chen, Guangcai; Zhang, Jianfeng; Xing, Baoshan

2017-06-01

To explore the joint effect of copper (Cu) and flooding on Salix integra Thunb. (S. integra), the physiological and biochemical parameters of the seedlings grown in Cu amended soil (50, 150, 450 mg kg -1 ) with or without the flooding for 60 days were evaluated. The results suggested that the flooding significantly inhibited the root growth in terms of root length and root tips. The Cu exposures of 50 and 150 mg kg -1 notably enhanced the root growth as compared to the control. Majority of Cu was accumulated in S. integra roots, while flooding significantly reduced the Cu content, except the 150 mg kg -1 Cu treatment, but the iron (Fe) and manganese (Mn) content on the root surface were both markedly increased relative to non-flooded control. The malonaldehyde (MDA) and glutathione (GSH) contents in leaves showed a dose-response upon Cu exposure. Soil flooding enhanced the GSH level, which displayed 4.50-49.59% increases compared to its respective non-flooded treatment, while no difference was evident on MDA contents between the flooding and the non-flooded treatments. Both superoxide dismutase (SOD) and peroxidase (POD) activities were boosted while the catalase (CAT) was suppressed with increasing Cu exposure dose, and soil flooding reduced the POD and CAT activities. The elevated Cu level caused the evident increases of root calcium (Ca), potassium (K), and sulfur (S) concentrations and decreases of root phosphorus (P), sodium (Na), and zinc (Zn) concentrations. Soil flooding increased the concentrations of Fe, S, Na, Ca, and magnesium (Mg) in S. integra root. Taken together, our results suggested S. integra has high tolerance to the joint stress from Cu and flooding. Copyright © 2017 Elsevier Ltd. All rights reserved.

There's a World Going on Underground: Imaging Technologies to Understand Root Growth Dynamics and Rhizosphere Interactions

NASA Astrophysics Data System (ADS)

Topp, C. N.

2016-12-01

Our ability to harness the power of plant genomics for basic and applied science depends on how well and how fast we can quantify the phenotypic ramifications of genetic variation. Plants can be considered from many vantage points: at scales from cells to organs, over the course of development or evolution, and from biophysical, physiological, and ecological perspectives. In all of these ways, our understanding of plant form and function is greatly limited by our ability to study subterranean structures and processes. The limitations to accessing this knowledge are well known - soil is opaque, roots are morphologically complex, and root growth can be heavily influenced by a myriad of environmental factors. Nonetheless, recent technological innovations in imaging science have generated a renewed focus on roots and thus new opportunities to understand the plant as a whole. The Topp Lab is interested in crop root system growth dynamics and function in response to environmental stresses such as drought, rhizosphere interactions, and as a consequence of artificial selection for agronomically important traits such as nitrogen uptake and high plant density. Studying roots requires the development of imaging technologies, computational infrastructure, and statistical methods that can capture and analyze morphologically complex networks over time and at high-throughput. The lab uses several imaging tools (optical, X-ray CT, PET, etc.) along with quantitative genetics and molecular biology to understand the dynamics of root growth and physiology. We aim to understand the relationships among root traits that can be effectively measured both in controlled laboratory environments and in the field, and to identify genes and gene networks that control root, and ultimately whole plant architectural features useful for crop improvement.

Virtual Plants Need Water Too: Functional-Structural Root System Models in the Context of Drought Tolerance Breeding

PubMed Central

Ndour, Adama; Vadez, Vincent; Pradal, Christophe; Lucas, Mikaël

2017-01-01

Developing a sustainable agricultural model is one of the great challenges of the coming years. The agricultural practices inherited from the Green Revolution of the 1960s show their limits today, and new paradigms need to be explored to counter rising issues such as the multiplication of climate-change related drought episodes. Two such new paradigms are the use of functional-structural plant models to complement and rationalize breeding approaches and a renewed focus on root systems as untapped sources of plant amelioration. Since the late 1980s, numerous functional and structural models of root systems were developed and used to investigate the properties of root systems in soil or lab-conditions. In this review, we focus on the conception and use of such root models in the broader context of research on root-driven drought tolerance, on the basis of root system architecture (RSA) phenotyping. Such models result from the integration of architectural, physiological and environmental data. Here, we consider the different phenotyping techniques allowing for root architectural and physiological study and their limits. We discuss how QTL and breeding studies support the manipulation of RSA as a way to improve drought resistance. We then go over the integration of the generated data within architectural models, how those architectural models can be coupled with functional hydraulic models, and how functional parameters can be measured to feed those models. We then consider the assessment and validation of those hydraulic models through confrontation of simulations to experimentations. Finally, we discuss the up and coming challenges facing root systems functional-structural modeling approaches in the context of breeding. PMID:29018456

Virtual Plants Need Water Too: Functional-Structural Root System Models in the Context of Drought Tolerance Breeding.

PubMed

Ndour, Adama; Vadez, Vincent; Pradal, Christophe; Lucas, Mikaël

2017-01-01

Developing a sustainable agricultural model is one of the great challenges of the coming years. The agricultural practices inherited from the Green Revolution of the 1960s show their limits today, and new paradigms need to be explored to counter rising issues such as the multiplication of climate-change related drought episodes. Two such new paradigms are the use of functional-structural plant models to complement and rationalize breeding approaches and a renewed focus on root systems as untapped sources of plant amelioration. Since the late 1980s, numerous functional and structural models of root systems were developed and used to investigate the properties of root systems in soil or lab-conditions. In this review, we focus on the conception and use of such root models in the broader context of research on root-driven drought tolerance, on the basis of root system architecture (RSA) phenotyping. Such models result from the integration of architectural, physiological and environmental data. Here, we consider the different phenotyping techniques allowing for root architectural and physiological study and their limits. We discuss how QTL and breeding studies support the manipulation of RSA as a way to improve drought resistance. We then go over the integration of the generated data within architectural models, how those architectural models can be coupled with functional hydraulic models, and how functional parameters can be measured to feed those models. We then consider the assessment and validation of those hydraulic models through confrontation of simulations to experimentations. Finally, we discuss the up and coming challenges facing root systems functional-structural modeling approaches in the context of breeding.

Small peptide signaling pathways modulating macronutrient utilization in plants.

PubMed

de Bang, Thomas C; Lay, Katerina S; Scheible, Wolf-Rüdiger; Takahashi, Hideki

2017-10-01

Root system architecture (RSA) and physiological functions define macronutrient uptake efficiency. Small signaling peptides (SSPs), that act in manners similar to hormones, and their cognate receptors transmit signals both locally and systemically. Several SSPs controlling morphological and physiological traits of roots have been identified to be associated with macronutrient uptake. Recent development in plant genome research has provided an avenue toward systems-based identification and prediction of additional SSPs. This review highlights recent studies on SSP pathways important for optimization of macronutrient uptake and provides new insights into the diversity of SSPs regulated in response to changes in macronutrient availabilities. Copyright © 2017 Elsevier Ltd. All rights reserved.

Metabolomics combined with chemometric tools (PCA, HCA, PLS-DA and SVM) for screening cassava (Manihot esculenta Crantz) roots during postharvest physiological deterioration.

PubMed

Uarrota, Virgílio Gavicho; Moresco, Rodolfo; Coelho, Bianca; Nunes, Eduardo da Costa; Peruch, Luiz Augusto Martins; Neubert, Enilto de Oliveira; Rocha, Miguel; Maraschin, Marcelo

2014-10-15

Cassava roots are an important source of dietary and industrial carbohydrates and suffer markedly from postharvest physiological deterioration (PPD). This paper deals with metabolomics combined with chemometric tools for screening the chemical and enzymatic composition in several genotypes of cassava roots during PPD. Metabolome analyses showed increases in carotenoids, flavonoids, anthocyanins, phenolics, reactive scavenging species, and enzymes (superoxide dismutase family, hydrogen peroxide, and catalase) until 3-5days postharvest. PPD correlated negatively with phenolics and carotenoids and positively with anthocyanins and flavonoids. Chemometric tools such as principal component analysis, partial least squares discriminant analysis, and support vector machines discriminated well cassava samples and enabled a good prediction of samples. Hierarchical clustering analyses grouped samples according to their levels of PPD and chemical compositions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Physiological response and sulfur metabolism of the V. dahliae-infected tomato plants in tomato/potato onion companion cropping.

PubMed

Fu, Xuepeng; Li, Chunxia; Zhou, Xingang; Liu, Shouwei; Wu, Fengzhi

2016-11-03

Companion cropping with potato onions (Allium cepa var. agrogatum Don.) can enhance the disease resistance of tomato plants (Solanum lycopersicum) to Verticillium dahliae infection by increasing the expressions of genes related to disease resistance. However, it is not clear how tomato plants physiologically respond to V. dahliae infection and what roles sulfur plays in the disease-resistance. Pot experiments were performed to examine changes in the physiology and sulfur metabolism of tomato roots infected by V. dahliae under the companion cropping (tomato/potato onion). The results showed that the companion cropping increased the content of total phenol, lignin and glutathione and increased the activities of peroxidase, polyphenol oxidase and phenylalanine ammonia lyase in the roots of tomato plants. RNA-seq analysis showed that the expressions of genes involved in sulfur uptake and assimilation, and the formation of sulfur-containing defense compounds (SDCs) were up-regulated in the V. dahlia-infected tomatoes in the companion cropping. In addition, the interactions among tomato, potato onion and V. dahliae induced the expression of the high- affinity sulfate transporter gene in the tomato roots. These results suggest that sulfur may play important roles in tomato disease resistance against V. dahliae.

PHYSIOLOGICAL ECOLOGY OF CLOSTRIDIUM GLYCOLICUM RD-1, AN AEROTOLERANT ACETOGEN ISOLATED FROM SEA GRASS ROOTS

EPA Science Inventory

An anaerobic, H2-utilizing bacterium, strain RD-1, was isolated from the highest growth-positive dilution series of a root homogenate prepared from the sea grass Halodule wrightii. Cells of RD-1 were gram-positive, spore-forming, motile rods that were linked by connecting filamen...

Transplant shock of northern red oak seedlings following simulated drought as influenced by root morphology

Treesearch

Douglass F. Jacobs; Francis Salifu; Anthony Davis

2005-01-01

Transplant shock, implicated by depressed seedling physiological response associated with moisture or nutrient stress immediately following planting, limits early plantation establishment. We investigated the impacts of simulated drought and transplant root volume on predawn leaf xylem water potential, photosynthetic assimilation rates, stomatal conductance, and growth...

Microsensor Technologies for Plant Growth System Monitoring

NASA Technical Reports Server (NTRS)

Kim, Chang-Soo

2004-01-01

This document covered the following: a) demonstration of feasibility of microsensor for tube and particulate growth systems; b) Dissolved oxygen; c)Wetness; d) Flexible microfluidic substrate with microfluidic channels and microsensor arrays; e)Dynamic root zone control/monitoring in microgravity; f)Rapid prototyping of phytoremediation; and g) A new tool for root physiology and pathology.

The development of spectro-signature indicators of root disease impacts on forest stands

NASA Technical Reports Server (NTRS)

Weber, F. P.; Wear, J. F.

1970-01-01

A field research program was begun in 1969 and intensified in 1970 on the physiology and biophysical responses of second-growth Douglas fir infected with root rot fungus. A double tramway system was suspended between three 100-foot instrument towers to carry sensors for measuring the energy response from above both healthy and infected trees. Processing and analysis was completed of airborne multispectral scanner imagery collected over the Wind River research area in 1969. Likelihood ratio processing of three-channel infrared data and Euclidean distance analysis of ten-channel spectrometer data did not identify incipient root rot infection outside the training sets. In all cases infected fir was misclassified as healthy fir. It was concluded from careful examination of physiological data that Poria root rot infection has little effect on water metabolism and energy exchange. What was identified was a low-grade stress that affects respiration and metabolism over long periods of time. This led to minor changes in the external physical symptoms of Poria-infected trees which was revealed only in the shortwave reflectance data.

Distinct physiological responses of tomato and cucumber plants in silicon-mediated alleviation of cadmium stress

PubMed Central

Wu, Jiawen; Guo, Jia; Hu, Yanhong; Gong, Haijun

2015-01-01

The alleviative effects of silicon (Si) on cadmium (Cd) toxicity were investigated in cucumber (Cucumis sativus L.) and tomato (Solanum lycopersicum L.) grown hydroponically. The growth of both plant species was inhibited by 100 μM Cd, but Si application counteracted the adverse effects on growth. Si application significantly decreased the Cd concentrations in shoots of both species and roots of cucumber. The root-to-shoot transport of Cd was depressed by added Si in tomato whereas it was increased by added Si in cucumber. The total content of organic acids was decreased in tomato leaves but increased in cucumber roots and leaves by Si application under Cd stress. Si application also increased the cell wall polysaccharide levels in the roots of both species under Cd toxicity. Si-mediated changes in levels of organic acids and cell wall polysaccharides might contribute to the differences in Cd transport in the two species. In addition, Si application also mitigated Cd-induced oxidative damage in both species. The results indicate that there were different mechanisms for Si-mediated decrease in shoot Cd accumulation: in tomato, Si supply decreased root-to-shoot Cd transport; whereas in cucumber, Si supply reduced the Cd uptake by roots. It is suggested that Si-mediated Cd tolerance is associated with different physiological responses in tomato and cucumber plants. PMID:26136764

In-vivo analysis of the uptake process of heavy metals through maize roots by using synchrotron X-ray fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Hwang, Bae Geun; Lee, Sang Joon; Gil, Kyehwan

2016-12-01

The uptake of heavy metals by plants has been receiving much attention for crop contamination and phytoremediation. We employed synchrotron X-ray fluorescence (XRF) spectroscopy for an in-vivo analysis of heavy-metal uptake through a strand of maize root. A focused X-ray beam of 2.5 × 2.5 μm2 in physical dimensions was scanned along horizontal lines of the maize root at intervals of 3 μm at the 4B X-ray micro-diffraction beamline of the Pohang Accelerator Laboratory (PAL). Time-resolved mapping of the fluorescence intensities from multiple metallic elements in the root tissues provided information about the radial distributions of heavy-metal elements and their temporal variations. The concentrated core stream of heavy-metal elements spread radially up to roughly 500 μm, corresponding to 40 % of the root diameter. The absorption characteristics of three heavy metals, Cr, Mn and Ni, and their physiological features were analyzed. The absolute concentrations and the contents of the heavy-metal elements in the tested maize roots were quantitatively evaluated by using the calibration curve obtained from reference samples with preset concentrations. The uptake quantities of the tested heavy-metal elements are noticeably different, although their molecular weights are similar. This study should be helpful for understanding plant physiology related with heavy-metal uptake.

Root-to-shoot Cd translocation via the xylem is the major process determining shoot and grain cadmium accumulation in rice

PubMed Central

Uraguchi, Shimpei; Mori, Shinsuke; Kuramata, Masato; Kawasaki, Akira; Arao, Tomohito; Ishikawa, Satoru

2009-01-01

Physiological properties involved in divergent cadmium (Cd) accumulation among rice genotypes were characterized using the indica cultivar ‘Habataki’ (high Cd in grains) and the japonica cultivar ‘Sasanishiki’ (low Cd in grains). Time-dependence and concentration-dependence of symplastic Cd absorption in roots were revealed not to be responsible for the different Cd accumulation between the two cultivars because root Cd uptake was not greater in the Cd-accumulating cultivar ‘Habataki’ compared with ‘Sasanishiki’. On the other hand, rapid and greater root-to-shoot Cd translocation was observed in ‘Habataki’, which could be mediated by higher abilities in xylem loading of Cd and transpiration rate as a driving force. To verify whether different abilities in xylem-mediated shoot-to-root translocation generally account for the genotypic variation in shoot Cd accumulation in rice, the world rice core collection, consisting of 69 accessions which covers the genetic diversity of almost 32 000 accessions of cultivated rice, was used. The results showed strong correlation between Cd levels in xylem sap and shoots and grains among the 69 rice accessions. Overall, the results presented in this study revealed that the root-to-shoot Cd translocation via the xylem is the major and common physiological process determining the Cd accumulation level in shoots and grains of rice plants. PMID:19401409

Identification of water-deficit responsive genes in maritime pine (Pinus pinaster Ait.) roots.

PubMed

Dubos, Christian; Plomion, Christophe

2003-01-01

Root adaptation to soil environmental factors is very important to maritime pine, the main conifer species used for reforestation in France. The range of climates in the sites where this species is established varies from flooded in winter to drought-prone in summer. No studies have yet focused on the morphological, physiological or molecular variability of the root system to adapt its growth to such an environment. We developed a strategy to isolate drought-responsive genes in the root tissue in order to identify the molecular mechanisms that trees have evolved to cope with drought (the main problem affecting wood productivity), and to exploit this information to improve drought stress tolerance. In order to provide easy access to the root system, seedlings were raised in hydroponic solution. Polyethylene glycol was used as an osmoticum to induce water deficit. Using the cDNA-AFLP technique, we screened more than 2500 transcript derived fragments, of which 33 (1.2%) showed clear variation in presence/absence between non stressed and stressed medium. The relative abundance of these transcripts was then analysed by reverse northern. Only two out of these 33 genes showed significant opposite behaviour between both techniques. The identification and characterization of water-deficit responsive genes in roots provide the emergence of physiological understanding of the patterns of gene expression and regulation involved in the drought stress response of maritime pine.

Articulatory Complexity, Ambient Frequency, and Functional Load as Predictors of Consonant Development in Children

ERIC Educational Resources Information Center

Stokes, Stephanie F.; Surendran, Dinoj

2005-01-01

The notion of a universal pattern of phonological development, rooted in basic physiological constraints, is controversial, with some researchers arguing for a strong environmental (ambient language) influence on phonological development or an interaction of both physiological constraints and ambient language effects. This research examines the…

PLANT CULTURAL SYSTEM FOR MONITORING EVAPOTRANSPIRATION AND PHYSIOLOGICAL RESPONSES UNDER FIELD CONDITIONS

EPA Science Inventory

A plant culture system incorporating the water-table root-screen method for controlling plant water status was adapted for use in open-top field exposure chambers for studying the effects of drought stress on physiological responses. The daily transpiration rates of the plants we...

Adaptive Calibration of Children's Physiological Responses to Family Stress: The Utility of Evolutionary Developmental Theory--Comment on Del Giudice et al. (2012) and Sturge-Apple et al. (2012)

ERIC Educational Resources Information Center

Bugental, Daphne Blunt

2012-01-01

Children's physiological reactions to stress are presented from the broader theoretical perspective of adaptive calibration to the environment, as rooted in life history theory. Del Giudice, Hinnant, Ellis, and El-Sheikh (2012) focus on children's physiological responses to a stressful task as a consequence of their history of family stress.…

Expression of root-related transcription factors associated with flooding tolerance of soybean (Glycine max).

PubMed

Valliyodan, Babu; Van Toai, Tara T; Alves, Jose Donizeti; de Fátima P Goulart, Patricia; Lee, Jeong Dong; Fritschi, Felix B; Rahman, Mohammed Atiqur; Islam, Rafiq; Shannon, J Grover; Nguyen, Henry T

2014-09-29

Much research has been conducted on the changes in gene expression of the model plant Arabidopsis to low-oxygen stress. Flooding results in a low oxygen environment in the root zone. However, there is ample evidence that tolerance to soil flooding is more than tolerance to low oxygen alone. In this study, we investigated the physiological response and differential expression of root-related transcription factors (TFs) associated with the tolerance of soybean plants to soil flooding. Differential responses of PI408105A and S99-2281 plants to ten days of soil flooding were evaluated at physiological, morphological and anatomical levels. Gene expression underlying the tolerance response was investigated using qRT-PCR of root-related TFs, known anaerobic genes, and housekeeping genes. Biomass of flood-sensitive S99-2281 roots remained unchanged during the entire 10 days of flooding. Flood-tolerant PI408105A plants exhibited recovery of root growth after 3 days of flooding. Flooding induced the development of aerenchyma and adventitious roots more rapidly in the flood-tolerant than the flood-sensitive genotype. Roots of tolerant plants also contained more ATP than roots of sensitive plants at the 7th and 10th days of flooding. Quantitative transcript analysis identified 132 genes differentially expressed between the two genotypes at one or more time points of flooding. Expression of genes related to the ethylene biosynthesis pathway and formation of adventitious roots was induced earlier and to higher levels in roots of the flood-tolerant genotype. Three potential flood-tolerance TFs which were differentially expressed between the two genotypes during the entire 10-day flooding duration were identified. This study confirmed the expression of anaerobic genes in response to soil flooding. Additionally, the differential expression of TFs associated with soil flooding tolerance was not qualitative but quantitative and temporal. Functional analyses of these genes will be necessary to reveal their potential to enhance flooding tolerance of soybean cultivars.

Expression of Root-Related Transcription Factors Associated with Flooding Tolerance of Soybean (Glycine max)

PubMed Central

Valliyodan, Babu; Van Toai, Tara T.; Alves, Jose Donizeti; de Fátima P. Goulart, Patricia; Lee, Jeong Dong; Fritschi, Felix B.; Rahman, Mohammed Atiqur; Islam, Rafiq; Shannon, J. Grover; Nguyen, Henry T.

2014-01-01

Much research has been conducted on the changes in gene expression of the model plant Arabidopsis to low-oxygen stress. Flooding results in a low oxygen environment in the root zone. However, there is ample evidence that tolerance to soil flooding is more than tolerance to low oxygen alone. In this study, we investigated the physiological response and differential expression of root-related transcription factors (TFs) associated with the tolerance of soybean plants to soil flooding. Differential responses of PI408105A and S99-2281 plants to ten days of soil flooding were evaluated at physiological, morphological and anatomical levels. Gene expression underlying the tolerance response was investigated using qRT-PCR of root-related TFs, known anaerobic genes, and housekeeping genes. Biomass of flood-sensitive S99-2281 roots remained unchanged during the entire 10 days of flooding. Flood-tolerant PI408105A plants exhibited recovery of root growth after 3 days of flooding. Flooding induced the development of aerenchyma and adventitious roots more rapidly in the flood-tolerant than the flood-sensitive genotype. Roots of tolerant plants also contained more ATP than roots of sensitive plants at the 7th and 10th days of flooding. Quantitative transcript analysis identified 132 genes differentially expressed between the two genotypes at one or more time points of flooding. Expression of genes related to the ethylene biosynthesis pathway and formation of adventitious roots was induced earlier and to higher levels in roots of the flood-tolerant genotype. Three potential flood-tolerance TFs which were differentially expressed between the two genotypes during the entire 10-day flooding duration were identified. This study confirmed the expression of anaerobic genes in response to soil flooding. Additionally, the differential expression of TFs associated with soil flooding tolerance was not qualitative but quantitative and temporal. Functional analyses of these genes will be necessary to reveal their potential to enhance flooding tolerance of soybean cultivars. PMID:25268626

Influence of different irrigation levels on the root water uptake and the physiology of root-chicory

NASA Astrophysics Data System (ADS)

Vandoorne, B.; Dekoninck, N.; Lutts, S.; Capelle, B.; Javaux, M.

2009-04-01

In the context of global warming and given recent heat waves observed in Western Europe, the relationship between the soil water status and the plant health has recently received more attention, especially for cash crops like chicory. In this study we particularly investigated the impact of soil water status on the chicory root water uptake and density and made a link with physiological and yield parameters. During five months, we imposed different irrigation levels to 10 plants of chicory (Cichorium intybus var. sativum) growing in greenhouses. Each seed, coming from an autogamous selection in this allogamous species, was sown in a column of 1.42m height and 0.4m diameter filled with yellow sand and irrigated from the bottom with Hoagland solution. On those 10 columns, we measured the distribution of soil moisture with TDR (8 columns) and ERT (2 columns) probes. Lateral windows also allowed us to follow the root growth. The column weights were also monitored in order to quantify the plant transpiration. During the experiment, several physiological indices were also followed like the gas exchange (CO2 and transpiration), the chlorophyll fluorescence, the stomatal conductance, the plastochron, and the Leaf Area Index (LAI). At the end of the experiment, the complete root length density and the water content profiles were measured. We had also a look to the osmotic potential, the pigments content and the isotopic discrimination of carbon in the leaves, which gives information about the level of stress. At a biochemical point of view, we measured the content in enzymes involves in inulin metabolism and sugars synthesis. We observed that the plants suffering from a slight water stress developed better. A simple1-D model was built which describes the root growth in function of the irrigation level and of the soil and atmospheric boundary conditions.

The Plant as Metaorganism and Research on Next-Generation Systemic Pesticides – Prospects and Challenges

PubMed Central

Vryzas, Zisis

2016-01-01

Systemic pesticides (SPs) are usually recommended for soil treatments and as seed coating agents and are taken up from the soil by involving various plant-mediated processes, physiological, and morphological attributes of the root systems. Microscopic insights and next-generation sequencing combined with bioinformatics allow us now to identify new functions and interactions of plant-associated bacteria and perceive plants as meta-organisms. Host symbiotic, rhizo-epiphytic, endophytic microorganisms and their functions on plants have not been studied yet in accordance with uptake, tanslocation and action of pesticides. Root tips exudates mediated by rhizobacteria could modify the uptake of specific pesticides while bacterial ligands and enzymes can affect metabolism and fate of pesticide within plant. Over expression of specific proteins in cell membrane can also modify pesticide influx in roots. Moreover, proteins and other membrane compartments are usually involved in pesticide modes of action and resistance development. In this article it is discussed what is known of the physiological attributes including apoplastic, symplastic, and trans-membrane transport of SPs in accordance with the intercommunication dictated by plant–microbe, cell to cell and intracellular signaling. Prospects and challenges for uptake, translocation, storage, exudation, metabolism, and action of SPs are given through the prism of new insights of plant microbiome. Interactions of soil applied pesticides with physiological processes, plant root exudates and plant microbiome are summarized to scrutinize challenges for the next-generation pesticides. PMID:28018306

Phytotoxicity of glyphosate in the germination of Pisum sativum and its effect on germinated seedlings

PubMed Central

2017-01-01

The present study evaluated the effects of glyphosate on Pisum sativum germination as well as its effect on the physiology and biochemistry of germinated seedlings. Different physico-chemical biomarkers, viz., chlorophyll, root and shoot length, total protein and soluble sugar, along with sodium and potassium concentration, were investigated in germinated seedlings at different glyphosate concentrations. This study reports the influence of different concentrations of glyphosate on pea seeds and seedlings. Physicochemical biomarkers were significantly changed by glyphosate exposure after 15 days. The germination of seedlings under control conditions (0 mg/L) was 100% after 3 days of treatment but at 3 and 4 mg/L glyphosate, germination was reduced to 55 and 40%, respectively. Physiological parameters like root and shoot length decreased monotonically with increasing glyphosate concentration, at 14 days of observation. Average root and shoot length (n=30 in three replicates) were reduced to 14.7 and 17.6%, respectively, at 4 mg/L glyphosate. Leaf chlorophyll content also decreased, with a similar trend to root and shoot length, but the protein content initially decreased and then increased with an increase in glyphosate concentration to 3 mg/L. The study suggests that glyphosate reduces the soluble sugar content significantly, by 21.6% (v/v). But internal sodium and potassium tissue concentrations were significantly altered by glyphosate exposure with increasing concentrations of glyphosate. Biochemical and physiological analysis also supports the inhibitory effect of glyphosate on seed germination and biochemical effects on seedlings. PMID:28728354

Adaptive biochemical and physiological responses of Eriobotrya japonica to fluoride air pollution.

PubMed

Elloumi, Nada; Zouari, Mohamed; Mezghani, Imed; Ben Abdallah, Ferjani; Woodward, Steve; Kallel, Monem

2017-09-01

The biochemical and physiological effects of fluoride were investigated in loquat trees (Eriobotrya japonica) grown in the vicinity of a phosphate fertilizer plant in Tunisia. Photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (E), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities were assessed; along with photosynthetic pigments, lipid peroxidation, electrolytic leakage (EL) and total phenolic contents in foliage and roots of trees at different distances from the phosphate fertilizer plant. All assessed parameters showed significant discrepancies in comparison with unpolluted sites. Obtained results showed high oxidative stress indices including H 2 O 2 , lipid peroxidation, and EL, SOD, CAT and GPx activities and proline contents in leaves and roots at the polluted sites as compared to control. In contrast, leaf Pn, Gs, E and photosynthetic pigment contents were low as compared to the control. These results indicate that even though antioxidant responses increased near the factory, adverse effects on physiology were pronounced.

Water use patterns of co-occurring C3 and C4 shrubs in the Gurbantonggut desert in northwestern China.

PubMed

Tiemuerbieke, Bahejiayinaer; Min, Xiao-Jun; Zang, Yong-Xin; Xing, Peng; Ma, Jian-Ying; Sun, Wei

2018-09-01

In water-limited ecosystems, spatial and temporal partitioning of water sources is an important mechanism that facilitates plant survival and lessens the competition intensity of co-existing plants. Insights into species-specific root functional plasticity and differences in the water sources of co-existing plants under changing water conditions can aid in accurate prediction of the response of desert ecosystems to future climate change. We used stable isotopes of soil water, groundwater and xylem water to determine the seasonal and inter- and intraspecific differences variations in the water sources of six C 3 and C 4 shrubs in the Gurbantonggut desert. We also measured the stem water potentials to determine the water stress levels of each species under varying water conditions. The studied shrubs exhibited similar seasonal water uptake patterns, i.e., all shrubs extracted shallow soil water recharged by snowmelt water during early spring and reverted to deeper water sources during dry summer periods, indicating that all of the studied shrubs have dimorphic root systems that enable them to obtain water sources that differ in space and time. Species in the C 4 shrub community exhibited differences in seasonal water absorption and water status due to differences in topography and rooting depth, demonstrating divergent adaptations to water availability and water stress. Haloxylon ammodendron and T. ramosissima in the C 3 /C 4 mixed community were similar in terms of seasonal water extraction but differed with respect to water potential, which indicated that plant water status is controlled by both root functioning and shoot eco-physiological traits. The two Tamarix species in the C 3 shrub community were similar in terms of water uptake and water status, which suggests functional convergence of the root system and physiological performance under same soil water conditions. In different communities, Haloxylon ammodendron differed in terms of summer water extraction, which suggests that this species exhibits plasticity with respect to rooting depth under different soil water conditions. Shrubs in the Gurbantonggut desert displayed varying adaptations across species and communities through divergent root functioning and shoot eco-physiological traits. Copyright © 2018 Elsevier B.V. All rights reserved.

[Response of fine roots to soil nutrient spatial heterogeneity].

PubMed

Wang, Qingcheng; Cheng, Yunhuan

2004-06-01

The spatial heterogeneity is the complexity and variation of systems or their attributes, and the heterogeneity of soil nutrients is ubiquitous in all natural ecosystems. The scale of spatial heterogeneity varies considerably among different ecosystems, from tens of centimeters to hundred meters. Some of the scales can be detected by individual plant. Because the growth of individual plants can be strongly influenced by soil heterogeneity, it follows that the inter-specific competition should also be affected. During the long process of evolution, plants developed various plastic responses with their root system, including morphological, physiological and mycorrhizal plasticity, to maximize the nutrient acquisition from heterogeneous soil resources. Morphological plasticity, an adjustment in root system spatial allocation and architecture in response to spatial heterogeneous distribution of available soil resources, has been most intensively studied, and root proliferation in nutrient rich patches has been certified for many species. The species that do respond may have an increased rate of nutrient uptake, leading to a competitive advantage. Scale and precision are two important features employed in describing the size and foraging behavior of root system. It was hypothesized that scale and precision is negatively related, i. e., the species with high scale of root system tend to be a less precise forager. The outcomes of different research work have been diverse, far from reaching a consensus. Species with high scale are not necessarily less precise in fine root allocation, and vice versa. The proliferation of fine root in enriched micro-sites is species dependent, and also affected by other factors, such as patch attributes (size and nutrients concentration), nutrients, and overall soil fertility. Beside root proliferation in nutrient enriched patches, plants can also adapt themselves to the heterogeneous soil environment by altering other root characteristics such as fine root diameter, branch angle, length, and spatial architecture of root system. Physiological and mycorrhizal plasticity can add some influence on the morphological plasticity to some extent, but they are less studied. Roots located in different patches can quickly regulate their nutrient uptake kinetics within different nutrient patches, and increase overall nutrient uptake. Physiological response may, to certain extent, reduce morphological response, and is meaningful for plant growth on soils with frequently changing spatial and temporal heterogeneity. Mycorrhizal plasticity has been least studied so far. Some researches revealed that mycorrhiza, rather than fine root, proliferated in enriched patches. But, it is not the case with other studies. The proliferation of mycorrhiza within enriched patches is more profitable in term of carbon invest. The effect of fine root proliferation on nutrient uptake is complex, depending on ion mobility and whether or not neighboring plant exists. The influence of root plasticity on the growth of plants is species specific. Some species (sensitive species) gain growth benefit, while others don't. The ability of an individual plant to response to heterogeneous resources has significant effect on its competitive ability and its fate within the community, and eventually shapes the composition and structure of the community.

UV-B Radiation Induces Root Bending Through the Flavonoid-Mediated Auxin Pathway in Arabidopsis.

PubMed

Wan, Jinpeng; Zhang, Ping; Wang, Ruling; Sun, Liangliang; Wang, Wenying; Zhou, Huakun; Xu, Jin

2018-01-01

Ultraviolet (UV)-B radiation-induced root bending has been reported; however, the underlying mechanisms largely remain unclear. Here, we investigate whether and how auxin and flavonoids are involved in UV-B radiation-induced root bending in Arabidopsis using physiological, pharmacological, and genetic approaches. UV-B radiation modulated the direction of root growth by decreasing IAA biosynthesis and affecting auxin distribution in the root tips, where reduced auxin accumulation and asymmetric auxin distribution were observed. UV-B radiation increased the distribution of auxin on the nonradiated side of the root tips, promoting growth and causing root bending. Further analysis indicated that UV-B induced an asymmetric accumulation of flavonoids; this pathway is involved in modulating the accumulation and asymmetric distribution of auxin in root tips and the subsequent redirection of root growth by altering the distribution of auxin carriers in response to UV-B radiation. Taken together, our results indicate that UV-B radiation-induced root bending occurred through a flavonoid-mediated phototropic response to UV-B radiation.

UV-B Radiation Induces Root Bending Through the Flavonoid-Mediated Auxin Pathway in Arabidopsis

PubMed Central

Wan, Jinpeng; Zhang, Ping; Wang, Ruling; Sun, Liangliang; Wang, Wenying; Zhou, Huakun; Xu, Jin

2018-01-01

Ultraviolet (UV)-B radiation-induced root bending has been reported; however, the underlying mechanisms largely remain unclear. Here, we investigate whether and how auxin and flavonoids are involved in UV-B radiation-induced root bending in Arabidopsis using physiological, pharmacological, and genetic approaches. UV-B radiation modulated the direction of root growth by decreasing IAA biosynthesis and affecting auxin distribution in the root tips, where reduced auxin accumulation and asymmetric auxin distribution were observed. UV-B radiation increased the distribution of auxin on the nonradiated side of the root tips, promoting growth and causing root bending. Further analysis indicated that UV-B induced an asymmetric accumulation of flavonoids; this pathway is involved in modulating the accumulation and asymmetric distribution of auxin in root tips and the subsequent redirection of root growth by altering the distribution of auxin carriers in response to UV-B radiation. Taken together, our results indicate that UV-B radiation-induced root bending occurred through a flavonoid-mediated phototropic response to UV-B radiation. PMID:29868074

Seasonal Fine Root Carbohydrate Relations of Plantation Loblolly Pine After Thinning

Treesearch

Mary A. Sword; Eric A. Kuehler; Zhenmin Tang

2000-01-01

Loblolly pine (Pinus taeda L.) occurs naturally on soils that are frequently low in fertility and water availability (Allen et al., 1990; Schultz 1997). Despite these limitations, this species maintains a high level of productivity on most sites (Schultz, 1997). Knowledge of plantation loblolly pine root system growth and physiology is needed to...

Familiarity with Latin and Greek Anatomical Terms and Course Performance in Undergraduates

ERIC Educational Resources Information Center

Pampush, James D.; Petto, Andrew J.

2011-01-01

Commonly used technical anatomy and physiology (A&P) terms are predominantly rooted in Latin and Greek vocabulary, so it is commonly inferred that a solid grounding in Latin and Greek roots of medical terminology will improve student learning in anatomy and related disciplines. This study examines the association of etymological knowledge of…

Effect of Salinity on Biomass Yield and Physiological and Stem-Root Anatomical Characteristics of Purslane (Portulaca oleracea L.) Accessions

PubMed Central

Juraimi, Abdul Shukor; Rafii, M. Y.; Abdul Hamid, Azizah

2015-01-01

13 selected purslane accessions were subjected to five salinity levels 0, 8, 16, 24, and 32 dS m−1. Salinity effect was evaluated on the basis of biomass yield reduction, physiological attributes, and stem-root anatomical changes. Aggravated salinity stress caused significant (P < 0.05) reduction in all measured parameters and the highest salinity showed more detrimental effect compared to control as well as lower salinity levels. The fresh and dry matter production was found to increase in Ac1, Ac9, and Ac13 from lower to higher salinity levels but others were badly affected. Considering salinity effect on purslane physiology, increase in chlorophyll content was seen in Ac2, Ac4, Ac6, and Ac8 at 16 dS m−1 salinity, whereas Ac4, Ac9, and Ac12 showed increased photosynthesis at the same salinity levels compared to control. Anatomically, stem cortical tissues of Ac5, Ac9, and Ac12 were unaffected at control and 8 dS m−1 salinity but root cortical tissues did not show any significant damage except a bit enlargement in Ac12 and Ac13. A dendrogram was constructed by UPGMA based on biomass yield and physiological traits where all 13 accessions were grouped into 5 clusters proving greater diversity among them. The 3-dimensional principal component analysis (PCA) has also confirmed the output of grouping from cluster analysis. Overall, salinity stressed among all 13 purslane accessions considering biomass production, physiological growth, and anatomical development Ac9 was the best salt-tolerant purslane accession and Ac13 was the most affected accession. PMID:25802833

RNAi inhibition of feruloyl CoA 6'-hydroxylase reduces scopoletin biosynthesis and post-harvest physiological deterioration in cassava (Manihot esculenta Crantz) storage roots.

PubMed

Liu, Shi; Zainuddin, Ima M; Vanderschuren, Herve; Doughty, James; Beeching, John R

2017-05-01

Cassava (Manihot esculenta Crantz) is a major world crop, whose storage roots provide food for over 800 million throughout the humid tropics. Despite many advantages as a crop, the development of cassava is seriously constrained by the rapid post-harvest physiological deterioration (PPD) of its roots that occurs within 24-72 h of harvest, rendering the roots unpalatable and unmarketable. PPD limits cassava's marketing possibilities in countries that are undergoing increased development and urbanisation due to growing distances between farms and consumers. The inevitable wounding of the roots caused by harvesting triggers an oxidative burst that spreads throughout the cassava root, together with the accumulation of secondary metabolites including phenolic compounds, of which the coumarin scopoletin (7-hydroxy-6-methoxy-2H-1-benzopyran-2-one) is the most abundant. Scopoletin oxidation yields a blue-black colour, which suggests its involvement in the discoloration observed during PPD. Feruloyl CoA 6'-hydroxylase is a controlling enzyme in the biosynthesis of scopoletin. The cassava genome contains a seven membered family of feruloyl CoA 6'-hydroxylase genes, four of which are expressed in the storage root and, of these, three were capable of functionally complementing Arabidopsis T-DNA insertion mutants in this gene. A RNA interference construct, designed to a highly conserved region of these genes, was used to transform cassava, where it significantly reduced feruloyl CoA 6'-hydroxylase gene expression, scopoletin accumulation and PPD symptom development. Collectively, our results provide evidence that scopoletin plays a major functional role in the development of PPD symptoms, rather than merely paralleling symptom development in the cassava storage root.

Short-term effects of fertilization on loblolly pine (Pinus taeda L.) physiology

Treesearch

C.M. Gough; J.R. Seiler; Chris A. Maier

2004-01-01

Fertilization commonly increases biomass production in loblolly pine (Pinus taeda L.). However, the sequence of short-term physiological adjustments allowing for the establishment of leaf area and enhanced growth is not well understood. The effects of fertilization on photosynthetic parameters, root respiration, and growth for over 200 d following...

Early steps of adventitious rooting: morphology, hormonal profiling and carbohydrate turnover in carnation stem cuttings.

PubMed

Agulló-Antón, María Ángeles; Ferrández-Ayela, Almudena; Fernández-García, Nieves; Nicolás, Carlos; Albacete, Alfonso; Pérez-Alfocea, Francisco; Sánchez-Bravo, José; Pérez-Pérez, José Manuel; Acosta, Manuel

2014-03-01

The rooting of stem cuttings is a common vegetative propagation practice in many ornamental species. A detailed analysis of the morphological changes occurring in the basal region of cultivated carnation cuttings during the early stages of adventitious rooting was carried out and the physiological modifications induced by exogenous auxin application were studied. To this end, the endogenous concentrations of five major classes of plant hormones [auxin, cytokinin (CK), abscisic acid, salicylic acid (SA) and jasmonic acid] and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid were analyzed at the base of stem cuttings and at different stages of adventitious root formation. We found that the stimulus triggering the initiation of adventitious root formation occurred during the first hours after their excision from the donor plant, due to the breakdown of the vascular continuum that induces auxin accumulation near the wounding. Although this stimulus was independent of exogenously applied auxin, it was observed that the auxin treatment accelerated cell division in the cambium and increased the sucrolytic activities at the base of the stem, both of which contributed to the establishment of the new root primordia at the stem base. Further, several genes involved in auxin transport were upregulated in the stem base either with or without auxin application, while endogenous CK and SA concentrations were specially affected by exogenous auxin application. Taken together our results indicate significant crosstalk between auxin levels, stress hormone homeostasis and sugar availability in the base of the stem cuttings in carnation during the initial steps of adventitious rooting. © 2013 Scandinavian Plant Physiology Society.

Arbuscular mycorrhizal symbiosis can mitigate the negative effects of night warming on physiological traits of Medicago truncatula L.

PubMed

Hu, Yajun; Wu, Songlin; Sun, Yuqing; Li, Tao; Zhang, Xin; Chen, Caiyan; Lin, Ge; Chen, Baodong

2015-02-01

Elevated night temperature, one of the main climate warming scenarios, can have profound effects on plant growth and metabolism. However, little attention has been paid to the potential role of mycorrhizal associations in plant responses to night warming, although it is well known that symbiotic fungi can protect host plants against various environmental stresses. In the present study, physiological traits of Medicago truncatula L. in association with the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis were investigated under simulated night warming. A constant increase in night temperature of 1.53 °C significantly reduced plant shoot and root biomass, flower and seed number, leaf sugar concentration, and shoot Zn and root P concentrations. However, the AM association essentially mitigated these negative effects of night warming by improving plant growth, especially through increased root biomass, root to shoot ratio, and shoot Zn and root P concentrations. A significant interaction was observed between R. irregularis inoculation and night warming in influencing both root sucrose concentration and expression of sucrose synthase (SusS) genes, suggesting that AM symbiosis and increased night temperature jointly regulated plant sugar metabolism. Night warming stimulated AM fungal colonization but did not influence arbuscule abundance, symbiosis-related plant or fungal gene expression, or growth of extraradical mycelium, indicating little effect of night warming on the development or functioning of AM symbiosis. These findings highlight the importance of mycorrhizal symbiosis in assisting plant resilience to climate warming.

How tree roots respond to drought

PubMed Central

Brunner, Ivano; Herzog, Claude; Dawes, Melissa A.; Arend, Matthias; Sperisen, Christoph

2015-01-01

The ongoing climate change is characterized by increased temperatures and altered precipitation patterns. In addition, there has been an increase in both the frequency and intensity of extreme climatic events such as drought. Episodes of drought induce a series of interconnected effects, all of which have the potential to alter the carbon balance of forest ecosystems profoundly at different scales of plant organization and ecosystem functioning. During recent years, considerable progress has been made in the understanding of how aboveground parts of trees respond to drought and how these responses affect carbon assimilation. In contrast, processes of belowground parts are relatively underrepresented in research on climate change. In this review, we describe current knowledge about responses of tree roots to drought. Tree roots are capable of responding to drought through a variety of strategies that enable them to avoid and tolerate stress. Responses include root biomass adjustments, anatomical alterations, and physiological acclimations. The molecular mechanisms underlying these responses are characterized to some extent, and involve stress signaling and the induction of numerous genes, leading to the activation of tolerance pathways. In addition, mycorrhizas seem to play important protective roles. The current knowledge compiled in this review supports the view that tree roots are well equipped to withstand drought situations and maintain morphological and physiological functions as long as possible. Further, the reviewed literature demonstrates the important role of tree roots in the functioning of forest ecosystems and highlights the need for more research in this emerging field. PMID:26284083

Nitric Oxide Inhibits Al-Induced Programmed Cell Death in Root Tips of Peanut (Arachis hypogaea L.) by Affecting Physiological Properties of Antioxidants Systems and Cell Wall

PubMed Central

Pan, Chun-Liu; Yao, Shao-Chang; Xiong, Wei-Jiao; Luo, Shu-Zhen; Wang, Ya-Lun; Wang, Ai-Qin; Xiao, Dong; Zhan, Jie; He, Long-Fei

2017-01-01

It has been reported that nitric oxide (NO) is a negative regulator of aluminum (Al)-induced programmed cell death (PCD) in peanut root tips. However, the inhibiting mechanism of NO on Al-induced PCD is unclear. In order to investigate the mechanism by which NO inhibits Al-induced PCD, the effects of co-treatment Al with the exogenous NO donor or the NO-specific scavenger on peanut root tips, the physiological properties of antioxidants systems and cell wall (CW) in root tip cells of NO inhibiting Al-induced PCD were studied with two peanut cultivars. The results showed that Al exposure induced endogenous NO accumulation, and endogenous NO burst increased antioxidant enzyme activity in response to Al stress. The addition of NO donor sodium nitroprusside (SNP) relieved Al-induced root elongation inhibition, cell death and Al adsorption in CW, as well as oxidative damage and ROS accumulation. Furthermore, co-treatment with the exogenous NO donor decreased MDA content, LOX activity and pectin methylesterase (PME) activity, increased xyloglucan endotransglucosylase (XET) activity and relative expression of the xyloglucan endotransglucosylase/hydrolase (XTH-32) gene. Taken together, exogenous NO alleviated Al-induced PCD by inhibiting Al adsorption in CW, enhancing antioxidant defense and reducing peroxidation of membrane lipids, alleviating the inhibition of Al on root elongation by maintaining the extensibility of CW, decreasing PME activity, and increasing XET activity and relative XTH-32 expression of CW. PMID:29311970

Nitric Oxide Inhibits Al-Induced Programmed Cell Death in Root Tips of Peanut (Arachis hypogaea L.) by Affecting Physiological Properties of Antioxidants Systems and Cell Wall.

PubMed

Pan, Chun-Liu; Yao, Shao-Chang; Xiong, Wei-Jiao; Luo, Shu-Zhen; Wang, Ya-Lun; Wang, Ai-Qin; Xiao, Dong; Zhan, Jie; He, Long-Fei

2017-01-01

It has been reported that nitric oxide (NO) is a negative regulator of aluminum (Al)-induced programmed cell death (PCD) in peanut root tips. However, the inhibiting mechanism of NO on Al-induced PCD is unclear. In order to investigate the mechanism by which NO inhibits Al-induced PCD, the effects of co-treatment Al with the exogenous NO donor or the NO-specific scavenger on peanut root tips, the physiological properties of antioxidants systems and cell wall (CW) in root tip cells of NO inhibiting Al-induced PCD were studied with two peanut cultivars. The results showed that Al exposure induced endogenous NO accumulation, and endogenous NO burst increased antioxidant enzyme activity in response to Al stress. The addition of NO donor sodium nitroprusside (SNP) relieved Al-induced root elongation inhibition, cell death and Al adsorption in CW, as well as oxidative damage and ROS accumulation. Furthermore, co-treatment with the exogenous NO donor decreased MDA content, LOX activity and pectin methylesterase (PME) activity, increased xyloglucan endotransglucosylase (XET) activity and relative expression of the xyloglucan endotransglucosylase/hydrolase ( XTH-32 ) gene. Taken together, exogenous NO alleviated Al-induced PCD by inhibiting Al adsorption in CW, enhancing antioxidant defense and reducing peroxidation of membrane lipids, alleviating the inhibition of Al on root elongation by maintaining the extensibility of CW, decreasing PME activity, and increasing XET activity and relative XTH-32 expression of CW.

[Effects of different application rates of water-retaining agent on root physiological characteristics of winter wheat at its different growth stages].

PubMed

Yang, Yong-Hui; Wu, Ji-Cheng; Wu, Pu-Te; Huang, Zhan-Bin; Zhao, Xi-Ning; Guan, Xiu-Juan; He, Fang

2011-01-01

A field experiment was conducted at the Yuzhou Experimental Base of Henan Province to study the effects of different application rates (0, 30, 60, and 90 kg x hm(-2)) of water-retaining agent (WRA) on the root physiological characteristics, biomass, and grain yield of two winter wheat cultivars Zhengmai-9694 and Aikang-58, aimed to probe into the action mechanisms of WRA on the root system of winter wheat at its different growth stages. The application of WRA decreased the root membrane permeability and soluble sugar content, and increased the root vigor. After the application of WRA, the Zhengmai-9694 at its different growth stages had a greater decrement of root membrane permeability, compared with Aikang-58. In all treatments except 90 kg x hm(-2) of WRA, the root vigor of Aikang-58 was obviously higher than that of Zhengmai-9694. At booting and grain-filling stages, the root soluble sugar content of Zhengmai-9694 decreased much more than that of Aikang-58. In the whole growth period of the two cultivars, their root membrane permeability and soluble sugar content were the lowest in treatment 60 kg x hm(-2) of WRA, and no significant differences were observed between treatments 60 and 90 kg x hm(-2) of WRA. The root vigor of Zhengmai-9694 increased remarkably with the increasing rate of WRA application, while that of Aikang-58 was the highest in treatment 60 kg x hm(-2) of WRA. The application of WRA also increased root biomass, and at jointing and booting stages, the root biomass of Aikang-58 was much higher than that of Zhengmai-9694. However, at grain-filling stage, the biomass of Aikang-58 in treatments 60 and 90 kg x hm(-2) of WRA was lower than that of Zhengmai-9694. Treatment 60 kg x hm(-2) of WRA had the highest grain yield of the two cultivars. It was concluded that WRA had more significant effects on Zhengmai-9694 than on Aikang-58, and applying 60 kg x hm(-2) of WRA could obtain the best effect.

Accumulation of cadmium, zinc, and copper by Helianthus annuus L.: impact on plant growth and uptake of nutritional elements.

PubMed

Rivelli, Anna Rita; De Maria, Susanna; Puschenreiter, Markus; Gherbin, Piergiorgio

2012-04-01

We investigated the effects on physiological response, trace elements and nutrients accumulation of sunflower plants grown in soil contaminated with: 5 mg kg(-1) of Cd; 5 and 300 mg kg(-1) of Cd and Zn, respectively; 5, 300, and 400 mg kg(-1) of Cd, Zn, and Cu, respectively. Contaminants applied did not produce large effects on growth, except in Cd-Zn-Cu treatment in which leaf area and total dry matter were reduced, by 15%. The contamination with Cd alone did not affect neither growth nor physiological parameters, despite considerable amounts of Cd accumulated in roots and older leaves, with a high bioconcentration factor from soil to plant. By adding Zn and then Cu to Cd in soil, significant were the toxic effects on chlorophyll content and water relations due to greater accumulation of trace elements in tissues, with imbalances in nutrients uptake. Highly significant was the interaction between shoot elements concentration (Cd, Zn, Cu, Fe, Mg, K, Ca) and treatments. Heavy metals concentrations in roots always exceeded those in stem and leaves, with a lower translocation from roots to shoots, suggesting a strategy of sunflower to compartmentalise the potentially toxic elements in physiologically less active parts in order to preserve younger tissues.

Lead tolerance of water hyacinth (Eichhornia crassipes Mart. - Pontederiaceae) as defined by anatomical and physiological traits.

PubMed

Pereira, Fabricio J; Castro, Evaristo M de; Oliveira, Cynthia de; Pires, Marinês F; Pereira, Marcio P; Ramos, Silvio J; Faquin, Valdemar

2014-09-01

This study aimed at verifying the lead tolerance of water hyacinth and at looking at consequent anatomical and physiological modifications. Water hyacinth plants were grown on nutrient solutions with five different lead concentrations: 0.00, 0.50, 1.00, 2.00 and 4.00 mg L-1 by 20 days. Photosynthesis, transpiration, stomatal conductance and the Ci/Ca rate were measured at the end of 15 days of experiment. At the end of the experiment, the anatomical modifications in the roots and leaves, and the activity of antioxidant system enzymes, were evaluated. Photosynthetic and Ci/Ca rates were both increased under all lead treatments. Leaf anatomy did not exhibit any evidence of toxicity effects, but showed modifications of the stomata and in the thickness of the palisade and spongy parenchyma in the presence of lead. Likewise, root anatomy did not exhibit any toxicity effects, but the xylem and phloem exhibited favorable modifications as well as increased apoplastic barriers. All antioxidant system enzymes exhibited increased activity in the leaves, and some modifications in roots, in the presence of lead. It is likely, therefore, that water hyacinth tolerance to lead is related to anatomical and physiological modifications such as increased photosynthesis and enhanced anatomical capacity for CO2 assimilation and water conductance.

Unraveling the role of dark septate endophyte (DSE) colonizing maize (Zea mays) under cadmium stress: physiological, cytological and genic aspects.

PubMed

Wang, Jun-ling; Li, Tao; Liu, Gao-yuan; Smith, Joshua M; Zhao, Zhi-wei

2016-02-25

A growing body of evidence suggests that plant root-associated fungi such as dark septate endophytes (DSE) can help plants overcome many biotic and abiotic stresses, of great interest is DSE-plant metal tolerance and alleviation capabilities on contaminated soils. However, the tolerance and alleviation mechanisms involved have not yet been elucidated. In the current study, the regulation and physiological response of Zea mays to its root-associated DSE, Exophiala pisciphila was analyzed under increased soil Cd stress (0, 10, 50, 100 mg kg(-1)). Under Cd stress, DSE inoculation significantly enhanced the activities of antioxidant enzymes and low-molecular weight antioxidants, while also inducing increased Cd accumulation in the cell wall and conversion of Cd into inactive forms by shoot and root specific regulation of genes related to metal uptake, translocation and chelation. Our results showed that DSE colonization resulted in a marked tolerance to Cd, with a significant decrease in cadmium phytotoxicity and a significant increase in maize growth by triggering antioxidant systems, altering metal chemical forms into inactive Cd, and repartitioning subcellular Cd into the cell wall. These results provide comprehensive evidence for the mechanisms by which DSE colonization bioaugments Cd tolerance in maize at physiological, cytological and molecular levels.

Physiological response and sulfur metabolism of the V. dahliae-infected tomato plants in tomato/potato onion companion cropping

PubMed Central

Fu, Xuepeng; Li, Chunxia; Zhou, Xingang; Liu, Shouwei; Wu, Fengzhi

2016-01-01

Companion cropping with potato onions (Allium cepa var. agrogatum Don.) can enhance the disease resistance of tomato plants (Solanum lycopersicum) to Verticillium dahliae infection by increasing the expressions of genes related to disease resistance. However, it is not clear how tomato plants physiologically respond to V. dahliae infection and what roles sulfur plays in the disease-resistance. Pot experiments were performed to examine changes in the physiology and sulfur metabolism of tomato roots infected by V. dahliae under the companion cropping (tomato/potato onion). The results showed that the companion cropping increased the content of total phenol, lignin and glutathione and increased the activities of peroxidase, polyphenol oxidase and phenylalanine ammonia lyase in the roots of tomato plants. RNA-seq analysis showed that the expressions of genes involved in sulfur uptake and assimilation, and the formation of sulfur-containing defense compounds (SDCs) were up-regulated in the V. dahlia-infected tomatoes in the companion cropping. In addition, the interactions among tomato, potato onion and V. dahliae induced the expression of the high- affinity sulfate transporter gene in the tomato roots. These results suggest that sulfur may play important roles in tomato disease resistance against V. dahliae. PMID:27808257

Unraveling the role of dark septate endophyte (DSE) colonizing maize (Zea mays) under cadmium stress: physiological, cytological and genic aspects

NASA Astrophysics Data System (ADS)

Wang, Jun-Ling; Li, Tao; Liu, Gao-Yuan; Smith, Joshua M.; Zhao, Zhi-Wei

2016-02-01

A growing body of evidence suggests that plant root-associated fungi such as dark septate endophytes (DSE) can help plants overcome many biotic and abiotic stresses, of great interest is DSE-plant metal tolerance and alleviation capabilities on contaminated soils. However, the tolerance and alleviation mechanisms involved have not yet been elucidated. In the current study, the regulation and physiological response of Zea mays to its root-associated DSE, Exophiala pisciphila was analyzed under increased soil Cd stress (0, 10, 50, 100 mg kg-1). Under Cd stress, DSE inoculation significantly enhanced the activities of antioxidant enzymes and low-molecular weight antioxidants, while also inducing increased Cd accumulation in the cell wall and conversion of Cd into inactive forms by shoot and root specific regulation of genes related to metal uptake, translocation and chelation. Our results showed that DSE colonization resulted in a marked tolerance to Cd, with a significant decrease in cadmium phytotoxicity and a significant increase in maize growth by triggering antioxidant systems, altering metal chemical forms into inactive Cd, and repartitioning subcellular Cd into the cell wall. These results provide comprehensive evidence for the mechanisms by which DSE colonization bioaugments Cd tolerance in maize at physiological, cytological and molecular levels.

Opposite metabolic responses of shoots and roots to drought

NASA Astrophysics Data System (ADS)

Gargallo-Garriga, Albert; Sardans, Jordi; Pérez-Trujillo, Míriam; Rivas-Ubach, Albert; Oravec, Michal; Vecerova, Kristyna; Urban, Otmar; Jentsch, Anke; Kreyling, Juergen; Beierkuhnlein, Carl; Parella, Teodor; Peñuelas, Josep

2014-10-01

Shoots and roots are autotrophic and heterotrophic organs of plants with different physiological functions. Do they have different metabolomes? Do their metabolisms respond differently to environmental changes such as drought? We used metabolomics and elemental analyses to answer these questions. First, we show that shoots and roots have different metabolomes and nutrient and elemental stoichiometries. Second, we show that the shoot metabolome is much more variable among species and seasons than is the root metabolome. Third, we show that the metabolic response of shoots to drought contrasts with that of roots; shoots decrease their growth metabolism (lower concentrations of sugars, amino acids, nucleosides, N, P, and K), and roots increase it in a mirrored response. Shoots are metabolically deactivated during drought to reduce the consumption of water and nutrients, whereas roots are metabolically activated to enhance the uptake of water and nutrients, together buffering the effects of drought, at least at the short term.

Osmotic and elastic adjustments in cold desert shrubs differing in rooting depth: coping with drought and subzero temperatures

Treesearch

Fabian G. Scholz; Sandra J. Bucci; Nadia Arias; Frederick C. Meinzer; Guillermo Goldstein

2012-01-01

Physiological adjustments to enhance tolerance or avoidance of summer drought and winter freezing were studied in shallow- to deep-rooted Patagonian cold desert shrubs. We measured leaf water potential, osmotic potential, tissue elasticity, stem hydraulic characteristics, and stomatal conductance across species throughout the year, and assessed tissue damage by subzero...

Alkaline β-fructofuranosidases of tuberous roots: Possible physiological function.

PubMed

Ricardo, C P

1974-12-01

Alkaline invertase of roots of carrot (Daucus carota L.) did not hydrolyze raffinose while the acid invertase from the same tissue showed with this sugar ca. 60% of the activity found with sucrose. The activity of the two invertases was inhibited by fructose to a different extent, the K i value being ca. 4×10(-2) M and 3×10(-1)M, respectively, for the alkaline and the acid invertases from the roots of both carrot and turnip (Brassica rapa L.). It is proposed that fructose inhibition of acid invertase is of no physiological significance but that, in contrast, hexoses might regulate the activity of alkaline invertase.Comparing several species and cultivars, it was found that the content of reducing sugars and the activity of alkaline invertase of mature tuberous roots showed a positive correlation. This indicates that alkaline invertase may participate in the regulation of the hexose level of the cell, as was previously suggested for sugar-cane. A scheme is presented which proposes a way of participation of alkaline invertase in such a regulation, assuming that this enzyme is located in the cytoplasm and acid invertase is membrane-bound and mainly located at the cell surface.

Factors influencing real time internal structural visualization and dynamic process monitoring in plants using synchrotron-based phase contrast X-ray imaging

PubMed Central

Karunakaran, Chithra; Lahlali, Rachid; Zhu, Ning; Webb, Adam M.; Schmidt, Marina; Fransishyn, Kyle; Belev, George; Wysokinski, Tomasz; Olson, Jeremy; Cooper, David M. L.; Hallin, Emil

2015-01-01

Minimally invasive investigation of plant parts (root, stem, leaves, and flower) has good potential to elucidate the dynamics of plant growth, morphology, physiology, and root-rhizosphere interactions. Laboratory based absorption X-ray imaging and computed tomography (CT) systems are extensively used for in situ feasibility studies of plants grown in natural and artificial soil. These techniques have challenges such as low contrast between soil pore space and roots, long X-ray imaging time, and low spatial resolution. In this study, the use of synchrotron (SR) based phase contrast X-ray imaging (PCI) has been demonstrated as a minimally invasive technique for imaging plants. Above ground plant parts and roots of 10 day old canola and wheat seedlings grown in sandy clay loam soil were successfully scanned and reconstructed. Results confirmed that SR-PCI can deliver good quality images to study dynamic and real time processes such as cavitation and water-refilling in plants. The advantages of SR-PCI, effect of X-ray energy, and effective pixel size to study plant samples have been demonstrated. The use of contrast agents to monitor physiological processes in plants was also investigated and discussed. PMID:26183486

Effect of simulated climate warming on the morphological and physiological traits of Elsholtzia haichowensis in copper contaminated soil.

PubMed

Guan, Ming; Jin, Zexin; Li, Junmin; Pan, Xiaocui; Wang, Suizi; Li, Yuelin

2016-01-01

The aim of this study was to investigate the effects of temperature and Cu on the morphological and physiological traits of Elsholtzia haichowensis grown in soils amended with four Cu concentrations (0, 50, 500, and 1000 mg kg(-1)) under ambient temperature and slight warming. At the same Cu concentration, the height, shoot dry weight, total plant dry weight, and root morphological parameters such as length, surface area and tip number of E. haichowensis increased due to the slight warming. The net photosynthetic rate, stomatal conductance, transpiration, light use efficiency were also higher under the slight warming than under ambient temperature. The increased Cu concentrations, total Cu uptake, bioaccumulation factors and tolerance indexes of shoots and roots were also observed at the slight warming. The shoot dry weight, root dry weight, total plant dry weight and the bioaccumulation factors of shoots and roots at 50 mg Cu kg(-1) were significantly higher than those at 500 and 1000 mg Cu kg(-1) under the slight warming. Therefore, the climate warming may improve the ability of E. haichowensis to phytoremediate Cu-contaminated soil, and the ability improvement greatly depended on the Cu concentrations in soils.

Shoot-derived abscisic acid promotes root growth.

PubMed

McAdam, Scott A M; Brodribb, Timothy J; Ross, John J

2016-03-01

The phytohormone abscisic acid (ABA) plays a major role in regulating root growth. Most work to date has investigated the influence of root-sourced ABA on root growth during water stress. Here, we tested whether foliage-derived ABA could be transported to the roots, and whether this foliage-derived ABA had an influence on root growth under well-watered conditions. Using both application studies of deuterium-labelled ABA and reciprocal grafting between wild-type and ABA-biosynthetic mutant plants, we show that both ABA levels in the roots and root growth in representative angiosperms are controlled by ABA synthesized in the leaves rather than sourced from the roots. Foliage-derived ABA was found to promote root growth relative to shoot growth but to inhibit the development of lateral roots. Increased root auxin (IAA) levels in plants with ABA-deficient scions suggest that foliage-derived ABA inhibits root growth through the root growth-inhibitor IAA. These results highlight the physiological and morphological importance, beyond the control of stomata, of foliage-derived ABA. The use of foliar ABA as a signal for root growth has important implications for regulating root to shoot growth under normal conditions and suggests that leaf rather than root hydration is the main signal for regulating plant responses to moisture. © 2015 John Wiley & Sons Ltd.

Transcriptomic Profiling and Physiological Responses of Halophyte Kochia sieversiana Provide Insights into Salt Tolerance

PubMed Central

Zhao, Long; Yang, Zongze; Guo, Qiaobing; Mao, Shun; Li, Shaoqiang; Sun, Fasheng; Wang, Huan; Yang, Chunwu

2017-01-01

Halophytes are remarkable plants that can tolerate extremely high-salinity conditions, and have different salinity tolerance mechanisms from those of glycophytic plants. In this work, we investigated the mechanisms of salinity tolerance of an extreme halophyte, Kochia sieversiana (Pall.) C. A. M, using RNA sequencing and physiological tests. The results showed that moderate salinity stimulated the growth and water uptake of K. sieversiana and, even under 480-mM salinity condition, K. sieversiana maintained an extremely high water content. This high water content may be a specific adaptive strategy of K. sieversiana to high salinity. The physiological analysis indicated that increasing succulence and great accumulations of sodium, alanine, sucrose, and maltose may be favorable to the water uptake and osmotic regulation of K. sieversiana under high-salinity stress. Transcriptome data indicated that some aquaporin genes and potassium (K+) transporter genes may be important for water uptake and ion balance, respectively, while different members of those gene families were employed under low- and high-salinity stresses. In addition, several aquaporin genes were up-regulated in low- but not high-salinity stressed roots. The highly expressed aquaporin genes may allow low-salinity stressed K. sieversiana plants to uptake more water than control plants. The leaf K+/root K+ ratio was enhanced under low- but not high-salinity stress, which suggested that low salinity might promote K+ transport from the roots to the shoots. Hence, we speculated that low salinity might allow K. sieversiana to uptake more water and transport more K+ from roots to shoots, increasing the growth rate of K. sieversiana. PMID:29225608

Aortic Root Biomechanics After Sleeve and David Sparing Techniques: A Finite Element Analysis.

PubMed

Tasca, Giordano; Selmi, Matteo; Votta, Emiliano; Redaelli, Paola; Sturla, Francesco; Redaelli, Alberto; Gamba, Amando

2017-05-01

Aortic root aneurysm can be treated with valve-sparing procedures. The David and Yacoub techniques have shown excellent long-term results but are technically demanding. Recently, a new and simpler procedure, the Sleeve technique, was proposed with encouraging results. We aimed to quantify the biomechanics of the initially aneurysmal aortic root (AR) after the Sleeve procedure to assess whether it induces abnormal stresses, potentially undermining its durability. Two finite element (FE) models of the physiologic and aneurysmal AR were built, accounting for the anatomical asymmetry and the nonlinear and anisotropic mechanical properties of human AR tissues. On the aneurysmal model, the Sleeve and David techniques were simulated based on the corresponding published technical features. Aortic root biomechanics throughout 2 consecutive cardiac cycles were computed in each simulated configuration. Both sparing techniques restored physiologic-like kinematics of aortic valve (AV) leaflets but induced different leaflets stresses. The time course averaged over the leaflets' bellies was 35% higher in the David model than in the Sleeve model. Commissural stresses, which were equal to 153 and 318 kPa in the physiologic and aneurysmal models, respectively, became 369 and 208 kPa in the David and Sleeve models, respectively. No intrinsic structural problems were detected in the Sleeve model that might jeopardize the durability of the procedure. If corroborated by long-term clinical outcomes, the results obtained suggest that using this new technique could successfully simplify the surgical repair of AR aneurysms and reduce intraoperative complications. Copyright © 2017 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Physiological adjustment to salt stress in Jatropha curcas is associated with accumulation of salt ions, transport and selectivity of K+, osmotic adjustment and K+/Na+ homeostasis.

PubMed

Silva, E N; Silveira, J A G; Rodrigues, C R F; Viégas, R A

2015-09-01

This study assessed the capacity of Jatropha curcas to physiologically adjust to salinity. Seedlings were exposed to increasing NaCl concentrations (25, 50, 75 and 100 mm) for 15 days. Treatment without NaCl was adopted as control. Shoot dry weight was strongly reduced by NaCl, reaching values of 35% to 65% with 25 to 100 mm NaCl. The shoot/root ratio was only affected with 100 mm NaCl. Relative water content (RWC) increased only with 100 mm NaCl, while electrolyte leakage (EL) was much enhanced with 50 mm NaCl. The Na(+) transport rate to the shoot was more affected with 50 and 100 mm NaCl. In parallel, Cl(-) transport rate increased with 75 and 100 mm NaCl, while K(+) transport rate fell from 50 mm to 100 mm NaCl. In roots, Na(+) and Cl(-) transport rates fell slightly only in 50 mm (to Na(+)) and 50 and 100 mm (to Cl(-)) NaCl, while K(+) transport rate fell significantly with increasing NaCl. In general, our data demonstrate that J. curcas seedlings present changes in key physiological processes that allow this species to adjust to salinity. These responses are related to accumulation of Na(+) and Cl(-) in leaves and roots, K(+)/Na(+) homeostasis, transport of K(+) and selectivity (K-Na) in roots, and accumulation of organic solutes contributing to osmotic adjustment of the species. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.

Physiological response of Arundo donax to cadmium stress by Fourier transform infrared spectroscopy

NASA Astrophysics Data System (ADS)

Yu, Shunhui; Sheng, Li; Zhang, Chunyan; Deng, Hongping

2018-06-01

The present paper deals with the physiological response of the changes in chemical contents of the root, stem and leaf of Arundo donax seedlings stressed by excess cadmium using Fourier transform infrared spectroscopy technique, cadmium accumulation in plant by atomic absorption spectroscopy were tested after different concentrations cadmium stress. The results showed that low cadmium concentrations (<1.0 mg/L) the root tissue of Arundo donax uses osmosis of organic substances (e.g. carbohydrates and amino acids) to improve cadmium tolerance. Organic substances (e.g. carbohydrates) that contain a lot of Osbnd H in leaf were transported to the root firstly and then could chelate cadmium, but no obvious changes in stems were noted. The cadmium in the shoots (stem and leaf) usually increased with increasing cadmium concentration. These studies demonstrate the potential of Fourier transform infrared spectroscopy technique for the non-invasive and rapid monitoring of the plants stressed with heavy metals, Arundo donax is suitable for phytoremediation of cadmium -contaminated wetland.

Functions of Nitric Oxide (NO) in Roots during Development and under Adverse Stress Conditions

PubMed Central

Corpas, Francisco J.; Barroso, Juan B.

2015-01-01

The free radical molecule, nitric oxide (NO), is present in the principal organs of plants, where it plays an important role in a wide range of physiological functions. Root growth and development are highly regulated by both internal and external factors such as nutrient availability, hormones, pattern formation, cell polarity and cell cycle control. The presence of NO in roots has opened up new areas of research on the role of NO, including root architecture, nutrient acquisition, microorganism interactions and the response mechanisms to adverse environmental conditions, among others. Additionally, the exogenous application of NO throughout the roots has the potential to counteract specific damages caused by certain stresses. This review aims to provide an up-to-date perspective on NO functions in the roots of higher plants. PMID:27135326

Aquatic Plants and Wastewater Treatment (an Overview)

NASA Technical Reports Server (NTRS)

Wolverton, B. C.

1986-01-01

The technology for using water hyacinth to upgrade domestic sewage effluent from lagoons and other wastewater treatment facilities to secondary and advanced secondary standards has been sufficiently developed to be used where the climate is warm year round. The technology of using emergent plants such as bulrush combined with duckweed is also sufficiently developed to make this a viable wastewater treatment alternative. This system is suited for both temperate and semi-tropical areas found throughout most of the U.S. The newest technology in artificial marsh wastewater treatment involves the use of emergent plant roots in conjunction with high surface area rock filters. Smaller land areas are required for these systems because of the increased concentration of microorganisms associated with the rock and plant root surfaces. Approximately 75 percent less land area is required for the plant-rock system than is required for a strict artificial wetland to achieve the same level of treatment.

Lateral root initiation in Marsilea quadrifolia. I. Origin and histogensis of lateral roots

NASA Technical Reports Server (NTRS)

Lin, B. L.; Raghavan, V.

1991-01-01

In Marsilea quadrifolia, lateral roots arise from modified single cells of the endodermis located opposite the protoxylem poles within the meristematic region of the parent root. The initial cell divides in four specific planes to establish a five-celled lateral root primordium, with a tetrahedral apical cell in the centre and the oldest merophytes and the root cap along the sides. The cells of the merophyte divide in a precise pattern to give rise to the cells of the cortex, endodermis, pericycle, and vascular tissues of the emerging lateral root. Although the construction of the parent root is more complicated than that of lateral roots, patterns of cell division and tissue formation are similar in both types of roots, with the various tissues being arranged in similar positions in relation to the central axis. Vascular connection between the lateral root primordium and the parent root is derived from the pericycle cells lying between the former and the protoxylem members of the latter. It is proposed that the central axis of the root is not only a geometric centre, but also a physiological centre which determines the fate of the different cell types.

Physiological responses of biomass allocation, root architecture, and invertase activity to copper stress in young seedlings from two populations of Kummerowia stipulacea (maxim.) Makino.

PubMed

Zhang, Luan; Pan, Yuxue; Lv, Wei; Xiong, Zhi-ting

2014-06-01

In the current study, we hypothesize that mine (metallicolous) populations of metallophytes form a trade-off between the roots and shoots when under copper (Cu) stress to adapt themselves to heavy metal contaminated habitats, and thus, differ from normal (non-metallicolous) populations in biomass allocation. To test the hypothesis, two populations of the metallophyte Kummerowia stipulacea, one from an ancient Cu mine (MP) and the other from a non-contaminated site (NMP), were treated with Cu(2+) in hydroponic conditions. The results showed that MP plants had higher root/shoot biomass allocation and more complicated root system architecture compared to those of the NMP plants when under Cu stress. The net photosynthetic capacity was more inhibited in the NMP plants than in the MP plants when under Cu stress. The sugar (sucrose and hexose) contents and acid invertase activities of MP plants were elevated while those in NMP plants were inhibited after Cu treatment. The neutral/alkaline invertase activities and sucrose synthase level showed no significant differences between the two populations when under Cu stress. The results showed that acid invertase played an important role in biomass allocation and that the physiological responses were beneficial for the high root/shoot biomass allocation, which were advantageous during adaptive evolution to Cu-enriched mine soils. Copyright © 2014 Elsevier Inc. All rights reserved.

Contribution of constitutive characteristics of lipids and phenolics in roots of tree species in Myrtales to aluminum tolerance.

PubMed

Maejima, Eriko; Osaki, Mitsuru; Wagatsuma, Tadao; Watanabe, Toshihiro

2017-05-01

High aluminum (Al) concentration in soil solution is the most important factor restricting plant growth in acidic soils. However, various plant species naturally grow in such soils. Generally, they are highly tolerant to Al, but organic acid exudation, the most common Al tolerance mechanism, cannot explain their tolerance. Lower phospholipid and higher sterol proportions in root plasma membrane enhance Al tolerance. Other cellular components, such as cell walls and phenolics, may also be involved in Al tolerance mechanisms. In this study, the relationships between these cellular components and the Al tolerance mechanisms in Melastoma malabathricum and Melaleuca cajuputi, both highly Al-tolerant species growing in strongly acidic soils, were investigated. Both species contained lower proportions of phospholipids and higher proportions of sterols in roots, respectively. Concentrations of phenolics in roots of both species were higher than that of rice; their phenolics could form chelates with Al. In these species, phenolic concentrations and composition were the same irrespective of the presence or absence of Al in the medium, suggesting that a higher concentration of phenolics is not a physiological response to Al but a constitutive characteristic. These characteristics of cellular components in roots may be cooperatively involved in their high Al tolerance. © 2016 The Authors. Physiologia Plantarum published by John Wiley & Sons Ltd on behalf of Scandinavian Plant Physiology Society.

Enhanced root exudation stimulates soil nitrogen transformations in a subalpine coniferous forest under experimental warming.

PubMed

Yin, Huajun; Li, Yufei; Xiao, Juan; Xu, Zhenfeng; Cheng, Xinyin; Liu, Qing

2013-07-01

Despite the perceived importance of exudation to forest ecosystem function, few studies have attempted to examine the effects of elevated temperature and nutrition availability on the rates of root exudation and associated microbial processes. In this study, we performed an experiment in which in situ exudates were collected from Picea asperata seedlings that were transplanted in disturbed soils exposed to two levels of temperature (ambient temperature and infrared heater warming) and two nitrogen levels (unfertilized and 25 g N m(-2)  a(-1) ). Here, we show that the trees exposed to an elevated temperature increased their exudation rates I (μg C g(-1) root biomass h(-1) ), II (μg C cm(-1)  root length h(-1) ) and III (μg C cm(-2)  root area h(-1) ) in the unfertilized plots. The altered morphological and physiological traits of the roots exposed to experimental warming could be responsible for this variation in root exudation. Moreover, these increases in root-derived C were positively correlated with the microbial release of extracellular enzymes involved in the breakdown of organic N (R(2)  = 0.790; P = 0.038), which was coupled with stimulated microbial activity and accelerated N transformations in the unfertilized soils. In contrast, the trees exposed to both experimental warming and N fertilization did not show increased exudation rates or soil enzyme activity, indicating that the stimulatory effects of experimental warming on root exudation depend on soil fertility. Collectively, our results provide preliminary evidence that an increase in the release of root exudates into the soil may be an important physiological adjustment by which the sustained growth responses of plants to experimental warming may be maintained via enhanced soil microbial activity and soil N transformation. Accordingly, the underlying mechanisms by which plant root-microbe interactions influence soil organic matter decomposition and N cycling should be incorporated into climate-carbon cycle models to determine reliable estimates of long-term C storage in forests. © 2013 Blackwell Publishing Ltd.

Effects of norflurazon, an inhibitor of carotenogenesis, on abscisic acid and xanthoxin in the caps of gravistimulated maize roots

NASA Technical Reports Server (NTRS)

Feldman, L. J.; Sun, P. S.

1986-01-01

Maize seeds were germinated in the dark in the presence of the carotenoid synthesis inhibitor norflurazon and the levels of abscisic acid, xanthoxin and total carotenoids were measured in the root cap and in the adjacent 1.5 mm segment. In norflurazon-treated roots abscisic acid levels were markedly reduced, but an increase occurred in the levels of xanthoxin, a compound structurally and physiologically similar to abscisic acid. In the cultivar of maize (Zea mays L. cv. Merit) used for this work, brief illumination of the root is required for gravitropic curving. Following illumination both control and norflurazon-treated roots showed normal gravitropic curvature; however, the rate of curvature was delayed in norflurazon-treated roots. Our data from norflurazon-treated roots are consistent with a role for xanthoxin in maize root gravitropism. The increase in xanthoxin in the presence of an inhibitor of carotenoid synthesis suggests that xanthoxin and abscisic acid originate, at least in part, via different metabolic pathways.

Metabolic and physiological adjustment of Suaeda maritima to combined salinity and hypoxia

PubMed Central

Behr, Jan H.; Bouchereau, Alain; Berardocco, Solenne; Seal, Charlotte E.; Flowers, Timothy J.

2017-01-01

Background and Aims Suaeda maritima is a halophyte commonly found on coastal wetlands in the intertidal zone. Due to its habitat S. maritima has evolved tolerance to high salt concentrations and hypoxic conditions in the soil caused by periodic flooding. In the present work, the adaptive mechanisms of S. maritima to salinity combined with hypoxia were investigated on a physiological and metabolic level. Methods To compare the adaptive mechanisms to deficient, optimal and stressful salt concentrations, S. maritima plants were grown in a hydroponic culture under low, medium and high salt concentrations. Additionally, hypoxic conditions were applied to investigate the impact of hypoxia combined with different salt concentrations. A non-targeted metabolic approach was used to clarify the biochemical pathways underlying the metabolic and physiological adaptation mechanisms of S. maritima. Key Results Roots exposed to hypoxic conditions showed an increased level of tricarboxylic acid (TCA)-cycle intermediates such as succinate, malate and citrate. During hypoxia, the concentration of free amino acids increased in shoots and roots. Osmoprotectants such as proline and glycine betaine increased in concentrations as the external salinity was increased under hypoxic conditions. Conclusions The combination of high salinity and hypoxia caused an ionic imbalance and an increase of metabolites associated with osmotic stress and photorespiration, indicating a severe physiological and metabolic response under these conditions. Disturbed proline degradation in the roots induced an enhanced proline accumulation under hypoxia. The enhanced alanine fermentation combined with a partial flux of the TCA cycle might contribute to the tolerance of S. maritima to hypoxic conditions. PMID:28110268

Differential response of hexaploid and tetraploid wheat to interactive effects of elevated [CO2] and low phosphorus.

PubMed

Pandey, Renu; Lal, Milan Kumar; Vengavasi, Krishnapriya

2018-06-04

Hexaploid wheat is more responsive than tetraploid to the interactive effects of elevated [CO 2 ] and low P in terms of carboxylate efflux, enzyme activity and gene expression (TaPT1 and TaPAP). Availability of mineral nutrients to plants under changing climate has become a serious challenge to food security and economic development. An understanding of how elevated [CO 2 ] influences phosphorus (P) acquisition processes at the whole-plant level would be critical in selecting cultivars as well as to maintain optimum yield in limited-P conditions. Wheat (Triticum aestivum and T. durum) grown hydroponically with sufficient and low P concentration were exposed to elevated and ambient [CO 2 ]. Improved dry matter partitioning towards root resulted in increased root-to-shoot ratio, root length, volume, surface area, root hair length and density at elevated [CO 2 ] with low P. Interaction of low P and [CO 2 ] induced activity of enzymes (phosphoenolpyruvate carboxylase, malate dehydrogenase and citrate synthase) in root tissue resulting in twofold increase in carboxylates and acid phosphatase exudation. Physiological absorption capacity of roots showed that plants alter their uptake kinetics by increasing affinity (low K m ) in response to elevated [CO 2 ] under low P supply. Increased relative expression of genes, purple acid phosphatase (TaPAP) and high-affinity Pi transporter (TaPT1) in roots induced by elevated [CO 2 ] and low P supported our physiological observations. Hexaploid wheat (PBW-396) being more responsive to elevated [CO 2 ] at low P supply as compared to tetraploid (PDW-233) necessitates the ploidy effect to be explored further which might be advantageous under changing climate.

Pyridine 2,4-dicarboxylic acid suppresses tomato seedling growth

NASA Astrophysics Data System (ADS)

Fragkostefanakis, Sotirios; Kaloudas, Dimitrios; Kalaitzis, Panagiotis

2018-01-01

Pyridine 2,4-dicarboxylic acid is a structural analogue of 2-oxoglutarate and is known to inhibit 2-oxoglutare-dependent dioxygenases. The effect of this inhibitor in tomato seedlings grown in MS media supplied with various concentrations of PDCA was investigated, resulting in shorter roots and hypocotyls in a dose-dependent manner. The partial inhibition of growth in roots was more drastic compared to hypocotyls and was attributed to a decrease in the elongation of root and hypocotyl cells. Concentrations of 100 and 250 μΜ of PDCA decreased hydroxyproline content in roots while only the 250 μΜ treatment reduced the hydroxyproline content in shoots. Seedlings treated with 100 μΜ PDCA exhibited enhanced growth of hypocotyl and cotyledon cells and higher hydroxyproline content resulting in cotyledons with greater surface area. However, no alterations in hypocotyl length were observed. Prolyl 4 hydroxylases (P4Hs) are involved in the O-glycosylation of AGPs and were also highly expressed during seedling growth. Moreover PDCA induced a decrease in the accumulation of HRGPs and particularly in AGPs-bound epitopes in a dose dependent-manner while more drastic reduction were observed in roots compared to shoots. In addition, bulged root epidermal cells were observed at the high concentration of 250 μΜ which is characteristic of root tissues with glycosylation defects. These results indicate that PDCA induced pleiotropic effects during seedling growth while further studies are required to better investigate the physiological significance of this 2-oxoglutarate analogue. This pharmacological approach might be used as a tool to better understand the physiological significance of HRGPs and probably P4Hs in various growth and developmental programs in plants.

7 CFR 51.2 - Terms defined.

Code of Federal Regulations, 2013 CFR

2013-01-01

...; mechanical injuries resulting from improper handling after packing; progressive pathological, physiological, and virus diseases, including fungal and bacterial roots; and freezing damage which may occur in...

Azospirillum brasilense, a Beneficial Soil Bacterium: Isolation and Cultivation.

PubMed

Alexandre, Gladys

2017-11-09

Bacteria of the genus Azospirillum comprise 15 species to date, with A. brasilense the best studied species in the genus. Azospirillum are soil bacteria able to promote the growth of plants from 113 species spanning 35 botanical families. These non-pathogenic and beneficial bacteria are ubiquitous in soils and inhabit the roots of diverse plants. These bacteria are microaerophilic, able to fix nitrogen under free-living conditions, motile, and able to navigate in gradients of various chemicals, including oxygen. These physiological traits are used to isolate these soil bacteria from soil and plant root samples, providing isolates that can be used for studying microbial physiology and plant growth promotion. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

Involvement of Arabidopsis thaliana phospholipase Dzeta2 in root hydrotropism through the suppression of root gravitropism.

PubMed

Taniguchi, Yukimi Y; Taniguchi, Masatoshi; Tsuge, Tomohiko; Oka, Atsuhiro; Aoyama, Takashi

2010-01-01

Root hydrotropism is the phenomenon of directional root growth toward moisture under water-deficient conditions. Although physiological and genetic studies have revealed the involvement of the root cap in the sensing of moisture gradients, and those of auxin and abscisic acid (ABA) in the signal transduction for asymmetric root elongation, the overall mechanism of root hydrotropism is still unclear. We found that the promoter activity of the Arabidopsis phospholipase Dzeta2 gene (PLDzeta2) was localized to epidermal cells in the distal root elongation zone and lateral root cap cells adjacent to them, and that exogenous ABA enhanced the activity and extended its area to the entire root cap. Although pldzeta2 mutant root caps did not exhibit a morphological phenotype in either the absence or presence of exogenous ABA, the inhibitory effect of ABA on gravitropism, which was significant in wild-type roots, was not observed in pldzeta2 mutant roots. In root hydrotropism experiments, pldzeta2 mutations significantly retarded or disturbed root hydrotropic responses. A drought condition similar to that used in a hydrotropism experiment enhanced the PLDzeta2 promoter activity in the root cap, as did exogenous ABA. These results suggest that PLDzeta2 responds to drought through ABA signaling in the root cap and accelerates root hydrotropism through the suppression of root gravitropism.

Biomechanical and Physiological Validation of the Omni-Directional Treadmill Upgrade as a Mobility Platform for Immersive Environments

DTIC Science & Technology

2011-04-01

a potentially unstable single limb ( Marigold and Patla, 2002; Murray et al., 1985). In theory, adopting a more flexed posture should also lower the...when knowingly traversing slippery terrain ( Marigold and Patla). Despite minimal differences in temporal-spatial values and kinematics for the two...Walking in Healthy Individuals. J. Appl. Physiol. 2008, 104, 747–755. 22 Marigold , D. S.; Patla, A. E. Strategies for Dynamic Stability During

Maize water status and physiological traits as affected by root endophytic fungus Piriformospora indica under combined drought and mechanical stresses.

PubMed

Hosseini, Fatemeh; Mosaddeghi, Mohammad Reza; Dexter, Anthony Roger; Sepehri, Mozhgan

2018-05-01

Under combined drought and mechanical stresses, mechanical stress primarily controlled physiological responses of maize. Piriformospora indica mitigated the adverse effects of stresses, and inoculated maize experienced less oxidative damage and had better adaptation to stressful conditions. The objective of this study was to investigate the effect of maize root colonization by an endophytic fungus P. indica on plant water status, physiological traits and root morphology under combined drought and mechanical stresses. Seedlings of inoculated and non-inoculated maize (Zea mays L., cv. single cross 704) were cultivated in growth chambers filled with moistened siliceous sand at a matric suction of 20 hPa. Drought stress was induced using PEG 6000 solution with osmotic potentials of 0, - 0.3 and - 0.5 MPa. Mechanical stress (i.e., penetration resistances of 1.05, 4.23 and 6.34 MPa) was exerted by placing weights on the surface of the sand medium. After 30 days, leaf water potential (LWP) and relative water content (RWC), root and shoot fresh weights, root volume (RV) and diameter (RD), leaf proline content, leaf area (LA) and catalase (CAT) and ascorbate peroxidase (APX) activities were measured. The results show that exposure to individual drought and mechanical stresses led to higher RD and proline content and lower plant biomass, RV and LA. Moreover, increasing drought and mechanical stress severity increased APX activity by about 1.9- and 3.1-fold compared with the control. When plants were exposed to combined stresses, mechanical stress played the dominant role in controlling plant responses. P. indica-inoculated plants are better adapted to individual and combined stresses. The inoculated plants had greater RV, LA, RWC, LWP and proline content under stressful conditions. In comparison with non-inoculated plants, inoculated plants showed lower CAT and APX activities which means that they experienced less oxidative stress induced by stressful conditions.

Physiological girdling of pine trees via phloem chilling: proof of concept

Treesearch

Kurt Johnsen; Chris Maier; Felipe Sanchez; Peter Anderson; John Butnor; Richard Waring; Sune Linder

2007-01-01

Quantifying below-ground carbon (C) allocation is particularly difficult as methods usually disturb the root– mycorrhizal–soil continuum. We reduced C allocation below ground of loblolly pine trees by: (1) physically girdling trees and (2) physiologically girdling pine trees by chilling the phloem. Chilling reduced cambium temperatures by approximately 18 °C. Both...

The response of sap flow to pulses of rain in a temperate Australian woodland

Treesearch

Melanie Zeppel; Catrioina M.O. Macinnis-Ng; Chelcy R. Ford; Derek Eamus

2008-01-01

In water-limited systems, pulses of rainfall can trigger a cascade of plant physiological responses. However, the timing and size of the physiological response can vary depending on plant and environmental characteristics, such as rooting depth, plant size, rainfall amount, or antecedent soil moisture. We investigated the influence of pulses of rainfall on the response...

Associating root morphology and physiology with molybdenum uptake of three rice varieties grown in three pH regimes

USDA-ARS?s Scientific Manuscript database

Molybdenum (Mo) is an essential micronutrient required in very low amounts (0.1-1 µg g-1 dry weight) in plants. It acts as a co-factor of certain enzymes carrying out redox reactions and is required for various physiological, biochemical and metabolic processes. However, its accumulation in excess l...

Growth and physiological responses of some Capsicum frutescens varieties to copper stress

NASA Astrophysics Data System (ADS)

Jadid, Nurul; Maziyah, Rizka; Nurcahyani, Desy Dwi; Mubarokah, Nilna Rizqiyah

2017-06-01

Copper (Cu) is an essential micronutrient participating in various physiological processes. However, excessive uptake of this micronutrient could potentially affect plant growth and development as well as plant productivity. In this present work, growth and physiological responses of some Capsicum frustescens varieties to Cu stress were determined. Three C. frutescens varieties used in this work were var. Bara, CF 291, and Genie. In addition, these varieties were treated with different concentration of Cu (0, 30, 70, and 120 ppm). The growth and physiological responses measured in this work included plant height, root length, malondialdehyde (MDA), and chlorophyll. The result showed that all varieties tested relatively displayed plant growth reduction including plant height and root length. Likewise, an increase of MDA level, a major bioindicator for oxidative damage was also found in all varieties following exposure to elevated Cu concentration. Finally, the chlorophyll content was also affected indicated by a decreased amount of chlorophyll, especially in var. CF291. The overall results demonstrated that elevated Cu concentration might decrease C. frutescens productivity where among the three varieties tested, var CF 291 seemed to be the most sensitive varieties to Cu stress.

Drought induced changes of leaf-to-root relationships in two tomato genotypes.

PubMed

Moles, Tommaso Michele; Mariotti, Lorenzo; De Pedro, Leandro Federico; Guglielminetti, Lorenzo; Picciarelli, Piero; Scartazza, Andrea

2018-07-01

Water deficit triggers a dynamic and integrated cross-talk between leaves and roots. Tolerant plants have developed several physiological and molecular mechanisms to establish new cell metabolism homeostasis, avoiding and/or escaping from permanent impairments triggered by drought. Two tomato genotypes (a Southern Italy landrace called Ciettaicale and the well-known commercial cultivar Moneymaker) were investigated at vegetative stage to assess leaf and root metabolic strategies under 20 days of water deficit. Physiological and metabolic changes, in terms of ABA, IAA, proline, soluble sugars and phenols contents, occurred in both tomato genotypes under water stress. Overall, our results pointed out the higher plasticity of Ciettaicale to manage plant water status under drought in order to preserve the source-sink relationships. This aim was achieved by maintaining a more efficient leaf photosystem II (PSII) photochemistry, as suggested by chlorophyll fluorescence parameters, associated with a major investment towards root growth and activity to improve water uptake. On the contrary, the higher accumulation of carbon compounds, resulting from reduced PSII photochemistry and enhanced starch reserve mobilization, in leaves and roots of Moneymaker under drought could play a key role in the osmotic adjustment, although causing a feedback disruption of the source-sink relations. This hypothesis was also supported by the different drought-induced redox unbalance, as suggested by H 2 O 2 and MDA contents. This could affect both PSII photochemistry and root activity, leading to a major involvement of NPQ and antioxidant system in response to drought in Moneymaker than Ciettaicale. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

[Responses of the common bean (Phaseolus vulgaris L.) and Rhizobium tropici CIAT899 symbiosystem to induced allelopathy by Ipomoea purpurea L. Roth].

PubMed

Pérez-Peralta, Paulina Janneth; Ferrera-Cerrato, Ronald; Alarcón, Alejandro; Trejo-Téllez, Libia I; Cruz-Ortega, Rocío; Silva-Rojas, Hilda V

2018-06-07

Allelopathy is a phenomenon that involves the production of secondary metabolites that influence the growth of plants and microorganisms; however, this alellopathic effect has been scarcely studied on the rhizobia-legume symbiosis. The aims of this research were 1) to assess the allelopathic potential of aqueous extracts of Ipomoea purpurea L. Roth on seed germination and root length of common bean seedlings (Phaseolus vulgaris L.), 2) to determine its effects on the in vitro growth of Rhizobium tropici CIAT899, and 3) to evaluate the allelopathic potential of I. purpurea on the growth, nodulation and physiology of common bean plants inoculated with R. tropici. After 48h, 15% of the aqueous root extract of I. purpurea stimulated seed germination, whereas 4% of the aqueous shoot extracts stimulated such germination. Both the root or shoot extracts stimulated seed germination and e root length. In vitro growth of R. tropici was inhibited as a result of the application of both aqueous extracts. The presence of I. purpurea negatively affected both the growth and physiological responses of common bean plants, and this effect was attenuated after the inoculation of R. tropici; nevertheless, this allelopathic plant affected root nodulation. Our results suggest that the symbiosis of rhizobia and roots of common bean plants is an important element for attenuating the negative effects caused by the allelopathic plant. Copyright © 2018 Asociación Argentina de Microbiología. Publicado por Elsevier España, S.L.U. All rights reserved.

Genome-wide microarray analysis of tomato roots showed defined responses to iron deficiency

PubMed Central

2012-01-01

Background Plants react to iron deficiency stress adopting different kind of adaptive responses. Tomato, a Strategy I plant, improves iron uptake through acidification of rhizosphere, reduction of Fe3+ to Fe2+ and transport of Fe2+ into the cells. Large-scale transcriptional analyses of roots under iron deficiency are only available for a very limited number of plant species with particular emphasis for Arabidopsis thaliana. Regarding tomato, an interesting model species for Strategy I plants and an economically important crop, physiological responses to Fe-deficiency have been thoroughly described and molecular analyses have provided evidence for genes involved in iron uptake mechanisms and their regulation. However, no detailed transcriptome analysis has been described so far. Results A genome-wide transcriptional analysis, performed with a chip that allows to monitor the expression of more than 25,000 tomato transcripts, identified 97 differentially expressed transcripts by comparing roots of Fe-deficient and Fe-sufficient tomato plants. These transcripts are related to the physiological responses of tomato roots to the nutrient stress resulting in an improved iron uptake, including regulatory aspects, translocation, root morphological modification and adaptation in primary metabolic pathways, such as glycolysis and TCA cycle. Other genes play a role in flavonoid biosynthesis and hormonal metabolism. Conclusions The transcriptional characterization confirmed the presence of the previously described mechanisms to adapt to iron starvation in tomato, but also allowed to identify other genes potentially playing a role in this process, thus opening new research perspectives to improve the knowledge on the tomato root response to the nutrient deficiency. PMID:22433273

Physiologically grounded metrics of model skill: a case study estimating heat stress in intertidal populations

PubMed Central

Kish, Nicole E.; Helmuth, Brian; Wethey, David S.

2016-01-01

Models of ecological responses to climate change fundamentally assume that predictor variables, which are often measured at large scales, are to some degree diagnostic of the smaller-scale biological processes that ultimately drive patterns of abundance and distribution. Given that organisms respond physiologically to stressors, such as temperature, in highly non-linear ways, small modelling errors in predictor variables can potentially result in failures to predict mortality or severe stress, especially if an organism exists near its physiological limits. As a result, a central challenge facing ecologists, particularly those attempting to forecast future responses to environmental change, is how to develop metrics of forecast model skill (the ability of a model to predict defined events) that are biologically meaningful and reflective of underlying processes. We quantified the skill of four simple models of body temperature (a primary determinant of physiological stress) of an intertidal mussel, Mytilus californianus, using common metrics of model performance, such as root mean square error, as well as forecast verification skill scores developed by the meteorological community. We used a physiologically grounded framework to assess each model's ability to predict optimal, sub-optimal, sub-lethal and lethal physiological responses. Models diverged in their ability to predict different levels of physiological stress when evaluated using skill scores, even though common metrics, such as root mean square error, indicated similar accuracy overall. Results from this study emphasize the importance of grounding assessments of model skill in the context of an organism's physiology and, especially, of considering the implications of false-positive and false-negative errors when forecasting the ecological effects of environmental change. PMID:27729979

Metabolic analysis of the increased adventitious rooting mutant of Artemisia annua reveals a role for the plant monoterpene borneol in adventitious root formation.

PubMed

Tian, Na; Liu, Shuoqian; Li, Juan; Xu, Wenwen; Yuan, Lin; Huang, Jianan; Liu, Zhonghua

2014-08-01

Adventitious root (AR) formation is a critical process for plant clonal propagation. The role of plant secondary metabolites in AR formation is still poorly understood. Chemical and physical mutagenesis in combination with somatic variation were performed on Artemisia annua in order to obtain a mutant with changes in adventitious rooting and composition of plant secondary metabolites. Metabolic and morphological analyses of the iar (increased adventitious rooting) mutant coupled with in vitro assays were used to elucidate the relationship between plant secondary metabolites and AR formation. The only detected differences between the iar mutant and wild-type were rooting capacity and borneol/camphor content. Consistent with this, treatment with borneol in vitro promoted adventitious rooting in wild-type. The enhanced rooting did not continue upon removal of borneol. The iar mutant displayed no significant differences in AR formation upon treatment with camphor. Together, our results suggest that borneol promotes adventitious rooting whereas camphor has no effect on AR formation. © 2013 Scandinavian Plant Physiology Society.

Responses of root physiological characteristics and yield of sweet potato to humic acid urea fertilizer

PubMed Central

Kou, Meng; Tang, Zhonghou; Zhang, Aijun; Li, Hongmin; Wei, Meng

2017-01-01

Humic acid (HA), not only promote the growth of crop roots, they can be combined with nitrogen (N) to increase fertilizer use efficiency and yield. However, the effects of HA urea fertilizer (HA-N) on root growth and yield of sweet potato has not been widely investigated. Xushu 28 was used as the experimental crop to investigate the effects of HA-N on root morphology, active oxygen metabolism and yield under field conditions. Results showed that nitrogen application alone was not beneficial for root growth and storage root formation during the early growth stage. HA-N significantly increased the dry weight of the root system, promoted differentiation from adventitious root to storage root, and increased the overall root activity, total root length, root diameter, root surface area, as well as root volume. HA-N thus increased the activity of superoxide dismutase (SOD), peroxidase (POD), and Catalase (CAT) as well as increasing the soluble protein content of roots and decreasing the malondialdehyde (MDA) content. HA-N significantly increased both the number of storage roots per plant increased by 14.01%, and the average fresh weight per storage root increased by 13.7%, while the yield was also obviously increased by 29.56%. In this study, HA-N increased yield through a synergistic increase of biological yield and harvest index. PMID:29253886

Morphology of the Physiological Apical Foramen in Maxillary and Mandibular First Molars

PubMed Central

Abarca, J.; Zaror, C.; Monardes, H.; Hermosilla, V.; Muñoz, C.; Cantin, M.

2015-01-01

SUMMARY Information regarding the anatomy of the physiological apical foramen is limited. Knowing its diameter and shapes contributes to clinical work, specifically to the cleaning and shaping of the apical third. The aim of this ex vivo study was to determine the minimum and maximum diameters and shape of the physiological apical foramen in the roots of maxillary and mandibular first molars. A descriptive study was conducted on 89 recently extracted first molars. Roots 3–5 mm from the apex were sectioned and prepared for analysis at 40× magnification. The minimum and maximum diameters of each physiological foramen were measured using the program Motic Images plus 2.0 ML. The shape of the foramina, classified as round, oval or irregular, was determined by the difference between the maximum and minimum diameters. A total of 174 physiological foramina were analyzed. The average of the minimum and maximum diameters was between 0.24–0.33 mm in maxillary first molars and between 0.25–0.33 mm in mandibular first molars. In maxillary molars, the most common shape of the foramen was oval (50%), then irregular (32%), then round (18%). In mandibular molars, the oval shape was also the most frequent (59%), followed by irregular (23%) and round (18%). The findings of this study regarding the morphology of physiological apical foramina in first molars make it easier for the operator to choose the appropriately-sized instruments to perform endodontic therapy successfully. PMID:25937698

Morphology of the Physiological Apical Foramen in Maxillary and Mandibular First Molars.

PubMed

Abarca, J; Zaror, C; Monardes, H; Hermosilla, V; Muñoz, C; Cantin, M

2014-06-01

Information regarding the anatomy of the physiological apical foramen is limited. Knowing its diameter and shapes contributes to clinical work, specifically to the cleaning and shaping of the apical third. The aim of this ex vivo study was to determine the minimum and maximum diameters and shape of the physiological apical foramen in the roots of maxillary and mandibular first molars. A descriptive study was conducted on 89 recently extracted first molars. Roots 3-5 mm from the apex were sectioned and prepared for analysis at 40× magnification. The minimum and maximum diameters of each physiological foramen were measured using the program Motic Images plus 2.0 ML. The shape of the foramina, classified as round, oval or irregular, was determined by the difference between the maximum and minimum diameters. A total of 174 physiological foramina were analyzed. The average of the minimum and maximum diameters was between 0.24-0.33 mm in maxillary first molars and between 0.25-0.33 mm in mandibular first molars. In maxillary molars, the most common shape of the foramen was oval (50%), then irregular (32%), then round (18%). In mandibular molars, the oval shape was also the most frequent (59%), followed by irregular (23%) and round (18%). The findings of this study regarding the morphology of physiological apical foramina in first molars make it easier for the operator to choose the appropriately-sized instruments to perform endodontic therapy successfully.

Plant root and shoot dynamics during subsurface obstacle interaction

NASA Astrophysics Data System (ADS)

Conn, Nathaniel; Aguilar, Jeffrey; Benfey, Philip; Goldman, Daniel

As roots grow, they must navigate complex underground environments to anchor and retrieve water and nutrients. From gravity sensing at the root tip to pressure sensing along the tip and elongation zone, the complex mechanosensory feedback system of the root allows it to bend towards greater depths and avoid obstacles of high impedance by asymmetrically suppressing cell elongation. Here we investigate the mechanical and physiological responses of roots to rigid obstacles. We grow Maize, Zea mays, plants in quasi-2D glass containers (22cm x 17cm x 1.4cm) filled with photoelastic gel and observe that, regardless of obstacle interaction, smaller roots branch off the primary root when the upward growing shoot (which contains the first leaf) reaches an average length of 40 mm, coinciding with when the first leaf emerges. However, prior to branching, contacts with obstacles result in reduced root growth rates. The growth rate of the root relative to the shoot is sensitive to the angle of the obstacle surface, whereby the relative root growth is greatest for horizontally oriented surfaces. We posit that root growth is prioritized when horizontal obstacles are encountered to ensure anchoring and access to nutrients during later stages of development. NSF Physics of Living Systems.

Integration of root phenes revealed by intensive phenotyping of root system architecture, anatomy, and physiology in cereals

NASA Astrophysics Data System (ADS)

York, Larry

2015-04-01

Food insecurity is among the greatest challenges humanity will face in the 21st century. Agricultural production in much of the world is constrained by the natural infertility of soil which restrains crops from reaching their yield potential. In developed nations, fertilizer inputs pollute air and water and contribute to climate change and environmental degradation. In poor nations low soil fertility is a primary constraint to food security and economic development. Water is almost always limiting crop growth in any system. Increasing the acquisition efficiency of soil resources is one method by which crop yields could be increased without the use of more fertilizers or irrigation. Cereals are the most widely grown crops, both in terms of land area and in yield, so optimizing uptake efficiency of cereals is an important goal. Roots are the primary interface between plant and soil and are responsible for the uptake of soil resources. The deployment of roots in space and time comprises root system architecture (RSA). Cereal RSA is a complex phenotype that aggregates many elemental phenes (elemental units of phenotype). Integration of root phenes will be determined by interactions through their effects on soil foraging and plant metabolism. Many architectural, metabolic, and physiological root phenes have been identified in maize, including: nodal root number, nodal root growth angle, lateral root density, lateral root length, aerenchyma, cortical cell size and number, and nitrate uptake kinetics. The utility of these phenes needs confirmation in maize and in other cereals. The maize root system is composed of an embryonic root system and nodal roots that emerge in successive whorls as the plant develops, and is similar to other cereals. Current phenotyping platforms often ignore the inner whorls and instead focus on the most visible outer whorls after excavating a maize root crown from soil. Here, an intensive phenotyping platform evaluating phenes of all nodal root whorls in maize is introduced, and field work demonstrated how the variation within the root crown has functional significance for nitrogen acquisition. Nodal root number was decomposed to more elemental phenes including the number of nodes and the occupancies of each node. Simulations demonstrated that root systems forming fewer nodal roots and with delayed emergence perform well in low nitrogen soils. Nitrate uptake kinetics (NUK) also varied within the maize root system, and simulations showing a lack of interaction between NUK and RSA reflects a knowledge gap in the costs of NUK at the molecular level. Finally, maize RSA among hybrids from different era periods over the past 100 years suggests evolution towards more nitrogen efficient root phene states. This work will be discussed within the context of next-generation root phenotyping of cereals, the dilemma between extensive and intensive phenotyping, and the need for linking across scales and methods.

Alleviation of Cd toxicity by composted sewage sludge in Cd-treated Schmidt birch (Betula schmidtii) seedlings.

PubMed

Han, Sim-Hee; Lee, Jae-Cheon; Oh, Chang-Young; Kim, Pan-Gi

2006-10-01

We investigated alleviation of Cd toxicity and changes in the physiological characteristics of Betula schmidtii seedlings following application of composted sewage sludge to Cd-treated plants. Plants were grown under four test conditions: control, Cd treatment, sludge amendment, and Cd treatment with sludge amendment. B. schmidtii treated with Cd only accumulated the greatest amount of Cd in the leaves, but absorbed Cd was also highly concentrated in the roots. In contrast, Cd concentrations in the Cd and sludge amendment treated seedlings were the lowest in the roots. Since sludge amendment increased the growth of seedlings, it may have alleviated toxicity by dilution of Cd. Additionally, the absorbed Cd was more widely distributed since it was transported from the roots and accumulated in the stems and leaves of Cd and sludge treated plants. Cd treatment inhibited the growth and physiological functions of B. schmidtii seedlings, but sludge amendment compensated for these effects and improved growth and physiological functions in both Cd-treated and control plants. SOD activity in the leaves of seedlings was increased in the Cd-treated plants, but not in the Cd and sludge amendment treated seedlings. In conclusion, alleviation of Cd toxicity in response to sludge amendment may be related to a dilution effect, in which the Cd concentration in the tissues was effectively lowered by the improved growth performance of the seedlings.

Xylem transport and gene expression play decisive roles in cadmium accumulation in shoots of two oilseed rape cultivars (Brassica napus).

PubMed

Wu, Zhichao; Zhao, Xiaohu; Sun, Xuecheng; Tan, Qiling; Tang, Yafang; Nie, Zhaojun; Hu, Chengxiao

2015-01-01

Cadmium (Cd) is a toxic metal which harms human health through food chains. The mechanisms underlying Cd accumulation in oilseed rape are still poorly understood. Here, we investigated the physiological and genetic processes involved in Cd uptake and transport of two oilseed rape cultivars (Brassica napus). L351 accumulates more Cd in shoots but less in roots than L338. A scanning ion-selective electrode technique (SIET) and uptake kinetics of Cd showed that roots were not responsible for the different Cd accumulation in shoots since L351 showed a lower Cd uptake ability. However, concentration-dependent and time-dependent dynamics of Cd transport by xylem showed L351 exhibited a superordinate capacity of Cd translocation to shoots. Additionally, the Cd concentrations of shoots and xylem sap showed a great correlation in both cultivars. Furthermore, gene expression levels related to Cd uptake by roots (IRT1) and Cd transport by xylem (HMA2 and HMA4) were consistent with the tendencies of Cd absorption and transport at the physiological level respectively. In other words, L351 had stronger gene expression for Cd transport but lower for Cd uptake. Overall, results revealed that the process of Cd translocation to shoots is a determinative factor for Cd accumulation in shoots, both at physiological and genetic levels. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

Variable effects of arbuscular mycorrhizal fungal inoculation on physiological and molecular measures of root and stomatal conductance of diverse Medicago truncatula accessions.

PubMed

Watts-Williams, Stephanie J; Cavagnaro, Timothy R; Tyerman, Stephen D

2018-06-22

Association with arbuscular mycorrhizal fungi (AMF) can impact on plant water relations; mycorrhizal plants can exhibit increased stomatal conductance (g s ) and root hydraulic conductance (normalised to root dry weight, L o ), and altered expression of aquaporins (AQP). Many factors regulate such responses, however, plant intraspecific diversity effects have yet to be explored. Twenty geographically diverse accessions of Medicago truncatula were inoculated with the AMF Funneliformis mosseae or mock-inoculated, and grown under well-watered conditions. Biomass, g s , shoot nutrient concentrations and mycorrhizal colonisation were measured in all accessions, and L o and gene expression in five accessions. The diverse accessions varied in physiology and gene expression; some accessions were also larger or had higher g s when colonised by F. mosseae. In the five accessions, L o was higher in two accessions when colonised by AMF, and also maintained within a much smaller range than the mock-inoculated plants. Expression of MtPIP1 correlated with both g s and L o , and when plants were more than 3% colonised, mycorrhizal colonisation correlated with L o . Accession and AMF treatments had profound effects on M. truncatula, including several measures of plant water relations. Correlations between response variables, especially between molecular and physiological variables, across genotypes, highlight the findings of this study. This article is protected by copyright. All rights reserved.

7 CFR 51.2 - Terms defined.

Code of Federal Regulations, 2011 CFR

2011-01-01

... resulting from improper handling after packing; progressive pathological, physiological, and virus diseases, including fungal and bacterial roots; and freezing damage which may occur in transit or storage; or any...

Heavy metal accumulation and signal transduction in herbaceous and woody plants: Paving the way for enhancing phytoremediation efficiency.

PubMed

Luo, Zhi-Bin; He, Jiali; Polle, Andrea; Rennenberg, Heinz

2016-11-01

Heavy metal (HM)-accumulating herbaceous and woody plants are employed for phytoremediation. To develop improved strategies for enhancing phytoremediation efficiency, knowledge of the microstructural, physiological and molecular responses underlying HM-accumulation is required. Here we review the progress in understanding the structural, physiological and molecular mechanisms underlying HM uptake, transport, sequestration and detoxification, as well as the regulation of these processes by signal transduction in response to HM exposure. The significance of genetic engineering for enhancing phytoremediation efficiency is also discussed. In herbaceous plants, HMs are taken up by roots and transported into the root cells via transmembrane carriers for nutritional ions. The HMs absorbed by root cells can be further translocated to the xylem vessels and unloaded into the xylem sap, thereby reaching the aerial parts of plants. HMs can be sequestered in the cell walls, vacuoles and the Golgi apparatuses. Plant roots initially perceive HM stress and trigger the signal transduction, thereby mediating changes at the molecular, physiological, and microstructural level. Signaling molecules such as phytohormones, reactive oxygen species (ROS) and nitric oxide (NO), modulate plant responses to HMs via differentially expressed genes, activation of the antioxidative system and coordinated cross talk among different signaling molecules. A number of genes participated in HM uptake, transport, sequestration and detoxification have been functionally characterized and transformed to target plants for enhancing phytoremediation efficiency. Fast growing woody plants hold an advantage over herbaceous plants for phytoremediation in terms of accumulation of high HM-amounts in their large biomass. Presumably, woody plants accumulate HMs using similar mechanisms as herbaceous counterparts, but the processes of HM accumulation and signal transduction can be more complex in woody plants. Copyright © 2016 Elsevier Inc. All rights reserved.

Abiotic stresses modulate expression of major intrinsic proteins in barley (Hordeum vulgare).

PubMed

Ligaba, Ayalew; Katsuhara, Maki; Shibasaka, Mineo; Djira, Gemechis

2011-02-01

In one of the most important crops, barley (Hordeum vulgare L.), gene expression and physiological roles of most major intrinsic proteins (MIPs) remained to be elucidated. Here we studied expression of five tonoplast intrinsic protein isoforms (HvTIP1;2, HvTIP2;1, HvTIP2;2, HvTIP2;3 and HvTIP4;1), a NOD26-like intrinsic protein (HvNIP2;1) and a plasma membrane intrinsic protein (HvPIP2;1) by using the quantitative real-time RT-PCR. Five-day-old seedlings were exposed to abiotic stresses (salt, heavy metals and nutrient deficiency), abscisic acid (ABA) and gibberellic acid (GA) for 24 h. Treatment with 100 mM NaCl, 0.1 mM ABA and 1 mM GA differentially regulated gene expression in roots and shoots. Nitrogen and prolonged P-deficiency downregulated expression of most MIP genes in roots. Intriguingly, gene expression was restored to the values in the control three days after nutrient supply was resumed. Heavy metals (0.2 mM each of Cd, Cu, Zn and Cr) downregulated the transcript levels by 60-80% in roots, whereas 0.2 mM Hg upregulated expressions of most genes in roots. This was accompanied by a 45% decrease in the rate of transpiration. In order to study the physiological role of the MIPs, cDNA of three genes (HvTIP2;1, HvTIP2;3 and HvNIP2;1) have been cloned and heterologous expression was performed in Xenopus laevis oocytes. Osmotic water permeability was determined by a swelling assay. However, no water uptake activity was observed for the three proteins. Hence, the possible physiological role of the proteins is discussed. Copyright © 2010 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Response to non-uniform salinity in the root zone of the halophyte Atriplex nummularia: growth, photosynthesis, water relations and tissue ion concentrations.

PubMed

Bazihizina, Nadia; Colmer, Timothy D; Barrett-Lennard, Edward G

2009-09-01

Soil salinity is often heterogeneous, yet the physiology of halophytes has typically been studied with uniform salinity treatments. An evaluation was made of the growth, net photosynthesis, water use, water relations and tissue ions in the halophytic shrub Atriplex nummularia in response to non-uniform NaCl concentrations in a split-root system. Atriplex nummularia was grown in a split-root system for 21 d, with either the same or two different NaCl concentrations (ranging from 10 to 670 mm), in aerated nutrient solution bathing each root half. Non-uniform salinity, with high NaCl in one root half (up to 670 mm) and 10 mm in the other half, had no effect on shoot ethanol-insoluble dry mass, net photosynthesis or shoot pre-dawn water potential. In contrast, a modest effect occurred for leaf osmotic potential (up to 30 % more solutes compared with uniform 10 mm NaCl treatment). With non-uniform NaCl concentrations (10/670 mm), 90 % of water was absorbed from the low salinity side, and the reduction in water use from the high salinity side caused whole-plant water use to decrease by about 30 %; there was no compensatory water uptake from the low salinity side. Leaf Na(+) and Cl(-) concentrations were 1.9- to 2.3-fold higher in the uniform 670 mm treatment than in the 10/670 mm treatment, whereas leaf K(+) concentrations were 1.2- to 2.0-fold higher in the non-uniform treatment. Atriplex nummularia with one root half in 10 mm NaCl maintained net photosynthesis, shoot growth and shoot water potential even when the other root half was exposed to 670 mm NaCl, a concentration that inhibits growth by 65 % when uniform in the root zone. Given the likelihood of non-uniform salinity in many field situations, this situation would presumably benefit halophyte growth and physiology in saline environments.

Uptake, translocation and physiological effects of magnetic iron oxide (γ-Fe2O3) nanoparticles in corn (Zea mays L.).

PubMed

Li, Junli; Hu, Jing; Ma, Chuanxin; Wang, Yunqiang; Wu, Chan; Huang, Jin; Xing, Baoshan

2016-09-01

Iron oxide nanoparticles (γ-Fe2O3 NPs) have emerged as an innovative and promising method of iron application in agricultural systems. However, the possible toxicity of γ-Fe2O3 NPs and its uptake and translocation require further study prior to large-scale field application. In this study, we investigated uptake and distribution of γ-Fe2O3 NPs in corn (Zea mays L.) and its impacts on seed germination, antioxidant enzyme activity, malondialdehyde (MDA) content, and chlorophyll content were determined. 20 mg/L of γ-Fe2O3 NPs significantly promoted root elongation by 11.5%, and increased germination index and vigor index by 27.2% and 39.6%, respectively. However, 50 and 100 mg/L γ-Fe2O3 NPs remarkably decreased root length by 13.5% and 12.5%, respectively. Additionally, evidence for γ-Fe2O3 NPs induced oxidative stress was exclusively found in the root. Exposures of different concentrations of NPs induced notably high levels of MDA in corn roots, and the MDA levels of corn roots treated by γ-Fe2O3 NPs (20-100 mg/L) were 5-7-fold higher than that observed in the control plants. Meanwhile, the chlorophyll contents were decreased by 11.6%, 39.9% and 19.6%, respectively, upon NPs treatment relative to the control group. Images from fluorescence and transmission electron microscopy (TEM) indicated that γ-Fe2O3 NPs could enter plant roots and migrate apoplastically from the epidermis to the endodermis and accumulate the vacuole. Furthermore, we found that NPs mostly existed around the epidermis of root and no translocation of NPs from roots to shoots was observed. Our results will be highly meaningful on understanding the fate and physiological effects of γ-Fe2O3 NPs in plants. Copyright © 2016 Elsevier Ltd. All rights reserved.

Influence of experimental snow removal on root and canopy physiology of sugar maple trees in a northern hardwood forest

Treesearch

Daniel P. Comerford; Paul G. Schaberg; Pamela H. Templer; Anne M. Socci; John L. Campbell; Kimberly F. Wallin

2013-01-01

Due to projected increases in winter air temperatures in the northeastern USA over the next 100 years, the snowpack is expected to decrease in depth and duration, thereby increasing soil exposure to freezing air temperatures. To evaluate the potential physiological responses of sugar maple (Acer saccharum Marsh.) to a reduced snowpack, we measured...

Quantitation of Cellular Dynamics in Growing Arabidopsis Roots with Light Sheet Microscopy

PubMed Central

Birnbaum, Kenneth D.; Leibler, Stanislas

2011-01-01

To understand dynamic developmental processes, living tissues have to be imaged frequently and for extended periods of time. Root development is extensively studied at cellular resolution to understand basic mechanisms underlying pattern formation and maintenance in plants. Unfortunately, ensuring continuous specimen access, while preserving physiological conditions and preventing photo-damage, poses major barriers to measurements of cellular dynamics in growing organs such as plant roots. We present a system that integrates optical sectioning through light sheet fluorescence microscopy with hydroponic culture that enables us to image, at cellular resolution, a vertically growing Arabidopsis root every few minutes and for several consecutive days. We describe novel automated routines to track the root tip as it grows, to track cellular nuclei and to identify cell divisions. We demonstrate the system's capabilities by collecting data on divisions and nuclear dynamics. PMID:21731697

Physiological responses and tolerance of kenaf (Hibiscus cannabinus L.) exposed to chromium.

PubMed

Ding, Han; Wang, Guodong; Lou, Lili; Lv, Jinyin

2016-11-01

Selection of kenaf species with chromium (Cr) tolerance and exploring the physiological mechanisms involved in Cr tolerance are crucial for application of these species to phyto-remediation. In the present study, a hydroponic experiment was conducted to investigate the variation in two kenaf cultivars, K39-2 and Zhe50-3 under Cr stress. At the same Cr concentration, the tolerance index (TI) of K39-2 was higher than that of Zhe50-3, indicating that K39-2 may be more tolerant to Cr than Zhe50-3. It was also observed that high concentration of chromium was accumulated both in the shoots and the roots of Hibiscus cannabinus L. The leaves of K39-2 accumulated 4760.28mgkg(-1) of dry weight under 1.50mM Cr stress, and the roots accumulated 11,958.33mgkg(-1). Physiological response shows that the antioxidant enzymes' superoxide dismutase (SOD), catalase activity (CAT) and peroxidase (POD) activities increased in the leaves and decreased in roots of the Cr-stressed plants nearly compared to the control. Moreover, the variation of antioxidant enzymes activities indicated Zhe50-3 was more vulnerable than K39-2, and the contents of the non-protein thiol pool (GSH, NPT and PCs) were higher in K39-2 than Zhe50-3 with the increased Cr concentration. Based on the observations above, it can be concluded that the well-coordinated physiological changes confer a greater Cr tolerance to K39-2 than Zhe50-3 under Cr exposure, and Hibiscus cannabinus L. has a great accumulation capacity for chromium. Copyright © 2016 Elsevier Inc. All rights reserved.

Effects on Physiology and Performance of Wearing the Aviator NBC ensemble While Flying the UH-60 Helicopter Flight Simulator in a Controlled Heat Environment.

DTIC Science & Technology

1992-09-01

and collecting and processing data. They were at the front line in interacting with the subjects and maintaining morale. They did an excellent job. They...second for 16 parameter channels, and the data were processed to produce a single root mean square (RMS) error value for each channel appropriate to...represented in the final analysis. Physiological data The physiological data on the VAX were processed by sampling them at 5-minute intervals throughout the

Fine Root Productivity and Turnover of Ectomycorrhizal and Arbuscular Mycorrhizal Tree Species in a Temperate Broad-Leaved Mixed Forest

PubMed Central

Kubisch, Petra; Hertel, Dietrich; Leuschner, Christoph

2016-01-01

Advancing our understanding of tree fine root dynamics is of high importance for tree physiology and forest biogeochemistry. In temperate broad-leaved forests, ectomycorrhizal (EM) and arbuscular mycorrhizal (AM) tree species often are coexisting. It is not known whether EM and AM trees differ systematically in fine root dynamics and belowground resource foraging strategies. We measured fine root productivity (FRP) and fine root turnover (and its inverse, root longevity) of three EM and three AM broad-leaved tree species in a natural cool-temperate mixed forest using ingrowth cores and combined the productivity data with data on root biomass per root orders. FRP and root turnover were related to root morphological traits and aboveground productivity. FRP differed up to twofold among the six coexisting species with larger species differences in lower horizons than in the topsoil. Root turnover varied up to fivefold among the species with lowest values in Acer pseudoplatanus and highest in its congener Acer platanoides. Variation in root turnover was larger within the two groups than between EM and AM species. We conclude that the main determinant of FRP and turnover in this mixed forest is species identity, while the influence of mycorrhiza type seems to be less important. PMID:27617016

Further insights into normal aortic valve function: role of a compliant aortic root on leaflet opening and valve orifice area.

PubMed

Sripathi, Vangipuram Canchi; Kumar, Ramarathnam Krishna; Balakrishnan, Komarakshi R

2004-03-01

This study aims to find the fundamental differences in the mechanism of opening and closing of a normal aortic valve and a valve with a stiff root, using a dynamic finite element model. A dynamic, finite element model with time varying pressure was used in this study. Shell elements with linear elastic properties for the leaflet and root were used. Two different cases were analyzed: (1) normal leaflets inside a compliant root, and (2) normal leaflets inside a stiff root. A compliant aortic root contributes substantially to the smooth and symmetrical leaflet opening with minimal gradients. In contrast, the leaflet opening inside a stiff root is delayed, asymmetric, and wrinkled. However, this wrinkling is not associated with increased leaflet stresses. In compliant roots, the effective valve orifice area can substantially increase because of increased root pressure and transvalvular gradients. In stiff roots this effect is strikingly absent. A compliant aortic root contributes substantially to smooth and symmetrical leaflet opening with minimal gradients. The compliance also contributes much to the ability of the normal aortic valve to increase its effective valve orifice in response to physiologic demands of exercise. This effect is strikingly absent in stiff roots.

Characterization and inhibitive study of gel-grown hydroxyapatite crystals at physiological temperature

NASA Astrophysics Data System (ADS)

Parekh, Bharat; Joshi, Mihir; Vaidya, Ashok

2008-04-01

Hydroxyapatite is very useful for various biomedical applications, due to its chemical similarity with mineralized bone of human. Hydroxyapatite is also responsible for arthropathy (joint disease). In the present study, the growth of hydroxyapatite crystals was carried out by using single-diffusion gel growth technique in silica hydro gel media, at physiological temperature. The growth of hydroxyapatite crystals under slow and controlled environment in gel medium can be simulated in a simple manner to the growth in human body. The crystals, formed in the Liesegang rings, were characterized by powder XRD, FTIR and dielectric study. The diffusion study is also carried out for the hydroxyapatite crystals using the moving boundary model. The inhibitive influence of various Ayurvedic medicinal plant extracts such as Boswellia serrata gum resin , Tribulus terrestris fruits, Rotula aquatica roots, Boerhaavia diffusa roots and Commiphora wightii, on the growth of hydroxyapatite was studied. Roots of R. aquatica and B. diffusa show some inhibition of the hydroxyapatite crystals in vitro. This preclinical study will be helpful to design the therapy for prevention of hydroxyapatite-based ailments.

Physiological response of Arundo donax to cadmium stress by Fourier transform infrared spectroscopy.

PubMed

Yu, Shunhui; Sheng, Li; Zhang, Chunyan; Deng, Hongping

2018-06-05

The present paper deals with the physiological response of the changes in chemical contents of the root, stem and leaf of Arundo donax seedlings stressed by excess cadmium using Fourier transform infrared spectroscopy technique, cadmium accumulation in plant by atomic absorption spectroscopy were tested after different concentrations cadmium stress. The results showed that low cadmium concentrations (<1.0mg/L) the root tissue of Arundo donax uses osmosis of organic substances (e.g. carbohydrates and amino acids) to improve cadmium tolerance. Organic substances (e.g. carbohydrates) that contain a lot of OH in leaf were transported to the root firstly and then could chelate cadmium, but no obvious changes in stems were noted. The cadmium in the shoots (stem and leaf) usually increased with increasing cadmium concentration. These studies demonstrate the potential of Fourier transform infrared spectroscopy technique for the non-invasive and rapid monitoring of the plants stressed with heavy metals, Arundo donax is suitable for phytoremediation of cadmium -contaminated wetland. Copyright © 2018 Elsevier B.V. All rights reserved.

Flavonoids modify root growth and modulate expression of SHORT-ROOT and HD-ZIP III.

PubMed

Franco, Danilo Miralha; Silva, Eder Marques; Saldanha, Luiz Leonardo; Adachi, Sérgio Akira; Schley, Thayssa Rabelo; Rodrigues, Tatiane Maria; Dokkedal, Anne Ligia; Nogueira, Fabio Tebaldi Silveira; Rolim de Almeida, Luiz Fernando

2015-09-01

Flavonoids are a class of distinct compounds produced by plant secondary metabolism that inhibit or promote plant development and have a relationship with auxin transport. We showed that, in terms of root development, Copaifera langsdorffii leaf extracts has an inhibitory effect on most flavonoid components compared with the application of exogenous flavonoids (glycosides and aglycones). These compounds alter the pattern of expression of the SHORT-ROOT and HD-ZIP III transcription factor gene family and cause morpho-physiological alterations in sorghum roots. In addition, to examine the flavonoid auxin interaction in stress, we correlated the responses with the effects of exogenous application of auxin and an auxin transport inhibitor. The results show that exogenous flavonoids inhibit primary root growth and increase the development of lateral roots. Exogenous flavonoids also change the pattern of expression of specific genes associated with root tissue differentiation. These findings indicate that flavonoid glycosides can influence the polar transport of auxin, leading to stress responses that depend on auxin. Copyright © 2015 Elsevier GmbH. All rights reserved.

Fine root morphological traits determine variation in root respiration of Quercus serrata.

PubMed

Makita, Naoki; Hirano, Yasuhiro; Dannoura, Masako; Kominami, Yuji; Mizoguchi, Takeo; Ishii, Hiroaki; Kanazawa, Yoichi

2009-04-01

Fine root respiration is a significant component of carbon cycling in forest ecosystems. Although fine roots differ functionally from coarse roots, these root types have been distinguished based on arbitrary diameter cut-offs (e.g., 2 or 5 mm). Fine root morphology is directly related to physiological function, but few attempts have been made to understand the relationships between morphology and respiration of fine roots. To examine relationships between respiration rates and morphological traits of fine roots (0.15-1.4 mm in diameter) of mature Quercus serrata Murr., we measured respiration of small fine root segments in the field with a portable closed static chamber system. We found a significant power relationship between mean root diameter and respiration rate. Respiration rates of roots<0.4 mm in mean diameter were high and variable, ranging from 3.8 to 11.3 nmol CO2 g(-1) s(-1), compared with those of larger diameter roots (0.4-1.4 mm), which ranged from 1.8 to 3.0 nmol CO2 g(-1) s(-1). Fine root respiration rate was positively correlated with specific root length (SRL) as well as with root nitrogen (N) concentration. For roots<0.4 mm in diameter, SRL had a wider range (11.3-80.4 m g(-1)) and was more strongly correlated with respiration rate than diameter. Our results indicate that a more detailed classification of fine roots<2.0 mm is needed to represent the heterogeneity of root respiration and to evaluate root biomass and root morphological traits.

A new mutant of Arabidopsis disturbed in its roots, right-handed slanting, and gravitropism defines a gene that encodes a heat-shock factor.

PubMed

Fortunati, A; Piconese, S; Tassone, P; Ferrari, S; Migliaccio, F

2008-01-01

A new mutant of Arabidopsis named rha1 is characterized and the gene involved cloned. In roots, the mutant shows minimal right-handed slanting, reduced gravitropic response, notable resistance to 2,4-D, but scarce resistance to IAA and NAA. The roots also show a clear resistance to the auxin transport inhibitors TIBA and NPA, and to ethylene. Other characteristics are a reduced number of lateral roots and reduced size of shoot and root in the seedlings. The gene, cloned through TAIL-PCR, was found to be a heat-shock factor that maps on chromosome 5, close to and above the RFLP marker m61. The rha1 structure, mRNA, and translation product are reported. Since, so far, no other gravitropic mutant has been described as mutated in a heat-shock factor, rha1 belongs to a new group of mutants disturbed in slanting, gravitropism, and auxin physiology. As shown through the RT-PCR analyses of its expression, the gene retains the function connected with heat shock. If the characteristics connected with auxin physiology are considered, however, it is also likely that the gene, as a transcription factor, could be involved in root circumnutation, gravitropic response, and hormonal control of differentiation. Since GUS staining under the gene promoter was localized mainly in the mature tissues, rha1 does not seem to be involved in the first steps of gravitropism, but is rather related to the general response to auxin. The alterations in slanting (mainly due to reduced chiral circumnutation) and gravitropism lead to the supposition that the two processes may have, at least in part, common origins.

Humic acid effect on catalase activity and the generation of reactive oxygen species in corn (Zea mays).

PubMed

Cordeiro, Flávio Couto; Santa-Catarina, Claudete; Silveira, Vanildo; de Souza, Sonia Regina

2011-01-01

Humic acids (HAs) have positive effects on plant physiology, but the molecular mechanisms underlying these events are only partially understood. The induction of root growth and emission of lateral roots (LRs) promoted by exogenous auxin is a natural phenomenon. Exogenous auxins are also associated with HA. Gas nitric oxide (NO) is a secondary messenger produced endogenously in plants. It is associated with metabolic events dependent on auxin. With the application of auxin, NO production is significantly increased, resulting in positive effects on plant physiology. Thus it is possible to evaluate the beneficial effects of the application of HA as an effect of auxin. To investigate the effects of HA the parameters of root growth, Zea mays was studied by evaluating the application of 3 mM C L⁻¹ of HA extracted from Oxisol and 100 µM SNP (sodium nitroprusside) and the NO donor, subject to two N-NO₃⁻, high dose (5.0 mM N-NO₃⁻) and low dose (5.0 mM N-NO₃⁻). Treatments with HA and NO were positively increased, regardless of the N-NO₃⁻ taken, as assessed by fresh weight and dry root, issue of LRs. The effects were more pronounced in the treatment with a lower dose of N-NO₃⁻. Detection of reactive oxygen species (ROS) in vivo and catalase activity were evaluated; these tests were associated with root growth. Under application of the bioactive substances tested, detection of ROS and catalase activity increased, especially in treatments with lower doses of N-NO₃⁻. The results of this experiment indicate that the effects of HA are dependent on ROS generation, which act as a messenger that induces root growth and the emission of LRs.

[Three-dimensional data fusion method for tooth crown and root based on curvature continuity algorithm].

PubMed

Zhao, Y J; Liu, Y; Sun, Y C; Wang, Y

2017-08-18

To explore a three-dimensional (3D) data fusion and integration method of optical scanning tooth crowns and cone beam CT (CBCT) reconstructing tooth roots for their natural transition in the 3D profile. One mild dental crowding case was chosen from orthodontics clinics with full denture. The CBCT data were acquired to reconstruct the dental model with tooth roots by Mimics 17.0 medical imaging software, and the optical impression was taken to obtain the dentition model with high precision physiological contour of crowns by Smart Optics dental scanner. The two models were doing 3D registration based on their common part of the crowns' shape in Geomagic Studio 2012 reverse engineering software. The model coordinate system was established by defining the occlusal plane. crown-gingiva boundary was extracted from optical scanning model manually, then crown-root boundary was generated by offsetting and projecting crown-gingiva boundary to the root model. After trimming the crown and root models, the 3D fusion model with physiological contour crown and nature root was formed by curvature continuity filling algorithm finally. In the study, 10 patients with dentition mild crowded from the oral clinics were followed up with this method to obtain 3D crown and root fusion models, and 10 high qualification doctors were invited to do subjective evaluation of these fusion models. This study based on commercial software platform, preliminarily realized the 3D data fusion and integration method of optical scanning tooth crowns and CBCT tooth roots with a curvature continuous shape transition. The 10 patients' 3D crown and root fusion models were constructed successfully by the method, and the average score of the doctors' subjective evaluation for these 10 models was 8.6 points (0-10 points). which meant that all the fusion models could basically meet the need of the oral clinics, and also showed the method in our study was feasible and efficient in orthodontics study and clinics. The method of this study for 3D crown and root data fusion could obtain an integrate tooth or dental model more close to the nature shape. CBCT model calibration may probably improve the precision of the fusion model. The adaptation of this method for severe dentition crowding and micromaxillary deformity needs further research.

Natural genetic variation of root system architecture from Arabidopsis to Brachypodium: towards adaptive value.

PubMed

Pacheco-Villalobos, David; Hardtke, Christian S

2012-06-05

Root system architecture is a trait that displays considerable plasticity because of its sensitivity to environmental stimuli. Nevertheless, to a significant degree it is genetically constrained as suggested by surveys of its natural genetic variation. A few regulators of root system architecture have been isolated as quantitative trait loci through the natural variation approach in the dicotyledon model, Arabidopsis. This provides proof of principle that allelic variation for root system architecture traits exists, is genetically tractable, and might be exploited for crop breeding. Beyond Arabidopsis, Brachypodium could serve as both a credible and experimentally accessible model for root system architecture variation in monocotyledons, as suggested by first glimpses of the different root morphologies of Brachypodium accessions. Whether a direct knowledge transfer gained from molecular model system studies will work in practice remains unclear however, because of a lack of comprehensive understanding of root system physiology in the native context. For instance, apart from a few notable exceptions, the adaptive value of genetic variation in root system modulators is unknown. Future studies should thus aim at comprehensive characterization of the role of genetic players in root system architecture variation by taking into account the native environmental conditions, in particular soil characteristics.

Measuring the ability of military aircrews to adapt to perceived stressors when undergoing centrifuge training.

PubMed

Wang, Jenhung; Lin, Pei-Chun; Li, Shih-Chin

2014-01-01

This study assessed the ability of military aircrews to adapt to stressors when undergoing centrifuge training and determined what equipment items caused perceived stress and needed to be upgraded. We used questionnaires and the Rasch model to measure aircrew personnel's ability to adapt to centrifuge training. The measurement items were ranked by 611 military aircrew personnel. Analytical results indicated that the majority of the stress perceived by aircrew personnel resulted from the lightproof cockpit without outer reference. This study prioritized the equipment requiring updating as the lightproof cockpit design, the dim lighting of the cockpit, and the pedal design. A significant difference was found between pilot and non-pilot subjects' stress from the pedal design; and considerable association was discernible between the seat angle design and flight hours accrued. The study results provide aviators, astronauts, and air forces with reliable information as to which equipment items need to be urgently upgraded as their present physiological and psychological effects can affect the effectiveness of centrifuge training.

Challenges in tracing the fate and effects of atmospheric polycyclic aromatic hydrocarbon deposition in vascular plants.

PubMed

Desalme, Dorine; Binet, Philippe; Chiapusio, Geneviève

2013-05-07

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic pollutants that raise environmental concerns because of their toxicity. Their accumulation in vascular plants conditions harmful consequences to human health because of their position in the food chain. Consequently, understanding how atmospheric PAHs are taken up in plant tissues is crucial for risk assessment. In this review we synthesize current knowledge about PAH atmospheric deposition, accumulation in both gymnosperms and angiosperms, mechanisms of transfer, and ecological and physiological effects. PAHs emitted in the atmosphere partition between gas and particulate phases and undergo atmospheric deposition on shoots and soil. Most PAH concentration data from vascular plant leaves suggest that contamination occurs by both direct (air-leaf) and indirect (air-soil-root) pathways. Experimental studies demonstrate that PAHs affect plant growth, interfering with plant carbon allocation and root symbioses. Photosynthesis remains the most studied physiological process affected by PAHs. Among scientific challenges, identifying specific physiological transfer mechanisms and improving the understanding of plant-symbiont interactions in relation to PAH pollution remain pivotal for both fundamental and applied environmental sciences.

Electronic working length determination in primary teeth by ProPex and Digital Signal Processing.

PubMed

Nelson-Filho, Paulo; Lucisano, Marcela Pacífico; Leonardo, Mário Roberto; da Silva, Raquel Assed Bezerra; da Silva, Léa Assed Bezerra

2010-12-01

The purpose of this study was to evaluate the accuracy of electronic apex locators Digital Signal Processing (DSP) and ProPex, for root canal length determination in primary teeth. Fifteen primary molars (a total of 34 root canals) were divided into two groups: Group I - without physiological resorption (n = 16); and Group II - with physiological resorption (n = 18). The length of each canal was measured by introducing a file until its tip was visible and then it was retracted 1 mm. For electronic measurement, the devices were set to 1 mm short of the apical resorption. The data were analysed statistically using the intraclass correlation coefficient (ICC). Results showed that the ICC was high for both electronic apex locators in all situations - with (ICC: DSP = 0.82 and Propex = 0.89) or without resorption (ICC: DSP = 0.92 and Propex = 0.90). Both apex locators were extremely accurate in determining the working length in primary teeth, both with or without physiological resorption. © 2010 The Authors. Australian Endodontic Journal © 2010 Australian Society of Endodontology.

Highly diverse endophytes in roots of Cycas bifida (Cycadaceae), an ancient but endangered gymnosperm.

PubMed

Zheng, Ying; Chiang, Tzen-Yuh; Huang, Chao-Li; Gong, Xun

2018-05-01

As an ancient seed plant, cycads are one of the few gymnosperms that develop a root symbiosis with cyanobacteria, which has allowed cycads to cope with harsh geologic and climatic conditions during the evolutionary process. However, the endophytic microbes in cycad roots remain poorly identified. In this study, using next-generation sequencing techniques, we investigated the microbial diversity and composition of both the coralloid and regular roots of Cycas bifida (Dyer) K.D. Hill. Highly diverse endophytic communities were observed in both the coralloid and regular roots. Of the associated bacteria, the top five families were the Nostocaceae, Sinobacteraceae, Bradyrhizobiaceae, Bacillaceae, and Hyphomicrobiaceae. The Nectriaceae, Trichocomaceae, and Incertae sedis were the predominant fungal families in all root samples. A significant difference in the endophytic bacterial community was detected between coralloid roots and regular roots, but no difference was observed between the fungal communities in the two root types. Cyanobacteria were more dominant in coralloid roots than in regular roots. The divergence of cycad root structures and the modified physiological processes may have contributed to the abundance of cyanobionts in coralloid roots. Consequently, the colonization of cyanobacteria inhibits the assemblage of other endophytes. Our results contribute to an understanding of the species diversity and composition of the cycad-endophyte microbiome and provide an abbreviated list of potential ecological roles of the core microbes present.

Controlled environment crop production - Hydroponic vs. lunar regolith

NASA Technical Reports Server (NTRS)

Bugbee, Bruce G.; Salisbury, Frank B.

1989-01-01

The potential of controlled environment crop production in a lunar colony is discussed. Findings on the effects of optimal root-zone and aerial environments derived as part of the NASA CELSS project at Utah State are presented. The concept of growing wheat in optimal environment is discussed. It is suggested that genetic engineering might produce the ideal wheat cultivar for CELSS (about 100 mm in height with fewer leaves). The Utah State University hydroponic system is outlined and diagrams of the system and plant container construction are provided. Ratio of plant mass to solution mass, minimum root-zone volume, maintenance, and pH control are discussed. A comparison of liquid hydrophonic systems and lunar regoliths as substrates for plant growth is provided. The physiological processes that are affected by the root-zone environment are discussed including carbon partitioning, nutrient availability, nutrient absorption zones, root-zone oxygen, plant water potential, root-produced hormones, and rhizosphere pH control.

Rha1, a new mutant of Arabidopsis disturbed in root slanting, gravitropism and auxin physiology.

PubMed

Fortunati, Alessio; Piconese, Silvia; Tassone, Paola; Ferrari, Simone; Migliaccio, Fernando

2008-11-01

A new Arabidopsis mutant is characterized (rha1) that shows, in the roots, reduced right-handed slanting, reduced gravitropism and resistance to 2,4-D, TIBA, NPA and ethylene. It also shows reduced length in the shoot and root, reduced number of lateral roots and shorter siliques. The gene was cloned through TAIL-PCR and resulted in a HSF. Because none of the known gravitropic and auxinic mutants result from damage in a HSF, rha1 seems to belong to a new class of this group of mutants. Quantitative PCR analysis showed that the expression of the gene is increased by heat and cold shock, and by presence of 2,4-D in the media. Study of the expression through the GUS reporter gene revealed increased expression in clinostated and gravistimulated plants, but only in adult tissues, and not in the apical meristems of shoots and roots.

Rha1, a new mutant of Arabidopsis disturbed in root slanting, gravitropism and auxin physiology

PubMed Central

Fortunati, Alessio; Piconese, Silvia; Tassone, Paola; Ferrari, Simone

2008-01-01

A new Arabidopsis mutant is characterized (rha1) that shows, in the roots, reduced right-handed slanting, reduced gravitropism and resistance to 2,4-D, TIBA, NPA and ethylene. It also shows reduced length in the shoot and root, reduced number of lateral roots and shorter siliques. The gene was cloned through TAIL-PCR and resulted in a HSF. Because none of the known gravitropic and auxinic mutants result from damage in a HSF, rha1 seems to belong to a new class of this group of mutants. Quantitative PCR analysis showed that the expression of the gene is increased by heat and cold shock, and by presence of 2,4-D in the media. Study of the expression through the GUS reporter gene revealed increased expression in clinostated and gravistimulated plants, but only in adult tissues, and not in the apical meristems of shoots and roots. PMID:19704429

Thermal measurement of root surface temperatures during application of intracanal laser energy in vitro

NASA Astrophysics Data System (ADS)

Goodis, Harold E.; White, Joel M.; Neev, Joseph

1993-07-01

The use of laser energy to clean, shape, and sterilize a root canal system space involves the generation of heat due to the thermal effect of the laser on the organic tissue contents and dentin walls of that space. If heat generation is above physiologic levels, irreparable damage may occur to the periodontal ligament and surrounding bone. This study measured temperature rise on the outer root surfaces of extracted teeth during intracanal laser exposure. Thirty single rooted, recently extracted teeth free of caries and restorations were accessed pulps extirpated and divided into three groups. Each root canal system was treated with a 1.06 micrometers pulsed Nd:YAG laser with quartz contact probes. Temperatures were recorded for all surfaces (mesial distal, buccal, lingual, apical) with infrared thermography utilizing a detector response time of 1 (mu) sec, sensitivity range (infrared) of 8 to 12 micrometers and a scan rate of 30 frames/sec.

Root developmental adaptation to phosphate starvation: better safe than sorry.

PubMed

Péret, Benjamin; Clément, Mathilde; Nussaume, Laurent; Desnos, Thierry

2011-08-01

Phosphorus is a crucial component of major organic molecules such as nucleic acids, ATP and membrane phospholipids. It is present in soils in the form of inorganic phosphate (Pi), which has low availability and poor mobility. To cope with Pi limitations, plants have evolved complex adaptive responses that include morphological and physiological modifications. This review describes how the model plant Arabidopsis thaliana adapts its root system architecture to phosphate deficiency through inhibition of primary root growth, increase in lateral root formation and growth and production of root hairs, which all promote topsoil foraging. A better understanding of plant adaptation to low phosphate will open the way to increased phosphorus use efficiency by crops. Such an improvement is needed in order to adjust how we manage limited phosphorus stocks and to reduce the disastrous environmental effects of phosphate fertilizers overuse. Copyright © 2011 Elsevier Ltd. All rights reserved.

Root growth and development in response to CO2 enrichment

NASA Technical Reports Server (NTRS)

Day, Frank P., Jr.

1994-01-01

A non-destructive technique (minirhizotron observation tubes) was used to assess the effects of CO2 enrichment on root growth and development in experimental plots in a scrub oak-palmetto community at the Kennedy Space Center. Potential effects of CO2 enrichment on plants have a global significance in light of concerns over increasing CO2 concentrations in the Earth's atmosphere. The study at Kennedy Space Center focused on aboveground physiological responses (photosynthetic efficiency and water use efficiency), effects on process rates (litter decomposition and nutrient turnover), and belowground responses of the plants. Belowground dynamics are an exceptionally important component of total plant response but are frequently ignored due to methodological difficulties. Most methods used to examine root growth and development are destructive and, therefore, severely compromise results. Minirhizotrons allow nondestructive observation and quantification of the same soil volume and roots through time. Root length density and root phenology were evaluated for CO2 effects with this nondestructive technique.

New nitrogen uptake strategy: specialized snow roots.

PubMed

Onipchenko, Vladimir G; Makarov, Mikhail I; van Logtestijn, Richard S P; Ivanov, Viktor B; Akhmetzhanova, Assem A; Tekeev, Dzhamal K; Ermak, Anton A; Salpagarova, Fatima S; Kozhevnikova, Anna D; Cornelissen, Johannes H C

2009-08-01

The evolution of plants has yielded a wealth of adaptations for the acquisition of key mineral nutrients. These include the structure, physiology and positioning of root systems. We report the discovery of specialized snow roots as a plant strategy to cope with the very short season for nutrient uptake and growth in alpine snow-beds, i.e. patches in the landscape that remain snow-covered well into the summer. We provide anatomical, chemical and experimental (15)N isotope tracking evidence that the Caucasian snow-bed plant Corydalis conorhiza forms extensive networks of specialized above-ground roots, which grow against gravity to acquire nitrogen directly from within snow packs. Snow roots capture nitrogen that would otherwise partly run off down-slope over a frozen surface, thereby helping to nourish these alpine ecosystems. Climate warming is changing and will change mountain snow regimes, while large-scale anthropogenic N deposition has increased snow N contents. These global changes are likely to impact on the distribution, abundance and functional significance of snow roots.

FAL Clowes, 1921-2016: a Memoir.

PubMed

Barlow, Peter W

2018-03-04

With the death of Frederick Albert Lionel Clowes on 21 September 2016, plant sciences lost a member of that lineage of experimental morphologists which reaches back to Johann Wolfgang von Goethe. In 1949, he discovered a group of cells at the tip of the beech root apex which were metabolically inert. In 1954, he confirmed generality of this root apex feature and coined the term 'quiescent center'. He continued to study these unique cells throughout next decades up to his last papers published in 1980s. Concept of the quiescent centre of plant roots is one of the milestones in plant cell biology and plant physiology.

Morphological and Physiological Responses of Cotton (Gossypium hirsutum L.) Plants to Salinity

PubMed Central

Zhang, Lei; Ma, Huijuan; Chen, Tingting; Pen, Jun; Yu, Shuxun; Zhao, Xinhua

2014-01-01

Salinization usually plays a primary role in soil degradation, which consequently reduces agricultural productivity. In this study, the effects of salinity on growth parameters, ion, chlorophyll, and proline content, photosynthesis, antioxidant enzyme activities, and lipid peroxidation of two cotton cultivars, [CCRI-79 (salt tolerant) and Simian 3 (salt sensitive)], were evaluated. Salinity was investigated at 0 mM, 80 mM, 160 mM, and 240 mM NaCl for 7 days. Salinity induced morphological and physiological changes, including a reduction in the dry weight of leaves and roots, root length, root volume, average root diameter, chlorophyll and proline contents, net photosynthesis and stomatal conductance. In addition, salinity caused ion imbalance in plants as shown by higher Na+ and Cl− contents and lower K+, Ca2+, and Mg2+ concentrations. Ion imbalance was more pronounced in CCRI-79 than in Simian3. In the leaves and roots of the salt-tolerant cultivar CCRI-79, increasing levels of salinity increased the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR), but reduced catalase (CAT) activity. The activities of SOD, CAT, APX, and GR in the leaves and roots of CCRI-79 were higher than those in Simian 3. CAT and APX showed the greatest H2O2 scavenging activity in both leaves and roots. Moreover, CAT and APX activities in conjunction with SOD seem to play an essential protective role in the scavenging process. These results indicate that CCRI-79 has a more effective protection mechanism and mitigated oxidative stress and lipid peroxidation by maintaining higher antioxidant activities than those in Simian 3. Overall, the chlorophyll a, chlorophyll b, and Chl (a+b) contents, net photosynthetic rate and stomatal conductance, SOD, CAT, APX, and GR activities showed the most significant variation between the two cotton cultivars. PMID:25391141

Small acidic protein 1 and SCFTIR1 ubiquitin proteasome pathway act in concert to induce 2,4-dichlorophenoxyacetic acid-mediated alteration of actin in Arabidopsis roots.

PubMed

Takahashi, Maho; Umetsu, Kana; Oono, Yutaka; Higaki, Takumi; Blancaflor, Elison B; Rahman, Abidur

2017-03-01

2,4-Dichlorophenoxyacetic acid (2,4-D), a functional analogue of auxin, is used as an exogenous source of auxin as it evokes physiological responses like the endogenous auxin, indole-3-acetic acid (IAA). Previous molecular analyses of the auxin response pathway revealed that IAA and 2,4-D share a common mode of action to elicit downstream physiological responses. However, recent findings with 2,4-D-specific mutants suggested that 2,4-D and IAA might also use distinct pathways to modulate root growth in Arabidopsis. Using genetic and cellular approaches, we demonstrate that the distinct effects of 2,4-D and IAA on actin filament organization partly dictate the differential responses of roots to these two auxin analogues. 2,4-D but not IAA altered the actin structure in long-term and short-term assays. Analysis of the 2,4-D-specific mutant aar1-1 revealed that small acidic protein 1 (SMAP1) functions positively to facilitate the 2,4-D-induced depolymerization of actin. The ubiquitin proteasome mutants tir1-1 and axr1-12, which show enhanced resistance to 2,4-D compared with IAA for inhibition of root growth, were also found to have less disrupted actin filament networks after 2,4-D exposure. Consistently, a chemical inhibitor of the ubiquitin proteasome pathway mitigated the disrupting effects of 2,4-D on the organization of actin filaments. Roots of the double mutant aar1-1 tir1-1 also showed enhanced resistance to 2,4-D-induced inhibition of root growth and actin degradation compared with their respective parental lines. Collectively, these results suggest that the effects of 2,4-D on actin filament organization and root growth are mediated through synergistic interactions between SMAP1 and SCF TIR 1 ubiquitin proteasome components. © 2016 The Authors The Plant Journal © 2016 John Wiley & Sons Ltd.

The role of defoliation and root rot pathogen infection in driving the mode of drought-related physiological decline in Scots pine (Pinus sylvestris L.).

PubMed

Aguadé, D; Poyatos, R; Gómez, M; Oliva, J; Martínez-Vilalta, J

2015-03-01

Drought-related tree die-off episodes have been observed in all vegetated continents. Despite much research effort, however, the multiple interactions between carbon starvation, hydraulic failure and biotic agents in driving tree mortality under field conditions are still not well understood. We analysed the seasonal variability of non-structural carbohydrates (NSCs) in four organs (leaves, branches, trunk and roots), the vulnerability to embolism in roots and branches, native embolism (percentage loss of hydraulic conductivity (PLC)) in branches and the presence of root rot pathogens in defoliated and non-defoliated individuals in a declining Scots pine (Pinus sylvestris L.) population in the NE Iberian Peninsula in 2012, which included a particularly dry and warm summer. No differences were observed between defoliated and non-defoliated pines in hydraulic parameters, except for a higher vulnerability to embolism at pressures below -2 MPa in roots of defoliated pines. No differences were found between defoliation classes in branch PLC. Total NSC (TNSC, soluble sugars plus starch) values decreased during drought, particularly in leaves. Defoliation reduced TNSC levels across tree organs, especially just before (June) and during (August) drought. Root rot infection by the fungal pathogen Onnia P. Karst spp. was detected but it did not appear to be associated to tree defoliation. However, Onnia infection was associated with reduced leaf-specific hydraulic conductivity and sapwood depth, and thus contributed to hydraulic impairment, especially in defoliated pines. Infection was also associated with virtually depleted root starch reserves during and after drought in defoliated pines. Moreover, defoliated and infected trees tended to show lower basal area increment. Overall, our results show the intertwined nature of physiological mechanisms leading to drought-induced mortality and the inherent difficulty of isolating their contribution under field conditions. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Single Plant Root System Modeling under Soil Moisture Variation

NASA Astrophysics Data System (ADS)

Yabusaki, S.; Fang, Y.; Chen, X.; Scheibe, T. D.

2016-12-01

A prognostic Virtual Plant-Atmosphere-Soil System (vPASS) model is being developed that integrates comprehensively detailed mechanistic single plant modeling with microbial, atmospheric, and soil system processes in its immediate environment. Three broad areas of process module development are targeted: Incorporating models for root growth and function, rhizosphere interactions with bacteria and other organisms, litter decomposition and soil respiration into established porous media flow and reactive transport models Incorporating root/shoot transport, growth, photosynthesis and carbon allocation process models into an integrated plant physiology model Incorporating transpiration, Volatile Organic Compounds (VOC) emission, particulate deposition and local atmospheric processes into a coupled plant/atmosphere model. The integrated plant ecosystem simulation capability is being developed as open source process modules and associated interfaces under a modeling framework. The initial focus addresses the coupling of root growth, vascular transport system, and soil under drought scenarios. Two types of root water uptake modeling approaches are tested: continuous root distribution and constitutive root system architecture. The continuous root distribution models are based on spatially averaged root development process parameters, which are relatively straightforward to accommodate in the continuum soil flow and reactive transport module. Conversely, the constitutive root system architecture models use root growth rates, root growth direction, and root branching to evolve explicit root geometries. The branching topologies require more complex data structures and additional input parameters. Preliminary results are presented for root model development and the vascular response to temporal and spatial variations in soil conditions.

Hypercementosis and odontogenic epithelial hyperplasia associated with a tooth root remnant mimicking a neoplasm. A case report.

PubMed

Zustin, J; Friedrich, R E

2010-01-01

Hypercementosis presents as painless, single or multiple non-neoplastic cementum formation beyond the physiological limits of the tooth. It often occurs in the apical area of the involved tooth following infection, chemical or mechanical trauma. We report on radiographic and histopathological findings in a single case of late intraosseous hypercementosis and odontogenic epithelial hyperplasia associated with a minute apical tooth root remnant years after its extraction, mimicking a tumour.

On the use of antibiotics to reduce rhizoplane microbial populations in root physiology and ecology investigations

NASA Technical Reports Server (NTRS)

Smart, D. R.; Ferro, A.; Ritchie, K.; Bugbee, B. G.

1995-01-01

No straightforward method exists for separating the proportion of ion exchange and respiration due to rhizoplane microbial organisms from that of root ion exchange and respiration. We examined several antibiotics that might be used for the temporary elimination of rhizoplane bacteria from hydroponically grown wheat roots (Triticum aestivum cv. Veery 10). Each antibiotic was tested for herbicidal activity and plate counts were used to enumerate bacteria and evaluate antibiotic kinetics. Only lactam antibiotics (penicillins and cephalosporins) did not reduce wheat growth rates. Aminoglycosides, the pyrimidine trimethoprim, colistin and rifampicin reduced growth rates substantially. Antibiotics acted slowly, with maximum reductions in rhizoplane bacteria occurring after more than 48 h of exposure. Combinations of nonphytotoxic antibiotics reduced platable rhizoplane bacteria by as much as 98%; however, this was generally a reduction from about 10(9) to 10(6) colony forming units per gram of dry root mass, so that many viable bacteria remained on root surfaces. We present evidence which suggests that insufficient bacterial biomass exists on root surfaces of nonstressed plants grown under well-aerated conditions to quantitatively interfere with root nitrogen absorption measurements.

Analysis of Phosphate Acquisition Efficiency in Different Arabidopsis Accessions

PubMed Central

Narang, Ram A.; Bruene, Asja; Altmann, Thomas

2000-01-01

The morphological and physiological characteristics of Arabidopsis accessions differing in their phosphate acquisition efficiencies (PAEs) when grown on a sparingly soluble phosphate source (hydroxylapatite) were analyzed. A set of 36 accessions was subjected to an initial PAE evaluation following cultivation on synthetic, agarose-solidified media containing potassium phosphate (soluble) or hydroxylapatite (sparingly soluble). From the five most divergent accessions identified in this way, C24, Co, and Cal exhibited high PAEs, whereas Col-0 and Te exhibited low PAEs. These five accessions were analyzed in detail. Significant differences were found in root morphology, phosphate uptake kinetics, organic acid release, rhizosphere acidification, and the ability of roots to penetrate substrates. Long root hairs at high densities, high uptake per unit root length, and high substrate penetration ability in the efficient accessions C24 and Co mediate their high PAEs. The third accession with high PAE, Cal, exhibits a high shoot-to-root ratio, long roots with long root hairs, and rhizosphere acidification. These results are consistent with previous observations and highlight the suitability of using Arabidopsis accessions to identify and isolate genes determining the PAE in plants. PMID:11115894

Lanthanum resulted in unbalance of nutrient elements and disturbance of cell proliferation cycles in V. faba L. seedlings.

PubMed

Wang, Chengrun; Lu, Xianwen; Tian, Yuan; Cheng, Tao; Hu, Lingling; Chen, Fenfen; Jiang, Chuanjun; Wang, Xiaorong

2011-11-01

Effects of lanthanum (La) on mineral nutrients, cell cycles, and root lengthening have been little reported. The present work investigated these physiological responses in roots of Vicia faba seedlings cultivated in La3+-contained solutions for 15 days. The results showed that the increasing contents of La in the roots and leaves contributed to disbalances of contents of Ca, Fe, Cu, Zn, Mg, Mn, P, and K elements, and potential redistributions of some elements in the roots and leaves. These disbalances might be involved in the subsequent alteration of cell cycle phases in the root tips. Low-dose promotion and high-dose inhibition (Hormetic effects) were demonstrated as the dose responses of G0/G1-, S- or G2/M-phase ratios. The cell cycles were most probably arrested at G1/S interphase by La3+ in the root tips. The fact that the root lengths were not consistent with the changes of cell cycle phases suggested that the cell proliferation activities might be masked by other factors (e.g., cell expansion) under long-time exposure to La3+.

Trampling, defoliation and physiological integration affect growth, morphological and mechanical properties of a root-suckering clonal tree.

PubMed

Xu, Liang; Yu, Fei-Hai; van Drunen, Elles; Schieving, Feike; Dong, Ming; Anten, Niels P R

2012-04-01

Grazing is a complex process involving the simultaneous occurrence of both trampling and defoliation. Clonal plants are a common feature of heavily grazed ecosystems where large herbivores inflict the simultaneous pressures of trampling and defoliation on the vegetation. We test the hypothesis that physiological integration (resource sharing between interconnected ramets) may help plants to deal with the interactive effects of trampling and defoliation. In a field study, small and large ramets of the root-suckering clonal tree Populus simonii were subjected to two levels of trampling and defoliation, while connected or disconnected to other ramets. Plant responses were quantified via survival, growth, morphological and stem mechanical traits. Disconnection and trampling increased mortality, especially in small ramets. Trampling increased stem length, basal diameter, fibrous root mass, stem stiffness and resistance to deflection in connected ramets, but decreased them in disconnected ones. Trampling decreased vertical height more in disconnected than in connected ramets, and reduced stem mass in disconnected ramets but not in connected ramets. Defoliation reduced basal diameter, leaf mass, stem mass and leaf area ratio, but did not interact with trampling or disconnection. Although clonal integration did not influence defoliation response, it did alleviate the effects of trampling. We suggest that by facilitating resource transport between ramets, clonal integration compensates for trampling-induced damage to fine roots.

Active summer carbon storage for winter persistence in trees at the cold alpine treeline.

PubMed

Li, Mai-He; Jiang, Yong; Wang, Ao; Li, Xiaobin; Zhu, Wanze; Yan, Cai-Feng; Du, Zhong; Shi, Zheng; Lei, Jingpin; Schönbeck, Leonie; He, Peng; Yu, Fei-Hai; Wang, Xue

2018-03-12

The low-temperature limited alpine treeline is one of the most obvious boundaries in mountain landscapes. The question of whether resource limitation is the physiological mechanism for the formation of the alpine treeline is still waiting for conclusive evidence and answers. We therefore examined non-structural carbohydrates (NSC) and nitrogen (N) in treeline trees (TATs) and low-elevation trees (LETs) in both summer and winter in 11 alpine treeline cases ranging from subtropical monsoon to temperate continental climates across Eurasia. We found that tissue N concentration did not decrease with increasing elevation at the individual treeline level, but the mean root N concentration was lower in TATs than in LETs across treelines in summer. The TATs did not have lower tissue NSC concentrations than LETs in summer. However, the present study with multiple tree species across a large geographical scale, for the first time, revealed a common phenomenon that TATs had significantly lower NSC concentration in roots but not in the aboveground tissues than LETs in winter. Compared with LETs, TATs exhibited both a passive NSC storage in aboveground tissues in excess of carbon demand and an active starch storage in roots at the expense of growth reduction during the growing season. This starch accumulation disappeared in winter. Our results highlight some important aspects of the N and carbon physiology in relation to season in trees at their upper limits. Whether or to what extent the disadvantages of winter root NSC and summer root N level of TATs affect the growth of treeline trees and the alpine treeline formation needs to be further studied.

Aluminum stress signaling in plants

PubMed Central

Baluska, Frantisek; Matsumoto, Hideaki

2009-01-01

Aluminum (Al) toxicity is a major constraint for crop production in acidic soil worldwide. When the soil pH is lower than 5, Al3+ is released to the soil and enters into root tip cell ceases root development of plant. In acid soil with high mineral content, Al is the major cause of phytotoxicity. The target of Al toxicity is the root tip, in which Al exposure causes inhibition of cell elongation and cell division, leading to root stunting accompanied by reduced water and nutrient uptake. A variety of genes have been identified that are induced or repressed upon Al exposure. At tissue level, the distal part of the transition zone is the most sensitive to Al. At cellular and molecular level, many cell components are implicated in the Al toxicity including DNA in nucleus, numerous cytoplastic compounds, mitochondria, the plasma membrane and the cell wall. Although it is difficult to distinguish the primary targets from the secondary effects so far, understanding of the target sites of the Al toxicity is helpful for elucidating the mechanisms by which Al exerts its deleterious effects on root growth. To develop high tolerance against Al stress is the major goal of plant sciences. This review examines our current understanding of the Al signaling with the physiological, genetic and molecular approaches to improve the crop performance under the Al toxicity. New discoveries will open up new avenues of molecular/physiological inquiry that should greatly advance our understanding of Al tolerance mechanisms. Additionally, these breakthroughs will provide new molecular resources for improving the crop Al tolerance via molecular-assisted breeding and biotechnology. PMID:19820334

Remediation mechanisms of mercapto-grafted palygorskite for cadmium pollutant in paddy soil.

PubMed

Liang, Xuefeng; Qin, Xu; Huang, Qingqing; Huang, Rong; Yin, Xiuling; Cai, Yanming; Wang, Lin; Sun, Yuebing; Xu, Yingming

2017-10-01

The immobilization agent was the key factor that determined the success of remediation of heavy metal polluted soil. In this study, mercapto-grafted palygorskite (MP) as a novel and efficient immobilization agent was utilized for the remediation of Cd-polluted paddy soil in pot trials, and the remediation mechanisms were investigated in the aspect of soil chemistry and plant physiology with different rice cultivars as model plants. Mercapto-grafted palygorskite at applied doses of 0.1-0.3% could reduce Cd contents of brown rice and straws of different cultivars significantly. Both reduced DTPA-extractable Cd contents in rhizosphere and non-rhizosphere soil and decreasing Cd contents in iron plaques on rice root surfaces confirmed that MP was an efficient immobilization agent for Cd pollutant in paddy soil. In the aspect of soil chemistry, the pH values of rhizosphere and non-rhizosphere soils had no statistical changes in the MP treatment groups, but their zeta potentials decreased obviously, indicating that MP could enhance the fixation or sorption of Cd on soil compositions. In the aspect of antioxidant system, MP could increase POD activity of rice roots significantly to alleviate the stress of Cd to roots, and resulted in the decrease of T-AOC, SOD, and CAT activities of rice roots of the selected cultivars. MP had no inhabitation or enhancement effects on TSH of rice roots but enhance the contents of MTs and NPT to binding Cd to complete detoxification process. MP as a novel and efficient immobilization agent could complete the remediation effects through soil chemistry and plant physiological mechanisms.

Variable conductivity and embolism in roots, trunks and branches of tree species growing under future atmospheric CO2 concentration (DUKE FACE site): impacts on whole-plant hydraulic performance and carbon assimilation

NASA Astrophysics Data System (ADS)

domec, J.; Palmroth, S.; Oren, R.; Johnson, D. M.; Ward, E. J.; McCulloh, K.; Gonzalez, C.; Warren, J.

2013-12-01

Anatomical and physiological acclimation to water stress of the tree hydraulic system involves tradeoffs between maintenance of stomatal conductance and loss of hydraulic conductivity, with short-term impacts on photosynthesis and long-term consequences to survival and growth. Here we study the role of variations in root, trunk and branch maximum hydraulic specific conductivity (Ks-max) under high and low soil moisture in determining whole-tree hydraulic conductance (Ktree) and in mediating stomatal control of gas exchange in loblolly pine trees growing under ambient and elevated CO2 (CO2a and CO2e). We hypothesized that Ktree would adjust to CO2e, through an increase in root and branch Ks-max in response to anatomical adjustments. Embolism in roots explained the loss of Ktree and therefore indirectly constituted a hydraulic signal involved in stomatal regulation and in the reduction of canopy conductance and carbon assimilation. Across roots, trunk and branches, the increase in Ks-max was associated with a decrease resistance to drought, a consequence of structural acclimation such as larger conduits and lower wood density. In loblolly pine, higher xylem dysfunction under CO2e might impact tree performance in a future climate when increased evaporative demand could cause a greater loss of hydraulic function. The results contributed to our knowledge of the physiological and morphological mechanisms underpinning the responses of tree species to drought and more generally to global change.

Biochemical and molecular characterization of rice (Oryza sativa L.) roots forming a barrier to radial oxygen loss.

PubMed

Kulichikhin, Konstantin; Yamauchi, Takaki; Watanabe, Kohtaro; Nakazono, Mikio

2014-10-01

The formation of a barrier to radial oxygen (O2 ) loss (ROL) in the root is an important adaptation of plants to root flooding, but the biochemical changes in plant roots where the barrier is formed are unclear. In this study, we analysed metabolic profiles and gene expression profiles in roots of rice (Oryza sativa L.) plants grown under stagnant deoxygenated conditions, which induce suberization in the outer cell layers of the roots and formation of barrier to ROL. Under these conditions, two distinctive biochemical features of the roots were the accumulations of malic acid and very long chain fatty acids (VLCFAs). We also showed that the expressions of some genes encoding plastid-localized enzymes, which convert malic acid to acetyl coenzyme A (AcCoA), were simultaneously up-regulated under stagnant conditions. The expression levels of these genes in specific root tissues isolated by laser microdissection suggested that malic acid is converted to AcCoA predominantly in the plastids in the outer cell layers of rice roots. We propose that the physiological role of malic acid accumulation in rice roots grown under stagnant conditions is to provide a substrate for the biosynthesis of fatty acids, which, in turn, are used in the biosynthesis of suberin. © 2014 John Wiley & Sons Ltd.

Gene Networks Involved in Hormonal Control of Root Development in Arabidopsis thaliana: A Framework for Studying Its Disturbance by Metal Stress

PubMed Central

De Smet, Stefanie; Cuypers, Ann; Vangronsveld, Jaco; Remans, Tony

2015-01-01

Plant survival under abiotic stress conditions requires morphological and physiological adaptations. Adverse soil conditions directly affect root development, although the underlying mechanisms remain largely to be discovered. Plant hormones regulate normal root growth and mediate root morphological responses to abiotic stress. Hormone synthesis, signal transduction, perception and cross-talk create a complex network in which metal stress can interfere, resulting in root growth alterations. We focus on Arabidopsis thaliana, for which gene networks in root development have been intensively studied, and supply essential terminology of anatomy and growth of roots. Knowledge of gene networks, mechanisms and interactions related to the role of plant hormones is reviewed. Most knowledge has been generated for auxin, the best-studied hormone with a pronounced primary role in root development. Furthermore, cytokinins, gibberellins, abscisic acid, ethylene, jasmonic acid, strigolactones, brassinosteroids and salicylic acid are discussed. Interactions between hormones that are of potential importance for root growth are described. This creates a framework that can be used for investigating the impact of abiotic stress factors on molecular mechanisms related to plant hormones, with the limited knowledge of the effects of the metals cadmium, copper and zinc on plant hormones and root development included as case example. PMID:26287175

Nitrate induction of root hair density is mediated by TGA1/TGA4 and CPC transcription factors in Arabidopsis thaliana.

PubMed

Canales, Javier; Contreras-López, Orlando; Álvarez, José M; Gutiérrez, Rodrigo A

2017-10-01

Root hairs are specialized cells that are important for nutrient uptake. It is well established that nutrients such as phosphate have a great influence on root hair development in many plant species. Here we investigated the role of nitrate on root hair development at a physiological and molecular level. We showed that nitrate increases root hair density in Arabidopsis thaliana. We found that two different root hair defective mutants have significantly less nitrate than wild-type plants, suggesting that in A. thaliana root hairs have an important role in the capacity to acquire nitrate. Nitrate reductase-null mutants exhibited nitrate-dependent root hair phenotypes comparable with wild-type plants, indicating that nitrate is the signal that leads to increased formation of root hairs. We examined the role of two key regulators of root hair cell fate, CPC and WER, in response to nitrate treatments. Phenotypic analyses of these mutants showed that CPC is essential for nitrate-induced responses of root hair development. Moreover, we showed that NRT1.1 and TGA1/TGA4 are required for pathways that induce root hair development by suppression of longitudinal elongation of trichoblast cells in response to nitrate treatments. Our results prompted a model where nitrate signaling via TGA1/TGA4 directly regulates the CPC root hair cell fate specification gene to increase formation of root hairs in A. thaliana. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

[Research advances in mechanism of high phosphorus use efficiency of plants].

PubMed

Ma, Xiangqing; Liang, Xia

2004-04-01

Phosphorus deficiency is one of the main factors influencing agricultural and forestry productions. Fertilization and soil improvement are the major measures to meet the demand of phosphorus for crops in traditional agriculture and forestry management. Recently, the plants with high phosphorus use efficiency have been discovered to replace the traditional measures to improve phosphorus use efficiency of crops. This paper reviewed the research advances in the morphological, physiological and genetics mechanisms of plants with high phosphorus use efficiency. There were three mechanisms for the plants with high phosphorus use efficiency to grow under phosphorus stress: (1) under low phosphorus stress, the root morphology would change (root system grew fast, root axes became small, the number and density of lateral root increased) and more photosynthesis products would transport from the crown to the root, (2) under low phosphorus stress, plant root exudation increased, mycorrhizae invaded into root system, the feature of root absorption kinetics changed, and the internal phosphorus cycling of plant reinforced to tolerate phosphorus deficiency, and (3) under long selection stress of low phosphorus, some plants would form the genetic properties of phosphorus nutrition that could exploit the hardly soluble phosphorus in the soil.

Regulation of nitrogen uptake and assimilation: Effects of nitrogen source and root-zone and aerial environment on growth and productivity of soybean

NASA Technical Reports Server (NTRS)

Raper, C. David, Jr.

1994-01-01

The interdependence of root and shoot growth produces a functional equilibrium as described in quantitative terms by numerous authors. It was noted that bean seedlings grown in a constant environment tended to have a constant distribution pattern of dry matter between roots and leaves characteristic of the set of environmental conditions. Disturbing equilibrium resulted in a change in relative growth of roots and leaves until the original ratio was restored. To define a physiological basis for regulation of nitrogen uptake within the balance between root and shoot activities, the authors combined a partioning scheme and a utilization priority assumption in which: (1) all carbon enters the plant through photosynthesis in leaves and all nitrogen enters the plant through active uptake by roots, (2) nitrogen uptake by roots and secretion into the xylem for transport to the shoots are active processes, (3) availability of exogenous nitrogen determines concentration of soluble carbohydrates within the roots, (4) leaves are a source and a sink for carbohydrates, and (5) the requirement for nitrogen by leaf growth is proportionally greater during initiation and early expansion than during later expansion.

Linking root hydraulic properties to carbon allocation patterns in annual plant

NASA Astrophysics Data System (ADS)

Hosseini, A.; Ewers, B. E.; Adjesiwor, A. T.; Kniss, A. R.

2017-12-01

Incorporation of root structure and function into biophysical models is an important tool to predict plant water and nutrient uptake from the soil, plant carbon (C) assimilation, partitioning and release to the soils. Most of the models describing root water uptake (RWU) are based on semi-empirical (i.e. built on physiological hypotheses, but still combined with empirical functions) approaches and hydraulic parameters involved are hardly available. Root conductance is essential to define the interaction between soil-to-root and canopy-to-atmosphere. Also root hydraulic limitations to water flow can impact gas exchange rates and plant biomass partitioning. In this study, sugar beet (B. vulgaris) seeds under two treatments, grass (Kentucky bluegrass) and no grass (control), were planted in 19 L plastic buckets in June 2016. Photosynthetic characteristics (e.g. gas exchange and chlorophyll fluorescence), leaf morphology and anatomy, root morphology and above and below ground biomass of the plants was monitored at 15, 30, 50, 70 and 90 days after planting (DAP). Further emphasis was placed on the limits to water flow by coupling of hydraulic conductance (k) whole root-system with water relation parameters and gas exchange rates in fully established plants.

Toxicity of silver nanoparticles to Arabidopsis: Inhibition of root gravitropism by interfering with auxin pathway.

PubMed

Sun, Juzhi; Wang, Likai; Li, Shuang; Yin, Liyan; Huang, Jin; Chen, Chunli

2017-10-01

Impacts of polyvinylpyrrolidine-coated silver nanoparticles (AgNPs) on root gravitropism in Arabidopsis thaliana were investigated at the physiological, cellular, and molecular levels. Our results showed that AgNPs were taken up by the root and primarily localized at the cell wall and intercellular spaces. Root gravitropism was inhibited by exposure to AgNPs, and the inhibition in root gravitropism caused by exposure to AgNPs exhibited a dose-response relationship. Auxin accumulation was reduced in the root tips because of exposure to AgNPs. However, increased indole-3-acetic acid level could not rescue the inhibition of root gravitropism. Real-time polymerase chain reaction showed significant downregulation of expression of auxin receptor-related genes, which is the TIR1/AFB family of F-box proteins including AFB1, AFB2, AFB3, AFB5, and TIR1. Therefore, the present study suggests that AgNPs have toxicity to the model plant A. thaliana as shown by inhibition of root gravitropism along with a reduction in auxin accumulation and expression of auxin receptors. Environ Toxicol Chem 2017;36:2773-2780. © 2017 SETAC. © 2017 SETAC.

Silicon enhances suberization and lignification in roots of rice (Oryza sativa).

PubMed

Fleck, Alexander T; Nye, Thandar; Repenning, Cornelia; Stahl, Frank; Zahn, Marc; Schenk, Manfred K

2011-03-01

The beneficial element silicon (Si) may affect radial oxygen loss (ROL) of rice roots depending on suberization of the exodermis and lignification of sclerenchyma. Thus, the effect of Si nutrition on the oxidation power of rice roots, suberization and lignification was examined. In addition, Si-induced alterations of the transcript levels of 265 genes related to suberin and lignin synthesis were studied by custom-made microarray and quantitative Real Time-PCR. Without Si supply, the oxidation zone of 12 cm long adventitious roots extended along the entire root length but with Si supply the oxidation zone was restricted to 5 cm behind the root tip. This pattern coincided with enhanced suberization of the exodermis and lignification of sclerenchyma by Si supply. Suberization of the exodermis started, with and without Si supply, at 4-5 cm and 8-9 cm distance from the root tip (drt), respectively. Si significantly increased transcript abundance of 12 genes, while two genes had a reduced transcript level. A gene coding for a leucine-rich repeat protein exhibited a 25-fold higher transcript level with Si nutrition. Physiological, histochemical, and molecular-biological data showing that Si has an active impact on rice root anatomy and gene transcription is presented here.

Aluminium tolerance of root hairs underlies genotypic differences in rhizosheath size of wheat (Triticum aestivum) grown on acid soil.

PubMed

Delhaize, Emmanuel; James, Richard A; Ryan, Peter R

2012-08-01

We found significant genetic variation in the ability of wheat (Triticum aestivum) to form rhizosheaths on acid soil and assessed whether differences in aluminium (Al(3+) ) tolerance of root hairs between genotypes was the physiological basis for this genetic variation. A method was developed to rapidly screen rhizosheath size in a range of wheat genotypes. Backcrossed populations were generated from cv Fronteira (large rhizosheath) using cv EGA-Burke (small rhizosheath) as the recurrent parent. A positive correlation existed between rhizosheath size on acid soil and root hair length. In hydroponic experiments, root hairs of the backcrossed lines with large rhizosheaths were more tolerant of Al(3+) toxicity than the backcrossed lines with small rhizosheaths. We conclude that greater Al(3+) tolerance of root hairs underlies the larger rhizosheath of wheat grown on acid soil. Tolerance of the root hairs to Al(3+) was largely independent of the TaALMT1 gene which suggests that different genes encode the Al(3+) tolerance of root hairs. The maintenance of longer root hairs in acid soils is important for the efficient uptake of water and nutrients. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

Response to non-uniform salinity in the root zone of the halophyte Atriplex nummularia: growth, photosynthesis, water relations and tissue ion concentrations

PubMed Central

Bazihizina, Nadia; Colmer, Timothy D.; Barrett-Lennard, Edward G.

2009-01-01

Background and Aims Soil salinity is often heterogeneous, yet the physiology of halophytes has typically been studied with uniform salinity treatments. An evaluation was made of the growth, net photosynthesis, water use, water relations and tissue ions in the halophytic shrub Atriplex nummularia in response to non-uniform NaCl concentrations in a split-root system. Methods Atriplex nummularia was grown in a split-root system for 21 d, with either the same or two different NaCl concentrations (ranging from 10 to 670 mm), in aerated nutrient solution bathing each root half. Key Results Non-uniform salinity, with high NaCl in one root half (up to 670 mm) and 10 mm in the other half, had no effect on shoot ethanol-insoluble dry mass, net photosynthesis or shoot pre-dawn water potential. In contrast, a modest effect occurred for leaf osmotic potential (up to 30 % more solutes compared with uniform 10 mm NaCl treatment). With non-uniform NaCl concentrations (10/670 mm), 90 % of water was absorbed from the low salinity side, and the reduction in water use from the high salinity side caused whole-plant water use to decrease by about 30 %; there was no compensatory water uptake from the low salinity side. Leaf Na+ and Cl− concentrations were 1·9- to 2·3-fold higher in the uniform 670 mm treatment than in the 10/670 mm treatment, whereas leaf K+ concentrations were 1·2- to 2·0-fold higher in the non-uniform treatment. Conclusions Atriplex nummularia with one root half in 10 mm NaCl maintained net photosynthesis, shoot growth and shoot water potential even when the other root half was exposed to 670 mm NaCl, a concentration that inhibits growth by 65 % when uniform in the root zone. Given the likelihood of non-uniform salinity in many field situations, this situation would presumably benefit halophyte growth and physiology in saline environments. PMID:19556265

Physiological and biochemical responses of Ricinus communis seedlings to different temperatures: a metabolomics approach.

PubMed

Ribeiro, Paulo Roberto; Fernandez, Luzimar Gonzaga; de Castro, Renato Delmondez; Ligterink, Wilco; Hilhorst, Henk W M

2014-08-12

Compared with major crops, growth and development of Ricinus communis is still poorly understood. A better understanding of the biochemical and physiological aspects of germination and seedling growth is crucial for the breeding of high yielding varieties adapted to various growing environments. In this context, we analysed the effect of temperature on growth of young R. communis seedlings and we measured primary and secondary metabolites in roots and cotyledons. Three genotypes, recommended to small family farms as cash crop, were used in this study. Seedling biomass was strongly affected by the temperature, with the lowest total biomass observed at 20°C. The response in terms of biomass production for the genotype MPA11 was clearly different from the other two genotypes: genotype MPA11 produced heavier seedlings at all temperatures but the root biomass of this genotype decreased with increasing temperature, reaching the lowest value at 35°C. In contrast, root biomass of genotypes MPB01 and IAC80 was not affected by temperature, suggesting that the roots of these genotypes are less sensitive to changes in temperature. In addition, an increasing temperature decreased the root to shoot ratio, which suggests that biomass allocation between below- and above ground parts of the plants was strongly affected by the temperature. Carbohydrate contents were reduced in response to increasing temperature in both roots and cotyledons, whereas amino acids accumulated to higher contents. Our results show that a specific balance between amino acids, carbohydrates and organic acids in the cotyledons and roots seems to be an important trait for faster and more efficient growth of genotype MPA11. An increase in temperature triggers the mobilization of carbohydrates to support the preferred growth of the aerial parts, at the expense of the roots. A shift in the carbon-nitrogen metabolism towards the accumulation of nitrogen-containing compounds seems to be the main biochemical response to support growth at higher temperatures. The biochemical changes observed in response to the increasing temperature provide leads into understanding plant adaptation to harsh environmental conditions, which will be very helpful in developing strategies for R. communis crop improvement research.

Chromium toxicity tolerance of Solanum nigrum L. and Parthenium hysterophorus L. plants with reference to ion pattern, antioxidation activity and root exudation.

PubMed

UdDin, Islam; Bano, Asghari; Masood, Sajid

2015-03-01

Chromium (Cr), being a highly toxic metal, adversely affects the mineral uptake and metabolic processes in plants when present in excess. The current study was aimed at investigating the Cr accumulation in various plant tissues and its relation to the antioxidation activity and root exudation. Plants were grown in soil spiked with different concentrations of Cr for three weeks in pots and analysed for different growth, antioxidants and ion attributes. Furthermore, plants treated with different concentrations of Cr in pots were shifted to rhizobox-like system for 48h and organic acids were monitored in the mucilage dissolved from the plant root surface, mirroring rhizospheric solution. The results revealed that the Cr application at 1mM increased the shoot fresh and dry weight and root dry weight of Solanum nigrum, whereas the opposite was observed for Parthenium hysterophorus when compared with lower levels of Cr (0.5mM) or control treatment. In both plant species, Cr and Cl concentrations were increased while Ca, Mg and K concentrations in root, shoot and root exudates were decreased with increasing levels of Cr. Higher levels of Cr treatments enhanced the activities of SOD, POD and proline content in leaves of S. nigrum, whereas lower levels of Cr treatment were found to have stimulatory effects in P. hysterophorus. P. hysterophorus exhibited highest exudation of organic acid contents. With increasing levels of Cr treatments, citric acid concentration in root exudates increased by 35% and 44% in S. nigrum, whereas 20% and 76% in P. hysterophorus. Cr toxicity was responsible for the shoot growth reduction of S. nigrum and P. hysterophorus, however, shoot growth response was different at different levels of applied Cr. Consequently, Cr stress negatively altered the plant physiology and biochemistry. However, the enhanced antioxidant production, Cl uptake and root exudation are the physiological and biochemical indicators for the plant adaptations in biotic systems polluted with Cr. Copyright © 2014 Elsevier Inc. All rights reserved.

Relationships between Nutrient Heterogeneity, Root Growth, and Hormones: Evidence for Interspecific Variation

PubMed Central

Dong, Jia; Jones, Robert H.; Mou, Pu

2018-01-01

(1) Background: Plant roots respond to nutrients through root architecture that is regulated by hormones. Strong inter-specific variation in root architecture has been well documented, but physiological mechanisms that may control the variation have not. (2) Methods: We examined correlations between root architecture and hormones to seek clues on mechanisms behind root foraging behavior. In the green house at Beijing Normal University, hydroponic culture experiments were used to examine the root responses of four species—Callistephus chinensis, Solidago canadensis, Ailanthus altissima, Oryza sativa—to two nitrogen types (NO3− or NH4+), three nitrogen concentrations (low, medium, and high concentrations of 0.2, 1, and 18 mM, respectively) and two ways of nitrogen application (stable vs. variable). The plants were harvested after 36 days to measure root mass, 1st order root length, seminal root length for O. sativa, density of the 1st order laterals, seminal root number for O. sativa, the inter-node length of the 1st order laterals, and root hormone contents of indole-3-acetic acid, abscisic acid, and cytokinins (zeatin + zeatinriboside). (3) Results: Species differed significantly in their root architecture responses to nitrogen treatments. They also differed significantly in hormone responses to the nitrogen treatments. Additionally, the correlations between root architecture and hormone responses were quite variable across the species. Each hormone had highly species-specific relationships with root responses. (4) Conclusions: Our finding implies that a particular root foraging behavior is probably not controlled by the same biochemical pathway in all species. PMID:29495558

Distinct modes of adventitious rooting in Arabidopsis thaliana.

PubMed

Correa, L da Rocha; Troleis, J; Mastroberti, A A; Mariath, J E A; Fett-Neto, A G

2012-01-01

The literature describes different rooting protocols for Arabidopsis thaliana as models to study adventitious rooting, and results are generally perceived as comparable. However, there is a lack of investigations focusing on the distinct features, advantages and limitations of each method in the study of adventitious rooting with both wild-type (WT) ecotypes and their respective mutants. This investigation was undertaken to evaluate the adventitious rooting process in three different experimental systems, all using A. thaliana, analysing the same rooting parameters after transient exposure to auxin (indole-3-acetic acid) and control conditions: excised leaves, de-rooted plants and etiolated seedlings. The founding tissues and sites of origin of roots differed depending on the system used, whereas all rooting patterns were of the direct type (i.e., without callus formation). None of the systems had an absolute requirement for exogenous auxin, although rooting was enhanced by this phytohormone, with the exception of de-rooted plants, which had adventitious rooting strongly inhibited by exogenous auxin. Root elongation was much favoured in isolated leaves. Auxin-overproducing mutants could not be used in the detached leaf system due to precocious senescence; in the de-rooted plant system, these mutants had a WT-like rooting response, whereas the expression of the 'rooty' phenotype was only evident in the etiolated seedling system. Adventitious rooting of etiolated WT seedlings in the presence of exogenous auxin was inhibited by exogenous flavonoids, which act as auxin transport inhibitors; surprisingly, the flavonoid-deficient mutant chs had a lower rooting response compared to WT. Although Arabidopsis is an excellent model system to study adventitious rooting, physiological and developmental responses differed significantly, underlining the importance of avoiding data generalisation on rooting responses derived from different experimental systems with this species. © 2011 German Botanical Society and The Royal Botanical Society of the Netherlands.

Root-derived auxin contributes to the phosphorus-deficiency-induced cluster-root formation in white lupin (Lupinus albus).

PubMed

Meng, Zhi Bin; You, Xue Di; Suo, Dong; Chen, Yun Long; Tang, Caixian; Yang, Jian Li; Zheng, Shao Jian

2013-08-01

Formation of cluster roots is a typical morphological response to phosphorus (P) deficiency in white lupin (Lupinus albus), but its physiological and molecular mechanisms are still unclear. We investigated the role of auxin in the initiation of cluster roots by distinguishing the sources of auxin, measuring the longitudinal distribution patterns of free indole-3-acetic acid (IAA) along the root and the related gene expressions responsible for polar auxin transport (PAT) in different developmental stages of cluster roots. We found that removal of shoot apex or primary root apex and application of auxin-influx or -efflux transport inhibitors, 3-chloro-4-hydroxyphenylacetic acid, N-1-naphthylphthalamic acid and 2,3,5-triiodobenzoic acid, to the stem did not affect the number of cluster roots and the free-IAA concentration in the roots of P-deficient plants, but when these inhibitors were applied directly to the growth media, the cluster-root formation was greatly suppressed, suggesting the fundamental role of root-derived IAA in cluster-root formation. The concentration of free IAA in the roots was higher in P-deficient plants than in P-adequate ones, and the highest in the lateral-root apex and the lowest in the mature cluster roots. Meanwhile the expression patterns of LaAUX1, LaPIN1 and LaPIN3 transcripts related to PAT was consistent with concentrations of free IAA along the lateral root, indicating the contribution of IAA redistribution in the cluster-root development. We proposed that root-derived IAA plays a direct and important role in the P-deficiency-induced formation of cluster roots. Copyright © Physiologia Plantarum 2012.

Abscisic Acid Regulation of Root Hydraulic Conductivity and Aquaporin Gene Expression Is Crucial to the Plant Shoot Growth Enhancement Caused by Rhizosphere Humic Acids.

PubMed

Olaetxea, Maite; Mora, Verónica; Bacaicoa, Eva; Garnica, María; Fuentes, Marta; Casanova, Esther; Zamarreño, Angel M; Iriarte, Juan C; Etayo, David; Ederra, Iñigo; Gonzalo, Ramón; Baigorri, Roberto; García-Mina, Jose M

2015-12-01

The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments using cucumber (Cucumis sativus) plants show that the shoot growth enhancement caused by a structurally well-characterized humic acid with sedimentary origin is functionally associated with significant increases in abscisic acid (ABA) root concentration and root hydraulic conductivity. Complementary experiments involving a blocking agent of cell wall pores and water root transport (polyethylenglycol) show that increases in root hydraulic conductivity are essential in the shoot growth-promoting action of the model humic acid. Further experiments involving an inhibitor of ABA biosynthesis in root and shoot (fluridone) show that the humic acid-mediated enhancement of both root hydraulic conductivity and shoot growth depended on ABA signaling pathways. These experiments also show that a significant increase in the gene expression of the main root plasma membrane aquaporins is associated with the increase of root hydraulic conductivity caused by the model humic acid. Finally, experimental data suggest that all of these actions of model humic acid on root functionality, which are linked to its beneficial action on plant shoot growth, are likely related to the conformational structure of humic acid in solution and its interaction with the cell wall at the root surface. © 2015 American Society of Plant Biologists. All Rights Reserved.

Production of glucosinolates, phenolic compounds and associated gene expression profiles of hairy root cultures in turnip (Brassica rapa ssp. rapa).

PubMed

Chung, Ill-Min; Rekha, Kaliyaperumal; Rajakumar, Govindasamy; Thiruvengadam, Muthu

2016-12-01

Turnip (Brassica rapa ssp. rapa) is an important vegetable crop producing glucosinolates (GSLs) and phenolic compounds. The GSLs, phenolic compound contents and transcript levels in hairy root cultures, as well as their antioxidant, antimicrobial and anticancer activity were studied in turnip. Transgenic hairy root lines were confirmed by polymerase chain reaction (PCR) and reverse transcription-PCR. GSLs levels (glucoallysin, glucobrassicanapin, gluconasturtiin, glucobrassicin, 4-methoxyglucobrassicin, neoglucobrassicin and 4-hydroxyglucobrassicin) and their gene expression levels (BrMYB28, BrMYB29, BrMYB34, BrMYB51, BrMYB122, CYP79 and CYP83) significantly increased in hairy roots compared with that in non-transformed roots. Furthermore, hairy roots efficiently produced several important individual phenolic compounds (flavonols, hydroxybenzoic and hydroxycinnamic acids). Colorimetric analysis revealed that the highest levels of total phenol, flavonoid contents, and their gene expression levels (PAL, CHI and FLS) in hairy roots than non-transformed roots. Our study provides beneficial information on the molecular and physiological active processes that are associated with the phytochemical content and biosynthetic gene expression in turnip. Moreover, antioxidant activity, as measured by DPPH scavenging activity, reducing potential, phosphomolybdenum and ferrous ion chelating ability assays was significantly higher in hairy roots. Hairy root extracts exhibited higher antimicrobial activity against bacterial and fungal species. The extract of hairy roots showed inhibition of human breast and colon cancer cell lines.

Abscisic Acid Regulation of Root Hydraulic Conductivity and Aquaporin Gene Expression Is Crucial to the Plant Shoot Growth Enhancement Caused by Rhizosphere Humic Acids1

PubMed Central

Bacaicoa, Eva; Garnica, María; Fuentes, Marta; Casanova, Esther; Etayo, David; Ederra, Iñigo; Gonzalo, Ramón

2015-01-01

The physiological and metabolic mechanisms behind the humic acid-mediated plant growth enhancement are discussed in detail. Experiments using cucumber (Cucumis sativus) plants show that the shoot growth enhancement caused by a structurally well-characterized humic acid with sedimentary origin is functionally associated with significant increases in abscisic acid (ABA) root concentration and root hydraulic conductivity. Complementary experiments involving a blocking agent of cell wall pores and water root transport (polyethylenglycol) show that increases in root hydraulic conductivity are essential in the shoot growth-promoting action of the model humic acid. Further experiments involving an inhibitor of ABA biosynthesis in root and shoot (fluridone) show that the humic acid-mediated enhancement of both root hydraulic conductivity and shoot growth depended on ABA signaling pathways. These experiments also show that a significant increase in the gene expression of the main root plasma membrane aquaporins is associated with the increase of root hydraulic conductivity caused by the model humic acid. Finally, experimental data suggest that all of these actions of model humic acid on root functionality, which are linked to its beneficial action on plant shoot growth, are likely related to the conformational structure of humic acid in solution and its interaction with the cell wall at the root surface. PMID:26450705

Root Morphology Was Improved in a Late-Stage Vigor Super Rice Cultivar.

PubMed

Huang, Min; Chen, Jiana; Cao, Fangbo; Jiang, Ligeng; Zou, Yingbin

2015-01-01

This study aimed to test the hypothesis that root morphology might be improved and consequently contributing to superior post-heading shoot growth and grain yield in late-stage vigor super rice. A pot experiment was carried out to compare yield attributes, shoot growth and physiological properties and root morphological traits between a late-stage vigor super rice cultivar (Y-liangyou 087) and an elite rice cultivar (Teyou 838). Grain yield and total shoot biomass were 7-9% higher in Y-liangyou 087 than in Teyou 838. Y-liangyou 087 had 60-64% higher post-heading shoot growth rate and biomass production than Teyou 838. Average relative chlorophyll concentration and net photosynthetic rate in flag leaves were 7-11% higher in Y-liangyou 087 than in Teyou 838 during heading to 25 days after heading. Y-liangyou 087 had 41% higher post-heading shoot N uptake but 17-25% lower root biomass and root-shoot ratio at heading and maturity than Teyou 838. Specific root length and length and surface area of fine roots were higher in Y-liangyou 087 than in Teyou 838 at heading and maturity by more than 15%. These results indicated that root-shoot relationships were well balanced during post-heading phase in the late-stage vigor super rice cultivar Y-liangyou 087 by improving root morphology including avoiding a too great root biomass and developing a large fine root system.

Investigation of the effects of cadmium by micro analytical methods on Lycopersicon esculentum Mill. roots.

PubMed

Colak, G; Baykul, M C; Gürler, R; Catak, E; Caner, N

2014-09-01

The interactions between cadmium stress and plant nutritional elements have been investigated on complete plant or at the level of organs. This study was undertaken to contribute to the exploration of the physiological basis of cadmium phytotoxicity. We examined the changes in the nutritional element compositions of the root epidermal cells of the seedlings of Lycopersicon esculentum Mill. at the initial growth stages that is known as the most sensitive stage to the stress. Effects of cadmium stress on the seedlings of Lycopersicon esculentum Mill. were examined by EDX (Energy Dispersive X-Ray Microanalysis) assay performed with using low vacuum (∼ 24 Pascal) Scanning Electron Microscopy. In the analysis performed at the level of root epidermal cells, some of the macro- and micronutrient contents of the cells (carbon, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, copper, and zinc levels) were found to change when the applying toxic concentrations of cadmium. There was no change in the manganese and sodium content of the epidermal cells. It was concluded that the changes in nutritional element composition of the cells can be considered as an effective parameter in explaining the physiological mechanisms of cadmium-induced growth inhibition.

Fixed allocation patterns, rather than plasticity, benefit recruitment and recovery from drought in seedlings of a desert shrub

PubMed Central

Zhang, Yao; Li, Yan; Xie, Jiang-Bo

2016-01-01

The response of plants to drought is controlled by the interaction between physiological regulation and morphological adjustment. Although recent studies have highlighted the long-term morphological acclimatization of plants to drought, there is still debate on how plant biomass allocation patterns respond to drought. In this study, we performed a greenhouse experiment with first-year seedlings of a desert shrub in control, drought and re-water treatments, to examine their physiological and morphological traits during drought and subsequent recovery. We found that (i) biomass was preferentially allocated to roots along a fixed allometric trajectory throughout the first year of development, irrespective of the variation in water availability; and (ii) this fixed biomass allocation pattern benefited the post-drought recovery. These results suggest that, in a stressful environment, natural selection has favoured a fixed biomass allocation pattern rather than plastic responses to environmental variation. The fixed ‘preferential allocation to root’ biomass suggests that roots may play a critical role in determining the fate of this desert shrub during prolonged drought. As the major organ for resource acquisition and storage, how the root system functions during drought requires further investigation. PMID:27073036

Perennial Roots to Immortality1,2[C

PubMed Central

Munné-Bosch, Sergi

2014-01-01

Maximum lifespan greatly varies among species, and it is not strictly determined; it can change with species evolution. Clonal growth is a major factor governing maximum lifespan. In the plant kingdom, the maximum lifespans described for clonal and nonclonal plants vary by an order of magnitude, with 43,600 and 5,062 years for Lomatia tasmanica and Pinus longaeva, respectively. Nonclonal perennial plants (those plants exclusively using sexual reproduction) also present a huge diversity in maximum lifespans (from a few to thousands of years) and even more interestingly, contrasting differences in aging patterns. Some plants show a clear physiological deterioration with aging, whereas others do not. Indeed, some plants can even improve their physiological performance as they age (a phenomenon called negative senescence). This diversity in aging patterns responds to species-specific life history traits and mechanisms evolved by each species to adapt to its habitat. Particularities of roots in perennial plants, such as meristem indeterminacy, modular growth, stress resistance, and patterns of senescence, are crucial in establishing perenniality and understanding adaptation of perennial plants to their habitats. Here, the key role of roots for perennial plant longevity will be discussed, taking into account current knowledge and highlighting additional aspects that still require investigation. PMID:24563283

Effect of coastal eutrophication on growth and physiology of Spartina alterniflora Loisel

NASA Astrophysics Data System (ADS)

Zhang, Yu; Cui, Baoshan; Xie, Tian; Wang, Qing; Yan, Jiaguo

2018-02-01

Coastal eutrophication has become a driver of coastal wetlands loss. Eutrophication caused by the increase of nitrogen content was one of the most main reasons. We analyzed that exogenous ammonium nitrogen (EAN) of different concentration influenced on the growth and physiology of Spartina alterniflora Loisel (S. alterniflora) through simulated conditions. The results showed that growth of the root system largely depended on the environment conditions around S. alterniflora. Higher nitrogen concentration promoted aboveground biomass and increased plant height. On the other hand, as the increase of growth period, higher nitrogen concentration could inhibit the elongation growth of root and reduce the underground biomass. We showed that activity of POD, SOD and MDA content changed in an upward trend along with the increased nitrogen level. There was a significant positive correlation between H+ flux and NO3- flux (r = 0.601, P < 0.01), and a significant negative correlation between H+ flux and NH4+ flux (r = -0.713, P < 0.01) within 1.5 mm from the root tip of S. alterniflora. Efflux and influx of ions were associated with changes of nitrogen levels. This research will provide data supporting for coastal wetland restoration of biodiversity reduction caused by coastal eutrophication.

Changes in extracellular calcium activity during gravity sensing in maize roots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bjoerkman, T.; Cleland, R.E.

1990-05-01

A redistribution of calcium downward across the root cap has been proposed as an essential part of gravitropism in roots. Exogenous {sup 45}Ca moves preferentially downward across gravistimulated maize root tips. However, because of the many calcium-binding sites in the apoplast, this might not result in a physiologically effect change in the apoplasmic calcium activity. To test whether there is such a change, we measured the effect of gravistimulation on the calcium activity with calcium-specific microelectrodes. Decapped maize roots (Zea mays L. cv. Golden Cross Bantam) were grown for 31 h to regenerate gravitropic sensitivity, but not root caps. Themore » calcium activity in the apoplasm surrounding the gravity-sensing cells could then be measured. The initial pCa was 2.60 {plus minus} 0.28 (approx 2.5 mM). The calcium activity on the upper side of the root tip remained constant for about five minutes after gravistimulation, then decreased by about one half. On the lower side, after a similar lag the calcium activity doubled. Control roots, which were decapped but measured before recovering gravisensitivity (19 h), showed no change in calcium activity. We have found a distinct and rapid differential in the apoplasmic calcium activity between the upper and lower sides of gravistimulated maize root tips.« less

Root attributes affecting water uptake of rice (Oryza sativa) under drought

PubMed Central

Henry, Amelia

2012-01-01

Lowland rice roots have a unique physiological response to drought because of their adaptation to flooded soil. Rice root attributes that facilitate growth under flooded conditions may affect rice response to drought, but the relative roles of root structural and functional characteristics for water uptake under drought in rice are not known. Morphological, anatomical, biochemical, and molecular attributes of soil-grown rice roots were measured to investigate the genotypic variability and genotype×environment interactions of water uptake under variable soil water regimes. Drought-resistant genotypes had the lowest night-time bleeding rates of sap from the root system in the field. Diurnal fluctuation predominated as the strongest source of variation for bleeding rates in the field and root hydraulic conductivity (Lp r) in the greenhouse, and was related to expression trends of various PIP and TIP aquaporins. Root anatomy was generally more responsive to drought treatments in drought-resistant genotypes. Suberization and compaction of sclerenchyma layer cells decreased under drought, whereas suberization of the endodermis increased, suggesting differential roles of these two cell layers for the retention of oxygen under flooded conditions (sclerenchyma layer) and retention of water under drought (endodermis). The results of this study point to the genetic variability in responsiveness to drought of rice roots in terms of morphology, anatomy, and function. PMID:22791828

Root attributes affecting water uptake of rice (Oryza sativa) under drought.

PubMed

Henry, Amelia; Cal, Andrew J; Batoto, Tristram C; Torres, Rolando O; Serraj, Rachid

2012-08-01

Lowland rice roots have a unique physiological response to drought because of their adaptation to flooded soil. Rice root attributes that facilitate growth under flooded conditions may affect rice response to drought, but the relative roles of root structural and functional characteristics for water uptake under drought in rice are not known. Morphological, anatomical, biochemical, and molecular attributes of soil-grown rice roots were measured to investigate the genotypic variability and genotype×environment interactions of water uptake under variable soil water regimes. Drought-resistant genotypes had the lowest night-time bleeding rates of sap from the root system in the field. Diurnal fluctuation predominated as the strongest source of variation for bleeding rates in the field and root hydraulic conductivity (Lpr) in the greenhouse, and was related to expression trends of various PIP and TIP aquaporins. Root anatomy was generally more responsive to drought treatments in drought-resistant genotypes. Suberization and compaction of sclerenchyma layer cells decreased under drought, whereas suberization of the endodermis increased, suggesting differential roles of these two cell layers for the retention of oxygen under flooded conditions (sclerenchyma layer) and retention of water under drought (endodermis). The results of this study point to the genetic variability in responsiveness to drought of rice roots in terms of morphology, anatomy, and function.

Salt Stress Reduces Root Meristem Size by Nitric Oxide-Mediated Modulation of Auxin Accumulation and Signaling in Arabidopsis1[OPEN

PubMed Central

Liu, Wen; Li, Rong-Jun; Han, Tong-Tong; Cai, Wei; Fu, Zheng-Wei

2015-01-01

The development of the plant root system is highly plastic, which allows the plant to adapt to various environmental stresses. Salt stress inhibits root elongation by reducing the size of the root meristem. However, the mechanism underlying this process remains unclear. In this study, we explored whether and how auxin and nitric oxide (NO) are involved in salt-mediated inhibition of root meristem growth in Arabidopsis (Arabidopsis thaliana) using physiological, pharmacological, and genetic approaches. We found that salt stress significantly reduced root meristem size by down-regulating the expression of PINFORMED (PIN) genes, thereby reducing auxin levels. In addition, salt stress promoted AUXIN RESISTANT3 (AXR3)/INDOLE-3-ACETIC ACID17 (IAA17) stabilization, which repressed auxin signaling during this process. Furthermore, salt stress stimulated NO accumulation, whereas blocking NO production with the inhibitor Nω-nitro-l-arginine-methylester compromised the salt-mediated reduction of root meristem size, PIN down-regulation, and stabilization of AXR3/IAA17, indicating that NO is involved in salt-mediated inhibition of root meristem growth. Taken together, these findings suggest that salt stress inhibits root meristem growth by repressing PIN expression (thereby reducing auxin levels) and stabilizing IAA17 (thereby repressing auxin signaling) via increasing NO levels. PMID:25818700

Soybean Roots Grown under Heat Stress Show Global Changes in Their Transcriptional and Proteomic Profiles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valdés-López, Oswaldo; Batek, Josef; Gomez-Hernandez, Nicolas

2016-04-25

Heat stress is likely to be a key factor in the negative impact of climate change on crop production. Roots provide support, water and nutrients to other plant organs. Likewise, roots play an important role in the establishment of symbiotic associations with different microorganisms. Despite the physiological relevance of roots, few studies have examined the response of these plant organs to heat stress. In this study, we performed genome-wide transcriptomic and proteomic analyses on isolated root hairs, which are a single, epidermal cell type, and compared their response to whole roots. We identified 2,013 genes differentially regulated in root hairsmore » in response to heat stress. Our gene regulatory module analysis identified ten, key modules that controlled the majority of the transcriptional response to heat stress. We also conducted proteomic analysis on membrane fractions isolated from roots and root hairs. These experiments identified a variety of proteins whose expression changed within 3 hours of application of heat stress. Most of these proteins were predicted to play a role in thermotolerance, as well as in chromatin remodeling and post-transcriptional regulation. The data presented represent an in-depth analysis of the heat stress response of a single cell type in soybean.« less

Tomato ethylene sensitivity determines interaction with plant growth-promoting bacteria.

PubMed

Ibort, Pablo; Molina, Sonia; Núñez, Rafael; Zamarreño, Ángel María; García-Mina, José María; Ruiz-Lozano, Juan Manuel; Orozco-Mosqueda, Maria Del Carmen; Glick, Bernard R; Aroca, Ricardo

2017-07-01

Plant growth-promoting bacteria (PGPB) are soil micro-organisms able to interact with plants and stimulate their growth, positively affecting plant physiology and development. Although ethylene plays a key role in plant growth, little is known about the involvement of ethylene sensitivity in bacterial inoculation effects on plant physiology. Thus, the present study was pursued to establish whether ethylene perception is critical for plant-bacteria interaction and growth induction by two different PGPB strains, and to assess the physiological effects of these strains in juvenile and mature tomato ( Solanum lycopersicum ) plants. An experiment was performed with the ethylene-insensitive tomato never ripe and its isogenic wild-type line in which these two strains were inoculated with either Bacillus megaterium or Enterobacter sp. C7. Plants were grown until juvenile and mature stages, when biomass, stomatal conductance, photosynthesis as well as nutritional, hormonal and metabolic statuses were analysed. Bacillus megaterium promoted growth only in mature wild type plants. However, Enterobacter C7 PGPB activity affected both wild-type and never ripe plants. Furthermore, PGPB inoculation affected physiological parameters and root metabolite levels in juvenile plants; meanwhile plant nutrition was highly dependent on ethylene sensitivity and was altered at the mature stage. Bacillus megaterium inoculation improved carbon assimilation in wild-type plants. However, insensitivity to ethylene compromised B. megaterium PGPB activity, affecting photosynthetic efficiency, plant nutrition and the root sugar content. Nevertheless, Enterobacter C7 inoculation modified the root amino acid content in addition to stomatal conductance and plant nutrition. Insensitivity to ethylene severely impaired B. megaterium interaction with tomato plants, resulting in physiological modifications and loss of PGPB activity. In contrast, Enterobacter C7 inoculation stimulated growth independently of ethylene perception and improved nitrogen assimilation in ethylene-insensitive plants. Thus, ethylene sensitivity is a determinant for B. megaterium , but is not involved in Enterobacter C7 PGPB activity. © The Author 2017. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Allelopatic Potential of Dittrichia viscosa (L.) W. Greuter Mediated by VOCs: A Physiological and Metabolomic Approach.

PubMed

Araniti, Fabrizio; Lupini, Antonio; Sunseri, Francesco; Abenavoli, Maria Rosa

2017-01-01

Dittrichia viscosa (L.) W. Greuter is a pioneer species belonging to the Compositae family. It is widespread in the Mediterranean basin, where it is considered invasive. It is a source of secondary metabolites, playing an important ecological role. D. viscosa plant extracts showed a phytotoxic activity on several physiological processes of different species. In the current study, the allelopathic potential of D. viscosa VOCs, released by its foliage, was evaluated on seed germination and root growth of lettuce. The VOCs effect was also studied on lettuce adult plants in microcosm systems, which better mimicked the open field conditions. D. viscosa VOCs inhibited both seed germination and root growth of lettuce. The VOCs composition revealed a large presence of terpenoids, responsible of the effects observed. Moreover, D. viscosa VOCs caused an alteration on plant water status accompanied by oxidative damages and photoinhibition on lettuce adult plants.

Allelopatic Potential of Dittrichia viscosa (L.) W. Greuter Mediated by VOCs: A Physiological and Metabolomic Approach

PubMed Central

Lupini, Antonio; Sunseri, Francesco; Abenavoli, Maria Rosa

2017-01-01

Dittrichia viscosa (L.) W. Greuter is a pioneer species belonging to the Compositae family. It is widespread in the Mediterranean basin, where it is considered invasive. It is a source of secondary metabolites, playing an important ecological role. D. viscosa plant extracts showed a phytotoxic activity on several physiological processes of different species. In the current study, the allelopathic potential of D. viscosa VOCs, released by its foliage, was evaluated on seed germination and root growth of lettuce. The VOCs effect was also studied on lettuce adult plants in microcosm systems, which better mimicked the open field conditions. D. viscosa VOCs inhibited both seed germination and root growth of lettuce. The VOCs composition revealed a large presence of terpenoids, responsible of the effects observed. Moreover, D. viscosa VOCs caused an alteration on plant water status accompanied by oxidative damages and photoinhibition on lettuce adult plants. PMID:28085959

Antimony (SbIII) reduces growth, declines photosynthesis, and modifies leaf tissue anatomy in sunflower (Helianthus annuus L.).

PubMed

Vaculík, Marek; Mrázová, Anna; Lux, Alexander

2015-12-01

The role of antimony (Sb)--a non-essential trace metalloid--in physiological processes running in crops is still poorly understood. Present paper describes the effect of Sb tartrate (SbIII) on growth, Sb uptake, photosynthesis, photosynthetic pigments, and leaf tissue organization in young sunflower plants grown in hydroponics. We found that growth of below- and aboveground part was reduced with increasing concentration of Sb in the medium. Although Sb was mostly taken up by sunflower roots and only small part (1-2%) was translocated to the shoots, decline in photosynthesis, transpiration, and decreased content of photosynthetic pigments were observed. This indicates that despite relatively low mobility of Sb in root-shoot system, Sb in shoot noticeably modifies physiological status and reduced plant growth. Additionally, leaf anatomical changes indicated that Sb reduced the size of intercellular spaces and made leaf tissue more compact.

Physiological responses and partisan bias: beyond self-reported measures of party identification.

PubMed

Petersen, Michael Bang; Giessing, Ann; Nielsen, Jesper

2015-01-01

People are biased partisans: they tend to agree with policies from political parties they identify with, independent of policy content. Here, we investigate how physiological reactions to political parties shape bias. Using changes in galvanic skin conductance responses to the visual presentation of party logos, we obtained an implicit and physiological measure of the affective arousal associated with political parties. Subsequently, we exposed subjects to classical party cue experiments where the party sponsors of specific policies were experimentally varied. We found that partisan bias only obtains among those exhibiting a strong physiological reaction to the party source; being a self-reported party identifier is not sufficient on its own. This suggests that partisan bias is rooted in implicit, affective reactions.

Physiological Responses and Partisan Bias: Beyond Self-Reported Measures of Party Identification

PubMed Central

Petersen, Michael Bang; Giessing, Ann; Nielsen, Jesper

2015-01-01

People are biased partisans: they tend to agree with policies from political parties they identify with, independent of policy content. Here, we investigate how physiological reactions to political parties shape bias. Using changes in galvanic skin conductance responses to the visual presentation of party logos, we obtained an implicit and physiological measure of the affective arousal associated with political parties. Subsequently, we exposed subjects to classical party cue experiments where the party sponsors of specific policies were experimentally varied. We found that partisan bias only obtains among those exhibiting a strong physiological reaction to the party source; being a self-reported party identifier is not sufficient on its own. This suggests that partisan bias is rooted in implicit, affective reactions. PMID:26010527

Physiological and Transcriptome Responses to Combinations of Elevated CO2 and Magnesium in Arabidopsis thaliana

PubMed Central

Niu, Yaofang; Ahammed, Golam Jalal; Tang, Caixian; Guo, Longbiao; Yu, Jingquan

2016-01-01

The unprecedented rise in atmospheric CO2 concentration and injudicious fertilization or heterogeneous distribution of Mg in the soil warrant further research to understand the synergistic and holistic mechanisms involved in the plant growth regulation. This study investigated the influence of elevated CO2 (800 μL L−1) on physiological and transcriptomic profiles in Arabidopsis cultured in hydroponic media treated with 1 μM (low), 1000 μM (normal) and 10000 μM (high) Mg2+. Following 7-d treatment, elevated CO2 increased the shoot growth and chlorophyll content under both low and normal Mg supply, whereas root growth was improved exclusively under normal Mg nutrition. Notably, the effect of elevated CO2 on mineral homeostasis in both shoots and roots was less than that of Mg supply. Irrespective of CO2 treatment, high Mg increased number of young leaf but decreased root growth and absorption of P, K, Ca, Fe and Mn whereas low Mg increased the concentration of P, K, Ca and Fe in leaves. Transcriptomics results showed that elevated CO2 decreased the expression of genes related to cell redox homeostasis, cadmium response, and lipid localization, but enhanced signal transduction, protein phosphorylation, NBS-LRR disease resistance proteins and subsequently programmed cell death in low-Mg shoots. By comparison, elevated CO2 enhanced the response of lipid localization (mainly LTP transfer protein/protease inhibitor), endomembrane system, heme binding and cell wall modification in high-Mg roots. Some of these transcriptomic results are substantially in accordance with our physiological and/or biochemical analysis. The present findings broaden our current understanding on the interactive effect of elevated CO2 and Mg levels in the Arabidopsis, which may help to design the novel metabolic engineering strategies to cope with Mg deficiency/excess in crops under elevated CO2. PMID:26881808

Brassinolide Increases Potato Root Growth In Vitro in a Dose-Dependent Way and Alleviates Salinity Stress

PubMed Central

Xia, Shitou; Su, Yi; Wang, Huiqun; Luo, Weigui; Su, Shengying

2016-01-01

Brassinosteroids (BRs) are steroidal phytohormones that regulate various physiological processes, such as root development and stress tolerance. In the present study, we showed that brassinolide (BL) affects potato root in vitro growth in a dose-dependent manner. Low BL concentrations (0.1 and 0.01 μg/L) promoted root elongation and lateral root development, whereas high BL concentrations (1–100 μg/L) inhibited root elongation. There was a significant (P < 0.05) positive correlation between root activity and BL concentrations within a range from 0.01 to 100 μg/L, with the peak activity of 8.238 mg TTC·g−1 FW·h−1 at a BL concentration of 100 μg/L. Furthermore, plants treated with 50 μg/L BL showed enhanced salt stress tolerance through in vitro growth. Under this scenario, BL treatment enhanced the proline content and antioxidant enzymes' (superoxide dismutase, peroxidase, and catalase) activity and reduced malondialdehyde content in potato shoots. Application of BL maintain K+ and Na+ homeostasis by improving tissue K+/Na+ ratio. Therefore, we suggested that the effects of BL on root development from stem fragments explants as well as on primary root development are dose-dependent and that BL application alleviates salt stress on potato by improving root activity, root/shoot ratio, and antioxidative capacity in shoots and maintaining K+/Na+ homeostasis in potato shoots and roots. PMID:27803931

Analysis of the relationship between rusty root incidences and soil properties in Panax ginseng

NASA Astrophysics Data System (ADS)

Wang, Q. X.; Xu, C. L.; Sun, H.; Ma, L.; Li, L.; Zhang, D. D.; Zhang, Y. Y.

2016-08-01

Rusty root is a serious problem in ginseng cultivation that limits the production and quality of ginseng worldwide. The Changbai Mountains are the most famous area for ginseng cultivation in China. To clarify the relationship between rusty root and soil characteristics, physico-chemical properties and enzymatic activities of soil collected from five different fields in the Changbai Mountains were analyzed and a controlled experiment carried out by increasing the concentration of Fe (II). Soil bulk density, moisture, total iron (Fe) and total manganese (Mn) concentrations and polyphenol oxidase (PPO) activity were significantly higher in rusty root than healthy root groups (two-sample test, P<0.05 or P<0.01), respectively. Pearson test showed that there was a significant positive correlation between rusty root index and pH, N, Fe, Mn, Al, Zn and Ca of soil samples collected from fields (P<0.05 or P<0.01), and a significant positive correlation also occurred between rusty root index and Fe (II) added to soil in Fe (II) inducing rusty root (P<0.01). Physiological factors may be very important roles giving rise to ginseng rusty root. Fe (III) reduction and Fe (II) oxidation could be important in increasing the incidence of rusty root. Soil moisture and bulk density of non-rhizosphere soil not attached to the root surface, and pH, N and PPO content of rhizosphere soils attached to the root surface were heavily involved in the reduction, oxidation and sequestration of metal ions.

Multiwall carbon nanotubes modulate paraquat toxicity in Arabidopsis thaliana.

PubMed

Fan, Xiaoji; Xu, Jiahui; Lavoie, Michel; Peijnenburg, W J G M; Zhu, Youchao; Lu, Tao; Fu, Zhengwei; Zhu, Tingheng; Qian, Haifeng

2018-02-01

Carbon nanotubes can be either toxic or beneficial to plant growth and can also modulate toxicity of organic contaminants through surface sorption. The complex interacting toxic effects of carbon nanotubes and organic contaminants in plants have received little attention in the literature to date. In this study, the toxicity of multiwall carbon nanotubes (MWCNT, 50 mg/L) and paraquat (MV, 0.82 mg/L), separately or in combination, were evaluated at the physiological and the proteomic level in Arabidopsis thaliana for 7-14 days. The results revealed that the exposure to MWCNT had no inhibitory effect on the growth of shoots and leaves. Rather, MWCNT stimulated the relative electron transport rate and the effective photochemical quantum yield of PSII value as compared to the control by around 12% and lateral root production up to nearly 4-fold as compared to the control. The protective effect of MWCNT on MV toxicity on the root surface area could be quantitatively explained by the extent of MV adsorption on MWCNT and was related to stimulation of photosynthesis, antioxidant protection and number and area of lateral roots which in turn helped nutrient assimilation. The influence of MWCNT and MV on photosynthesis and oxidative stress at the physiological level was consistent with the proteomics analysis, with various over-expressed photosynthesis-related proteins (by more than 2 folds) and various under-expressed oxidative stress related proteins (by about 2-3 folds). This study brings new insights into the interactive effects of two xenobiotics (MWCNT and MV) on the physiology of a model plant. Copyright © 2017 Elsevier Ltd. All rights reserved.

Physiological, structural and molecular traits activated in strawberry plants after inoculation with the plant growth-promoting bacterium Azospirillum brasilense REC3.

PubMed

Guerrero-Molina, M F; Lovaisa, N C; Salazar, S M; Martínez-Zamora, M G; Díaz-Ricci, J C; Pedraza, R O

2015-05-01

The plant growth-promoting strain REC3 of Azospirillum brasilense, isolated from strawberry roots, prompts growth promotion and systemic protection against anthracnose disease in this crop. Hence, we hypothesised that A. brasilense REC3 can induce different physiological, structural and molecular responses in strawberry plants. Therefore, the aim of this work was to study these traits activated in Azospirillum-colonised strawberry plants, which have not been assessed until now. Healthy, in vitro micropropagated plants were root-inoculated with REC3 under hydroponic conditions; root and leaf tissues were sampled at different times, and oxidative burst, phenolic compound content, malondialdehyde (MDA) concentration, callose deposition, cell wall fortification and gene expression were evaluated. Azospirillum inoculation enhanced levels of soluble phenolic compounds after 12 h post-inoculation (hpi), while amounts of cell wall bound phenolics were similar in inoculated and control plants. Other early responses activated by REC3 (at 24 hpi) were a decline of lipid peroxidation and up-regulation of strawberry genes involved in defence (FaPR1), bacterial recognition (FaFLS2) and H₂O₂ depuration (FaCAT and FaAPXc). The last may explain the apparent absence of oxidative burst in leaves after bacterial inoculation. Also, REC3 inoculation induced delayed structural responses such as callose deposition and cell wall fortification (at 72 hpi). Results showed that A. brasilense REC3 is capable of exerting beneficial effects on strawberry plants, reinforcing their physiological and cellular characteristics, which in turns contribute to improve plant performance. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

Stretching of roots contributes to the pathophysiology of radiculopathies.

PubMed

Berthelot, Jean-Marie; Laredo, Jean-Denis; Darrieutort-Laffite, Christelle; Maugars, Yves

2018-01-01

To perform a synthesis of articles addressing the role of stretching on roots in the pathophysiology of radiculopathy. Review of relevant articles on this topic available in the PubMed database. An intraoperative microscopy study of patients with sciatica showed that in all patients the hernia was adherent to the dura mater of nerve roots. During the SLR (Lasègue's) test, the limitation of nerve root movement occurs by periradicular adhesive tissue, and temporary ischemic changes in the nerve root induced by the root stretching cause transient conduction disturbances. Spinal roots are more frail than peripheral nerves, and other mechanical stresses than root compression can also induce radiculopathy, especially if they also impair intraradicular blood flow, or the function of the arachnoid villi intimately related to radicular veins. For instance arachnoiditis, the lack of peridural fat around the thecal sac, and epidural fibrosis following surgery, can all promote sciatica, especially in patients whose sciatic trunks also stick to piriformis or internus obturator muscles. Indeed, stretching of roots is greatly increased by adherence at two levels. As excessive traction of nerve roots is not shown by imaging, many physicians have unlearned to think in terms of microscopic and physiologic changes, although nerve root compression in the lumbar MRI is lacking in more than 10% of patients with sciatica. It should be reminded that, while compression of a spinal nerve root implies stretching of this root, the reverse is not true: stretching of some roots can occur without any visible compression. Copyright © 2017 Société française de rhumatologie. Published by Elsevier SAS. All rights reserved.

A novel root gravitropism mutant of Arabidopsis thaliana exhibiting altered auxin physiology

NASA Technical Reports Server (NTRS)

Simmons, C.; Migliaccio, F.; Masson, P.; Caspar, T.; Soll, D.

1995-01-01

A root gravitropism mutant was isolated from the DuPont Arabidopsis thaliana T-DNA insertional mutagenesis collection. This mutant has reduced root gravitropism, hence the name rgr1. Roots of rgr1 are shorter than those of wild-type, and they have reduced lateral root formation. In addition, roots of rgr1 coil clockwise on inclined agar plates, unlike wild-type roots which grow in a wavy pattern. The rgr1 mutant has increased resistance, as measured by root elongation, to exogenously applied auxins (6-fold to indole-3-acetic acid, 3-fold to 2,4-dichlorophenoxyacetic acid, and 2-fold to napthyleneacetic acid). It is also resistant to polar auxin transport inhibitors (2-fold to triiodobenzoic acid and 3- to 5-fold to napthylphthalamic acid). The rgr1 mutant does not appear to be resistant to other plant hormone classes. When grown in the presence of 10(-7) M 2,4-dichlorophenoxyacetic acid, rgr1 roots have fewer root hairs than wild type. All these rgr1 phenotypes are Mendelian recessives. Complementation tests indicate that rgr1 is not allelic to previously characterized agravitropic or auxin-resistant mutants. The rgr1 locus was mapped using visible markers to 1.4 +/- 0.6 map units from the CH1 locus at 1-65.4. The rgr1 mutation and the T-DNA cosegregate, suggesting that rgr1 was caused by insertional gene inactivation.

Soybean Roots Grown under Heat Stress Show Global Changes in Their Transcriptional and Proteomic Profiles

DOE PAGES

Valdés-López, Oswaldo; Batek, Josef; Gomez-Hernandez, Nicolas; ...

2016-04-25

Heat stress is likely to be a key factor in the negative impact of climate change on crop production. Heat stress significantly influences the functions of roots, which provide support, water, and nutrients to other plant organs. Likewise, roots play an important role in the establishment of symbiotic associations with different microorganisms. Despite the physiological relevance of roots, few studies have examined their response to heat stress. Here in this study, we performed genome-wide transcriptomic and proteomic analyses on isolated root hairs, which are a single, epidermal cell type, and compared their response to stripped roots. On average, we identifiedmore » 1849 and 3091 genes differentially regulated in root hairs and stripped roots, respectively, in response to heat stress. Our gene regulatory module analysis identified 10 key modules that might control the majority of the transcriptional response to heat stress. We also conducted proteomic analysis on membrane fractions isolated from root hairs and compared these responses to stripped roots. These experiments identified a variety of proteins whose expression changed within 3 h of application of heat stress. Most of these proteins were predicted to play a significant role in thermo-tolerance, as well as in chromatin remodeling and post-transcriptional regulation. In conclusion, the data presented represent an in-depth analysis of the heat stress response of a single cell type in soybean.« less

Ammonium Inhibits Primary Root Growth by Reducing the Length of Meristem and Elongation Zone and Decreasing Elemental Expansion Rate in the Root Apex in Arabidopsis thaliana

PubMed Central

Gao, Kun; Chen, Fanjun; Yuan, Lixing; Mi, Guohua

2013-01-01

The inhibitory effect of ammonium on primary root growth has been well documented; however the underlying physiological and molecular mechanisms are still controversial. To avoid ammonium toxicity to shoot growth, we used a vertical two-layer split plate system, in which the upper layer contained nitrate and the lower layer contained ammonium. In this way, nitrogen status was maintained and only the apical part of the root system was exposed to ammonium. Using a kinematic approach, we show here that 1 mM ammonium reduces primary root growth, decreasing both elemental expansion and cell production. Ammonium inhibits the length of elongation zone and the maximum elemental expansion rate. Ammonium also decreases the apparent length of the meristem as well as the number of dividing cells without affecting cell division rate. Moreover, ammonium reduces the number of root cap cells but appears to affect neither the status of root stem cell niche nor the distal auxin maximum at the quiescent center. Ammonium also inhibits root gravitropism and concomitantly down-regulates the expression of two pivotal auxin transporters, AUX1 and PIN2. Insofar as ammonium inhibits root growth rate in AUX1 and PIN2 loss-of-function mutants almost as strongly as in wild type, we conclude that ammonium inhibits root growth and gravitropism by largely distinct pathways. PMID:23577185

Ecophysiology of wetland plant roots: A modelling comparison of aeration in relation to species distribution

USGS Publications Warehouse

Sorrell, B.K.; Mendelssohn, I.A.; McKee, K.L.; Woods, R.A.

2000-01-01

This study examined the potential for inter-specific differences in root aeration to determine wetland plant distribution in nature. We compared aeration in species that differ in the type of sediment and depth of water they colonize. Differences in root anatomy, structure and physiology were applied to aeration models that predicted the maximum possible aerobic lengths and development of anoxic zones in primary adventitious roots. Differences in anatomy and metabolism that provided higher axial fluxes of oxygen allowed deeper root growth in species that favour more reducing sediments and deeper water. Modelling identified factors that affected growth in anoxic soils through their effects on aeration. These included lateral root formation, which occurred at the expense of extension of the primary root because of the additional respiratory demand they imposed, reducing oxygen fluxes to the tip and stele, and the development of stelar anoxia. However, changes in sediment oxygen demand had little detectable effect on aeration in the primary roots due to their low wall permeability and high surface impedance, but appeared to reduce internal oxygen availability by accelerating loss from laterals. The development of pressurized convective gas flow in shoots and rhizomes was also found to be important in assisting root aeration, as it maintained higher basal oxygen concentrations at the rhizome-root junctions in species growing into deep water. (C) 2000 Annals of Botany Company.

Molecular and physiological responses of trees to waterlogging stress.

PubMed

Kreuzwieser, Jürgen; Rennenberg, Heinz

2014-10-01

One major effect of global climate change will be altered precipitation patterns in many regions of the world. This will cause a higher probability of long-term waterlogging in winter/spring and flash floods in summer because of extreme rainfall events. Particularly, trees not adapted at their natural site to such waterlogging stress can be impaired. Despite the enormous economic, ecological and social importance of forest ecosystems, the effect of waterlogging on trees is far less understood than the effect on many crops or the model plant Arabidopsis. There is only a handful of studies available investigating the transcriptome and metabolome of waterlogged trees. Main physiological responses of trees to waterlogging include the stimulation of fermentative pathways and an accelerated glycolytic flux. Many energy-consuming, anabolic processes are slowed down to overcome the energy crisis mediated by waterlogging. A crucial feature of waterlogging tolerance is the steady supply of glycolysis with carbohydrates, particularly in the roots; stress-sensitive trees fail to maintain sufficient carbohydrate availability resulting in the dieback of the stressed tissues. The present review summarizes physiological and molecular features of waterlogging tolerance of trees; the focus is on carbon metabolism in both, leaves and roots of trees. © 2014 John Wiley & Sons Ltd.

Specialized 'dauciform' roots of Cyperaceae are structurally distinct, but functionally analogous with 'cluster' roots.

PubMed

Shane, Michael W; Cawthray, Gregory R; Cramer, Michael D; Kuo, John; Lambers, Hans

2006-10-01

When grown in nutrient solutions of extremely low [P] (

Proteomic and physiological analyses reveal the role of exogenous spermidine on cucumber roots in response to Ca(NO3)2 stress.

PubMed

Du, Jing; Guo, Shirong; Sun, Jin; Shu, Sheng

2018-05-01

The mechanism of exogenous Spd-induced Ca(NO 3 ) 2 stress tolerance in cucumber was studied by proteomics and physiological analyses. Protein-protein interaction network revealed 13 key proteins involved in Spd-induced Ca(NO 3 ) 2 stress resistance. Ca(NO 3 ) 2 stress is one of the major reasons for secondary salinization that limits cucumber plant development in greenhouse. The conferred protective role of exogenous Spd on cucumber in response to Ca(NO 3 ) 2 stress cues involves changes at the cellular and physiological levels. To investigate the molecular foundation of exogenous Spd in Ca(NO 3 ) 2 stress tolerance, a proteomic approach was performed in our work. After a 9 days period of Ca(NO 3 ) 2 stress and/or exogenous Spd, 71 differential protein spots were confidently identified. The resulting proteins were enriched in seven different categories of biological processes, including protein metabolism, carbohydrate and energy metabolism, ROS homeostasis and stress defense, cell wall related, transcription, others and unknown. Protein metabolism (31.2%), carbohydrate and energy metabolism (15.6%), ROS homeostasis and stress defense (32.5%) were the three largest functional categories in cucumber root and most of them were significantly increased by exogenous Spd. The Spd-responsive protein interaction network revealed 13 key proteins, whose accumulation changes could be critical for Spd-induced resistance; all 13 proteins were upregulated by Spd at transcriptional and protein levels in response to Ca(NO 3 ) 2 stress. Furthermore, accumulation of antioxidant enzymes, non-enzymatic antioxidant and polyamines, along with reduction of H 2 O 2 and MDA, were detected after exogenous Spd application during Ca(NO 3 ) 2 stress. The results of these proteomic and physiological analyses in cucumber root may facilitate a better understanding of the underlying mechanism of Ca(NO 3 ) 2 stress tolerance mediated by exogenous Spd.

Physiological, biochemical and molecular responses in four Prunus rootstocks submitted to drought stress.

PubMed

Jiménez, Sergio; Dridi, Jihène; Gutiérrez, Diego; Moret, David; Irigoyen, Juan J; Moreno, María A; Gogorcena, Yolanda

2013-10-01

An understanding of the mechanisms that determine plant response to reduced water availability is essential to improve water-use efficiency (WUE) of stone fruit crops. The physiological, biochemical and molecular drought responses of four Prunus rootstocks (GF 677, Cadaman, ROOTPAC 20 and ROOTPAC(®) R) budded with 'Catherina' peach cultivar were studied. Trees were grown in 15-l containers and subjected to a progressive water stress for 26 days, monitoring soil moisture content by time domain reflectometry. Photosynthetic and gas exchange parameters were determined. Root and leaf soluble sugars and proline content were also measured. At the end of the experiment, stressed plants showed lower net photosynthesis rate, stomatal conductance and transpiration rate, and higher intrinsic leaf WUE (AN/gs). Soluble sugars and proline concentration changes were observed, in both root and leaf tissues, especially in an advanced state of stress. The accumulation of proline in roots and leaves with drought stress was related to the decrease in osmotic potential and increase in WUE, whereas the accumulation of sorbitol in leaves, raffinose in roots and proline in both tissues was related only to the increase in the WUE. Owing to the putative role of raffinose and proline as antioxidants and their low concentration, they could be ameliorating deleterious effects of drought-induced oxidative stress by protecting membranes and enzymes rather than acting as active osmolytes. Higher expression of P5SC gene in roots was also consistent with proline accumulation in the tolerant genotype GF 677. These results indicate that accumulation of sorbitol, raffinose and proline in different tissues and/or the increase in P5SC expression could be used as markers of drought tolerance in peach cultivars grafted on Prunus rootstocks.

Biosynthesis of scopoletin and scopolin in cassava roots during post-harvest physiological deterioration: the E-Z-isomerisation stage.

PubMed

Bayoumi, Soad A L; Rowan, Michael G; Blagbrough, Ian S; Beeching, John R

2008-12-01

Two to three days after harvesting, cassava (Manihot esculenta Crantz) roots suffer from post-harvest physiological deterioration (PPD) when secondary metabolites are accumulated. Amongst these are hydroxycoumarins (e.g. scopoletin and its glucoside scopolin) which play roles in plant defence and have pharmacological activities. Some steps in the biosynthesis of these molecules are still unknown in cassava and in other plants. We exploit the accumulation of these coumarins during PPD to investigate the E-Z-isomerisation step in their biosynthesis. Feeding cubed cassava roots with E-cinnamic-3,2',3',4',5',6'-d(5) acid gave scopoletin-d(2). However, feeding with E-cinnamic-3,2',3',4',5',6'-d(6) and E-cinnamic-2,3,2',3',4',5',6'-d(7) acids, both gave scopoletin-d(3), the latter not affording the expected scopoletin-d(4). We therefore synthesised and fed with E-cinnamic-2-d(1) when unlabelled scopoletin was biosynthesised. Solely the hydrogen (or deuterium) at C2 of cinnamic acid is exchanged in the biosynthesis of hydroxycoumarins. If the mechanism of E-Z-cinnamic acid isomerisation were photochemical, we would not expect to see the loss of deuterium which we observed. Therefore, a possible mechanism is an enzyme catalysed 1,4-Michael addition, followed by sigma-bond rotation and hydrogen (or deuterium) elimination to yield the Z-isomer. Feeding the roots under light and dark conditions with E-cinnamic-2,3,2',3',4',5',6'-d(7) acid gave scopoletin-d(3) with no significant difference in the yields. We conclude that the E-Z-isomerisation stage in the biosynthesis of scopoletin and scopolin, in cassava roots during PPD, is not photochemical, but could be catalysed by an isomerase which is independent of light.

Enhanced Reactive Oxygen Species Scavenging by Overproduction of Superoxide Dismutase and Catalase Delays Postharvest Physiological Deterioration of Cassava Storage Roots1[C][W][OA

PubMed Central

Xu, Jia; Duan, Xiaoguang; Yang, Jun; Beeching, John R.; Zhang, Peng

2013-01-01

Postharvest physiological deterioration (PPD) of cassava (Manihot esculenta) storage roots is the result of a rapid oxidative burst, which leads to discoloration of the vascular tissues due to the oxidation of phenolic compounds. In this study, coexpression of the reactive oxygen species (ROS)-scavenging enzymes copper/zinc superoxide dismutase (MeCu/ZnSOD) and catalase (MeCAT1) in transgenic cassava was used to explore the intrinsic relationship between ROS scavenging and PPD occurrence. Transgenic cassava plants integrated with the expression cassette p54::MeCu/ZnSOD-35S::MeCAT1 were confirmed by Southern-blot analysis. The expression of MeCu/ZnSOD and MeCAT1 was verified by quantitative reverse transcription-polymerase chain reaction and enzymatic activity analysis both in the leaves and storage roots. Under exposure to the ROS-generating reagent methyl viologen or to hydrogen peroxide (H2O2), the transgenic plants showed higher enzymatic activities of SOD and CAT than the wild-type plants. Levels of malondialdehyde, chlorophyll degradation, lipid peroxidation, and H2O2 accumulation were dramatically reduced in the transgenic lines compared with the wild type. After harvest, the storage roots of transgenic cassava lines show a delay in their PPD response of at least 10 d, accompanied by less mitochondrial oxidation and H2O2 accumulation, compared with those of the wild type. We hypothesize that this is due to the combined ectopic expression of Cu/ZnSOD and CAT leading to an improved synergistic ROS-scavenging capacity of the roots. Our study not only sheds light on the mechanism of the PPD process but also develops an effective approach for delaying the occurrence of PPD in cassava. PMID:23344905

Enhanced reactive oxygen species scavenging by overproduction of superoxide dismutase and catalase delays postharvest physiological deterioration of cassava storage roots.

PubMed

Xu, Jia; Duan, Xiaoguang; Yang, Jun; Beeching, John R; Zhang, Peng

2013-03-01

Postharvest physiological deterioration (PPD) of cassava (Manihot esculenta) storage roots is the result of a rapid oxidative burst, which leads to discoloration of the vascular tissues due to the oxidation of phenolic compounds. In this study, coexpression of the reactive oxygen species (ROS)-scavenging enzymes copper/zinc superoxide dismutase (MeCu/ZnSOD) and catalase (MeCAT1) in transgenic cassava was used to explore the intrinsic relationship between ROS scavenging and PPD occurrence. Transgenic cassava plants integrated with the expression cassette p54::MeCu/ZnSOD-35S::MeCAT1 were confirmed by Southern-blot analysis. The expression of MeCu/ZnSOD and MeCAT1 was verified by quantitative reverse transcription-polymerase chain reaction and enzymatic activity analysis both in the leaves and storage roots. Under exposure to the ROS-generating reagent methyl viologen or to hydrogen peroxide (H2O2), the transgenic plants showed higher enzymatic activities of SOD and CAT than the wild-type plants. Levels of malondialdehyde, chlorophyll degradation, lipid peroxidation, and H2O2 accumulation were dramatically reduced in the transgenic lines compared with the wild type. After harvest, the storage roots of transgenic cassava lines show a delay in their PPD response of at least 10 d, accompanied by less mitochondrial oxidation and H2O2 accumulation, compared with those of the wild type. We hypothesize that this is due to the combined ectopic expression of Cu/ZnSOD and CAT leading to an improved synergistic ROS-scavenging capacity of the roots. Our study not only sheds light on the mechanism of the PPD process but also develops an effective approach for delaying the occurrence of PPD in cassava.

Physiological and Proteomic Analysis of the Rice Mutant cpm2 Suggests a Negative Regulatory Role of Jasmonic Acid in Drought Tolerance

PubMed Central

Dhakarey, Rohit; Raorane, Manish L.; Treumann, Achim; Peethambaran, Preshobha K.; Schendel, Rachel R.; Sahi, Vaidurya P.; Hause, Bettina; Bunzel, Mirko; Henry, Amelia; Kohli, Ajay; Riemann, Michael

2017-01-01

It is widely known that numerous adaptive responses of drought-stressed plants are stimulated by chemical messengers known as phytohormones. Jasmonic acid (JA) is one such phytohormone. But there are very few reports revealing its direct implication in drought related responses or its cross-talk with other phytohormones. In this study, we compared the morpho-physiological traits and the root proteome of a wild type (WT) rice plant with its JA biosynthesis mutant coleoptile photomorphogenesis 2 (cpm2), disrupted in the allene oxide cyclase (AOC) gene, for insights into the role of JA under drought. The mutant had higher stomatal conductance, higher water use efficiency and higher shoot ABA levels under severe drought as compared to the WT. Notably, roots of cpm2 were better developed compared to the WT under both, control and drought stress conditions. Root proteome was analyzed using the Tandem Mass Tag strategy to better understand this difference at the molecular level. Expectedly, AOC was unique but notably highly abundant under drought in the WT. Identification of other differentially abundant proteins (DAPs) suggested increased energy metabolism (i.e., increased mobilization of resources) and reactive oxygen species scavenging in cpm2 under drought. Additionally, various proteins involved in secondary metabolism, cell growth and cell wall synthesis were also more abundant in cpm2 roots. Proteome-guided transcript, metabolite, and histological analyses provided further insights into the favorable adaptations and responses, most likely orchestrated by the lack of JA, in the cpm2 roots. Our results in cpm2 are discussed in the light of JA crosstalk to other phytohormones. These results together pave the path for understanding the precise role of JA during drought stress in rice. PMID:29250082

Nitric oxide signaling is involved in the response to iron deficiency in the woody plant Malus xiaojinensis.

PubMed

Zhai, Longmei; Xiao, Dashuang; Sun, Chaohua; Wu, Ting; Han, Zhenhai; Zhang, Xinzhong; Xu, Xuefeng; Wang, Yi

2016-12-01

To cope with iron (Fe) deficiency, plants have evolved a wide range of adaptive responses from changes in morphology to altered physiological responses. Recent studies have demonstrated that nitric oxide (NO) is involved in the Fe-deficiency response through hormonal signaling pathways. Here, we report that NO plays a significant role in Malus xiaojinensis, an Fe-efficient woody plant. Fe deficiency triggered significant accumulation of NO in the root system, predominantly in the outer cortical and epidermal cells of the elongation zone. The NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO) completely arrested Fe deficiency-induced root hair formation, blocked the increase in root ferric-chelate reductase activity and in root H + excretion, further reduced the active iron content in young leaves and roots, and prevented the upregulation of the critical Fe-related genes, FIT, MxFRO2-like, and MxIRT1. These conditions were restored under Fe deficiency by treatment with the NO donor, sodium nitroprusside (SNP). Additionally, chlorophyll content and relative expression levels of the genes chlorophyll a deoxygenase (MxCAO) and polyamine oxidase (MxPAO) were not changed significantly following Fe deficiency for 6 d; however, SNP treatment increased MxHEMA gene expression. Interestingly, the Fv/Fm ratio, the maximum quantum yield of photosystem II (PSII), decreased significantly following cPTIO treatment. We observed more severe chlorosis under Fe deficiency with cPTIO treatment for 9 d. These results strongly suggest that NO mediates a range of responses to Fe deficiency in M. xiaojinensis, from morphological changes to the regulation of physiological processes and gene expression. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

[Regulation effect of water storage in deeper soil layers on root physiological characteristics and leaf photosynthetic traits of cotton with drip irrigation under mulch].

PubMed

Luo, Hong-Hai; Zhang, Hong-Zhi; Du, Ming-Wei; Huang, Jian-Jun; Zhang, Ya-Li; Zhang, Wang-Feng

2009-06-01

A soil column culture experiment was conducted under the ecological and climatic conditions of Xinjiang to study the effects of water storage in deeper (> 60 cm) soil layers on the root physiological characteristics and leaf photosynthetic traits of cotton variety Xinluzao 13. Two treatments were installed, i.e., well-watered and no watering. The moisture content in plough layer was controlled at 70% +/- 5% and 55% +/- 5% of field capacity by drip irrigation under mulch during growth season. It was shown that the water storage in deeper soil layers enhanced the SOD activity and the vigor of cotton root, and increased the water use efficiency of plant as well as the leaf water potential, chlorophyll content, and net photosynthesis rate, which finally led to a higher yield of seed cotton and higher water use efficiency. Under well-watered condition and when the moisture content in plough layer was maintained at 55% of field capacity, the senescence of roots in middle and lower soil layers was slower, and the higher root vigor compensated the negative effects of impaired photosynthesis caused by water deficit to some extent. The yield of seed cotton was lower when the moisture content in plough layer was maintained at 55% of field capacity than at 70% of field capacity, but no significant difference was observed in the water use efficiency. Our results emphasized the importance of pre-sowing irrigation in winter or in spring to increase the water storage of deeper soil layers. In addition, proper cultivation practices and less frequent drip irrigation (longer intervals between successive rounds of irrigation) were also essential for conserving irrigation water and achieving higher yield.

Interplays between Soil-Borne Plant Viruses and RNA Silencing-Mediated Antiviral Defense in Roots

PubMed Central

Andika, Ida Bagus; Kondo, Hideki; Sun, Liying

2016-01-01

Although the majority of plant viruses are transmitted by arthropod vectors and invade the host plants through the aerial parts, there is a considerable number of plant viruses that infect roots via soil-inhabiting vectors such as plasmodiophorids, chytrids, and nematodes. These soil-borne viruses belong to diverse families, and many of them cause serious diseases in major crop plants. Thus, roots are important organs for the life cycle of many viruses. Compared to shoots, roots have a distinct metabolism and particular physiological characteristics due to the differences in development, cell composition, gene expression patterns, and surrounding environmental conditions. RNA silencing is an important innate defense mechanism to combat virus infection in plants, but the specific information on the activities and molecular mechanism of RNA silencing-mediated viral defense in root tissue is still limited. In this review, we summarize and discuss the current knowledge regarding RNA silencing aspects of the interactions between soil-borne viruses and host plants. Overall, research evidence suggests that soil-borne viruses have evolved to adapt to the distinct mechanism of antiviral RNA silencing in roots. PMID:27695446

Responses of seminal wheat seedling roots to soil water deficits.

PubMed

Trejo, Carlos; Else, Mark A; Atkinson, Christopher J

2018-04-01

The aims of this paper are to develop our understanding of the ways by which soil water deficits influence early wheat root growth responses, particularly how seminal roots respond to soil drying and the extent to which information on differences in soil water content are conveyed to the shoot and their impact on shoot behaviour. To achieve this, wheat seedlings have been grown, individually for around 25 days after germination in segmented soil columns within vertical plastic compartments. Roots were exposed to different soil volumetric moisture contents (SVMC) within the two compartments. Experiments where the soil in the lower compartment was allowed to dry to different extents, while the upper was maintained close to field capacity, showed that wheat seedlings allocated proportionally more root dry matter to the lower drier soil compartment. The total production of root, irrespective of the upper or lower SVMC, was similar and there were no detected effects on leaf growth rate or gas exchange. The response of seminal roots to proportionally increase their allocation of dry matter, to the drier soil was unexpected with such plasticity of roots system development traditionally linked to heterogeneous nutrient distribution than accessing soil water. In experiments where the upper soil compartment was allowed to dry, root growth slowed and leaf growth and gas exchange declined. Subsequent experiments used root growth rates to determine when seminal root tips first came into contact with drying soil, with the intentions of determining how the observed root growth rates were maintained as an explanation for the observed changes in root allocation. Measurements of seminal root ABA and ethylene from roots within the drying soil are interpreted with respect to what is known about the physiological control of root growth in drying soil. Copyright © 2018 Elsevier GmbH. All rights reserved.

Metabolomic Analysis of Alfalfa (Medicago sativa L.) Root-Symbiotic Rhizobia Responses under Alkali Stress.

PubMed

Song, Tingting; Xu, Huihui; Sun, Na; Jiang, Liu; Tian, Pu; Yong, Yueyuan; Yang, Weiwei; Cai, Hua; Cui, Guowen

2017-01-01

Alkaline salts (e.g., NaHCO 3 and Na 2 CO 3 ) causes more severe morphological and physiological damage to plants than neutral salts (e.g., NaCl and Na 2 SO 4 ) due to differences in pH. The mechanism by which plants respond to alkali stress is not fully understood, especially in plants having symbotic relationships such as alfalfa ( Medicago sativa L.). Therefore, a study was designed to evaluate the metabolic response of the root-nodule symbiosis in alfalfa under alkali stress using comparative metabolomics. Rhizobium-nodulized (RI group) and non-nodulized (NI group) alfalfa roots were treated with 200 mmol/L NaHCO 3 and, roots samples were analyzed for malondialdehydyde (MDA), proline, glutathione (GSH), superoxide dismutase (SOD), and peroxidase (POD) content. Additionally, metabolite profiling was conducted using gas chromatography combined with time-of-flight mass spectrometry (GC/TOF-MS). Phenotypically, the RI alfalfa exhibited a greater resistance to alkali stress than the NI plants examined. Physiological analysis and metabolic profiling revealed that RI plants accumulated more antioxidants (SOD, POD, GSH), osmolytes (sugar, glycols, proline), organic acids (succinic acid, fumaric acid, and alpha-ketoglutaric acid), and metabolites that are involved in nitrogen fixation. Our pairwise metabolomics comparisons revealed that RI alfalfa plants exhibited a distinct metabolic profile associated with alkali putative tolerance relative to NI alfalfa plants. Data provide new information about the relationship between non-nodulized, rhizobium-nodulized alfalfa and alkali resistance.

Metabolomic Analysis of Alfalfa (Medicago sativa L.) Root-Symbiotic Rhizobia Responses under Alkali Stress

PubMed Central

Song, Tingting; Xu, Huihui; Sun, Na; Jiang, Liu; Tian, Pu; Yong, Yueyuan; Yang, Weiwei; Cai, Hua; Cui, Guowen

2017-01-01

Alkaline salts (e.g., NaHCO3 and Na2CO3) causes more severe morphological and physiological damage to plants than neutral salts (e.g., NaCl and Na2SO4) due to differences in pH. The mechanism by which plants respond to alkali stress is not fully understood, especially in plants having symbotic relationships such as alfalfa (Medicago sativa L.). Therefore, a study was designed to evaluate the metabolic response of the root-nodule symbiosis in alfalfa under alkali stress using comparative metabolomics. Rhizobium-nodulized (RI group) and non-nodulized (NI group) alfalfa roots were treated with 200 mmol/L NaHCO3 and, roots samples were analyzed for malondialdehydyde (MDA), proline, glutathione (GSH), superoxide dismutase (SOD), and peroxidase (POD) content. Additionally, metabolite profiling was conducted using gas chromatography combined with time-of-flight mass spectrometry (GC/TOF-MS). Phenotypically, the RI alfalfa exhibited a greater resistance to alkali stress than the NI plants examined. Physiological analysis and metabolic profiling revealed that RI plants accumulated more antioxidants (SOD, POD, GSH), osmolytes (sugar, glycols, proline), organic acids (succinic acid, fumaric acid, and alpha-ketoglutaric acid), and metabolites that are involved in nitrogen fixation. Our pairwise metabolomics comparisons revealed that RI alfalfa plants exhibited a distinct metabolic profile associated with alkali putative tolerance relative to NI alfalfa plants. Data provide new information about the relationship between non-nodulized, rhizobium-nodulized alfalfa and alkali resistance. PMID:28744296

Molecular, physiological and morphological analysis of waterlogging tolerance in clonal genotypes of Theobroma cacao L.

PubMed

Bertolde, Fabiana Zanelato; De Almeida, Alex-Alan Furtado; Corrêa, Ronan Xavier; Gomes, Fábio Pinto; Gaiotto, Fernanda Amato; Baligar, Virupax C; Loguercio, Leandro Lopes

2010-01-01

In soil, anoxia conditions generated by waterlogging induce changes in genetic, morphological and physiological processes, altering the growth and development of plants. Mass propagation of cacao (Theobroma cacao L.) plantlets (clones) is affected by waterlogging caused by heavy rains and irrigation methods used to induce rooting. An experiment was undertaken to assess the effects of a 45-day flooding (anoxia) on physiological and morphological traits of 35 elite cacao genotypes, aiming at potentially identifying those with greater tolerance to flooding of the growth substrate. Eighteen fluorochrome-labeled microsatellite (SSR) primer pairs were used to assess genetic variability among clones, with 248 alleles being amplified and used to calculate similarity coefficients. The resulting dendrogram indicated the presence of four major groups, in which two represented 60% and 31% of the genotypes tested. A general trend toward high levels of heterozygosity was also found for physiological and morphological traits. The survival index (IS) for flood tolerance observed varied from 30 to 96%. Clones TSA-654, TSA-656, TSA-792, CA-1.4, CEPEC-2009 and PH-17 showed an IS value above 94%, whereas CEPEC-2010, CEPEC-2002, CA-7.1 and VB-903 clones were those mostly affected by waterlogging, with IS value below 56%. All genotypes displayed lenticel and adventitious root formation in response to waterlogging, although with different intensities. To determine whether patterns of physiological response could be associated with tolerance to anoxia, a similarity-grouping analysis was performed using the ratio between waterlogged and control values obtained for a series of physiological variables assessed. No specific pattern of physiological and morphological responses to waterlogging was strictly associated with survival of plantlets. However, results revealed by the dendrogram suggest that absence of leaf chlorosis may be a proper trait to indicate cacao clones with higher survival rates under flooding conditions. Consequences of these findings are discussed in the context of developing improved strategies for mass production of clones from elite cacao genotypes.

Root Architecture Diversity and Meristem Dynamics in Different Populations of Arabidopsis thaliana

PubMed Central

Aceves-García, Pamela; Álvarez-Buylla, Elena R.; Garay-Arroyo, Adriana; García-Ponce, Berenice; Muñoz, Rodrigo; Sánchez, María de la Paz

2016-01-01

Arabidopsis thaliana has been an excellent model system for molecular genetic approaches to development and physiology. More recently, the potential of studying various accessions collected from diverse habitats has been started to exploit. Col-0 has been the best-studied accession but we now know that several traits show significant divergences among them. In this work, we focused in the root that has become a key system for development. We studied root architecture and growth dynamics of 12 Arabidopsis accessions. Our data reveal a wide variability in root architecture and root length among accessions. We also found variability in the root apical meristem (RAM), explained mainly by cell size at the RAM transition domain and possibly by peculiar forms of organization at the stem cell niche in some accessions. Contrary to Col-0 reports, in some accessions the RAM size not always explains the variations in the root length; indicating that elongated cell size could be more relevant in the determination of root length than the RAM size itself. This study contributes to investigations dealing with understanding the molecular and cellular basis of phenotypic variation, the role of plasticity on adaptation, and the developmental mechanisms that may restrict phenotypic variation in response to contrasting environmental conditions. PMID:27379140

Root Architecture Diversity and Meristem Dynamics in Different Populations of Arabidopsis thaliana.

PubMed

Aceves-García, Pamela; Álvarez-Buylla, Elena R; Garay-Arroyo, Adriana; García-Ponce, Berenice; Muñoz, Rodrigo; Sánchez, María de la Paz

2016-01-01

Arabidopsis thaliana has been an excellent model system for molecular genetic approaches to development and physiology. More recently, the potential of studying various accessions collected from diverse habitats has been started to exploit. Col-0 has been the best-studied accession but we now know that several traits show significant divergences among them. In this work, we focused in the root that has become a key system for development. We studied root architecture and growth dynamics of 12 Arabidopsis accessions. Our data reveal a wide variability in root architecture and root length among accessions. We also found variability in the root apical meristem (RAM), explained mainly by cell size at the RAM transition domain and possibly by peculiar forms of organization at the stem cell niche in some accessions. Contrary to Col-0 reports, in some accessions the RAM size not always explains the variations in the root length; indicating that elongated cell size could be more relevant in the determination of root length than the RAM size itself. This study contributes to investigations dealing with understanding the molecular and cellular basis of phenotypic variation, the role of plasticity on adaptation, and the developmental mechanisms that may restrict phenotypic variation in response to contrasting environmental conditions.

Cyclotron-based effects on plant gravitropism

NASA Astrophysics Data System (ADS)

Kordyum, E.; Sobol, M.; Kalinina, Ia.; Bogatina, N.; Kondrachuk, A.

Primary roots exhibit positive gravitropism and grow in the direction of the gravitational vector, while shoots respond negatively and grow opposite to the gravitational vector. We first demonstrated that the use of a weak combined magnetic field (CMF), which is comprised of a permanent magnetic field and an alternating magnetic field with the frequency resonance of the cyclotron frequency of calcium ions, can change root gravitropism from a positive direction to negative direction. Two-day-old cress seedlings were gravistimulated in a chamber that was placed into a μ-metal shield where this CMF was created. Using this "new model" of a root gravitropic response, we have studied some of its components including the movement of amyloplasts-statoliths in root cap statocytes and the distribution of Ca 2+ ions in the distal elongation zone during gravistimulation. Unlike results from the control, amyloplasts did not sediment in the distal part of a statocyte, and more Ca 2+ accumulation was observed in the upper side of a gravistimulated root for seedlings treated with the CMF. For plants treated with the CMF, it appears that a root gravitropic reaction occurs by a normal physiological process resulting in root bending although in the opposite direction. These results support the hypothesis that both the amyloplasts in the root cap statocytes and calcium are important signaling components in plant gravitropism.

The symbiosis with the arbuscular mycorrhizal fungus Rhizophagus irregularis drives root water transport in flooded tomato plants.

PubMed

Calvo-Polanco, Monica; Molina, Sonia; Zamarreño, Angel María; García-Mina, Jose María; Aroca, Ricardo

2014-05-01

It is known that the presence of arbuscular mycorrhizal fungi within the plant roots enhances the tolerance of the host plant to different environmental stresses, although the positive effect of the fungi in plants under waterlogged conditions has not been well studied. Tolerance of plants to flooding can be achieved through different molecular, physiological and anatomical adaptations, which will affect their water uptake capacity and therefore their root hydraulic properties. Here, we investigated the root hydraulic properties under non-flooded and flooded conditions in non-mycorrhizal tomato plants and plants inoculated with the arbuscular mycorrhizal fungus Rhizophagus irregularis. Only flooded mycorrhizal plants increased their root hydraulic conductivity, and this effect was correlated with a higher expression of the plant aquaporin SlPIP1;7 and the fungal aquaporin GintAQP1. There was also a higher abundance of the PIP2 protein phoshorylated at Ser280 in mycorrhizal flooded plants. The role of plant hormones (ethylene, ABA and IAA) in root hydraulic properties was also taken into consideration, and it was concluded that, in mycorrhizal flooded plants, ethylene has a secondary role regulating root hydraulic conductivity whereas IAA may be the key hormone that allows the enhancement of root hydraulic conductivity in mycorrhizal plants under low oxygen conditions.

Global expression pattern comparison between low phosphorus insensitive 4 and WT Arabidopsis reveals an important role of reactive oxygen species and jasmonic acid in the root tip response to phosphate starvation

PubMed Central

Chacón-López, Alejandra; Ibarra-Laclette, Enrique; Sánchez-Calderón, Lenin; Gutiérrez-Alanís, Dolores

2011-01-01

Plants are exposed to several biotic and abiotic stresses. A common environmental stress that plants have to face both in natural and agricultural ecosystems that impacts both its growth and development is low phosphate (Pi) availability. There has been an important progress in the knowledge of the molecular mechanisms by which plants cope with Pi deficiency. However, the mechanisms that mediate alterations in the architecture of the Arabidopsis root system responses to Pi starvation are still largely unknown. One of the most conspicuous developmental effects of low Pi on the Arabidopsis root system is the inhibition of primary root growth that is accompanied by loss of root meristematic activity. To identify signalling pathways potentially involved in the Arabidpsis root meristem response to Pi-deprivation, here we report the global gene expression analysis of the root tip of wild type and low phosphorus insensitive4 (lpi4) mutant grown under Pi limiting conditions. Differential gene expression analysis and physiological experiments show that changes in the redox status, probably mediated by jasmonic acid and ethylene, play an important role in the primary root meristem exhaustion process triggered by Pi-starvation. PMID:21368582

Modification of cytogenetic and physiological effects of space flight factors by biologically active compounds

NASA Technical Reports Server (NTRS)

Aliyev, A. A.; Mekhti-Zade, E. R.; Mashinskiy, A. L.; Alekperov, U. K.

1986-01-01

Physiological and cytogenetic changes in the Welsh onion plants induced by a short (82 days) and long term (522 days) space flight are expressed in decrease of seed germination, inhibition of stem growth, depression of cell division in root meristem, and increase in the number of structural chromosome rearrangements. The treatment of such plants with solutions of a-tocopherol, auxin, and kinetin decreased the level of chromosome aberrations to the control one and normalized cell divisions and growth partly or completely.

Effects of Microclimate Cooling on Physiology and Performance While Flying the UH-60 Helicopter Simulator in NBC Conditions in a Controlled Heat Environment

DTIC Science & Technology

1992-08-01

including instrumenting and dressing the subjects, monitoring the physiological parameters in the simulator, and collecting and processing data. They...also was decided to extend the recruiting process to include all helicopter aviators, even if not UH-60 qualified. There is little in the flight profile...parameter channels, and the data were processed to produce a single root mean square (RMS) error value for each channel appropriate to each of the 9

Enhancing cytokinin synthesis by overexpressing ipt alleviated drought inhibition of root growth through activating ROS-scavenging systems in Agrostis stolonifera.

PubMed

Xu, Yi; Burgess, Patrick; Zhang, Xunzhong; Huang, Bingru

2016-03-01

Drought stress limits root growth and inhibits cytokinin (CK) production. Increases in CK production through overexpression of isopentenyltransferase (ipt) alleviate drought damages to promote root growth. The objective of this study was to investigate whether CK-regulated root growth was involved in the alteration of reactive oxygen species (ROS) production and ROS scavenging capacity under drought stress. Wild-type (WT) creeping bentgrass (Agrostis stolonifera L. 'Penncross') and a transgenic line (S41) overexpressing ipt ligated to a senescence-activated promoter (SAG12) were exposed to drought stress for 21 d in growth chambers. SAG12-ipt transgenic S41 developed a more extensive root system under drought stress compared to the WT. Root physiological analysis (electrolyte leakage and lipid peroxidation) showed that S41 roots exhibited less cellular damage compared to the WT under drought stress. Roots of SAG12-ipt transgenic S41 had significantly higher endogenous CK content than the WT roots under drought stress. ROS (hydrogen peroxide and superoxide) content was significantly lower and content of total and free ascorbate was significantly higher in S41 roots compared to the WT roots under drought stress. Enzymatic assays and transcript abundance analysis showed that superoxide dismutase, catalase, peroxidase, and dehydroascorbate reductase were significantly higher in S41 roots compared to the WT roots under drought stress. S41 roots also maintained significantly higher alternative respiration rates compared to the WT under drought stress. The improved root growth of transgenic creeping bentgrass may be facilitated by CK-enhanced ROS scavenging through antioxidant accumulation and activation of antioxidant enzymes, as well as higher alternative respiration rates when soil water is limited. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Enhancing cytokinin synthesis by overexpressing ipt alleviated drought inhibition of root growth through activating ROS-scavenging systems in Agrostis stolonifera

PubMed Central

Xu, Yi; Burgess, Patrick; Zhang, Xunzhong; Huang, Bingru

2016-01-01

Drought stress limits root growth and inhibits cytokinin (CK) production. Increases in CK production through overexpression of isopentenyltransferase (ipt) alleviate drought damages to promote root growth. The objective of this study was to investigate whether CK-regulated root growth was involved in the alteration of reactive oxygen species (ROS) production and ROS scavenging capacity under drought stress. Wild-type (WT) creeping bentgrass (Agrostis stolonifera L. ‘Penncross’) and a transgenic line (S41) overexpressing ipt ligated to a senescence-activated promoter (SAG12) were exposed to drought stress for 21 d in growth chambers. SAG12-ipt transgenic S41 developed a more extensive root system under drought stress compared to the WT. Root physiological analysis (electrolyte leakage and lipid peroxidation) showed that S41 roots exhibited less cellular damage compared to the WT under drought stress. Roots of SAG12-ipt transgenic S41 had significantly higher endogenous CK content than the WT roots under drought stress. ROS (hydrogen peroxide and superoxide) content was significantly lower and content of total and free ascorbate was significantly higher in S41 roots compared to the WT roots under drought stress. Enzymatic assays and transcript abundance analysis showed that superoxide dismutase, catalase, peroxidase, and dehydroascorbate reductase were significantly higher in S41 roots compared to the WT roots under drought stress. S41 roots also maintained significantly higher alternative respiration rates compared to the WT under drought stress. The improved root growth of transgenic creeping bentgrass may be facilitated by CK-enhanced ROS scavenging through antioxidant accumulation and activation of antioxidant enzymes, as well as higher alternative respiration rates when soil water is limited. PMID:26889010

Foxtail Millet [Setaria italica (L.) Beauv.] Grown under Low Nitrogen Shows a Smaller Root System, Enhanced Biomass Accumulation, and Nitrate Transporter Expression.

PubMed

Nadeem, Faisal; Ahmad, Zeeshan; Wang, Ruifeng; Han, Jienan; Shen, Qi; Chang, Feiran; Diao, Xianmin; Zhang, Fusuo; Li, Xuexian

2018-01-01

Foxtail millet (FM) [ Setaria italica (L.) Beauv.] is a grain and forage crop well adapted to nutrient-poor soils. To date little is known how FM adapts to low nitrogen (LN) at the morphological, physiological, and molecular levels. Using the FM variety Yugu1, we found that LN led to lower chlorophyll contents and N concentrations, and higher root/shoot and C/N ratios and N utilization efficiencies under hydroponic culture. Importantly, enhanced biomass accumulation in the root under LN was in contrast to a smaller root system, as indicated by significant decreases in total root length; crown root number and length; and lateral root number, length, and density. Enhanced carbon allocation toward the root was rather for significant increases in average diameter of the LN root, potentially favorable for wider xylem vessels or other anatomical alterations facilitating nutrient transport. Lower levels of IAA and CKs were consistent with a smaller root system and higher levels of GA may promote root thickening under LN. Further, up-regulation of SiNRT1.1, SiNRT2.1, and SiNAR2.1 expression and nitrate influx in the root and that of SiNRT1.11 and SiNRT1.12 expression in the shoot probably favored nitrate uptake and remobilization as a whole. Lastly, more soluble proteins accumulated in the N-deficient root likely as a result of increases of N utilization efficiencies. Such "excessive" protein-N was possibly available for shoot delivery. Thus, FM may preferentially transport carbon toward the root facilitating root thickening/nutrient transport and allocate N toward the shoot maximizing photosynthesis/carbon fixation as a primary adaptive strategy to N limitation.

Lifting date affects black walnut planting stock quality.

Treesearch

W.J. Rietveld; Robert D. Williams

1981-01-01

Presents information for black walnut seedlings on storage chilling requirement, fall lifting for overwinter storage, spring lifting, planting times, use of root regeneration potential (RRP) to assess physiological quality of planting stock, and relation between RRP at planting and field performance.

Organ-specific proteomics of soybean seedlings under flooding and drought stresses.

PubMed

Wang, Xin; Khodadadi, Ehsaneh; Fakheri, Baratali; Komatsu, Setsuko

2017-06-06

Organ-specific analyses enrich the understanding of plant growth and development under abiotic stresses. To elucidate the cellular responses in soybean seedlings exposed to flooding and drought stresses, organ-specific analysis was performed using a gel-free/label-free proteomic technique. Physiological analysis indicated that enzyme activities of alcohol dehydrogenase and delta-1-pyrroline-5-carboxylate synthase were markedly increased in leaf and root of plants treated with 6days of flooding and drought stresses, respectively. Proteins related to photosynthesis, RNA, DNA, signaling, and the tricarboxylic acid cycle were predominately affected in leaf, hypocotyl, and root in response to flooding and drought. Notably, the tricarboxylic acid cycle was suppressed in leaf and root under both stresses. Moreover, 17 proteins, including beta-glucosidase 31 and beta-amylase 5, were identified in soybean seedlings under both stresses. The protein abundances of beta-glucosidase 31 and beta-amylase 5 were increased in leaf and root under both stresses. Additionally, the gene expression of beta-amylase 5 was upregulated in leaf exposed to the flooding and drought, and the expression level was highly correlated with the protein abundance. These results suggest that beta-amylase 5 may be involved in carbohydrate mobilization to provide energy to the leaf of soybean seedlings exposed to flooding and drought. This study examined the effects of flooding and drought on soybean seedlings in different organs using a gel-free/label-free proteomic approach. Physiological responses indicated that enzyme activities of alcohol dehydrogenase and delta-1-pyrroline-5-carboxylate synthase were increased in leaf and root of soybean seedlings exposed to flooding and drought for 6days. Functional analysis of acquired protein profiles exhibited that proteins related to photosynthesis, RNA, DNA, signaling, and the tricarboxylic acid cycle were predominated affected in leaf, hypocotyl, and root under both stresses. Moreover, the tricarboxylic acid cycle was suppressed in leaf and root of stressed soybean seedlings. Additionally, increased protein abundance of beta-amylase 5 was consistent with upregulated gene expression in the leaf under both stresses, suggesting that carbohydrate metabolism might be governed in response to flooding and drought of soybean seedlings. Copyright © 2017 Elsevier B.V. All rights reserved.

Transcriptional and physiological analyses of Fe deficiency response in maize reveal the presence of Strategy I components and Fe/P interactions.

PubMed

Zanin, Laura; Venuti, Silvia; Zamboni, Anita; Varanini, Zeno; Tomasi, Nicola; Pinton, Roberto

2017-02-13

Under limited iron (Fe) availability maize, a Strategy II plant, improves Fe acquisition through the release of phytosiderophores (PS) into the rhizosphere and the subsequent uptake of Fe-PS complexes into root cells. Occurrence of Strategy-I-like components and interactions with phosphorous (P) nutrition has been hypothesized based on molecular and physiological studies in grasses. In this report transcriptomic analysis (NimbleGen microarray) of Fe deficiency response revealed that maize roots modulated the expression levels of 724 genes (508 up- and 216 down-regulated, respectively). As expected, roots of Fe-deficient maize plants overexpressed genes involved in the synthesis and release of 2'-deoxymugineic acid (the main PS released by maize roots). A strong modulation of genes involved in regulatory aspects, Fe translocation, root morphological modification, primary metabolic pathways and hormonal metabolism was induced by the nutritional stress. Genes encoding transporters for Fe 2+ (ZmNRAMP1) and P (ZmPHT1;7 and ZmPHO1) were also up-regulated under Fe deficiency. Fe-deficient maize plants accumulated higher amounts of P than the Fe-sufficient ones, both in roots and shoots. The supply of 1 μM 59 Fe, as soluble (Fe-Citrate and Fe-PS) or sparingly soluble (Ferrihydrite) sources to deficient plants, caused a rapid down-regulation of genes coding for PS and Fe(III)-PS transport, as well as of ZmNRAMP1 and ZmPHT1;7. Levels of 32 P absorption essentially followed the rates of 59 Fe uptake in Fe-deficient plants during Fe resupply, suggesting that P accumulation might be regulated by Fe uptake in maize plants. The transcriptional response to Fe-deficiency in maize roots confirmed the modulation of known genes involved in the Strategy II and revealed the presence of Strategy I components usually described in dicots. Moreover, data here presented provide evidence of a close relationship between two essential nutrients for plants, Fe and P, and highlight a key role played by Fe and P transporters to preserve the homeostasis of these two nutrients in maize plants.

The compensation effects of physiology and yield in cotton after drought stress.

PubMed

Niu, Jing; Zhang, Siping; Liu, Shaodong; Ma, Huijuan; Chen, Jing; Shen, Qian; Ge, Changwei; Zhang, Xiaomeng; Pang, Chaoyou; Zhao, Xinhua

The objective of this study was to investigate the root growth compensatory effects and cotton yield under drought stress. The results indicate that the root dry weight, boll weight, and cotton yield increased in both the drought-resistant cultivar (CCRI-45) and the drought-sensitive cultivar (CCRI-60). Compensation effects were exhibited under the three-day drought stress treatment at a soil relative water content (SRWC) of 60% and 45% during the seedling stage, and flowering and boll-forming stage over two years. The yield of the drought-resistant cultivar (CCRI-45) was higher than the control, however, following the six-day 45% SRWC drought treatments, the yield of the drought-sensitive cultivar (CCRI-60) was lower than the control. The soluble sugar content, proline content, superoxide dismutase (SOD) activity, and peroxidase (POD) activity of the roots increased under drought stress and then decreased after re-watering, although the values remained higher than those of the controls for a short period. These physiological measures may represent stress reactions and thus may not indicate factors that result in compensation effects. However, catalase (CAT) activity and gibberellic acid (GA) content of the roots decreased under drought stress. After re-watering, the CAT activity and the GA content increased and were significantly higher than those of the controls under the six-day 60% SRWC and 45% SRWC drought treatments. The abscisic acid (ABA) content of the roots increased under drought stress. After re-watering, the ABA content decreased to a lower level under the three and six-day 60% SRWC and 45% SRWC drought treatments than in the controls. According to an analysis of various indicators, the interaction between ABA and GA signals may play an important role in root growth compensatory effects. In summary, the results demonstrate that moderate drought stress is beneficial to root growth and yield. This conclusion is of great significance to improving our understanding of the maximum utilization of limited water resources. Copyright © 2018 The Authors. Published by Elsevier GmbH.. All rights reserved.

An Integrated View of Whole-Tree Hydraulic Architecture. Does Stomatal or Hydraulic Conductance Determine Whole Tree Transpiration?

PubMed Central

Rodríguez-Gamir, Juan; Primo-Millo, Eduardo; Forner-Giner, María Ángeles

2016-01-01

Hydraulic conductance exerts a strong influence on many aspects of plant physiology, namely: transpiration, CO2 assimilation, growth, productivity or stress response. However we lack full understanding of the contribution of root or shoot water transport capacity to the total water balance, something which is difficult to study in trees. Here we tested the hypothesis that whole plant hydraulic conductance modulates plant transpiration using two different seedlings of citrus rootstocks, Poncirus trifoliata (L.) Raf. and Cleopatra mandarin (Citrus reshni Hort ex Tan.). The two genotypes presented important differences in their root or shoot hydraulic conductance contribution to whole plant hydraulic conductance but, even so, water balance proved highly dependent on whole plant conductance. Further, we propose there is a possible equilibrium between root and shoot hydraulic conductance, similar to that between shoot and root biomass production, which could be related with xylem anatomy. PMID:27223695

Biochemical Composition Suggests Different Roles of Leaf Litter and Fine Roots in Soil Carbon Formation

NASA Astrophysics Data System (ADS)

Xia, M.; Pregitzer, K. S.; Talhelm, A. F.

2012-12-01

Plant litter is a major source of soil organic carbon (C). This litter is not homogenous, but instead primarily composed of fine root and leaf litter that adapted to different physiological functions. These unique functions suggest that root and leaf litter likely have different biochemical traits, and thus different decomposition patterns. However, few studies have compared their substrate quality and contributions to soil C. Also, much less attention has been given to fine roots although they can represent a substantial litter production. Here we hypothesize that 1) leaf litter and fine roots have different substrate quality as they are highly different in biochemical composition; 2) the biochemical composition of leaf litter and fine roots responds differently to the simulated nitrogen (N) deposition. To test these hypotheses, we collected leaf litter and fine roots of Acer saccharum (the dominant species in the northern temperate ecosystems we studied) in both ambient and N addition treatment plots at four sites of Michigan N deposition gradient study. We quantified ten biochemical components thought to be important on decomposition. Strikingly, we found a consistently three-fold higher lignin concentration in fine roots than that in leaf litter (P< 0.01). On average, lignin concentration of fine roots was 45.4±0.3% while that of leaf litter was 13.5±0.2%. Lignin has been considered highly recalcitrant and hypothesized as the major precursor of humus substance. Condensed tannin (CT) concentration in fine roots (13.13±0.51%) was also substantially higher than that in leaf litter (P< 0.01, 4.63±0.42 %). Tissue CT can inhibit litter decay by both precipitating proteins and by having antimicrobial properties. In contrast, fine roots exhibited lower concentrations of non-structural carbohydrates (NSC), soluble phenolics, and holocellulose (hemicelluloses & cellulose) than leaf litter (P< 0.01). These components are considered more easily accessible, and may stimulate the decay of lignin by providing required energy. Therefore, fine roots of Acer saccharum have a relatively recalcitrant nature based on their distinct biochemical composition, suggesting fine roots may be the major driver of soil carbon formation in the ecosystems we studied. Litter type and N addition had significant interactions on lignin, holocellulose, and NSC (P< 0.05), indicating these traits of different litter types respond differently to N addition. In leaf litter, the concentrations of lignin, NSC, and bound CT were affected by N addition (P< 0.05). By contrast, N addition only reduced the soluble protein concentration in fine roots (P< 0.05). Hence, substrate quality of leaf litter and fine roots responds differently to the simulated N deposition, and may eventually lead to different responses in decomposition pattern. This is one of few studies comparing the detailed biochemical profile of leaf litter and fine roots in a dominant tree species. Different biochemical traits of fine roots and leaf litter may reflect the different specializations for their physiological functions. This work highlights the importance of fine root in the soil carbon formation due to its recalcitrant nature, and emphasizes the necessity of differentiating the responses of leaf litter and fine root decompositions to environmental changes when modeling biogeochemical cycles.

Arbuscular mycorrhizal symbiosis increases relative apoplastic water flow in roots of the host plant under both well-watered and drought stress conditions.

PubMed

Bárzana, Gloria; Aroca, Ricardo; Paz, José Antonio; Chaumont, François; Martinez-Ballesta, Mari Carmen; Carvajal, Micaela; Ruiz-Lozano, Juan Manuel

2012-04-01

The movement of water through mycorrhizal fungal tissues and between the fungus and roots is little understood. It has been demonstrated that arbuscular mycorrhizal (AM) symbiosis regulates root hydraulic properties, including root hydraulic conductivity. However, it is not clear whether this effect is due to a regulation of root aquaporins (cell-to-cell pathway) or to enhanced apoplastic water flow. Here we measured the relative contributions of the apoplastic versus the cell-to-cell pathway for water movement in roots of AM and non-AM plants. We used a combination of two experiments using the apoplastic tracer dye light green SF yellowish and sodium azide as an inhibitor of aquaporin activity. Plant water and physiological status, root hydraulic conductivity and apoplastic water flow were measured. Roots of AM plants enhanced significantly relative apoplastic water flow as compared with non-AM plants and this increase was evident under both well-watered and drought stress conditions. The presence of the AM fungus in the roots of the host plants was able to modulate the switching between apoplastic and cell-to-cell water transport pathways. The ability of AM plants to switch between water transport pathways could allow a higher flexibility in the response of these plants to water shortage according to the demand from the shoot.

Arbuscular mycorrhizal symbiosis increases relative apoplastic water flow in roots of the host plant under both well-watered and drought stress conditions

PubMed Central

Bárzana, Gloria; Aroca, Ricardo; Paz, José Antonio; Chaumont, François; Martinez-Ballesta, Mari Carmen; Carvajal, Micaela; Ruiz-Lozano, Juan Manuel

2012-01-01

Background and Aims The movement of water through mycorrhizal fungal tissues and between the fungus and roots is little understood. It has been demonstrated that arbuscular mycorrhizal (AM) symbiosis regulates root hydraulic properties, including root hydraulic conductivity. However, it is not clear whether this effect is due to a regulation of root aquaporins (cell-to-cell pathway) or to enhanced apoplastic water flow. Here we measured the relative contributions of the apoplastic versus the cell-to-cell pathway for water movement in roots of AM and non-AM plants. Methods We used a combination of two experiments using the apoplastic tracer dye light green SF yellowish and sodium azide as an inhibitor of aquaporin activity. Plant water and physiological status, root hydraulic conductivity and apoplastic water flow were measured. Key Results Roots of AM plants enhanced significantly relative apoplastic water flow as compared with non-AM plants and this increase was evident under both well-watered and drought stress conditions. The presence of the AM fungus in the roots of the host plants was able to modulate the switching between apoplastic and cell-to-cell water transport pathways. Conclusions The ability of AM plants to switch between water transport pathways could allow a higher flexibility in the response of these plants to water shortage according to the demand from the shoot. PMID:22294476

Contrasting responses of root morphology and root-exuded organic acids to low phosphorus availability in three important food crops with divergent root traits.

PubMed

Wang, Yan-Liang; Almvik, Marit; Clarke, Nicholas; Eich-Greatorex, Susanne; Øgaard, Anne Falk; Krogstad, Tore; Lambers, Hans; Clarke, Jihong Liu

2015-08-17

Phosphorus (P) is an important element for crop productivity and is widely applied in fertilizers. Most P fertilizers applied to land are sorbed onto soil particles, so research on improving plant uptake of less easily available P is important. In the current study, we investigated the responses in root morphology and root-exuded organic acids (OAs) to low available P (1 μM P) and sufficient P (50 μM P) in barley, canola and micropropagated seedlings of potato-three important food crops with divergent root traits, using a hydroponic plant growth system. We hypothesized that the dicots canola and tuber-producing potato and the monocot barley would respond differently under various P availabilities. WinRHIZO and liquid chromatography triple quadrupole mass spectrometry results suggested that under low P availability, canola developed longer roots and exhibited the fastest root exudation rate for citric acid. Barley showed a reduction in root length and root surface area and an increase in root-exuded malic acid under low-P conditions. Potato exuded relatively small amounts of OAs under low P, while there was a marked increase in root tips. Based on the results, we conclude that different crops show divergent morphological and physiological responses to low P availability, having evolved specific traits of root morphology and root exudation that enhance their P-uptake capacity under low-P conditions. These results could underpin future efforts to improve P uptake of the three crops that are of importance for future sustainable crop production. Published by Oxford University Press on behalf of the Annals of Botany Company.

Effect of off-season flooding on growth, photosynthesis, carbohydrate partitioning, and nutrient uptake in Distylium chinense.

PubMed

Liu, Zebin; Cheng, Ruimei; Xiao, Wenfa; Guo, Quanshui; Wang, Na

2014-01-01

Distylium chinense is an evergreen shrub used for the vegetation recovery of floodplain and riparian areas in Three Gorges Reservoir Region. To clarify the morphological and physiological responses and tolerance of Distylium chinense to off-season flooding, a simulation flooding experiment was conducted during autumn and winter. Results indicated that the survival rate of seedlings was 100%, and that plant height and stem diameter were not significantly affected by flooding. Adventitious roots and hypertrophic lenticels were observed in flooded seedlings after 30 days of flooding. Flooding significantly reduced the plant biomass of roots, net photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), maximum photochemical efficiency (Fv/Fm), photochemical quenching (qP), and electron transport rate (ETR) in leaves, and also affected the allocation and transport of carbohydrate and nutrients. However, D. chinense was able to maintain stable levels of Pn, Fv/Fm, qP, ETR, and nutrient content (N and P) in leaves and to store a certain amount of carbohydrate in roots over prolonged durations of flooding. Based on these results, we conclude that there is a high flooding tolerance in D. chinense, and the high survival rate of D. chinense may be attributable to a combination of morphological and physiological responses to flooding.

Melatonin attenuates postharvest physiological deterioration of cassava storage roots.

PubMed

Ma, Qiuxiang; Zhang, Ting; Zhang, Peng; Wang, Zhen-Yu

2016-05-01

Melatonin reportedly increases abiotic and biotic stress tolerance in plants, but information on its in vivo effects during postharvest physiological deterioration (PPD) in cassava is limited. In this study, we investigated the effect of melatonin in regulating cassava PPD. Treatment with 500 mg/L melatonin significantly delayed cassava PPD and reduced the accumulation of hydrogen peroxide (H2O2) while increasing the activity of superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR), but not ascorbate peroxidase (APX). Transcript analysis further showed that expression of copper/zinc SOD (MeCu/ZnSOD), MeCAT1, glutathione peroxidase (MeGPX), peroxidase 3 (MePX3), and glutathione S-transferases (MeGST) was higher in cassava roots sliced treated with 500 mg/L melatonin than in those not exposed to exogenous melatonin. These data demonstrate that melatonin delays cassava PPD by directly or indirectly maintaining homoeostasis of cellular reactive oxygen species (ROS). We also found that accumulation of endogenous melatonin and the transcript levels of melatonin biosynthesis genes changed dynamically during the PPD process. This finding suggested that endogenous melatonin acts as a signal modulator for maintaining cassava PPD progression and that manipulation of melatonin biosynthesis genes through genetic engineering might prevent cassava root deterioration. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Exploratory Project: Rigid nanostructured organic polymer monolith for in situ collection and analysis of plant metabolites from soil matrices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tharayil, Nishanth

Plant metabolites released from litter leachates and root exudates enable plants to adapt and survive in a wide range of habitats by facilitating resource foraging and plant-organismal interactions, and could influence soil carbon storage. The biological functions of these plant inputs and the organismal interactions they facilitate in soil are strictly governed by their composition and molecular identity. Our current understanding about the molecular identity of exudates is based on physiological studies that are done in soil-less axenic cultures. On the other hand, ecological studies that rely on isotope labeling to track the fluxes of carbon from plants to soilmore » have found the complexities of soil-microbe matrices as an insurmountable barrier to undertake any meaningful molecular level characterization of plant inputs. Although it is constantly advocated to undertake a molecular level identification of the dynamicity of plant metabolites in soils, the complexity of soil system has thus far prevented any such endeavors. We developed polymeric probes through in-situ polymerization of poly(styrene-co-vinylbenzyl chloride-co-divinylbenzene) to elucidate the chemical environment of the soil to which the plant roots are exposed. Hypercrosslinking of the polymeric probes through an in-situ Friedel-Crafts alkylation significantly increased the surface area and the sorption capacity of the probes. Surface functionalization of the probes using a hybrid approach was also attempted. The efficacy of these probes was tested using batch equilibration. Scanning electron microscopy revealed extensive modification of the surface of the probes through hypercrosslinking. The probes exhibited a lower site specific sorption (slope of Freundlich adsorption isotherm close to unity) and percent recovery of the sorbed compounds from the probes were >70, indicating a predominance of reversible sorption. Further we imparted specificity to this copolymer matrix by using molecular-template imprinting approach for the selective capture of less abundant plant metabolites from a crowded soil/litter leachate. Our results suggests that i) the root exudate pattern of plants is highly dependent on the nutrient status of the plant, with greater specificity of root exudation occurring in growing medium with low available form of nutrients, ii) the chemical composition of root exudation is a function of the distance of sampling from the source-roots, with the composition of root exudation being more enriched in polar metabolites farther from the source-roots, iii) Further we demonstrated that the compounds present in real root exudates diffuse farther from the source roots than those in artificial root exudates that are traditionally used. Thus, our project highlights how the soil matrix is instrumental in modifying the chemical composition of root exudates, and highlights that, apart from the plant physiology, the specificity and function of root exudates is also modified by environmental factors.« less

Domestication and Crop Physiology: Roots of Green-Revolution Wheat

PubMed Central

Waines, J. Giles; Ehdaie, Bahman

2007-01-01

Background and Aims Most plant scientists, in contrast to animal scientists, study only half the organism, namely above-ground stems, leaves, flowers and fruits, and neglect below-ground roots. Yet all acknowledge roots are important for anchorage, water and nutrient uptake, and presumably components of yield. This paper investigates the relationship between domestication, and the root systems of landraces, and the parents of early, mid- and late green-revolution bread wheat cultivars. It compares the root system of bread wheat and ‘Veery’-type wheat containing the 1RS translocation from rye. Methods Wheat germplasm was grown in large pots in sand culture in replicated experiments. This allowed roots to be washed free to study root characters. Key Results The three bread wheat parents of early green-revolution wheats have root biomass less than two-thirds the mean of some landrace wheats. Crossing early green-revolution wheat to an F2 of ‘Norin 10’ and ‘Brevor’, further reduced root biomass in mid-generation semi-dwarf and dwarf wheats. Later-generation semi-dwarf wheats show genetic variation for root biomass, but some exhibit further reduction in root size. This is so for some California and UK wheats. The wheat–rye translocation in ‘Kavkaz’ for the short arm of chromosome 1 (1RS) increased root biomass and branching in cultivars that contained it. Conclusions Root size of modern cultivars is small compared with that of landraces. Their root system may be too small for optimum uptake of water and nutrients and maximum grain yield. Optimum root size for grain yield has not been investigated in wheat or most crop plants. Use of 1RS and similar alien translocations may increase root biomass and grain yield significantly in irrigated and rain-fed conditions. Root characters may be integrated into components of yield analysis in wheat. Plant breeders may need to select directly for root characters. PMID:17940075

The regulatory network of cluster-root function and development in phosphate-deficient white lupin (Lupinus albus) identified by transcriptome sequencing.

PubMed

Wang, Zhengrui; Straub, Daniel; Yang, Huaiyu; Kania, Angelika; Shen, Jianbo; Ludewig, Uwe; Neumann, Günter

2014-07-01

Lupinus albus serves as model plant for root-induced mobilization of sparingly soluble soil phosphates via the formation of cluster-roots (CRs) that mediate secretion of protons, citrate, phenolics and acid phosphatases (APases). This study employed next-generation sequencing to investigate the molecular mechanisms behind these complex adaptive responses at the transcriptome level. We compared different stages of CR development, including pre-emergent (PE), juvenile (JU) and the mature (MA) stages. The results confirmed that the primary metabolism underwent significant modifications during CR maturation, promoting the biosynthesis of organic acids, as had been deduced from physiological studies. Citrate catabolism was downregulated, associated with citrate accumulation in MA clusters. Upregulation of the phenylpropanoid pathway reflected the accumulation of phenolics. Specific transcript expression of ALMT and MATE transporter genes correlated with the exudation of citrate and flavonoids. The expression of transcripts related to nucleotide degradation and APases in MA clusters coincided with the re-mobilization and hydrolysis of organic phosphate resources. Most interestingly, hormone-related gene expression suggested a central role of ethylene during CR maturation. This was associated with the upregulation of the iron (Fe)-deficiency regulated network that mediates ethylene-induced expression of Fe-deficiency responses in other species. Finally, transcripts related to abscisic acid and jasmonic acid were upregulated in MA clusters, while auxin- and brassinosteroid-related genes and cytokinin receptors were most strongly expressed during CR initiation. Key regulations proposed by the RNA-seq data were confirmed by quantitative real-time polymerase chain reaction (RT-qPCR) and some physiological analyses. A model for the gene network regulating CR development and function is presented. © 2014 Scandinavian Plant Physiology Society.

Aqueous extracts and polysaccharides from Marshmallow roots (Althea officinalis L.): cellular internalisation and stimulation of cell physiology of human epithelial cells in vitro.

PubMed

Deters, Alexandra; Zippel, Janina; Hellenbrand, Nils; Pappai, Dirk; Possemeyer, Cathleen; Hensel, Andreas

2010-01-08

Aqueous extracts from the roots of Althea officinalis L. (Malvaceae) are widely used for treatment of irritated mucosa. The clinical proven effects are related to the presence of bioadhesive and mucilaginous polysaccharides from the rhamnogalacturonan type, leading to the physical formation of mucin-like on top of the irritated tissues. No data are available if the extracts or the polysaccharides from these extract exert an active influence on mucosal or connective tissue cells, in order to initiated changes in cell physiology, useful for better tissue regeneration. In vitro investigations of aqueous A. officinalis extract AE and raw polysaccharides (RPS) on epithelial KB cells and primary dermal human fibroblasts (pNHF) using WST1 vitality test and BrdU proliferation ELISA. Gene expression analysis by microarray from KB cells. Internalisation studies of polysaccharides were performed by laser scanning microscopy. AE (1, 10 microg/mL) had stimulating effect on cell viability and proliferation of epithelial KB cells. RPS (1, 10 microg/mL) stimulated cell vitality of epithelial cells significantly without triggering the cells into higher proliferation status. Neither AE nor RPS had any effect on fibroblasts. FITC-labeled RPS was shown to be internalised into epithelial cells, but not into fibroblasts. FITC-RPS was shown to form bioadhesive layers on the cell surface of dermal fibroblasts. Microarray analysis indicated an up-regulation of genes related to cell adhesion proteins, growth regulators, extracellular matrix, cytokine release and apoptosis. Aqueous extracts and polysaccharides from the roots of A. officinalis are effective stimulators of cell physiology of epithelial cells which can prove the traditional use of Marshmallow preparations for treatment of irritated mucous membranes within tissue regeneration. Copyright 2009 Elsevier Ireland Ltd. All rights reserved.

Physiological and biochemical perspectives of non-salt tolerant plants during bacterial interaction against soil salinity.

PubMed

Radhakrishnan, Ramalingam; Baek, Kwang Hyun

2017-07-01

Climatic changes on earth affect the soil quality of agricultural lands, especially by increasing salt deposition in soil, which results in soil salinity. Soil salinity is a major challenge to growth and reproduction among glycophytes (including all crop plants). Soil bacteria present in the rhizosphere and/or roots naturally protect plants from the adverse effects of soil salinity by reprogramming the stress-induced physiological changes in plants. Bacteria can enrich the soil with major nutrients (nitrogen, phosphorus, and potassium) in a form easily available to plants and prevent the transport of excess sodium to roots (exopolysaccharides secreted by bacteria bind with sodium ions) for maintaining ionic balance and water potential in cells. Salinity also affects plant growth regulators and suppresses seed germination and root and shoot growth. Bacterial secretion of indole-3-acetic acid and gibberellins compensates for the salt-induced hormonal decrease in plants, and bacterial 1-aminocyclopropane-1-carboxylate (ACC) deaminase synthesis decreases ethylene production to stimulate plant growth. Furthermore, bacteria modulate the redox state of salinity-affected plants by enhancing antioxidants and polyamines, which leads to increased photosynthetic efficiency. Bacteria-induced accumulation of compatible solutes in stressed plants regulates plant cellular activities and prevents salt stress damage. Plant-bacterial interaction reprograms the expression of salt stress-responsive genes and proteins in salinity-affected plants, resulting in a precise stress mitigation metabolism as a defense mechanism. Soil bacteria increase the fertility of soil and regulate the plant functions to prevent the salinity effects in glycophytes. This review explains the current understanding about the physiological changes induced in glycophytes during bacterial interaction to alleviate the adverse effects of soil salinity stress. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Characteristics of a root hair-less line of Arabidopsis thaliana under physiological stresses.

PubMed

Tanaka, Natsuki; Kato, Mariko; Tomioka, Rie; Kurata, Rie; Fukao, Yoichiro; Aoyama, Takashi; Maeshima, Masayoshi

2014-04-01

The plasma membrane-associated Ca(2+)-binding protein-2 of Arabidopsis thaliana is involved in the growth of root hair tips. Several transgenic lines that overexpress the 23 residue N-terminal domain of this protein under the control of the root hair-specific EXPANSIN A7 promoter lack root hairs completely. The role of root hairs under normal and stress conditions was examined in one of these root hair-less lines (NR23). Compared with the wild type, NR23 showed a 47% reduction in water absorption, decreased drought tolerance, and a lower ability to adapt to heat. Growth of NR23 was suppressed in media deficient in phosphorus, iron, calcium, zinc, copper, or potassium. Also, the content of an individual mineral in NR23 grown in normal medium, or in medium lacking a specific mineral, was relatively low. In wild-type plants, the primary and lateral roots produce numerous root hairs that become elongated under phosphate-deficient conditions; NR23 did not produce root hairs. Although several isoforms of the plasma membrane phosphate transporters including PHT1;1-PHT1;6 were markedly induced after growth in phosphate-deficient medium, the levels induced in NR23 were less than half those observed in the wild type. In phosphate-deficient medium, the amounts of acid phosphatase, malate, and citrate secreted from NR23 roots were 38, 9, and 16% of the levels secreted from wild-type roots. The present results suggest that root hairs play significant roles in the absorption of water and several minerals, secretion of acid phosphatase(s) and organic acids, and in penetration of the primary roots into gels.

Facilitation of amphibious habit by physiological integration in the clonal, perennial, climbing herb Ipomoea aquatica.

PubMed

Lin, Hui-Feng; Alpert, Peter; Zhang, Qian; Yu, Fei-Hai

2018-03-15

Physiological integration of connected ramets of clonal plants can increase clonal performance when ramets grow in contrasting microenvironments within a habitat. In amphibious clonal species, integration of ramets in different habitats, terrestrial and aquatic, is possible. This may increase performance of amphibious clones, especially under eutrophic conditions. To test this, clonal fragments consisting of two ramets of the amphibious, perennial, climbing herb Ipomoea aquatica connected by a stem were placed such that the proximal ramet was rooted in a simulated riparian community of four other species, while the distal ramet extended into a simulated aquatic habitat with open water and sediment. The connection between ramets was either left intact or severed, and 0, 5, or 25mg N L -1 was added to the aquatic habitat to simulate different degrees of eutrophication. Without added N, fragments in which the original ramets were left connected accumulated two times more total mass than fragments in which the ramets were disconnected from one another. The positive effect of connection increased two-fold with increasing N. These results were consistent with the hypotheses that physiological integration between connected terrestrial and aquatic ramets can increase clonal performance in plants and that this effect can be greater when the aquatic ramet is richer in nutrients. Connection reduced root to shoot ratio in terrestrial ramets, but increased it in aquatic ones, suggesting that physiological integration induced a division of labor in which terrestrial ramets specialized for light acquisition and aquatic ramets specialized for acquisition of nutrients. This provides the first report of increase in clonal performance and induction of division of labor due to physiological integration between ramets in different habitats. Copyright © 2017 Elsevier B.V. All rights reserved.

In vitro cultured primary roots derived from stem segments of cassava (Manihot esculenta) can behave like storage organs.

PubMed

Medina, Ricardo D; Faloci, Mirta M; Gonzalez, Ana M; Mroginski, Luis A

2007-03-01

Cassava (Manihot esculenta) has three adventitious root types: primary and secondary fibrous roots, and storage roots. Different adventitious root types can also regenerate from in vitro cultured segments. The aim of this study was to investigate aspects of in vitro production of storage roots. Morphological and anatomical analyses were performed to identify and differentiate each root type. Twenty-nine clones were assayed to determine the effect of genotype on the capacity to form storage roots in vitro. The effects of cytokinins and auxins on the formation of storage roots in vitro were also examined. Primary roots formed in vitro and in vivo had similar tissue kinds; however, storage roots formed in vitro exhibited physiological specialization for storing starch. The only consistent diagnostic feature between secondary fibrous and storage roots was their functional differentiation. Anatomical analysis of the storage roots formed in vitro showed that radial expansion as a consequence of massive proliferation and enlargement of parenchymatous cells occurred in the middle cortex, but not from cambial activity as in roots formed in vivo. Cortical expansion could be related to dilatation growth favoured by hormone treatments. Starch deposition of storage roots formed in vitro was confined to cortical tissue and occurred earlier than in storage roots formed in vivo. Auxin and cytokinin supplementation were absolutely required for in vitro storage root regeneration; these roots were not able to develop secondary growth, but formed a tissue competent for starch storing. MS medium with 5 % sucrose plus 0.54 microM 1-naphthaleneacetic acid and 0.44 microM 6-benzylaminopurine was one of the most effective in stimulating the storage root formation. Genotypes differed significantly in their capacity to produce storage roots in vitro. Storage root formation was considerably affected by the segment's primary position and strongly influenced by hormone treatments. The storage root formation system reported here is a first approach to develop a tuberization model, and additional efforts are required to improve it. Although it was not possible to achieve root secondary growth, after this work it will be feasible to advance in some aspects of in vitro cassava tuberization.

Form matters: morphological aspects of lateral root development

PubMed Central

Szymanowska-Pułka, Joanna

2013-01-01

Background The crucial role of roots in plant nutrition, and consequently in plant productivity, is a strong motivation to study the growth and functioning of various aspects of the root system. Numerous studies on lateral roots, as a major determinant of the root system architecture, mostly focus on the physiological and molecular bases of developmental processes. Unfortunately, little attention is paid either to the morphological changes accompanying the formation of a lateral root or to morphological defects occurring in lateral root primordia. The latter are observed in some mutants and occasionally in wild-type plants, but may also result from application of external factors. Scope and Conclusions In this review various morphological aspects of lateral branching in roots are analysed. Morphological events occurring during the formation of a typical lateral root are described. This process involves dramatic changes in the geometry of the developing organ that at early stages are associated with oblique cell divisions, leading to breaking of the symmetry of the cell pattern. Several types of defects in the morphology of primordia are indicated and described. Computer simulations show that some of these defects may result from an unstable field of growth rates. Significant changes in both primary and lateral root morphology may also be a consequence of various mutations, some of which are auxin-related. Examples reported in the literature are considered. Finally, lateral root formation is discussed in terms of mechanics. In this approach the primordium is considered as a physical object undergoing deformation and is characterized by specific mechanical properties. PMID:24190952

Nocturnal and daytime stomatal conductance respond to root-zone temperature in ‘Shiraz’ grapevines

PubMed Central

Rogiers, Suzy Y.; Clarke, Simon J.

2013-01-01

Background and Aims Daytime root-zone temperature may be a significant factor regulating water flux through plants. Water flux can also occur during the night but nocturnal stomatal response to environmental drivers such as root-zone temperature remains largely unknown. Methods Here nocturnal and daytime leaf gas exchange was quantified in ‘Shiraz’ grapevines (Vitis vinifera) exposed to three root-zone temperatures from budburst to fruit-set, for a total of 8 weeks in spring. Key Results Despite lower stomatal density, night-time stomatal conductance and transpiration rates were greater for plants grown in warm root-zones. Elevated root-zone temperature resulted in higher daytime stomatal conductance, transpiration and net assimilation rates across a range of leaf-to-air vapour pressure deficits, air temperatures and light levels. Intrinsic water-use efficiency was, however, lowest in those plants with warm root-zones. CO2 response curves of foliar gas exchange indicated that the maximum rate of electron transport and the maximum rate of Rubisco activity did not differ between the root-zone treatments, and therefore it was likely that the lower photosynthesis in cool root-zones was predominantly the result of a stomatal limitation. One week after discontinuation of the temperature treatments, gas exchange was similar between the plants, indicating a reversible physiological response to soil temperature. Conclusions In this anisohydric grapevine variety both night-time and daytime stomatal conductance were responsive to root-zone temperature. Because nocturnal transpiration has implications for overall plant water status, predictive climate change models using stomatal conductance will need to factor in this root-zone variable. PMID:23293018

Analysis of changes in relative elemental growth rate patterns in the elongation zone of Arabidopsis roots upon gravistimulation

NASA Technical Reports Server (NTRS)

Mullen, J. L.; Ishikawa, H.; Evans, M. L.

1998-01-01

Although Arabidopsis is an important system for studying root physiology, the localized growth patterns of its roots have not been well defined, particularly during tropic responses. In order to characterize growth rate profiles along the apex of primary roots of Arabidopsis thaliana (L.) Heynh (ecotype Columbia) we applied small charcoal particles to the root surface and analyzed their displacement during growth using an automated video digitizer system with custom software for tracking the markers. When growing vertically, the maximum elongation rate occurred 481 +/- 50 microns back from the extreme tip of the root (tip of root cap), and the elongation zone extended back to 912 +/- 137 microns. The distal elongation zone (DEZ) has previously been described as the apical region of the elongation zone in which the relative elemental growth rate (REGR) is < or = 30% of the peak rate in the central elongation zone. By this definition, our data indicate that the basal limit of the DEZ was located 248 +/- 30 microns from the root tip. However, after gravistimulation, the growth patterns of the root changed. Within the first hour of graviresponse, the basal limit of the DEZ and the position of peak REGR shifted apically on the upper flank of the root. This was due to a combination of increased growth in the DEZ and growth inhibition in the central elongation zone. On the lower flank, the basal limit of the DEZ shifted basipetally as the REGR decreased. These factors set up the gradient of growth rate across the root, which drives curvature.

Nocturnal and daytime stomatal conductance respond to root-zone temperature in 'Shiraz' grapevines.

PubMed

Rogiers, Suzy Y; Clarke, Simon J

2013-03-01

Daytime root-zone temperature may be a significant factor regulating water flux through plants. Water flux can also occur during the night but nocturnal stomatal response to environmental drivers such as root-zone temperature remains largely unknown. Here nocturnal and daytime leaf gas exchange was quantified in 'Shiraz' grapevines (Vitis vinifera) exposed to three root-zone temperatures from budburst to fruit-set, for a total of 8 weeks in spring. Despite lower stomatal density, night-time stomatal conductance and transpiration rates were greater for plants grown in warm root-zones. Elevated root-zone temperature resulted in higher daytime stomatal conductance, transpiration and net assimilation rates across a range of leaf-to-air vapour pressure deficits, air temperatures and light levels. Intrinsic water-use efficiency was, however, lowest in those plants with warm root-zones. CO(2) response curves of foliar gas exchange indicated that the maximum rate of electron transport and the maximum rate of Rubisco activity did not differ between the root-zone treatments, and therefore it was likely that the lower photosynthesis in cool root-zones was predominantly the result of a stomatal limitation. One week after discontinuation of the temperature treatments, gas exchange was similar between the plants, indicating a reversible physiological response to soil temperature. In this anisohydric grapevine variety both night-time and daytime stomatal conductance were responsive to root-zone temperature. Because nocturnal transpiration has implications for overall plant water status, predictive climate change models using stomatal conductance will need to factor in this root-zone variable.

Microarray Analyses of Gene Expression during Adventitious Root Development in Pinus contorta1[w

PubMed Central

Brinker, Monika; van Zyl, Leonel; Liu, Wenbin; Craig, Deborah; Sederoff, Ronald R.; Clapham, David H.; von Arnold, Sara

2004-01-01

In order to investigate the gene expression pattern during adventitious root development, RNA of Pinus contorta hypocotyls, pulse-treated with the auxin indole-3-butyric acid and harvested at distinct developmental time points of root development, was hybridized to microarrays containing 2,178 cDNAs from Pinus taeda. Over the period of observation of root development, the transcript levels of 220 genes changed significantly. During the root initiation phase, genes involved in cell replication and cell wall weakening and a transcript encoding a PINHEAD/ZWILLE-like protein were up-regulated, while genes related to auxin transport, photosynthesis, and cell wall synthesis were down-regulated. In addition, there were changes in transcript abundance of genes related to water stress. During the root meristem formation phase the transcript abundances of genes involved in auxin transport, auxin responsive transcription, and cell wall synthesis, and of a gene encoding a B-box zinc finger-like protein, increased, while those encoding proteins involved in cell wall weakening decreased. Changes of transcript abundance of genes related to water stress during the root meristem formation and root formation phase indicate that the plant roots had become functional in water transport. Simultaneously, genes involved in auxin transport were up-regulated, while genes related to cell wall modification were down-regulated. Finally, during the root elongation phase down-regulation of transcripts encoding proteins involved in cell replication and stress occurred. Based on the observed changes in transcript abundances, we suggest hypotheses about the relative importance of various physiological processes during the auxin-induced development of roots in P. contorta. PMID:15247392

Understanding the development of roots exposed to contaminants and the potential of plant-associated bacteria for optimization of growth

PubMed Central

Remans, Tony; Thijs, Sofie; Truyens, Sascha; Weyens, Nele; Schellingen, Kerim; Keunen, Els; Gielen, Heidi; Cuypers, Ann; Vangronsveld, Jaco

2012-01-01

Background and Scope Plant responses to the toxic effects of soil contaminants, such as excess metals or organic substances, have been studied mainly at physiological, biochemical and molecular levels, but the influence on root system architecture has received little attention. Nevertheless, the precise position, morphology and extent of roots can influence contaminant uptake. Here, data are discussed that aim to increase the molecular and ecological understanding of the influence of contaminants on root system architecture. Furthermore, the potential of plant-associated bacteria to influence root growth by their growth-promoting and stress-relieving capacities is explored. Methods Root growth parameters of Arabidopsis thaliana seedlings grown in vertical agar plates are quantified. Mutants are used in a reverse genetics approach to identify molecular components underlying quantitative changes in root architecture after exposure to excess cadmium, copper or zinc. Plant-associated bacteria are isolated from contaminated environments, genotypically and phenotypically characterized, and used to test plant root growth improvement in the presence of contaminants. Key Results The molecular determinants of primary root growth inhibition and effects on lateral root density by cadmium were identified. A vertical split-root system revealed local effects of cadmium and copper on root development. However, systemic effects of zinc exposure on root growth reduced both the avoidance of contaminated areas and colonization of non-contaminated areas. The potential for growth promotion and contaminant degradation of plant-associated bacteria was demonstrated by improved root growth of inoculated plants exposed to 2,4-di-nitro-toluene (DNT) or cadmium. Conclusions Knowledge concerning the specific influence of different contaminants on root system architecture and the molecular mechanisms by which this is achieved can be combined with the exploitation of plant-associated bacteria to influence root development and increase plant stress tolerance, which should lead to more optimal root systems for application in phytoremediation or safer biomass production. PMID:22634257

Understanding the development of roots exposed to contaminants and the potential of plant-associated bacteria for optimization of growth.

PubMed

Remans, Tony; Thijs, Sofie; Truyens, Sascha; Weyens, Nele; Schellingen, Kerim; Keunen, Els; Gielen, Heidi; Cuypers, Ann; Vangronsveld, Jaco

2012-07-01

Plant responses to the toxic effects of soil contaminants, such as excess metals or organic substances, have been studied mainly at physiological, biochemical and molecular levels, but the influence on root system architecture has received little attention. Nevertheless, the precise position, morphology and extent of roots can influence contaminant uptake. Here, data are discussed that aim to increase the molecular and ecological understanding of the influence of contaminants on root system architecture. Furthermore, the potential of plant-associated bacteria to influence root growth by their growth-promoting and stress-relieving capacities is explored. Root growth parameters of Arabidopsis thaliana seedlings grown in vertical agar plates are quantified. Mutants are used in a reverse genetics approach to identify molecular components underlying quantitative changes in root architecture after exposure to excess cadmium, copper or zinc. Plant-associated bacteria are isolated from contaminated environments, genotypically and phenotypically characterized, and used to test plant root growth improvement in the presence of contaminants. The molecular determinants of primary root growth inhibition and effects on lateral root density by cadmium were identified. A vertical split-root system revealed local effects of cadmium and copper on root development. However, systemic effects of zinc exposure on root growth reduced both the avoidance of contaminated areas and colonization of non-contaminated areas. The potential for growth promotion and contaminant degradation of plant-associated bacteria was demonstrated by improved root growth of inoculated plants exposed to 2,4-di-nitro-toluene (DNT) or cadmium. Knowledge concerning the specific influence of different contaminants on root system architecture and the molecular mechanisms by which this is achieved can be combined with the exploitation of plant-associated bacteria to influence root development and increase plant stress tolerance, which should lead to more optimal root systems for application in phytoremediation or safer biomass production.

The tomato res mutant which accumulates JA in roots in non-stressed conditions restores cell structure alterations under salinity.

PubMed

Garcia-Abellan, José O; Fernandez-Garcia, Nieves; Lopez-Berenguer, Carmen; Egea, Isabel; Flores, Francisco B; Angosto, Trinidad; Capel, Juan; Lozano, Rafael; Pineda, Benito; Moreno, Vicente; Olmos, Enrique; Bolarin, Maria C

2015-11-01

Jasmonic acid (JA) regulates a wide spectrum of plant biological processes, from plant development to stress defense responses. The role of JA in plant response to salt stress is scarcely known, and even less known is the specific response in root, the main plant organ responsible for ionic uptake and transport to the shoot. Here we report the characterization of the first tomato (Solanum lycopersicum) mutant, named res (restored cell structure by salinity), that accumulates JA in roots prior to exposure to stress. The res tomato mutant presented remarkable growth inhibition and displayed important morphological alterations and cellular disorganization in roots and leaves under control conditions, while these alterations disappeared when the res mutant plants were grown under salt stress. Reciprocal grafting between res and wild type (WT) (tomato cv. Moneymaker) indicated that the main organ responsible for the development of alterations was the root. The JA-signaling pathway is activated in res roots prior to stress, with transcripts levels being even higher in control condition than in salinity. Future studies on this mutant will provide significant advances in the knowledge of JA role in root in salt-stress tolerance response, as well as in the energy trade-off between plant growth and response to stress. © 2015 Scandinavian Plant Physiology Society.

High efficiency transport of quantum dots into plant roots with the aid of silwet L-77.

PubMed

Hu, Yong; Li, Jun; Ma, Lu; Peng, Qionglin; Feng, Wei; Zhang, Lu; He, Shibin; Yang, Fei; Huang, Jing; Li, Lijia

2010-08-01

Quantum dots (QDs) are a novel type of small, photostable and bright fluorophores that have been successfully applied to mammalian and human live cell imaging. In this study, highly dispersive water-soluble mercaptoacetic acid (MAA)-coated CdSe/ZnS QDs were synthesized, which were suitable for investigation as fluorescent probe labels. The treatment of maize seedling roots with QDs showed that the surfactant silwet L-77 aided the efficient transport of QDs into maize roots. Under a concentration ranging from 0.128 to 1.28 microM, QDs caused very low cytotoxicity on maize seed germination and root growth. The addition of mercuric chloride to the Hoagland solution resulted in a decrease of QD content in root tissues, and this decrease was reversed upon the addition of beta-mercaptoethanol, which suggests that mercury-sensitive processes play a significant role in regulating QD flow in the maize root system. We speculate that the apoplastic pathway can contribute substantially to the total quantity of QDs reaching the stele. Therefore, based on this transport approach, MAA-coated QDs can be utilized for live imaging in plant systems to verify known physiological processes. Copyright 2010 Elsevier Masson SAS. All rights reserved.

Representing leaf and root physiological traits in CLM improves global carbon and nitrogen cycling predictions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghimire, Bardan; Riley, William J.; Koven, Charles D.

In many ecosystems, nitrogen is the most limiting nutrient for plant growth and productivity. However, current Earth System Models (ESMs) do not mechanistically represent functional nitrogen allocation for photosynthesis or the linkage between nitrogen uptake and root traits. The current version of CLM (4.5) links nitrogen availability and plant productivity via (1) an instantaneous downregulation of potential photosynthesis rates based on soil mineral nitrogen availability, and (2) apportionment of soil nitrogen between plants and competing nitrogen consumers assumed to be proportional to their relative N demands. However, plants do not photosynthesize at potential rates and then downregulate; instead photosynthesis ratesmore » are governed by nitrogen that has been allocated to the physiological processes underpinning photosynthesis. Furthermore, the role of plant roots in nutrient acquisition has also been largely ignored in ESMs. We therefore present a new plant nitrogen model for CLM4.5 with (1) improved representations of linkages between leaf nitrogen and plant productivity based on observed relationships in a global plant trait database and (2) plant nitrogen uptake based on root-scale Michaelis-Menten uptake kinetics. Our model improvements led to a global bias reduction in GPP, LAI, and biomass of 70%, 11%, and 49%, respectively. Furthermore, water use efficiency predictions were improved conceptually, qualitatively, and in magnitude. The new model's GPP responses to nitrogen deposition, CO 2 fertilization, and climate also differed from the baseline model. The mechanistic representation of leaf-level nitrogen allocation and a theoretically consistent treatment of competition with belowground consumers led to overall improvements in global carbon cycling predictions.« less

Representing leaf and root physiological traits in CLM improves global carbon and nitrogen cycling predictions

DOE PAGES

Ghimire, Bardan; Riley, William J.; Koven, Charles D.; ...

2016-05-01

In many ecosystems, nitrogen is the most limiting nutrient for plant growth and productivity. However, current Earth System Models (ESMs) do not mechanistically represent functional nitrogen allocation for photosynthesis or the linkage between nitrogen uptake and root traits. The current version of CLM (4.5) links nitrogen availability and plant productivity via (1) an instantaneous downregulation of potential photosynthesis rates based on soil mineral nitrogen availability, and (2) apportionment of soil nitrogen between plants and competing nitrogen consumers assumed to be proportional to their relative N demands. However, plants do not photosynthesize at potential rates and then downregulate; instead photosynthesis ratesmore » are governed by nitrogen that has been allocated to the physiological processes underpinning photosynthesis. Furthermore, the role of plant roots in nutrient acquisition has also been largely ignored in ESMs. We therefore present a new plant nitrogen model for CLM4.5 with (1) improved representations of linkages between leaf nitrogen and plant productivity based on observed relationships in a global plant trait database and (2) plant nitrogen uptake based on root-scale Michaelis-Menten uptake kinetics. Our model improvements led to a global bias reduction in GPP, LAI, and biomass of 70%, 11%, and 49%, respectively. Furthermore, water use efficiency predictions were improved conceptually, qualitatively, and in magnitude. The new model's GPP responses to nitrogen deposition, CO 2 fertilization, and climate also differed from the baseline model. The mechanistic representation of leaf-level nitrogen allocation and a theoretically consistent treatment of competition with belowground consumers led to overall improvements in global carbon cycling predictions.« less

Proteomic analysis of injured storage roots in cassava (Manihot esculenta Crantz) under postharvest physiological deterioration

PubMed Central

Qin, Yuling; Djabou, Astride Stéphanie Mouafi; An, Feifei; Li, Kaimian; Li, Zhaogui; Yang, Long; Wang, Xiaojing

2017-01-01

Postharvest physiological deterioration (PPD) is a global challenge in the improvement of cassava value chain. However, how to reduce cassava spoilage and reveal the mechanism of injured cassava storage roots in response to PPD were poorly understood. In the present study, we investigated the activities of antioxidant enzymes of cassava injured storage roots in PPD-susceptible (SC9) and PPD-tolerant (QZ1) genotypes at the time-points from 0h to 120h, and further analyzed their proteomic changes using two-dimensional electrophoresis (2-DE) in combination with MALDI-TOF-MS/MS. Ninety-nine differentially expressed proteins were identified from SC9 and QZ1 genotypes in the pairwise comparison of 24h/0h, 48h/0h, 72h/0h and 96h/0h. Of those proteins were associated with 13 biological functions, in which carbohydrate and energy metabolism related proteins were the biggest amount differential proteins in both genotypes, followed by chaperones, DNA and RNA metabolism, and defense system. We speculated that SOD in combination with CAT activities would be the first line of defense against PPD to support PPD-tolerant cassava varieties. The four hub proteins including CPN60B, LOS2, HSC70-1 and CPN20B, produced from the network of protein-protein interaction, will be the candidate key proteins linked with PPD. This study provides a new clue to improve cassava PPD-tolerant varieties and would be helpful to much better understand the molecular mechanism of PPD of cassava injured storage roots. PMID:28339481

Proteomic analysis of injured storage roots in cassava (Manihot esculenta Crantz) under postharvest physiological deterioration.

PubMed

Qin, Yuling; Djabou, Astride Stéphanie Mouafi; An, Feifei; Li, Kaimian; Li, Zhaogui; Yang, Long; Wang, Xiaojing; Chen, Songbi

2017-01-01

Postharvest physiological deterioration (PPD) is a global challenge in the improvement of cassava value chain. However, how to reduce cassava spoilage and reveal the mechanism of injured cassava storage roots in response to PPD were poorly understood. In the present study, we investigated the activities of antioxidant enzymes of cassava injured storage roots in PPD-susceptible (SC9) and PPD-tolerant (QZ1) genotypes at the time-points from 0h to 120h, and further analyzed their proteomic changes using two-dimensional electrophoresis (2-DE) in combination with MALDI-TOF-MS/MS. Ninety-nine differentially expressed proteins were identified from SC9 and QZ1 genotypes in the pairwise comparison of 24h/0h, 48h/0h, 72h/0h and 96h/0h. Of those proteins were associated with 13 biological functions, in which carbohydrate and energy metabolism related proteins were the biggest amount differential proteins in both genotypes, followed by chaperones, DNA and RNA metabolism, and defense system. We speculated that SOD in combination with CAT activities would be the first line of defense against PPD to support PPD-tolerant cassava varieties. The four hub proteins including CPN60B, LOS2, HSC70-1 and CPN20B, produced from the network of protein-protein interaction, will be the candidate key proteins linked with PPD. This study provides a new clue to improve cassava PPD-tolerant varieties and would be helpful to much better understand the molecular mechanism of PPD of cassava injured storage roots.

A novel root-to-shoot stomatal response to very high CO2 levels in the soil: electrical, hydraulic and biochemical signalling.

PubMed

Lake, Janice A; Walker, Heather J; Cameron, Duncan D; Lomax, Barry H

2017-04-01

Investigations were undertaken in the context of the potential environmental impact of carbon capture and storage (CCS) transportation in the form of a hypothetical leak of extreme levels of CO 2 into the soil environment and subsequent effects on plant physiology. Laboratory studies using purpose built soil chambers, separating and isolating the soil and aerial environments, were used to introduce high levels of CO 2 gas exclusively into the rhizosphere. CO 2 concentrations greater than 32% in the isolated soil environment revealed a previously unknown whole plant stomatal response. Time course measurements of stomatal conductance (g s ), leaf temperature and leaf abscisic acid (ABA) show strong coupling between all three variables over a specific period (3 h following CO 2 gassing) occurring as a result of CO 2 -specific detection by roots. The coupling of g s and ABA subsequently breaks down resulting in a rapid and complete loss of turgor in the shoot. Root access to water is severely restricted as evidenced by the inability to counter turgor loss, however, the plant regains some turgor over time. Recovery of full turgor is not achieved over the longer term. Results suggest an immediate perception and whole plant response as changes in measured parameters (leaf temperature, g s and ABA) occur in the shoot, but the response is solely due to detection of very high CO 2 concentration at the root/soil interface which results in loss of stomatal regulation and disruption to control over water uptake. © 2016 Scandinavian Plant Physiology Society.

Physiological Investigation and Transcriptome Analysis of Polyethylene Glycol (PEG)-Induced Dehydration Stress in Cassava.

PubMed

Fu, Lili; Ding, Zehong; Han, Bingying; Hu, Wei; Li, Yajun; Zhang, Jiaming

2016-02-25

Cassava is an important tropical and sub-tropical root crop that is adapted to drought environment. However, severe drought stress significantly influences biomass accumulation and starchy root production. The mechanism underlying drought-tolerance remains obscure in cassava. In this study, changes of physiological characters and gene transcriptome profiles were investigated under dehydration stress simulated by polyethylene glycol (PEG) treatments. Five traits, including peroxidase (POD) activity, proline content, malondialdehyde (MDA), soluble sugar and soluble protein, were all dramatically induced in response to PEG treatment. RNA-seq analysis revealed a gradient decrease of differentially expressed (DE) gene number in tissues from bottom to top of a plant, suggesting that cassava root has a quicker response and more induced/depressed DE genes than leaves in response to drought. Overall, dynamic changes of gene expression profiles in cassava root and leaves were uncovered: genes related to glycolysis, abscisic acid and ethylene biosynthesis, lipid metabolism, protein degradation, and second metabolism of flavonoids were significantly induced, while genes associated with cell cycle/organization, cell wall synthesis and degradation, DNA synthesis and chromatin structure, protein synthesis, light reaction of photosynthesis, gibberelin pathways and abiotic stress were greatly depressed. Finally, novel pathways in ABA-dependent and ABA-independent regulatory networks underlying PEG-induced dehydration response in cassava were detected, and the RNA-Seq results of a subset of fifteen genes were confirmed by real-time PCR. The findings will improve our understanding of the mechanism related to dehydration stress-tolerance in cassava and will provide useful candidate genes for breeding of cassava varieties better adapted to drought environment.

Physiological Investigation and Transcriptome Analysis of Polyethylene Glycol (PEG)-Induced Dehydration Stress in Cassava

PubMed Central

Fu, Lili; Ding, Zehong; Han, Bingying; Hu, Wei; Li, Yajun; Zhang, Jiaming

2016-01-01

Cassava is an important tropical and sub-tropical root crop that is adapted to drought environment. However, severe drought stress significantly influences biomass accumulation and starchy root production. The mechanism underlying drought-tolerance remains obscure in cassava. In this study, changes of physiological characters and gene transcriptome profiles were investigated under dehydration stress simulated by polyethylene glycol (PEG) treatments. Five traits, including peroxidase (POD) activity, proline content, malondialdehyde (MDA), soluble sugar and soluble protein, were all dramatically induced in response to PEG treatment. RNA-seq analysis revealed a gradient decrease of differentially expressed (DE) gene number in tissues from bottom to top of a plant, suggesting that cassava root has a quicker response and more induced/depressed DE genes than leaves in response to drought. Overall, dynamic changes of gene expression profiles in cassava root and leaves were uncovered: genes related to glycolysis, abscisic acid and ethylene biosynthesis, lipid metabolism, protein degradation, and second metabolism of flavonoids were significantly induced, while genes associated with cell cycle/organization, cell wall synthesis and degradation, DNA synthesis and chromatin structure, protein synthesis, light reaction of photosynthesis, gibberelin pathways and abiotic stress were greatly depressed. Finally, novel pathways in ABA-dependent and ABA-independent regulatory networks underlying PEG-induced dehydration response in cassava were detected, and the RNA-Seq results of a subset of fifteen genes were confirmed by real-time PCR. The findings will improve our understanding of the mechanism related to dehydration stress-tolerance in cassava and will provide useful candidate genes for breeding of cassava varieties better adapted to drought environment. PMID:26927071

Carbon nanomaterials alter plant physiology and soil bacterial community composition in a rice-soil-bacterial ecosystem.

PubMed

Hao, Yi; Ma, Chuanxin; Zhang, Zetian; Song, Youhong; Cao, Weidong; Guo, Jing; Zhou, Guopeng; Rui, Yukui; Liu, Liming; Xing, Baoshan

2018-01-01

The aim of this study was to compare the toxicity effects of carbon nanomaterials (CNMs), namely fullerene (C 60 ), reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs), on a mini-ecosystem of rice grown in a loamy potted soil. We measured plant physiological and biochemical parameters and examined bacterial community composition in the CNMs-treated plant-soil system. After 30 days of exposure, all the three CNMs negatively affected the shoot height and root length of rice, significantly decreased root cortical cells diameter and resulted in shrinkage and deformation of cells, regardless of exposure doses (50 or 500 mg/kg). Additionally, at the high exposure dose of CNM, the concentrations of four phytohormones, including auxin, indoleacetic acid, brassinosteroid and gibberellin acid 4 in rice roots significantly increased as compared to the control. At the high exposure dose of MWCNTs and C 60 , activities of the antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD) in roots increased significantly. High-throughput sequencing showed that three typical CNMs had little effect on shifting the predominant soil bacterial species, but the presence of CNMs significantly altered the composition of the bacterial community. Our results indicate that different CNMs indeed resulted in environmental toxicity to rice and soil bacterial community in the rhizosphere and suggest that CNMs themselves and their incorporated products should be reasonably used to control their release/discharge into the environment to prevent their toxic effects on living organisms and the potential risks to food safety. Copyright © 2017 Elsevier Ltd. All rights reserved.

Representing leaf and root physiological traits in CLM improves global carbon and nitrogen cycling predictions

NASA Astrophysics Data System (ADS)

Ghimire, Bardan; Riley, William J.; Koven, Charles D.; Mu, Mingquan; Randerson, James T.

2016-06-01

In many ecosystems, nitrogen is the most limiting nutrient for plant growth and productivity. However, current Earth System Models (ESMs) do not mechanistically represent functional nitrogen allocation for photosynthesis or the linkage between nitrogen uptake and root traits. The current version of CLM (4.5) links nitrogen availability and plant productivity via (1) an instantaneous downregulation of potential photosynthesis rates based on soil mineral nitrogen availability, and (2) apportionment of soil nitrogen between plants and competing nitrogen consumers assumed to be proportional to their relative N demands. However, plants do not photosynthesize at potential rates and then downregulate; instead photosynthesis rates are governed by nitrogen that has been allocated to the physiological processes underpinning photosynthesis. Furthermore, the role of plant roots in nutrient acquisition has also been largely ignored in ESMs. We therefore present a new plant nitrogen model for CLM4.5 with (1) improved representations of linkages between leaf nitrogen and plant productivity based on observed relationships in a global plant trait database and (2) plant nitrogen uptake based on root-scale Michaelis-Menten uptake kinetics. Our model improvements led to a global bias reduction in GPP, LAI, and biomass of 70%, 11%, and 49%, respectively. Furthermore, water use efficiency predictions were improved conceptually, qualitatively, and in magnitude. The new model's GPP responses to nitrogen deposition, CO2 fertilization, and climate also differed from the baseline model. The mechanistic representation of leaf-level nitrogen allocation and a theoretically consistent treatment of competition with belowground consumers led to overall improvements in global carbon cycling predictions.

Western forest diseases and climate relations: Root diseases and climate change

Treesearch

Mee-Sook Kim; Bryce A. Richardson; Ned B. Klopfenstein

2008-01-01

Climate change could alter patterns of disturbances from pathogens through (1) direct effects on the development, survival, reproduction, dispersal, and distribution of pathogens; (2) physiological changes in tree defenses; (3) indirect effects from changes in the abundance of mutualists and competitors.

Utility of a thermal-based two-source energy balance model for estimating surface fluxes over complex landscapes

USDA-ARS?s Scientific Manuscript database

Many landscapes are comprised of a variety of vegetation types with different canopy structure, rooting depth, physiological characteristics, including response to environmental stressors, etc. Even in agricultural regions, different management practices, including crop rotations, irrigation schedu...

Apple rootstocks: history, physiology, management and breeding

USDA-ARS?s Scientific Manuscript database

For more than two millennia superior fruit tree genotypes have been grafted onto rootstocks to maintain the genetic identity of the desirable scions. Until the 20th century most fruit trees were grafted onto seedling rootstocks. Following the classification, evaluation and propagation of clonal root...

The role of ascorbate peroxidase, guaiacol peroxidase, and polysaccharides in cassava (Manihot esculenta Crantz) roots under postharvest physiological deterioration.

PubMed

Uarrota, Virgílio Gavicho; Moresco, Rodolfo; Schmidt, Eder Carlos; Bouzon, Zenilda Laurita; Nunes, Eduardo da Costa; Neubert, Enilto de Oliveira; Peruch, Luiz Augusto Martins; Rocha, Miguel; Maraschin, Marcelo

2016-04-15

This study aimed to investigate the role of ascorbate peroxidase (APX), guaiacol peroxidase (GPX), polysaccharides, and protein contents associated with the early events of postharvest physiological deterioration (PPD) in cassava roots. Increases in APX and GPX activity, as well as total protein contents occurred from 3 to 5 days of storage and were correlated with the delay of PPD. Cassava samples stained with Periodic Acid-Schiff (PAS) highlighted the presence of starch and cellulose. Degradation of starch granules during PPD was also detected. Slight metachromatic reaction with toluidine blue is indicative of increasing of acidic polysaccharides and may play an important role in PPD delay. Principal component analysis (PCA) classified samples according to their levels of enzymatic activity based on the decision tree model which showed GPX and total protein amounts to be correlated with PPD. The Oriental (ORI) cultivar was more susceptible to PPD. Copyright © 2015 Elsevier Ltd. All rights reserved.

Physiological, cellular and molecular aspects of the desiccation tolerance in Anadenanthera colubrina seeds during germination.

PubMed

Castro, L E; Guimarães, C C; Faria, J M R

2017-11-01

During germination, orthodox seeds become gradually intolerant to desiccation, and for this reason, they are a good model for recalcitrance studies. In the present work, physiological, biochemical, and ultrastructural aspects of the desiccation tolerance were characterized during the germination process of Anadenanthera colubrina seeds. The seeds were imbibed during zero (control), 2, 8, 12 (no germinated seeds), and 18 hours (germinated seeds with 1 mm protruded radicle); then they were dried for 72 hours, rehydrated and evaluated for survivorship. Along the imbibition, cytometric and ultrastructural analysis were performed, besides the extraction of the heat-stable proteins. Posteriorly to imbibition and drying, the evaluation of ultrastructural damages was performed. Desiccation tolerance was fully lost after root protrusion. There was no increase in 4C DNA content after the loss of desiccation tolerance. Ultrastructural characteristics of cells from 1mm roots resembled those found in the recalcitrant seeds, in both hydrated and dehydrated states. The loss of desiccation tolerance coincided with the reduction of heat-stable proteins.

Regulation of Strigolactone Biosynthesis by Gibberellin Signaling.

PubMed

Ito, Shinsaku; Yamagami, Daichi; Umehara, Mikihisa; Hanada, Atsushi; Yoshida, Satoko; Sasaki, Yasuyuki; Yajima, Shunsuke; Kyozuka, Junko; Ueguchi-Tanaka, Miyako; Matsuoka, Makoto; Shirasu, Ken; Yamaguchi, Shinjiro; Asami, Tadao

2017-06-01

Strigolactones (SLs) are a class of plant hormones that regulate diverse physiological processes, including shoot branching and root development. They also act as rhizosphere signaling molecules to stimulate the germination of root parasitic weeds and the branching of arbuscular mycorrhizal fungi. Although various types of cross talk between SLs and other hormones have been reported in physiological analyses, the cross talk between gibberellin (GA) and SLs is poorly understood. We screened for chemicals that regulate the level of SLs in rice ( Oryza sativa ) and identified GA as, to our knowledge, a novel SL-regulating molecule. The regulation of SL biosynthesis by GA is dependent on the GA receptor GID1 and F-box protein GID2. GA treatment also reduced the infection of rice plants by the parasitic plant witchers weed ( Striga hermonthica ). These data not only demonstrate, to our knowledge, the novel plant hormone cross talk between SL and GA, but also suggest that GA can be used to control parasitic weed infections. © 2017 American Society of Plant Biologists. All Rights Reserved.

Regulation of Strigolactone Biosynthesis by Gibberellin Signaling1[OPEN

PubMed Central

Ito, Shinsaku; Yamagami, Daichi; Umehara, Mikihisa; Hanada, Atsushi; Sasaki, Yasuyuki; Yajima, Shunsuke; Kyozuka, Junko; Ueguchi-Tanaka, Miyako; Matsuoka, Makoto; Yamaguchi, Shinjiro

2017-01-01

Strigolactones (SLs) are a class of plant hormones that regulate diverse physiological processes, including shoot branching and root development. They also act as rhizosphere signaling molecules to stimulate the germination of root parasitic weeds and the branching of arbuscular mycorrhizal fungi. Although various types of cross talk between SLs and other hormones have been reported in physiological analyses, the cross talk between gibberellin (GA) and SLs is poorly understood. We screened for chemicals that regulate the level of SLs in rice (Oryza sativa) and identified GA as, to our knowledge, a novel SL-regulating molecule. The regulation of SL biosynthesis by GA is dependent on the GA receptor GID1 and F-box protein GID2. GA treatment also reduced the infection of rice plants by the parasitic plant witchers weed (Striga hermonthica). These data not only demonstrate, to our knowledge, the novel plant hormone cross talk between SL and GA, but also suggest that GA can be used to control parasitic weed infections. PMID:28404726

Partial Root-Zone Drying of Olive (Olea europaea var. 'Chetoui') Induces Reduced Yield under Field Conditions.

PubMed

Dbara, Soumaya; Haworth, Matthew; Emiliani, Giovani; Ben Mimoun, Mehdi; Gómez-Cadenas, Aurelio; Centritto, Mauro

2016-01-01

The productivity of olive trees in arid and semi-arid environments is closely linked to irrigation. It is necessary to improve the efficiency of irrigation techniques to optimise the amount of olive fruit produced in relation to the volume of water used. Partial root-zone drying (PRD) is a water saving irrigation technique that theoretically allows the production of a root-to-shoot signal that modifies the physiology of the above-ground parts of the plant; specifically reducing stomatal conductance (gs) and improving water use efficiency (WUE). Partial root-zone drying has been successfully applied under field conditions to woody and non-woody crops; yet the few previous trials with olive trees have produced contrasting results. Thirty year-old olive trees (Olea europaea 'var. Chetoui') in a Tunisian grove were exposed to four treatments from May to October for three-years: 'control' plants received 100% of the potential evapotranspirative demand (ETc) applied to the whole root-zone; 'PRD100' were supplied with an identical volume of water to the control plants alternated between halves of the root-zone every ten-days; 'PRD50' were given 50% of ETc to half of the root-system, and; 'rain-fed' plants received no supplementary irrigation. Allowing part of the root-zone to dry resulted in reduced vegetative growth and lower yield: PRD100 decreased yield by ~47% during productive years. During the less productive years of the alternate bearing cycle, irrigation had no effect on yield; this suggests that withholding of water during 'off-years' may enhance the effectiveness of irrigation over a two-year cycle. The amount and quality of oil within the olive fruit was unaffected by the irrigation treatment. Photosynthesis declined in the PRD50 and rain-fed trees due to greater diffusive limitations and reduced biochemical uptake of CO2. Stomatal conductance and the foliar concentration of abscisic acid (ABA) were not altered by PRD100 irrigation, which may indicate the absence of a hormonal root-to-shoot signal. Rain-fed and PRD50 treatments induced increased stem water potential and increased foliar concentrations of ABA, proline and soluble sugars. The stomata of the olive trees were relatively insensitive to super-ambient increases in [CO2] and higher [ABA]. These characteristics of 'hydro-passive' stomatal behaviour indicate that the 'Chetoui' variety of olive tree used in this study lacks the physiological responses required for the successful exploitation of PRD techniques to increase yield and water productivity. Alternative irrigation techniques such as partial deficit irrigation may be more suitable for 'Chetoui' olive production.

The Soil-Plant-Atmosphere System - Past and Present.

NASA Astrophysics Data System (ADS)

Berry, J. A.; Baker, I. T.; Randall, D. A.; Sellers, P. J.

2012-12-01

Plants with stomata, roots and a vascular system first appeared on earth about 415 million years ago. This evolutionary innovation helped to set in motion non-linear feedback mechanisms that led to an acceleration of the hydrologic cycle over the continents and an expansion of the climate zones favorable for plant (and animal) life. Skeletal soils that developed long before plants came onto the land would have held water and nutrients in their pore space, yet these resources would have been largely unavailable to primitive, surface-dwelling non-vascular plants due to physical limitations on water transport once the surface layer of soil dries. Plants with roots and a vascular system that could span this dry surface layer could gain increased and prolonged access to the water and nutrients stored in the soil for photosynthesis. Maintenance of the hydraulic connections permitting water to be drawn through the vascular system from deep in the soil to the sites of evaporation in the leaves required a cuticle and physiological regulation of stomata. These anatomical and physiological innovations changed properties of the terrestrial surface (albedo, roughness, a vascular system and control of surface conductance) and set in motion complex interactions of the soil - plant - atmosphere system. We will use coupled physiological and meteorological models to examine some of these interactions.

Physiological gain leads to high ISI variability in a simple model of a cortical regular spiking cell.

PubMed

Troyer, T W; Miller, K D

1997-07-01

To understand the interspike interval (ISI) variability displayed by visual cortical neurons (Softky & Koch, 1993), it is critical to examine the dynamics of their neuronal integration, as well as the variability in their synaptic input current. Most previous models have focused on the latter factor. We match a simple integrate-and-fire model to the experimentally measured integrative properties of cortical regular spiking cells (McCormick, Connors, Lighthall, & Prince, 1985). After setting RC parameters, the post-spike voltage reset is set to match experimental measurements of neuronal gain (obtained from in vitro plots of firing frequency versus injected current). Examination of the resulting model leads to an intuitive picture of neuronal integration that unifies the seemingly contradictory 1/square root of N and random walk pictures that have previously been proposed. When ISIs are dominated by postspike recovery, 1/square root of N arguments hold and spiking is regular; after the "memory" of the last spike becomes negligible, spike threshold crossing is caused by input variance around a steady state and spiking is Poisson. In integrate-and-fire neurons matched to cortical cell physiology, steady-state behavior is predominant, and ISIs are highly variable at all physiological firing rates and for a wide range of inhibitory and excitatory inputs.

Exogenous glutathione improves high root-zone temperature tolerance by modulating photosynthesis, antioxidant and osmolytes systems in cucumber seedlings

PubMed Central

Ding, Xiaotao; Jiang, Yuping; He, Lizhong; Zhou, Qiang; Yu, Jizhu; Hui, Dafeng; Huang, Danfeng

2016-01-01

To investigate the physiological responses of plants to high root-zone temperature (HT, 35 °C) stress mitigated by exogenous glutathione (GSH), cucumber (Cucumis sativus L.) seedlings were exposed to HT with or without GSH treatment for 4 days and following with 4 days of recovery. Plant physiological variables, growth, and gene expression related to antioxidant enzymes and Calvin cycle were quantified. The results showed that HT significantly decreased GSH content, the ratio of reduced to oxidized glutathione (GSH/GSSG), chlorophyll content, photosynthesis and related gene expression, shoot height, stem diameter, as well as dry weight. The exogenous GSH treatment clearly lessened the HT stress by increasing the above variables. Meanwhile, HT significantly increased soluble protein content, proline and malondialdehyde (MDA) content as well as O2•− production rate, the gene expression and activities of antioxidant enzymes. The GSH treatment remarkably improved soluble protein content, proline content, antioxidant enzymes activities, and antioxidant enzymes related gene expression, and reduced the MDA content and O2•− production rate compared to no GSH treatment in the HT condition. Our results suggest that exogenous GSH enhances cucumber seedling tolerance of HT stress by modulating the photosynthesis, antioxidant and osmolytes systems to improve physiological adaptation. PMID:27752105

Physiological and transcriptome response to cadmium in cosmos (Cosmos bipinnatus Cav.) seedlings.

PubMed

Liu, Yujing; Yu, Xiaofang; Feng, Yimei; Zhang, Chao; Wang, Chao; Zeng, Jian; Huang, Zhuo; Kang, Houyang; Fan, Xing; Sha, Lina; Zhang, Haiqin; Zhou, Yonghong; Gao, Suping; Chen, Qibing

2017-10-31

To date, several species of Asteraceae have been considered as Cd-accumulators. However, little information on the Cd tolerance and associated mechanisms of Asteraceae species Cosmos bipinnatus, is known. Presently, several physiological indexes and transcriptome profiling under Cd stress were investigated. C. bipinnatus exhibited strong Cd tolerance and recommended as a Cd-accumulator, although the biomasses were reduced by Cd. Meanwhile, Cd stresses reduced Zn and Ca uptake, but increased Fe uptake. Subcellular distribution indicated that the vacuole sequestration in root mainly detoxified Cd under lower Cd stress. Whilst, cell wall binding and vacuole sequestration in root co-detoxified Cd under high Cd exposure. Meanwhile, 66,407 unigenes were assembled and 41,674 (62.75%) unigenes were annotated in at least one database. 2,658 DEGs including 1,292 up-regulated unigenes and 1,366 down-regulated unigenes were identified under 40 μmol/L Cd stress. Among of these DEGs, ZIPs, HMAs, NRAMPs and ABC transporters might participate in Cd uptake, translocation and accumulation. Many DEGs participating in several processes such as cell wall biosynthesis, GSH metabolism, TCA cycle and antioxidant system probably play critical roles in cell wall binding, vacuole sequestration and detoxification. These results provided a novel insight into the physiological and transcriptome response to Cd in C. bipinnatus seedlings.

Early harvest increases post-harvest physiological quality of Araucaria angustifolia (Araucariaceae) seeds.

PubMed

Shibata, Marília; Medeiros Coelho, Cileide Maria

2016-06-01

Araucaria angustifolia is a conifer native to Brazil and is an endangered species. Since this species seeds have a short period of viability, its vulnerability is higher. Thus the aim of this study was to evaluate the physiological quality of A. angustifolia seeds during the development and post-storage periods. For this, cones of A. angustifolia were collected from a natural population in Curitibanos, Santa Catarina, Brazil, in March, April, May and June 2012. The collected seeds were classified into developmental stages of cotyledonary, I, II and III according to the month of collection; a total of 10 cones were collected for each stage. Seeds were stored in a refrigerator for 60 and 120 days, and were submitted to a chamber germination test (25 °C-photoperiod 12 h). Additionally, seeds were tested for moisture content (105 °C for 24 hours), tetrazolium (0.1 % for 1 hour) and vigor (electric conductivity [75 mL distilled water at 25 °C], germination speed index, and shoot and root length). Our results showed that during seed development, moisture content decreased from the cotyledonary stage (66.54 %) to stage III (49.69 %), and vigor increased in the last stage. During storage, moisture content at cotyledonary stage and stage I was stable. On the other hand, stored seeds exhibited a decrease in moisture content after 120 days at stages II and III. Physiological quality at the cotyledonary stage resulted in an increased germination rate of 86 % and 93 % after 60 and 120 days of storage, respectively; unlike stages II and III exhibited a decrease in seed viability and vigor after storage. Electrical conductivity was higher for fresh seeds at the cotyledonary stage, than for those stored for 60 and 120 days. However, in other stages, released leachate content after 120 days of storage, increased with the advance of the collection period. Germination speed index and shoot and root lengths after storage were highest for seeds at the cotyledonary stage and stage I; unlike stages II and III which had short root and shoot lengths during storage. Thus, the maintenance of seed moisture content during storage was variable and dependent on the period of collection. Furthermore, the physiological quality differed among earlier and later stages. Early collection favored seed physiological quality, and may be a strategy for better conservation of A. angustifolia seeds.

Mild Salt Stress Conditions Induce Different Responses in Root Hydraulic Conductivity of Phaseolus vulgaris Over-Time

PubMed Central

Calvo-Polanco, Monica; Sánchez-Romera, Beatriz; Aroca, Ricardo

2014-01-01

Plants respond to salinity by altering their physiological parameters in order to maintain their water balance. The reduction in root hydraulic conductivity is one of the first responses of plants to the presence of salt in order to minimize water stress. Although its regulation has been commonly attributed to aquaporins activity, osmotic adjustment and the toxic effect of Na+ and Cl− have also a main role in the whole process. We studied the effects of 30 mM NaCl on Phaseolus vulgaris plants after 9 days and found different responses in root hydraulic conductivity over-time. An initial and final reduction of root hydraulic conductivity, stomatal conductance, and leaf water potential in response to NaCl was attributed to an initial osmotic shock after 1 day of treatment, and to the initial symptoms of salt accumulation within the plant tissues after 9 days of treatment. After 6 days of NaCl treatment, the increase in root hydraulic conductivity to the levels of control plants was accompanied by an increase in root fructose content, and with the intracellular localization of root plasma membrane aquaporins (PIP) to cortex cells close to the epidermis and to cells surrounding xylem vessels. Thus, the different responses of bean plants to mild salt stress over time may be connected with root fructose accumulation, and intracellular localization of PIP aquaporins. PMID:24595059

Copper regulates primary root elongation through PIN1-mediated auxin redistribution.

PubMed

Yuan, Hong-Mei; Xu, Heng-Hao; Liu, Wen-Cheng; Lu, Ying-Tang

2013-05-01

The heavy metal copper (Cu) is an essential microelement required for normal plant growth and development, but it inhibits primary root growth when in excess. The mechanism underlying how excess Cu functions in this process remains to be further elucidated. Here, we report that a higher concentration of CuSO4 inhibited primary root elongation of Arabidopsis seedlings by affecting both the elongation and meristem zones. In the meristem zone, meristematic cell division potential was reduced by excess Cu. Further experiments showed that Cu can modulate auxin distribution, resulting in higher auxin activities in both the elongation and meristem zones of Cu-treated roots based on DR5::GUS expression patterns. This Cu-mediated auxin redistribution was shown to be responsible for Cu-mediated inhibition of primary root elongation. Additional genetic and physiological data demonstrated that it was PINFORMED1 (PIN1), but not PIN2 or AUXIN1 (AUX1), that regulated this process. However, Cu-induced hydrogen peroxide accumulation did not contribute to Cu-induced auxin redistribution for inhibition of root elongation. When the possible role of ethylene in this process was analyzed, Cu had a similar impact on the root elongation of both the wild type and the ein2-1 mutant, implying that Cu-mediated inhibition of primary root elongation was not due to the ethylene signaling pathway.

Growth is required for perception of water availability to pattern root branches in plants.

PubMed

Robbins, Neil E; Dinneny, José R

2018-01-23

Water availability is a potent regulator of plant development and induces root branching through a process termed hydropatterning. Hydropatterning enables roots to position lateral branches toward regions of high water availability, such as wet soil or agar media, while preventing their emergence where water is less available, such as in air. The mechanism by which roots perceive the spatial distribution of water during hydropatterning is unknown. Using primary roots of Zea mays (maize) we reveal that developmental competence for hydropatterning is limited to the growth zone of the root tip. Past work has shown that growth generates gradients in water potential across an organ when asymmetries exist in the distribution of available water. Using mathematical modeling, we predict that substantial growth-sustained water potential gradients are also generated in the hydropatterning competent zone and that such biophysical cues inform the patterning of lateral roots. Using diverse chemical and environmental treatments we experimentally demonstrate that growth is necessary for normal hydropatterning of lateral roots. Transcriptomic characterization of the local response of tissues to a moist surface or air revealed extensive regulation of signaling and physiological pathways, some of which we show are growth-dependent. Our work supports a "sense-by-growth" mechanism governing hydropatterning, by which water availability cues are rendered interpretable through growth-sustained water movement. Copyright © 2018 the Author(s). Published by PNAS.

Growth is required for perception of water availability to pattern root branches in plants

PubMed Central

2018-01-01

Water availability is a potent regulator of plant development and induces root branching through a process termed hydropatterning. Hydropatterning enables roots to position lateral branches toward regions of high water availability, such as wet soil or agar media, while preventing their emergence where water is less available, such as in air. The mechanism by which roots perceive the spatial distribution of water during hydropatterning is unknown. Using primary roots of Zea mays (maize) we reveal that developmental competence for hydropatterning is limited to the growth zone of the root tip. Past work has shown that growth generates gradients in water potential across an organ when asymmetries exist in the distribution of available water. Using mathematical modeling, we predict that substantial growth-sustained water potential gradients are also generated in the hydropatterning competent zone and that such biophysical cues inform the patterning of lateral roots. Using diverse chemical and environmental treatments we experimentally demonstrate that growth is necessary for normal hydropatterning of lateral roots. Transcriptomic characterization of the local response of tissues to a moist surface or air revealed extensive regulation of signaling and physiological pathways, some of which we show are growth-dependent. Our work supports a “sense-by-growth” mechanism governing hydropatterning, by which water availability cues are rendered interpretable through growth-sustained water movement. PMID:29317538

Physiological and molecular analysis of the interaction between aluminium toxicity and drought stress in common bean (Phaseolus vulgaris)

PubMed Central

Yang, Zhong-Bao; Eticha, Dejene; Albacete, Alfonso; Rao, Idupulapati Madhusudana; Roitsch, Thomas; Horst, Walter Johannes

2012-01-01

Aluminium (Al) toxicity and drought are two major factors limiting common bean (Phaseolus vulgaris) production in the tropics. Short-term effects of Al toxicity and drought stress on root growth in acid, Al-toxic soil were studied, with special emphasis on Al–drought interaction in the root apex. Root elongation was inhibited by both Al and drought. Combined stresses resulted in a more severe inhibition of root elongation than either stress alone. This result was different from the alleviation of Al toxicity by osmotic stress (–0.60 MPa polyethylene glycol) in hydroponics. However, drought reduced the impact of Al on the root tip, as indicated by the reduction of Al-induced callose formation and MATE expression. Combined Al and drought stress enhanced up-regulation of ACCO expression and synthesis of zeatin riboside, reduced drought-enhanced abscisic acid (ABA) concentration, and expression of NCED involved in ABA biosynthesis and the transcription factors bZIP and MYB, thus affecting the regulation of ABA-dependent genes (SUS, PvLEA18, KS-DHN, and LTP) in root tips. The results provide circumstantial evidence that in soil, drought alleviates Al injury, but Al renders the root apex more drought-sensitive, particularly by impacting the gene regulatory network involved in ABA signal transduction and cross-talk with other phytohormones necessary for maintaining root growth under drought. PMID:22371077

A model framework to represent plant-physiology and rhizosphere processes in soil profile simulation models

NASA Astrophysics Data System (ADS)

Vanderborght, J.; Javaux, M.; Couvreur, V.; Schröder, N.; Huber, K.; Abesha, B.; Schnepf, A.; Vereecken, H.

2013-12-01

Plant roots play a crucial role in several key processes in soils. Besides their impact on biogeochemical cycles and processes, they also have an important influence on physical processes such as water flow and transport of dissolved substances in soils. Interaction between plant roots and soil processes takes place at different scales and ranges from the scale of an individual root and its directly surrounding soil or rhizosphere over the scale of a root system of an individual plant in a soil profile to the scale of vegetation patterns in landscapes. Simulation models that are used to predict water flow and solute transport in soil-plant systems mainly focus on the individual plant root system scale, parameterize single-root scale phenomena, and aggregate the root system scale to the vegetation scale. In this presentation, we will focus on the transition from the single root to the root system scale. Using high resolution non-invasive imaging techniques and methods, gradients in soil properties and states around roots and their difference from the bulk soil properties could be demonstrated. Recent developments in plant sciences provide new insights in the mechanisms that control water fluxes in plants and in the adaptation of root properties or root plasticity to changing soil conditions. However, since currently used approaches to simulate root water uptake neither resolve these small scale processes nor represent processes and controls within the root system, transferring this information to the whole soil-plant system scale is a challenge. Using a simulation model that describes flow and transport processes in the soil, resolves flow and transport towards individual roots, and describes flow and transport within the root system, such a transfer could be achieved. We present a few examples that illustrate: (i) the impact of changed rhizosphere hydraulic properties, (ii) the effect of root hydraulic properties and root system architecture, (iii) the regulation of plant transpiration by root-zone produced plant hormones, and (iv) the impact of salt accumulation at the soil-root interface on root water uptake. We further propose a framework how this process knowledge could be implemented in root zone simulation models that do not resolve small scale processes.

Cadmium alteration of root physiology and potassium ion fluxes.

PubMed

Keck, R W

1978-07-01

Segments of oat (Avena sativa L.) roots which had been exposed to 1 millimolar CdSO(4) in quarter-strength Hoagland No. 1 solution exhibited decreased respiratory rates, ATP levels, membrane-bound ATPase activity, and reduced K(+) fluxes. Respiration and ATP levels were decreased after a 2-hour treatment with 1 millimolar CdSO(4) to 65 and 75%, respectively, of control rates. A membrane-bound, Mg(2+)-dependent, K(+)-stimulated acid ATPase was rapidly inhibited to 12% of control activity in the presence of 1 millimolar CdSO(4). Potassium uptake into root segments was inhibited to 80% of control values after 30 minutes in the presence of CdSO(4). A 2-hour pretreatment of root segments with CdSO(4) inhibited K(+) uptake to 15% of control values. Cytoplasmic K(+) efflux was inhibited with 1 millimolar CdSO(4).The rates and the degree of Cd(2+) inhibition of the parameters listed above suggest that one of the first sites of Cd(2+) action is the plasmalemma K(+) carrier (ATPase) in oat roots.

[Cell surface peroxidase--generator of superoxide anion in wheat root cells under wound stress].

PubMed

Chasov, A V; Gordon, L Kh; Kolesnikov, O P; Minibaeva, F V

2002-01-01

Development of wound stress in excised wheat roots is known to be accompanied with an increase in reactive oxygen species (ROS) production, fall of membrane potential, release of K+ from cells, alkalization of extracellular solution, changes in respiration and metabolism of structural lipids. Dynamics of superoxide release correlates with changes in other physiological parameters, indicating the cross-reaction of these processes. Activity of peroxidase in extracellular solution after a 1 h incubation and removal of roots was shown to be stimulated by the range of organic acids, detergents, metals, and to be inhibited by cyanide. Superoxide production was sensitive to the addition of Mn2+ and H2O2. Increase in superoxide production correlates with the enhancement of peroxidase activity at the application of organic acids and detergents. The results obtained indicate that cell surface peroxidase is one of the main generators of superoxide in wounded wheat root cells. Different ways of stimulation of the ROS producing activity in root cells is supposed. By controlling superoxide and hydrogen peroxide formation, the cell surface peroxidase can control the adaptation processes in stressed plant cells.

Physiological Responses and Gene Co-Expression Network of Mycorrhizal Roots under K+ Deprivation1[OPEN

PubMed Central

Roy, Sushmita

2017-01-01

Arbuscular mycorrhizal (AM) associations enhance the phosphorous and nitrogen nutrition of host plants, but little is known about their role in potassium (K+) nutrition. Medicago truncatula plants were cocultured with the AM fungus Rhizophagus irregularis under high and low K+ regimes for 6 weeks. We determined how K+ deprivation affects plant development and mineral acquisition and how these negative effects are tempered by the AM colonization. The transcriptional response of AM roots under K+ deficiency was analyzed by whole-genome RNA sequencing. K+ deprivation decreased root biomass and external K+ uptake and modulated oxidative stress gene expression in M. truncatula roots. AM colonization induced specific transcriptional responses to K+ deprivation that seem to temper these negative effects. A gene network analysis revealed putative key regulators of these responses. This study confirmed that AM associations provide some tolerance to K+ deprivation to host plants, revealed that AM symbiosis modulates the expression of specific root genes to cope with this nutrient stress, and identified putative regulators participating in these tolerance mechanisms. PMID:28159827

Identification and Validation of Expressed Sequence Tags from Pigeonpea (Cajanus cajan L.) Root

PubMed Central

Kumar, Ravi Ranjan; Yadav, Shailesh; Joshi, Shourabh; Bhandare, Prithviraj P.; Patil, Vinod Kumar; Kulkarni, Pramod B.; Sonkawade, Swati; Naik, G. R.

2014-01-01

Pigeonpea (Cajanus cajan (L) Millsp.) is an important food legume crop of rain fed agriculture in the arid and semiarid tropics of the world. It has deep and extensive root system which serves a number of important physiological and metabolic functions in plant development and growth. In order to identify genes associated with pigeonpea root, ESTs were generated from the root tissues of pigeonpea (GRG-295 genotype) by normalized cDNA library. A total of 105 high quality ESTs were generated by sequencing of 250 random clones which resulted in 72 unigenes comprising 25 contigs and 47 singlets. The ESTs were assigned to 9 functional categories on the basis of their putative function. In order to validate the possible expression of transcripts, four genes, namely, S-adenosylmethionine synthetase, phosphoglycerate kinase, serine carboxypeptidase, and methionine aminopeptidase, were further analyzed by reverse transcriptase PCR. The possible role of the identified transcripts and their functions associated with root will also be a valuable resource for the functional genomics study in legume crop. PMID:24895494

Successful Strategies for Rapidly Upgrading PTC Windchill 9.1 to Windchill 10.1 on a Light Budget

NASA Technical Reports Server (NTRS)

Shearrow, Charles A.

2013-01-01

Topics covered include: The Frugal Times Historical Upgrade Process; Planning for Possible Constraints; PTC Compatibility Matrix; In-Place Upgrade Process; Pre-Upgrade Activities; Upgrade Activities; Post Upgrade Activities; Results of the Upgrade; Tips for an Upgrade On a Shoestring Budget.

Clastogenic and physiological response of chromosomes to nine pesticides in the Vicia faba in vivo root tip assay system.

PubMed

deKergommeaux, D J; Grant, W F; Sandhu, S S

1983-10-01

9 common pesticides were assayed for clastogenic and physiological activity using Vicia faba as a eukaryotic, whole-organism, test system. The compounds tested included the insecticides acephate, demeton, monocrotophos, parathion-methyl, and trichlorfon; the fungicides captan and folpet; and the herbicides bromacil and simazine. The chemicals have been grouped according to relative genotoxicity (strongly positive: demeton, parathion-methyl; positive: folpet, acephate, monocrotophos, captan; weakly positive: bromacil, trichlorfon, simazine). The results were compared with those reported from other assay systems.

Tetraploidy Enhances Boron-Excess Tolerance in Carrizo Citrange (Citrus sinensis L. Osb. × Poncirus trifoliata L. Raf.).

PubMed

Ruiz, Marta; Quiñones, Ana; Martínez-Alcántara, Belén; Aleza, Pablo; Morillon, Raphaël; Navarro, Luis; Primo-Millo, Eduardo; Martínez-Cuenca, Mary-Rus

2016-01-01

Tetraploidy modifies root anatomy which may lead to differentiated capacity to uptake and transport mineral elements. This work provides insights into physiological and molecular characters involved in boron (B) toxicity responses in diploid (2x) and tetraploid (4x) plants of Carrizo citrange (Citrus sinensis L. Osb. × Poncirus trifoliata L. Raf.), a widely used citrus rootstock. With B excess, 2x plants accumulated more B in leaves than 4x plants, which accounted for their higher B uptake and root-to-shoot transport rates. Ploidy did not modify the expression of membrane transporters NIP5 and BOR1 in roots. The cellular allocation of B excess differed between ploidy levels in the soluble fraction, which was lower in 4x leaves, while cell wall-linked B was similar in 2x and 4x genotypes. This correlates with the increased damage and stunted growth recorded in the 2x plants. The 4x roots were found to have fewer root tips, shorter specific root length, longer diameter, thicker exodermis and earlier tissue maturation in root tips, where the Casparian strip was detected at a shorter distance from the root apex than in the 2x roots. The results presented herein suggest that the root anatomical characters of the 4x plants play a key role in their lower B uptake capacity and root-to-shoot transport. Tetraploidy enhances B excess tolerance in citrange CarrizoExpression of NIP5 and BOR1 transporters and cell wall-bounded B are similar between ploidiesB tolerance is attributed to root anatomical modifications induced by genome duplicationThe rootstock 4x citrange carrizo may prevent citrus trees from B excess.

Tetraploidy Enhances Boron-Excess Tolerance in Carrizo Citrange (Citrus sinensis L. Osb. × Poncirus trifoliata L. Raf.)

PubMed Central

Ruiz, Marta; Quiñones, Ana; Martínez-Alcántara, Belén; Aleza, Pablo; Morillon, Raphaël; Navarro, Luis; Primo-Millo, Eduardo; Martínez-Cuenca, Mary-Rus

2016-01-01

Tetraploidy modifies root anatomy which may lead to differentiated capacity to uptake and transport mineral elements. This work provides insights into physiological and molecular characters involved in boron (B) toxicity responses in diploid (2x) and tetraploid (4x) plants of Carrizo citrange (Citrus sinensis L. Osb. × Poncirus trifoliata L. Raf.), a widely used citrus rootstock. With B excess, 2x plants accumulated more B in leaves than 4x plants, which accounted for their higher B uptake and root-to-shoot transport rates. Ploidy did not modify the expression of membrane transporters NIP5 and BOR1 in roots. The cellular allocation of B excess differed between ploidy levels in the soluble fraction, which was lower in 4x leaves, while cell wall-linked B was similar in 2x and 4x genotypes. This correlates with the increased damage and stunted growth recorded in the 2x plants. The 4x roots were found to have fewer root tips, shorter specific root length, longer diameter, thicker exodermis and earlier tissue maturation in root tips, where the Casparian strip was detected at a shorter distance from the root apex than in the 2x roots. The results presented herein suggest that the root anatomical characters of the 4x plants play a key role in their lower B uptake capacity and root-to-shoot transport. Highlights Tetraploidy enhances B excess tolerance in citrange Carrizo Expression of NIP5 and BOR1 transporters and cell wall-bounded B are similar between ploidies B tolerance is attributed to root anatomical modifications induced by genome duplication The rootstock 4x citrange carrizo may prevent citrus trees from B excess. PMID:27252717

The interaction between glucose and cytokinin signaling in controlling Arabidopsis thaliana seedling root growth and development

PubMed Central

Kushwah, Sunita

2017-01-01

ABSTRACT Cytokinin (CK) and glucose (GLC) control several common responses in plants. There is an extensive overlap between CK and GLC signal transduction pathways in Arabidopsis. Physiologically, both GLC and CK could regulate root length in light. CK interacts with GLC via HXK1 dependent pathway for root length control. Wild-type (WT) roots cannot elongate in the GLC free medium while CK-receptor mutant ARABIDOPSIS HISTIDINE KINASE4 (ahk4) and type B ARR triple mutant ARABIDOPSIS RESPONSE REGULATOR1, 10,11 (arr1, 10,11) roots could elongate even in the absence of GLC as compared with the WT. The root hair initiation was also found defective in CK signaling mutants ahk4, arr1,10,11 and arr3,4,5,6,8,9 on increasing GLC concentration (up to 3%); and lesser number of root hairs were visible even at 5% GLC as compared with the WT. Out of 941 BAP regulated genes, 103 (11%) genes were involved in root growth and development. Out of these 103 genes, 60 (58%) genes were also regulated by GLC. GLC could regulate 5736 genes, which include 327 (6%) genes involved in root growth and development. Out of these 327 genes, 60 (18%) genes were also regulated by BAP. Both GLC and CK signaling cannot alter root length in light in auxin signaling mutant AUXIN RESPONSE3/INDOLE-3-ACETIC ACID17 (axr3/iaa17) suggesting that they may involve auxin signaling component as a nodal point. Therefore CK- and GLC- signaling are involved in controlling different aspects of root growth and development such as root length, with auxin signaling components working as downstream target. PMID:28467152

Regulation of root morphogenesis in arbuscular mycorrhizae: what role do fungal exudates, phosphate, sugars and hormones play in lateral root formation?

PubMed Central

Fusconi, Anna

2014-01-01

Background Arbuscular mycorrhizae (AMs) form a widespread root–fungus symbiosis that improves plant phosphate (Pi) acquisition and modifies the physiology and development of host plants. Increased branching is recognized as a general feature of AM roots, and has been interpreted as a means of increasing suitable sites for colonization. Fungal exudates, which are involved in the dialogue between AM fungi and their host during the pre-colonization phase, play a well-documented role in lateral root (LR) formation. In addition, the increased Pi content of AM plants, in relation to Pi-starved controls, as well as changes in the delivery of carbohydrates to the roots and modulation of phytohormone concentration, transport and sensitivity, are probably involved in increasing root system branching. Scope This review discusses the possible causes of increased branching in AM plants. The differential root responses to Pi, sugars and hormones of potential AM host species are also highlighted and discussed in comparison with those of the non-host Arabidopsis thaliana. Conclusions Fungal exudates are probably the main compounds regulating AM root morphogenesis during the first colonization steps, while a complex network of interactions governs root development in established AMs. Colonization and high Pi act synergistically to increase root branching, and sugar transport towards the arbusculated cells may contribute to LR formation. In addition, AM colonization and high Pi generally increase auxin and cytokinin and decrease ethylene and strigolactone levels. With the exception of cytokinins, which seem to regulate mainly the root:shoot biomass ratio, these hormones play a leading role in governing root morphogenesis, with strigolactones and ethylene blocking LR formation in the non-colonized, Pi-starved plants, and auxin inducing them in colonized plants, or in plants grown under high Pi conditions. PMID:24227446

The interaction between glucose and cytokinin signaling in controlling Arabidopsis thaliana seedling root growth and development.

PubMed

Kushwah, Sunita; Laxmi, Ashverya

2017-05-04

Cytokinin (CK) and glucose (GLC) control several common responses in plants. There is an extensive overlap between CK and GLC signal transduction pathways in Arabidopsis. Physiologically, both GLC and CK could regulate root length in light. CK interacts with GLC via HXK1 dependent pathway for root length control. Wild-type (WT) roots cannot elongate in the GLC free medium while CK-receptor mutant ARABIDOPSIS HISTIDINE KINASE4 (ahk4) and type B ARR triple mutant ARABIDOPSIS RESPONSE REGULATOR1, 10,11 (arr1, 10,11) roots could elongate even in the absence of GLC as compared with the WT. The root hair initiation was also found defective in CK signaling mutants ahk4, arr1,10,11 and arr3,4,5,6,8,9 on increasing GLC concentration (up to 3%); and lesser number of root hairs were visible even at 5% GLC as compared with the WT. Out of 941 BAP regulated genes, 103 (11%) genes were involved in root growth and development. Out of these 103 genes, 60 (58%) genes were also regulated by GLC. GLC could regulate 5736 genes, which include 327 (6%) genes involved in root growth and development. Out of these 327 genes, 60 (18%) genes were also regulated by BAP. Both GLC and CK signaling cannot alter root length in light in auxin signaling mutant AUXIN RESPONSE3/INDOLE-3-ACETIC ACID17 (axr3/iaa17) suggesting that they may involve auxin signaling component as a nodal point. Therefore CK- and GLC- signaling are involved in controlling different aspects of root growth and development such as root length, with auxin signaling components working as downstream target.

Root-soil relationships and terroir

NASA Astrophysics Data System (ADS)

Tomasi, Diego

2015-04-01

Soil features, along with climate, are among the most important determinants of a succesful grape production in a certain area. Most of the studies, so far, investigated the above-ground vine response to differente edaphic and climate condition, but it is clearly not sufficient to explain the vine whole behaviour. In fact, roots represent an important part of the terroir system (soil-plant-atmosphere-man), and their study can provide better comprehension of vine responses to different environments. The root density and distribution, the ability of deep-rooting and regenerating new roots are good indicators of root well-being, and represents the basis for an efficient physiological activity of the root system. Root deepening and distribution are strongly dependent and sensitive on soil type and soil properties, while root density is affected mostly by canopy size, rootstock and water availability. According to root well-being, soil management strategies should alleviate soil impediments, improving aeration and microbial activity. Moreover, agronomic practices can impact root system performance and influence the above-ground growth. It is well known, for example, that the root system size is largely diminished by high planting densities. Close vine spacings stimulate a more effective utilization of the available soil, water and nutrients, but if the competition for available soil becomes too high, it can repress vine growth, and compromise vineyard longevity, productivity and reaction to growing season weather. Development of resilient rootstocks, more efficient in terms of water and nutrient uptake and capable of dealing with climate and soil extremes (drought, high salinity) are primary goals fore future research. The use of these rootstocks will benefit a more sustainable use of the soil resources and the preservation and valorisation of the terroir.

Ethylene Inhibits Root Elongation during Alkaline Stress through AUXIN1 and Associated Changes in Auxin Accumulation1

PubMed Central

Li, Juan; Xu, Heng-Hao; Liu, Wen-Cheng; Zhang, Xiao-Wei

2015-01-01

Soil alkalinity causes major reductions in yield and quality of crops worldwide. The plant root is the first organ sensing soil alkalinity, which results in shorter primary roots. However, the mechanism underlying alkaline stress-mediated inhibition of root elongation remains to be further elucidated. Here, we report that alkaline conditions inhibit primary root elongation of Arabidopsis (Arabidopsis thaliana) seedlings by reducing cell division potential in the meristem zones and that ethylene signaling affects this process. The ethylene perception antagonist silver (Ag+) alleviated the inhibition of root elongation by alkaline stress. Moreover, the ethylene signaling mutants ethylene response1-3 (etr1-3), ethylene insensitive2 (ein2), and ein3-1 showed less reduction in root length under alkaline conditions, indicating a reduced sensitivity to alkalinity. Ethylene biosynthesis also was found to play a role in alkaline stress-mediated root inhibition; the ethylene overproducer1-1 mutant, which overproduces ethylene because of increased stability of 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID SYNTHASE5, was hypersensitive to alkaline stress. In addition, the ethylene biosynthesis inhibitor cobalt (Co2+) suppressed alkaline stress-mediated inhibition of root elongation. We further found that alkaline stress caused an increase in auxin levels by promoting expression of auxin biosynthesis-related genes, but the increase in auxin levels was reduced in the roots of the etr1-3 and ein3-1 mutants and in Ag+/Co2+-treated wild-type plants. Additional genetic and physiological data showed that AUXIN1 (AUX1) was involved in alkaline stress-mediated inhibition of root elongation. Taken together, our results reveal that ethylene modulates alkaline stress-mediated inhibition of root growth by increasing auxin accumulation by stimulating the expression of AUX1 and auxin biosynthesis-related genes. PMID:26109425

Molecular genetics of root gravitropism and waving in Arabidopsis thaliana

NASA Technical Reports Server (NTRS)

Sedbrook, J.; Boonsirichai, K.; Chen, R.; Hilson, P.; Pearlman, R.; Rosen, E.; Rutherford, R.; Batiza, A.; Carroll, K.; Schulz, T.;

Tree root dynamics in montane and sub-alpine mixed forest patches.

PubMed

Wang, Y; Kim, J H; Mao, Z; Ramel, M; Pailler, F; Perez, J; Rey, H; Tron, S; Jourdan, C; Stokes, A

2018-02-28

The structure of heterogeneous forests has consequences for their biophysical environment. Variations in the local climate significantly affect tree physiological processes. We hypothesize that forest structure also alters tree root elongation and longevity through temporal and spatial variations in soil temperature and water potential. We installed rhizotrons in paired vegetation communities of closed forest (tree islands) and open patches (canopy gaps), along a soil temperature gradient (elevations of 1400, 1700 and 2000 m) in a heterogeneous mixed forest. We measured the number of growing tree roots, elongation and mortality every month over 4 years. The results showed that the mean daily root elongation rate (RER) was not correlated with soil water potential but was significantly and positively correlated with soil temperature between 0 and 8 °C only. The RER peaked in spring, and a smaller peak was usually observed in the autumn. Root longevity was dependent on altitude and the season in which roots were initiated, and root diameter was a significant factor explaining much of the variability observed. The finest roots usually grew faster and had a higher risk of mortality in gaps than in closed forest. At 2000 m, the finest roots had a higher risk of mortality compared with the lower altitudes. The RER was largely driven by soil temperature and was lower in cold soils. At the treeline, ephemeral fine roots were more numerous, probably in order to compensate for the shorter growing season. Differences in soil climate and root dynamics between gaps and closed forest were marked at 1400 and 1700 m, but not at 2000 m, where canopy cover was more sparse. Therefore, heterogeneous forest structure and situation play a significant role in determining root demography in temperate, montane forests, mostly through impacts on soil temperature.

External hyphae of Rhizophagus irregularis DAOM 197198 are less sensitive to low pH than roots in arbuscular mycorrhizae: evidence from axenic culture system.

PubMed

Wang, Ning; Feng, Zengwei; Zhou, Yang; Zhu, Honghui; Yao, Qing

2017-10-01

The growth of plant roots and arbuscular mycorrhizal fungi (AMF) can be inhibited by low pH; however, it is largely unknown which is more sensitive to low pH. This study aimed to compare the physiological and molecular responses of external hyphae (EH) and roots to low pH in terms of growth, development and functioning. We established AM symbiosis in a two-compartmented system (root compartment, RC; hyphal compartment, HC) using AMF and transformed hairy roots and exposed them to pH 6.5 and/or pH 4.5. The results showed that pH 4.5 significantly decreased root cell viability, while EH at pH 6.5 attenuated the effect. In either RC or HC, pH 4.5 reduced biomass, P content, colonization, ALP activity in roots, and ALP activity and polyphosphate accumulation in EH. GintPT expression in EH was inhibited by pH 4.5 in HC but not in RC. The expression of mycorrhiza-responsive LePTs was significantly reduced by the lower colonization due to decreased pH in either RC or HC, while the expression of non-mycorrhiza-responsive LePTs was not affected. Variation partitioning analysis indicated that EH was less sensitive to low pH than roots. The interactions between roots and EH under low pH stress merit further investigation. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

A meta-analysis of aortic root size in elite athletes.

PubMed

Iskandar, Aline; Thompson, Paul D

2013-02-19

The aorta is exposed to hemodynamic stress during exercise, but whether or not the aorta is larger in athletes is not clear. We performed a systematic literature review and meta-analysis to examine whethere athletes demonstrate increased aortic root dimensions compared with nonathlete controls. We searched MEDLINE and Scopus from inception through August 12, 2012, for English-language studies reporting the aortic root size in elite athletes. Two investigators independently extracted athlete and study characteristics. A multivariate linear mixed model was used to conduct meta-regression analyses. We identified 71 studies reporting aortic root dimensions in 8564 unique athletes, but only 23 of these studies met our criteria by reporting aortic root dimensions at the aortic valve annulus or sinus of Valsalva in elite athletes (n=5580). Athletes were compared directly with controls (n=727) in 13 studies. On meta-regression, the weighted mean aortic root diameter measured at the sinuses of Valsalva was 3.2 mm (P=0.02) larger in athletes than in the nonathletic controls, whereas aortic root size at the aortic valve annulus was 1.6 mm (P=0.04) greater in athletes than in controls. Elite athletes have a small but significantly larger aortic root diameter at the sinuses of Valsalva and aortic valve annulus, but this difference is minor and clinically insignificant. Clinicians evaluating athletes should know that marked aortic root dilatation likely represents a pathological process and not a physiological adaptation to exercise.

Responses to Systemic Nitrogen Signaling in Arabidopsis Roots Involve trans-Zeatin in Shoots.

PubMed

Poitout, Arthur; Crabos, Amandine; Petřík, Ivan; Novák, Ondřej; Krouk, Gabriel; Lacombe, Benoît; Ruffel, Sandrine

2018-05-15

Plants face temporal and spatial variation in nitrogen (N) availability. This includes heterogeneity in soil nitrate (NO3-) content. To overcome these constraints, plants modify their gene expression and physiological processes to optimize N acquisition. This plasticity relies on a complex long-distance root-shoot-root signaling network that remains poorly understood. We previously showed that cytokinin (CK) biosynthesis is required to trigger systemic N signaling. Here, we performed split-root experiments and used a combination of CK-related mutant analyses, hormone profiling, transcriptomic analysis, NO3- uptake assays, and root growth measurements to gain insight into systemic N signaling in Arabidopsis thaliana. By comparing wild-type plants and mutants affected in CK biosynthesis and ABCG14-dependent root-to-shoot translocation of CK, we revealed an important role for active trans-Zeatin (tZ) in systemic N signaling. Both rapid sentinel gene regulation and long-term functional acclimation to heterogeneous NO3- supply, including NO3- transport and root growth regulation, are likely mediated by the integration of tZ content in shoots. Furthermore, shoot transcriptome profiling revealed that glutamate/glutamine metabolism is likely a target of tZ root-to-shoot translocation, prompting an interesting hypothesis regarding shoot-to-root communication. Finally, this study highlights tZ-independent pathways regulating gene expression in shoots as well as NO3- uptake activity in response to total N-deprivation. © 2018 American Society of Plant Biologists. All rights reserved.

Effects of increasing root carbon investment on the mortality and resprouting of Haloxylon ammodendron seedlings under drought.

PubMed

Zhang, Y; Xie, J-B; Li, Y

2017-03-01

Tree mortality induced by drought is one of the most complex processes in ecology. Although two mechanisms associated with water and carbon balance are proposed to explain tree mortality, outstanding problems still exist. Here, in order to test how the root system benefits survival and resprouting of Haloxylon ammodendron seedlings, we examined the various water- and carbon-related physiological indicators (shoot water potential, photosynthesis, dark respiration, hydraulic conductance and non-structural carbohydrates [NSC]) of H. ammodendron seedlings, which were grown in drought and control conditions throughout a grow season in greenhouse. The survival time of the seedling root system (died 70 days after drought) doubled the survival time of the shoot (died at 35 days). Difference in survival time between shoot and root resulted from sustained root respiration supported by increased NSC in roots under drought. Furthermore, investment into the root contributed to resprouting following drought. Based on these results, a death criterion is proposed for this species. The time sequence of major events indicated that drought shifted carbon allocation between shoot and root and altered the flux among different sinks (growth, respiration or storage). The interaction of water and carbon processes determined death or survival of droughted H. ammodendron seedlings. These findings revealed that the 'root protection' strategy is critical in determining survival and resprouting of this species, and provided insights into the effects of carbon and water dynamics on tree mortality. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.

Aluminum tolerance in sorghum and maize

USDA-ARS?s Scientific Manuscript database

The soils of the tropics and subtropics are highly weathered, leading to poor soil fertility and low soil pH. Root growth and function on these acid soils is impaired by aluminium (Al) toxicity, leading to yield instability that jeopardizes food security worldwide. A wealth of physiological evidence...

Characterization of physiological and molecular processes associated with potato response to Zebra chip disease

USDA-ARS?s Scientific Manuscript database

Transcriptional analyses were applied to identify molecular mechanisms associated with the response of leaf and root potato tissues to ‘Ca. Liberibacter solanacearum’ (Lso) infection, causal agent of zebra chip disease (ZC). Lso infection affected several host processes including defense response-, ...

Zostera marina root demography in an intertidal estuarine environment measured using minirhizotron technology

EPA Science Inventory

Over the last four decades there have been major advances in our understanding of the biology, ecology and physiology of seagrasses and their interaction with the environment. Despite these advances, there has been relatively little advancement in our understanding of the belowg...

Effects of Low pH on Photosynthesis, Related Physiological Parameters, and Nutrient Profiles of Citrus

PubMed Central

Long, An; Zhang, Jiang; Yang, Lin-Tong; Ye, Xin; Lai, Ning-Wei; Tan, Ling-Ling; Lin, Dan; Chen, Li-Song

2017-01-01

Seedlings of “Xuegan” (Citrus sinensis) and “Sour pummelo” (Citrus grandis) were irrigated daily with a nutrient solution at a pH of 2.5, 3, 4, 5, or 6 for 9 months. Thereafter, the following responses were investigated: seedling growth; root, stem, and leaf concentrations of nutrient elements; leaf gas exchange, pigment concentration, ribulose-1,5-bisphosphate carboxylase/oxygenase activity and chlorophyll a fluorescence; relative water content, total soluble protein level, H2O2 production and electrolyte leakage in roots and leaves. This was done (a) to determine how low pH affects photosynthesis, related physiological parameters, and mineral nutrient profiles; and (b) to understand the mechanisms by which low pH may cause a decrease in leaf CO2 assimilation. The pH 2.5 greatly inhibited seedling growth, and many physiological parameters were altered only at pH 2.5; pH 3 slightly inhibited seedling growth; pH 4 had almost no influence on seedling growth; and seedling growth and many physiological parameters reached their maximum at pH 5. No seedlings died at any given pH. These results demonstrate that citrus survival is insensitive to low pH. H+-toxicity may directly damage citrus roots, thus affecting the uptake of mineral nutrients and water. H+-toxicity and a decreased uptake of nutrients (i.e., nitrogen, phosphorus, potassium, calcium, and magnesium) and water were likely responsible for the low pH-induced inhibition of growth. Leaf CO2 assimilation was inhibited only at pH 2.5. The combinations of an impaired photosynthetic electron transport chain, increased production of reactive oxygen species, and decreased uptake of nutrients and water might account for the pH 2.5-induced decrease in CO2 assimilation. Mottled bleached leaves only occurred in the pH 2.5-treated C. grandis seedlings. Furthermore, the pH 2.5-induced alterations of leaf CO2 assimilation, water-use efficiency, chlorophylls, polyphasic chlorophyll a fluorescence (OJIP) transients and many fluorescence parameters, root and leaf total soluble proteins, H2O2 production, and electrolyte leakage were all slightly greater in C. grandis than in C. sinensis seedlings. Hence, C. sinensis was slightly more tolerant to low pH than C. grandis. In conclusion, our findings provide novel insight into the causes of low pH-induced inhibition of seedling growth and leaf CO2 assimilation. PMID:28270819

Effects of Low pH on Photosynthesis, Related Physiological Parameters, and Nutrient Profiles of Citrus.

PubMed

Long, An; Zhang, Jiang; Yang, Lin-Tong; Ye, Xin; Lai, Ning-Wei; Tan, Ling-Ling; Lin, Dan; Chen, Li-Song

2017-01-01

Seedlings of "Xuegan" ( Citrus sinensis ) and "Sour pummelo" ( Citrus grandis ) were irrigated daily with a nutrient solution at a pH of 2.5, 3, 4, 5, or 6 for 9 months. Thereafter, the following responses were investigated: seedling growth; root, stem, and leaf concentrations of nutrient elements; leaf gas exchange, pigment concentration, ribulose-1,5-bisphosphate carboxylase/oxygenase activity and chlorophyll a fluorescence; relative water content, total soluble protein level, H 2 O 2 production and electrolyte leakage in roots and leaves. This was done ( a ) to determine how low pH affects photosynthesis, related physiological parameters, and mineral nutrient profiles; and ( b ) to understand the mechanisms by which low pH may cause a decrease in leaf CO 2 assimilation. The pH 2.5 greatly inhibited seedling growth, and many physiological parameters were altered only at pH 2.5; pH 3 slightly inhibited seedling growth; pH 4 had almost no influence on seedling growth; and seedling growth and many physiological parameters reached their maximum at pH 5. No seedlings died at any given pH. These results demonstrate that citrus survival is insensitive to low pH. H + -toxicity may directly damage citrus roots, thus affecting the uptake of mineral nutrients and water. H + -toxicity and a decreased uptake of nutrients (i.e., nitrogen, phosphorus, potassium, calcium, and magnesium) and water were likely responsible for the low pH-induced inhibition of growth. Leaf CO 2 assimilation was inhibited only at pH 2.5. The combinations of an impaired photosynthetic electron transport chain, increased production of reactive oxygen species, and decreased uptake of nutrients and water might account for the pH 2.5-induced decrease in CO 2 assimilation. Mottled bleached leaves only occurred in the pH 2.5-treated C. grandis seedlings. Furthermore, the pH 2.5-induced alterations of leaf CO 2 assimilation, water-use efficiency, chlorophylls, polyphasic chlorophyll a fluorescence (OJIP) transients and many fluorescence parameters, root and leaf total soluble proteins, H 2 O 2 production, and electrolyte leakage were all slightly greater in C. grandis than in C. sinensis seedlings. Hence, C. sinensis was slightly more tolerant to low pH than C. grandis . In conclusion, our findings provide novel insight into the causes of low pH-induced inhibition of seedling growth and leaf CO 2 assimilation.

Comparative Analysis of Arabidopsis Ecotypes Reveals a Role for Brassinosteroids in Root Hydrotropism1[OPEN

PubMed Central

Wang, Meng; Yuan, Wei; Ren, Yan; Li, Ying; Zhang, Na; Kronzucker, Herbert J.

2018-01-01

Plant roots respond to soil moisture gradients and remodel their growth orientation toward water through hydrotropism, a process vital for acclimation to a changing soil environment. Mechanisms underlying the root hydrotropic response, however, remain poorly understood. Here, we examined hydrotropism in 31 Arabidopsis (Arabidopsis thaliana) ecotypes collected from different parts of the world and grown along moisture gradients in a specially designed soil-simulation system. Comparative transcriptome profiling and physiological analyses were carried out on three selected ecotypes, Wassilewskija (Ws), Columbia (Col-0) (strongly hydrotropic), Col-0 (moderately hydrotropic), and C24 (weakly hydrotropic), and in mutant lines with altered root hydrotropic responses. We show that H+ efflux, Ca2+ influx, redox homeostasis, epigenetic regulation, and phytohormone signaling may contribute to root hydrotropism. Among phytohormones, the role of brassinosteroids (BRs) was examined further. In the presence of an inhibitor of BR biosynthesis, the strong hydrotropic response observed in Ws was reduced. The root H+ efflux and primary root elongation also were inhibited when compared with C24, an ecotype that showed a weak hydrotropic response. The BR-insensitive mutant bri1-5 displayed higher rates of root growth inhibition and root curvature on moisture gradients in vertical or oblique orientation when compared with wild-type Ws. We also demonstrate that BRI1 (a BR receptor) interacts with AHA2 (a plasma membrane H+-ATPase) and that their expression patterns are highly coordinated. This synergistic action may contribute to the strong hydrotropism observed in Ws. Our results suggest that BR-associated H+ efflux is critical in the hydrotropic response of Arabidopsis roots. PMID:29439211

Plant Growth Environments with Programmable Relative Humidity and Homogeneous Nutrient Availability

PubMed Central

Lind, Kara R.; Lee, Nigel; Sizmur, Tom; Siemianowski, Oskar; Van Bruggen, Shawn; Ganapathysubramaniam, Baskar

2016-01-01

We describe the design, characterization, and use of “programmable”, sterile growth environments for individual (or small sets of) plants. The specific relative humidities and nutrient availability experienced by the plant is established (RH between 15% and 95%; nutrient concentration as desired) during the setup of the growth environment, which takes about 5 minutes and <1$ in disposable cost. These systems maintain these environmental parameters constant for at least 14 days with minimal intervention (one minute every two days). The design is composed entirely of off-the-shelf components (e.g., LEGO® bricks) and is characterized by (i) a separation of root and shoot environment (which is physiologically relevant and facilitates imposing specific conditions on the root system, e.g., darkness), (ii) the development of the root system on a flat surface, where the root enjoys constant contact with nutrient solution and air, (iii) a compatibility with root phenotyping. We demonstrate phenotyping by characterizing root systems of Brassica rapa plants growing in different relative humidities (55%, 75%, and 95%). While most phenotypes were found to be sensitive to these environmental changes, a phenotype tightly associated with root system topology–the size distribution of the areas encircled by roots–appeared to be remarkably and counterintuitively insensitive to humidity changes. These setups combine many of the advantages of hydroponics conditions (e.g., root phenotyping, complete control over nutrient composition, scalability) and soil conditions (e.g., aeration of roots, shading of roots), while being comparable in cost and setup time to Magenta® boxes. PMID:27304431

Oral Insulin Delivery in a Physiologic Context: Review

PubMed Central

Arbit, Ehud; Kidron, Miriam

2017-01-01

Insulin remains indispensable to the treatment of diabetes, but its availability in injectable form only has hampered its timely and broader use. The development of an oral insulin remains an ultimate goal to both enhance ease of use, and to provide therapeutic advantages rooted in its direct delivery to the portal vein and liver. By mimicking the physiological path taken by pancreatic insulin, oral insulin is expected to have a distinct effect on the hepatic aspect of carbohydrate metabolism, hepatic insulin resistance, and, at the same time, avoid hyperinsulinemia and minimize the risk of hypoglycemia. With oral insulin approaching late stages of development, the goal of this review is to examine oral insulin in a physiological context and report on recent progress in its development. PMID:28654313

Seasonal changes in morphophysiological traits of two native Patagonian shrubs from Argentina with different drought resistance strategies.

PubMed

Varela, M Celeste; Reinoso, Herminda; Luna, Virginia; Cenzano, Ana M

2018-06-01

In semi-arid regions, plants develop various biochemical and physiological strategies to adapt to dry periods. Understanding the resistance mechanisms to dry periods under field conditions is an important topic in ecology. Larrea divaricata and Lycium chilense provide various ecological services. The aim of this work is to elucidate new morpho-histological, biochemical and hormonal traits that contribute to the drought resistance strategies of two native shrubs. Green leaves and fine roots from L. divaricata and L. chilense were collected in each season for one year, and various traits were measured. The hormone (abscisic acid, ABA-glucose ester, gibberellins A 1 and A 3 , and indole acetic acid) contents were determined by liquid chromatography coupled to mass spectrometry. Rainfall data and the soil water content were also measured. A multivariate analysis showed that green leaves from L. divaricata showed high values for the leaf dry weight, blade leaf thickness and ABA content in the summer compared with those from L. chilense. Fine roots from L. divaricata had high RWC and high IAA levels during the autumn-dry period compared with those from L. chilense, but both had similar levels during the winter and spring. Our results support the notion that species with different drought resistance mechanisms (avoidance or tolerance) display different responses to dry periods throughout the year. Larrea divaricata, which exhibits more xerophytic traits, modified its morphology and maintained its physiological parameters (high RWC in leaves and roots, high ABA levels in leaves during summer, high GA 3 in leaves and high IAA in roots during autumn) to tolerate dry periods, whereas Lycium chilense, which displays more mesophytic traits, uses strategies to avoid dry periods (loss of leaves during autumn and winter, high RWC in leaves, high ABA-GE and GA 3 in leaves during summer, high GA 1 and GA 3 in roots during summer, and high IAA in roots during autumn and summer) and thus has a metabolism that is more dependent on water availability for growth. Copyright © 2018. Published by Elsevier Masson SAS.

A test of the hydraulic vulnerability segmentation hypothesis in angiosperm and conifer tree species

DOE PAGES

Johnson, Daniel M.; Wortemann, Remi; McCulloh, Katherine A.; ...

2016-05-04

Water transport from soils to the atmosphere is critical for plant growth and survival. However, we have a limited understanding about many portions of the whole-tree hydraulic pathway, because the vast majority of published information is on terminal branches. Our understanding of mature tree trunk hydraulic physiology, in particular, is limited. The hydraulic vulnerability segmentation hypothesis (HVSH) stipulates that distal portions of the plant (leaves, branches and roots) should be more vulnerable to embolism than trunks, which are non-redundant organs that require a massive carbon investment. In the current study, we compared vulnerability to loss of hydraulic function, leaf andmore » xylem water potentials and the resulting hydraulic safety margins (in relation to the water potential causing 50% loss of hydraulic conductivity) in leaves, branches, trunks and roots of four angiosperms and four conifer tree species. Across all species, our results supported strongly the HVSH as leaves and roots were less resistant to embolism than branches or trunks. However, branches were consistently more resistant to embolism than any other portion of the plant, including trunks. Also, calculated whole-tree vulnerability to hydraulic dysfunction was much greater than vulnerability in branches. This was due to hydraulic dysfunction in roots and leaves at less negative water potentials than those causing branch or trunk dysfunction. Leaves and roots had narrow or negative hydraulic safety margins, but trunks and branches maintained positive safety margins. By using branch-based hydraulic information as a proxy for entire plants, much research has potentially overestimated embolism resistance, and possibly drought tolerance, for many species. This study highlights the necessity to reconsider past conclusions made about plant resistance to drought based on branch xylem only. As a result, this study also highlights the necessity for more research of whole-plant hydraulic physiology to better understand strategies of plant drought tolerance and the critical control points within the hydraulic pathway.« less

A test of the hydraulic vulnerability segmentation hypothesis in angiosperm and conifer tree species

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Daniel M.; Wortemann, Remi; McCulloh, Katherine A.

Water transport from soils to the atmosphere is critical for plant growth and survival. However, we have a limited understanding about many portions of the whole-tree hydraulic pathway, because the vast majority of published information is on terminal branches. Our understanding of mature tree trunk hydraulic physiology, in particular, is limited. The hydraulic vulnerability segmentation hypothesis (HVSH) stipulates that distal portions of the plant (leaves, branches and roots) should be more vulnerable to embolism than trunks, which are non-redundant organs that require a massive carbon investment. In the current study, we compared vulnerability to loss of hydraulic function, leaf andmore » xylem water potentials and the resulting hydraulic safety margins (in relation to the water potential causing 50% loss of hydraulic conductivity) in leaves, branches, trunks and roots of four angiosperms and four conifer tree species. Across all species, our results supported strongly the HVSH as leaves and roots were less resistant to embolism than branches or trunks. However, branches were consistently more resistant to embolism than any other portion of the plant, including trunks. Also, calculated whole-tree vulnerability to hydraulic dysfunction was much greater than vulnerability in branches. This was due to hydraulic dysfunction in roots and leaves at less negative water potentials than those causing branch or trunk dysfunction. Leaves and roots had narrow or negative hydraulic safety margins, but trunks and branches maintained positive safety margins. By using branch-based hydraulic information as a proxy for entire plants, much research has potentially overestimated embolism resistance, and possibly drought tolerance, for many species. This study highlights the necessity to reconsider past conclusions made about plant resistance to drought based on branch xylem only. As a result, this study also highlights the necessity for more research of whole-plant hydraulic physiology to better understand strategies of plant drought tolerance and the critical control points within the hydraulic pathway.« less

Contributions of two cytosolic glutamine synthetase isozymes to ammonium assimilation in Arabidopsis roots

PubMed Central

Konishi, Noriyuki; Ishiyama, Keiki; Beier, Marcel Pascal; Inoue, Eri; Kanno, Keiichi; Yamaya, Tomoyuki; Takahashi, Hideki

2017-01-01

Abstract Glutamine synthetase (GS) catalyzes a reaction that incorporates ammonium into glutamate and yields glutamine in the cytosol and chloroplasts. Although the enzymatic characteristics of the GS1 isozymes are well known, their physiological functions in ammonium assimilation and regulation in roots remain unclear. In this study we show evidence that two cytosolic GS1 isozymes (GLN1;2 and GLN1;3) contribute to ammonium assimilation in Arabidopsis roots. Arabidopsis T-DNA insertion lines for GLN1;2 and GLN1;3 (i.e. gln1;2 and gln1;3 single-mutants), the gln1;2:gln1;3 double-mutant, and the wild-type accession (Col-0) were grown in hydroponic culture with variable concentrations of ammonium to compare their growth, and their content of nitrogen, carbon, ammonium, and amino acids. GLN1;2 and GLN1;3 promoter-dependent green fluorescent protein was observed under conditions with or without ammonium supply. Loss of GLN1;2 caused significant suppression of plant growth and glutamine biosynthesis under ammonium-replete conditions. In contrast, loss of GLN1;3 caused slight defects in growth and Gln biosynthesis that were only visible based on a comparison of the gln1;2 single- and gln1;2:gln1;3 double-mutants. GLN1;2, being the most abundantly expressed GS1 isozyme, markedly increased following ammonium supply and its promoter activity was localized at the cortex and epidermis, while GLN1;3 showed only low expression at the pericycle, suggesting their different physiological contributions to ammonium assimilation in roots. The GLN1;2 promoter-deletion analysis identified regulatory sequences required for controlling ammonium-responsive gene expression of GLN1;2 in Arabidopsis roots. These results shed light on GLN1 isozyme-specific regulatory mechanisms in Arabidopsis that allow adaptation to an ammonium-replete environment. PMID:28007952

Immunolocalization of IAA and ABA in roots and needles of radiata pine (Pinus radiata) during drought and rewatering.

PubMed

De Diego, N; Rodríguez, J L; Dodd, I C; Pérez-Alfocea, F; Moncaleán, P; Lacuesta, M

2013-05-01

Anatomical, physiological and phytohormonal changes involved in drought tolerance were examined in different Pinus radiata D. Don breeds subjected to soil drying and rewatering. Breeds with the smallest stomatal chamber size had the lowest transpiration rate and the highest intrinsic water-use efficiency. Xylem cell size was positively correlated with leaf hydraulic conductance and needle indole-3-acetic acid (IAA) concentrations, whereas transpiration rate was negatively correlated with needle abscisic acid (ABA) levels. Since these two phytohormones seem important in regulating the P. radiata drought response, they were simultaneously immunolocalized in roots and needles of the most tolerant breed (P. radiata var. radiata × var. cedrosensis) during two sequential drought cycles and after rewatering. During drought, IAA was unequally distributed into the pointed area of the needle cross-section and mainly located in mesophyll and vascular tissue cells of needles, possibly inducing needle epinasty, whereas ABA was principally located in guard cells, presumably to elicit stomata closure. In the roots, at the end of the first drought cycle, while strong IAA accumulation was observed in the cortex, ABA levels decreased probably due to translocation to the leaves. Rewatering modified the distribution of both IAA and ABA in the needles, causing an accumulation principally in vascular tissue, with residual concentrations in mesophyll, likely favouring the acclimatization of the plants for further drought cycles. Contrarily, in the roots IAA and ABA were located in the exodermis, a natural barrier that regulates the phytohormone translocation to other plant tissues and hormone losses to the soil solution after rewatering. These results confirm that immunolocalization is an efficient tool to understand the translocation of IAA and ABA in plants subjected to different water stress situations, and clarify their role in regulating physiological responses such as stomata closure and epinasty in needles and root development.

Cortex proliferation in the root is a protective mechanism against abiotic stress.

PubMed

Cui, Hongchang

2015-01-01

Although as an organ the root plays a pivotal role in nutrient and water uptake as well anchorage, individual cell types function distinctly. Cortex is regarded as the least differentiated cell type in the root, but little is known about its role in plant growth and physiology. In recent studies, we found that cortex proliferation can be induced by oxidative stress. Since all types of abiotic stress lead to oxidative stress, this finding suggests a role for cortex in coping with abiotic stress. This hypothesis was tested in this study using the spy mutant, which has an extra layer of cortex in the root. Interestingly, the spy mutant was shown to be hypersensitive to salt and oxidizing reagent applied to the leaves, but it was as tolerant as the wild type to these compounds in the soil. This result lends support to the notion that cortex has a protective role against abiotic stress arising from the soil.

Randomly amplified polymorphic-DNA analysis for detecting genotoxic effects of Boron on maize (Zea mays L.).

PubMed

Sakcali, M Serdal; Kekec, Guzin; Uzonur, Irem; Alpsoy, Lokman; Tombuloglu, Huseyin

2015-08-01

This study was carried out to investigate the genotoxic effect of boron (B) on maize using randomly amplified polymorphic DNA (RAPD) method. Experimental design was conducted under 0, 5, 10, 25, 50, 100, 125, and 150 ppm B exposures, and physiological changes have revealed a sharp decrease in root growth rates from 28% to 85%, starting from 25 ppm to 150 ppm, respectively. RAPD-polymerase chain reaction (PCR) analysis shows that DNA alterations are clearly observed from beginning to 100 ppm. B-induced inhibition in root growth had a positive correlation with DNA alterations. Total soluble protein, root and stem lengths, and B content analysis in root and leaves encourage these results as a consequence. These preliminary findings reveal that B causes chromosomal aberration and genotoxic effects on maize. Meanwhile, usage of RAPD-PCR technique is a suitable biomarker to detect genotoxic effect of B on maize and other crops for the future. © The Author(s) 2013.

The use of stored carbon reserves in growth of temperate tree roots and leaf buds: Analyses using radiocarbon measurements and modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaudinski, J.B.; Torn, M.S.; Riley, W.J.

2009-02-01

Characterizing the use of carbon (C) reserves in trees is important for understanding regional and global C cycles, stress responses, asynchrony between photosynthetic activity and growth demand, and isotopic exchanges in studies of tree physiology and ecosystem C cycling. Using an inadvertent, whole-ecosystem radiocarbon ({sup 14}C) release in a temperate deciduous oak forest and numerical modeling, we estimated that the mean age of stored C used to grow both leaf buds and new roots is 0.7 years and about 55% of new-root growth annually comes from stored C. Therefore, the calculated mean age of C used to grow new-root tissuemore » is {approx}0.4 years. In short, new roots contain a lot of stored C but it is young in age. Additionally, the type of structure used to model stored C input is important. Model structures that did not include storage, or that assumed stored and new C mixed well (within root or shoot tissues) before being used for root growth, did not fit the data nearly as well as when a distinct storage pool was used. Consistent with these whole-ecosystem labeling results, the mean age of C in new-root tissues determined using 'bomb-{sup 14}C' in three additional forest sites in North America and Europe (one deciduous, two coniferous) was less than 1-2 years. The effect of stored reserves on estimated ages of fine roots is unlikely to be large in most natural abundance isotope studies. However, models of root C dynamics should take stored reserves into account, particularly for pulse-labeling studies and fast-cycling roots (<1 years).« less

Root–root interactions: extending our perspective to be more inclusive of the range of theories in ecology and agriculture using in-vivo analyses

PubMed Central

Faget, Marc; Nagel, Kerstin A.; Walter, Achim; Herrera, Juan M.; Jahnke, Siegfried; Schurr, Ulrich; Temperton, Vicky M.

2013-01-01

Background There is a large body of literature on competitive interactions among plants, but many studies have only focused on above-ground interactions and little is known about root–root dynamics between interacting plants. The perspective on possible mechanisms that explain the outcome of root–root interactions has recently been extended to include non-resource-driven mechanisms (as well as resource-driven mechanisms) of root competition and positive interactions such as facilitation. These approaches have often suffered from being static, partly due to the lack of appropriate methodologies for in-situ non-destructive root characterization. Scope Recent studies show that interactive effects of plant neighbourhood interactions follow non-linear and non-additive paths that are hard to explain. Common outcomes such as accumulation of roots mainly in the topsoil cannot be explained solely by competition theory but require a more inclusive theoretical, as well as an improved methodological framework. This will include the question of whether we can apply the same conceptual framework to crop versus natural species. Conclusions The development of non-invasive methods to dynamically study root–root interactions in vivo will provide the necessary tools to study a more inclusive conceptual framework for root–root interactions. By following the dynamics of root–root interactions through time in a whole range of scenarios and systems, using a wide variety of non-invasive methods, (such as fluorescent protein which now allows us to separately identify the roots of several individuals within soil), we will be much better equipped to answer some of the key questions in root physiology, ecology and agronomy. PMID:23378521

Physiological integration enhanced the tolerance of Cynodon dactylon to flooding.

PubMed

Li, Z J; Fan, D Y; Chen, F Q; Yuan, Q Y; Chow, W S; Xie, Z Q

2015-03-01

Many flooding-tolerant species are clonal plants; however, the effects of physiological integration on plant responses to flooding have received limited attention. We hypothesise that flooding can trigger changes in metabolism of carbohydrates and ROS (reactive oxygen species) in clonal plants, and that physiological integration can ameliorate the adverse effects of stress, subsequently restoring the growth of flooded ramets. In the present study, we conducted a factorial experiment combining flooding to apical ramets and stolon severing (preventing physiological integration) between apical and basal ramets of Cynodon dactylon, which is a stoloniferous perennial grass with considerable flooding tolerance. Flooding-induced responses including decreased root biomass, accumulation of soluble sugar and starch, as well as increased activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX) in apical ramets. Physiological integration relieved growth inhibition, carbohydrate accumulation and induction of antioxidant enzyme activity in stressed ramets, as expected, without any observable cost in unstressed ramets. We speculate that relief of flooding stress in clonal plants may rely on oxidising power and electron acceptors transferred between ramets through physiological integration. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.

DESIGN FOR THINKING, A FIRST BOOK IN SEMANTICS.

ERIC Educational Resources Information Center

UPTON, ALBERT

THIS BOOK ABOUT THE FUNCTIONS OF LANGUAGE IN HUMAN LIFE EMPHASIZES LEARNING HOW TO CLASSIFY, DEFINE, AND ANALYZE. FOLLOWING AN EXPLANATION OF THE PHYSIOLOGICAL AND PSYCHOLOGICAL ROOTS OF LANGUAGE, CHAPTERS ON ANALYSIS, MEANING, SIGNS, AMBIGUITY, SEMANTIC GROWTH, AND METAPHOR LEAD TO A DESCRIPTION OF THE COMMUNICATIVE FUNCTION OF LANGUAGE,…

Impact of arbuscular mycorrhizal fungi on maize physiology and biochemical response under variable nitrogen levels

USDA-ARS?s Scientific Manuscript database

Arbuscular mycorrhizal (AM) fungi are known for colonizing plant roots, transporting water and nutrients from the soil to the plant. Therefore, environmental conditions set mainly by soil water and nutrient levels are important determinants of AM function and host plant response. Mechanisms of nitro...

Regulation of Iron Acquisition Responses in Plant Roots by a Transcription Factor

ERIC Educational Resources Information Center

Bauer, Petra

2016-01-01

The presented research hypothesis-driven laboratory exercise teaches advanced undergraduate students state of the art methods and thinking in an integrated molecular physiology context. Students understand the theoretical background of iron acquisition in the model plant "Arabidopsis thaliana." They design a flowchart summarizing the key…

S-nitrosoglutathione spraying improves stomatal conductance, Rubisco activity and antioxidant defense in both leaves and roots of sugarcane plants under water deficit.

PubMed

Silveira, Neidiquele M; Marcos, Fernanda C C; Frungillo, Lucas; Moura, Bárbara B; Seabra, Amedea B; Salgado, Ione; Machado, Eduardo C; Hancock, John T; Ribeiro, Rafael V

2017-08-01

Water deficit is a major environmental constraint on crop productivity and performance and nitric oxide (NO) is an important signaling molecule associated with many biochemical and physiological processes in plants under stressful conditions. This study aims to test the hypothesis that leaf spraying of S-nitrosoglutathione (GSNO), an NO donor, improves the antioxidant defense in both roots and leaves of sugarcane plants under water deficit, with positive consequences for photosynthesis. In addition, the roles of key photosynthetic enzymes ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC) in maintaining CO 2 assimilation of GSNO-sprayed plants under water deficit were evaluated. Sugarcane plants were sprayed with water or GSNO 100 μM and subjected to water deficit, by adding polyethylene glycol (PEG-8000) to the nutrient solution. Sugarcane plants supplied with GSNO presented increases in the activity of antioxidant enzymes such as superoxide dismutase in leaves and catalase in roots, indicating higher antioxidant capacity under water deficit. Such adjustments induced by GSNO were sufficient to prevent oxidative damage in both organs and were associated with better leaf water status. As a consequence, GSNO spraying alleviated the negative impact of water deficit on stomatal conductance and photosynthetic rates, with plants also showing increases in Rubisco activity under water deficit. © 2017 Scandinavian Plant Physiology Society.

Cowpea (Vigna unguiculata L. Walp.) Metabolomics: Osmoprotection as a Physiological Strategy for Drought Stress Resistance and Improved Yield.

PubMed

Goufo, Piebiep; Moutinho-Pereira, José M; Jorge, Tiago F; Correia, Carlos M; Oliveira, Manuela R; Rosa, Eduardo A S; António, Carla; Trindade, Henrique

2017-01-01

Plants usually tolerate drought by producing organic solutes, which can either act as compatible osmolytes for maintaining turgor, or radical scavengers for protecting cellular functions. However, these two properties of organic solutes are often indistinguishable during stress progression. This study looked at individualizing properties of osmotic adjustment vs. osmoprotection in plants, using cowpea as the model species. Two cultivars were grown in well-watered soil, drought conditions, or drought followed by rewatering through fruit formation. Osmoadaptation was investigated in leaves and roots using photosynthetic traits, water homoeostasis, inorganic ions, and primary and secondary metabolites. Multifactorial analyses indicated allocation of high quantities of amino acids, sugars, and proanthocyanidins into roots, presumably linked to their role in growth and initial stress perception. Physiological and metabolic changes developed in parallel and drought/recovery responses showed a progressive acclimation of the cowpea plant to stress. Of the 88 metabolites studied, proline, galactinol, and a quercetin derivative responded the most to drought as highlighted by multivariate analyses, and their correlations with yield indicated beneficial effects. These metabolites accumulated differently in roots, but similarly in leaves, suggesting a more conservative strategy to cope with drought in the aerial parts. Changes in these compounds roughly reflected energy investment in protective mechanisms, although the ability of plants to adjust osmotically through inorganic ions uptake could not be discounted.

Cowpea (Vigna unguiculata L. Walp.) Metabolomics: Osmoprotection as a Physiological Strategy for Drought Stress Resistance and Improved Yield

PubMed Central

Goufo, Piebiep; Moutinho-Pereira, José M.; Jorge, Tiago F.; Correia, Carlos M.; Oliveira, Manuela R.; Rosa, Eduardo A. S.; António, Carla; Trindade, Henrique

2017-01-01

Plants usually tolerate drought by producing organic solutes, which can either act as compatible osmolytes for maintaining turgor, or radical scavengers for protecting cellular functions. However, these two properties of organic solutes are often indistinguishable during stress progression. This study looked at individualizing properties of osmotic adjustment vs. osmoprotection in plants, using cowpea as the model species. Two cultivars were grown in well-watered soil, drought conditions, or drought followed by rewatering through fruit formation. Osmoadaptation was investigated in leaves and roots using photosynthetic traits, water homoeostasis, inorganic ions, and primary and secondary metabolites. Multifactorial analyses indicated allocation of high quantities of amino acids, sugars, and proanthocyanidins into roots, presumably linked to their role in growth and initial stress perception. Physiological and metabolic changes developed in parallel and drought/recovery responses showed a progressive acclimation of the cowpea plant to stress. Of the 88 metabolites studied, proline, galactinol, and a quercetin derivative responded the most to drought as highlighted by multivariate analyses, and their correlations with yield indicated beneficial effects. These metabolites accumulated differently in roots, but similarly in leaves, suggesting a more conservative strategy to cope with drought in the aerial parts. Changes in these compounds roughly reflected energy investment in protective mechanisms, although the ability of plants to adjust osmotically through inorganic ions uptake could not be discounted. PMID:28473840

Use of NK1 receptor antagonists in the exploration of physiological functions of substance P and neurokinin A.

PubMed

Otsuka, M; Yoshioka, K; Yanagisawa, M; Suzuki, H; Zhao, F Y; Guo, J Z; Hosoki, R; Kurihara, T

1995-07-01

Tachykinin NK1 receptor antagonists were used to explore the physiological functions of substance P (SP) and neurokinin A (NKA). Pharmacological profiles of three NK1 receptor antagonists, GR71251, GR82334, and RP 67580, were examined in the isolated spinal cord preparation of the neonatal rat. These tachykinin receptor antagonists exhibited considerable specificities and antagonized the actions of both SP and NKA to induce the depolarization of ventral roots. Electrical stimulation of the saphenous nerve with C-fiber strength evoked a depolarization lasting about 30 s of the ipsilateral L3 ventral root. This response, which is referred to as saphenous-nerve-evoked slow ventral root potential (VRP), was depressed by these NK1 receptor antagonists. In contrast, the saphenous-nerve-evoked slow VRP was potentiated by application of a mixture of peptidase inhibitors, including thiorphan, actinonin, and captopril in the presence of naloxone, but not after further addition of GR71251. Likewise, in the isolated coeliac ganglion of the guinea pig, electrical stimulation of the mesenteric nerves evoked in some ganglionic cells slow excitatory postsynaptic potentials (EPSPs), which were depressed by GR71251 and potentiated by peptidase inhibitors. These results further support the notion that SP and NKA serve as neurotransmitters producing slow EPSPs in the neonatal rat spinal cord and guinea pig prevertebral ganglia.

Nanoscale Zinc Oxide Particles for Improving the Physiological and Sanitary Quality of a Mexican Landrace of Red Maize

PubMed Central

Estrada-Urbina, Juan; Cruz-Alonso, Alejandro; Santander-González, Martha; Vázquez-Durán, Alma

2018-01-01

In this research, quasi-spherical-shaped zinc oxide nanoparticles (ZnO NPs) were synthesized by a simple cost-competitive aqueous precipitation method. The engineered NPs were characterized using several validation methodologies: UV–Vis spectroscopy, diffuse reflection UV–Vis, spectrofluorometry, transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Fourier transform infrared (FTIR) spectroscopy with attenuated total reflection (ATR). A procedure was established to coat a landrace of red maize using gelatinized maize starch. Each maize seed was treated with 0.16 mg ZnO NPs (~7.7 × 109 particles). The standard germination (SG) and accelerated aging (AA) tests indicated that ZnO NP-treated maize seeds presented better physiological quality (higher percentage of normal seedlings) and sanitary quality (lower percentage of seeds contaminated by microorganisms) as compared to controls. The application of ZnO NPs also improved seedling vigor, correlated to shoot length, shoot diameter, root length, and number of secondary roots. Furthermore, shoots and roots of the ZnO NP-treated maize seeds showed a marked increment in the main active FTIR band areas, most notably for the vibrations associated with peptide-protein, lipid, lignin, polysaccharide, hemicellulose, cellulose, and carbohydrate. From these results, it is concluded that ZnO NPs have potential for applications in peasant agriculture to improve the quality of small-scale farmers’ seeds and, as a result, preserve germplasm resources. PMID:29673162

In vitro Cultured Primary Roots Derived from Stem Segments of Cassava (Manihot esculenta) Can Behave Like Storage Organs

PubMed Central

Medina, Ricardo D.; Faloci, Mirta M.; Gonzalez, Ana M.; Mroginski, Luis A.

2007-01-01

Background and Aims Cassava (Manihot esculenta) has three adventitious root types: primary and secondary fibrous roots, and storage roots. Different adventitious root types can also regenerate from in vitro cultured segments. The aim of this study was to investigate aspects of in vitro production of storage roots. Methods Morphological and anatomical analyses were performed to identify and differentiate each root type. Twenty-nine clones were assayed to determine the effect of genotype on the capacity to form storage roots in vitro. The effects of cytokinins and auxins on the formation of storage roots in vitro were also examined. Key Results Primary roots formed in vitro and in vivo had similar tissue kinds; however, storage roots formed in vitro exhibited physiological specialization for storing starch. The only consistent diagnostic feature between secondary fibrous and storage roots was their functional differentiation. Anatomical analysis of the storage roots formed in vitro showed that radial expansion as a consequence of massive proliferation and enlargement of parenchymatous cells occurred in the middle cortex, but not from cambial activity as in roots formed in vivo. Cortical expansion could be related to dilatation growth favoured by hormone treatments. Starch deposition of storage roots formed in vitro was confined to cortical tissue and occurred earlier than in storage roots formed in vivo. Auxin and cytokinin supplementation were absolutely required for in vitro storage root regeneration; these roots were not able to develop secondary growth, but formed a tissue competent for starch storing. MS medium with 5 % sucrose plus 0·54 μm 1-naphthaleneacetic acid and 0·44 μm 6-benzylaminopurine was one of the most effective in stimulating the storage root formation. Genotypes differed significantly in their capacity to produce storage roots in vitro. Storage root formation was considerably affected by the segment's primary position and strongly influenced by hormone treatments. Conclusions The storage root formation system reported here is a first approach to develop a tuberization model, and additional efforts are required to improve it. Although it was not possible to achieve root secondary growth, after this work it will be feasible to advance in some aspects of in vitro cassava tuberization. PMID:17267513

Scientific/Technical Report Bioenergetics Research Initiative Award number-DE-FG02-05ER64092

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trappe, Scott A

2009-12-04

General Project Overview and Final Technical Report This equipment grant was utilized to enhance the infrastructure of the Human Performance Laboratory at Ball State University. The laboratories primary focus is human based exercise physiology conducting research in the areas of sports performance, aging and exercise, unloading (space flight and bed rest), pediatric exercise and clinical exercise physiology. The main equipment supported by this grant was an ultrasound unit for cardiac and skeletal muscle imaging at the whole organ level, microscope system for micro imaging of skeletal muscle tissue, running treadmill for energy expenditure assessment, autoclave for sterilization, and upgrade tomore » our dual x–ray absorptiometry (DEXA) system that was utilized for body composition measurements. The equipment was involved in several human metabolic and skeletal muscle research projects as highlighted above. In particular, this equipment served a support role for other large–scale clinical projects funded by the National Institutes of Health (NIH), National Aeronautics and Space Administration (NASA), and corporate sponsors.« less

Root Cortical Aerenchyma Enhances Nitrogen Acquisition from Low-Nitrogen Soils in Maize1[W][OPEN

PubMed Central

Saengwilai, Patompong; Nord, Eric A.; Chimungu, Joseph G.; Brown, Kathleen M.; Lynch, Jonathan Paul

2014-01-01

Suboptimal nitrogen (N) availability is a primary constraint for crop production in developing nations, while in rich nations, intensive N fertilization carries substantial environmental and economic costs. Therefore, understanding root phenes that enhance N acquisition is of considerable importance. Structural-functional modeling predicts that root cortical aerenchyma (RCA) could improve N acquisition in maize (Zea mays). We evaluated the utility of RCA for N acquisition by physiological comparison of maize recombinant inbred lines contrasting in RCA grown under suboptimal and adequate N availability in greenhouse mesocosms and in the field in the United States and South Africa. N stress increased RCA formation by 200% in mesocosms and by 90% to 100% in the field. RCA formation substantially reduced root respiration and root N content. Under low-N conditions, RCA formation increased rooting depth by 15% to 31%, increased leaf N content by 28% to 81%, increased leaf chlorophyll content by 22%, increased leaf CO2 assimilation by 22%, increased vegetative biomass by 31% to 66%, and increased grain yield by 58%. Our results are consistent with the hypothesis that RCA improves plant growth under N-limiting conditions by decreasing root metabolic costs, thereby enhancing soil exploration and N acquisition in deep soil strata. Although potential fitness tradeoffs of RCA formation are poorly understood, increased RCA formation appears be a promising breeding target for enhancing crop N acquisition. PMID:24891611

BAM 1 and RECEPTOR-LIKE PROTEIN KINASE 2 constitute a signaling pathway and modulate CLE peptide-triggered growth inhibition in Arabidopsis root.

PubMed

Shimizu, Noriko; Ishida, Takashi; Yamada, Masashi; Shigenobu, Shuji; Tabata, Ryo; Kinoshita, Atsuko; Yamaguchi, Katsushi; Hasebe, Mitsuyasu; Mitsumasu, Kanako; Sawa, Shinichiro

2015-12-01

Ligand receptor-based signaling is a means of cell-to-cell communication for coordinating developmental and physiological processes in multicellular organisms. In plants, cell-producing meristems utilize this signaling to regulate their activities and ensure for proper development. Shoot and root systems share common requirements for carrying out this process; however, its molecular basis is largely unclear. It has been suggested that synthetic CLV3/EMBRYO SURROUNDING REGION (CLE) peptide shrinks the root meristem through the actions of CLAVATA2 (CLV2) and the RECEPTOR-LIKE PROTEIN KINASE 2 (RPK2) pathway in Arabidopsis thaliana. Our genetic screening for mutations that resist CLE peptide signaling in roots determined that BAM1, which is a member of the leucine-rich repeat receptor-like kinase (LRR-RLK) family, is also involved in this pathway. BAM1 is preferentially expressed in the root tip, including the quiescent center and its surrounding stem cells. Our genetic analysis revealed that BAM1 functions together with RPK2. Using coimmunoprecipitation assay, we showed that BAM1 is capable of forming heteromeric complexes with RPK2. These findings suggest that the BAM1 and RPK2 receptors constitute a signaling pathway that modulates cell proliferation in the root meristem and that related molecules are employed in root and shoot meristems. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Identification of differentially accumulated proteins involved in regulating independent and combined osmosis and cadmium stress response in Brachypodium seedling roots.

PubMed

Chen, Ziyan; Zhu, Dong; Wu, Jisu; Cheng, Zhiwei; Yan, Xing; Deng, Xiong; Yan, Yueming

2018-05-17

In this study, we aimed to identify differentially accumulated proteins (DAPs) involved in PEG mock osmotic stress, cadmium (Cd 2+ ) stress, and their combined stress responses in Brachypodium distachyon seedling roots. The results showed that combined PEG and Cd 2+ stresses had more significant effects on Brachypodium seedling root growth, physiological traits, and ultrastructures when compared with each individual stress. Totally, 106 DAPs were identified that are responsive to individual and combined stresses in roots. These DAPs were mainly involved in energy metabolism, detoxification and stress defense and protein metabolism. Principal component analysis revealed that DAPs from Cd 2+ and combined stress treatments were grouped closer than those from osmotic stress treatment, indicating that Cd 2+ and combined stresses had more severe influences on the root proteome than osmotic stress alone. Protein-protein interaction analyses highlighted a 14-3-3 centered sub-network that synergistically responded to osmotic and Cd 2+ stresses and their combined stresses. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis of 14 key DAP genes revealed that most genes showed consistency between transcriptional and translational expression patterns. A putative pathway of proteome metabolic changes in Brachypodium seedling roots under different stresses was proposed, which revealed a complicated synergetic responsive network of plant roots to adverse environments.

New insights into root gravitropic signalling

PubMed Central

Sato, Ethel Mendocilla; Hijazi, Hussein; Bennett, Malcolm J.; Vissenberg, Kris; Swarup, Ranjan

2015-01-01

An important feature of plants is the ability to adapt their growth towards or away from external stimuli such as light, water, temperature, and gravity. These responsive plant growth movements are called tropisms and they contribute to the plant’s survival and reproduction. Roots modulate their growth towards gravity to exploit the soil for water and nutrient uptake, and to provide anchorage. The physiological process of root gravitropism comprises gravity perception, signal transmission, growth response, and the re-establishment of normal growth. Gravity perception is best explained by the starch–statolith hypothesis that states that dense starch-filled amyloplasts or statoliths within columella cells sediment in the direction of gravity, resulting in the generation of a signal that causes asymmetric growth. Though little is known about the gravity receptor(s), the role of auxin linking gravity sensing to the response is well established. Auxin influx and efflux carriers facilitate creation of a differential auxin gradient between the upper and lower side of gravistimulated roots. This asymmetric auxin gradient causes differential growth responses in the graviresponding tissue of the elongation zone, leading to root curvature. Cell biological and mathematical modelling approaches suggest that the root gravitropic response begins within minutes of a gravity stimulus, triggering genomic and non-genomic responses. This review discusses recent advances in our understanding of root gravitropism in Arabidopsis thaliana and identifies current challenges and future perspectives. PMID:25547917

Host Genotype and Nitrogen Form Shape the Root Microbiome of Pinus radiata.

PubMed

Gallart, Marta; Adair, Karen L; Love, Jonathan; Meason, Dean F; Clinton, Peter W; Xue, Jianming; Turnbull, Matthew H

2018-02-01

A central challenge in community ecology is understanding the role that phenotypic variation among genotypes plays in structuring host-associated communities. While recent studies have investigated the relationship between plant genotype and the composition of soil microbial communities, the effect of genotype-by-environment interactions on the plant microbiome remains unclear. In this study, we assessed the influence of tree genetics (G), nitrogen (N) form and genotype-by-environment interaction (G x N) on the composition of the root microbiome. Rhizosphere communities (bacteria and fungi) and root-associated fungi (including ectomycorrhizal and saprotrophic guilds) were characterised in two genotypes of Pinus radiata with contrasting physiological responses to exogenous organic or inorganic N supply. Genotype-specific responses to N form influenced the composition of the root microbiome. Specifically, (1) diversity and composition of rhizosphere bacterial and root-associated fungal communities differed between genotypes that had distinct responses to N form, (2) shifts in the relative abundance of individual taxa were driven by the main effects of N form or host genotype and (3) the root microbiome of the P. radiata genotype with the most divergent growth responses to organic and inorganic N was most sensitive to differences in N form. Our results show that intraspecific variation in tree response to N form has significant consequences for the root microbiome of P. radiata, demonstrating the importance of genotype-by-environment interactions in shaping host-associated communities.

Plasma membrane proteome analysis identifies a role of barley membrane steroid binding protein in root architecture response to salinity.

PubMed

Witzel, Katja; Matros, Andrea; Møller, Anders L B; Ramireddy, Eswarayya; Finnie, Christine; Peukert, Manuela; Rutten, Twan; Herzog, Andreas; Kunze, Gotthard; Melzer, Michael; Kaspar-Schoenefeld, Stephanie; Schmülling, Thomas; Svensson, Birte; Mock, Hans-Peter

2018-06-01

Although the physiological consequences of plant growth under saline conditions have been well described, understanding the core mechanisms conferring plant salt adaptation has only started. We target the root plasma membrane proteomes of two barley varieties, cvs. Steptoe and Morex, with contrasting salinity tolerance. In total, 588 plasma membrane proteins were identified by mass spectrometry, of which 182 were either cultivar or salinity stress responsive. Three candidate proteins with increased abundance in the tolerant cv. Morex were involved either in sterol binding (a GTPase-activating protein for the adenosine diphosphate ribosylation factor [ZIGA2], and a membrane steroid binding protein [MSBP]) or in phospholipid synthesis (phosphoethanolamine methyltransferase [PEAMT]). Overexpression of barley MSBP conferred salinity tolerance to yeast cells, whereas the knock-out of the heterologous AtMSBP1 increased salt sensitivity in Arabidopsis. Atmsbp1 plants showed a reduced number of lateral roots under salinity, and root-tip-specific expression of barley MSBP in Atmsbp1 complemented this phenotype. In barley, an increased abundance of MSBP correlates with reduced root length and lateral root formation as well as increased levels of auxin under salinity being stronger in the tolerant cv. Morex. Hence, we concluded the involvement of MSBP in phytohormone-directed adaptation of root architecture in response to salinity. © 2018 John Wiley & Sons Ltd.

Sequential depolarization of root cortical and stelar cells induced by an acute salt shock - implications for Na(+) and K(+) transport into xylem vessels.

PubMed

Wegner, Lars H; Stefano, Giovanni; Shabala, Lana; Rossi, Marika; Mancuso, Stefano; Shabala, Sergey

2011-05-01

Early events in NaCl-induced root ion and water transport were investigated in maize (Zea mays L) roots using a range of microelectrode and imaging techniques. Addition of 100 mm NaCl to the bath resulted in an exponential drop in root xylem pressure, rapid depolarization of trans-root potential and a transient drop in xylem K(+) activity (A(K+) ) within ∼1 min after stress onset. At this time, no detectable amounts of Na(+) were released into the xylem vessels. The observed drop in A(K+) was unexpected, given the fact that application of the physiologically relevant concentrations of Na(+) to isolated stele has caused rapid plasma membrane depolarization and a subsequent K(+) efflux from the stelar tissues. This controversy was explained by the difference in kinetics of NaCl-induced depolarization between cortical and stelar cells. As root cortical cells are first to be depolarized and lose K(+) to the environment, this is associated with some K(+) shift from the stelar symplast to the cortex, resulting in K(+) being transiently removed from the xylem. Once Na(+) is loaded into the xylem (between 1 and 5 min of root exposure to NaCl), stelar cells become more depolarized, and a gradual recovery in A(K+) occurs. © 2011 Blackwell Publishing Ltd.

Contrasting physiological effects of partial root zone drying in field-grown grapevine (Vitis vinifera L. cv. Monastrell) according to total soil water availability

PubMed Central

Romero, Pascual; Dodd, Ian C.; Martinez-Cutillas, Adrian

2012-01-01

Different spatial distributions of soil moisture were imposed on field-grown grapevines by applying the same irrigation volumes to the entire (DI; deficit irrigation) or part of the (PRD; partial root zone drying) root zone. Five treatments were applied: controls irrigated at 60% ETc (crop evapotranspiration) for the whole season (308 mm year−1); DI-1 and PRD-1 that received the same irrigation as controls before fruit set, 30% ETc from fruit set to harvest and 45% ETc post-harvest (192 mm year−1); and DI-2 and PRD-2 that were the same, except that 15% ETc was applied from fruit set to harvest (142 mm year−1). Compared with DI-1, PRD-1 maintained higher leaf area post-veraison and increased root water uptake, whole-plant hydraulic conductance, leaf transpiration, stomatal conductance, and photosynthesis, but decreased intrinsic gas exchange efficiency without causing differences in leaf xylem abscisic acid (ABA) concentration. Compared with DI-2, PRD-2 increased leaf xylem ABA concentration and decreased root water uptake, whole-plant hydraulic conductance, leaf transpiration, stomatal conductance, and photosynthesis, mainly at the beginning of PRD cycles. Distinctive PRD effects (e.g. greater stomatal closure) depended on the volumetric soil water content of the wet root zone, as predicted from a model of root-to-shoot ABA signalling. PMID:22451721

Use of ex vitro composite plants to study the interaction of cowpea (Vigna unguiculata L.) with the root parasitic angiosperm Striga gesnerioides

PubMed Central

2012-01-01

Background Cowpea (Vigna unguiculata L.) is an important grain and forage legume grown throughout sub-Saharan Africa primarily by subsistence farmers on poor, drought prone soils. Genetic improvement of the crop is being actively pursued and numerous functional genomics studies are underway aimed at characterizing gene controlling key agronomic characteristics for disease and pest resistances. Unfortunately, similar to other legumes, efficient plant transformation technology is a rate-limiting step in analysis of gene function in cowpea. Results Here we describe an optimized protocol for the rapid generation of transformed hairy roots on ex vitro composite plants of cowpea using Agrobacterium rhizogenes. We further demonstrate the applicability of cowpea composite plants to study gene expression involved in the resistance response of the plant roots to attack by the root parasitic weed, Striga gesnerioides. The utility of the new system and critical parameters of the method are described and discussed herein. Conclusions Cowpea composite plants offer a rapid alternative to methods requiring stable transformation and whole plant regeneration for studying gene expression in resistance or susceptibility responses to parasitic weeds. Their use can likely be readily adapted to look at the effects of both ectopic gene overexpression as well as gene knockdown of root associated defense responses and to the study of a broader range of root associated physiological and aphysiological processes including root growth and differentiation as well as interactions with other root pests, parasites, and symbionts. PMID:22741546

SABRE is required for stabilization of root hair patterning in Arabidopsis thaliana.

PubMed

Pietra, Stefano; Lang, Patricia; Grebe, Markus

2015-03-01

Patterned differentiation of distinct cell types is essential for the development of multicellular organisms. The root epidermis of Arabidopsis thaliana is composed of alternating files of root hair and non-hair cells and represents a model system for studying the control of cell-fate acquisition. Epidermal cell fate is regulated by a network of genes that translate positional information from the underlying cortical cell layer into a specific pattern of differentiated cells. While much is known about the genes of this network, new players continue to be discovered. Here we show that the SABRE (SAB) gene, known to mediate microtubule organization, anisotropic cell growth and planar polarity, has an effect on root epidermal hair cell patterning. Loss of SAB function results in ectopic root hair formation and destabilizes the expression of cell fate and differentiation markers in the root epidermis, including expression of the WEREWOLF (WER) and GLABRA2 (GL2) genes. Double mutant analysis reveal that wer and caprice (cpc) mutants, defective in core components of the epidermal patterning pathway, genetically interact with sab. This suggests that SAB may act on epidermal patterning upstream of WER and CPC. Hence, we provide evidence for a role of SAB in root epidermal patterning by affecting cell-fate stabilization. Our work opens the door for future studies addressing SAB-dependent functions of the cytoskeleton during root epidermal patterning. © 2014 The Authors. Physiologia Plantarum published by John Wiley & Sons Ltd on behalf of Scandinavian Plant Physiology Society.

Discerning morpho-anatomical, physiological and molecular multiformity in cultivated and wild genotypes of lentil with reconciliation to salinity stress

PubMed Central

Singh, Chandan Kumar; Kumari, Shanti; Singh Tomar, Ram Sewak; Karwa, Sourabh; Singh, Rajendra; Singh, Raja Bahadur; Sarkar, Susheel Kumar; Pal, Madan

2017-01-01

One hundred and sixty two genotypes of different Lens species were screened for salinity tolerance in hydroponics at 40, 80 and 120 mM sodium chloride (NaCl) for 30 d. The germination, seedling growth, biomass accumulation, seedling survivability, salinity scores, root and shoot anatomy, sodium ion (Na+), chloride ion (Cl-) and potassium ion (K+) concentrations, proline and antioxidant activities were measured to evaluate the performance of all the genotypes. The results were compared in respect of physiological (Na+, K+ and Cl-) and seed yield components obtained from field trials for salinity stress conducted during two years. Expression of salt tolerance in hydroponics was found to be reliable indicator for similarity in salt tolerance between genotypes and was evident in saline soil based comparisons. Impressive genotypic variation for salinity tolerance was observed among the genotypes screened under hydroponic and saline field conditions. Plant concentrations of Na+ and Cl- at 120 mM NaCl were found significantly correlated with germination, root and shoot length, fresh and dry weight of roots and shoots, seedling survivability, salinity scores and K+ under controlled conditions and ranked the genotypes along with their seed yield in the field. Root and shoot anatomy of tolerant line (PDL-1) and wild accession (ILWL-137) showed restricted uptake of Na+ and Cl- due to thick layer of their epidermis and endodermis as compared to sensitive cultigen (L-4076). All the genotypes were scanned using SSR markers for genetic diversity, which generated high polymorphism. On the basis of cluster analysis and population structure the contrasting genotypes were grouped into different classes. These markers may further be tested to explore their potential in marker-assisted selection. PMID:28542267

Discerning morpho-anatomical, physiological and molecular multiformity in cultivated and wild genotypes of lentil with reconciliation to salinity stress.

PubMed

Singh, Dharmendra; Singh, Chandan Kumar; Kumari, Shanti; Singh Tomar, Ram Sewak; Karwa, Sourabh; Singh, Rajendra; Singh, Raja Bahadur; Sarkar, Susheel Kumar; Pal, Madan

2017-01-01

One hundred and sixty two genotypes of different Lens species were screened for salinity tolerance in hydroponics at 40, 80 and 120 mM sodium chloride (NaCl) for 30 d. The germination, seedling growth, biomass accumulation, seedling survivability, salinity scores, root and shoot anatomy, sodium ion (Na+), chloride ion (Cl-) and potassium ion (K+) concentrations, proline and antioxidant activities were measured to evaluate the performance of all the genotypes. The results were compared in respect of physiological (Na+, K+ and Cl-) and seed yield components obtained from field trials for salinity stress conducted during two years. Expression of salt tolerance in hydroponics was found to be reliable indicator for similarity in salt tolerance between genotypes and was evident in saline soil based comparisons. Impressive genotypic variation for salinity tolerance was observed among the genotypes screened under hydroponic and saline field conditions. Plant concentrations of Na+ and Cl- at 120 mM NaCl were found significantly correlated with germination, root and shoot length, fresh and dry weight of roots and shoots, seedling survivability, salinity scores and K+ under controlled conditions and ranked the genotypes along with their seed yield in the field. Root and shoot anatomy of tolerant line (PDL-1) and wild accession (ILWL-137) showed restricted uptake of Na+ and Cl- due to thick layer of their epidermis and endodermis as compared to sensitive cultigen (L-4076). All the genotypes were scanned using SSR markers for genetic diversity, which generated high polymorphism. On the basis of cluster analysis and population structure the contrasting genotypes were grouped into different classes. These markers may further be tested to explore their potential in marker-assisted selection.

Soil moisture controls on phenology and productivity in a semi-arid critical zone.

PubMed

Cleverly, James; Eamus, Derek; Restrepo Coupe, Natalia; Chen, Chao; Maes, Wouter; Li, Longhui; Faux, Ralph; Santini, Nadia S; Rumman, Rizwana; Yu, Qiang; Huete, Alfredo

2016-10-15

The Earth's Critical Zone, where physical, chemical and biological systems interact, extends from the top of the canopy to the underlying bedrock. In this study, we investigated soil moisture controls on phenology and productivity of an Acacia woodland in semi-arid central Australia. Situated on an extensive sand plain with negligible runoff and drainage, the carry-over of soil moisture content (θ) in the rhizosphere enabled the delay of phenology and productivity across seasons, until conditions were favourable for transpiration of that water to prevent overheating in the canopy. Storage of soil moisture near the surface (in the top few metres) was promoted by a siliceous hardpan. Pulsed recharge of θ above the hardpan was rapid and depended upon precipitation amount: 150mm storm(-1) resulted in saturation of θ above the hardpan (i.e., formation of a temporary, discontinuous perched aquifer above the hardpan in unconsolidated soil) and immediate carbon uptake by the vegetation. During dry and inter-storm periods, we inferred the presence of hydraulic lift from soil storage above the hardpan to the surface due to (i) regular daily drawdown of θ in the reservoir that accumulates above the hardpan in the absence of drainage and evapotranspiration; (ii) the dimorphic root distribution wherein most roots were found in dry soil near the surface, but with significant root just above the hardpan; and (iii) synchronisation of phenology amongst trees and grasses in the dry season. We propose that hydraulic redistribution provides a small amount of moisture that maintains functioning of the shallow roots during long periods when the surface soil layer was dry, thereby enabling Mulga to maintain physiological activity without diminishing phenological and physiological responses to precipitation when conditions were favourable to promote canopy cooling. Copyright © 2016 Elsevier B.V. All rights reserved.

Tissue-specific root ion profiling reveals essential roles of the CAX and ACA calcium transport systems in response to hypoxia in Arabidopsis

PubMed Central

Wang, Feifei; Chen, Zhong-Hua; Liu, Xiaohui; Colmer, Timothy David; Zhou, Meixue; Shabala, Sergey

2016-01-01

Waterlogging is a major abiotic stress that limits the growth of plants. The crucial role of Ca2+ as a second messenger in response to abiotic and biotic stimuli has been widely recognized in plants. However, the physiological and molecular mechanisms of Ca2+ distribution within specific cell types in different root zones under hypoxia is poorly understood. In this work, whole-plant physiological and tissue-specific Ca2+ changes were studied using several ACA (Ca2+-ATPase) and CAX (Ca2+/proton exchanger) knock-out Arabidopsis mutants subjected to waterlogging treatment. In the wild-type (WT) plants, several days of hypoxia decreased the expression of ACA8, CAX4, and CAX11 by 33% and 50% compared with the control. The hypoxic treatment also resulted in an up to 11-fold tissue-dependent increase in Ca2+ accumulation in root tissues as revealed by confocal microscopy. The increase was much higher in stelar cells in the mature zone of Arabidopsis mutants with loss of function for ACA8, ACA11, CAX4, and CAX11. In addition, a significantly increased Ca2+ concentration was found in the cytosol of stelar cells in the mature zone after hypoxic treatment. Three weeks of waterlogging resulted in dramatic loss of shoot biomass in cax11 plants (67% loss in shoot dry weight), while in the WT and other transport mutants this decline was only 14–22%. These results were also consistent with a decline in leaf chlorophyll fluorescence (F v/F m). It is suggested that CAX11 plays a key role in maintaining cytosolic Ca2+ homeostasis and/or signalling in root cells under hypoxic conditions. PMID:26889007

Differences in hydraulic architecture between mesic and xeric Pinus pinaster populations at the seedling stage.

PubMed

Corcuera, Leyre; Gil-Pelegrín, Eustaquio; Notivol, Eduardo

2012-12-01

We studied the intraspecific variability of maritime pine in a set of morphological and physiological traits: soil-to-leaf hydraulic conductance, intrinsic water-use efficiency (WUE, estimated by carbon isotope composition, δ(13)C), root morphology, xylem anatomy, growth and carbon allocation patterns. The data were collected from Pinus pinaster Aiton seedlings (25 half-sib families from five populations) grown in a greenhouse and subjected to water and water-stress treatments. The aims were to relate this variability to differences in water availability at the geographic location of the populations, and to study the potential trade-offs among traits. The drought-stressed seedlings demonstrated a decrease in hydraulic conductance and root surface area and increased WUE and root tip number. The relationships among the growth, morphological, anatomical and physiological traits changed with the scale of study: within the species, among/within populations. The populations showed a highly significant relationship between the percentage reduction in whole-plant hydraulic conductance and WUE. The differences among the populations in root morphology, whole-plant conductance, carbon allocation, plant growth and WUE were significant and consistent with dryness of the site of seed origin. The xeric populations exhibited lower growth and a conservative water use, as opposed to the fast-growing, less water-use-efficient populations from mesic habitats. The xeric and mesic populations, Tamrabta and San Cipriano, respectively, showed the most contrasting traits and were clustered in opposite directions along the main axis in the canonical discriminant analysis under both the control and drought treatments. The results suggest the possibility of selecting the Arenas population, which presents a combination of traits that confer increased growth and drought resistance.

Anatomical and Physiological Responses of Citrus Trees to Varying Boron Availability Are Dependent on Rootstock.

PubMed

Mesquita, Geisa L; Zambrosi, Fernando C B; Tanaka, Francisco A O; Boaretto, Rodrigo M; Quaggio, José A; Ribeiro, Rafael V; Mattos, Dirceu

2016-01-01

In Citrus, water, nutrient transport and thereby fruit production, are influenced among other factors, by the interaction between rootstock and boron (B) nutrition. This study aimed to investigate how B affects the anatomical structure of roots and leaves as well as leaf gas exchange in sweet orange trees grafted on two contrasting rootstocks in response to B supply. Plants grafted on Swingle citrumelo or Sunki mandarin were grown in a nutrient solution of varying B concentration (deficient, adequate, and excessive). Those grafted on Swingle were more tolerant to both B deficiency and toxicity than those on Sunki, as revealed by higher shoot and root growth. In addition, plants grafted on Sunki exhibited more severe anatomical and physiological damages under B deficiency, showing thickening of xylem cell walls and impairments in whole-plant leaf-specific hydraulic conductance and leaf CO2 assimilation. Our data revealed that trees grafted on Swingle sustain better growth under low B availablitlity in the root medium and still respond positively to increased B levels by combining higher B absorption and root growth as well as better organization of xylem vessels. Taken together, those traits improved water and B transport to the plant canopy. Under B toxicity, Swingle rootstock would also favor plant growth by reducing anatomical and ultrastructural damage to leaf tissue and improving water transport compared with plants grafted on Sunki. From a practical point of view, our results highlight that B management in citrus orchards shall take into account rootstock varieties, of which the Swingle rootstock was characterized by its performance on regulating anatomical and ultrastructural damages, improving water transport and limiting negative impacts of B stress conditions on plant growth.

Microbial Growth and Carbon Use Efficiency in the Rhizosphere and Root-Free Soil

PubMed Central

Blagodatskaya, Evgenia; Blagodatsky, Sergey; Anderson, Traute-Heidi; Kuzyakov, Yakov

2014-01-01

Plant-microbial interactions alter C and N balance in the rhizosphere and affect the microbial carbon use efficiency (CUE)–the fundamental characteristic of microbial metabolism. Estimation of CUE in microbial hotspots with high dynamics of activity and changes of microbial physiological state from dormancy to activity is a challenge in soil microbiology. We analyzed respiratory activity, microbial DNA content and CUE by manipulation the C and nutrients availability in the soil under Beta vulgaris. All measurements were done in root-free and rhizosphere soil under steady-state conditions and during microbial growth induced by addition of glucose. Microorganisms in the rhizosphere and root-free soil differed in their CUE dynamics due to varying time delays between respiration burst and DNA increase. Constant CUE in an exponentially-growing microbial community in rhizosphere demonstrated the balanced growth. In contrast, the CUE in the root-free soil increased more than three times at the end of exponential growth and was 1.5 times higher than in the rhizosphere. Plants alter the dynamics of microbial CUE by balancing the catabolic and anabolic processes, which were decoupled in the root-free soil. The effects of N and C availability on CUE in rhizosphere and root-free soil are discussed. PMID:24722409

Physiological assessment and path coefficient analysis to improve evaluation of alfalfa autotoxicity.

PubMed

Chon, Sang-Uk; Nelson, C Jerry; Coutts, John H

2003-11-01

Reseeding of alfalfa is affected until autotoxic chemicals break down or are dispersed, often requiring a year or more. Bioassays of seed germination and early seedling growth, on agar medium in petri dishes, were conducted to evaluate autotoxic responses of 20 alfalfa germplasms to water-soluble extracts of alfalfa leaf tissue. Root length, 120 hr after placing imbibed seed on agar, was more sensitive to the autotoxin(s) than was hypocotyl length, germination speed, and final germination percentage. Path coefficient analyses showed variation in root length had 7-17 times more effect than variation in hypocotyl length in determining autotoxic effects on total seedling length. Although variations in seed size and germination rate were negatively associated (P < 0.05) with final root length, the autotoxin had little effect on these factors relative to that on root length. Germplasms in the control differed (P < 0.05) in root length, requiring tolerance to be evaluated as percent of control. Germplasms, as percent of control, differed significantly (P < 0.05) at extract concentrations of 1.0 and 4.0 g l(-1), but the range and LSD were more favorable for selection at 1.0 g l(-1). Root length is appropriate for genetic assessments of tolerance to the autotoxin when expressed as percent of control.

Physiological response of Cistus monspeliensis L. growing in two mine areas of the Iberian Pyrite Belt

NASA Astrophysics Data System (ADS)

Arenas Lago, Daniel; Carvalho, Luisa C.; Santos, Erika S.; Abreu, Maria Manuela; Andrade, María Luisa

2015-04-01

São Domingos and Lousal mines, nowadays in abandoned state, are located in Portugal, in the Iberian Pyrite Belt, a world-class volcanic-hosted massive sulfide. As a result of the intense mining activity large volumes of wastes containing metal(loid)s were partly exposed to weathering realising potential hazardous elements contaminating waters, soils and sediments. In both mines, a great part of the contaminated areas is relatively covered by several wild species. These species have developed mechanisms of response to oxidative stress originated by high concentration of metal(loid)s in plant tissues, whose presence leads to the formation of reactive oxygen species, thus causing oxidative damage. The main objective of this study was to evaluate changes in the ecophysiological behaviour of Cistus monspeliensis L., which grows spontaneously in both mine areas, in soils containing high concentrations of metal(loid)s. With this purpose, the variation of some physiological parameters was analysed in order to identify which parameters can be indicators of the plant'sresponse to oxidative stress. Representative soils from rhizosphere and plants were sampled, in the same locations, in different areas of São Domingos and Lousal mines and in an uncontaminated area nearby São Domingos. Soils were characterized for the classic properties. Multielemental total concentration was analysed in soils and plants (shoots and roots), and multielemental concentration in the available fraction of soils. Pigments (chlorophylls, anthocyanins and carotenoids), glutathione, ascorbate, H2O2 and antioxidative enzyme activities were measured in plant shoots. In general, total and available concentrations (mg/kg) of Zn (total 149-463; available 2-16), As (total 62-3030; available 0.03-1.9), Cd (total 0.3-1.2; available 0.01-0.05), Cu (total 79-375; available 0.8-10) and Pb (total 95-9210; available 0.2-40) are significantly higher in mine soils than in uncontaminated soils Zn (total 92-123; available <0.6), As (total 18-20; available <0.08), Cd (total <0.3; available <0.01), Cu (total 25-47; available <0.1) and Pb (total 28-50; < available 0.08). Also, shoots and roots of the plants collected in both mine areas contain in general higher concentrations (mg/kg) of As (shoot 0.6-75; root 0.8-13.5)and Pb (shoot 2.5-35; root 1.8-91) than plants from uncontaminated soils (As (shoot 0.8-1.2; root <0.8); Pb (shoot <3.2; root 4-9)). Physiological analyses showed a decrease in chlorophylls, anthocyanins, ascorbic acid levels and percentage of glutathione in shoots of C. monspeliensis collected in contaminated areas compared to the plants growing on uncontaminated soils. The decrease in anthocyanins is correlated with the content of Cd and Zn in plants shoots. A negative correlation was observed between carotenoid contents and Cd concentration in shoots in both mine areas. Arsenic and Cd concentrations were correlated positively with an increase of glutathione in plants grown on mine soils. Moreover, high concentrations of metals in mine soils triggered defence mechanisms against oxidative stress, in the form of increased antioxidative enzyme activity. Therefore, these results reveal that C. monspeliensis is a species adapted to unfavourable environments with high concentrations of metal(loid)s, adjusting its tolerance mechanisms at the metabolic and physiological levels.

Genetic and chemical reductions in protein phosphatase activity alter auxin transport, gravity response, and lateral root growth

NASA Technical Reports Server (NTRS)

Rashotte, A. M.; DeLong, A.; Muday, G. K.; Brown, C. S. (Principal Investigator)

2001-01-01

Auxin transport is required for important growth and developmental processes in plants, including gravity response and lateral root growth. Several lines of evidence suggest that reversible protein phosphorylation regulates auxin transport. Arabidopsis rcn1 mutant seedlings exhibit reduced protein phosphatase 2A activity and defects in differential cell elongation. Here we report that reduced phosphatase activity alters auxin transport and dependent physiological processes in the seedling root. Root basipetal transport was increased in rcn1 or phosphatase inhibitor-treated seedlings but showed normal sensitivity to the auxin transport inhibitor naphthylphthalamic acid (NPA). Phosphatase inhibition reduced root gravity response and delayed the establishment of differential auxin-induced gene expression across a gravity-stimulated root tip. An NPA treatment that reduced basipetal transport in rcn1 and cantharidin-treated wild-type plants also restored a normal gravity response and asymmetric auxin-induced gene expression, indicating that increased basipetal auxin transport impedes gravitropism. Increased auxin transport in rcn1 or phosphatase inhibitor-treated seedlings did not require the AGR1/EIR1/PIN2/WAV6 or AUX1 gene products. In contrast to basipetal transport, root acropetal transport was normal in phosphatase-inhibited seedlings in the absence of NPA, although it showed reduced NPA sensitivity. Lateral root growth also exhibited reduced NPA sensitivity in rcn1 seedlings, consistent with acropetal transport controlling lateral root growth. These results support the role of protein phosphorylation in regulating auxin transport and suggest that the acropetal and basipetal auxin transport streams are differentially regulated.

Aeroponics for adventitious rhizogenesis in evergreen haloxeric tree Tamarix aphylla (L.) Karst.: influence of exogenous auxins and cutting type.

PubMed

Sharma, Udit; Kataria, Vinod; Shekhawat, N S

2018-02-01

Tamarix aphylla (L.) Karst., a drought resistant halophyte tree, is an agroforestry species which can be used for reclamation of waterlogged saline and marginal lands. Due to very low seed viability and unsuitable conditions for seed germination, the tree is becoming rare in Indian Thar desert. Present study concerns the evaluation of aeroponics technique for vegetative propagation of T. aphylla . Effect of various exogenous auxins (indole-3-acetic acid, indole-3-butyric acid, naphthalene acetic acid) at different concentrations (0.0, 1.0, 2.0, 3.0, 5.0, 10.0 mg l -1 ) was examined for induction of adventitious rooting and other morphological features. Among all three auxins tested individually, maximum rooting response (79%) was observed with IBA 2.0 mg l -1 . However, stem cuttings treated with a combination of auxins (2.0 mg l -1 IBA and 1.0 mg l -1 IAA) for 15 min resulted in 87% of rooting response. Among three types of stem cuttings (apical shoot, newly sprouted cuttings, mature stem cuttings), maximum rooting (~ 90%) was observed on mature stem cuttings. Number of roots and root length were significantly higher in aeroponically rooted stem cuttings as compared to stem cuttings rooted in soil conditions. Successfully rooted and sprouted plants were transferred to polybags with 95% survival rate. This is the first report on aeroponic culture of Tamarix aphylla which can be utilized in agroforestry practices, marginal land reclamation and physiological studies.

Root Structure and Functioning for Efficient Acquisition of Phosphorus: Matching Morphological and Physiological Traits

PubMed Central

LAMBERS, HANS; SHANE, MICHAEL W.; CRAMER, MICHAEL D.; PEARSE, STUART J.; VENEKLAAS, ERIK J.

2006-01-01

• Background Global phosphorus (P) reserves are being depleted, with half-depletion predicted to occur between 2040 and 2060. Most of the P applied in fertilizers may be sorbed by soil, and not be available for plants lacking specific adaptations. On the severely P-impoverished soils of south-western Australia and the Cape region in South Africa, non-mycorrhizal species exhibit highly effective adaptations to acquire P. A wide range of these non-mycorrhizal species, belonging to two monocotyledonous and eight dicotyledonous families, produce root clusters. Non-mycorrhizal species with root clusters appear to be particularly effective at accessing P when its availability is extremely low. • Scope There is a need to develop crops that are highly effective at acquiring inorganic P (Pi) from P-sorbing soils. Traits such as those found in non-mycorrhizal root-cluster-bearing species in Australia, South Africa and other P-impoverished environments are highly desirable for future crops. Root clusters combine a specialized structure with a specialized metabolism. Native species with such traits could be domesticated or crossed with existing crop species. An alternative approach would be to develop future crops with root clusters based on knowledge of the genes involved in development and functioning of root clusters. • Conclusions Root clusters offer enormous potential for future research of both a fundamental and a strategic nature. New discoveries of the development and functioning of root clusters in both monocotyledonous and dicotyledonous families are essential to produce new crops with superior P-acquisition traits. PMID:16769731

Relationship between fine-root exudation and respiration of two Quercus species in a Japanese temperate forest.

PubMed

Sun, Lijuan; Ataka, Mioko; Kominami, Yuji; Yoshimura, Kenichi

2017-08-01

Plants allocate a considerable amount of carbon (C) to fine roots as respiration and exudation. Fine-root exudation could stimulate microbial activity, which further contributes to soil heterotrophic respiration. Although both root respiration and exudation are important components of belowground C cycling, how they relate to each other is less well known. In this study, we aimed to explore this relationship on mature trees growing in the field. The measurements were performed on two canopy species, Quercus serrata Thunb. and Quercus glauca, in a warm temperate forest. The respiration and exudation rates of the same fine-root segment were measured in parallel with a syringe-basis incubation and a closed static chamber, respectively. We also measured root traits and ectomycorrhizal colonization ratio because these indexes commonly relate to root respiration and reflect root physiology. The microbial activity enhanced by root exudation was investigated by comparing the dissolved organic carbon (DOC) and microbial biomass carbon (MBC) between rhizosphere soils and bulk soils. Mean DOC concentration and MBC were ca two times higher in the rhizosphere soils and positively related to exudation rates, indicating that exudation further relates to the C dynamics in the soils. Flux rates of exudation and respiration were positively correlated with each other. Both root exudation and respiration rates positively related to ectomycorrhizal colonization and root tissue nitrogen, and therefore the relationship between the two fluxes may be attributed to fine-root activity. The flux rates of root respiration were 8.7 and 10.5 times as much as those of exudation on a root-length basis and a root-weight basis, respectively. In spite of the fact that flux rates of respiration and exudation varied enormously among the fine-root segments of the two Quercus species, exudation was in proportion to respiration. This result gives new insight into the fine-root C-allocation strategy and the belowground C dynamics. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

3D Electrical Resistivity Tomography and Mise-à-la-Masse Method as Tools for the Characterization of Vine Roots

NASA Astrophysics Data System (ADS)

Boaga, J.; Mary, B.; Peruzzo, L.; Schmutz, M.; Wu, Y.; Hubbard, S. S.; Cassiani, G.

2017-12-01

The interest on non-invasive geophysical monitoring of soil properties and root architecture is rapidly growing. Despite this, few case studies exist concerning vineyards, which are economically one of the leading sectors of agriculture. In this study, we integrate different geophysical methods in order to gain a better imaging of the vine root system, with the aim of quantifying root development, a key factor to understand roots-soil interaction and water balance. Our test site is a vineyard located in Bordeaux (France), where we adopted the Mise-a-la-Masse method (MALM) and micro-scale electrical resistivity tomography (ERT) on the same 3D electrode configuration. While ERT is a well-established technique to image changes in soil moisture content by root activity, MALM is a relatively new approach in this field of research. The idea is to inject current directly in the plant trunk and verify the resulting voltage distribution in the soil, as an effect of current distribution through the root system. In order to distinguish the root effect from other phenomena linked to the soil heterogeneities, we conducted and compared MALM measurements acquired through injecting current into the stem and into the soil near the stem. Moreover, the MALM data measured in the field were compared with numerical simulations to improve the confidence in the interpretation. Differences obtained between the stem and soil injection clearly validated the assumption that the whole root system is acting as a current pathway, thus highlighting the locations at depth where current is entering the soil from the fine roots. The simulation results indicated that the best fit is obtained through considering distributed sources with depth, reflecting a probable root zone area. The root location and volume estimated using this procedure are in agreement with vineyard experimental evidence. This work suggests the promising application of electrical methods to locate and monitor root systems. Further work is necessary to effectively integrate the geophysical and plant physiology information.

Phloem Girdling of Norway Spruce Alters Quantity and Quality of Wood Formation in Roots Particularly Under Drought

PubMed Central

Rainer-Lethaus, Gina; Oberhuber, Walter

2018-01-01

Carbon (C) availability plays an essential role in tree growth and wood formation. We evaluated the hypothesis that a decrease in C availability (i) triggers mobilization of C reserves in the coarse roots of Picea abies to maintain growth and (ii) causes modification of wood structure notably under drought. The 6-year-old saplings were subjected to two levels of soil moisture (watered versus drought conditions) and root C status was manipulated by physically blocking phloem transport in the stem at three girdling dates (GDs). Stem girdling was done before the onset of bud break [day of the year (doy) 77], during vigorous aboveground shoot and radial stem growth (GD doy 138), and after cessation of shoot growth (GD doy 190). The effect of blockage of C transport on root growth, root phenology, and wood anatomical traits [cell lumen diameter (CLD) and cell wall thickness (CWT)] in earlywood (EW) and latewood (LW) was determined. To evaluate changes in belowground C status caused by girdling, non-structural carbohydrates (soluble sugars and starch) in coarse roots were determined at the time of girdling and after the growing season. Although fine root mass significantly decreased in response to blockage of phloem C transport, the phenology of root elongation growth was not affected. Surprisingly, radial root growth and CLD of EW tracheids in coarse roots were strikingly increased in drought-stressed trees, when girdling occurred before bud break or during aboveground stem growth. In watered trees, the growth response to girdling was less distinct, but the CWT of EW significantly increased. Starch reserves in the roots of girdled trees significantly decreased in both soil moisture treatments and at all GDs. We conclude that (i) radial growth and wood development in coarse roots of P. abies saplings are not only dependent on current photosynthates, and (ii) blockage of phloem transport induces physiological changes that outweigh drought effects imposed on root cambial activity and cell differentiation. PMID:29636766

Adaptive shoot and root responses collectively enhance growth at optimum temperature and limited phosphorus supply of three herbaceous legume species.

PubMed

Suriyagoda, Lalith D B; Ryan, Megan H; Renton, Michael; Lambers, Hans

2012-10-01

Studies on the effects of sub- and/or supraoptimal temperatures on growth and phosphorus (P) nutrition of perennial herbaceous species at growth-limiting P availability are few, and the impacts of temperature on rhizosphere carboxylate dynamics are not known for any species. The effect of three day/night temperature regimes (low, 20/13 °C; medium, 27/20 °C; and high, 32/25 °C) on growth and P nutrition of Cullen cinereum, Kennedia nigricans and Lotus australis was determined. The highest temperature was optimal for growth of C. cinereum, while the lowest temperature was optimal for K. nigricans and L. australis. At optimum temperatures, the relative growth rate (RGR), root length, root length per leaf area, total P content, P productivity and water-use efficiency were higher for all species, and rhizosphere carboxylate content was higher for K. nigricans and L. australis. Cullen cinereum, with a slower RGR, had long (higher root length per leaf area) and thin roots to enhance P uptake by exploring a greater volume of soil at its optimum temperature, while K. nigricans and L. australis, with faster RGRs, had only long roots (higher root length per leaf area) as a morphological adaptation, but had a higher content of carboxylates in their rhizospheres at the optimum temperature. Irrespective of the species, the amount of P taken up by a plant was mainly determined by root length, rather than by P uptake rate per unit root surface area. Phosphorus productivity was correlated with RGR and plant biomass. All three species exhibited adaptive shoot and root traits to enhance growth at their optimum temperatures at growth-limiting P supply. The species with a slower RGR (i.e. C. cinereum) showed only morphological root adaptations, while K. nigricans and L. australis, with faster RGRs, had both morphological and physiological (i.e. root carboxylate dynamics) root adaptations.

Body surface area as a key determinant of aortic root and arch dimensions in a population-based study.

PubMed

Wang, Yan-Li; Wang, Qing-Ling; Wang, Liang; Wu, Ying-Biao; Wang, Zhi-Bin; Cameron, James; Liang, Yu-Lu

2013-02-01

The associations between the aortic dimensions (of the aortic sinus, aortic annulus and aortic arch) and physiological variables have not been established in the Chinese population. The present study examined the associations among physiological variables to determine the aortic root and arch dimensions echocardiographically. The diameters of the aortic sinus, annulus and arch were measured in 1,010 subjects via 2-D echocardiography with a 3.5-MHz transducer in a trans-thoracic position. The images of the aortic sinus and aortic annulus were obtained from a standard parasternal long-axis view. The maximum diameter of the valve orifice was measured at the end of systole. The aortic arch dimension was visualized in the long-axis using a suprasternal notch window and the maximum transverse diameter was measured. Epidata 3.0, Excel 2007 and SPSS version 17.0 were used to collect and analyze the data. A total of 1,010 subjects were enrolled. The mean age was 55.0±17.0 years (range of 18 to 90 years). The body surface area (BSA) was the best predictor of all the studied physiological variables and may be used to predict aortic sinus, annulus and arch dimensions independently (r=0.54, 0.37 and 0.39, respectively). Gender, blood pressure, age and BSA are significant predictors of the aortic dimensions. Of these, BSA was the best predictor.

Adaptive physiological response, carbon partitioning, and biomass production of Withania somnifera (L.) Dunal grown under elevated CO2 regimes.

PubMed

Sharma, Rupali; Singh, Hukum; Kaushik, Monica; Nautiyal, Raman; Singh, Ombir

2018-06-01

Winter cherry or Ashwagandha ( Withania somnifera ) is an important medicinal plant used in traditional and herbal medicine system. Yet, there is no information available on response of this plant to changing climatic conditions particularly elevated atmospheric CO 2 concentrations. Therefore, we conducted an experiment to examine the effect of elevated CO 2 concentrations (ECs) on Withania somnifera . The variations in traits of physiological adaptation, net primary productivity, carbon partitioning, morphology, and biomass in response to elevated CO 2 concentrations (ambient, 600 and 800 µmol mol -1 ) during one growth cycle were investigated within the open top chamber (OTC) facility in the foothill of the Himalayas, Dehardun, India. ECs significantly increased photosynthetic rate, transpiration rate, stomatal conductance, water use efficiency, soil respiration, net primary productivity and the carbon content of plant tissues (leaf, stem, and root), and soil carbon. Furthermore, ECs significantly enhanced biomass production (root and shoot), although declined night leaf respiration. Overall, it was summarized that photosynthesis, stomatal conductance, water use efficiency, leaf, and soil carbon and biomass increased under ECs rendering the physiological adaptation to the plant. Increased net primary productivity might facilitate mitigation effects by sequestering elevated levels of carbon dioxide. We advocate further studies to investigate the effects of ECs on the accumulation of secondary metabolites and health-promoting substances of this as well as other medicinal plants.

Aluminium tolerance and high phosphorus efficiency helps Stylosanthes better adapt to low-P acid soils.

PubMed

Du, Yu-Mei; Tian, Jiang; Liao, Hong; Bai, Chang-Jun; Yan, Xiao-Long; Liu, Guo-Dao

2009-06-01

Stylosanthes spp. (stylo) is one of the most important pasture legumes used in a wide range of agricultural systems on acid soils, where aluminium (Al) toxicity and phosphorus (P) deficiency are two major limiting factors for plant growth. However, physiological mechanisms of stylo adaptation to acid soils are not understood. Twelve stylo genotypes were surveyed under field conditions, followed by sand and nutrient solution culture experiments to investigate possible physiological mechanisms of stylo adaptation to low-P acid soils. Stylo genotypes varied substantially in growth and P uptake in low P conditions in the field. Three genotypes contrasting in P efficiency were selected for experiments in nutrient solution and sand culture to examine their Al tolerance and ability to utilize different P sources, including Ca-P, K-P, Al-P, Fe-P and phytate-P. Among the three tested genotypes, the P-efficient genotype 'TPRC2001-1' had higher Al tolerance than the P-inefficient genotype 'Fine-stem' as indicated by relative tap root length and haematoxylin staining. The three genotypes differed in their ability to utilize different P sources. The P-efficient genotype, 'TPRC2001-1', had superior ability to utilize phytate-P. The findings suggest that possible physiological mechanisms of stylo adaptation to low-P acid soils might involve superior ability of plant roots to tolerate Al toxicity and to utilize organic P and Al-P.

[Different responses of growth and root development of Schima superba provenance to the adjacent plant competition in different nutrient conditions].

PubMed

Yao, Jia Bao; Chu, Xiu Li; Zhou, Zhi Chun; Tong, Jian She; Wang, Hui; Yu, Jia Zhong

2017-04-18

Growth and root development of three Schima superba seedling provenances were influenced by adjacent plant competition in the homogeneous and heterogeneous nutrient environment, which revealed the reasons of S. superba competition differences in the different genotypes. The results indicated that, compared with homogeneous nutrient environment, all three S. superba provenances showed higher seedling height, more dry matter accumulation, and significant root proliferation in heterogeneous nutrient environment. Under heterogeneous nutrient environment, the seedlings of S. superba from Jian'ou of Fujian exhibited higher competitive advantage in growth than that of S. superba from Longquan of Zhejiang and Xinfeng of Jiangxi, especially standing out under mixed cultivation with seedlings of Cunninghamia lanceolata. Under mixed cultivation, the root growth parameters of S. superba such as root length, root surface area and volume increased by 20.4%-69.0% compared with the single plant, which enhanced the foraging ability and growth advantage. To some extent, however, the root development in Longquan of Zhejiang and Xinfeng of Jiangxi was suppressed when subjected to the pattern of mixed cultivation. Besides, the root growth and development of all three S. superba provenances were suppressed, which might be due to their root self-recognition in the pattern of mono cultivation. Therefore, the seedling growth in Jian'ou of Fujian decreased significantly, but seedling growth in Longquan of Zhejiang and Xinfeng of Jiangxi was not suppressed, even increased evidently, as their root physiological plasticity might play the crucial role in seedling growth. Hence the S. superba from Jian'ou of Fujian with high foraging efficiency and competition ability was suggested with the method of mixed forestation to improve the S. superba forest plantation productivity.

Immersed boundary-finite element model of fluid-structure interaction in the aortic root

NASA Astrophysics Data System (ADS)

Flamini, Vittoria; DeAnda, Abe; Griffith, Boyce E.

2016-04-01

It has long been recognized that aortic root elasticity helps to ensure efficient aortic valve closure, but our understanding of the functional importance of the elasticity and geometry of the aortic root continues to evolve as increasingly detailed in vivo imaging data become available. Herein, we describe a fluid-structure interaction model of the aortic root, including the aortic valve leaflets, the sinuses of Valsalva, the aortic annulus, and the sinotubular junction, that employs a version of Peskin's immersed boundary (IB) method with a finite element description of the structural elasticity. As in earlier work, we use a fiber-based model of the valve leaflets, but this study extends earlier IB models of the aortic root by employing an incompressible hyperelastic model of the mechanics of the sinuses and ascending aorta using a constitutive law fit to experimental data from human aortic root tissue. In vivo pressure loading is accounted for by a backward displacement method that determines the unloaded configuration of the root model. Our model yields realistic cardiac output at physiological pressures, with low transvalvular pressure differences during forward flow, minimal regurgitation during valve closure, and realistic pressure loads when the valve is closed during diastole. Further, results from high-resolution computations indicate that although the detailed leaflet and root kinematics show some grid sensitivity, our IB model of the aortic root nonetheless produces essentially grid-converged flow rates and pressures at practical grid spacings for the high Reynolds number flows of the aortic root. These results thereby clarify minimum grid resolutions required by such models when used as stand-alone models of the aortic valve as well as when used to provide models of the outflow valves in models of left-ventricular fluid dynamics.

Silicon alleviates Cd stress of wheat seedlings (Triticum turgidum L. cv. Claudio) grown in hydroponics.

PubMed

Rizwan, M; Meunier, J-D; Davidian, J-C; Pokrovsky, O S; Bovet, N; Keller, C

2016-01-01

We investigated the potential role of silicon in improving tolerance and decreasing cadmium (Cd) toxicity in durum wheat (Triticum turgidum L. durum) either through a reduced Cd uptake or exclusion/sequestration in non-metabolic tissues. For this, plants were grown in hydroponic conditions for 10 days either in presence or absence of 1 mM Si and for 11 additional days in various Cd concentrations (0, 0.5, 5.0 and 50 μM). After harvesting, morphological and physiological parameters as well as elemental concentrations were recorded. Cadmium caused reduction in growth parameters, photosynthetic pigments and mineral nutrient concentrations both in shoots and roots. Shoot and root contents of malate, citrate and aconitate increased, while contents of phosphate, nitrate and sulphate decreased with increasing Cd concentrations in plants. Addition of Si to the nutrient solution mitigated these adverse effects: Cd concentration in shoots decreased while concentration of Cd adsorbed at the root cell apoplasmic level increased together with Zn uptake by roots. Overall, total Cd uptake decreased in presence of Si. There was no co-localisation of Cd and Si either at the shoot or at the root levels. No Cd was detected in leaf phytoliths. In roots, Cd was mainly detected in the cortical parenchyma and Si at the endodermis level, while analysis of the outer thin root surface of the plants grown in the 50 μM Cd + 1 mM Si treatment highlighted non-homogeneous Cd and Si enrichments. These data strongly suggest the existence of a root localised protection mechanism consisting in armoring the root surface by Si- and Cd-bearing compounds and in limiting root-shoot translocation.

Electrical signaling, stomatal conductance, ABA and Ethylene content in avocado trees in response to root hypoxia

PubMed Central

Gurovich, Luis; Schaffer, Bruce; García, Nicolás; Iturriaga, Rodrigo

2009-01-01

Avocado (Persea americana Mill.) trees are among the most sensitive of fruit tree species to root hypoxia as a result of flooded or poorly drained soil. Similar to drought stress, an early physiological response to root hypoxia in avocado is a reduction of stomatal conductance. It has been previously determined in avocado trees that an extracellular electrical signal between the base of stem and leaves is produced and related to reductions in stomatal conductance in response to drought stress. The current study was designed to determine if changes in the extracellular electrical potential between the base of the stem and leaves in avocado trees could also be detected in response to short-term (min) or long-term (days) root hypoxia, and if these signals could be related to stomatal conductance (gs), root and leaf ABA and ACC concentrations, ethylene emission from leaves and leaf abscission. In contrast to previous observations for drought-stressed trees, short-term or long-term root hypoxia did not stimulate an electrical potential difference between the base of the stem and leaves. Short-term hypoxia did not result in a significant decrease in gs compared with plants in the control treatment, and no differences in ABA concentration were found between plants subjected to hypoxia and control plants. Long-term hypoxia in the root zone resulted in a significant decrease in gs, increased leaf ethylene and increased leaf abscission. The results indicate that for avocado trees exposed to root hypoxia, electrical signals do not appear to be the primary root-to-shoot communication mechanism involved in signaling for stomatal closure as a result of hypoxia in the root zone. PMID:19649181

Partial Root-Zone Drying of Olive (Olea europaea var. 'Chetoui') Induces Reduced Yield under Field Conditions

PubMed Central

Dbara, Soumaya; Haworth, Matthew; Emiliani, Giovani; Ben Mimoun, Mehdi; Gómez-Cadenas, Aurelio; Centritto, Mauro

2016-01-01

The productivity of olive trees in arid and semi-arid environments is closely linked to irrigation. It is necessary to improve the efficiency of irrigation techniques to optimise the amount of olive fruit produced in relation to the volume of water used. Partial root-zone drying (PRD) is a water saving irrigation technique that theoretically allows the production of a root-to-shoot signal that modifies the physiology of the above-ground parts of the plant; specifically reducing stomatal conductance (gs) and improving water use efficiency (WUE). Partial root-zone drying has been successfully applied under field conditions to woody and non-woody crops; yet the few previous trials with olive trees have produced contrasting results. Thirty year-old olive trees (Olea europaea ‘var. Chetoui’) in a Tunisian grove were exposed to four treatments from May to October for three-years: ‘control’ plants received 100% of the potential evapotranspirative demand (ETc) applied to the whole root-zone; ‘PRD100’ were supplied with an identical volume of water to the control plants alternated between halves of the root-zone every ten-days; ‘PRD50’ were given 50% of ETc to half of the root-system, and; ‘rain-fed’ plants received no supplementary irrigation. Allowing part of the root-zone to dry resulted in reduced vegetative growth and lower yield: PRD100 decreased yield by ~47% during productive years. During the less productive years of the alternate bearing cycle, irrigation had no effect on yield; this suggests that withholding of water during ‘off-years’ may enhance the effectiveness of irrigation over a two-year cycle. The amount and quality of oil within the olive fruit was unaffected by the irrigation treatment. Photosynthesis declined in the PRD50 and rain-fed trees due to greater diffusive limitations and reduced biochemical uptake of CO2. Stomatal conductance and the foliar concentration of abscisic acid (ABA) were not altered by PRD100 irrigation, which may indicate the absence of a hormonal root-to-shoot signal. Rain-fed and PRD50 treatments induced increased stem water potential and increased foliar concentrations of ABA, proline and soluble sugars. The stomata of the olive trees were relatively insensitive to super-ambient increases in [CO2] and higher [ABA]. These characteristics of ‘hydro-passive’ stomatal behaviour indicate that the ‘Chetoui’ variety of olive tree used in this study lacks the physiological responses required for the successful exploitation of PRD techniques to increase yield and water productivity. Alternative irrigation techniques such as partial deficit irrigation may be more suitable for ‘Chetoui’ olive production. PMID:27315081

Experimental identification of mechanisms controlling calcium isotopic fractionations by the vegetation.

NASA Astrophysics Data System (ADS)

Cobert, Florian; Schimtt, Anne-Désirée.; Bourgeade, Pascale; Stille, Peter; Chabaux, François; Badot, Pierre-Marie; Jaegler, Thomas

2010-05-01

This study aims to better understand the role of vegetation on the Ca cycle at the level of the critical zone of the Earth, in order to specify the mechanisms controlling the Ca absorption by plants at the rock/plant interface. To do this, we performed experiments using hydroponic plant cultures in a way that we could control the co-occuring geochemical and physiological process and determine the impact of the nutritive solution on the Ca cycle within plants. A dicotyledon and calcicole plant with rapid growth, the French bean (Phaseolus vulgaris L.), has been chosen to have access to one complete growth cycle. Several experiments have been conducted with two Ca concentrations, 6 (L) and 60 (H) ppm and two pH values (4 and 6) in the nutritive solution, for which the Ca concentration was maintained constant, so its Ca content is considered as infinite. A second experiment (non infinite L6) allowed Ca depletion in the solution through time; therefore, response effects on the Ca isotopic signatures in the plant organs and in the nutritive solution were observed. We determined Ca concentrations and isotopic ratios in the nutritive solution and in different organs (main roots, secondary roots, old and young stems, old and young leaves and fruits) at two different growth stages (10 days and 6 weeks). Preliminary results show that: (1) the roots (main and secondary) were enriched in the light isotope (40Ca) compared to the nutritive solution, and leaves were enriched in the heavy isotope (44Ca) compared to stems. These results are in accord with previously published field studies (Wigand et al., 2005; Page et al., 2008; Cenki-Tok et al., 2009; Holmden and Bélanger, 2010). Leaves and secondary roots were however enriched in the heavy isotope (44Ca) compared to bean pods, stems and main roots. These results could be related to kinetic fractionation processes occurring either during the Ca root uptake, or during the Ca transport within the plant, or physiological mechanisms occurring first at the level of secondary roots, and second at the level of leaves. (2) No Ca isotope difference was observed neither between old and young organs, (except for H6 leaves), nor between the two growth stages (except for H6 roots). This suggest that the mechanisms controlling isotopic fractionations of Ca within common beans do not vary during growth, and that the nutrients stored in the cotyledons have only a minor effect on the Ca isotope fractionations of plants harvested after 10 days. (3) Strongest Ca isotope fractionations were observed at the nutritive solution/root interface. This implies that the mechanisms of light isotope enrichments in the plant are mainly due to transport processes taking place at this interface. (4) The non infinite L6 nutritive solution became enriched in 44Ca during the experiment compared to the infinite L6 nutritive solution and all the other solutions (L4, H4, and H6). This enrichment can be explained by Rayleigh fractionation or isotopic equilibrium. (5) Bean organs, from L4 and non infinite L6 experiment conditions, were enriched in 44Ca compared to stems and roots cultivated under H4, H6 and infinite L6 conditions. This might be due to the limited Ca in the nutritive solutions that cause smallest Ca isotope fractionations in the bean organs. All these results show that there is no simple correlation between Ca isotopic variations, Ca content and pH of the nutrient solution, and that physiological effects have also to be involved. They confirm the potential of the Ca isotopic system for tracing biological fractionations in natural ecosystems.

Amyloplast Distribution Directs a Root Gravitropic Reaction

NASA Astrophysics Data System (ADS)

Kordyum, Elizabeth

Immobile higher plants are oriented in the gravitational field due to gravitropim that is a physiological growth reaction and consists of three phases: reception of a gravitational signal by statocytes, its transduction to the elongation zone, and finally the organ bending. As it is known, roots are characterized with positive gravitropism, i. e. they grow in the direction of a gravitational vector, stems - with negative gravitropism, i. e. they grow in the direction opposite to a gravitational vector. According to the Nemec’s and Haberlandt’s starch-statolith hypothesis, amyloplasts in diameter of 1.5 - 3 μ in average, which appear to act as gravity sensors and fulfill a statolythic function in the specialized graviperceptive cells - statocytes, sediment in the direction of a gravitational vector in the distal part of a cell, while a nucleus is in the proximal one. There are reasonable data that confirm the amyloplasts-statoliths participation in gravity perception: 1) correlation between the statoliths localization and the site of gravity sensing, 2) significant redistribution (sedimentation) of amyloplasts in statocytes under gravistimulation in comparison with other cell organelles, 3) root decreased ability to react on gravity under starch removal from amyloplasts, 4) starchless Arabidopsis thaliana mutants are agravitropic, 5) amyloplasts-statoliths do not sediment in the absence of the gravitational vector and are in different parts or more concentrated in the center of statocytes. Plant tropisms have been intensively studied for many decades and continue to be investigated. Nevertheless, the mechanisms by which plants do so is still not clearly explained and many questions on gravisensing and graviresponse remain unanswered. Even accepted hypotheses are now being questioned and recent data are critically evaluated. Although the available data show the Ca2+ and cytoskeleton participation in graviperception and signal transduction, the clear evidence with regard to the participation of calcium ions and cytoskeletal elements in these processes is therefore substantial but still circumstantial and requires new experimental data. Using a new model - weak combined magnetic fields (CMFs), which elicit a variety of responses in plants, growth rate and fresh weight, seed germination, Ca2+ concentration, membrane permeability, with a frequency resonance to cyclotron frequency of calcium ions, we firstly showed that a root positive gravitropic reaction changes on a negative one. In this case, the paradoxical displacement of amylopasts-statoliths to the upper longitudinal cell wall of statocytes occurred in the direction opposite to a gravitational vector. Displacement of amyloplasts, which contain the abundance of free Ca2+ in the stroma, was accompanied with Ca2+ redistribution in the same direction in the cytosol and increasing around amyloplasts in comparison with the state magnetic field. In the elongation zone, calcium ions accumulated in the upper site of a gravistimulated root unlike a positive gravitropic reaction, and a root is bending in the same direction in which amyloplasts are displacing. It seems that a root gravitropic reaction, if it began, occurs by an usual physiological way resulting in root bending with an opposite sign. It is of a special interest that a root is bending to the same direction with displacing of amyloplasts: in positive gravitropism - downwards, in negative gravitropism - upwards. Peculiarities of calcium ion redistribution in statocytes under gravistimulation in such combined magnetic field are a new additional evidence of a Ca2+ ion significant role in gravitropism. Thus, our data support the starch-statolith hypothesis but also pose the question as to which forces displace amyloplasts against the gravity vector? We hope that these data will stimulate new research to better understand the mechanisms of plant graviperception and graviresponse. Gravistimulation of a root in the CMF with the frequency resonance to the cyclotron frequency of Ca2+ ions is an effective model for future research of the mechanism of plant gravitropism, including a Ca2+ role in plant physiological growth reactions.

Stars and Symbiosis: MicroRNA- and MicroRNA*-Mediated Transcript Cleavage Involved in Arbuscular Mycorrhizal Symbiosis1[W][OA

PubMed Central

Devers, Emanuel A.; Branscheid, Anja; May, Patrick; Krajinski, Franziska

2011-01-01

The majority of plants are able to form the arbuscular mycorrhizal (AM) symbiosis in association with AM fungi. During symbiosis development, plant cells undergo a complex reprogramming resulting in profound morphological and physiological changes. MicroRNAs (miRNAs) are important components of the regulatory network of plant cells. To unravel the impact of miRNAs and miRNA-mediated mRNA cleavage on root cell reprogramming during AM symbiosis, we carried out high-throughput (Illumina) sequencing of small RNAs and degradome tags of Medicago truncatula roots. This led to the annotation of 243 novel miRNAs. An increased accumulation of several novel and conserved miRNAs in mycorrhizal roots suggest a role of these miRNAs during AM symbiosis. The degradome analysis led to the identification of 185 root transcripts as mature miRNA and also miRNA*-mediated mRNA cleavage targets. Several of the identified miRNA targets are known to be involved in root symbioses. In summary, the increased accumulation of specific miRNAs and the miRNA-mediated cleavage of symbiosis-relevant genes indicate that miRNAs are an important part of the regulatory network leading to symbiosis development. PMID:21571671

The tonoplast intrinsic aquaporin (TIP) subfamily of Eucalyptus grandis: Characterization of EgTIP2, a root-specific and osmotic stress-responsive gene.

PubMed

Rodrigues, Marcela I; Bravo, Juliana P; Sassaki, Flávio T; Severino, Fábio E; Maia, Ivan G

2013-12-01

Aquaporins have important roles in various physiological processes in plants, including growth, development and adaptation to stress. In this study, a gene encoding a root-specific tonoplast intrinsic aquaporin (TIP) from Eucalyptus grandis (named EgTIP2) was investigated. The root-specific expression of EgTIP2 was validated over a panel of five eucalyptus organ/tissues. In eucalyptus roots, EgTIP2 expression was significantly induced by osmotic stress imposed by PEG treatment. Histochemical analysis of transgenic tobacco lines (Nicotiana tabacum SR1) harboring an EgTIP2 promoter:GUS reporter cassette revealed major GUS staining in the vasculature and in root tips. Consistent with its osmotic-stress inducible expression in eucalyptus, EgTIP2 promoter activity was up-regulated by mannitol treatment, but was down-regulated by abscisic acid. Taken together, these results suggest that EgTIP2 might be involved in eucalyptus response to drought. Additional searches in the eucalyptus genome revealed the presence of four additional putative TIP coding genes, which could be individually assigned to the classical TIP1-5 groups. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Mechanisms for the increase in phosphorus uptake of waterlogged plants: soil phosphorus availability, root morphology and uptake kinetics.

PubMed

Rubio, Gerardo; Oesterheld, Martín; Alvarez, Carina R; Lavado, Raúl S

1997-10-01

Waterlogging frequently reduces plant biomass allocation to roots. This response may result in a variety of alterations in mineral nutrition, which range from a proportional lowering of whole-plant nutrient concentration as a result of unchanged uptake per unit of root biomass, to a maintenance of nutrient concentration by means of an increase in uptake per unit of root biomass. The first objective of this paper was to test these two alternative hypothetical responses. In a pot experiment, we evaluated how plant P concentration of Paspalum dilatatum, (a waterlogging-tolerant grass from the Flooding Pampa, Argentina) was affected by waterlogging and P supply and how this related to changes in root-shoot ratio. Under both soil P levels waterlogging reduced root-shoot ratios, but did not reduce P concentration. Thus, uptake of P per unit of root biomass increased under waterlogging. Our second objective was to test three non-exclusive hypotheses about potential mechanisms for this increase in P uptake. We hypothesized that the greater P uptake per unit of root biomass was a consequence of: (1) an increase in soil P availability induced by waterlogging; (2) a change in root morphology, and/or (3) an increase in the intrinsic uptake capacity of each unit of root biomass. To test these hypotheses we evaluated (1) changes in P availability induced by waterlogging; (2) specific root length of waterlogged and control plants, and (3) P uptake kinetics in excised roots from waterlogged and control plants. The results supported the three hypotheses. Soil P avail-ability was higher during waterlogging periods, roots of waterlogged plants showed a morphology more favorable to nutrient uptake (finer roots) and these roots showed a higher physiological capacity to absorb P. The results suggest that both soil and plant mechanisms contributed to compensate, in terms of P nutrition, for the reduction in allocation to root growth. The rapid transformation of the P uptake system is likely an advantage for plants inhabiting frequently flooded environments with low P fertility, like the Flooding Pampa. This advantage would be one of the reasons for the increased relative abundance of P. dilatatum in the community after waterlogging periods.

[Adaptive adjustment of rhizome and root system on morphology, biomass and nutrient in Phyllostachys rivalis under long-term waterlogged condition].

PubMed

Liu, Yu-fang; Chen, Shuang-lin; Li Ying-chun; Guo, Zi-wu; Li, Ying-chun; Yang, Qing-ping

2015-12-01

The research was to approach the growth strategy of rhizome and roots based on the morphology, biomass and nutrient in Phyllostachys rivalis under long-term waterlogged conditions, and provided a theoretical basis for its application for vegetation restoration in wetland and water-level fluctuation belts. The morphological characteristics, physiological and biochemical indexes of annual bamboo rhizome and roots were investigated with an experiment using individually potted P. rivalis which was treated by artificial water-logging for 3, 6, and 12 months. Accordingly the morphological characteristics, biomass allocation, nutrient absorption and balance in rhizome and roots of P. rivalis were analyzed. The results showed that there was no obvious impact of long-term water-logging on the length and diameter of rhizomes, diameter of roots in P. rivalis. The morphological characteristics of rhizome had been less affected generally under water-logging for 3 months. And less rhizomes were submerged, while the growth of roots was inhibited to some extent. Furthermore, with waterlogging time extended, submerged roots and rhizomes grew abundantly, and the roots and rhizomes in soil were promoted. Moreover for ratios of rhizome biomass in soil and water, there were no obvious variations, the same for the root biomass in soil to total biomass. The ratio of root biomass in water to total biomass and the ratio of root biomass in water to root biomass in soil both increased significantly. The results indicated that P. rivalis could adapt to waterlogged conditions gradually through growth regulation and reasonable biomass distribution. However, the activity of rhizome roots in soil decreased and the nutrient absorption was inhibited by long-term water-logging, although it had no effect on stoichiometric ratios of root nutrient in soil. The activity of rhizome root in water increased and the stoichiometric ratios adjusted adaptively to waterlogged conditions, the ratio of N/P increased, while N/K and P/K decreased, which implied that roots in water absorbed oxygen and nutrients could help P. rivalis adapt to long-term waterlogged environment effectively.

Seedling establishment and physiological responses to temporal and spatial soil moisture changes

Treesearch

Jeremy Pinto; John D. Marshall; Kas Dumroese; Anthony S. Davis; Douglas R. Cobos

2016-01-01

In many forests of the world, the summer season (temporal element) brings drought conditions causing low soil moisture in the upper soil profile (spatial element) - a potentially large barrier to seedling establishment. We evaluated the relationship between initial seedling root depth, temporal and spatial changes in soil moisture during drought after...

Isolation and Structural Studies of Mitochondria from Pea Roots.

PubMed

Vishwakarma, Abhaypratap; Gupta, Kapuganti Jagadis

2017-01-01

For structural and respiratory studies, isolation of intact and active mitochondria is essential. Here, we describe an isolation method which gave good yield and intact mitochondria from 2-week-old pea (Pisum sativum) roots grown hydroponically under standard growth conditions. We used Percoll gradient centrifugation for this isolation procedure. The yield of purified mitochondria was 50 μg/g FW. Isolated mitochondria maintained their structure which was observed by using MitoTracker green in confocal microscope and scanning electron microscopy (SEM). Intact mitochondria are clearly visible in SCM images. Taken together this isolation method can be used for physiological and microscopic studies on mitochondria.

Differential flank growth

NASA Astrophysics Data System (ADS)

Zieschang, H. E.; Sievers, A.

1994-08-01

With the mathematical basis for the precise analysis of developmental processes in plants, the patterns of growth in phototropic and gravitropic responses have become better understood. A detailed temporal and spatial quantification of a growth process is an important tool for evaluating hypotheses about the underlying physiological mechanisms. Studies of growth rates and curvature show that the original Cholodny-Went hypothesis cannot explain the complex growth patterns during tropic responses of shoots and roots. In addition, regulating factors other than the lateral redistribution of hormones must be taken into account. Electrophysiological studies on roots led to a modification of the Cholodny-Went hypothesis in that redistributions of bioelectrical activities are observed.

Species and population variation to salinity stress in Panicum hemitomon, Spartina patens, and Spartina alterniflora: Morphological and physiological constraints

USGS Publications Warehouse

Hester, M.W.; Mendelssohn, I.A.; McKee, K.L.

2001-01-01

Panicum hemitomon, Spartina patens, and Spartina alterniflora are wide-spread dominant grasses of fresh, brackish, and salt marsh plant communities, respectively. Our previous research identified significant intraspecific variation in salt tolerance and morphology among populations within each species. In this study our objectives were to determine shorter-term physiological/biochemical responses to salinity stress and identify potential indicators of salt tolerance, with the ultimate goal of discerning similarities and differences in the mechanisms of salinity stress resistance. We subjected a subset of six populations within each species, ranging from high to low salt tolerance, to sublethal salinity levels (4, 20, and 30 ppt, respectively, for species) and monitored physiological and growth responses after 1 week (early harvest) and 5 weeks (late harvest). In all three species sublethal salinity levels generally resulted in significantly reduced net CO2 assimilation, leaf expansion, midday leaf xylem pressure, water use efficiency, and live and total biomass; and significantly increased leaf Na+/K+ ratio, leaf proline, leaf glycine betaine, leaf sucrose, root-to-shoot ratio, and dead:total aboveground biomass ratio. All three species displayed significant population (intraspecific) variation in net CO2 assimilation, leaf expansion, water use efficiency, midday leaf xylem pressure, leaf proline, leaf glycine betaine (except Panicum, where it could not be accurately determined), leaf Na+/K+ ratio, leaf sucrose, total plant biomass, dead:total aboveground biomass ratio, and root-to-shoot ratio. General indicators of salt tolerance (regardless of species) included high net CO2 assimilation rates and water use efficiencies, and low ratios of root-to-shoot and dead:total aboveground biomass. Factor analysis and a-priori linear contrasts revealed some unique differences between species in terms of the relative importance of morphology and physiology in explaining intraspecific variation in salt tolerance. Plant morphology (size attributes) were strongly associated with salt tolerance in P. hemitomon, weakly associated with salt tolerance in S. patens, and not associated with salt tolerance in S. alterniflora. Highly salt-tolerant populations of Spartina alterniflora displayed the greatest ion selectivity (lower leaf Na+/K+ ratios), which was not displayed by the other two species. These results suggest that plant size attributes can be very important in explaining population differences in salt tolerance in glycophytes, but may be independent of salt tolerance in halophytes, which have specialized physiological (and/or anatomical) adaptations that can confer salinity stress resistance through mechanisms such as selective ion exclusion and secretion. ?? 2001 Elsevier Science B.V. All rights reserved.

Ethylene Inhibits Root Elongation during Alkaline Stress through AUXIN1 and Associated Changes in Auxin Accumulation.

PubMed

Li, Juan; Xu, Heng-Hao; Liu, Wen-Cheng; Zhang, Xiao-Wei; Lu, Ying-Tang

2015-08-01

Soil alkalinity causes major reductions in yield and quality of crops worldwide. The plant root is the first organ sensing soil alkalinity, which results in shorter primary roots. However, the mechanism underlying alkaline stress-mediated inhibition of root elongation remains to be further elucidated. Here, we report that alkaline conditions inhibit primary root elongation of Arabidopsis (Arabidopsis thaliana) seedlings by reducing cell division potential in the meristem zones and that ethylene signaling affects this process. The ethylene perception antagonist silver (Ag(+)) alleviated the inhibition of root elongation by alkaline stress. Moreover, the ethylene signaling mutants ethylene response1-3 (etr1-3), ethylene insensitive2 (ein2), and ein3-1 showed less reduction in root length under alkaline conditions, indicating a reduced sensitivity to alkalinity. Ethylene biosynthesis also was found to play a role in alkaline stress-mediated root inhibition; the ethylene overproducer1-1 mutant, which overproduces ethylene because of increased stability of 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID SYNTHASE5, was hypersensitive to alkaline stress. In addition, the ethylene biosynthesis inhibitor cobalt (Co(2+)) suppressed alkaline stress-mediated inhibition of root elongation. We further found that alkaline stress caused an increase in auxin levels by promoting expression of auxin biosynthesis-related genes, but the increase in auxin levels was reduced in the roots of the etr1-3 and ein3-1 mutants and in Ag(+)/Co(2+)-treated wild-type plants. Additional genetic and physiological data showed that AUXIN1 (AUX1) was involved in alkaline stress-mediated inhibition of root elongation. Taken together, our results reveal that ethylene modulates alkaline stress-mediated inhibition of root growth by increasing auxin accumulation by stimulating the expression of AUX1 and auxin biosynthesis-related genes. © 2015 American Society of Plant Biologists. All Rights Reserved.

Root Damage under Alkaline Stress Is Associated with Reactive Oxygen Species Accumulation in Rice (Oryza sativa L.)

PubMed Central

Zhang, Hui; Liu, Xiao-Long; Zhang, Rui-Xue; Yuan, Hai-Yan; Wang, Ming-Ming; Yang, Hao-Yu; Ma, Hong-Yuan; Liu, Duo; Jiang, Chang-Jie; Liang, Zheng-Wei

2017-01-01

Alkaline stress (high pH) severely damages root cells, and consequently, inhibits rice (Oryza sativa L.) seedling growth. In this study, we demonstrate the accumulation of reactive oxygen species (ROS) in root cells under alkaline stress. Seedlings of two rice cultivars with different alkaline tolerances, ‘Dongdao-4’ (moderately alkaline-tolerant) and ‘Jiudao-51’ (alkaline-sensitive), were subjected to alkaline stress simulated by 15 mM sodium carbonate (Na2CO3). Alkaline stress greatly reduced seedling survival rate, shoot and root growth, and root vigor. Moreover, severe root cell damage was observed under alkaline stress, as shown by increased membrane injury, malondialdehyde accumulation, and Evan’s Blue staining. The expression of the cell death-related genes OsKOD1, OsHsr203j, OsCP1, and OsNAC4 was consistently upregulated, while that of a cell death-suppressor gene, OsBI1, was downregulated. Analysis of the ROS contents revealed that alkaline stress induced a marked accumulation of superoxide anions (O2•-) and hydrogen peroxide (H2O2) in rice roots. The application of procyanidins (a potent antioxidant) to rice seedlings 24 h prior to alkaline treatment significantly alleviated alkalinity-induced root damage and promoted seedling growth inhibition, which were concomitant with reduced ROS accumulation. These results suggest that root cell damage, and consequently growth inhibition, of rice seedlings under alkaline stress is closely associated with ROS accumulation. The antioxidant activity of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase increased under alkaline stress in the roots, probably in response to the cellular damage induced by oxidative stress. However, this response mechanism may be overwhelmed by the excess ROS accumulation observed under stress, resulting in oxidative damage to root cells. Our findings provide physiological insights into the molecular mechanisms of alkalinity-induced damage to root cells, and will contribute to the improvement of alkaline stress tolerance in rice plants. PMID:28943882

Root Damage under Alkaline Stress Is Associated with Reactive Oxygen Species Accumulation in Rice (Oryza sativa L.).

PubMed

Zhang, Hui; Liu, Xiao-Long; Zhang, Rui-Xue; Yuan, Hai-Yan; Wang, Ming-Ming; Yang, Hao-Yu; Ma, Hong-Yuan; Liu, Duo; Jiang, Chang-Jie; Liang, Zheng-Wei

2017-01-01

Alkaline stress (high pH) severely damages root cells, and consequently, inhibits rice ( Oryza sativa L.) seedling growth. In this study, we demonstrate the accumulation of reactive oxygen species (ROS) in root cells under alkaline stress. Seedlings of two rice cultivars with different alkaline tolerances, 'Dongdao-4' (moderately alkaline-tolerant) and 'Jiudao-51' (alkaline-sensitive), were subjected to alkaline stress simulated by 15 mM sodium carbonate (Na 2 CO 3 ). Alkaline stress greatly reduced seedling survival rate, shoot and root growth, and root vigor. Moreover, severe root cell damage was observed under alkaline stress, as shown by increased membrane injury, malondialdehyde accumulation, and Evan's Blue staining. The expression of the cell death-related genes OsKOD1 , OsHsr203j , OsCP1 , and OsNAC4 was consistently upregulated, while that of a cell death-suppressor gene, OsBI1 , was downregulated. Analysis of the ROS contents revealed that alkaline stress induced a marked accumulation of superoxide anions ([Formula: see text]) and hydrogen peroxide (H 2 O 2 ) in rice roots. The application of procyanidins (a potent antioxidant) to rice seedlings 24 h prior to alkaline treatment significantly alleviated alkalinity-induced root damage and promoted seedling growth inhibition, which were concomitant with reduced ROS accumulation. These results suggest that root cell damage, and consequently growth inhibition, of rice seedlings under alkaline stress is closely associated with ROS accumulation. The antioxidant activity of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase increased under alkaline stress in the roots, probably in response to the cellular damage induced by oxidative stress. However, this response mechanism may be overwhelmed by the excess ROS accumulation observed under stress, resulting in oxidative damage to root cells. Our findings provide physiological insights into the molecular mechanisms of alkalinity-induced damage to root cells, and will contribute to the improvement of alkaline stress tolerance in rice plants.

A novel-type phosphatidylinositol phosphate-interactive, Ca-binding protein PCaP1 in Arabidopsis thaliana: stable association with plasma membrane and partial involvement in stomata closure.

PubMed

Nagata, Chisako; Miwa, Chika; Tanaka, Natsuki; Kato, Mariko; Suito, Momoe; Tsuchihira, Ayako; Sato, Yori; Segami, Shoji; Maeshima, Masayoshi

2016-05-01

The Ca(2+)-binding protein-1 (PCaP1) of Arabidopsis thaliana is a new type protein that binds to phosphatidylinositol phosphates and Ca(2+)-calmodulin complex as well as free Ca(2+). Although biochemical properties, such as binding to ligands and N-myristoylation, have been revealed, the intracellular localization, tissue and cell specificity, integrity of membrane association and physiological roles of PCaP1 are unknown. We investigated the tissue and intracellular distribution of PCaP1 by using transgenic lines expressing PCaP1 linked with a green fluorescence protein (GFP) at the carboxyl terminus of PCaP1. GFP fluorescence was obviously detected in most tissues including root, stem, leaf and flower. In these tissues, PCaP1-GFP signal was observed predominantly in the plasma membrane even under physiological stress conditions but not in other organelles. The fluorescence was detected in the cytosol when the 25-residue N-terminal sequence was deleted from PCaP1 indicating essential contribution of N-myristoylation to the plasma membrane anchoring. Fluorescence intensity of PCaP1-GFP in roots was slightly decreased in seedlings grown in medium supplemented with high concentrations of iron for 1 week and increased in those grown with copper. In stomatal guard cells, PCaP1-GFP was strictly, specifically localized to the plasma membrane at the epidermal-cell side but not at the pore side. A T-DNA insertion mutant line of PCaP1 did not show marked phenotype in a life cycle except for well growth under high CO2 conditions. However, stomata of the mutant line did not close entirely even in high osmolarity, which usually induces stomata closure. These results suggest that PCaP1 is involved in the stomatal movement, especially closure process, in leaves and response to excessive copper in root and leaf as a mineral nutrient as a physiological role.

Drought-Up-Regulated TaNAC69-1 is a Transcriptional Repressor of TaSHY2 and TaIAA7, and Enhances Root Length and Biomass in Wheat.

PubMed

Chen, Dandan; Richardson, Terese; Chai, Shoucheng; Lynne McIntyre, C; Rae, Anne L; Xue, Gang-Ping

2016-10-01

A well-known physiological adaptation process of plants encountering drying soil is to achieve water balance by reducing shoot growth and maintaining or promoting root elongation, but little is known about the molecular basis of this process. This study investigated the role of a drought-up-regulated Triticum aestivum NAC69-1 (TaNAC69-1) in the modulation of root growth in wheat. TaNAC69-1 was predominantly expressed in wheat roots at the early vegetative stage. Overexpression of TaNAC69-1 in wheat roots using OsRSP3 (essentially root-specific) and OsPIP2;3 (root-predominant) promoters resulted in enhanced primary seminal root length and a marked increase in maturity root biomass. Competitive growth analysis under water-limited conditions showed that OsRSP3 promoter-driven TaNAC69-1 transgenic lines produced 32% and 35% more above-ground biomass and grains than wild-type plants, respectively. TaNAC69-1 overexpression in the roots down-regulated the expression of TaSHY2 and TaIAA7, which are from the auxin/IAA (Aux/IAA) transcriptional repressor gene family and are the homologs of negative root growth regulators SHY2/IAA3 and IAA7 in Arabidopsis. The expression of TaSHY2 and TaIAA7 in roots was down-regulated by drought stress and up-regulated by cytokinin treatment, which inhibited root growth. DNA binding and transient expression analyses revealed that TaNAC69-1 bound to the promoters of TaSHY2 and TaIAA7, acted as a transcriptional repressor and repressed the expression of reporter genes driven by the TaSHY2 or TaIAA7 promoter. These data suggest that TaNAC69-1 is a transcriptional repressor of TaSHY2 and TaIAA7 homologous to Arabidopsis negative root growth regulators and is likely to be involved in promoting root elongation in drying soil. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

N-fertilization has different effects on the growth, carbon and nitrogen physiology, and wood properties of slow- and fast-growing Populus species

PubMed Central

Luo, Zhi-Bin

2012-01-01

To investigate how N-fertilization affects the growth, carbon and nitrogen (N) physiology, and wood properties of poplars with contrasting growth characteristics, slow-growing (Populus popularis, Pp) and fast-growing (P. alba×P. glandulosa, Pg) poplar saplings were exposed to different N levels. Above-ground biomass, leaf area, photosynthetic rates (A), instantaneous photosynthetic nitrogen use efficiency (PNUE i), chlorophyll and foliar sugar concentrations were higher in Pg than in Pp. Foliar nitrate reductase (NR) activities and root glutamate synthase (GOGAT) activities were higher in Pg than in Pp as were the N amount and NUE of new shoots. Lignin contents and calorific values of Pg wood were less than that of Pp wood. N-fertilization reduced root biomass of Pg more than of Pp, but increased leaf biomass, leaf area, A, and PNUEi of Pg more than of Pp. Among 13 genes involved in the transport of ammonium or nitrate or in N assimilation, transcripts showed more pronounced changes to N-fertilization in Pg than in Pp. Increases in NR activities and N contents due to N-fertilization were larger in Pg than in Pp. In both species, N-fertilization resulted in lower calorific values as well as shorter and wider vessel elements/fibres. These results suggest that growth, carbon and N physiology, and wood properties are more sensitive to increasing N availability in fast-growing poplars than in slow-growing ones, which is probably due to prioritized resource allocation to the leaves and accelerated N physiological processes in fast-growing poplars under higher N levels. PMID:23028021

N-fertilization has different effects on the growth, carbon and nitrogen physiology, and wood properties of slow- and fast-growing Populus species.

PubMed

Li, Hong; Li, Mengchun; Luo, Jie; Cao, Xu; Qu, Long; Gai, Ying; Jiang, Xiangning; Liu, Tongxian; Bai, Hua; Janz, Dennis; Polle, Andrea; Peng, Changhui; Luo, Zhi-Bin

2012-10-01

To investigate how N-fertilization affects the growth, carbon and nitrogen (N) physiology, and wood properties of poplars with contrasting growth characteristics, slow-growing (Populus popularis, Pp) and fast-growing (P. alba×P. glandulosa, Pg) poplar saplings were exposed to different N levels. Above-ground biomass, leaf area, photosynthetic rates (A), instantaneous photosynthetic nitrogen use efficiency (PNUE (i)), chlorophyll and foliar sugar concentrations were higher in Pg than in Pp. Foliar nitrate reductase (NR) activities and root glutamate synthase (GOGAT) activities were higher in Pg than in Pp as were the N amount and NUE of new shoots. Lignin contents and calorific values of Pg wood were less than that of Pp wood. N-fertilization reduced root biomass of Pg more than of Pp, but increased leaf biomass, leaf area, A, and PNUE(i) of Pg more than of Pp. Among 13 genes involved in the transport of ammonium or nitrate or in N assimilation, transcripts showed more pronounced changes to N-fertilization in Pg than in Pp. Increases in NR activities and N contents due to N-fertilization were larger in Pg than in Pp. In both species, N-fertilization resulted in lower calorific values as well as shorter and wider vessel elements/fibres. These results suggest that growth, carbon and N physiology, and wood properties are more sensitive to increasing N availability in fast-growing poplars than in slow-growing ones, which is probably due to prioritized resource allocation to the leaves and accelerated N physiological processes in fast-growing poplars under higher N levels.

Physiological differences between root suckers and saplings enlarge the regeneration niche in Eucryphia cordifolia Cav.

PubMed

Escandón, Antonio B; Rojas, Roke; Morales, Loreto V; Corcuera, Luis J; Coopman, Rafael E; Paula, Susana

2018-01-01

Many clonal plants produce vegetative recruits that remain connected to the parent plant. Such connections permit resource sharing among ramets, explaining the high survival rates of vegetative recruits during establishment under suboptimal conditions for sexual regeneration. We propose that differences in the regeneration niches of sexual and vegetative recruits reflect different physiological adjustments caused by parental supply of resources to the ramets. We conducted ecophysiological measurements in saplings and root suckers of Eucryphia cordifolia Cav., a tree species of the temperate rainforest of southern South America. We compared the following traits of saplings and suckers: gas exchange at the leaf level, crown architecture, daily crown carbon balance, biomass allocation to above-ground tissues (leaf-to-stem mass ratio, leaf mass area and leaf area ratio), xylem anatomy traits (lumen vessel fraction, vessel density and size) and stem ring width. We also correlated the growth rates of saplings and suckers with relevant environmental data (light and climate). Saplings showed morphological, architectural and physiological traits that enhance daily crown carbon balance and increase water-use efficiency, in order to supply their growth demands while minimizing water loss per unit of carbon gained. The radial growth of saplings diminished under dry conditions, which suggests a strong stomatal sensitivity to water availability. Suckers have low stomatal conductance, likely because the carbon supplied by the parent plant diminishes the necessity of high rates of photosynthesis. The low responsiveness of sucker growth to temporal changes in water availability also supports the existence of parental supply. The physiological differences between sexual and vegetative recruits satisfactorily explain the ecological niche of E. cordifolia, with saplings restricted to more closed and humid sites. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Pachyrhizus ahipa (Wedd.) Parodi roots and flour: Biochemical and functional characteristics.

PubMed

Doporto, María C; Mugridge, Alicia; García, María A; Viña, Sonia Z

2011-06-15

Ahipa roots' chemical composition and physiological parameters were characterised; ahipa flour preparation procedures were selected and the chemical composition and functional properties of these products were studied. Ahipa roots and flour can be considered alternative food sources of gluten-free starch, with a considerable contribution of protein, fibre and minerals, such as potassium, calcium and iron. The grating process for ahipa flour production required a pressing step (AFGP) and the recovery of the starch leached. The slicing procedure (AFS) was simpler and the resulting product showed higher contents of potassium, magnesium, calcium and protein than did AFGP, which showed lower sodium and higher acid detergent fibre contents, together with lower gelatinisation temperature. Both flours differed in terms of α-amylase activity and swelling power, characteristics that may condition their specific applications, such as the incorporation of these flours as gluten-free functional food ingredients. Copyright © 2010 Elsevier Ltd. All rights reserved.

Toward better understanding of postharvest deterioration: biochemical changes in stored cassava (Manihot esculenta Crantz) roots.

PubMed

Uarrota, Virgílio Gavicho; Nunes, Eduardo da Costa; Peruch, Luiz Augusto Martins; Neubert, Enilto de Oliveira; Coelho, Bianca; Moresco, Rodolfo; Domínguez, Moralba Garcia; Sánchez, Teresa; Meléndez, Jorge Luis Luna; Dufour, Dominique; Ceballos, Hernan; Becerra Lopez-Lavalle, Luis Augusto; Hershey, Clair; Rocha, Miguel; Maraschin, Marcelo

2016-05-01

Food losses can occur during production, postharvest, and processing stages in the supply chain. With the onset of worldwide food shortages, interest in reducing postharvest losses in cassava has been increasing. In this research, the main goal was to evaluate biochemical changes and identify the metabolites involved in the deterioration of cassava roots. We found that high levels of ascorbic acid (AsA), polyphenol oxidase (PPO), dry matter, and proteins are correlated with overall lower rates of deterioration. On the other hand, soluble sugars such as glucose and fructose, as well as organic acids, mainly, succinic acid, seem to be upregulated during storage and may play a role in the deterioration of cassava roots. Cultivar Branco (BRA) was most resilient to postharvest physiological deterioration (PPD), while Oriental (ORI) was the most susceptible. Our findings suggest that PPO, AsA, and proteins may play a distinct role in PPD delay.

Identity and Behavior of Xylem-Residing Bacteria in Rough Lemon Roots of Florida Citrus Trees †

PubMed Central

Gardner, John M.; Feldman, Albert W.; Zablotowicz, Robert M.

1982-01-01

An aseptic vacuum extraction technique was used to obtain xylem fluid from the roots of rough lemon (Citrus jambhiri Lush.) rootstock of Florida citrus trees. Bacteria were consistently isolated from vascular fluid of both healthy and young tree decline-affected trees. Thirteen genera of bacteria were found, the most frequently occurring genera being Pseudomonas (40%), Enterobacter (18%), Bacillus, Corynebacterium, and other gram-positive bacteria (16%), and Serratia (6%). Xylem bacterial counts fluctuated seasonally. Bacterial populations ranged from 0.1 to 22 per mm3 of root tissue (about 102 to 2 × 104 bacteria per g of xylem) when bacterial counts were made on vascular fluid, but these numbers were 10- to 1,000-fold greater when aseptically homogenized xylem tissue was examined similarly. Some of the resident bacteria (4%) are potentially phytopathogenic. It is proposed that xylem bacteria have an important role in the physiology of citrus. PMID:16346030

Regulation of nitrogen uptake and assimilation: Effects of nitrogen source, root-zone pH, and aerial CO2 concentration on growth and productivity of soybeans

NASA Technical Reports Server (NTRS)

Raper, C. D.; Tolley-Henry, L.

1989-01-01

An important feature of controlled-environment crop production systems such as those to be used for life support of crews during space exploration is the efficient utilization of nitrogen supplies. Making decisions about the best sources of these supplies requires research into the relationship between nitrogen source and the physiological processes which regulate vegetative and reproductive plant growth. Work done in four areas within this research objective is reported: (1) experiments on the effects of root-zone pH on preferential utilization of NO3(-) versus NH4(+) nitrogen; (2) investigation of processes at the whole-plant level that regulate nitrogen uptake; (3) studies of the effects of atmospheric CO2 and NO3(-) supply on the growth of soybeans; and (4) examination of the role of NO3(-) uptake in enhancement of root respiration.

Regulation of seedling growth by ethylene and the ethylene-auxin crosstalk.

PubMed

Hu, Yuming; Vandenbussche, Filip; Van Der Straeten, Dominique

2017-03-01

This review highlights that the auxin gradient, established by local auxin biosynthesis and transport, can be controlled by ethylene, and steers seedling growth. A better understanding of the mechanisms in Arabidopsis will increase potential applications in crop species. In dark-grown Arabidopsis seedlings, exogenous ethylene treatment triggers an exaggeration of the apical hook, the inhibition of both hypocotyl and root elongation, and radial swelling of the hypocotyl. These features are predominantly based on the differential cell elongation in different cells/tissues mediated by an auxin gradient. Interestingly, the physiological responses regulated by ethylene and auxin crosstalk can be either additive or synergistic, as in primary root and root hair elongation, or antagonistic, as in hypocotyl elongation. This review focuses on the crosstalk of these two hormones at the seedling stage. Before illustrating the crosstalk, ethylene and auxin biosynthesis, metabolism, transport and signaling are briefly discussed.

A Potassium-Dependent Oxygen Sensing Pathway Regulates Plant Root Hydraulics.

PubMed

Shahzad, Zaigham; Canut, Matthieu; Tournaire-Roux, Colette; Martinière, Alexandre; Boursiac, Yann; Loudet, Olivier; Maurel, Christophe

2016-09-22

Aerobic organisms survive low oxygen (O2) through activation of diverse molecular, metabolic, and physiological responses. In most plants, root water permeability (in other words, hydraulic conductivity, Lpr) is downregulated under O2 deficiency. Here, we used a quantitative genetics approach in Arabidopsis to clone Hydraulic Conductivity of Root 1 (HCR1), a Raf-like MAPKKK that negatively controls Lpr. HCR1 accumulates and is functional under combined O2 limitation and potassium (K(+)) sufficiency. HCR1 regulates Lpr and hypoxia responsive genes, through the control of RAP2.12, a key transcriptional regulator of the core anaerobic response. A substantial variation of HCR1 in regulating Lpr is observed at the Arabidopsis species level. Thus, by combinatorially integrating two soil signals, K(+) and O2 availability, HCR1 modulates the resilience of plants to multiple flooding scenarios. Copyright © 2016 Elsevier Inc. All rights reserved.

An electric current associated with gravity sensing in maize roots

NASA Technical Reports Server (NTRS)

Bjorkman, T.; Leopold, A. C.

1987-01-01

The study of gravisensing would be greatly enhanced if physiological events associated with gravity sensing could be detected separately from subsequent growth processes. This report presents a means to discriminate sensing from the growth processes. By using a vibrating probe, we have found an electric current generated by the gravity sensing region of the root cap of maize (Zea mays cv Merit) in response to gravistimulation. On the upper surface of the root cap, the change from the endogenous current has a density of 0.55 microampere per square centimeter away from gravity. The onset of the current shift has a characteristic of lag of three to four minutes after gravistimulation, which corresponds to the presentation time for gravity sensing in this tissue. A description of the current provides some information about the sensing mechanism, as well as being a valuable means to detect gravity sensing independently of differential growth.

Phytotoxic cyanamide affects maize (Zea mays) root growth and root tip function: from structure to gene expression.

PubMed

Soltys, Dorota; Rudzińska-Langwald, Anna; Kurek, Wojciech; Szajko, Katarzyna; Sliwinska, Elwira; Bogatek, Renata; Gniazdowska, Agnieszka

2014-05-01

Cyanamide (CA) is a phytotoxic compound produced by four Fabaceae species: hairy vetch, bird vetch, purple vetch and black locust. Its toxicity is due to complex activity that involves the modification of both cellular structures and physiological processes. To date, CA has been investigated mainly in dicot plants. The goal of this study was to investigate the effects of CA in the restriction of the root growth of maize (Zea mays), representing the monocot species. CA (3mM) reduced the number of border cells in the root tips of maize seedlings and degraded their protoplasts. However, CA did not induce any significant changes in the organelle structure of other root cells, apart from increased vacuolization. CA toxicity was also demonstrated by its effect on cell cycle activity, endoreduplication intensity, and modifications of cyclins CycA2, CycD2, and histone HisH3 gene expression. In contrast, the arrangement of microtubules was not altered by CA. Treatment of maize seedlings with CA did not completely arrest mitotic activity, although the frequency of dividing cells was reduced. Furthermore, prolonged CA treatment increased the proportion of endopolyploid cells in the root tip. Cytological malformations were accompanied by an induction of oxidative stress in root cells, which manifested as enhanced accumulation of H2O2. Exposure of maize seedlings to CA resulted in an increased concentration of auxin and stimulated ethylene emission. Taken together, these findings suggested that the inhibition of root growth by CA may be a consequence of stress-induced morphogenic responses. Copyright © 2014. Published by Elsevier GmbH.

Alkaline stress and iron deficiency regulate iron uptake and riboflavin synthesis gene expression differently in root and leaf tissue: implications for iron deficiency chlorosis

PubMed Central

Hsieh, En-Jung; Waters, Brian M.

2016-01-01

Iron (Fe) is an essential mineral that has low solubility in alkaline soils, where its deficiency results in chlorosis. Whether low Fe supply and alkaline pH stress are equivalent is unclear, as they have not been treated as separate variables in molecular physiological studies. Additionally, molecular responses to these stresses have not been studied in leaf and root tissues simultaneously. We tested how plants with the Strategy I Fe uptake system respond to Fe deficiency at mildly acidic and alkaline pH by measuring root ferric chelate reductase (FCR) activity and expression of selected Fe uptake genes and riboflavin synthesis genes. Alkaline pH increased cucumber (Cucumis sativus L.) root FCR activity at full Fe supply, but alkaline stress abolished FCR response to low Fe supply. Alkaline pH or low Fe supply resulted in increased expression of Fe uptake genes, but riboflavin synthesis genes responded to Fe deficiency but not alkalinity. Iron deficiency increased expression of some common genes in roots and leaves, but alkaline stress blocked up-regulation of these genes in Fe-deficient leaves. In roots of the melon (Cucumis melo L.) fefe mutant, in which Fe uptake responses are blocked upstream of Fe uptake genes, alkaline stress or Fe deficiency up-regulation of certain Fe uptake and riboflavin synthesis genes was inhibited, indicating a central role for the FeFe protein. These results suggest a model implicating shoot-to-root signaling of Fe status to induce Fe uptake gene expression in roots. PMID:27605716

Morphological, anatomical, and ultrastructural changes (visualized through scanning electron microscopy) induced in Triticum aestivum by Pb²⁺ treatment.

PubMed

Kaur, Gurpreet; Singh, Harminder Pal; Batish, Daizy Rani; Kohli, Ravinder Kumar

2014-11-01

Lead (Pb) causes severe damage to crops, ecosystems, and humans, and alters the physiology and biochemistry of various plant species. It is hypothesized that Pb-induced metabolic alterations could manifest as structural variations in the roots of plants. In light of this, the morphological, anatomical, and ultrastructural variations (through scanning electron microscopy, SEM) were studied in 4-day-old seedlings of Triticum aestivum grown under Pb stress (0, 8, 16, 40, and 80 mg Pb(2+) l(-1); mild to highly toxic). The toxic effect was more pronounced in radicle growth than on the plumule growth. The SEM of the root of T. aestivum depicted morphological alterations and surface ultrastructural changes. Compared to intact and uniform surface cells in the control roots, cells were irregular and desiccated in Pb(2+)-treated roots. In Pb(2+)-treated roots, the number of root hairs increased manifold, showing dense growth, and these were apparently longer. Apart from the deformity in surface morphology and anatomy of the roots in response to Pb(2+) toxicity, considerable anatomical alterations were also observed. Pb(2+)-treated root exhibited signs of injury in the form of cell distortion, particularly in the cortical cells. The endodermis and pericycle region showed loss of uniformity post Pb(2+) exposure (at 80 mg l(-1) Pb(2+)). The cells appeared to be squeezed with greater depositions observed all over the tissue. The study concludes that Pb(2+) treatment caused structural anomalies and induced anatomical and surface ultrastructural changes in T. aestivum.

Experimentally altered rainfall regimes and host root traits affect grassland arbuscular mycorrhizal fungal communities.

PubMed

Deveautour, Coline; Donn, Suzanne; Power, Sally A; Bennett, Alison E; Powell, Jeff R

2018-04-01

Future climate scenarios predict changes in rainfall regimes. These changes are expected to affect plants via effects on the expression of root traits associated with water and nutrient uptake. Associated microorganisms may also respond to these new precipitation regimes, either directly in response to changes in the soil environment or indirectly in response to altered root trait expression. We characterized arbuscular mycorrhizal (AM) fungal communities in an Australian grassland exposed to experimentally altered rainfall regimes. We used Illumina sequencing to assess the responses of AM fungal communities associated with four plant species sampled in different watering treatments and evaluated the extent to which shifts were associated with changes in root traits. We observed that altered rainfall regimes affected the composition but not the richness of the AM fungal communities, and we found distinctive communities in the increased rainfall treatment. We found no evidence of altered rainfall regime effects via changes in host physiology because none of the studied traits were affected by changes in rainfall. However, specific root length was observed to correlate with AM fungal richness, while concentrations of phosphorus and calcium in root tissue and the proportion of root length allocated to fine roots were correlated to community composition. Our study provides evidence that climate change and its effects on rainfall may influence AM fungal community assembly, as do plant traits related to plant nutrition and water uptake. We did not find evidence that host responses to altered rainfall drive AM fungal community assembly in this grassland ecosystem. © 2018 John Wiley & Sons Ltd.

Bravo Emma! Music in the life and work of Charles Darwin.

PubMed

Derry, J F

2009-03-01

The long-term marital dance of Emma and Charles Darwin was set to the routine beat of an almost daily piano recital. Emma was a proficient pianist, and so a quality instrument was a welcome and appropriate house-warming present for their first marital home in London. That same piano accompanied the Darwins on their move to Downe before being upgraded for a newer model, which is still there, whilst another, cheaper piano may have played in Charles Darwin's work, particularly on earthworms. Whilst he lamented his own lack of musicality, Darwin revelled in his wife's prowess, a capacity that he recognised could be inherited, not least through observation of his own children. The evolution of musicality, he reasoned, was rooted in sexual attraction as a form of communication that preceded language.

Comparative impacts of iron oxide nanoparticles and ferric ions on the growth of Citrus maxima.

PubMed

Hu, Jing; Guo, Huiyuan; Li, Junli; Gan, Qiuliang; Wang, Yunqiang; Xing, Baoshan

2017-02-01

The impacts of iron oxide nanoparticles (γ-Fe 2 O 3 NPs) and ferric ions (Fe 3+ ) on plant growth and molecular responses associated with the transformation and transport of Fe 2+ were poorly understood. This study comprehensively compared and evaluated the physiological and molecular changes of Citrus maxima plants as affected by different levels of γ-Fe 2 O 3 NPs and Fe 3+ . We found that γ-Fe 2 O 3 NPs could enter plant roots but no translocation from roots to shoots was observed. 20 mg/L γ-Fe 2 O 3 NPs had no impact on plant growth. 50 mg/L γ-Fe 2 O 3 NPs significantly enhanced chlorophyll content by 23.2% and root activity by 23.8% as compared with control. However, 100 mg/L γ-Fe 2 O 3 NPs notably increased MDA formation, decreased chlorophyll content and root activity. Although Fe 3+ ions could be used by plants and promoted the synthesis of chlorophyll, they appeared to be more toxic than γ-Fe 2 O 3 NPs, especially for 100 mg/L Fe 3+ . The impacts caused by γ-Fe 2 O 3 NPs and Fe 3+ were concentration-dependent. Physiological results showed that γ-Fe 2 O 3 NPs at proper concentrations had the potential to be an effective iron nanofertilizer for plant growth. RT-PCR analysis showed that γ-Fe 2 O 3 NPs had no impact on AHA gene expression. 50 mg/L γ-Fe 2 O 3 NPs and Fe 3+ significantly increased expression levels of FRO2 gene and correspondingly had a higher ferric reductase activity compared to both control and Fe(II)-EDTA exposure, thus promoting the iron transformation and enhancing the tolerance of plants to iron deficiency. Relative levels of Nramp3 gene expression exposed to γ-Fe 2 O 3 NPs and Fe 3+ were significantly lower than control, indicating that all γ-Fe 2 O 3 NPs and Fe 3+ treatments could supply iron to C. maxima seedlings. Overall, plants can modify the speciation and transport of γ-Fe 2 O 3 NPs or Fe 3+ for self-protection and development by activating many physiological and molecular processes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Clarifying the Roles of Homeostasis and Allostasis in Physiological Regulation

PubMed Central

Ramsay, Douglas S.; Woods, Stephen C.

2014-01-01

Homeostasis, the dominant explanatory framework for physiological regulation, has undergone significant revision in recent years, with contemporary models differing significantly from the original formulation. Allostasis, an alternative view of physiological regulation, goes beyond its homeostatic roots, offering novel insights relevant to our understanding and treatment of several chronic health conditions. Despite growing enthusiasm for allostasis, the concept remains diffuse, due in part to ambiguity as to how the term is understood and used, impeding meaningful translational and clinical research on allostasis. Here we provide a more focused understanding of homeostasis and allostasis by explaining how both play a role in physiological regulation, and a critical analysis of regulation suggests how homeostasis and allostasis can be distinguished. Rather than focusing on changes in the value of a regulated variable (e.g., body temperature, body adiposity, or reward), research investigating the activity and relationship among the multiple regulatory loops that influence the value of these regulated variables may be the key to distinguishing homeostasis and allostasis. The mechanisms underlying physiological regulation and dysregulation are likely to have important implications for health and disease. PMID:24730599

Metabolomic Analysis and Phenylpropanoid Biosynthesis in Hairy Root Culture of Tartary Buckwheat Cultivars

PubMed Central

Li, Xiaohua; Bok Kim, Yeon; Romij Uddin, Md; Kim, Sun Ju; Suzuki, Tatsuro; Park, Nam Il; Park, Sang Un

2013-01-01

Buckwheat, Fagopyrum tataricum Gaertn., is an important medicinal plant, which contains several phenolic compounds, including one of the highest content of rutin, a phenolic compound with anti-inflammatory properties. An experiment was conducted to investigate the level of expression of various genes in the phenylpropanoid biosynthetic pathway to analyze in vitro production of anthocyanin and phenolic compounds from hairy root cultures derived from 2 cultivars of tartary buckwheat (Hokkai T8 and T10). A total of 47 metabolites were identified by gas chromatography–time-of-flight mass spectrometry (GC-TOFMS) and subjected to principal component analysis (PCA) in order to fully distinguish between Hokkai T8 and T10 hairy roots. The expression levels of phenylpropanoid biosynthetic pathway genes, through qRT-PCR, showed higher expression for almost all the genes in T10 than T8 hairy root except for FtF3’H-2 and FtFLS-2. Rutin, quercetin, gallic acid, caffeic acid, ferulic acid, 4-hydroxybenzoic acid, and 2 anthocyanin compounds were identified in Hokkai T8 and T10 hairy roots. The concentration of rutin and anthocyanin in Hokkai T10 hairy roots of tartary buckwheat was several-fold higher compared with that obtained from Hokkai T8 hairy root. This study provides useful information on the molecular and physiological dynamic processes that are correlated with phenylpropanoid biosynthetic gene expression and phenolic compound content in F. tataricum species. PMID:23799007

Programmed proteome response for drought avoidance/tolerance in the root of a C(3) xerophyte (wild watermelon) under water deficits.

PubMed

Yoshimura, Kazuya; Masuda, Akiko; Kuwano, Masayoshi; Yokota, Akiho; Akashi, Kinya

2008-02-01

Water availability is a critical determinant for the growth and ecological distribution of terrestrial plants. Although some xerophytes are unique regarding their highly developed root architecture and the successful adaptation to arid environments, virtually nothing is known about the molecular mechanisms underlying this adaptation. Here, we report physiological and molecular responses of wild watermelon (Citrullus lanatus sp.), which exhibits extraordinarily high drought resistance. At the early stage of drought stress, root development of wild watermelon was significantly enhanced compared with that of the irrigated plants, indicating the activation of a drought avoidance mechanism for absorbing water from deep soil layers. Consistent with this observation, comparative proteome analysis revealed that many proteins induced in the early stage of drought stress are involved in root morphogenesis and carbon/nitrogen metabolism, which may contribute to the drought avoidance via the enhancement of root growth. On the other hand, lignin synthesis-related proteins and molecular chaperones, which may function in the enhancement of physical desiccation tolerance and maintenance of protein integrity, respectively, were induced mostly at the later stage of drought stress. Our findings suggest that this xerophyte switches survival strategies from drought avoidance to drought tolerance during the progression of drought stress, by regulating its root proteome in a temporally programmed manner. This study provides new insights into the complex molecular networks within plant roots involved in the adaptation to adverse environments.

Nitrate reductase-mediated early nitric oxide burst alleviates oxidative damage induced by aluminum through enhancement of antioxidant defenses in roots of wheat (Triticum aestivum).

PubMed

Sun, Chengliang; Lu, Lingli; Liu, Lijuan; Liu, Wenjing; Yu, Yan; Liu, Xiaoxia; Hu, Yan; Jin, Chongwei; Lin, Xianyong

2014-03-01

• Nitric oxide (NO) is an important signaling molecule involved in the physiological processes of plants. The role of NO release in the tolerance strategies of roots of wheat (Triticum aestivum) under aluminum (Al) stress was investigated using two genotypes with different Al resistances. • An early NO burst at 3 h was observed in the root tips of the Al-tolerant genotype Jian-864, whereas the Al-sensitive genotype Yang-5 showed no NO accumulation at 3 h but an extremely high NO concentration after 12 h. Stimulating NO production at 3 h in the root tips of Yang-5 with the NO donor relieved Al-induced root inhibition and callose production, as well as oxidative damage and ROS accumulation, while elimination of the early NO burst by NO scavenger aggravated root inhibition in Jian-864. • Synthesis of early NO in roots of Jian-864 was mediated through nitrate reductase (NR) but not through NO synthase. Elevated antioxidant enzyme activities were induced by Al stress in both wheat genotypes and significantly enhanced by NO donor, but suppressed by NO scavenger or NR inhibitor. • These results suggest that an NR-mediated early NO burst plays an important role in Al resistance of wheat through modulating enhanced antioxidant defense to adapt to Al stress. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Effect of exogenous abscisic acid on morphology, growth and nutrient uptake of rice (Oryza sativa) roots under simulated acid rain stress.

PubMed

Liu, Hongyue; Ren, Xiaoqian; Zhu, Jiuzheng; Wu, Xi; Liang, Chanjuan

2018-05-31

Application of proper ABA can improve acid tolerance of rice roots by balancing endogenous hormones and promoting nutrient uptake. Abscisic acid (ABA) has an important signaling role in enhancing plant tolerance to environmental stress. To alleviate the inhibition on plant growth and productivity caused by acid rain, it is crucial to clarify the regulating mechanism of ABA on adaptation of plants to acid rain. Here, we studied the effects of exogenously applied ABA on nutrients uptake of rice roots under simulated acid rain (SAR) stress from physiological, biochemical and molecular aspects. Compared to the single SAR treatment (pH 4.5 or 3.5), exogenous 10 μM ABA alleviated the SAR-induced inhibition of root growth by balancing endogenous hormones (abscisic acid, indole-3-acetic acid, gibberellic acid and zeatin), promoting nutrient uptake (nitrate, P, K and Mg) in rice roots, and increasing the activity of the plasma membrane H + -ATPase by up-regulating expression levels of genes (OSA2, OSA4, OSA9 and OSA10). However, exogenous 100 μM ABA exacerbated the SAR-caused inhibition of root growth by disrupting the balance of endogenous hormones, and inhibiting nutrient uptake (nitrate, P, K, Ca and Mg) through decreasing the activity of the plasma membrane H + -ATPase. These results indicate that proper concentration of exogenous ABA could enhance tolerance of rice roots to SAR stress by promoting nutrients uptake and balancing endogenous hormones.

Aluminum induced physiological and proteomic responses in tea (Camellia sinensis) roots and leaves.

PubMed

Xu, Qingshan; Wang, Yu; Ding, Zhaotang; Fan, Kai; Ma, Dexin; Zhang, Yongliang; Yin, Qi

2017-06-01

Tea (Camellia sinensis (L.) O. Kuntze), is an aluminum (Al) hyperaccumulator and grows well in acid soils. Although Al-induced growth of tea plant has been studied, the proteomic profiles of tea plants in response to Al are unclear. In the present study, the proteomic profiles in tea roots and leaves under Al stress were investigated using iTRAQ proteomics approach. In total, 755 and 1059 differentially expressed proteins were identified in tea roots and leaves, respectively. KEGG enrichment analysis showed that the differentially expressed proteins in roots were mainly involved in 11 pathways whereas those from leaves were mainly involved in 9 pathways. Abundance of most protein functions in glycolytic metabolism were enhanced in tea roots, and proteins involved in photosynthesis were stimulated in tea leaves. The protein ferulate-5-hydroxylase (F5H) in lignin biosynthetic pathway was down-regulated in both roots and leaves. Furthermore, antioxidant enzymes (ascorbate peroxidase, catalase and glutathione S-transferase) and citrate synthesis were accumulated in tea roots in response to Al. The results indicated that active photosynthesis and glycolysis as well as increased activities of antioxidant enzymes can be considered as a possible reason for the stimulatory effects of Al on the growth of tea plants. Additionally, the down-regulation of F5H and the binding of Al and phenolic acids may reduce the accumulation of lignin. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Functional Heart Valve Scaffolds Obtained by Complete Decellularization of Porcine Aortic Roots in a Novel Differential Pressure Gradient Perfusion System

PubMed Central

Sierad, Leslie Neil; Shaw, Eliza Laine; Bina, Alexander; Brazile, Bryn; Rierson, Nicholas; Patnaik, Sourav S.; Kennamer, Allison; Odum, Rebekah; Cotoi, Ovidiu; Terezia, Preda; Branzaniuc, Klara; Smallwood, Harrison; Deac, Radu; Egyed, Imre; Pavai, Zoltan; Szanto, Annamaria; Harceaga, Lucian; Suciu, Horatiu; Raicea, Victor; Olah, Peter; Simionescu, Agneta; Liao, Jun; Movileanu, Ionela

2015-01-01

There is a great need for living valve replacements for patients of all ages. Such constructs could be built by tissue engineering, with perspective of the unique structure and biology of the aortic root. The aortic valve root is composed of several different tissues, and careful structural and functional consideration has to be given to each segment and component. Previous work has shown that immersion techniques are inadequate for whole-root decellularization, with the aortic wall segment being particularly resistant to decellularization. The aim of this study was to develop a differential pressure gradient perfusion system capable of being rigorous enough to decellularize the aortic root wall while gentle enough to preserve the integrity of the cusps. Fresh porcine aortic roots have been subjected to various regimens of perfusion decellularization using detergents and enzymes and results compared to immersion decellularized roots. Success criteria for evaluation of each root segment (cusp, muscle, sinus, wall) for decellularization completeness, tissue integrity, and valve functionality were defined using complementary methods of cell analysis (histology with nuclear and matrix stains and DNA analysis), biomechanics (biaxial and bending tests), and physiologic heart valve bioreactor testing (with advanced image analysis of open–close cycles and geometric orifice area measurement). Fully acellular porcine roots treated with the optimized method exhibited preserved macroscopic structures and microscopic matrix components, which translated into conserved anisotropic mechanical properties, including bending and excellent valve functionality when tested in aortic flow and pressure conditions. This study highlighted the importance of (1) adapting decellularization methods to specific target tissues, (2) combining several methods of cell analysis compared to relying solely on histology, (3) developing relevant valve-specific mechanical tests, and (4) in vitro testing of valve functionality. PMID:26467108

Isolation of a novel mutant gene for soil-surface rooting in rice (Oryza sativa L.)

PubMed Central

2013-01-01

Background Root system architecture is an important trait affecting the uptake of nutrients and water by crops. Shallower root systems preferentially take up nutrients from the topsoil and help avoid unfavorable environments in deeper soil layers. We have found a soil-surface rooting mutant from an M2 population that was regenerated from seed calli of a japonica rice cultivar, Nipponbare. In this study, we examined the genetic and physiological characteristics of this mutant. Results The primary roots of the mutant showed no gravitropic response from the seedling stage on, whereas the gravitropic response of the shoots was normal. Segregation analyses by using an F2 population derived from a cross between the soil-surface rooting mutant and wild-type Nipponbare indicated that the trait was controlled by a single recessive gene, designated as sor1. Fine mapping by using an F2 population derived from a cross between the mutant and an indica rice cultivar, Kasalath, revealed that sor1 was located within a 136-kb region between the simple sequence repeat markers RM16254 and 2935-6 on the terminal region of the short arm of chromosome 4, where 13 putative open reading frames (ORFs) were found. We sequenced these ORFs and detected a 33-bp deletion in one of them, Os04g0101800. Transgenic plants of the mutant transformed with the genomic fragment carrying the Os04g0101800 sequence from Nipponbare showed normal gravitropic responses and no soil-surface rooting. Conclusion These results suggest that sor1, a rice mutant causing soil-surface rooting and altered root gravitropic response, is allelic to Os04g0101800, and that a 33-bp deletion in the coding region of this gene causes the mutant phenotypes. PMID:24280269

Isolation of a novel mutant gene for soil-surface rooting in rice (Oryza sativa L.).

PubMed

Hanzawa, Eiko; Sasaki, Kazuhiro; Nagai, Shinsei; Obara, Mitsuhiro; Fukuta, Yoshimichi; Uga, Yusaku; Miyao, Akio; Hirochika, Hirohiko; Higashitani, Atsushi; Maekawa, Masahiko; Sato, Tadashi

2013-11-20

Root system architecture is an important trait affecting the uptake of nutrients and water by crops. Shallower root systems preferentially take up nutrients from the topsoil and help avoid unfavorable environments in deeper soil layers. We have found a soil-surface rooting mutant from an M2 population that was regenerated from seed calli of a japonica rice cultivar, Nipponbare. In this study, we examined the genetic and physiological characteristics of this mutant. The primary roots of the mutant showed no gravitropic response from the seedling stage on, whereas the gravitropic response of the shoots was normal. Segregation analyses by using an F2 population derived from a cross between the soil-surface rooting mutant and wild-type Nipponbare indicated that the trait was controlled by a single recessive gene, designated as sor1. Fine mapping by using an F2 population derived from a cross between the mutant and an indica rice cultivar, Kasalath, revealed that sor1 was located within a 136-kb region between the simple sequence repeat markers RM16254 and 2935-6 on the terminal region of the short arm of chromosome 4, where 13 putative open reading frames (ORFs) were found. We sequenced these ORFs and detected a 33-bp deletion in one of them, Os04g0101800. Transgenic plants of the mutant transformed with the genomic fragment carrying the Os04g0101800 sequence from Nipponbare showed normal gravitropic responses and no soil-surface rooting. These results suggest that sor1, a rice mutant causing soil-surface rooting and altered root gravitropic response, is allelic to Os04g0101800, and that a 33-bp deletion in the coding region of this gene causes the mutant phenotypes.

The divining root: moisture-driven responses of roots at the micro- and macro-scale.

PubMed

Robbins, Neil E; Dinneny, José R

2015-04-01

Water is fundamental to plant life, but the mechanisms by which plant roots sense and respond to variations in water availability in the soil are poorly understood. Many studies of responses to water deficit have focused on large-scale effects of this stress, but have overlooked responses at the sub-organ or cellular level that give rise to emergent whole-plant phenotypes. We have recently discovered hydropatterning, an adaptive environmental response in which roots position new lateral branches according to the spatial distribution of available water across the circumferential axis. This discovery illustrates that roots are capable of sensing and responding to water availability at spatial scales far lower than those normally studied for such processes. This review will explore how roots respond to water availability with an emphasis on what is currently known at different spatial scales. Beginning at the micro-scale, there is a discussion of water physiology at the cellular level and proposed sensory mechanisms cells use to detect osmotic status. The implications of these principles are then explored in the context of cell and organ growth under non-stress and water-deficit conditions. Following this, several adaptive responses employed by roots to tailor their functionality to the local moisture environment are discussed, including patterning of lateral root development and generation of hydraulic barriers to limit water loss. We speculate that these micro-scale responses are necessary for optimal functionality of the root system in a heterogeneous moisture environment, allowing for efficient water uptake with minimal water loss during periods of drought. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Molecular Genetics of Root Thigmoresponsiveness in Arabidopsis thaliana

NASA Technical Reports Server (NTRS)

Masson, Patrick H.

2002-01-01

The molecular mechanisms that allow plant roots to use gravity and touch as growth guides are investigated. We are using a molecular genetic strategy in Arabidopsis thaliana to study these processes. When Arabidopsis thaliana seedlings grow on tilted hard-agar surfaces, their roots develop a wavy pattern of growth which appears to derive from a succession of left-handed and right-handed circumnutation-like processes triggered by gravity and touch stimulation (Okada and Shimura, 1990; Rutherford et al., 1998; Rutherford and Masson, 1996). Interestingly, mutations that affect root waving on tilted hard-agar surfaces can be identified and characterized. Some of these mutations affect root gravitropism, while others appear to be responsible for the production of abnormal waves (no waves, compressed or square waves, coils) without affecting gravitropism. The specific objectives of this project were to functionally characterize two genes (WVD2 and WVD6) which are required for root waving on tilted agar surfaces, but not for root gravitropism. Specific objectives included a physiological and cytological analysis of the mutants, and molecular cloning and characterization of the corresponding genes. As summarized in this paper, we have reached these objectives. We have also identified and partially characterized other mutations that affect root skewing on hard-agar surfaces (sku5-1 and ago1), and have completed our work on the root-wave phenotype associated with mutations in genes of the tryptophan biosynthesis pathway (Lynn et al., 1999; Rutherford et al., 1998; Sedbrook et al., 2000, 2002). We briefly describe our progress on the cloning and characterization of WVD6, WVD2 and SKU5, and provide a list of papers (published, or in preparation) that derived from this grant. We also discuss the biological implications of our findings, with special emphasis on the analysis of WVD2.

Auxin, ethylene and light in gravitropic growth: new insights

NASA Astrophysics Data System (ADS)

Edelmann, Hg; Sabovljevic, A.; Njio, G.; Roth, U.

The regulation mechanism of gravitropic differential plant growth is commonly divided into three sequential processes: the perception of the gravistimulus (generally attributed to amyloplast sedimentation), the transduction of the perceived signal (of which very little is known), and the adequate differential growth response (generally attributed to asymmetric auxin redistribution). The detailled mechanism is still unresolved and remains to be elucidated in significant parts. Employing 2D SDS-PAGE /Q-TOF amongst other methods and strategies we studied the effect of different auxins on gravitropism of coleoptiles and hypocotyls. We also analyzed the effects of light and ethylene (synthesis and perception) on gravitropic growth of primary shoots and roots and analyzed the protein pattern with respect to the observed physiological effects. In coleoptiles, under the applied experimental conditions the effect of 2,4-dichlorophenoxy acetic acid (2,4 D) on gravitropism differed from the effect of indolylacetic acid (IAA), which was similar to the one observed in sunflower hypocotyls. In roots, the relevance of ethylene for gravitropic differential growth and the capacity to evade mechanical barriers during horizontal gravistimulation was analyzed in detail. A special focus was addressed on the physiological significance of the root cap. We will show that the relevance of ethylene for gravitropism has hitherto been misjudged. Further new findings and their implications for the regulation mechanism of gravitropism will be presented and discussed. Kramer et al., (2003) J. Ex. Bot. 54, (393), 2723-2732 Edelmann, H.G., (2002) J. Ex. Bot. 53, (375), 1825-1828

Remediation mechanisms for Cd-contaminated soil using natural sepiolite at the field scale.

PubMed

Yin, Xiuling; Xu, Yingming; Huang, Rong; Huang, Qingqing; Xie, Zhonglei; Cai, Yanming; Liang, Xuefeng

2017-12-13

Remediation of heavy metal polluted agricultural soil is essential for human health and ecological safety and remediation mechanisms at the microscopic level are vital for their large-scale utilization. In this study, natural sepiolite was employed as an immobilization agent for in situ field-scale remediation of Cd-contaminated paddy soil and the remediation mechanisms were investigated in terms of soil chemistry and plant physiology. Natural sepiolite had a significant immobilization effect for bioavailable Cd contents in paddy soil, and consequently could lower the Cd concentrations of brown rice, husk, straw, and roots of rice plants by 54.7-73.7%, 44.0-62.5%, 26.5-67.2%, and 36.7-46.7%, respectively. Regarding soil chemistry, natural sepiolite increased the soil pH values and shifted the zeta potentials of soil particles to be more negative, enhancing the fixation or sorption of Cd on soil particles, and resulted in the reduction of HCl and DTPA extractable Cd concentrations in paddy soil. Natural sepiolite neither enhanced nor inhibited iron plaques on the rice root surface, but did change the chemical environments of Fe and S in rice root. Natural sepiolite improved the activities of antioxidant enzymes and enhanced the total antioxidant capacity to alleviate the stress of Cd. It also promotes the synthesis of GSH and NPT to complete the detoxification. In general, the remediation mechanisms of natural sepiolite for the Cd pollutant in paddy soil could be summarized as the collective effects of soil chemistry and plant physiology.

Bioagents and silicon promoting fast early upland rice growth.

PubMed

de Sousa, Thatyane Pereira; de Souza, Alan Carlos Alves; de Filippi, Marta Cristina Corsi; Lanna, Anna Cristina; Cortês, Marcio Vinicius; Pinheiro, Hugo Alves; da Silva, Gisele Barata

2018-02-01

Upland rice can overcome major challenges through the insertion of silicate fertilization and the presence of plant growth-promoting microorganisms (PGPMs) during its cultivation, as these factors promote an increase in vigor and plant disease resistance. Two consecutive experiments were conducted to evaluate the beneficial effects of silicon fertilization combined with the PGPM, Pseudomonas fluorensces, Burkholderia pyrrocinia, and a pool of Trichoderma asperellum, in upland rice seedlings, cultivar BRS Primavera CL: (a) E1, selecting PGPM type and Si doses for rice growth promotion and leaf blast supression, and (b) E2, evaluating physiological characteristics correlated with mechanisms involved in the higher vegetative growth in highlighted treatments from E1. In E1, 2 Si t ha -1 combined with the application of T. asperellum pool or PGPM mixture increased 54% in root dry matter biomass and 35 and 65% in shoot and root lengths, respectively; it also suppressed 99% of rice blast severity. In E2, shoot and root dry matter biomass and length, photosynthetic rate, water use efficiency, total soluble sugar, and chloroplastidic pigments were superior in BRS Primavera CL seedlings treated with 2 Si t ha -1 and T. asperellum pool or PGPM mixture. Higher salicilic and jasmonic acid levels were found in seedlings treated with Si and T. asperellum pool, individually. These physiological characteristics may explain, in part, the higher vigor of upland rice seedlings promoted by the synergistic effect between silicate fertilization and beneficial microorganisms.

Contrasting hydraulic strategies in two tropical lianas and their host trees.

PubMed

Johnson, Daniel M; Domec, Jean-Christophe; Woodruff, David R; McCulloh, Katherine A; Meinzer, Frederick C

2013-02-01

Tropical liana abundance has been increasing over the past 40 yr, which has been associated with reduced rainfall. The proposed mechanism allowing lianas to thrive in dry conditions is deeper root systems than co-occurring trees, although we know very little about the fundamental hydraulic physiology of lianas. To test the hypothesis that two abundant liana species would physiologically outperform their host tree under reduced water availability, we measured rooting depth, hydraulic properties, plant water status, and leaf gas exchange during the dry season in a seasonally dry tropical forest. We also used a model to compare water use by one of the liana species and the host tree during drought. All species measured were shallowly rooted. The liana species were more vulnerable to embolism than host trees and experienced water potentials that were predicted to result in substantial hydraulic losses in both leaves and stems. Water potentials measured in host trees were not negative enough to result in significant hydraulic losses. Model results predicted the liana to have greater gas exchange than its host tree during drought and nondrought conditions. The host tree species had a more conservative strategy for maintenance of the soil-to-leaf hydraulic pathway than the lianas it supported. The two liana species experienced embolism in stems and leaves, based on vulnerability curves and water potentials. These emboli were presumably repaired before the next morning. However, in the host tree species, reduced stomatal conductance prevented leaf or stem embolism.

Physiological aspects of fungi isolated from root nodules of faba bean (Vicia faba L.).

PubMed

Omar, S A; Abd-Alla, M H

2000-03-01

The present study was made to isolate and assess some physiological characteristics of root nodule-colonizing fungi. During this study, 17 fungal species were isolated from root nodule samples taken from faba bean plants (Vicia faba L.) collected from different sites at Assiut area (Egypt). The growth of faba bean plants in pots was significantly promoted by soil inoculation with most fungi. Growth was checked in pots with inocula of Cladosporium cladosporioides, Fusarium moniliforme, F: oxysporium, F solani, Macrophominia phaseolina and Rhizoctonia solani which were added separately. All growth-promoting fungi were capable of producing cellulase, pectin lyase, polygalacturonase, protease, urease, amidase, acid phosphatase, alkaline phosphatase and arylsulfatase in growth medium supplemented with the corresponding substrates. Four fungal species, Aspergillus awamori, A. flavus, Penicillium chrysogenum and Trichoderma koningii showed the highest rates of enzyme formation. The effect of the addition of six trace elements to the growth media at 30 micromol/ml on enzyme production revealed some dependency on species, enzyme and metal ion. Cd2+, Hg2+ and Zn2+ generally inhibited enzyme activity. Cu(1+), Fe3+ and Al3+ showed a stimulatory effect. Fungicides (afugan and tilt) and herbicides (brominal and fusilade) at 50 ppm generally promoted enzyme activity, but insecticides (kelthane and fenvalerate) caused some inhibition to enzyme activities. Salinization of the growth media with NaCl strongly inhibited the enzymatic activity of all fungi at concentrations between 0.5 and 1.5%.

Cell biology of aluminum toxicity and tolerance in higher plants.

PubMed

Matsumoto, H

2000-01-01

Aluminum is the major element in the soil and exists as a stable complex with oxygen and silicate in neutral and weakly acidic soil. When the soil pH is lower than 4.5-5.0, Al is solubilized in the soil water and absorbed by plant roots. Absorbed Al inhibits root elongation severely, and the elongation of roots exposed to Al3+ as low as mumol level is inhibited within an hour(s). Thus much research has been conducted to understand the mechanism of Al toxicity and tolerance. Al is located specifically at the root apex. Al-sensitive plants absorb more Al than do Al-tolerant plants, and thus the exclusion mechanism of Al is the major idea for Al tolerance. The understanding of Al stress in plants is important for stable food production in future. Al is a complicated ion in its chemical form and biological function. In this chapter, mechanisms of Al toxicity and tolerance proposed during the past few decades as well as future topics are described from physiological and molecular points of view.

Calcium-regulated in vivo protein phosphorylation in Zea mays L. root tips

NASA Technical Reports Server (NTRS)

Raghothama, K. G.; Reddy, A. S.; Friedmann, M.; Poovaiah, B. W.

1987-01-01

Calcium dependent protein phosphorylation was studied in corn (Zea mays L.) root tips. Prior to in vivo protein phosphorylation experiments, the effect of calcium, ethyleneglycol-bis-(beta-aminoethyl ether)-N-N' -tetraacetic acid (EGTA) and calcium ionophore (A-23187) on phosphorus uptake was studied. Calcium increased phosphorus uptake, whereas EGTA and A-23187 decreased it. Consequently, phosphorus concentration in the media was adjusted so as to attain similar uptake in different treatments. Phosphoproteins were analyzed by two-dimensional gel electrophoresis. Distinct changes in phosphorylation were observed following altered calcium levels. Calcium depletion in root tips with EGTA and A-23187 decreased protein phosphorylation. However, replenishment of calcium following EGTA and ionophore pretreatment enhanced phosphorylation of proteins. Preloading of the root tips with 32P in the presence of EGTA and A-23187 followed by a ten minute calcium treatment, resulted in increased phosphorylation indicating the involvement of calcium, calcium and calmodulin-dependent kinases. Calmodulin antagonist W-7 was effective in inhibiting calcium-promoted phosphorylation. These studies suggest a physiological role for calcium-dependent phosphorylation in calcium-mediated processes in plants.

Airborne signals from Trichoderma fungi stimulate iron uptake responses in roots resulting in priming of jasmonic acid-dependent defences in shoots of Arabidopsis thaliana and Solanum lycopersicum.

PubMed

Martínez-Medina, Ainhoa; Van Wees, Saskia C M; Pieterse, Corné M J

2017-11-01

Root colonization by Trichoderma fungi can trigger induced systemic resistance (ISR). In Arabidopsis, Trichoderma-ISR relies on the transcription factor MYB72, which plays a dual role in the onset of ISR and the activation of Fe uptake responses. Volatile compounds (VCs) from rhizobacteria are important elicitors of MYB72 in Arabidopsis roots. Here, we investigated the mode of action of VCs from Trichoderma fungi in the onset of ISR and Fe uptake responses. VCs from Trichoderma asperellum and Trichoderma harzianum were applied in an in vitro split-plate system with Arabidopsis or tomato seedlings. Locally, Trichoderma-VCs triggered MYB72 expression and molecular, physiological and morphological Fe uptake mechanisms in Arabidopsis roots. In leaves, Trichoderma-VCs primed jasmonic acid-dependent defences, leading to an enhanced resistance against Botrytis cinerea. By using Arabidopsis micrografts of VCs-exposed rootstocks and non-exposed scions, we demonstrated that perception of Trichoderma-VCs by the roots leads to a systemic signal that primes shoots for enhanced defences. Trichoderma-VCs also elicited Fe deficiency responses and shoot immunity in tomato, suggesting that this phenomenon is expressed in different plant species. Our results indicate that Trichoderma-VCs trigger locally a readjustment of Fe homeostasis in roots, which links to systemic elicitation of ISR by priming of jasmonic acid-dependent defences. © 2017 John Wiley & Sons Ltd.