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  1. Enhancing auxin accumulation in maize root tips improves root growth and dwarfs plant height.

    PubMed

    Li, Zhaoxia; Zhang, Xinrui; Zhao, Yajie; Li, Yujie; Zhang, Guangfeng; Peng, Zhenghua; Zhang, Juren

    2017-05-12

    Maize is a globally important food, feed crop and raw material for the food and energy industry. Plant architecture optimization plays important roles in maize yield improvement. PIN-FORMED (PIN) proteins are important for regulating auxin spatiotemporal asymmetric distribution in multiple plant developmental processes. In this study, ZmPIN1a overexpression in maize increased the number of lateral roots and inhibited their elongation, forming a developed root system with longer seminal roots and denser lateral roots. ZmPIN1a overexpression reduced plant height, internode length and ear height. This modification of the maize phenotype increased the yield under high-density cultivation conditions, and the developed root system improved plant resistance to drought, lodging and a low-phosphate environment. IAA concentration, transport capacity determination and application of external IAA indicated that ZmPIN1a overexpression led to increased IAA transport from shoot to root. The increase in auxin in the root enabled the plant to allocate more carbohydrates to the roots, enhanced the growth of the root and improved plant resistance to environmental stress. These findings demonstrate that maize plant architecture can be improved by root breeding to create an ideal phenotype for further yield increases. © 2017 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

  2. Externally imposed electric field enhances plant root tip regeneration

    PubMed Central

    Kral, Nicolas; Hanna Ougolnikova, Alexandra

    2016-01-01

    Abstract In plants, shoot and root regeneration can be induced in the distinctive conditions of tissue culture (in vitro) but is also observed in intact individuals (in planta) recovering from tissue damage. Roots, for example, can regenerate their fully excised meristems in planta, even in mutants with impaired apical stem cell niches. Unfortunately, to date a comprehensive understanding of regeneration in plants is still missing. Here, we provide evidence that an imposed electric field can perturb apical root regeneration in Arabidopsis. Crucially, we explored both spatial and temporal competences of the stump to respond to electrical stimulation, by varying respectively the position of the cut and the time interval between excision and stimulation. Our data indicate that a brief pulse of an electric field parallel to the root is sufficient to increase by up to two‐fold the probability of its regeneration, and to perturb the local distribution of the hormone auxin, as well as cell division regulation. Remarkably, the orientation of the root towards the anode or the cathode is shown to play a role. PMID:27606066

  3. Externally imposed electric field enhances plant root tip regeneration.

    PubMed

    Kral, Nicolas; Hanna Ougolnikova, Alexandra; Sena, Giovanni

    2016-06-01

    In plants, shoot and root regeneration can be induced in the distinctive conditions of tissue culture (in vitro) but is also observed in intact individuals (in planta) recovering from tissue damage. Roots, for example, can regenerate their fully excised meristems in planta, even in mutants with impaired apical stem cell niches. Unfortunately, to date a comprehensive understanding of regeneration in plants is still missing. Here, we provide evidence that an imposed electric field can perturb apical root regeneration in Arabidopsis. Crucially, we explored both spatial and temporal competences of the stump to respond to electrical stimulation, by varying respectively the position of the cut and the time interval between excision and stimulation. Our data indicate that a brief pulse of an electric field parallel to the root is sufficient to increase by up to two-fold the probability of its regeneration, and to perturb the local distribution of the hormone auxin, as well as cell division regulation. Remarkably, the orientation of the root towards the anode or the cathode is shown to play a role.

  4. In situ stimulation vs. bioaugmentation: Can microbial inoculation of plant roots enhance biodegradation of organic compounds?

    SciTech Connect

    Kingsley, M.T.; Metting, F.B. Jr.; Fredrickson, J.K.; Seidler, R.J.

    1993-06-01

    The use of plant roots and their associated rhizosphere bacteria for biocontainment and biorestoration offers several advantages for treating soil-dispersed contaminants and for application to large land areas. Plant roots function as effective delivery systems, since root growth transports bacteria vertically and laterally along the root in the soil column (see [ 1,2]). Movement of microbes along roots and downward in the soil column can be enhanced via irrigation [1-4]. For example, Ciafardini et al. [3] increased the nodulation and the final yield of soybeans during pod filling by including Bradyrhizobium japonicum in the irrigation water. Using rhizosphere microorganisms is advantageous for biodegradation of compounds that are degraded mainly by cometabolic processes, e.g., trichloroethylene (TCE). The energy source for bacterial growth and metabolism is supplied by the plant in the form of root exudates and other sloughed organic material. Plants are inexpensive, and by careful choice of species that possess either tap or fibrous root growth patterns, they can be used to influence mass transport of soil contaminants to the root surface via the transpiration stream [5]. Cropping of plants to remove heavy metals from contaminated soils has been proposed as a viable, low-cost, low-input treatment option [6]. The interest in use of plants as a remediation strategy has even reached the popular press [7], where the use of ragweed for the reclamation of sites contaminated with tetraethyl lead and other heavy metals was discussed.

  5. Agrobacteria Enhance Plant Defense Against Root-Knot Nematodes on Tomato.

    PubMed

    Lamovšek, Janja; Gerič Stare, Barbara; Mavrič Pleško, Irena; Širca, Saša; Urek, Gregor

    2017-01-30

    The increased incidence of the crown gall disease caused by Agrobacterium tumefaciens has long been associated with activities of root-knot nematodes, Meloidogyne spp. Pot experiments on tomato were designed to assess plant vitality, nematode reproduction and crown gall incidence in combined infection with Agrobacterium and Meloidogyne on tomato roots. Results suggest that tomato plants infected with pathogenic A. tumefaciens two days before the nematodes show enhanced plant defense against M. ethiopica resulting in lower egg and gall counts on roots 45 and 90 days post inoculation (dpi); no significantly enhanced defense was observed when the plant was inoculated with bacteria and nematodes at the same time. Split-root experiments also showed that the observed interaction was systemic. RT-qPCR analysis that targeted several genes under plant hormonal control suggests that the suppression was mediated via systemic acquired resistance by the pathogenesis-related protein 1 (PR1) and that M. ethiopica did not enhance the defense reaction of tomato against Agrobacterium. Nematodes completely inhibited tumor growth in a 45-day experiment if inoculated onto the roots before the pathogenic bacteria. We conclude that the observed antagonism in the tested pathosystem was the result of initially strong plant defense that was later suppressed by the invading pathogen and pest.

  6. Root endophyte Piriformospora indica DSM 11827 alters plant morphology, enhances biomass and antioxidant activity of medicinal plant Bacopa monniera.

    PubMed

    Prasad, Ram; Kamal, Shwet; Sharma, Pradeep K; Oelmüller, Ralf; Varma, Ajit

    2013-12-01

    Unorganized collections and over exploitation of naturally occurring medicinal plant Bacopa monniera is leading to rapid depletion of germplasm and is posing a great threat to its survival in natural habitats. The species has already been listed in the list of highly threatened plants of India. This calls for micropropagation based multiplication of potential accessions and understanding of their mycorrhizal associations for obtaining plants with enhanced secondary metabolite contents. The co-cultivation of B. monniera with axenically cultivated root endophyte Piriformospora indica resulted in growth promotion, increase in bacoside content, antioxidant activity and nuclear hypertrophy of this medicinal plant.

  7. Enhanced secondary metabolite biosynthesis by elicitation in transformed plant root system: effect of abiotic elicitors.

    PubMed

    Jeong, Gwi-Taek; Park, Don-Hee

    2006-01-01

    Plants generally produce secondary metabolites in nature as a defense mechanism against pathogenic and insect attack. In this study, we applied several abiotic elicitors in order to enhance growth and ginseng saponin biosynthesis in the hairy roots of Panax ginseng. Generally, elicitor treatments were found to inhibit the growth of the hairy roots, although simultaneously enhancing ginseng saponin biosynthesis. Tannic acid profoundly inhibited the hairy root growth during growth period. Also, ginseng saponin content was not significantly different from that of the control. The addition of selenium at inoculum time did not significantly affect ginseng saponin biosynthesis. However, when 0.5 mM selenium was added as an elicitor after 21 d of culture, ginseng saponin content and productivity increased to about 1.31 and 1.33 times control levels, respectively. Also, the addition of 20 microM NiSO4 resulted in an increase in ginseng saponin content and productivity, to about 1.20 and 1.23 times control levels, respectively, and also did not inhibit the growth of the roots. Sodium chloride treatment inhibited hairy root growth, except at a concentration of 0.3% (w/v). Increases in the amounts of synthesized ginseng saponin were observed at all concentrations of added sodium chloride. At 0.1% (w/v) sodium chloride, ginseng saponin content and productivity were increased to approx 1.15 and 1.13 times control values, respectively. These results suggest that processing time for the generation of ginseng saponin in a hairy root culture can be reduced via the application of an elicitor.

  8. Water Deficit Enhances C Export to the Roots in Arabidopsis thaliana Plants with Contribution of Sucrose Transporters in Both Shoot and Roots.

    PubMed

    Durand, Mickaël; Porcheron, Benoît; Hennion, Nils; Maurousset, Laurence; Lemoine, Rémi; Pourtau, Nathalie

    2016-03-01

    Root high plasticity is an adaptation to its changing environment. Water deficit impairs growth, leading to sugar accumulation in leaves, part of which could be available to roots via sucrose (Suc) phloem transport. Phloem loading is widely described in Arabidopsis (Arabidopsis thaliana), while unloading in roots is less understood. To gain information on leaf-to-root transport, a soil-based culture system was developed to monitor root system architecture in two dimensions. Under water deficit (50% of soil water-holding capacity), total root length was strongly reduced but the depth of root foraging and the shape of the root system were less affected, likely to improve water uptake. (14)CO2 pulse-chase experiments confirmed that water deficit enhanced carbon (C) export to the roots, as suggested by the increased root-to-shoot ratio. The transcript levels of AtSWEET11 (for sugar will eventually be exported transporter), AtSWEET12, and AtSUC2 (for Suc carrier) genes, all three involved in Suc phloem loading, were significantly up-regulated in leaves of water deficit plants, in accordance with the increase in C export from the leaves to the roots. Interestingly, the transcript levels of AtSUC2 and AtSWEET11 to AtSWEET15 were also significantly higher in stressed roots, underlying the importance of Suc apoplastic unloading in Arabidopsis roots and a putative role for these Suc transporters in Suc unloading. These data demonstrate that, during water deficit, plants respond to growth limitation by allocating relatively more C to the roots to maintain an efficient root system and that a subset of Suc transporters is potentially involved in the flux of C to and in the roots. © 2016 American Society of Plant Biologists. All Rights Reserved.

  9. Plant-Microbe Communication Enhances Auxin Biosynthesis by a Root-Associated Bacterium, Bacillus amyloliquefaciens SQR9.

    PubMed

    Liu, Yunpeng; Chen, Lin; Zhang, Nan; Li, Zunfeng; Zhang, Guishan; Xu, Yu; Shen, Qirong; Zhang, Ruifu

    2016-04-01

    Mechanisms by which beneficial rhizobacteria promote plant growth include tryptophan-dependent indole-3-acetic acid (IAA) synthesis. The abundance of tryptophan in the rhizosphere, however, may influence the level of benefit provided by IAA-producing rhizobacteria. This study examined the cucumber-Bacillus amyloliquefaciens SQR9 system and found that SQR9, a bacterium previously shown to enhance the growth of cucumber, increased root secretion of tryptophan by three- to fourfold. Using a split-root system, SQR9 colonization of roots in one chamber not only increased tryptophan secretion from the noninoculated roots but also increased the expression of the cucumber tryptophan transport gene but not the anthranilate synthesis gene in those roots. The increased tryptophan in isolated rhizosphere exudates was sufficient to support increased IAA production by SQR9. Moreover, SQR9 colonization of roots in one chamber in the split-root system resulted in sufficient tryptophan production by the other roots to upregulate SQR9 IAA biosynthesis genes, including a 27-fold increase in the indole-3-acetonitrilase gene yhcX during subsequent colonization of those roots. Deletion of yhcX eliminated SQR9-mediated increases in root surface area, likely by reducing IAA-stimulated lateral root growth. This study demonstrates a chemical dialogue between B. amyloliquefaciens and cucumber in which this communication contributes to bacteria-mediated plant-growth enhancement.

  10. Water Deficit Enhances C Export to the Roots in Arabidopsis thaliana Plants with Contribution of Sucrose Transporters in Both Shoot and Roots1[OPEN

    PubMed Central

    Durand, Mickaël; Porcheron, Benoît; Maurousset, Laurence; Lemoine, Rémi; Pourtau, Nathalie

    2016-01-01

    Root high plasticity is an adaptation to its changing environment. Water deficit impairs growth, leading to sugar accumulation in leaves, part of which could be available to roots via sucrose (Suc) phloem transport. Phloem loading is widely described in Arabidopsis (Arabidopsis thaliana), while unloading in roots is less understood. To gain information on leaf-to-root transport, a soil-based culture system was developed to monitor root system architecture in two dimensions. Under water deficit (50% of soil water-holding capacity), total root length was strongly reduced but the depth of root foraging and the shape of the root system were less affected, likely to improve water uptake. 14CO2 pulse-chase experiments confirmed that water deficit enhanced carbon (C) export to the roots, as suggested by the increased root-to-shoot ratio. The transcript levels of AtSWEET11 (for sugar will eventually be exported transporter), AtSWEET12, and AtSUC2 (for Suc carrier) genes, all three involved in Suc phloem loading, were significantly up-regulated in leaves of water deficit plants, in accordance with the increase in C export from the leaves to the roots. Interestingly, the transcript levels of AtSUC2 and AtSWEET11 to AtSWEET15 were also significantly higher in stressed roots, underlying the importance of Suc apoplastic unloading in Arabidopsis roots and a putative role for these Suc transporters in Suc unloading. These data demonstrate that, during water deficit, plants respond to growth limitation by allocating relatively more C to the roots to maintain an efficient root system and that a subset of Suc transporters is potentially involved in the flux of C to and in the roots. PMID:26802041

  11. Paenibacillus polymyxa BFKC01 enhances plant iron absorption via improved root systems and activated iron acquisition mechanisms.

    PubMed

    Zhou, Cheng; Guo, Jiansheng; Zhu, Lin; Xiao, Xin; Xie, Yue; Zhu, Jian; Ma, Zhongyou; Wang, Jianfei

    2016-08-01

    Despite the high abundance of iron (Fe) in most earth's soils, Fe is the major limiting factor for plant growth and development due to its low bioavailability. With an increasing recognition that soil microbes play important roles in plant growth, several strains of beneficial rhizobactria have been applied to improve plant nutrient absorption, biomass, and abiotic or biotic stress tolerance. In this study, we report the mechanisms of microbe-induced plant Fe assimilation, in which the plant growth promoting rhizobacteria (PGPR) Paenibacillus polymyxa BFKC01 stimulates plant's Fe acquisition machinery to enhance Fe uptake in Arabidopsis plants. Mechanistic studies show that BFKC01 transcriptionally activates the Fe-deficiency-induced transcription factor 1 (FIT1), thereby up-regulating the expression of IRT1 and FRO2. Furthermore, BFKC01 has been found to induce plant systemic responses with the increased transcription of MYB72, and the biosynthetic pathways of phenolic compounds are also activated. Our data reveal that abundant phenolic compounds are detected in root exudation of the BFKC01-inoculated plants, which efficiently facilitate Fe mobility under alkaline conditions. In addition, BFKC01 can secret auxin and further improved root systems, which enhances the ability of plants to acquire Fe from soils. As a result, BFKC01-inoculated plants have more endogenous Fe and increased photosynthetic capacity under alkaline conditions as compared to control plants. Our results demonstrate the potential roles of BFKC01 in promoting Fe acquisition in plants and underline the intricate integration of microbial signaling in controlling plant Fe acquisition.

  12. Multi-walled carbon nanotubes can enhance root elongation of wheat ( Triticum aestivum) plants

    NASA Astrophysics Data System (ADS)

    Wang, Xiuping; Han, Heyou; Liu, Xueqin; Gu, Xiaoxu; Chen, Kun; Lu, Donglian

    2012-06-01

    The potential effects of oxidized multi-walled carbon nanotubes (o-MWCNTs) with a length ranging from 50 to 630 nm on the development and physiology of wheat plants were evaluated by examining their effects on seed germination, root elongation, stem length, and vegetative biomass at a concentration ranging from 10 to 160 μg/mL in the plant. Results indicated that after 7 days of exposure to the o-MWCNTs medium, faster root growth and higher vegetative biomass were observed, but seed germination and stem length did not show any difference as compared with controls. Moreover, a physiological study was conducted at cellular level using a traditional physiological approach to evidence the possible alterations in morphology, the cell length of root zone, and the dehydrogenase activity of seedlings. Transmission electron microscopy images revealed that o-MWCNTs could penetrate the cell wall and enter the cytoplasm after being taken up by roots. The cell length of root zone for the seedlings germinated and grown in the o-MWCNTs (80 μg/mL) medium increased by 1.4-fold and a significant concentration-dependent increase in the dehydrogenase activity for the o-MWCNT-treated wheat seedlings was detected. These findings suggest that o-MWCNTs can significantly promote cell elongation in the root system and increase the dehydrogenase activity, resulting in faster root growth and higher biomass production.

  13. Artificial macropores attract crop roots and enhance plant productivity on compacted soils.

    PubMed

    Colombi, Tino; Braun, Serge; Keller, Thomas; Walter, Achim

    2017-01-01

    The structure of compacted soils is characterised by decreased (macro-)porosity, which leads to increased mechanical impedance and decreased fluid transport rates, resulting in reduced root growth and crop productivity. Particularly in soils with high mechanical impedance, macropores can be used by roots as pathways of least resistance. This study investigated how different soil physical states relate to whole plant growth and whether roots grow towards spots with favourable soil physical conditions. Experiments were conducted under controlled and field conditions. Soybean (Glycine max L.), wheat (Triticum aestivum L.) and maize (Zea mays L.) were grown on uncompacted soil, compacted soil and compacted soil with artificial macropores. The interactions between roots and artificial macropores were quantified using X-ray computed tomography. Active growth of roots towards artificial macropores was observed for all three species. Roots grew either into macropores (predominantly in maize) or crossed them (predominantly in wheat). The presence of artificial macropores in compacted soil enabled all three species to compensate for decreased early vigour at later developmental stages. These results show that roots sense their physical environment, enabling them to grow towards spots with favourable soil conditions. The different kinds of root-macropore interaction indicated that macropores serve as a path of least resistance and a source of oxygen, both resulting in increased crop productivity on compacted soils. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Sclareol induces plant resistance to root-knot nematode partially through ethylene-dependent enhancement of lignin accumulation.

    PubMed

    Fujimoto, Taketo; Mizukubo, Takayuki; Abe, Hiroshi; Seo, Shigemi

    2015-04-01

    The root-knot nematode (RKN) is one of the most devastating parasitic nematodes of plants. Although some secondary metabolites released by the host plant play roles as defense substances against parasitic nematodes, the mechanism underlying the induction of such defense responses is not fully understood. We found that sclareol, a natural diterpene known as an antimicrobial and defense-related molecule, inhibited RKN penetration of tomato and Arabidopsis roots. Sclareol induced genes related to ethylene (ET) biosynthesis and signaling and phenylpropanoid metabolism in Arabidopsis roots. In roots of ein2-1, an ET-insensitive mutant line, both sclareol-induced inhibition of RKN penetration and sclareol-induced enhancement of lignin accumulation were abolished. A mutant defective in lignin accumulation did not exhibit such inhibition. Sclareol also activated MPK3 and MPK6, Arabidopsis mitogen-activated protein kinases whose activation is required for triggering ET biosynthesis. Sclareol-induced inhibition of RKN penetration was exhibited by mutants of neither MPK3 nor MPK6. Treatment with a biosynthetic precursor of ET was insufficient compared with sclareol treatment to inhibit RKN penetration, suggesting the existence of an ET-independent signaling pathway leading to RKN resistance. These results suggested that sclareol induced resistance to RKN penetration partially through ET-dependent accumulation of lignin in roots.

  15. Rhizobacterial colonization of roots modulates plant volatile emission and enhances the attraction of a parasitoid wasp to host-infested plants.

    PubMed

    Pangesti, Nurmi; Weldegergis, Berhane T; Langendorf, Benjamin; van Loon, Joop J A; Dicke, Marcel; Pineda, Ana

    2015-08-01

    Beneficial root-associated microbes modify the physiological status of their host plants and affect direct and indirect plant defense against insect herbivores. While the effects of these microbes on direct plant defense against insect herbivores are well described, knowledge of the effect of the microbes on indirect plant defense against insect herbivores is still limited. In this study, we evaluate the role of the rhizobacterium Pseudomonas fluorescens WCS417r in indirect plant defense against the generalist leaf-chewing insect Mamestra brassicae through a combination of behavioral, chemical, and gene-transcriptional approaches. We show that rhizobacterial colonization of Arabidopsis thaliana roots results in an increased attraction of the parasitoid Microplitis mediator to caterpillar-infested plants. Volatile analysis revealed that rhizobacterial colonization suppressed the emission of the terpene (E)-α-bergamotene and the aromatics methyl salicylate and lilial in response to caterpillar feeding. Rhizobacterial colonization decreased the caterpillar-induced transcription of the terpene synthase genes TPS03 and TPS04. Rhizobacteria enhanced both the growth and the indirect defense of plants under caterpillar attack. This study shows that rhizobacteria have a high potential to enhance the biocontrol of leaf-chewing herbivores based on enhanced attraction of parasitoids.

  16. Exogenous malic and acetic acids reduce cadmium phytotoxicity and enhance cadmium accumulation in roots of sunflower plants.

    PubMed

    Hawrylak-Nowak, Barbara; Dresler, Sławomir; Matraszek, Renata

    2015-09-01

    There is increasing evidence showing that low molecular weight organic acids (LMWOA) are involved in heavy metal resistance mechanisms in plants. The aim of this study was to investigate the effects of exogenous malic (MA) or acetic (AA) acids on the toxicity and accumulation of cadmium (Cd) in sunflower (Helianthus annuus L.). For this purpose, plants were grown in hydroponics under controlled conditions. Single Cd stress (5 μM Cd for 14 days) induced strong phytotoxic effects, as indicated by a decrease in all growth parameters, concentration of photosynthetic pigments, and root activity, as well as a high level of hydrogen peroxide (H2O2) accumulation. Exogenous MA or AA (250 or 500 μM) applied to the Cd-containing medium enhanced the accumulation of Cd by the roots and limited Cd translocation to the shoots. Moreover, the MA or AA applied more or less reduced Cd phytotoxicity by increasing the growth parameters, photosynthetic pigment concentrations, decreasing accumulation of H2O2, and improving the root activity. Of the studied organic acids, MA was much more efficient in mitigation of Cd toxicity than AA, probably by its antioxidant effects, which were stronger than those of AA. Plant response to Cd involved decreased production of endogenous LMWOA, probably as a consequence of severe Cd toxicity. The addition of MA or AA to the medium increased endogenous accumulation of LMWOA, especially in the roots, which could be beneficial for plant metabolism. These results imply that especially MA may be involved in the processes of Cd uptake, translocation, and tolerance in plants.

  17. 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

  18. 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.

  19. Whole transcriptomic analysis of the plant-beneficial rhizobacterium Bacillus amyloliquefaciens SQR9 during enhanced biofilm formation regulated by maize root exudates.

    PubMed

    Zhang, Nan; Yang, Dongqing; Wang, Dandan; Miao, Youzhi; Shao, Jiahui; Zhou, Xuan; Xu, Zhihui; Li, Qing; Feng, Haichao; Li, Shuqing; Shen, Qirong; Zhang, Ruifu

    2015-09-07

    Bacillus amyloliquefaciens SQR9 is a plant growth-promoting rhizobacteria (PGPR) with outstanding abilities to enhance plant growth and to control soil-borne diseases. Root exudates is known to play important roles in plant-microbe interactions. To explore the rhizosphere interactions and plant-beneficial characteristics of SQR9, the complete genome sequence as well as the transcriptome in response to maize root exudates under biofilm-forming conditions were elucidated. Maize root exudates stimulated SQR9 biofilm formation in liquid culture, which is known to be positively correlated with enhanced root colonization. Transcriptional profiling via RNA-sequencing of SQR9 under static conditions indicated that, at 24 h post-inoculation, root exudates stimulated the expression of metabolism-relevant genes, while at 48 h post-inoculation, genes related to extracellular matrix production (tapA-sipW-tasA operon) were activated by root exudates. The individual components in maize root exudates that stimulated biofilm formation included glucose, citric acid, and fumaric acid, which either promoted the growth of SQR9 cells or activated extracellular matrix production. In addition, numerous groups of genes involved in rhizosphere adaptation and in plant-beneficial traits, including plant polysaccharide utilization, cell motility and chemotaxis, secondary antibiotics synthesis clusters, and plant growth promotion-relevant, were identified in the SQR9 genome. These genes also appeared to be induced by the maize root exudates. Enhanced biofilm formation of B. amyloliquefaciens SQR9 by maize root exudates could mainly be attributed to promoting cell growth and to inducing extracellular matrix production. The genomic analysis also highlighted the elements involved in the strain's potential as a PGPR. This study provides useful information for understanding plant-rhizobacteria interactions and hence for promoting the agricultural applications of this strain.

  20. Phytoremediation of Mercury and Organomercurials in Chloroplast Transgenic Plants: Enhanced Root Uptake, Translocation to Shoots, and Volatilization

    PubMed Central

    Hussein, Hussein S.; Ruiz, Oscar N.; Terry, Norman; Daniell, Henry

    2008-01-01

    Transgenic tobacco plants engineered with bacterial merA and merB genes via the chloroplast genome were investigated to study the uptake, translocation of different forms of mercury (Hg) from roots to shoots, and their volatilization. Untransformed plants, regardless of the form of Hg supplied, reached a saturation point at 200 µM of phenylmercuric acetate (PMA) or HgCl2, accumulating Hg concentrations up to 500 µg g−1 with significant reduction in growth. In contrast, chloroplast transgenic lines continued to grow well with Hg concentrations in root tissues up to 2000 µg g−1. Chloroplast transgenic lines accumulated both the organic and inorganic Hg forms to levels surpassing the concentrations found in the soil. The organic-Hg form was absorbed and translocated more efficiently than the inorganic-Hg form in transgenic lines, whereas no such difference was observed in untransformed plants. Chloroplast-transgenic lines showed about 100-fold increase in the efficiency of Hg accumulation in shoots compared to untransformed plants. This is the first report of such high levels of Hg accumulation in green leaves or tissues. Transgenic plants attained a maximum rate of elemental-Hg volatilization in two days when supplied with PMA and in three days when supplied with inorganic-Hg, attaining complete volatilization within a week. The combined expression of merAB via the chloroplast genome enhanced conversion of Hg2+ into Hg,0 conferred tolerance by rapid volatilization and increased uptake of different forms of mercury, surpassing the concentrations found in the soil. These investigations provide novel insights for improvement of plant tolerance and detoxification of mercury. PMID:18200876

  1. Heterologous Expression of Panax ginseng PgTIP1 Confers Enhanced Salt Tolerance of Soybean Cotyledon Hairy Roots, Composite, and Whole Plants.

    PubMed

    An, Jing; Hu, Zhenmin; Che, Benning; Chen, Haiying; Yu, Bingjun; Cai, Weiming

    2017-01-01

    The Panax ginseng TIP gene PgTIP1 was previously demonstrated to have high water channel activity by its heterologous expression in Xenopus laevis oocytes and in yeast; it also plays a significant role in growth of PgTIP1-transgenic Arabidopsis plants under favorable conditions and has enhanced tolerance toward salt and drought treatment. In this work, we first investigated the physiological effects of heterologous PgTIP1 expression in soybean cotyledon hairy roots or composite plants mediated by Agrobacterium rhizogenes toward enhanced salt tolerance. The PgTIP1-transgenic soybean plants mediated by the pollen tube pathway, represented by the lines N and J11, were analyzed at the physiological and molecular levels for enhanced salt tolerance. The results showed that in terms of root-specific heterologous expression, the PgTIP1-transformed soybean cotyledon hairy roots or composite plants displayed superior salt tolerance compared to the empty vector-transformed ones according to the mitigatory effects of hairy root growth reduction, drop in leaf RWC, and rise in REL under salt stress. Additionally, declines in K(+) content, increases in Na(+) content and Na(+)/K(+) ratios in the hairy roots, stems, or leaves were effectively alleviated by PgTIP1-transformation, particularly the stems and leaves of composite soybean plants. At the whole plant level, PgTIP1-trasgenic soybean lines were found to possess stronger root vigor, reduced root and leaf cell membrane damage, increased SOD, POD, CAT, and APX activities, steadily increased leaf Tr, RWC, and Pn values, and smaller declines in chlorophyll and carotenoid content when exposed to salt stress compared to wild type. Moreover, the distribution patterns of Na(+), K(+), and Cl(-) in the roots, stems, and leaves of salt-stressed transgenic plants were readjusted, in that the absorbed Na(+) and Cl(-) were mainly restricted to the roots to reduce their transport to the shoots, and the transport of root-absorbed K(+) to the

  2. Heterologous Expression of Panax ginseng PgTIP1 Confers Enhanced Salt Tolerance of Soybean Cotyledon Hairy Roots, Composite, and Whole Plants

    PubMed Central

    An, Jing; Hu, Zhenmin; Che, Benning; Chen, Haiying; Yu, Bingjun; Cai, Weiming

    2017-01-01

    The Panax ginseng TIP gene PgTIP1 was previously demonstrated to have high water channel activity by its heterologous expression in Xenopus laevis oocytes and in yeast; it also plays a significant role in growth of PgTIP1-transgenic Arabidopsis plants under favorable conditions and has enhanced tolerance toward salt and drought treatment. In this work, we first investigated the physiological effects of heterologous PgTIP1 expression in soybean cotyledon hairy roots or composite plants mediated by Agrobacterium rhizogenes toward enhanced salt tolerance. The PgTIP1-transgenic soybean plants mediated by the pollen tube pathway, represented by the lines N and J11, were analyzed at the physiological and molecular levels for enhanced salt tolerance. The results showed that in terms of root-specific heterologous expression, the PgTIP1-transformed soybean cotyledon hairy roots or composite plants displayed superior salt tolerance compared to the empty vector-transformed ones according to the mitigatory effects of hairy root growth reduction, drop in leaf RWC, and rise in REL under salt stress. Additionally, declines in K+ content, increases in Na+ content and Na+/K+ ratios in the hairy roots, stems, or leaves were effectively alleviated by PgTIP1-transformation, particularly the stems and leaves of composite soybean plants. At the whole plant level, PgTIP1-trasgenic soybean lines were found to possess stronger root vigor, reduced root and leaf cell membrane damage, increased SOD, POD, CAT, and APX activities, steadily increased leaf Tr, RWC, and Pn values, and smaller declines in chlorophyll and carotenoid content when exposed to salt stress compared to wild type. Moreover, the distribution patterns of Na+, K+, and Cl- in the roots, stems, and leaves of salt-stressed transgenic plants were readjusted, in that the absorbed Na+ and Cl- were mainly restricted to the roots to reduce their transport to the shoots, and the transport of root-absorbed K+ to the shoots was

  3. NO synthase-generated NO acts downstream of auxin in regulating Fe-deficiency-induced root branching that enhances Fe-deficiency tolerance in tomato plants

    PubMed Central

    Jin, Chong Wei; Shamsi, Imran Haider; Luo, Bing Fang; Lin, Xian Yong

    2011-01-01

    In response to Fe-deficiency, various dicots increase their root branching which contributes to the enhancement of ferric-chelate reductase activity. Whether this Fe-deficiency-induced response eventually enhances the ability of the plant to tolerate Fe-deficiency or not is still unclear and evidence is also scarce about the signals triggering it. In this study, it was found that the SPAD-chlorophyll meter values of newly developed leaves of four tomato (Solanum lycocarpum) lines, namely line227/1 and Roza and their two reciprocal F1 hybrid lines, were positively correlated with their root branching under Fe-deficient conditions. It indicates that Fe-deficiency-induced root branching is critical for plant tolerance to Fe-deficiency. In another tomato line, Micro-Tom, the increased root branching in Fe-deficient plants was accompanied by the elevation of endogenous auxin and nitric oxide (NO) levels, and was suppressed either by the auxin transport inhibitors NPA and TIBA or the NO scavenger cPTIO. On the other hand, root branching in Fe-sufficient plants was induced either by the auxin analogues NAA and 2,4-D or the NO donors NONOate or SNP. Further, in Fe-deficient plants, NONOate restored the NPA-terminated root branching, but NAA did not affect the cPTIO-terminated root branching. Fe-deficiency-induced root branching was inhibited by the NO-synthase (NOS) inhibitor L-NAME, but was not affected by the nitrate reductase (NR) inhibitor NH4+, tungstate or glycine. Taking all of these findings together, a novel function and signalling pathway of Fe-deficiency-induced root branching is presented where NOS-generated rather than NR-generated NO acts downstream of auxin in regulating this Fe-deficiency-induced response, which enhances the plant tolerance to Fe-deficiency. PMID:21511908

  4. Trade-Offs between Silicon and Phenolic Defenses may Explain Enhanced Performance of Root Herbivores on Phenolic-Rich Plants.

    PubMed

    Frew, Adam; Powell, Jeff R; Sallam, Nader; Allsopp, Peter G; Johnson, Scott N

    2016-08-01

    Phenolic compounds play a role in plant defense against herbivores. For some herbivorous insects, particularly root herbivores, host plants with high phenolic concentrations promote insect performance and tissue consumption. This positive relationship between some insects and phenolics, however, could reflect a negative correlation with other plant defenses acting against insects. Silicon is an important element for plant growth and defense, particularly in grasses, as many grass species take up large amounts of silicon. Negative impact of a high silicon diet on insect herbivore performance has been reported aboveground, but is unreported for belowground herbivores. It has been hypothesized that some silicon accumulating plants exhibit a trade-off between carbon-based defense compounds, such as phenolics, and silicon-based defenses. Here, we investigated the impact of silicon concentrations and total phenolic concentrations in sugarcane roots on the performance of the root-feeding greyback canegrub (Dermolepida albohirtum). Canegrub performance was positively correlated with root phenolics, but negatively correlated with root silicon. We found a negative relationship in the roots between total phenolics and silicon concentrations. This suggests the positive impact of phenolic compounds on some insects may be the effect of lower concentrations of silicon compounds in plant tissue. This is the first demonstration of plant silicon negatively affecting a belowground herbivore.

  5. The Application of Contrast Media for In Vivo Feature Enhancement in X-Ray Computed Tomography of Soil-Grown Plant Roots.

    PubMed

    Keyes, Samuel D; Gostling, Neil J; Cheung, Jessica H; Roose, Tiina; Sinclair, Ian; Marchant, Alan

    2017-06-01

    The use of in vivo X-ray microcomputed tomography (μCT) to study plant root systems has become routine, but is often hampered by poor contrast between roots, soil, soil water, and soil organic matter. In clinical radiology, imaging of poorly contrasting regions is frequently aided by the use of radio-opaque contrast media. In this study, we present evidence for the utility of iodinated contrast media (ICM) in the study of plant root systems using μCT. Different dilutions of an ionic and nonionic ICM (Gastrografin 370 and Niopam 300) were perfused into the aerial vasculature of juvenile pea plants via a leaf flap (Pisum sativum). The root systems were imaged via μCT, and a variety of image-processing approaches used to quantify and compare the magnitude of the contrast enhancement between different regions. Though the treatment did not appear to significantly aid extraction of full root system architectures from the surrounding soil, it did allow the xylem and phloem units of seminal roots and the vascular morphology within rhizobial nodules to be clearly visualized. The nonionic, low-osmolality contrast agent Niopam appeared to be well tolerated by the plant, whereas Gastrografin showed evidence of toxicity. In summary, the use of iodine-based contrast media allows usually poorly contrasting root structures to be visualized nondestructively using X-ray μCT. In particular, the vascular structures of roots and rhizobial nodules can be clearly visualized in situ.

  6. Plant diversity affects behavior of generalist root herbivores, reduces crop damage, and enhances crop yield.

    PubMed

    Staudacher, Karin; Schallhart, Nikolaus; Thalinger, Bettina; Wallinger, Corinna; Juen, Anita; Traugott, Michael

    2013-07-01

    Soil-dwelling pests inflict considerable economic damage in agriculture but are hard to control. A promising strategy to reduce pest pressure on crops is to increase the plant diversity in agroecosystems. This approach, however, demands a sound understanding of species' interactions, which is widely lacking for subterranean herbivore-plant systems. Here, we examine the effects of plant diversification on wireworms, the soil-dwelling larvae of click beetles that threaten crops worldwide. We conducted a field experiment employing plant diversification by adding either wheat or a mix of six associated plants (grasses, legumes, and forbs) between rows of maize to protect it from Agriotes wireworms. Wireworm feeding behavior, dispersal between crop and associated plants, as well as maize damage and yield were examined. The former was assessed combining molecular gut content and stable isotope analysis. The pests were strongly attracted by the associated plants in August, when the crop was most vulnerable, whereas in September, shortly before harvest, this effect occurred only in the plant mix. In maize monoculture, the larvae stayed in the principal crop throughout the season. Larval delta13C signatures revealed that maize feeding was reduced up to sevenfold in wireworms of the vegetationally diversified treatments compared to those of the maize monoculture. These findings were confirmed by molecular analysis, which additionally showed a dietary preference of wireworms for specific plants in the associated plant mix. Compared to the monoculture, maize damage was reduced by 38% and 55% in the wheat and plant mix treatment, which translated into a yield increase of 30% and 38%, respectively. The present findings demonstrate that increasing the plant diversity in agroecosystems provides an effective insurance against soil pests. The underlying mechanisms are the diversion of the pest from the principle crop and a changed feeding behavior. The deployment of diverse mixes of

  7. Combining Enhanced Root and Shoot Growth Reveals Cross Talk between Pathways That Control Plant Organ Size in Arabidopsis1[C][W][OA

    PubMed Central

    Vercruyssen, Liesbeth; Gonzalez, Nathalie; Werner, Tomáš; Schmülling, Thomas; Inzé, Dirk

    2011-01-01

    Functionally distinct Arabidopsis (Arabidopsis thaliana) genes that positively affect root or shoot growth when ectopically expressed were combined to explore the feasibility of enhanced biomass production. Enhanced root growth resulting from cytokinin deficiency was obtained by overexpressing CYTOKININ OXIDASE/DEHYDROGENASE3 (CKX3) under the control of the root-specific PYK10 promoter. Plants harboring the PYK10-CKX3 construct were crossed with four different transgenic lines showing enhanced leaf growth. For all combinations, the phenotypic traits of the individual lines could be combined, resulting in an overall growth increase. Unexpectedly, three out of four combinations had more than additive effects. Both leaf and root growth were synergistically enhanced in plants ectopically expressing CKX3 and BRASSINOSTEROID INSENSITIVE1, indicating cross talk between cytokinins and brassinosteroids. In agreement, treatment of PYK10-CKX3 plants with brassinolide resulted in a dramatic increase in lateral root growth that could not be observed in wild-type plants. Coexpression of CKX3 and the GROWTH-REGULATING FACTOR5 (GRF5) antagonized the effects of GRF5 overexpression, revealing an interplay between cytokinins and GRF5 during leaf cell proliferation. The combined overexpression of CKX3 and GIBBERELLIN 20-OXIDASE1 led to a synergistic increase in leaf growth, suggesting an antagonistic growth control by cytokinins and gibberellins. Only additive effects on root and shoot growth were visible in plants ectopically expressing both CKX3 and ARABIDOPSIS VACUOLAR PYROPHOSPHATASE1, hinting at an independent action mode. Our results show new interactions and contribute to the molecular and physiological understanding of biomass production at the whole plant level. PMID:21205622

  8. On plant roots logical gates.

    PubMed

    Adamatzky, Andrew; Sirakoulis, Georgios Ch; Martínez, Genaro J; Baluška, Frantisek; Mancuso, Stefano

    Theoretical constructs of logical gates implemented with plant roots are morphological computing asynchronous devices. Values of Boolean variables are represented by plant roots. A presence of a plant root at a given site symbolises the logical True, an absence the logical False. Logical functions are calculated via interaction between roots. Two types of two-inputs-two-outputs gates are proposed: a gate 〈x, y〉→〈xy, x+y〉 where root apexes are guided by gravity and a gate 〈x,y〉→〈x¯y,x〉 where root apexes are guided by humidity. We propose a design of binary half-adder based on the gates. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Project Work on Plant Roots.

    ERIC Educational Resources Information Center

    Devonald, V. G.

    1986-01-01

    Methods of investigating plant root growth developed for research purposes can be adopted for student use. Investigations of the effect of water table level and of ethylene concentration are described, and techniques of measuring root growth are explained. (Author/ML)

  10. Project Work on Plant Roots.

    ERIC Educational Resources Information Center

    Devonald, V. G.

    1986-01-01

    Methods of investigating plant root growth developed for research purposes can be adopted for student use. Investigations of the effect of water table level and of ethylene concentration are described, and techniques of measuring root growth are explained. (Author/ML)

  11. Crenarchaeota colonize terrestrial plant roots.

    PubMed

    Simon, H M; Dodsworth, J A; Goodman, R M

    2000-10-01

    Microorganisms that colonize plant roots are recruited from, and in turn contribute substantially to, the vast and virtually uncharacterized phylogenetic diversity of soil microbiota. The diverse, but poorly understood, microorganisms that colonize plant roots mediate mineral transformations and nutrient cycles that are central to biosphere functioning. Here, we report the results of epifluorescence microscopy and culture-independent recovery of small subunit (SSU) ribosomal RNA (rRNA) gene sequences showing that members of a previously reported clade of soil Crenarchaeota colonize both young and senescent plant roots at an unexpectedly high frequency, and are particularly abundant on the latter. Our results indicate that non-thermophilic members of the Archaea inhabit an important terrestrial niche on earth and direct attention to the need for studies that will determine their possible roles in mediating root biology.

  12. Nano titania aided clustering and adhesion of beneficial bacteria to plant roots to enhance crop growth and stress management

    NASA Astrophysics Data System (ADS)

    Palmqvist, N. G. M.; Bejai, S.; Meijer, J.; Seisenbaeva, G. A.; Kessler, V. G.

    2015-05-01

    A novel use of Titania nanoparticles as agents in the nano interface interaction between a beneficial plant growth promoting bacterium (Bacillus amyloliquefaciens UCMB5113) and oilseed rape plants (Brassica napus) for protection against the fungal pathogen Alternaria brassicae is presented. Two different TiO2 nanoparticle material were produced by the Sol-Gel approach, one using the patented Captigel method and the other one applying TiBALDH precursor. The particles were characterized by transmission electron microscopy, thermogravimetric analysis, X-ray diffraction, dynamic light scattering and nano particle tracking analysis. Scanning electron microscopy showed that the bacterium was living in clusters on the roots and the combined energy-dispersive X-ray spectroscopy analysis revealed that titanium was present in these cluster formations. Confocal laser scanning microscopy further demonstrated an increased bacterial colonization of Arabidopsis thaliana roots and a semi-quantitative microscopic assay confirmed an increased bacterial adhesion to the roots. An increased amount of adhered bacteria was further confirmed by quantitative fluorescence measurements. The degree of infection by the fungus was measured and quantified by real-time-qPCR. Results showed that Titania nanoparticles increased adhesion of beneficial bacteria on to the roots of oilseed rape and protected the plants against infection.

  13. Nano titania aided clustering and adhesion of beneficial bacteria to plant roots to enhance crop growth and stress management.

    PubMed

    Palmqvist, N G M; Bejai, S; Meijer, J; Seisenbaeva, G A; Kessler, V G

    2015-05-13

    A novel use of Titania nanoparticles as agents in the nano interface interaction between a beneficial plant growth promoting bacterium (Bacillus amyloliquefaciens UCMB5113) and oilseed rape plants (Brassica napus) for protection against the fungal pathogen Alternaria brassicae is presented. Two different TiO2 nanoparticle material were produced by the Sol-Gel approach, one using the patented Captigel method and the other one applying TiBALDH precursor. The particles were characterized by transmission electron microscopy, thermogravimetric analysis, X-ray diffraction, dynamic light scattering and nano particle tracking analysis. Scanning electron microscopy showed that the bacterium was living in clusters on the roots and the combined energy-dispersive X-ray spectroscopy analysis revealed that titanium was present in these cluster formations. Confocal laser scanning microscopy further demonstrated an increased bacterial colonization of Arabidopsis thaliana roots and a semi-quantitative microscopic assay confirmed an increased bacterial adhesion to the roots. An increased amount of adhered bacteria was further confirmed by quantitative fluorescence measurements. The degree of infection by the fungus was measured and quantified by real-time-qPCR. Results showed that Titania nanoparticles increased adhesion of beneficial bacteria on to the roots of oilseed rape and protected the plants against infection.

  14. Nano titania aided clustering and adhesion of beneficial bacteria to plant roots to enhance crop growth and stress management

    PubMed Central

    Palmqvist, N. G. M.; Bejai, S.; Meijer, J.; Seisenbaeva, G. A.; Kessler, V. G.

    2015-01-01

    A novel use of Titania nanoparticles as agents in the nano interface interaction between a beneficial plant growth promoting bacterium (Bacillus amyloliquefaciens UCMB5113) and oilseed rape plants (Brassica napus) for protection against the fungal pathogen Alternaria brassicae is presented. Two different TiO2 nanoparticle material were produced by the Sol-Gel approach, one using the patented Captigel method and the other one applying TiBALDH precursor. The particles were characterized by transmission electron microscopy, thermogravimetric analysis, X-ray diffraction, dynamic light scattering and nano particle tracking analysis. Scanning electron microscopy showed that the bacterium was living in clusters on the roots and the combined energy-dispersive X-ray spectroscopy analysis revealed that titanium was present in these cluster formations. Confocal laser scanning microscopy further demonstrated an increased bacterial colonization of Arabidopsis thaliana roots and a semi-quantitative microscopic assay confirmed an increased bacterial adhesion to the roots. An increased amount of adhered bacteria was further confirmed by quantitative fluorescence measurements. The degree of infection by the fungus was measured and quantified by real-time-qPCR. Results showed that Titania nanoparticles increased adhesion of beneficial bacteria on to the roots of oilseed rape and protected the plants against infection. PMID:25970693

  15. Root Traits and Phenotyping Strategies for Plant Improvement.

    PubMed

    Paez-Garcia, Ana; Motes, Christy M; Scheible, Wolf-Rüdiger; Chen, Rujin; Blancaflor, Elison B; Monteros, Maria J

    2015-06-15

    Roots are crucial for nutrient and water acquisition and can be targeted to enhance plant productivity under a broad range of growing conditions. A current challenge for plant breeding is the limited ability to phenotype and select for desirable root characteristics due to their underground location. Plant breeding efforts aimed at modifying root traits can result in novel, more stress-tolerant crops and increased yield by enhancing the capacity of the plant for soil exploration and, thus, water and nutrient acquisition. Available approaches for root phenotyping in laboratory, greenhouse and field encompass simple agar plates to labor-intensive root digging (i.e., shovelomics) and soil boring methods, the construction of underground root observation stations and sophisticated computer-assisted root imaging. Here, we summarize root architectural traits relevant to crop productivity, survey root phenotyping strategies and describe their advantages, limitations and practical value for crop and forage breeding programs.

  16. Root Traits and Phenotyping Strategies for Plant Improvement

    PubMed Central

    Paez-Garcia, Ana; Motes, Christy M.; Scheible, Wolf-Rüdiger; Chen, Rujin; Blancaflor, Elison B.; Monteros, Maria J.

    2015-01-01

    Roots are crucial for nutrient and water acquisition and can be targeted to enhance plant productivity under a broad range of growing conditions. A current challenge for plant breeding is the limited ability to phenotype and select for desirable root characteristics due to their underground location. Plant breeding efforts aimed at modifying root traits can result in novel, more stress-tolerant crops and increased yield by enhancing the capacity of the plant for soil exploration and, thus, water and nutrient acquisition. Available approaches for root phenotyping in laboratory, greenhouse and field encompass simple agar plates to labor-intensive root digging (i.e., shovelomics) and soil boring methods, the construction of underground root observation stations and sophisticated computer-assisted root imaging. Here, we summarize root architectural traits relevant to crop productivity, survey root phenotyping strategies and describe their advantages, limitations and practical value for crop and forage breeding programs. PMID:27135332

  17. Tomato transgenic plants expressing hairpin construct of a nematode protease gene conferred enhanced resistance to root-knot nematodes

    PubMed Central

    Dutta, Tushar K.; Papolu, Pradeep K.; Banakar, Prakash; Choudhary, Divya; Sirohi, Anil; Rao, Uma

    2015-01-01

    Root-knot nematodes (Meloidogyne incognita) cause substantial yield losses in vegetables worldwide, and are difficult to manage. Continuous withdrawal of environmentally-harmful nematicides from the global market warrants the need for novel nematode management strategies. Utility of host-delivered RNAi has been demonstrated in several plants (Arabidopsis, tobacco, and soybean) that exhibited resistance against root-knot and cyst nematodes. Herein, a M. incognita-specific protease gene, cathepsin L cysteine proteinase (Mi-cpl-1), was targeted to generate tomato transgenic lines to evaluate the genetically modified nematode resistance. In vitro knockdown of Mi-cpl-1 gene led to the reduced attraction and penetration of M. incognita in tomato, suggesting the involvement of Mi-cpl-1 in nematode parasitism. Transgenic expression of the RNAi construct of Mi-cpl-1 gene resulted in 60–80% reduction in infection and multiplication of M. incognita in tomato. Evidence for in vitro and in vivo silencing of Mi-cpl-1 was confirmed by expression analysis using quantitative PCR. Our study demonstrates that Mi-cpl-1 plays crucial role during plant-nematode interaction and plant-mediated downregulation of this gene elicits detrimental effect on M. incognita development, reinforcing the potential of RNAi technology for management of phytonematodes in crop plants. PMID:25883594

  18. Swarming behavior in plant roots.

    PubMed

    Ciszak, Marzena; Comparini, Diego; Mazzolai, Barbara; Baluska, Frantisek; Arecchi, F Tito; Vicsek, Tamás; Mancuso, Stefano

    2012-01-01

    Interactions between individuals that are guided by simple rules can generate swarming behavior. Swarming behavior has been observed in many groups of organisms, including humans, and recent research has revealed that plants also demonstrate social behavior based on mutual interaction with other individuals. However, this behavior has not previously been analyzed in the context of swarming. Here, we show that roots can be influenced by their neighbors to induce a tendency to align the directions of their growth. In the apparently noisy patterns formed by growing roots, episodic alignments are observed as the roots grow close to each other. These events are incompatible with the statistics of purely random growth. We present experimental results and a theoretical model that describes the growth of maize roots in terms of swarming.

  19. Economic strategies of plant absorptive roots vary with root diameter

    NASA Astrophysics Data System (ADS)

    Kong, D. L.; Wang, J. J.; Kardol, P.; Wu, H. F.; Zeng, H.; Deng, X. B.; Deng, Y.

    2016-01-01

    Plant roots typically vary along a dominant ecological axis, the root economics spectrum, depicting a tradeoff between resource acquisition and conservation. For absorptive roots, which are mainly responsible for resource acquisition, we hypothesized that root economic strategies differ with increasing root diameter. To test this hypothesis, we used seven plant species (a fern, a conifer, and five angiosperms from south China) for which we separated absorptive roots into two categories: thin roots (thickness of root cortex plus epidermis < 247 µm) and thick roots. For each category, we analyzed a range of root traits related to resource acquisition and conservation, including root tissue density, different carbon (C), and nitrogen (N) fractions (i.e., extractive, acid-soluble, and acid-insoluble fractions) as well as root anatomical traits. The results showed significant relationships among root traits indicating an acquisition-conservation tradeoff for thin absorptive roots while no such trait relationships were found for thick absorptive roots. Similar results were found when reanalyzing data of a previous study including 96 plant species. The contrasting economic strategies between thin and thick absorptive roots, as revealed here, may provide a new perspective on our understanding of the root economics spectrum.

  20. Root formation in ethylene-insensitive plants.

    PubMed

    Clark, D G; Gubrium, E K; Barrett, J E; Nell, T A; Klee, H J

    1999-09-01

    Experiments with ethylene-insensitive tomato (Lycopersicon esculentum) and petunia (Petunia x hybrida) plants were conducted to determine if normal or adventitious root formation is affected by ethylene insensitivity. Ethylene-insensitive Never ripe (NR) tomato plants produced more below-ground root mass but fewer above-ground adventitious roots than wild-type Pearson plants. Applied auxin (indole-3-butyric acid) increased adventitious root formation on vegetative stem cuttings of wild-type plants but had little or no effect on rooting of NR plants. Reduced adventitious root formation was also observed in ethylene-insensitive transgenic petunia plants. Applied 1-aminocyclopropane-1-carboxylic acid increased adventitious root formation on vegetative stem cuttings from NR and wild-type plants, but NR cuttings produced fewer adventitious roots than wild-type cuttings. These data suggest that the promotive effect of auxin on adventitious rooting is influenced by ethylene responsiveness. Seedling root growth of tomato in response to mechanical impedance was also influenced by ethylene sensitivity. Ninety-six percent of wild-type seedlings germinated and grown on sand for 7 d grew normal roots into the medium, whereas 47% of NR seedlings displayed elongated tap-roots, shortened hypocotyls, and did not penetrate the medium. These data indicate that ethylene has a critical role in various responses of roots to environmental stimuli.

  1. 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

  2. Plant growth-promoting rhizobacteria and root system functioning.

    PubMed

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

    2013-09-17

    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.

  3. Root exudates mediate kin recognition in plants

    PubMed Central

    Biedrzycki, Meredith L; Jilany, Tafari A

    2010-01-01

    Though recent work has demonstrated that plants can recognize species, kin versus strangers, and self/non-self roots, no mechanism for identity recognition in plants has yet been found. Here we examined the role of soluble chemicals in signaling among roots. Utilizing Arabidopsis thaliana, we exposed young seedlings to liquid media containing exudates from siblings, strangers (non-siblings), or only their own exudates. In one experiment, root secretions were inhibited by sodium orthovanadate and root length and number of lateral roots were measured. In a second experiment, responses to siblings, strangers, and their own exudates were measured for several accessions (genotypes), and the traits of length of the longest lateral root and hypocotyl length were also measured. The exposure of plants to the root exudates of strangers induced greater lateral root formation than exposure of plants to sibling exudates. Stranger recognition was abolished upon treatment with the secretion inhibitor. In one experiment, plants exposed to sibling or stranger exudates have shorter roots than plants only exposed to their own exudates. This self/non-self recognition response was not affected by the secretion inhibitor. The results demonstrate that that kin recognition and self/non-self are two separate identity recognition systems involving soluble chemicals. Kin recognition requires active secretion by roots. PMID:20539778

  4. Root exudates mediate kin recognition in plants.

    PubMed

    Biedrzycki, Meredith L; Jilany, Tafari A; Dudley, Susan A; Bais, Harsh P

    2010-01-01

    Though recent work has demonstrated that plants can recognize species, kin versus strangers, and self/non-self roots, no mechanism for identity recognition in plants has yet been found. Here we examined the role of soluble chemicals in signaling among roots. Utilizing Arabidopsis thaliana, we exposed young seedlings to liquid media containing exudates from siblings, strangers (non-siblings), or only their own exudates. In one experiment, root secretions were inhibited by sodium orthovanadate and root length and number of lateral roots were measured. In a second experiment, responses to siblings, strangers, and their own exudates were measured for several accessions (genotypes), and the traits of length of the longest lateral root and hypocotyl length were also measured. The exposure of plants to the root exudates of strangers induced greater lateral root formation than exposure of plants to sibling exudates. Stranger recognition was abolished upon treatment with the secretion inhibitor. In one experiment, plants exposed to sibling or stranger exudates have shorter roots than plants only exposed to their own exudates. This self/non-self recognition response was not affected by the secretion inhibitor. The results demonstrate that that kin recognition and self/non-self are two separate identity recognition systems involving soluble chemicals. Kin recognition requires active secretion by roots.

  5. Earliest rooting system and root : shoot ratio from a new Zosterophyllum plant.

    PubMed

    Hao, Shougang; Xue, Jinzhuang; Guo, Dali; Wang, Deming

    2010-01-01

    The enhanced chemical weathering by rooted vascular plants during the Silurian-Devonian period played a crucial role in altering global biogeochemical cycles and atmospheric environments; however, the documentation of early root morphology and physiology is scarce because the existing fossils are mostly incomplete. Here, we report an entire, uprooted specimen of a new Zosterophyllum Penhallow, named as Z. shengfengense, from the Early Devonian Xitun Formation (Lochkovian, c. 413 Myr old) of Yunnan, south China. This plant has the most ancient known record of a rooting system. The plant consists of aerial axes of 98 mm in height, showing a tufted habit, and a rhizome bearing a fibrous-like rooting system, c. 20 mm in length. The rhizome shows masses of branchings, which produce upwardly directed aerial axes and downwardly directed root-like axes. The completeness of Z. shengfengense made it possible to estimate the biomass allocation and root : shoot ratio. The root : shoot ratio of this early plant is estimated at a mean value of 0.028, and the root-like axes constitute only c. 3% of the total biomass. Zosterophyllum shengfengense was probably a semi-aquatic plant with efficient water use or a strong uptake capacity of the root-like axes.

  6. Overexpression of AtHMA4 enhances root-to-shoot translocation of zinc and cadmium and plant metal tolerance.

    PubMed

    Verret, Frédéric; Gravot, Antoine; Auroy, Pascaline; Leonhardt, Nathalie; David, Pascale; Nussaume, Laurent; Vavasseur, Alain; Richaud, Pierre

    2004-10-22

    AtHMA4 is an Arabidopsis thaliana P1B-ATPase which transports Zn and Cd. Here, we demonstrate that AtHMA4 is localized at the plasma membrane and expressed in tissues surrounding the root vascular vessels. The ectopic overexpression of AtHMA4 improved the root growth in the presence of toxic concentrations of Zn, Cd and Co. A null mutant exhibited a lower translocation of Zn and Cd from the roots to shoot. In contrast, the AtHMA4 overexpressing lines displayed an increase in the zinc and cadmium shoot content. Altogether, these results strongly indicate that AtHMA4 plays a role in metal loading in the xylem.

  7. [Effects and mechanisms of plant roots on slope reinforcement and soil erosion resistance: a research review].

    PubMed

    Xiong, Yan-Mei; Xia, Han-Ping; Li, Zhi-An; Cai, Xi-An

    2007-04-01

    Plant roots play an important role in resisting the shallow landslip and topsoil erosion of slopes by raising soil shear strength. Among the models in interpreting the mechanisms of slope reinforcement by plant roots, Wu-Waldron model is a widely accepted one. In this model, the reinforced soil strength by plant roots is positively proportional to average root tensile strength and root area ratio, the two most important factors in evaluating slope reinforcement effect of plant roots. It was found that soil erosion resistance increased with the number of plant roots, though no consistent quantitative functional relationship was observed between them. The increase of soil erosion resistance by plant roots was mainly through the actions of fiber roots less than 1 mm in diameter, while fiber roots enhanced the soil stability to resist water dispersion via increasing the number and diameter of soil water-stable aggregates. Fine roots could also improve soil permeability effectively to decrease runoff and weaken soil erosion.

  8. Apoplastic interactions between plants and plant root intruders.

    PubMed

    Mitsumasu, Kanako; Seto, Yoshiya; Yoshida, Satoko

    2015-01-01

    Numerous pathogenic or parasitic organisms attack plant roots to obtain nutrients, and the apoplast including the plant cell wall is where the plant cell meets such organisms. Root parasitic angiosperms and nematodes are two distinct types of plant root parasites but share some common features in their strategies for breaking into plant roots. Striga and Orobanche are obligate root parasitic angiosperms that cause devastating agricultural problems worldwide. Parasitic plants form an invasion organ called a haustorium, where plant cell wall degrading enzymes (PCWDEs) are highly expressed. Plant-parasitic nematodes are another type of agriculturally important plant root parasite. These nematodes breach the plant cell walls by protruding a sclerotized stylet from which PCWDEs are secreted. Responding to such parasitic invasion, host plants activate their own defense responses against parasites. Endoparasitic nematodes secrete apoplastic effectors to modulate host immune responses and to facilitate the formation of a feeding site. Apoplastic communication between hosts and parasitic plants also contributes to their interaction. Parasitic plant germination stimulants, strigolactones, are recently identified apoplastic signals that are transmitted over long distances from biosynthetic sites to functioning sites. Here, we discuss recent advances in understanding the importance of apoplastic signals and cell walls for plant-parasite interactions.

  9. Apoplastic interactions between plants and plant root intruders

    PubMed Central

    Mitsumasu, Kanako; Seto, Yoshiya; Yoshida, Satoko

    2015-01-01

    Numerous pathogenic or parasitic organisms attack plant roots to obtain nutrients, and the apoplast including the plant cell wall is where the plant cell meets such organisms. Root parasitic angiosperms and nematodes are two distinct types of plant root parasites but share some common features in their strategies for breaking into plant roots. Striga and Orobanche are obligate root parasitic angiosperms that cause devastating agricultural problems worldwide. Parasitic plants form an invasion organ called a haustorium, where plant cell wall degrading enzymes (PCWDEs) are highly expressed. Plant-parasitic nematodes are another type of agriculturally important plant root parasite. These nematodes breach the plant cell walls by protruding a sclerotized stylet from which PCWDEs are secreted. Responding to such parasitic invasion, host plants activate their own defense responses against parasites. Endoparasitic nematodes secrete apoplastic effectors to modulate host immune responses and to facilitate the formation of a feeding site. Apoplastic communication between hosts and parasitic plants also contributes to their interaction. Parasitic plant germination stimulants, strigolactones, are recently identified apoplastic signals that are transmitted over long distances from biosynthetic sites to functioning sites. Here, we discuss recent advances in understanding the importance of apoplastic signals and cell walls for plant–parasite interactions. PMID:26322059

  10. Sporulation on plant roots by Phytophthora ramorum

    USDA-ARS?s Scientific Manuscript database

    Phytophthora ramorum has been shown to infect the roots of many of the pathogen’s foliar hosts. Methods of detecting inoculum in runoff and of quantifying root colonization were tested using Viburnum tinus, Camellia oleifera, Quercus prinus, Umbellularia californica, and Epilobium ciliatum. Plants...

  11. Plant root-microbe communication in shaping root microbiomes.

    PubMed

    Lareen, Andrew; Burton, Frances; Schäfer, Patrick

    2016-04-01

    A growing body of research is highlighting the impacts root-associated microbial communities can have on plant health and development. These impacts can include changes in yield quantity and quality, timing of key developmental stages and tolerance of biotic and abiotic stresses. With such a range of effects it is clear that understanding the factors that contribute to a plant-beneficial root microbiome may prove advantageous. Increasing demands for food by a growing human population increases the importance and urgency of understanding how microbiomes may be exploited to increase crop yields and reduce losses caused by disease. In addition, climate change effects may require novel approaches to overcoming abiotic stresses such as drought and salinity as well as new emerging diseases. This review discusses current knowledge on the formation and maintenance of root-associated microbial communities and plant-microbe interactions with a particular emphasis on the effect of microbe-microbe interactions on the shape of microbial communities at the root surface. Further, we discuss the potential for root microbiome modification to benefit agriculture and food production.

  12. Plant Hormones: How They Affect Root Formation.

    ERIC Educational Resources Information Center

    Reinhard, Diana Hereda

    This science study aid, produced by the U.S. Department of Agriculture, includes a series of plant rooting activities for secondary science classes. The material in the pamphlet is written for students and includes background information on plant hormones, a vocabulary list, and five learning activities. Objectives, needed materials, and…

  13. Microbial products trigger amino acid exudation from plant roots.

    PubMed

    Phillips, Donald A; Fox, Tama C; King, Maria D; Bhuvaneswari, T V; Teuber, Larry R

    2004-09-01

    Plants naturally cycle amino acids across root cell plasma membranes, and any net efflux is termed exudation. The dominant ecological view is that microorganisms and roots passively compete for amino acids in the soil solution, yet the innate capacity of roots to recover amino acids present in ecologically relevant concentrations is unknown. We find that, in the absence of culturable microorganisms, the influx rates of 16 amino acids (each supplied at 2.5 microm) exceed efflux rates by 5% to 545% in roots of alfalfa (Medicago sativa), Medicago truncatula, maize (Zea mays), and wheat (Triticum aestivum). Several microbial products, which are produced by common soil microorganisms such as Pseudomonas bacteria and Fusarium fungi, significantly enhanced the net efflux (i.e. exudation) of amino acids from roots of these four plant species. In alfalfa, treating roots with 200 microm phenazine, 2,4-diacetylphloroglucinol, or zearalenone increased total net efflux of 16 amino acids 200% to 2,600% in 3 h. Data from (15)N tests suggest that 2,4-diacetylphloroglucinol blocks amino acid uptake, whereas zearalenone enhances efflux. Thus, amino acid exudation under normal conditions is a phenomenon that probably reflects both active manipulation and passive uptake by microorganisms, as well as diffusion and adsorption to soil, all of which help overcome the innate capacity of plant roots to reabsorb amino acids. The importance of identifying potential enhancers of root exudation lies in understanding that such compounds may represent regulatory linkages between the larger soil food web and the internal carbon metabolism of the plant.

  14. D-Root: a system for cultivating plants with the roots in darkness or under different light conditions.

    PubMed

    Silva-Navas, Javier; Moreno-Risueno, Miguel A; Manzano, Concepción; Pallero-Baena, Mercedes; Navarro-Neila, Sara; Téllez-Robledo, Bárbara; Garcia-Mina, Jose M; Baigorri, Roberto; Gallego, Francisco Javier; del Pozo, Juan C

    2015-10-01

    In nature roots grow in the dark and away from light (negative phototropism). However, most current research in root biology has been carried out with the root system grown in the presence of light. Here, we have engineered a device, called Dark-Root (D-Root), to grow plants in vitro with the aerial part exposed to the normal light/dark photoperiod while the roots are in the dark or exposed to specific wavelengths or light intensities. D-Root provides an efficient system for cultivating a large number of seedlings and easily characterizing root architecture in the dark. At the morphological level, root illumination shortens root length and promotes early emergence of lateral roots, therefore inducing expansion of the root system. Surprisingly, root illumination also affects shoot development, including flowering time. Our analyses also show that root illumination alters the proper response to hormones or abiotic stress (e.g. salt or osmotic stress) and nutrient starvation, enhancing inhibition of root growth. In conclusion, D-Root provides a growing system closer to the natural one for assaying Arabidopsis plants, and therefore its use will contribute to a better understanding of the mechanisms involved in root development, hormonal signaling and stress responses.

  15. Trichoderma virens, a Plant Beneficial Fungus, Enhances Biomass Production and Promotes Lateral Root Growth through an Auxin-Dependent Mechanism in Arabidopsis1[C][W][OA

    PubMed Central

    Contreras-Cornejo, Hexon Angel; Macías-Rodríguez, Lourdes; Cortés-Penagos, Carlos; López-Bucio, José

    2009-01-01

    Trichoderma species belong to a class of free-living fungi beneficial to plants that are common in the rhizosphere. We investigated the role of auxin in regulating the growth and development of Arabidopsis (Arabidopsis thaliana) seedlings in response to inoculation with Trichoderma virens and Trichoderma atroviride by developing a plant-fungus interaction system. Wild-type Arabidopsis seedlings inoculated with either T. virens or T. atroviride showed characteristic auxin-related phenotypes, including increased biomass production and stimulated lateral root development. Mutations in genes involved in auxin transport or signaling, AUX1, BIG, EIR1, and AXR1, were found to reduce the growth-promoting and root developmental effects of T. virens inoculation. When grown under axenic conditions, T. virens produced the auxin-related compounds indole-3-acetic acid, indole-3-acetaldehyde, and indole-3-ethanol. A comparative analysis of all three indolic compounds provided detailed information about the structure-activity relationship based on their efficacy at modulating root system architecture, activation of auxin-regulated gene expression, and rescue of the root hair-defective phenotype of the rhd6 auxin response Arabidopsis mutant. Our results highlight the important role of auxin signaling for plant growth promotion by T. virens. PMID:19176721

  16. Overexpression of Elsholtzia haichowensis metallothionein 1 (EhMT1) in tobacco plants enhances copper tolerance and accumulation in root cytoplasm and decreases hydrogen peroxide production.

    PubMed

    Xia, Yan; Qi, Ying; Yuan, Yuxiang; Wang, Guiping; Cui, Jin; Chen, Yahua; Zhang, Hongsheng; Shen, Zhenguo

    2012-09-30

    To evaluate the functional roles of metallothionein (MT) in copper tolerance, we generated transgenic tobacco plants overexpressing EhMT1 from the Cu-accumulator Elsholtzia haichowensis Sun. Overexpression of EhMT1 in tobacco plants imparted increased copper (Cu) tolerance based on seedling dry biomass when compared to wild-type plants. Plants expressing EhMT1 accumulated more Cu in roots, which was mainly attributable to an increase of the soluble fraction. Levels of lipid peroxidation and production of hydrogen peroxide were lower in roots of transgenic tobacco than in wild-type plants. EhMT1 was suggested to bind Cu in the cytoplasm, thereby decreasing activity of free Cu(2+) ions and blocking Cu(2+) from interacting with cytoplasmic components, which in turn decreases the production of reactive oxygen species. In addition, our results also indicate that EhMT1-overexpressing tobacco has a more efficient antioxidant system, with improved peroxidase activity to better cope with oxidative stress. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Assembly line plants take root

    SciTech Connect

    Comis, D.; Wood, M.

    1986-04-01

    This paper discussed tissue-culture propagation of sugarcane, apple trees, peach trees, citrus, orchids, data palms, and carrots. Tissue-culture propagation is a term used for a variety of techniques used to grow or genetically modify, preserve, or study plant parts in laboratories, from tissue or even a single cell. The author examined the benefits and commercial applications of this propagation process.

  18. Fate of polycyclic aromatic hydrocarbons in plant-soil systems: Plant responses to a chemical stress in the root zone

    SciTech Connect

    Hoylman, Anne M.

    1994-01-01

    Under laboratory conditions selected to maximize root uptake, plant tissue distribution of PAH-derived 14C was largely limited to root tissue of Malilotus alba. These results suggest that plant uptake of PAHs from contaminated soil via roots, and translocation to aboveground plant tissues (stems and leaves), is a limited mechanism for transport into terrestrial food chains. However, these data also indicate that root surface sorption of PAHs may be important for plants grown in soils containing elevated concentration PAHs. Root surface sorption of PAHs may be an important route of exposure for plants in soils containing elevated concentrations of PAHS. Consequently, the root-soil interface may be the site of plant-microbial interactions in response to a chemical stress. In this study, evidence of a shift in carbon allocation to the root zone of plants exposed to phenanthrene and corresponding increases in soil respiration and heterotrophic plate counts provide evidence of a plant-microbial response to a chemical stress. The results of this study establish the importance of the root-soil interface for plants growing in PAH contaminated soil and indicate the existence of plant-microbial interactions in response to a chemical stress. These results may provide new avenues of inquiry for studies of plant toxicology, plant-microbial interactions in the rhizosphere, and environmental fates of soil contaminants. In addition, the utilization of plants to enhance the biodegradation of soil contaminants may require evaluation of plant physiological changes and plant shifts in resource allocation.

  19. Root biomass and exudates link plant diversity with soil bacterial and fungal biomass

    PubMed Central

    Eisenhauer, Nico; Lanoue, Arnaud; Strecker, Tanja; Scheu, Stefan; Steinauer, Katja; Thakur, Madhav P.; Mommer, Liesje

    2017-01-01

    Plant diversity has been shown to determine the composition and functioning of soil biota. Although root-derived organic inputs are discussed as the main drivers of soil communities, experimental evidence is scarce. While there is some evidence that higher root biomass at high plant diversity increases substrate availability for soil biota, several studies have speculated that the quantity and diversity of root inputs into the soil, i.e. though root exudates, drive plant diversity effects on soil biota. Here we used a microcosm experiment to study the role of plant species richness on the biomass of soil bacteria and fungi as well as fungal-to-bacterial ratio via root biomass and root exudates. Plant diversity significantly increased shoot biomass, root biomass, the amount of root exudates, bacterial biomass, and fungal biomass. Fungal biomass increased most with increasing plant diversity resulting in a significant shift in the fungal-to-bacterial biomass ratio at high plant diversity. Fungal biomass increased significantly with plant diversity-induced increases in root biomass and the amount of root exudates. These results suggest that plant diversity enhances soil microbial biomass, particularly soil fungi, by increasing root-derived organic inputs. PMID:28374800

  20. Root biomass and exudates link plant diversity with soil bacterial and fungal biomass.

    PubMed

    Eisenhauer, Nico; Lanoue, Arnaud; Strecker, Tanja; Scheu, Stefan; Steinauer, Katja; Thakur, Madhav P; Mommer, Liesje

    2017-04-04

    Plant diversity has been shown to determine the composition and functioning of soil biota. Although root-derived organic inputs are discussed as the main drivers of soil communities, experimental evidence is scarce. While there is some evidence that higher root biomass at high plant diversity increases substrate availability for soil biota, several studies have speculated that the quantity and diversity of root inputs into the soil, i.e. though root exudates, drive plant diversity effects on soil biota. Here we used a microcosm experiment to study the role of plant species richness on the biomass of soil bacteria and fungi as well as fungal-to-bacterial ratio via root biomass and root exudates. Plant diversity significantly increased shoot biomass, root biomass, the amount of root exudates, bacterial biomass, and fungal biomass. Fungal biomass increased most with increasing plant diversity resulting in a significant shift in the fungal-to-bacterial biomass ratio at high plant diversity. Fungal biomass increased significantly with plant diversity-induced increases in root biomass and the amount of root exudates. These results suggest that plant diversity enhances soil microbial biomass, particularly soil fungi, by increasing root-derived organic inputs.

  1. The evolutionary root of flowering plants.

    PubMed

    Goremykin, Vadim V; Nikiforova, Svetlana V; Biggs, Patrick J; Zhong, Bojian; Delange, Peter; Martin, William; Woetzel, Stefan; Atherton, Robin A; McLenachan, Patricia A; Lockhart, Peter J

    2013-01-01

    Correct rooting of the angiosperm radiation is both challenging and necessary for understanding the origins and evolution of physiological and phenotypic traits in flowering plants. The problem is known to be difficult due to the large genetic distance separating flowering plants from other seed plants and the sparse taxon sampling among basal angiosperms. Here, we provide further evidence for concern over substitution model misspecification in analyses of chloroplast DNA sequences. We show that support for Amborella as the sole representative of the most basal angiosperm lineage is founded on sequence site patterns poorly described by time-reversible substitution models. Improving the fit between sequence data and substitution model identifies Trithuria, Nymphaeaceae, and Amborella as surviving relatives of the most basal lineage of flowering plants. This finding indicates that aquatic and herbaceous species dominate the earliest extant lineage of flowering plants. [; ; ; ; ; .].

  2. Root exudates of mycorrhizal tomato plants exhibit a different effect on microconidia germination of Fusarium oxysporum f. sp. lycopersici than root exudates from non-mycorrhizal tomato plants.

    PubMed

    Scheffknecht, S; Mammerler, R; Steinkellner, S; Vierheilig, H

    2006-07-01

    The effect of root exudates from mycorrhizal and non-mycorrhizal tomato plants on microconidia germination of the tomato pathogen Fusarium oxysporum f. sp. lycopersici was tested. Microconidia germination was enhanced in the presence of root exudates from mycorrhizal tomato plants. The more tomato plants were colonized by the arbuscular mycorrhizal fungus Glomus mosseae, the more microconidia germination was increased, indicating that alterations of the exudation pattern depended on the degree of root AM colonization. Moreover, alterations of the exudation pattern of mycorrhizal plants are not only local, but also systemic. Testing the exudates from plants with a high and a low P level revealed that the alterations of the root exudates from mycorrhizal plants, resulting in a changed effect on microconidia germination, are not due to an improved P status of mycorrhizal plants.

  3. Carbon allocation to root and shoot systems of woody plants

    Treesearch

    Alexander L. Friend; 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...

  4. [Medicinal plant hairy roots generating and their applications].

    PubMed

    Zhang, Meng; Gao, Wei; Wang, Xiu-Juan

    2014-06-01

    As a kind of the plant tissue cultures, hairy root culture is characterized by rapid growth without exogenous hormones source and high yield of secondary metabolites, which attracted the attention of scholars in resent years. This work systematically summarized the research of medicinal plant hairy roots, including the mechanism, current situation of medicinal plant hairy roots, and their applications.

  5. Light perception in aerial tissues enhances DWF4 accumulation in root tips and induces root growth.

    PubMed

    Sakaguchi, Jun; Watanabe, Yuichiro

    2017-05-12

    Many attempts have been made to characterize the activities of brassinosteroids (BRs), which are important plant hormones. The crosstalk between light perception and the BR signalling pathway has been extensively studied regarding its effects on photomorphogenesis, especially in elongating etiolated hypocotyls. In contrast, how and where the light induces BR biosynthesis remain uncharacterized. DWF4 is one of the main enzymes involved in the BR biosynthesis pathway in Arabidopsis thaliana. We established DWF4-GUS A. thaliana lines in a homozygous dwf4-102 genetic background, but functionally complemented with a genomic DWF4 sequence fused in-frame with a β-glucuronidase (GUS) marker gene. The DWF4-GUS plants enabled the visualization of the accumulation of DWF4 under different conditions. We investigated the effects of aboveground light on root and hypocotyl growth. We observed that root length increased when shoots were maintained under light irrespective of whether roots were exposed to light. We also determined that light perception in aerial tissues enhanced DWF4 accumulation in the root tips. Overall, our data indicate that BR biosynthesis is promoted in the root tip regions by an unknown mechanism in distantly located shoot tissues exposed to light, leading to increased root growth.

  6. Functional traits and root morphology of alpine plants

    PubMed Central

    Pohl, Mandy; Stroude, Raphaël; Buttler, Alexandre; Rixen, Christian

    2011-01-01

    Background and Aims Vegetation has long been recognized to protect the soil from erosion. Understanding species differences in root morphology and functional traits is an important step to assess which species and species mixtures may provide erosion control. Furthermore, extending classification of plant functional types towards root traits may be a useful procedure in understanding important root functions. Methods In this study, pioneer data on traits of alpine plant species, i.e. plant height and shoot biomass, root depth, horizontal root spreading, root length, diameter, tensile strength, plant age and root biomass, from a disturbed site in the Swiss Alps are presented. The applicability of three classifications of plant functional types (PFTs), i.e. life form, growth form and root type, was examined for above- and below-ground plant traits. Key Results Plant traits differed considerably among species even of the same life form, e.g. in the case of total root length by more than two orders of magnitude. Within the same root diameter, species differed significantly in tensile strength: some species (Geum reptans and Luzula spicata) had roots more than twice as strong as those of other species. Species of different life forms provided different root functions (e.g. root depth and horizontal root spreading) that may be important for soil physical processes. All classifications of PFTs were helpful to categorize plant traits; however, the PFTs according to root type explained total root length far better than the other PFTs. Conclusions The results of the study illustrate the remarkable differences between root traits of alpine plants, some of which cannot be assessed from simple morphological inspection, e.g. tensile strength. PFT classification based on root traits seems useful to categorize plant traits, even though some patterns are better explained at the individual species level. PMID:21795278

  7. Functional traits and root morphology of alpine plants.

    PubMed

    Pohl, Mandy; Stroude, Raphaël; Buttler, Alexandre; Rixen, Christian

    2011-09-01

    Vegetation has long been recognized to protect the soil from erosion. Understanding species differences in root morphology and functional traits is an important step to assess which species and species mixtures may provide erosion control. Furthermore, extending classification of plant functional types towards root traits may be a useful procedure in understanding important root functions. In this study, pioneer data on traits of alpine plant species, i.e. plant height and shoot biomass, root depth, horizontal root spreading, root length, diameter, tensile strength, plant age and root biomass, from a disturbed site in the Swiss Alps are presented. The applicability of three classifications of plant functional types (PFTs), i.e. life form, growth form and root type, was examined for above- and below-ground plant traits. Plant traits differed considerably among species even of the same life form, e.g. in the case of total root length by more than two orders of magnitude. Within the same root diameter, species differed significantly in tensile strength: some species (Geum reptans and Luzula spicata) had roots more than twice as strong as those of other species. Species of different life forms provided different root functions (e.g. root depth and horizontal root spreading) that may be important for soil physical processes. All classifications of PFTs were helpful to categorize plant traits; however, the PFTs according to root type explained total root length far better than the other PFTs. The results of the study illustrate the remarkable differences between root traits of alpine plants, some of which cannot be assessed from simple morphological inspection, e.g. tensile strength. PFT classification based on root traits seems useful to categorize plant traits, even though some patterns are better explained at the individual species level.

  8. Enhanced gravitropism of roots with a disrupted cap actin cytoskeleton

    NASA Technical Reports Server (NTRS)

    Hou, Guichuan; Mohamalawari, Deepti R.; Blancaflor, Elison B.

    2003-01-01

    The actin cytoskeleton has been proposed to be a major player in plant gravitropism. However, understanding the role of actin in this process is far from complete. To address this problem, we conducted an analysis of the effect of Latrunculin B (Lat B), a potent actin-disrupting drug, on root gravitropism using various parameters that included detailed curvature kinetics, estimation of gravitropic sensitivity, and monitoring of curvature development after extended clinorotation. Lat B treatment resulted in a promotion of root curvature after a 90 degrees reorientation in three plant species tested. More significantly, the sensitivity of maize (Zea mays) roots to gravity was enhanced after actin disruption, as determined from a comparison of presentation time of Lat B-treated versus untreated roots. A short 10-min gravistimulus followed by extended rotation on a 1-rpm clinostat resulted in extensive gravitropic responses, manifested as curvature that often exceeded 90 degrees. Application of Lat B to the cap or elongation zone of maize roots resulted in the disruption of the actin cytoskeleton, which was confined to the area of localized Lat B application. Only roots with Lat B applied to the cap displayed the strong curvature responses after extended clinorotation. Our study demonstrates that disrupting the actin cytoskeleton in the cap leads to the persistence of a signal established by a previous gravistimulus. Therefore, actin could function in root gravitropism by providing a mechanism to regulate the proliferation of a gravitropic signal originating from the cap to allow the root to attain its correct orientation or set point angle.

  9. Enhanced gravitropism of roots with a disrupted cap actin cytoskeleton

    NASA Technical Reports Server (NTRS)

    Hou, Guichuan; Mohamalawari, Deepti R.; Blancaflor, Elison B.

    2003-01-01

    The actin cytoskeleton has been proposed to be a major player in plant gravitropism. However, understanding the role of actin in this process is far from complete. To address this problem, we conducted an analysis of the effect of Latrunculin B (Lat B), a potent actin-disrupting drug, on root gravitropism using various parameters that included detailed curvature kinetics, estimation of gravitropic sensitivity, and monitoring of curvature development after extended clinorotation. Lat B treatment resulted in a promotion of root curvature after a 90 degrees reorientation in three plant species tested. More significantly, the sensitivity of maize (Zea mays) roots to gravity was enhanced after actin disruption, as determined from a comparison of presentation time of Lat B-treated versus untreated roots. A short 10-min gravistimulus followed by extended rotation on a 1-rpm clinostat resulted in extensive gravitropic responses, manifested as curvature that often exceeded 90 degrees. Application of Lat B to the cap or elongation zone of maize roots resulted in the disruption of the actin cytoskeleton, which was confined to the area of localized Lat B application. Only roots with Lat B applied to the cap displayed the strong curvature responses after extended clinorotation. Our study demonstrates that disrupting the actin cytoskeleton in the cap leads to the persistence of a signal established by a previous gravistimulus. Therefore, actin could function in root gravitropism by providing a mechanism to regulate the proliferation of a gravitropic signal originating from the cap to allow the root to attain its correct orientation or set point angle.

  10. Parthenolide: from plant shoots to cancer roots.

    PubMed

    Ghantous, Akram; Sinjab, Ansam; Herceg, Zdenko; Darwiche, Nadine

    2013-09-01

    Parthenolide (PTL), a sesquiterpene lactone (SL) originally purified from the shoots of feverfew (Tanacetum parthenium), has shown potent anticancer and anti-inflammatory activities. It is currently being tested in cancer clinical trials. Structure-activity relationship (SAR) studies of parthenolide revealed key chemical properties required for biological activities and epigenetic mechanisms, and led to the derivatization of an orally bioavailable analog, dimethylamino-parthenolide (DMAPT). Parthenolide is the first small molecule found to be selective against cancer stem cells (CSC), which it achieves by targeting specific signaling pathways and killing cancer from its roots. In this review, we highlight the exciting journey of parthenolide, from plant shoots to cancer roots. Copyright © 2013 Elsevier Ltd. All rights reserved.

  11. Advancements in Root Growth Measurement Technologies and Observation Capabilities for Container-Grown Plants

    PubMed Central

    Judd, Lesley A.; Jackson, Brian E.; Fonteno, William C.

    2015-01-01

    The study, characterization, observation, and quantification of plant root growth and root systems (Rhizometrics) has been and remains an important area of research in all disciplines of plant science. In the horticultural industry, a large portion of the crops grown annually are grown in pot culture. Root growth is a critical component in overall plant performance during production in containers, and therefore it is important to understand the factors that influence and/or possible enhance it. Quantifying root growth has varied over the last several decades with each method of quantification changing in its reliability of measurement and variation among the results. Methods such as root drawings, pin boards, rhizotrons, and minirhizotrons initiated the aptitude to measure roots with field crops, and have been expanded to container-grown plants. However, many of the published research methods are monotonous and time-consuming. More recently, computer programs have increased in use as technology advances and measuring characteristics of root growth becomes easier. These programs are instrumental in analyzing various root growth characteristics, from root diameter and length of individual roots to branching angle and topological depth of the root architecture. This review delves into the expanding technologies involved with expertly measuring root growth of plants in containers, and the advantages and disadvantages that remain. PMID:27135334

  12. Advancements in Root Growth Measurement Technologies and Observation Capabilities for Container-Grown Plants.

    PubMed

    Judd, Lesley A; Jackson, Brian E; Fonteno, William C

    2015-07-03

    The study, characterization, observation, and quantification of plant root growth and root systems (Rhizometrics) has been and remains an important area of research in all disciplines of plant science. In the horticultural industry, a large portion of the crops grown annually are grown in pot culture. Root growth is a critical component in overall plant performance during production in containers, and therefore it is important to understand the factors that influence and/or possible enhance it. Quantifying root growth has varied over the last several decades with each method of quantification changing in its reliability of measurement and variation among the results. Methods such as root drawings, pin boards, rhizotrons, and minirhizotrons initiated the aptitude to measure roots with field crops, and have been expanded to container-grown plants. However, many of the published research methods are monotonous and time-consuming. More recently, computer programs have increased in use as technology advances and measuring characteristics of root growth becomes easier. These programs are instrumental in analyzing various root growth characteristics, from root diameter and length of individual roots to branching angle and topological depth of the root architecture. This review delves into the expanding technologies involved with expertly measuring root growth of plants in containers, and the advantages and disadvantages that remain.

  13. [Induction of polyploid in hairy roots of Nicotiana tabacum and its plant regeneration].

    PubMed

    Hou, Lili; Shi, Heping; Yu, Wu; Tsang, Po Keung Eric; Chow, Cheuk Fai Stephen

    2014-04-01

    By genetic transformation with Agrobacterum rhizogenes and artificial chromosome doubling techniques, we studied the induction of hairy roots and their polyploidization, and subsequent plant regeneration and nicotine determination to enhance the content of nicotine in Nicotiana tabacum. The results show that hairy roots could be induced from the basal surface of leaf explants of N. tabacum 8 days after inoculation with Agrobacterium rhizogenes ATCC15834. The percentage of the rooting leaf explants was 100% 15 days after inoculation. The hairy roots could grow rapidly and autonomously on solid or liquid phytohormones-free MS medium. The transformation was confirmed by PCR amplification of rol gene of Ri plasmid and paper electrophoresis of opines from N. tabacum hairy roots. The highest rate of polyploidy induction, more than 64.71%, was obtained after treatment of hairy roots with 0.1% colchicine for 36 h. The optimum medium for plant regeneration from polyploid hairy roots was MS+2.0 mg/L 6-BA +0.2 mg/L NAA. Compared with the control diploid plants, the hairy roots-regenerated plants had weak apical dominance, more axillary buds and more narrow leaves; whereas the polyploid hairy root-regenerated plants had thicker stems, shorter internodes and the colour, width and thickness of leaves were significantly higher than that of the control. Observation of the number of chromosomes in their root tip cells reveals that the obtained polyploid regenerated plants were tetraploidy, with 96 (4n = 96) chromosomes. Pot-grown experiments showed compared to the control, the flowering was delayed by 21 days in diploid hairy roots-regenerated plants and polyploid hairy root-regenerated plants. GC-MS detection shows that the content of nicotine in polyploid plants was about 6.90 and 4.57 times the control and the diploid hairy roots-regenerated plants, respectively.

  14. Root carbon flow from an invasive plant to belowground foodwebs

    Treesearch

    Mark A. Bradford; Michael S. Strickland; Jayna L. DeVore; John C. Maerz

    2012-01-01

    Aims Soil foodwebs are based on plant production. This production enters belowground foodwebs via numerous pathways, with root pathways likely dominating supply. Indeed, root exudation may fuel 30–50 % of belowground activity with photosynthate fixed only hours earlier. Yet we have limited knowledge of root fluxes of recent-photosynthate from invasive plants to...

  15. Roles of abiotic losses, microbes, plant roots, and root exudates on phytoremediation of PAHs in a barren soil.

    PubMed

    Sun, Tian-Ran; Cang, Long; Wang, Quan-Ying; Zhou, Dong-Mei; Cheng, Jie-Min; Xu, Hui

    2010-04-15

    Phytoremediation is an emerging technology for the remediation of polycyclic aromatic hydrocarbons (PAHs). In this study, pot experiments were conducted to evaluate the efficacy of phytoremediation of phenanthrene and pyrene in a typical low organic matter soil (3.75 g kg(-1)), and the contribution proportions of abiotic losses, microbes, plant roots, and root exudates were ascertained during the PAHs dissipation. The results indicated that contribution of abiotic losses from this soil was high both for phenanthrene (83.4%) and pyrene (57.2%). The contributions of root-exudates-enhanced biodegradation of phenanthrene (15.5%) and pyrene (21.3%) were higher than those of indigenous microbial degradation. The role of root exudates on dissipation of phenanthrene and pyrene was evident in this experiment. By the way, with the increasing of ring numbers in PAHs structures, the root-exudates-enhanced degradation became more and more important. BIOLOG-ECO plate analysis indicated that microbial community structure of the soil receiving root exudates had changed. The removal efficiency and substrate utilization rate in the treatment with plant roots were lower than the treatment only with root exudates, which suggested that possible competition between roots and microbes for nutrients had occurred in a low organic matter soil. 2009. Published by Elsevier B.V.

  16. Rooting depths of plants relative to biological and environmental factors

    SciTech Connect

    Foxx, T S; Tierney, G D; Williams, J M

    1984-11-01

    In 1981 to 1982 an extensive bibliographic study was completed to document rooting depths of native plants in the United States. The data base presently contains 1034 citations with approximately 12,000 data elements. In this paper the data were analyzed for rooting depths as related to life form, soil type, geographical region, root type, family, root depth to shoot height ratios, and root depth to root lateral ratios. Average rooting depth and rooting frequencies were determined and related to present low-level waste site maintenance.

  17. 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.

  18. Root Formation in Ethylene-Insensitive Plants1

    PubMed Central

    Clark, David G.; Gubrium, Erika K.; Barrett, James E.; Nell, Terril A.; Klee, Harry J.

    1999-01-01

    Experiments with ethylene-insensitive tomato (Lycopersicon esculentum) and petunia (Petunia × hybrida) plants were conducted to determine if normal or adventitious root formation is affected by ethylene insensitivity. Ethylene-insensitive Never ripe (NR) tomato plants produced more belowground root mass but fewer aboveground adventitious roots than wild-type Pearson plants. Applied auxin (indole-3-butyric acid) increased adventitious root formation on vegetative stem cuttings of wild-type plants but had little or no effect on rooting of NR plants. Reduced adventitious root formation was also observed in ethylene-insensitive transgenic petunia plants. Applied 1-aminocyclopropane-1-carboxylic acid increased adventitious root formation on vegetative stem cuttings from NR and wild-type plants, but NR cuttings produced fewer adventitious roots than wild-type cuttings. These data suggest that the promotive effect of auxin on adventitious rooting is influenced by ethylene responsiveness. Seedling root growth of tomato in response to mechanical impedance was also influenced by ethylene sensitivity. Ninety-six percent of wild-type seedlings germinated and grown on sand for 7 d grew normal roots into the medium, whereas 47% of NR seedlings displayed elongated taproots, shortened hypocotyls, and did not penetrate the medium. These data indicate that ethylene has a critical role in various responses of roots to environmental stimuli. PMID:10482660

  19. [Induction of polyploid hairy roots and its plant regeneration in Pogostemon cablin].

    PubMed

    Shi, Heping; Yu, Wu; Zhang, Guopeng; Tsang, Pokeung Eric; Chow, Cheuk Fai Stephen

    2014-08-01

    Abstract: In order to enhance the content of secondary metabolites patchouli alcohol in Pogostemon cablin, we induced polyploid hairy roots and their plant regeneration, and determined the content of patchouli alcohol through artificial chromosome doubling with colchicine. The highest rate of polyploidy induction was more than 40% when hairy roots were treated with 0.05% colchicine for 36 h. The obtained polyploid hairy roots formed adventitious shoots when cultured in an MS medium with 6-BA 0.2 mg/L and NAA 0.1 mg/L for 60 d. Compared with the control diploid plants, the polyploid hairy root-regenerated plants of P. cablin had more developed root systems, thicker stems, shorter internodes and longer, wider and thicker leaves. Observation of the chromosome number in their root tip cells reveals that the obtained polyploid regenerated plants were tetraploidy, with 128 (4n = 128) chromosomes. The leaves contained around twice as many stomatal guard cells and chloroplasts as the controls, but the stomatal density declined with increasing ploidy. The stomatal density in diploid plants was around 1.67 times of that in polyploid plants. GC-MS analysis shows that the content of patchouli alcholol in the hairy root-derived polyploid plants was about 4.25 mg/g dry weight, which was 2.3 times of that in diploid plants. The present study demonstrates that polyploidization of hairy roots can stimulate the content of patchouli alcholol in medicinal plant of P. cablin.

  20. Plant potassium content modifies the effects of arbuscular mycorrhizal symbiosis on root hydraulic properties in maize plants.

    PubMed

    El-Mesbahi, Mohamed Najib; Azcón, Rosario; Ruiz-Lozano, Juan Manuel; Aroca, Ricardo

    2012-10-01

    It is well known that the arbuscular mycorrhizal (AM) symbiosis helps the host plant to overcome several abiotic stresses including drought. One of the mechanisms for this drought tolerance enhancement is the higher water uptake capacity of the mycorrhizal plants. However, the effects of the AM symbiosis on processes regulating root hydraulic properties of the host plant, such as root hydraulic conductivity and plasma membrane aquaporin gene expression, and protein abundance, are not well defined. Since it is known that K(+) status is modified by AM and that it regulates root hydraulic properties, it has been tested how plant K(+) status could modify the effects of the symbiosis on root hydraulic conductivity and plasma membrane aquaporin gene expression and protein abundance, using maize (Zea mays L.) plants and Glomus intraradices as a model. It was observed that the supply of extra K(+) increased root hydraulic conductivity only in AM plants. Also, the different pattern of plasma membrane aquaporin gene expression and protein abundance between AM and non-AM plants changed with the application of extra K(+). Thus, plant K(+) status could be one of the causes of the different observed effects of the AM symbiosis on root hydraulic properties. The present study also highlights the critical importance of AM fungal aquaporins in regulating root hydraulic properties of the host plant.

  1. [Influencing factors on culture of medicinal plants adventitious roots].

    PubMed

    Yin, Shuang-Shuang; Gao, Wen-Yuan; Wang, Juan; Liu, Hui; Zuo, Bei-Mei

    2012-12-01

    With the modernization of traditional Chinese medicine, medicinal plants resources cannot meet the request of Chinese medicine industry. Medicinal plants adventitious roots culture in a large scale is an important way to achieve Chinese medicine industrialization. However, how to establish good adventitious roots culture system is its key, such as plant hormones, explant, sucrose, innoculum and salt strength.

  2. Plant roots and spectroscopic methods - analyzing species, biomass and vitality.

    PubMed

    Rewald, Boris; Meinen, Catharina

    2013-01-01

    In order to understand plant functioning, plant community composition, and terrestrial biogeochemistry, it is decisive to study standing root biomass, (fine) root dynamics, and interactions belowground. While most plant taxa can be identified by visual criteria aboveground, roots show less distinctive features. Furthermore, root systems of neighboring plants are rarely spatially segregated; thus, most soil horizons and samples hold roots of more than one species necessitating root sorting according to taxa. In the last decades, various approaches, ranging from anatomical and morphological analyses to differences in chemical composition and DNA sequencing were applied to discern species' identity and biomass belowground. Among those methods, a variety of spectroscopic methods was used to detect differences in the chemical composition of roots. In this review, spectroscopic methods used to study root systems of herbaceous and woody species in excised samples or in situ will be discussed. In detail, techniques will be reviewed according to their usability to discern root taxa, to determine root vitality, and to quantify root biomass non-destructively or in soil cores holding mixtures of plant roots. In addition, spectroscopic methods which may be able to play an increasing role in future studies on root biomass and related traits are highlighted.

  3. Root traits contributing to plant productivity under drought

    PubMed Central

    Comas, Louise H.; Becker, Steven R.; Cruz, Von Mark V.; Byrne, Patrick F.; Dierig, David A.

    2013-01-01

    Geneticists and breeders are positioned to breed plants with root traits that improve productivity under drought. However, a better understanding of root functional traits and how traits are related to whole plant strategies to increase crop productivity under different drought conditions is needed. Root traits associated with maintaining plant productivity under drought include small fine root diameters, long specific root length, and considerable root length density, especially at depths in soil with available water. In environments with late season water deficits, small xylem diameters in targeted seminal roots save soil water deep in the soil profile for use during crop maturation and result in improved yields. Capacity for deep root growth and large xylem diameters in deep roots may also improve root acquisition of water when ample water at depth is available. Xylem pit anatomy that makes xylem less “leaky” and prone to cavitation warrants further exploration holding promise that such traits may improve plant productivity in water-limited environments without negatively impacting yield under adequate water conditions. Rapid resumption of root growth following soil rewetting may improve plant productivity under episodic drought. Genetic control of many of these traits through breeding appears feasible. Several recent reviews have covered methods for screening root traits but an appreciation for the complexity of root systems (e.g., functional differences between fine and coarse roots) needs to be paired with these methods to successfully identify relevant traits for crop improvement. Screening of root traits at early stages in plant development can proxy traits at mature stages but verification is needed on a case by case basis that traits are linked to increased crop productivity under drought. Examples in lesquerella (Physaria) and rice (Oryza) show approaches to phenotyping of root traits and current understanding of root trait genetics for breeding

  4. Root traits contributing to plant productivity under drought.

    PubMed

    Comas, Louise H; Becker, Steven R; Cruz, Von Mark V; Byrne, Patrick F; Dierig, David A

    2013-11-05

    Geneticists and breeders are positioned to breed plants with root traits that improve productivity under drought. However, a better understanding of root functional traits and how traits are related to whole plant strategies to increase crop productivity under different drought conditions is needed. Root traits associated with maintaining plant productivity under drought include small fine root diameters, long specific root length, and considerable root length density, especially at depths in soil with available water. In environments with late season water deficits, small xylem diameters in targeted seminal roots save soil water deep in the soil profile for use during crop maturation and result in improved yields. Capacity for deep root growth and large xylem diameters in deep roots may also improve root acquisition of water when ample water at depth is available. Xylem pit anatomy that makes xylem less "leaky" and prone to cavitation warrants further exploration holding promise that such traits may improve plant productivity in water-limited environments without negatively impacting yield under adequate water conditions. Rapid resumption of root growth following soil rewetting may improve plant productivity under episodic drought. Genetic control of many of these traits through breeding appears feasible. Several recent reviews have covered methods for screening root traits but an appreciation for the complexity of root systems (e.g., functional differences between fine and coarse roots) needs to be paired with these methods to successfully identify relevant traits for crop improvement. Screening of root traits at early stages in plant development can proxy traits at mature stages but verification is needed on a case by case basis that traits are linked to increased crop productivity under drought. Examples in lesquerella (Physaria) and rice (Oryza) show approaches to phenotyping of root traits and current understanding of root trait genetics for breeding.

  5. Alkamides isolated from plants promote growth and alter root development in Arabidopsis.

    PubMed

    Ramírez-Chávez, Enrique; López-Bucio, José; Herrera-Estrella, Luis; Molina-Torres, Jorge

    2004-03-01

    To date, several classes of hormones have been described that influence plant development, including auxins, cytokinins, ethylene, and, more recently, brassinosteroids. However, it is known that many fungal and bacterial species produce substances that alter plant growth that, if naturally present in plants, might represent novel classes of plant growth regulators. Alkamides are metabolites widely distributed in plants with a broad range of biological activities. In this work, we investigated the effects of affinin, an alkamide naturally occurring in plants, and its derivates, N-isobutyl-2E-decenamide and N-isobutyl-decanamide, on plant growth and early root development in Arabidopsis. We found that treatments with affinin in the range of 10(-6) to 10(-4) m alter shoot and root biomass production. This effect correlated with alteration on primary root growth, lateral root formation, and root hair elongation. Low concentrations of affinin (7 x 10(-6)-2.8 x 10(-5) m) enhanced primary root growth and root hair elongation, whereas higher concentrations inhibited primary root growth that related with a reduction in cell proliferating activity and cell elongation. N-isobutyl-2E-decenamide and N-isobutyl-decanamide were found to stimulate root hair elongation at concentrations between 10(-8) to 10(-7) m. Although the effects of alkamides were similar to those produced by auxins on root growth and cell parameters, the ability of the root system to respond to affinin was found to be independent of auxin signaling. Our results suggest that alkamides may represent a new group of plant growth promoting substances with significant impact on root development and opens the possibility of using these compounds for improved plant production.

  6. Alkamides Isolated from Plants Promote Growth and Alter Root Development in Arabidopsis1

    PubMed Central

    Ramírez-Chávez, Enrique; López-Bucio, José; Herrera-Estrella, Luis; Molina-Torres, Jorge

    2004-01-01

    To date, several classes of hormones have been described that influence plant development, including auxins, cytokinins, ethylene, and, more recently, brassinosteroids. However, it is known that many fungal and bacterial species produce substances that alter plant growth that, if naturally present in plants, might represent novel classes of plant growth regulators. Alkamides are metabolites widely distributed in plants with a broad range of biological activities. In this work, we investigated the effects of affinin, an alkamide naturally occurring in plants, and its derivates, N-isobutyl-2E-decenamide and N-isobutyl-decanamide, on plant growth and early root development in Arabidopsis. We found that treatments with affinin in the range of 10-6 to 10-4 m alter shoot and root biomass production. This effect correlated with alteration on primary root growth, lateral root formation, and root hair elongation. Low concentrations of affinin (7 × 10-6–2.8 × 10-5 m) enhanced primary root growth and root hair elongation, whereas higher concentrations inhibited primary root growth that related with a reduction in cell proliferating activity and cell elongation. N-isobutyl-2E-decenamide and N-isobutyl-decanamide were found to stimulate root hair elongation at concentrations between 10-8 to 10-7 m. Although the effects of alkamides were similar to those produced by auxins on root growth and cell parameters, the ability of the root system to respond to affinin was found to be independent of auxin signaling. Our results suggest that alkamides may represent a new group of plant growth promoting substances with significant impact on root development and opens the possibility of using these compounds for improved plant production. PMID:14988477

  7. 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

  8. Understanding plant root system influences on soil strength and stability

    NASA Astrophysics Data System (ADS)

    Bengough, A. Glyn; Brown, Jennifer L.; Loades, Kenneth W.; Knappett, Jonathan A.; Meijer, Gertjan; Nicoll, Bruce

    2016-04-01

    Keywords: root growth, soil reinforcement, tensile strength Plant roots modify and reinforce the soil matrix, stabilising it against erosion and shallow landslides. Roots mechanically bind the soil particles together and modify the soil hydrology via water uptake, creation of biopores, and modification of the soil water-release characteristic. Key to understanding the mechanical reinforcement of soil by roots is the relation between root strength and root diameter measured for roots in any given soil horizon. Thin roots have frequently been measured to have a greater tensile strength than thick roots, but their strength is also often much more variable. We consider the factors influencing this strength-diameter relationship, considering relations between root tensile strength and root dry density, root water content, root age, and root turnover in several woody and non-woody species. The role of possible experimental artefacts and measurement techniques will be considered. Tensile strength increased generally with root age and decreased with thermal time after excision as a result of root decomposition. Single factors alone do not appear to explain the strength-diameter relationship, and both strength/stiffness and dry density may vary between different layers of tissue within a single root. Results will be discussed to consider how we can achieve a more comprehensive understanding of the variation in root biomechanical properties, and its consequences for soil reinforcement. Acknowledgements: The James Hutton Institute receives funding from the Scottish Government. AGB and JAK acknowledge part funding from EPSRC (EP/M020355/1).

  9. Light as stress factor to plant roots - case of root halotropism.

    PubMed

    Yokawa, Ken; Fasano, Rossella; Kagenishi, Tomoko; Baluška, František

    2014-01-01

    Despite growing underground, largely in darkness, roots emerge to be very sensitive to light. Recently, several important papers have been published which reveal that plant roots not only express all known light receptors but also that their growth, physiology and adaptive stress responses are light-sensitive. In Arabidopsis, illumination of roots speeds-up root growth via reactive oxygen species-mediated and F-actin dependent process. On the other hand, keeping Arabidopsis roots in darkness alters F-actin distribution, polar localization of PIN proteins as well as polar transport of auxin. Several signaling components activated by phytohormones are overlapping with light-related signaling cascade. We demonstrated that the sensitivity of roots to salinity is altered in the light-grown Arabidopsis roots. Particularly, light-exposed roots are less effective in their salt-avoidance behavior known as root halotropism. Here we discuss these new aspects of light-mediated root behavior from cellular, physiological and evolutionary perspectives.

  10. Transgenic plants and hairy roots: exploiting the potential of plant species to remediate contaminants.

    PubMed

    Ibañez, Sabrina; Talano, Melina; Ontañon, Ornella; Suman, Jachym; Medina, María I; Macek, Tomas; Agostini, Elizabeth

    2016-09-25

    Phytoremediation has emerged as an attractive methodology to deal with environmental pollution, which is a serious worldwide problem. Although important advances have been made in this research field, there are still some drawbacks to become a widely used practice, such as the limited plant's metabolic rate and their difficulty to break down several organic compounds or to tolerate/accumulate heavy metals. However, biotechnology has opened new gateways in phytoremediation research by offering the opportunity for direct gene transfer to enhance plant capabilities for environmental cleanup. In this context, hairy roots (HRs) have emerged as an interesting model system to explore the potential of plants to remove inorganic and organic pollutants. Besides, their use in rhizoremediation studies has also been explored. In this minireview we will discuss the most recent advances using genetic engineering for enhancing phytoremediation capabilities of plants and HRs. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Root lengths of plants on Los Alamos National Laboratory lands

    SciTech Connect

    Tierney, G.D.; Foxx, T.S.

    1987-01-01

    Maximum root lengths of 22 plant species occurring on Los Alamos National Laboratory lands were measured. An average of two longest roots from each species were dug up and their lengths, typical shapes, and qualitative morphologics were noted along with the overstory dimensions of the plant individual with which the roots were associated. Maximum root lengths were compared with overstory (height times width) dimensions. Among the life forms studied, the shrubs tend to show the longest roots in relation to overstory size. Forbs show the shortest roots in relation to overstory size. Measurements of tree roots suggest only that immature trees on the Pajarito Plateau may have root-length to overstory-size ratios near one. 30 refs., 14 figs., 2 tabs.

  12. Root bacterial endophytes alter plant phenotype, but not physiology

    SciTech Connect

    Henning, Jeremiah A.; Weston, David J.; Pelletier, Dale A.; Timm, Collin M.; Jawdy, Sara S.; Classen, Aimée T.

    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, net photosynthesis, net photosynthesis at saturating light–Asat, and saturating CO2–Amax). 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.

  13. Root bacterial endophytes alter plant phenotype, but not physiology

    PubMed Central

    Weston, David J.; Pelletier, Dale A.; Jawdy, Sara S.; Classen, Aimée T.

    2016-01-01

    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. 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, net photosynthesis, net photosynthesis at saturating light–Asat, and saturating CO2–Amax). 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. PMID:27833797

  14. Root bacterial endophytes alter plant phenotype, but not physiology

    SciTech Connect

    Classen, Aimee T.; Henning, Jeremiah; Jawdy, Sara; Pelletier, Dale A.; Weston, David; Timm, Collin M.

    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. 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, net photosynthesis, net photosynthesis at saturating light–Asat, and saturating CO2–Amax). 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.

  15. 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–Asat, and saturating CO2–Amax). 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

  16. Root foraging for Patchy Phosphorus of Plant Species with Contrasting Foraging Strategy - Role of Roots and Mycorrhiza

    NASA Astrophysics Data System (ADS)

    Felderer, B.; Robinson, B. H.; Jansa, J.; Vontobel, P.; Frossard, E.; Schulin, R.

    2009-04-01

    Plant nutrients are distributed heterogeneously in soil. Thus the nutrient distribution together with nutrient availability, temporal and spatial development of roots determine nutrient uptake by the plants. Plants have developed several strategies to cope with the patchy nutrient distribution. Preferential root development within nutrient-enriched patches is a prominent response to heterogeneous nutrient distribution. This capacity to precisely allocate roots is called morphological plasticity and is highly variable between plant species. Another strategy is the increased nutrient uptake per unit of root surface in the nutrient-rich patches as compared to root zones outside such patches, so-called physiological plasticity . Additionally, enhanced nutrient uptake from nutrient-rich patches might be supported by increased production of mycorrhizal extraradical hyphae. We refer to this phenomenon as plastic response of the mycorrhiza-plant association. Relative importance for nutrient acquisition of these responses to heterogeneous nutrient distribution might vary between plant species. However, quantitative data are very rare. We will investigate nutrient acquisition and root development over time in sandy substrate with heterogeneous phosphorus (P) distribution of two model plant species with different nutrient foraging strategies (Lotus corniculatus, Trifolium arvense). These plant species are characterized by high and low morphological plasticity, respectively (according to results of preliminary experiments). We follow three main goals in a single mesocosm experiment, where P is to be homogeneously or patchily distributed in a sandy substrate: 1. - Imaging of root architecture of Lotus corniculatus and Trifolium arvense on a time line. 2. - Assessment of the physiological plasticity of Lotus corniculatus and Trifolium arvense 3. - Determination of the plasticity of mycorrhiza-plant association of Lotus corniculatus and Trifolium arvense associated with either of

  17. Desirable plant root traits for protecting unstable slopes against landslides

    NASA Astrophysics Data System (ADS)

    Stokes, A.; Atger, C.; Bengough, G.; Fourcaud, T.; Sidle, R. C.

    2009-04-01

    A trait is defined as a distinct, quantitative property of organisms, usually measured at the individual level and used comparatively across species. Plant quantitative traits are extremely important for understanding the local ecology of any site. Plant height, architecture, root depth, wood density, leaf size and leaf nitrogen concentration control ecosystem processes and define habitat for other taxa. An engineer conjecturing as to how plant traits may directly influence physical processes occurring on sloping land just needs to consider how e.g. canopy architecture and litter properties influence the partitioning of rainfall among interception loss, infiltration and runoff. Plant traits not only influence abiotic processes occurring at a site, but also the habitat for animals and invertebrates. Depending on the goal of the landslide engineer, the immediate and long-term effects of plant traits in an environment must be considered if a site is to remain viable and ecologically successful. When vegetation is considered in models of slope stability, usually the only root parameters taken into consideration are tensile strength and root area ratio. Root system spatial structure is not considered, although the length, orientation and diameter of roots are recognized as being of importance. Thick roots act like soil nails on slopes, reinforcing soil in the same way that concrete is reinforced with steel rods. The spatial position of these thick roots also has an indirect effect on soil fixation in that the location of thin and fine roots will depend on the arrangement of thick roots. Thin and fine roots act in tension during failure on slopes and if they cross the slip surface, are largely responsible for reinforcing soil on slopes. Therefore, the most important trait to consider initially is rooting depth. To stabilize a slope against a shallow landslide, roots must cross the shear surface. The number and thickness of roots in this zone will therefore largely

  18. Root traits contributing to plant productivity under drought

    USDA-ARS?s Scientific Manuscript database

    Geneticists and breeders are poised to breed plants with root traits that improve productivity under drought. However, they need a better understanding of root functional traits and how these traits are related to whole plant strategies to increase crop productivity under different drought conditio...

  19. Conserved Gene Expression Programs in Developing Roots from Diverse Plants

    PubMed Central

    Huang, Ling; Schiefelbein, John

    2015-01-01

    The molecular basis for the origin and diversification of morphological adaptations is a central issue in evolutionary developmental biology. Here, we defined temporal transcript accumulation in developing roots from seven vascular plants, permitting a genome-wide comparative analysis of the molecular programs used by a single organ across diverse species. The resulting gene expression maps uncover significant similarity in the genes employed in roots and their developmental expression profiles. The detailed analysis of a subset of 133 genes known to be associated with root development in Arabidopsis thaliana indicates that most of these are used in all plant species. Strikingly, this was also true for root development in a lycophyte (Selaginella moellendorffii), which forms morphologically different roots and is thought to have evolved roots independently. Thus, despite vast differences in size and anatomy of roots from diverse plants, the basic molecular mechanisms employed during root formation appear to be conserved. This suggests that roots evolved in the two major vascular plant lineages either by parallel recruitment of largely the same developmental program or by elaboration of an existing root program in the common ancestor of vascular plants. PMID:26265761

  20. Conserved Gene Expression Programs in Developing Roots from Diverse Plants.

    PubMed

    Huang, Ling; Schiefelbein, John

    2015-08-01

    The molecular basis for the origin and diversification of morphological adaptations is a central issue in evolutionary developmental biology. Here, we defined temporal transcript accumulation in developing roots from seven vascular plants, permitting a genome-wide comparative analysis of the molecular programs used by a single organ across diverse species. The resulting gene expression maps uncover significant similarity in the genes employed in roots and their developmental expression profiles. The detailed analysis of a subset of 133 genes known to be associated with root development in Arabidopsis thaliana indicates that most of these are used in all plant species. Strikingly, this was also true for root development in a lycophyte (Selaginella moellendorffii), which forms morphologically different roots and is thought to have evolved roots independently. Thus, despite vast differences in size and anatomy of roots from diverse plants, the basic molecular mechanisms employed during root formation appear to be conserved. This suggests that roots evolved in the two major vascular plant lineages either by parallel recruitment of largely the same developmental program or by elaboration of an existing root program in the common ancestor of vascular plants.

  1. Scaling root processes based on plant functional traits (Invited)

    NASA Astrophysics Data System (ADS)

    Eissenstat, D. M.; McCormack, M. L.; Gaines, K.; Adams, T.

    2013-12-01

    There are great challenges to scaling root processes as variation across species and variation of a particular species over different spatial and temporal scales is poorly understood. We have examined tree species variation using multispecies plantings, often referred to by ecologists as 'common gardens'. Choosing species with wide variation in growth rate, root morphology (diameter, branching intensity) and root chemistry (root N and Ca concentration), we found that variation in root lifespan was well correlated with plant functional traits across 12 species. There was also evidence that localized liquid N addition could increase root lifespan and localized water addition diminished root lifespan over untreated controls, with effects strongest in the species of finest root diameter. In an adjacent forest, we have also seen tree species variation in apparent depth of rooting using water isotopes. In particular species of wood anatomy that was ring porous (e.g. oaks) typically had the deepest rooting depth, whereas those that had either diffuse-porous sapwood (maples) or tracheid sapwood (pines) were shallower rooted. These differences in rooting depth were related to sap flux of trees during and immediately after periods of drought. The extent that the patterns observed in central Pennsylvania are modulated by environment or indicative of other plant species will be discussed.

  2. Diversification of Root Hair Development Genes in Vascular Plants.

    PubMed

    Huang, Ling; Shi, Xinhui; Wang, Wenjia; Ryu, Kook Hui; Schiefelbein, John

    2017-07-01

    The molecular genetic program for root hair development has been studied intensively in Arabidopsis (Arabidopsis thaliana). To understand the extent to which this program might operate in other plants, we conducted a large-scale comparative analysis of root hair development genes from diverse vascular plants, including eudicots, monocots, and a lycophyte. Combining phylogenetics and transcriptomics, we discovered conservation of a core set of root hair genes across all vascular plants, which may derive from an ancient program for unidirectional cell growth coopted for root hair development during vascular plant evolution. Interestingly, we also discovered preferential diversification in the structure and expression of root hair development genes, relative to other root hair- and root-expressed genes, among these species. These differences enabled the definition of sets of genes and gene functions that were acquired or lost in specific lineages during vascular plant evolution. In particular, we found substantial divergence in the structure and expression of genes used for root hair patterning, suggesting that the Arabidopsis transcriptional regulatory mechanism is not shared by other species. To our knowledge, this study provides the first comprehensive view of gene expression in a single plant cell type across multiple species. © 2017 American Society of Plant Biologists. All Rights Reserved.

  3. Plant diversity effects on root decomposition in grasslands

    NASA Astrophysics Data System (ADS)

    Chen, Hongmei; Mommer, Liesje; van Ruijven, Jasper; de Kroon, Hans; Gessler, Arthur; Scherer-Lorenzen, Michael; Wirth, Christian; Weigelt, Alexandra

    2016-04-01

    Loss of plant diversity impairs ecosystem functioning. Compared to other well-studied processes, we know little about whether and how plant diversity affects root decomposition, which is limiting our knowledge on biodiversity-carbon cycling relationships in the soil. Plant diversity potentially affects root decomposition via two non-exclusive mechanisms: by providing roots of different substrate quality and/or by altering the soil decomposition environment. To disentangle these two mechanisms, three decomposition experiments using a litter-bag approach were conducted on experimental grassland plots differing in plant species richness, functional group richness and functional group composition (e.g. presence/absence of grasses, legumes, small herbs and tall herbs, the Jena Experiment). We studied: 1) root substrate quality effects by decomposing roots collected from the different experimental plant communities in one common plot; 2) soil decomposition environment effects by decomposing standard roots in all experimental plots; and 3) the overall plant diversity effects by decomposing community roots in their 'home' plots. Litter bags were installed in April 2014 and retrieved after 1, 2 and 4 months to determine the mass loss. We found that mass loss decreased with increasing plant species richness, but not with functional group richness in the three experiments. However, functional group presence significantly affected mass loss with primarily negative effects of the presence of grasses and positive effects of the presence of legumes and small herbs. Our results thus provide clear evidence that species richness has a strong negative effect on root decomposition via effects on both root substrate quality and soil decomposition environment. This negative plant diversity-root decomposition relationship may partly account for the positive effect of plant diversity on soil C stocks by reducing C loss in addition to increasing primary root productivity. However, to fully

  4. Plant Phenotypic and Transcriptional Changes Induced by Volatiles from the Fungal Root Pathogen Rhizoctonia solani

    PubMed Central

    Cordovez, Viviane; Mommer, Liesje; Moisan, Kay; Lucas-Barbosa, Dani; Pierik, Ronald; Mumm, Roland; Carrion, Victor J.; Raaijmakers, Jos M.

    2017-01-01

    Beneficial soil microorganisms can affect plant growth and resistance by the production of volatile organic compounds (VOCs). Yet, little is known on how VOCs from soil-borne plant pathogens affect plant growth and resistance. Here we show that VOCs released from mycelium and sclerotia of the fungal root pathogen Rhizoctonia solani enhance growth and accelerate development of Arabidopsis thaliana. Seedlings briefly exposed to the fungal VOCs showed similar phenotypes, suggesting that enhanced biomass and accelerated development are primed already at early developmental stages. Fungal VOCs did not affect plant resistance to infection by the VOC-producing pathogen itself but reduced aboveground resistance to the herbivore Mamestra brassicae. Transcriptomics of A. thaliana revealed that genes involved in auxin signaling were up-regulated, whereas ethylene and jasmonic acid signaling pathways were down-regulated by fungal VOCs. Mutants disrupted in these pathways showed similar VOC-mediated growth responses as the wild-type A. thaliana, suggesting that other yet unknown pathways play a more prominent role. We postulate that R. solani uses VOCs to predispose plants for infection from a distance by altering root architecture and enhancing root biomass. Alternatively, plants may use enhanced root growth upon fungal VOC perception to sacrifice part of the root biomass and accelerate development and reproduction to survive infection. PMID:28785271

  5. Plant development in space: Observations on root formation and growth

    NASA Technical Reports Server (NTRS)

    Levine, H. G.; Kann, R. P.; Krikorian, Abraham D.

    1990-01-01

    Root growth in space is discussed and observations on root production from plants flown as part of the Chromex project that were defined as to their origin, stage of development and physiological status, are presented. Roots were generated from fully differentiated, aseptically maintained individuals of Haplopappus gracilis (Compositae) under spaceflight conditions. Results are compared for tissue culture generated plantlets and comparably sized seedling clone individuals, both of which had their roots trimmed on Earth before they were loaded into NASA's plant growth unit and subjected to a 5 day shuttle flight (STS-29). Asepsis was maintained throughout the experiment. Overall root production was 40 to 50 percent greater under spaceflight conditions than during ground control tests. However, root formation slowed down towards the end of the flight. This decrease in new roots did not occur in the ground controls that sought to simulate flight except for microgravity.

  6. Plant development in space: Observations on root formation and growth

    NASA Technical Reports Server (NTRS)

    Levine, H. G.; Kann, R. P.; Krikorian, Abraham D.

    1990-01-01

    Root growth in space is discussed and observations on root production from plants flown as part of the Chromex project that were defined as to their origin, stage of development and physiological status, are presented. Roots were generated from fully differentiated, aseptically maintained individuals of Haplopappus gracilis (Compositae) under spaceflight conditions. Results are compared for tissue culture generated plantlets and comparably sized seedling clone individuals, both of which had their roots trimmed on Earth before they were loaded into NASA's plant growth unit and subjected to a 5 day shuttle flight (STS-29). Asepsis was maintained throughout the experiment. Overall root production was 40 to 50 percent greater under spaceflight conditions than during ground control tests. However, root formation slowed down towards the end of the flight. This decrease in new roots did not occur in the ground controls that sought to simulate flight except for microgravity.

  7. Side-Branching Statistics of Plant Root Networks

    NASA Astrophysics Data System (ADS)

    Pollen, N.; Malamud, B.

    2001-12-01

    Many studies exist that characterise plant root architecture by calculating the fractal dimension of the root network, but few studies quantify the branching characteristics of the root network. This paper examines the Tokunaga side-branching statistics for the root systems of four plants--Sugar Beet (Beta vulgaris), Lucern (Medicago sativa), Common Wheat (Triticum aestivum) and White Clover (Trifolium michelianum)--and compares the resulting statistics to those calculated by similar means (by other authors) for the Kentucky and Powder River drainage basins and several Diffusion Limited Aggregation (DLA) models. The plant root networks studied all contained similar numbers of different order roots, but the side-branching statistics differed, offering one explanation for the differing visual appearance of the branching root networks. The White Clover plant had similar Tokunaga branching statistics to the drainage networks and DLA models. This may be due to the dichotomous root structure of the White Clover plant, which produces a network that is much more similar in appearance to the two drainage networks and DLA models than the other three plants, which had herringbone root. All of the root networks, drainage basins, and DLA models had branching networks that could be quantified well to very well by Tokunaga side-branching statistics. For many years, engineers have avoided implementation of stabilisation schemes involving vegetation, due to the inherent problems involved in the quantification of their dynamic and complex root structures. The use of Tokunaga statistics as a simplifying measure of root branching characteristics, may aid in this aspect, as well as others, such as the modelling of nutrient or water uptake.

  8. Does suberin accumulation in plant roots contribute to waterlogging tolerance?

    PubMed Central

    Watanabe, Kohtaro; Nishiuchi, Shunsaku; Kulichikhin, Konstantin; Nakazono, Mikio

    2013-01-01

    Plants that are adapted to waterlogged conditions develop aerenchyma in roots for ventilation. Some wetland plant species also form an apoplastic barrier at the outer cell layers of roots that reduces radial oxygen loss (ROL) from the aerenchyma and prevents toxic compounds from entering the root. The composition of the apoplastic barrier is not well understood. One potential component is suberin, which accumulates at the hypodermal/exodermal cell layers of the roots under waterlogged soil conditions or in response to other environmental stimuli. However, differences in suberin content and composition between plant species make it difficult to evaluate whether suberin has a role in preventing ROL. In this article, we summarize recent advances in understanding apoplastic barrier formation in roots and, between various plant species, compare the chemical compositions of the apoplastic barriers in relation to their permeability to oxygen. Moreover, the relationship between suberin accumulation and the barrier to ROL is discussed. PMID:23785371

  9. Transformation of the Herbicide Sulcotrione into a Root Growth Enhancer Compound by Sequential Photolysis and Hydrolysis.

    PubMed

    Goujon, Eric; Maruel, Sandra; Richard, Claire; Goupil, Pascale; Ledoigt, Gérard

    2016-01-27

    Xanthene-1,9-dione-3,4-dihydro-6-methylsulfonyl (1), the main product of sulcotrione phototransformation on plant leaves, was slowly hydrolyzed into 2-hydroxy-4-methylsulfonylbenzoic acid (2) and 1,3-cyclohexanedione (3) in aqueous solution. Interestingly, the rate of hydrolysis was significantly enhanced in the presence of roots of monocotyledonous plants, while the same treatment showed adverse effects on broadleaf weeds. Root growth enhancement varied according to the plant species and concentrations of compound 2, as shown with Zea mays roots. Compound 2 is a derivative of salicylic acid that is known to be a plant signaling messenger. Compound 2 was, therefore, able to mimic some known effects of this phytohormone. This work showed that a pesticide like sulcotrione was transformed into a compound exhibiting a positive impact on plant growth. This study exemplified a rarely reported situation where chemical and biological chain reactions transformed a xenobiotic into a compound exhibiting potential beneficial effects.

  10. Root foraging influences plant growth responses to earthworm foraging.

    PubMed

    Cameron, Erin K; Cahill, James F; Bayne, Erin M

    2014-01-01

    Interactions among the foraging behaviours of co-occurring animal species can impact population and community dynamics; the consequences of interactions between plant and animal foraging behaviours have received less attention. In North American forests, invasions by European earthworms have led to substantial changes in plant community composition. Changes in leaf litter have been identified as a critical indirect mechanism driving earthworm impacts on plants. However, there has been limited examination of the direct effects of earthworm burrowing on plant growth. Here we show a novel second pathway exists, whereby earthworms (Lumbricus terrestris L.) impact plant root foraging. In a mini-rhizotron experiment, roots occurred more frequently in burrows and soil cracks than in the soil matrix. The roots of Achillea millefolium L. preferentially occupied earthworm burrows, where nutrient availability was presumably higher than in cracks due to earthworm excreta. In contrast, the roots of Campanula rotundifolia L. were less likely to occur in burrows. This shift in root behaviour was associated with a 30% decline in the overall biomass of C. rotundifolia when earthworms were present. Our results indicate earthworm impacts on plant foraging can occur indirectly via physical and chemical changes to the soil and directly via root consumption or abrasion and thus may be one factor influencing plant growth and community change following earthworm invasion. More generally, this work demonstrates the potential for interactions to occur between the foraging behaviours of plants and soil animals and emphasizes the importance of integrating behavioural understanding in foraging studies involving plants.

  11. Root Foraging Influences Plant Growth Responses to Earthworm Foraging

    PubMed Central

    Cameron, Erin K.; Cahill, James F.; Bayne, Erin M.

    2014-01-01

    Interactions among the foraging behaviours of co-occurring animal species can impact population and community dynamics; the consequences of interactions between plant and animal foraging behaviours have received less attention. In North American forests, invasions by European earthworms have led to substantial changes in plant community composition. Changes in leaf litter have been identified as a critical indirect mechanism driving earthworm impacts on plants. However, there has been limited examination of the direct effects of earthworm burrowing on plant growth. Here we show a novel second pathway exists, whereby earthworms (Lumbricus terrestris L.) impact plant root foraging. In a mini-rhizotron experiment, roots occurred more frequently in burrows and soil cracks than in the soil matrix. The roots of Achillea millefolium L. preferentially occupied earthworm burrows, where nutrient availability was presumably higher than in cracks due to earthworm excreta. In contrast, the roots of Campanula rotundifolia L. were less likely to occur in burrows. This shift in root behaviour was associated with a 30% decline in the overall biomass of C. rotundifolia when earthworms were present. Our results indicate earthworm impacts on plant foraging can occur indirectly via physical and chemical changes to the soil and directly via root consumption or abrasion and thus may be one factor influencing plant growth and community change following earthworm invasion. More generally, this work demonstrates the potential for interactions to occur between the foraging behaviours of plants and soil animals and emphasizes the importance of integrating behavioural understanding in foraging studies involving plants. PMID:25268503

  12. Neuroprotective and Cognitive Enhancement Potentials of Angelica gigas Nakai Root: A Review.

    PubMed

    Sowndhararajan, Kandhasamy; Kim, Songmun

    2017-04-28

    Angelica gigas Nakai is an important medicinal plant with health promoting properties that is used to treat many disorders. In traditional herbal medicine, the root of this plant is used to promote blood flow, to treat anemia, and is used as sedative or tonic agent. The root contains various bioactive metabolites; in particular, decursin and decursinol (pyranocoumarin type components) have been reported to possess various pharmacological properties. Recently, several in vitro and in vivo studies have reported that the crude extracts and isolated components from the root of A. gigas exhibited neuroprotective and cognitive enhancement effects. Neuronal damage or death is the most important factor for many neurodegenerative diseases. In addition, recent studies have clearly demonstrated the possible mechanisms behind the neuroprotective action of extracts/compounds from the root of A. gigas. In the present review, we summarized the neuroprotective and cognitive enhancement effects of extracts and individual compounds from A. gigas root.

  13. Neuroprotective and Cognitive Enhancement Potentials of Angelica gigas Nakai Root: A Review

    PubMed Central

    Sowndhararajan, Kandhasamy; Kim, Songmun

    2017-01-01

    Angelica gigas Nakai is an important medicinal plant with health promoting properties that is used to treat many disorders. In traditional herbal medicine, the root of this plant is used to promote blood flow, to treat anemia, and is used as sedative or tonic agent. The root contains various bioactive metabolites; in particular, decursin and decursinol (pyranocoumarin type components) have been reported to possess various pharmacological properties. Recently, several in vitro and in vivo studies have reported that the crude extracts and isolated components from the root of A. gigas exhibited neuroprotective and cognitive enhancement effects. Neuronal damage or death is the most important factor for many neurodegenerative diseases. In addition, recent studies have clearly demonstrated the possible mechanisms behind the neuroprotective action of extracts/compounds from the root of A. gigas. In the present review, we summarized the neuroprotective and cognitive enhancement effects of extracts and individual compounds from A. gigas root. PMID:28452965

  14. A comparative study on the potential of oxygen release by roots of selected wetland plants

    NASA Astrophysics Data System (ADS)

    Yao, Fang; Shen, Gen-xiang; Li, Xue-lian; Li, Huai-zheng; Hu, Hong; Ni, Wu-zhong

    The capacity of root oxygen release by selected wetland plants pre-grown under both nutrient solution and artificial wastewater conditions were determined. The results indicated that the significant differences of root oxygen release by the tested wetland plants existed, and the biochemical process was the main source of root oxygen release as oxygen released by Vetiveria zizanioides L. Nash roots through biochemical process was contributed to 77% and 74% of total root oxygen release under nutrient solution conditions and artificial wastewater conditions, respectively, and that was 72% and 71% of total root oxygen release for Cyperus alternifolius L. It was found that the formation of root plaque with iron oxide was a function of root oxygen release as iron oxide concentration in root plaque was positively correlated to the potential of oxygen released by wetland plant roots with the regression coefficients as 0.874 *( p < 0.05) under nutrient solution conditions and 0.944 **( p < 0.01) under artificial wastewater conditions, which could be regarded as an important mechanism of wetland plants being tolerant to anoxia during wastewater treatment. It was suggested that the potential of root oxygen release could be used as a parameter for selecting wetland plants that can increase oxygen supply to soil or substrate of constructed wetlands and enhance nutrient transformation and removal, and V. zizanioides L. Nash with the highest potential of root oxygen release and higher tolerance to wastewater could be recommended to establish vegetated wetlands for treating nutrient-rich wastewater such as domestic wastewater.

  15. The unseen iceberg: plant roots in arctic tundra

    DOE PAGES

    Iversen, Colleen M.; Sloan, Victoria L.; Sullivan, Patrick F.; ...

    2014-09-10

    Arctic tundra is characterized by short-statured plant communities underlain by carbon (C)-rich soils and permafrost. Ecosystem C and nutrient cycles in tundra are driven by complex interactions between plants and their environment. However, root dynamics are one of the least understood aspects of plant growth in the Arctic. We synthesized available literature on tundra roots and discussed their representation in terrestrial biosphere models. Belowground biomass in tundra ecosystems can be an order of magnitude larger than aboveground biomass. Data on root production and turnover in tundra is sparse, limiting our understanding of the controls over root dynamics in these systems.more » Roots are shallowly distributed in the thin layer of soil that thaws each year, and are often found in the organic horizon at the soil surface. Species-specific differences in root distribution, mycorrhizal colonization, and resource partitioning may affect plant species competition under changing climatic conditions. Model representation of belowground processes has increased in complexity over recent years, but data are desperately needed to fill the gaps in model treatment of tundra roots. Future research should focus on estimates of root production and lifespan, and interactions between roots and the surrounding soil across the diversity of tundra ecosystems in the Arctic.« less

  16. The unseen iceberg: plant roots in arctic tundra

    SciTech Connect

    Iversen, Colleen M.; Sloan, Victoria L.; Sullivan, Patrick F.; Euskirchen, Eugenie S.; McGuire, A. David; Norby, Richard J.; Walker, Anthony P.; Warren, Jeffrey M.; Wullschleger, Stan D.

    2014-09-10

    Arctic tundra is characterized by short-statured plant communities underlain by carbon (C)-rich soils and permafrost. Ecosystem C and nutrient cycles in tundra are driven by complex interactions between plants and their environment. However, root dynamics are one of the least understood aspects of plant growth in the Arctic. We synthesized available literature on tundra roots and discussed their representation in terrestrial biosphere models. Belowground biomass in tundra ecosystems can be an order of magnitude larger than aboveground biomass. Data on root production and turnover in tundra is sparse, limiting our understanding of the controls over root dynamics in these systems. Roots are shallowly distributed in the thin layer of soil that thaws each year, and are often found in the organic horizon at the soil surface. Species-specific differences in root distribution, mycorrhizal colonization, and resource partitioning may affect plant species competition under changing climatic conditions. Model representation of belowground processes has increased in complexity over recent years, but data are desperately needed to fill the gaps in model treatment of tundra roots. Future research should focus on estimates of root production and lifespan, and interactions between roots and the surrounding soil across the diversity of tundra ecosystems in the Arctic.

  17. A bell pepper cultivar tolerant to chilling enhanced nitrogen allocation and stress-related metabolite accumulation in the roots in response to low root-zone temperature.

    PubMed

    Aidoo, Moses Kwame; Sherman, Tal; Lazarovitch, Naftali; Fait, Aaron; Rachmilevitch, Shimon

    2017-10-01

    Two bell pepper (Capsicum annuum) cultivars, differing in their response to chilling, were exposed to three levels of root-zone temperatures. Gas exchange, shoot and root phenology, and the pattern of change of the central metabolites and secondary metabolites caffeate and benzoate in the leaves and roots were profiled. Low root-zone temperature significantly inhibited gaseous exchange, with a greater effect on the sensitive commercial pepper hybrid (Canon) than on the new hybrid bred to enhance abiotic stress tolerance (S103). The latter was less affected by the treatment with respect to plant height, shoot dry mass, root maximum length, root projected area, number of root tips and root dry mass. More carbon was allocated to the leaves of S103 than nitrogen at 17°C, while in the roots at 17°C, more nitrogen was allocated and the ratio between C/N decreased. Metabolite profiling showed greater increase in the root than in the leaves. Leaf response between the two cultivars differed significantly. The roots accumulated stress-related metabolites including γ-aminobutyric acid (GABA), proline, galactinol and raffinose and at chilling (7°C) resulted in an increase of sugars in both cultivars. Our results suggest that the enhanced tolerance of S103 to root cold stress, reflected in the relative maintenance of shoot and root growth, is likely linked to a more effective regulation of photosynthesis facilitated by the induction of stress-related metabolism. © 2017 Scandinavian Plant Physiology Society.

  18. Root-Specific Reduction of Cytokinin Causes Enhanced Root Growth, Drought Tolerance, and Leaf Mineral Enrichment in Arabidopsis and Tobacco[C][W][OA

    PubMed Central

    Werner, Tomáš; Nehnevajova, Erika; Köllmer, Ireen; Novák, Ondřej; Strnad, Miroslav; Krämer, Ute; Schmülling, Thomas

    2010-01-01

    Optimizing root system architecture can overcome yield limitations in crop plants caused by water or nutrient shortages. Classic breeding approaches are difficult because the trait is governed by many genes and is difficult to score. We generated transgenic Arabidopsis thaliana and tobacco (Nicotiana tabacum) plants with enhanced root-specific degradation of the hormone cytokinin, a negative regulator of root growth. These transgenic plants form a larger root system, whereas growth and development of the shoot are similar. Elongation of the primary root, root branching, and root biomass formation were increased by up to 60% in transgenic lines, increasing the root-to-shoot ratio. We thus demonstrated that a single dominant gene could regulate a complex trait, root growth. Moreover, we showed that cytokinin regulates root growth in a largely organ-autonomous fashion that is consistent with its dual role as a hormone with both paracrine and long-distance activities. Transgenic plants had a higher survival rate after severe drought treatment. The accumulation of several elements, including S, P, Mn, Mg, Zn, as well as Cd from a contaminated soil, was significantly increased in shoots. Under conditions of sulfur or magnesium deficiency, leaf chlorophyll content was less affected in transgenic plants, demonstrating the physiological relevance of shoot element accumulation. Our approach might contribute to improve drought tolerance, nutrient efficiency, and nutrient content of crop plants. PMID:21148816

  19. Use of plant roots for phytoremediation and molecular farming.

    PubMed

    Gleba, D; Borisjuk, N V; Borisjuk, L G; Kneer, R; Poulev, A; Skarzhinskaya, M; Dushenkov, S; Logendra, S; Gleba, Y Y; Raskin, I

    1999-05-25

    Alternative agriculture, which expands the uses of plants well beyond food and fiber, is beginning to change plant biology. Two plant-based biotechnologies were recently developed that take advantage of the ability of plant roots to absorb or secrete various substances. They are (i) phytoextraction, the use of plants to remove pollutants from the environment and (ii) rhizosecretion, a subset of molecular farming, designed to produce and secrete valuable natural products and recombinant proteins from roots. Here we discuss recent advances in these technologies and assess their potential in soil remediation, drug discovery, and molecular farming.

  20. Use of plant roots for phytoremediation and molecular farming

    PubMed Central

    Gleba, Doloressa; Borisjuk, Nikolai V.; Borisjuk, Ludmyla G.; Kneer, Ralf; Poulev, Alexander; Skarzhinskaya, Marina; Dushenkov, Slavik; Logendra, Sithes; Gleba, Yuri Y.; Raskin, Ilya

    1999-01-01

    Alternative agriculture, which expands the uses of plants well beyond food and fiber, is beginning to change plant biology. Two plant-based biotechnologies were recently developed that take advantage of the ability of plant roots to absorb or secrete various substances. They are (i) phytoextraction, the use of plants to remove pollutants from the environment and (ii) rhizosecretion, a subset of molecular farming, designed to produce and secrete valuable natural products and recombinant proteins from roots. Here we discuss recent advances in these technologies and assess their potential in soil remediation, drug discovery, and molecular farming. PMID:10339526

  1. Tomato PYR/PYL/RCAR abscisic acid receptors show high expression in root, differential sensitivity to the abscisic acid agonist quinabactin, and the capability to enhance plant drought resistance.

    PubMed

    González-Guzmán, Miguel; Rodríguez, Lesia; Lorenzo-Orts, Laura; Pons, Clara; Sarrión-Perdigones, Alejandro; Fernández, Maria A; Peirats-Llobet, Marta; Forment, Javier; Moreno-Alvero, Maria; Cutler, Sean R; Albert, Armando; Granell, Antonio; Rodríguez, Pedro L

    2014-08-01

    Abscisic acid (ABA) plays a crucial role in the plant's response to both biotic and abiotic stress. Sustainable production of food faces several key challenges, particularly the generation of new varieties with improved water use efficiency and drought tolerance. Different studies have shown the potential applications of Arabidopsis PYR/PYL/RCAR ABA receptors to enhance plant drought resistance. Consequently the functional characterization of orthologous genes in crops holds promise for agriculture. The full set of tomato (Solanum lycopersicum) PYR/PYL/RCAR ABA receptors have been identified here. From the 15 putative tomato ABA receptors, 14 of them could be grouped in three subfamilies that correlated well with corresponding Arabidopsis subfamilies. High levels of expression of PYR/PYL/RCAR genes was found in tomato root, and some genes showed predominant expression in leaf and fruit tissues. Functional characterization of tomato receptors was performed through interaction assays with Arabidopsis and tomato clade A protein phosphatase type 2Cs (PP2Cs) as well as phosphatase inhibition studies. Tomato receptors were able to inhibit the activity of clade A PP2Cs differentially in an ABA-dependent manner, and at least three receptors were sensitive to the ABA agonist quinabactin, which inhibited tomato seed germination. Indeed, the chemical activation of ABA signalling induced by quinabactin was able to activate stress-responsive genes. Both dimeric and monomeric tomato receptors were functional in Arabidopsis plant cells, but only overexpression of monomeric-type receptors conferred enhanced drought resistance. In summary, gene expression analyses, and chemical and transgenic approaches revealed distinct properties of tomato PYR/PYL/RCAR ABA receptors that might have biotechnological implications. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  2. Circumnutation as an autonomous root movement in plants.

    PubMed

    Migliaccio, Fernando; Tassone, Paola; Fortunati, Alessio

    2013-01-01

    Although publications on circumnutation of the aerial parts of flowering plants are numerous and primarily from the time between Darwin (1880) and the 1950s, reports on circumnutation of roots are scarce. With the introduction of modern molecular biology techniques, many topics in the plant sciences have been revitalized; among these is root circumnutation. The most important research in this area has been done on Arabidopsis thaliana, which has roots that behave differently from those of many other plants; roots grown on inclined agar dishes produce a pattern of half waves slanted to one side. When grown instead on horizontally set dishes, the roots grow in loops or in tight right-handed coils that are characterized by a tight torsion to the left-hand. The roots of the few plants that differ from Arabidopsis and have been similarly tested do not present such patterns, because even if they circumnutate generally in a helical pattern, they subsequently straighten. Research on plants in space or on a clinostat has allowed the testing of these roots in a habitat lacking gravity or simulating the lack. Recently, molecular geneticists have started to connect various root behaviors to specific groups of genes. For example, anomalies in auxin responses caused by some genes can be overcome by complementation with wild-type genes. Such important studies contribute to understanding the mechanisms of growth and elongation, processes that are only superficially understood.

  3. Auxin: a master regulator in plant root development.

    PubMed

    Saini, Shivani; Sharma, Isha; Kaur, Navdeep; Pati, Pratap Kumar

    2013-06-01

    The demand for increased crop productivity and the predicted challenges related to plant survival under adverse environmental conditions have renewed the interest in research in root biology. Various physiological and genetic studies have provided ample evidence in support of the role of plant growth regulators in root development. The biosynthesis and transport of auxin and its signaling play a crucial role in controlling root growth and development. The univocal role of auxin in root development has established it as a master regulator. Other plant hormones, such as cytokinins, brassinosteroids, ethylene, abscisic acid, gibberellins, jasmonic acid, polyamines and strigolactones interact either synergistically or antagonistically with auxin to trigger cascades of events leading to root morphogenesis and development. In recent years, the availability of biological resources, development of modern tools and experimental approaches have led to the advancement of knowledge in root development. Research in the areas of hormone signal perception, understanding network of events involved in hormone action and the transport of plant hormones has added a new dimension to root biology. The present review highlights some of the important conceptual developments in the interplay of auxin and other plant hormones and associated downstream events affecting root development.

  4. 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.

  5. Role of calcium in gravity perception of plant roots

    NASA Astrophysics Data System (ADS)

    Evans, Michael L.

    Calcium ions may play a key role in linking graviperception by the root cap to the asymmetric growth which occurs in the elongation zone of gravistimulated roots. Application of calcium-chelating agents to the root cap inhibits gravitropic curvature without affecting growth. Asymmetric application of calcium to one side of the root cap induces curvature toward the calcium source, and gravistimulation induces polar movement of applied 45Ca2+ across the root cap toward the lower side. The action of calcium may be linked to auxin movement in roots since 1) auxin transport inhibitors interfere both with gravitropic curvature and gravi-induced polar calcium movement and 2) asymmetric application of calcium enhances auxin movement across the elongation zone of gravistimulated roots. Indirect evidence indicates that the calcium-modulated regulator protein, calmodulin, may be involved in either the transport or action of calcium in the gravitropic response mechanism of roots.

  6. Effects of glycoalkaloids from Solanum plants on cucumber root growth.

    PubMed

    Sun, Fang; Li, Shengyu; He, Dajun; Cao, Gang; Ni, Xiuzhen; Tai, Guihua; Zhou, Yifa; Wang, Deli

    2010-09-01

    The phytotoxic effect of four glycoalkaloids and two 6-O-sulfated glycoalkaloid derivatives were evaluated by testing their inhibition of cucumber root growth. The bioassays were performed using both compounds singly and in equimolar mixtures, respectively. Cucumber root growth was reduced by chaconine (C), solanine (S), solamargine (SM) and solasonine (SS) with IC(50) values of 260 (C), 380 (S), 530 (SM), and 610 microM (SS). The inhibitory effect was concentration-dependent. 6-O-sulfated chaconine and 6-O-sulfated solamargine had no inhibitory effects, which indicated that the carbohydrate moieties play an important role in inhibiting cucumber root growth. The equimolar mixtures of paired glycoalkaloids, both chaconine/solanine and solamargine/solasonine, produced synergistic effects on inhibition of cucumber root growth. By contrast, mixtures of unpaired glycoalkaloids from different plants had no obviously synergistic effects. The growth inhibited plant roots lacked hairs, which implied that inhibition was perhaps at the level of root hair growth.

  7. Root cause analysis at the Savannah River Plant

    SciTech Connect

    Paradies, M; Busch, D

    1988-01-01

    Events (or near misses) provide important information about ways to improve plant performance. Any particular event may have several /open quotes/root causes/close quotes/ that need correcting to prevent recurrence of the event and, thereby, improve the safety of the plant. Also, by reviewing a large number of events, one can identify cause trends or /open quotes/generic concerns./close quotes/ A method has been developed at Savannah River Plant (SRP) to systematically evaluate events, identify their root causes, record the root causes, and analyze the root cause trends. By providing a systematic method to identify correctable root causes, the system helps the event investigator ask the right questions during the investigation. It also provides an independent safety analysis group and management with statistics indicating existing and developing trouble spots. 3 refs., 4 figs.

  8. Silicon modifies root anatomy, and uptake and subcellular distribution of cadmium in young maize plants

    PubMed Central

    Vaculík, Marek; Landberg, Tommy; Greger, Maria; Luxová, Miroslava; Stoláriková, Miroslava; Lux, Alexander

    2012-01-01

    Background and Aims Silicon (Si) has been shown to ameliorate the negative influence of cadmium (Cd) on plant growth and development. However, the mechanism of this phenomenon is not fully understood. Here we describe the effect of Si on growth, and uptake and subcellular distribution of Cd in maize plants in relation to the development of root tissues. Methods Young maize plants (Zea mays) were cultivated for 10 d hydroponically with 5 or 50 µm Cd and/or 5 mm Si. Growth parameters and the concentrations of Cd and Si were determined in root and shoot by atomic absorption spectrometry or inductively coupled plasma mass spectroscopy. The development of apoplasmic barriers (Casparian bands and suberin lamellae) and vascular tissues in roots were analysed, and the influence of Si on apoplasmic and symplasmic distribution of 109Cd applied at 34 nm was investigated between root and shoot. Key Results Si stimulated the growth of young maize plants exposed to Cd and influenced the development of Casparian bands and suberin lamellae as well as vascular tissues in root. Si did not affect the distribution of apoplasmic and symplasmic Cd in maize roots, but considerably decreased symplasmic and increased apoplasmic concentration of Cd in maize shoots. Conclusions Differences in Cd uptake of roots and shoots are probably related to the development of apoplasmic barriers and maturation of vascular tissues in roots. Alleviation of Cd toxicity by Si might be attributed to enhanced binding of Cd to the apoplasmic fraction in maize shoots. PMID:22455991

  9. Silicon modifies root anatomy, and uptake and subcellular distribution of cadmium in young maize plants.

    PubMed

    Vaculík, Marek; Landberg, Tommy; Greger, Maria; Luxová, Miroslava; Stoláriková, Miroslava; Lux, Alexander

    2012-07-01

    Silicon (Si) has been shown to ameliorate the negative influence of cadmium (Cd) on plant growth and development. However, the mechanism of this phenomenon is not fully understood. Here we describe the effect of Si on growth, and uptake and subcellular distribution of Cd in maize plants in relation to the development of root tissues. Young maize plants (Zea mays) were cultivated for 10 d hydroponically with 5 or 50 µm Cd and/or 5 mm Si. Growth parameters and the concentrations of Cd and Si were determined in root and shoot by atomic absorption spectrometry or inductively coupled plasma mass spectroscopy. The development of apoplasmic barriers (Casparian bands and suberin lamellae) and vascular tissues in roots were analysed, and the influence of Si on apoplasmic and symplasmic distribution of (109)Cd applied at 34 nm was investigated between root and shoot. Si stimulated the growth of young maize plants exposed to Cd and influenced the development of Casparian bands and suberin lamellae as well as vascular tissues in root. Si did not affect the distribution of apoplasmic and symplasmic Cd in maize roots, but considerably decreased symplasmic and increased apoplasmic concentration of Cd in maize shoots. Differences in Cd uptake of roots and shoots are probably related to the development of apoplasmic barriers and maturation of vascular tissues in roots. Alleviation of Cd toxicity by Si might be attributed to enhanced binding of Cd to the apoplasmic fraction in maize shoots.

  10. Abscisic acid accumulation modulates auxin transport in the root tip to enhance proton secretion for maintaining root growth under moderate water stress.

    PubMed

    Xu, Weifeng; Jia, Liguo; Shi, Weiming; Liang, Jiansheng; Zhou, Feng; Li, Qianfeng; Zhang, Jianhua

    2013-01-01

    Maintenance of root growth is essential for plant adaptation to soil drying. Here, we tested the hypothesis that auxin transport is involved in mediating ABA's modulation by activating proton secretion in the root tip to maintain root growth under moderate water stress. Rice and Arabidopsis plants were raised under a hydroponic system and subjected to moderate water stress (-0.47 MPa) with polyethylene glycol (PEG). ABA accumulation, auxin transport and plasma membrane H(+)-ATPase activity at the root tip were monitored in addition to the primary root elongation and root hair density. We found that moderate water stress increases ABA accumulation and auxin transport in the root apex. Additionally, ABA modulation is involved in the regulation of auxin transport in the root tip. The transported auxin activates the plasma membrane H(+)-ATPase to release more protons along the root tip in its adaption to moderate water stress. The proton secretion in the root tip is essential in maintaining or promoting primary root elongation and root hair development under moderate water stress. These results suggest that ABA accumulation modulates auxin transport in the root tip, which enhances proton secretion for maintaining root growth under moderate water stress.

  11. Arbuscular mycorrhiza: the mother of plant root endosymbioses.

    PubMed

    Parniske, Martin

    2008-10-01

    Arbuscular mycorrhiza (AM), a symbiosis between plants and members of an ancient phylum of fungi, the Glomeromycota, improves the supply of water and nutrients, such as phosphate and nitrogen, to the host plant. In return, up to 20% of plant-fixed carbon is transferred to the fungus. Nutrient transport occurs through symbiotic structures inside plant root cells known as arbuscules. AM development is accompanied by an exchange of signalling molecules between the symbionts. A novel class of plant hormones known as strigolactones are exuded by the plant roots. On the one hand, strigolactones stimulate fungal metabolism and branching. On the other hand, they also trigger seed germination of parasitic plants. Fungi release signalling molecules, in the form of 'Myc factors' that trigger symbiotic root responses. Plant genes required for AM development have been characterized. During evolution, the genetic programme for AM has been recruited for other plant root symbioses: functional adaptation of a plant receptor kinase that is essential for AM symbiosis paved the way for nitrogen-fixing bacteria to form intracellular symbioses with plant cells.

  12. The unseen iceberg: Plant roots in arctic tundra

    USGS Publications Warehouse

    Iverson, Colleen M.; Sloan, Victoria L.; Sullivan, Patrick F.; Euskirchen, E.S.; McGuire, Anthony; Norby, Richard J.; Walker, Anthony P.; Warren, Jeffrey M.; Wullschleger, Stan D.

    2015-01-01

    Plant roots play a critical role in ecosystem function in arctic tundra, but root dynamics in these ecosystems are poorly understood. To address this knowledge gap, we synthesized available literature on tundra roots, including their distribution, dynamics and contribution to ecosystem carbon and nutrient fluxes, and highlighted key aspects of their representation in terrestrial biosphere models. Across all tundra ecosystems, belowground plant biomass exceeded aboveground biomass, with the exception of polar desert tundra. Roots were shallowly distributed in the thin layer of soil that thaws annually, and were often found in surface organic soil horizons. Root traits – including distribution, chemistry, anatomy and resource partitioning – play an important role in controlling plant species competition, and therefore ecosystem carbon and nutrient fluxes, under changing climatic conditions, but have only been quantified for a small fraction of tundra plants. Further, the annual production and mortality of fine roots are key components of ecosystem processes in tundra, but extant data are sparse. Tundra root traits and dynamics should be the focus of future research efforts. Better representation of the dynamics and characteristics of tundra roots will improve the utility of models for the evaluation of the responses of tundra ecosystems to changing environmental conditions.

  13. The unseen iceberg: plant roots in arctic tundra.

    PubMed

    Iversen, Colleen M; Sloan, Victoria L; Sullivan, Patrick F; Euskirchen, Eugenie S; McGuire, A David; Norby, Richard J; Walker, Anthony P; Warren, Jeffrey M; Wullschleger, Stan D

    2015-01-01

    Plant roots play a critical role in ecosystem function in arctic tundra, but root dynamics in these ecosystems are poorly understood. To address this knowledge gap, we synthesized available literature on tundra roots, including their distribution, dynamics and contribution to ecosystem carbon and nutrient fluxes, and highlighted key aspects of their representation in terrestrial biosphere models. Across all tundra ecosystems, belowground plant biomass exceeded aboveground biomass, with the exception of polar desert tundra. Roots were shallowly distributed in the thin layer of soil that thaws annually, and were often found in surface organic soil horizons. Root traits - including distribution, chemistry, anatomy and resource partitioning - play an important role in controlling plant species competition, and therefore ecosystem carbon and nutrient fluxes, under changing climatic conditions, but have only been quantified for a small fraction of tundra plants. Further, the annual production and mortality of fine roots are key components of ecosystem processes in tundra, but extant data are sparse. Tundra root traits and dynamics should be the focus of future research efforts. Better representation of the dynamics and characteristics of tundra roots will improve the utility of models for the evaluation of the responses of tundra ecosystems to changing environmental conditions. No claim to original US Government works New Phytologist © 2014 New Phytologist Trust.

  14. Plant root tortuosity: an indicator of root path formation in soil with different composition and density.

    PubMed

    Popova, Liyana; van Dusschoten, Dagmar; Nagel, Kerstin A; Fiorani, Fabio; Mazzolai, Barbara

    2016-05-03

    Root soil penetration and path optimization are fundamental for root development in soil. We describe the influence of soil strength on root elongation rate and diameter, response to gravity, and root-structure tortuosity, estimated by average curvature of primary maize roots. Soils with different densities (1·5, 1·6, 1·7 g cm(-3)), particle sizes (sandy loam; coarse sand mixed with sandy loam) and layering (monolayer, bilayer) were used. In total, five treatments were performed: Mix_low with mixed sand low density (three pots, 12 plants), Mix_medium - mixed sand medium density (three pots, 12 plants), Mix_high - mixed sand high density (three pots, ten plants), Loam_low sandy loam soil low density (four pots, 16 plants), and Bilayer with top layer of sandy loam and bottom layer mixed sand both of low density (four pots, 16 plants). We used non-invasive three-dimensional magnetic resonance imaging to quantify effects of these treatments. Roots grew more slowly [root growth rate (mm h(-1)); decreased 50 %] with increased diameters [root diameter (mm); increased 15 %] in denser soils (1·7 vs. 1·5 g cm(-3)). Root response to gravity decreased 23 % with increased soil compaction, and tortuosity increased 10 % in mixed sand. Response to gravity increased 39 % and tortuosity decreased 3 % in sandy loam. After crossing a bilayered-soil interface, roots grew more slowly, similar to roots grown in soil with a bulk density of 1·64 g cm(-3), whereas the actual experimental density was 1·48±0·02 g cm(-3) Elongation rate and tortuosity were higher in Mix_low than in Loam_low. The present study increases our existing knowledge of the influence of physical soil properties on root growth and presents new assays for studying root growth dynamics in non-transparent media. We found that root tortuosity is indicative of root path selection, because it could result from both mechanical deflection and active root growth in response to touch stimulation and

  15. Plant root tortuosity: an indicator of root path formation in soil with different composition and density

    PubMed Central

    Popova, Liyana; van Dusschoten, Dagmar; Nagel, Kerstin A.; Fiorani, Fabio; Mazzolai, Barbara

    2016-01-01

    Background and Aims Root soil penetration and path optimization are fundamental for root development in soil. We describe the influence of soil strength on root elongation rate and diameter, response to gravity, and root-structure tortuosity, estimated by average curvature of primary maize roots. Methods Soils with different densities (1·5, 1·6, 1·7 g cm−3), particle sizes (sandy loam; coarse sand mixed with sandy loam) and layering (monolayer, bilayer) were used. In total, five treatments were performed: Mix_low with mixed sand low density (three pots, 12 plants), Mix_medium - mixed sand medium density (three pots, 12 plants), Mix_high - mixed sand high density (three pots, ten plants), Loam_low sandy loam soil low density (four pots, 16 plants), and Bilayer with top layer of sandy loam and bottom layer mixed sand both of low density (four pots, 16 plants). We used non-invasive three-dimensional magnetic resonance imaging to quantify effects of these treatments. Key Results Roots grew more slowly [root growth rate (mm h–1); decreased 50 %] with increased diameters [root diameter (mm); increased 15 %] in denser soils (1·7 vs. 1·5 g cm–3). Root response to gravity decreased 23 % with increased soil compaction, and tortuosity increased 10 % in mixed sand. Response to gravity increased 39 % and tortuosity decreased 3 % in sandy loam. After crossing a bilayered–soil interface, roots grew more slowly, similar to roots grown in soil with a bulk density of 1·64 g cm–3, whereas the actual experimental density was 1·48±0·02 g cm–3. Elongation rate and tortuosity were higher in Mix_low than in Loam_low. Conclusions The present study increases our existing knowledge of the influence of physical soil properties on root growth and presents new assays for studying root growth dynamics in non-transparent media. We found that root tortuosity is indicative of root path selection, because it could result from both mechanical deflection and

  16. Nematode feeding sites: unique organs in plant roots.

    PubMed

    Kyndt, Tina; Vieira, Paulo; Gheysen, Godelieve; de Almeida-Engler, Janice

    2013-11-01

    Although generally unnoticed, nearly all crop plants have one or more species of nematodes that feed on their roots, frequently causing tremendous yield losses. The group of sedentary nematodes, which are among the most damaging plant-parasitic nematodes, cause the formation of special organs called nematode feeding sites (NFS) in the root tissue. In this review we discuss key metabolic and cellular changes correlated with NFS development, and similarities and discrepancies between different types of NFS are highlighted.

  17. Proteins as nitrogen source for plants: a short story about exudation of proteases by plant roots.

    PubMed

    Adamczyk, Bartosz; Smolander, Aino; Kitunen, Veikko; Godlewski, Mirosław

    2010-07-01

    Interest in the problem of plant nitrogen nutrition is increasing. Certain plants can use not only inorganic nitrogen, but also intact amino acids and short peptides. According to our studies, the roots of several agricultural and wild-living plants are able to exude proteases and by using them to create a pool of accessible N. This mini-review offers an overview of the problem of protease exudation by plant roots and its potential role in plant nitrogen nutrition.

  18. Tomato PYR/PYL/RCAR abscisic acid receptors show high expression in root, differential sensitivity to the abscisic acid agonist quinabactin, and the capability to enhance plant drought resistance

    PubMed Central

    González-Guzmán, Miguel; Rodríguez, Lesia; Lorenzo-Orts, Laura; Pons, Clara; Sarrión-Perdigones, Alejandro; Fernández, Maria A.; Peirats-Llobet, Marta; Forment, Javier; Moreno-Alvero, Maria; Cutler, Sean R.; Albert, Armando; Granell, Antonio; Rodríguez, Pedro L.

    2014-01-01

    Abscisic acid (ABA) plays a crucial role in the plant’s response to both biotic and abiotic stress. Sustainable production of food faces several key challenges, particularly the generation of new varieties with improved water use efficiency and drought tolerance. Different studies have shown the potential applications of Arabidopsis PYR/PYL/RCAR ABA receptors to enhance plant drought resistance. Consequently the functional characterization of orthologous genes in crops holds promise for agriculture. The full set of tomato (Solanum lycopersicum) PYR/PYL/RCAR ABA receptors have been identified here. From the 15 putative tomato ABA receptors, 14 of them could be grouped in three subfamilies that correlated well with corresponding Arabidopsis subfamilies. High levels of expression of PYR/PYL/RCAR genes was found in tomato root, and some genes showed predominant expression in leaf and fruit tissues. Functional characterization of tomato receptors was performed through interaction assays with Arabidopsis and tomato clade A protein phosphatase type 2Cs (PP2Cs) as well as phosphatase inhibition studies. Tomato receptors were able to inhibit the activity of clade A PP2Cs differentially in an ABA-dependent manner, and at least three receptors were sensitive to the ABA agonist quinabactin, which inhibited tomato seed germination. Indeed, the chemical activation of ABA signalling induced by quinabactin was able to activate stress-responsive genes. Both dimeric and monomeric tomato receptors were functional in Arabidopsis plant cells, but only overexpression of monomeric-type receptors conferred enhanced drought resistance. In summary, gene expression analyses, and chemical and transgenic approaches revealed distinct properties of tomato PYR/PYL/RCAR ABA receptors that might have biotechnological implications. PMID:24863435

  19. Enhancing Students' Understanding of Square Roots

    ERIC Educational Resources Information Center

    Wiesman, Jeff L.

    2015-01-01

    Students enrolled in a middle school prealgebra or algebra course often struggle to conceptualize and understand the meaning of radical notation when it is introduced. For example, although it is important for students to approximate the decimal value of a number such as [square root of] 30 and estimate the value of a square root in the form of…

  20. Enhancing Students' Understanding of Square Roots

    ERIC Educational Resources Information Center

    Wiesman, Jeff L.

    2015-01-01

    Students enrolled in a middle school prealgebra or algebra course often struggle to conceptualize and understand the meaning of radical notation when it is introduced. For example, although it is important for students to approximate the decimal value of a number such as [square root of] 30 and estimate the value of a square root in the form of…

  1. RootGraph: a graphic optimization tool for automated image analysis of plant roots

    PubMed Central

    Cai, Jinhai; Zeng, Zhanghui; Connor, Jason N.; Huang, Chun Yuan; Melino, Vanessa; Kumar, Pankaj; Miklavcic, Stanley J.

    2015-01-01

    This paper outlines a numerical scheme for accurate, detailed, and high-throughput image analysis of plant roots. In contrast to existing root image analysis tools that focus on root system-average traits, a novel, fully automated and robust approach for the detailed characterization of root traits, based on a graph optimization process is presented. The scheme, firstly, distinguishes primary roots from lateral roots and, secondly, quantifies a broad spectrum of root traits for each identified primary and lateral root. Thirdly, it associates lateral roots and their properties with the specific primary root from which the laterals emerge. The performance of this approach was evaluated through comparisons with other automated and semi-automated software solutions as well as against results based on manual measurements. The comparisons and subsequent application of the algorithm to an array of experimental data demonstrate that this method outperforms existing methods in terms of accuracy, robustness, and the ability to process root images under high-throughput conditions. PMID:26224880

  2. RootGraph: a graphic optimization tool for automated image analysis of plant roots.

    PubMed

    Cai, Jinhai; Zeng, Zhanghui; Connor, Jason N; Huang, Chun Yuan; Melino, Vanessa; Kumar, Pankaj; Miklavcic, Stanley J

    2015-11-01

    This paper outlines a numerical scheme for accurate, detailed, and high-throughput image analysis of plant roots. In contrast to existing root image analysis tools that focus on root system-average traits, a novel, fully automated and robust approach for the detailed characterization of root traits, based on a graph optimization process is presented. The scheme, firstly, distinguishes primary roots from lateral roots and, secondly, quantifies a broad spectrum of root traits for each identified primary and lateral root. Thirdly, it associates lateral roots and their properties with the specific primary root from which the laterals emerge. The performance of this approach was evaluated through comparisons with other automated and semi-automated software solutions as well as against results based on manual measurements. The comparisons and subsequent application of the algorithm to an array of experimental data demonstrate that this method outperforms existing methods in terms of accuracy, robustness, and the ability to process root images under high-throughput conditions. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  3. Using Hairy Roots for Production of Valuable Plant Secondary Metabolites.

    PubMed

    Tian, Li

    2015-01-01

    Plants synthesize a wide variety of natural products, which are traditionally termed secondary metabolites and, more recently, coined specialized metabolites. While these chemical compounds are employed by plants for interactions with their environment, humans have long since explored and exploited plant secondary metabolites for medicinal and practical uses. Due to the tissue-specific and low-abundance accumulation of these metabolites, alternative means of production in systems other than intact plants are sought after. To this end, hairy root culture presents an excellent platform for producing valuable secondary metabolites. This chapter will focus on several major groups of secondary metabolites that are manufactured by hairy roots established from different plant species. Additionally, the methods for preservations of hairy roots will also be reviewed.

  4. GiA Roots: software for the high throughput analysis of plant root system architecture

    PubMed Central

    2012-01-01

    Background Characterizing root system architecture (RSA) is essential to understanding the development and function of vascular plants. Identifying RSA-associated genes also represents an underexplored opportunity for crop improvement. Software tools are needed to accelerate the pace at which quantitative traits of RSA are estimated from images of root networks. Results We have developed GiA Roots (General Image Analysis of Roots), a semi-automated software tool designed specifically for the high-throughput analysis of root system images. GiA Roots includes user-assisted algorithms to distinguish root from background and a fully automated pipeline that extracts dozens of root system phenotypes. Quantitative information on each phenotype, along with intermediate steps for full reproducibility, is returned to the end-user for downstream analysis. GiA Roots has a GUI front end and a command-line interface for interweaving the software into large-scale workflows. GiA Roots can also be extended to estimate novel phenotypes specified by the end-user. Conclusions We demonstrate the use of GiA Roots on a set of 2393 images of rice roots representing 12 genotypes from the species Oryza sativa. We validate trait measurements against prior analyses of this image set that demonstrated that RSA traits are likely heritable and associated with genotypic differences. Moreover, we demonstrate that GiA Roots is extensible and an end-user can add functionality so that GiA Roots can estimate novel RSA traits. In summary, we show that the software can function as an efficient tool as part of a workflow to move from large numbers of root images to downstream analysis. PMID:22834569

  5. GiA Roots: software for the high throughput analysis of plant root system architecture.

    PubMed

    Galkovskyi, Taras; Mileyko, Yuriy; Bucksch, Alexander; Moore, Brad; Symonova, Olga; Price, Charles A; Topp, Christopher N; Iyer-Pascuzzi, Anjali S; Zurek, Paul R; Fang, Suqin; Harer, John; Benfey, Philip N; Weitz, Joshua S

    2012-07-26

    Characterizing root system architecture (RSA) is essential to understanding the development and function of vascular plants. Identifying RSA-associated genes also represents an underexplored opportunity for crop improvement. Software tools are needed to accelerate the pace at which quantitative traits of RSA are estimated from images of root networks. We have developed GiA Roots (General Image Analysis of Roots), a semi-automated software tool designed specifically for the high-throughput analysis of root system images. GiA Roots includes user-assisted algorithms to distinguish root from background and a fully automated pipeline that extracts dozens of root system phenotypes. Quantitative information on each phenotype, along with intermediate steps for full reproducibility, is returned to the end-user for downstream analysis. GiA Roots has a GUI front end and a command-line interface for interweaving the software into large-scale workflows. GiA Roots can also be extended to estimate novel phenotypes specified by the end-user. We demonstrate the use of GiA Roots on a set of 2393 images of rice roots representing 12 genotypes from the species Oryza sativa. We validate trait measurements against prior analyses of this image set that demonstrated that RSA traits are likely heritable and associated with genotypic differences. Moreover, we demonstrate that GiA Roots is extensible and an end-user can add functionality so that GiA Roots can estimate novel RSA traits. In summary, we show that the software can function as an efficient tool as part of a workflow to move from large numbers of root images to downstream analysis.

  6. Bacteria from Wheat and Cucurbit Plant Roots Metabolize PAHs and Aromatic Root Exudates: Implications for Rhizodegradation.

    PubMed

    Ely, Cairn S; Smets, Barth F

    2017-03-20

    The chemical interaction between plants and bacteria in the root zone can lead to soil decontamination. Bacteria which degrade PAHs have been isolated from the rhizospheres of plant species with varied biological traits, however, it is not known what phytochemicals promote contaminant degradation. One monocot and two dicotyledon plants were grown in PAH-contaminated soil from a manufactured gas plant (MGP) site. A phytotoxicity assay confirmed greater soil decontamination in rhizospheres when compared to bulk soil controls. Bacteria were isolated from plant roots (rhizobacteria) and selected for growth on anthracene and chrysene on PAH-amended plates. Rhizosphere isolates metabolized 3- and 4-ring PAHs and PAH catabolic intermediates in liquid incubations. Aromatic root exudate compounds, namely flavonoids and simple phenols, were also substrates for isolated rhizobacteria. In particular, the phenolic compounds - morin, caffeic acid, and protocatechuic acid - appear to be linked to bacterial degradation of 3- and 4- ring PAHs in the rhizosphere.

  7. Trichoderma-plant root colonization: escaping early plant defense responses and activation of the antioxidant machinery for saline stress tolerance.

    PubMed

    Brotman, Yariv; Landau, Udi; Cuadros-Inostroza, Álvaro; Tohge, Takayuki; Takayuki, Tohge; Fernie, Alisdair R; Chet, Ilan; Viterbo, Ada; Willmitzer, Lothar

    2013-03-01

    Trichoderma spp. are versatile opportunistic plant symbionts which can colonize the apoplast of plant roots. Microarrays analysis of Arabidopsis thaliana roots inoculated with Trichoderma asperelloides T203, coupled with qPCR analysis of 137 stress responsive genes and transcription factors, revealed wide gene transcript reprogramming, proceeded by a transient repression of the plant immune responses supposedly to allow root colonization. Enhancement in the expression of WRKY18 and WRKY40, which stimulate JA-signaling via suppression of JAZ repressors and negatively regulate the expression of the defense genes FMO1, PAD3 and CYP71A13, was detected in Arabidopsis roots upon Trichoderma colonization. Reduced root colonization was observed in the wrky18/wrky40 double mutant line, while partial phenotypic complementation was achieved by over-expressing WRKY40 in the wrky18 wrky40 background. On the other hand increased colonization rate was found in roots of the FMO1 knockout mutant. Trichoderma spp. stimulate plant growth and resistance to a wide range of adverse environmental conditions. Arabidopsis and cucumber (Cucumis sativus L.) plants treated with Trichoderma prior to salt stress imposition show significantly improved seed germination. In addition, Trichoderma treatment affects the expression of several genes related to osmo-protection and general oxidative stress in roots of both plants. The MDAR gene coding for monodehydroascorbate reductase is significantly up-regulated and, accordingly, the pool of reduced ascorbic acid was found to be increased in Trichoderma treated plants. 1-Aminocyclopropane-1-carboxylate (ACC)-deaminase silenced Trichoderma mutants were less effective in providing tolerance to salt stress, suggesting that Trichoderma, similarly to ACC deaminase producing bacteria, can ameliorate plant growth under conditions of abiotic stress, by lowering ameliorating increases in ethylene levels as well as promoting an elevated antioxidative capacity.

  8. Trichoderma-Plant Root Colonization: Escaping Early Plant Defense Responses and Activation of the Antioxidant Machinery for Saline Stress Tolerance

    PubMed Central

    Brotman, Yariv; Landau, Udi; Cuadros-Inostroza, Álvaro; Takayuki, Tohge; Fernie, Alisdair R.; Chet, Ilan; Viterbo, Ada; Willmitzer, Lothar

    2013-01-01

    Trichoderma spp. are versatile opportunistic plant symbionts which can colonize the apoplast of plant roots. Microarrays analysis of Arabidopsis thaliana roots inoculated with Trichoderma asperelloides T203, coupled with qPCR analysis of 137 stress responsive genes and transcription factors, revealed wide gene transcript reprogramming, proceeded by a transient repression of the plant immune responses supposedly to allow root colonization. Enhancement in the expression of WRKY18 and WRKY40, which stimulate JA-signaling via suppression of JAZ repressors and negatively regulate the expression of the defense genes FMO1, PAD3 and CYP71A13, was detected in Arabidopsis roots upon Trichoderma colonization. Reduced root colonization was observed in the wrky18/wrky40 double mutant line, while partial phenotypic complementation was achieved by over-expressing WRKY40 in the wrky18 wrky40 background. On the other hand increased colonization rate was found in roots of the FMO1 knockout mutant. Trichoderma spp. stimulate plant growth and resistance to a wide range of adverse environmental conditions. Arabidopsis and cucumber (Cucumis sativus L.) plants treated with Trichoderma prior to salt stress imposition show significantly improved seed germination. In addition, Trichoderma treatment affects the expression of several genes related to osmo-protection and general oxidative stress in roots of both plants. The MDAR gene coding for monodehydroascorbate reductase is significantly up-regulated and, accordingly, the pool of reduced ascorbic acid was found to be increased in Trichoderma treated plants. 1-Aminocyclopropane-1-carboxylate (ACC)-deaminase silenced Trichoderma mutants were less effective in providing tolerance to salt stress, suggesting that Trichoderma, similarly to ACC deaminase producing bacteria, can ameliorate plant growth under conditions of abiotic stress, by lowering ameliorating increases in ethylene levels as well as promoting an elevated antioxidative capacity

  9. 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.

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

    PubMed Central

    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.

    2014-01-01

    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. PMID:24927545

  11. Improved nitrogen nutrition enhances root uptake, root-to-shoot translocation and remobilization of zinc ((65) Zn) in wheat.

    PubMed

    Erenoglu, Emin Bulent; Kutman, Umit Baris; Ceylan, Yasemin; Yildiz, Bahar; Cakmak, Ismail

    2011-01-01

    This study focussed on the effect of increasing nitrogen (N) supply on root uptake and root-to-shoot translocation of zinc (Zn) as well as retranslocation of foliar-applied Zn in durum wheat (Triticum durum). Nutrient solution experiments were conducted to examine the root uptake and root-to-shoot translocation of (65) Zn in seedlings precultured with different N supplies. In additional experiments, the effect of varied N nutrition on retranslocation of foliar-applied (65) Zn was tested at both the vegetative and generative stages. When N supply was increased, the (65) Zn uptake by roots was enhanced by up to threefold and the (65) Zn translocation from roots to shoots increased by up to eightfold, while plant growth was affected to a much smaller degree. Retranslocation of (65) Zn from old into young leaves and from flag leaves to grains also showed marked positive responses to increasing N supply. The results demonstrate that the N-nutritional status of wheat affects major steps in the route of Zn from the growth medium to the grain, including its uptake, xylem transport and remobilization via phloem. Thus, N is a critical player in the uptake and accumulation of Zn in plants, which deserves special attention in biofortification of food crops with Zn. © The Authors (2010). Journal compilation © New Phytologist Trust (2010).

  12. Fungal root endophytes of the carnivorous plant Drosera rotundifolia.

    PubMed

    Quilliam, Richard S; Jones, David L

    2010-06-01

    As carnivorous plants acquire substantial amounts of nutrients from the digestion of their prey, mycorrhizal associations are considered to be redundant; however, fungal root endophytes have rarely been examined. As endophytic fungi can have profound impacts on plant communities, we aim to determine the extent of fungal root colonisation of the carnivorous plant Drosera rotundifolia at two points in the growing season (spring and summer). We have used a culture-dependent method to isolate fungal endophytes and diagnostic polymerase chain reaction methods to determine arbuscular mycorrhizal fungi colonisation. All of the roots sampled contained culturable fungal root endophytes; additionally, we have provided molecular evidence that they also host arbuscular mycorrhizal fungi. Colonisation showed seasonal differences: Roots in the spring were colonised by Articulospora tetracladia, two isolates of uncultured ectomycorrhizal fungi, an unidentified species of fungal endophyte and Trichoderma viride, which was present in every plant sampled. In contrast, roots in the summer were colonised by Alatospora acuminata, an uncultured ectomycorrhizal fungus, Penicillium pinophilum and an uncultured fungal clone. Although the functional roles of fungal endophytes of D. rotundifolia are unknown, colonisation may (a) confer abiotic stress tolerance, (b) facilitate the acquisition of scarce nutrients particularly at the beginning of the growing season or (c) play a role in nutrient signalling between root and shoot.

  13. The influence of arbuscular mycorrhizae on root precision nutrient foraging of two pioneer plant species during early reclamation

    NASA Astrophysics Data System (ADS)

    Boldt-Burisch, Katja; Naeth, M. Anne

    2017-04-01

    On many post mining sites in the Lusatian Mining District (East Germany) soil heterogeneity consists of sandy soil with embedded clay-silt fragments. Those clays silt fragments might act as nutrient hotspots. Arbuscular mycorrhizal fungi in an infertile ecosystem could enhance a plant's ability to selectively forage for those nutrients and thus to improve plants nutrient supply. In our study we investigated whether silt-clay fragments within a sandy soil matrix induced preferential root growth of Lotus corniculatus and Calamagrostis epigeios, whether arbuscular mycorrhizae influenced root foraging patterns, and to what extent selective rooting in clay silt fragments influenced plant growth were addressed in this research. Soil types were sterile and non-sterile sandy soil and clay-silt fragments. Treatments were with and without arbuscular mycorrhizae, with and without soil solution, and soil solution and mycorrhizal inoculum combined. Root biomass, root density and intraradical fungal alkaline phosphatase activity and frequency were determined in fragments relative to sandy soil. Furthermore, temporal relationship of number of roots in fragments and plant height was assessed. Lotus corniculatus showed strong selective rooting into fragments especially with those plants treated with commercial cultivated arbuscular mycorrhizae; Calamagrostis epigeios did not. Without arbuscular mycorrhizae, L. corniculatus growth was significantly reduced and selective rooting did not occur. Selective rooting induced significant growth spurts of L. corniculatus. Roots in fragments had higher fungal alkaline phosphatase activity suggesting that mycorrhizal efficiency and related plants phosphorus supply is enhanced in roots in fragments. The application of cultivated arbuscular mycorrhizal fungi significantly and quickly influenced root foraging patterns, especially those of L. corniculatus, suggesting mycorrhizae may also enhance the ability of other plants to selectively forage

  14. Root exudate cocktails: the link between plant diversity and soil microorganisms?

    PubMed

    Steinauer, Katja; Chatzinotas, Antonis; Eisenhauer, Nico

    2016-10-01

    Higher plant diversity is often associated with higher soil microbial biomass and diversity, which is assumed to be partly due to elevated root exudate diversity. However, there is little experimental evidence that diversity of root exudates shapes soil microbial communities. We tested whether higher root exudate diversity enhances soil microbial biomass and diversity in a plant diversity gradient, thereby negating significant plant diversity effects on soil microbial properties. We set up plant monocultures and two- and three-species mixtures in microcosms using functionally dissimilar plants and soil of a grassland biodiversity experiment in Germany. Artificial exudate cocktails were added by combining the most common sugars, organic acids, and amino acids found in root exudates. We applied four different exudate cocktails: two exudate diversity levels (low- and high-diversity) and two nutrient-enriched levels (carbon- and nitrogen-enriched), and a control with water only. Soil microorganisms were more carbon- than nitrogen-limited. Cultivation-independent fingerprinting analysis revealed significantly different soil microbial communities among exudate diversity treatments. Most notably and according to our hypothesis, adding diverse exudate cocktails negated the significant plant diversity effect on soil microbial properties. Our findings provide the first experimental evidence that root exudate diversity is a crucial link between plant diversity and soil microorganisms.

  15. Network modules and hubs in plant-root fungal biomes

    PubMed Central

    Toju, Hirokazu; Yamamoto, Satoshi; Tanabe, Akifumi S.; Hayakawa, Takashi; Ishii, Hiroshi S.

    2016-01-01

    Terrestrial plants host phylogenetically and functionally diverse groups of below-ground microbes, whose community structure controls plant growth/survival in both natural and agricultural ecosystems. Therefore, understanding the processes by which whole root-associated microbiomes are organized is one of the major challenges in ecology and plant science. We here report that diverse root-associated fungi can form highly compartmentalized networks of coexistence within host roots and that the structure of the fungal symbiont communities can be partitioned into semi-discrete types even within a single host plant population. Illumina sequencing of root-associated fungi in a monodominant south beech forest revealed that the network representing symbiont–symbiont co-occurrence patterns was compartmentalized into clear modules, which consisted of diverse functional groups of mycorrhizal and endophytic fungi. Consequently, terminal roots of the plant were colonized by either of the two largest fungal species sets (represented by Oidiodendron or Cenococcum). Thus, species-rich root microbiomes can have alternative community structures, as recently shown in the relationships between human gut microbiome type (i.e. ‘enterotype’) and host individual health. This study also shows an analytical framework for pinpointing network hubs in symbiont–symbiont networks, leading to the working hypothesis that a small number of microbial species organize the overall root–microbiome dynamics. PMID:26962029

  16. In vitro CLE peptide bioactivity assay on plant roots

    USDA-ARS?s Scientific Manuscript database

    Plant CLAVATA3/ESR (CLE)-related proteins play diverse roles in plant growth and development including regulating the development of root meristem. Mature CLE peptides are typically 12-13 amino acids (aa) in length that are derived from the conserved C-termini of their precursor proteins. Genes enco...

  17. Light as stress factor to plant roots – case of root halotropism

    PubMed Central

    Yokawa, Ken; Fasano, Rossella; Kagenishi, Tomoko; Baluška, František

    2014-01-01

    Despite growing underground, largely in darkness, roots emerge to be very sensitive to light. Recently, several important papers have been published which reveal that plant roots not only express all known light receptors but also that their growth, physiology and adaptive stress responses are light-sensitive. In Arabidopsis, illumination of roots speeds-up root growth via reactive oxygen species-mediated and F-actin dependent process. On the other hand, keeping Arabidopsis roots in darkness alters F-actin distribution, polar localization of PIN proteins as well as polar transport of auxin. Several signaling components activated by phytohormones are overlapping with light-related signaling cascade. We demonstrated that the sensitivity of roots to salinity is altered in the light-grown Arabidopsis roots. Particularly, light-exposed roots are less effective in their salt-avoidance behavior known as root halotropism. Here we discuss these new aspects of light-mediated root behavior from cellular, physiological and evolutionary perspectives. PMID:25566292

  18. Antimicrobial properties of roots of medicinal plants.

    PubMed

    Sini, S; Malathy, N S

    2005-10-01

    Antibacterial properties of hexane, chloroform and aqueous extracts of roots of Acorus calamus, Aristolochia indica, Cyperus rotundus, Desmodium gangeticum, Holostemma ada- kodien and Kaempferia galanga, used in the traditional medicine were studied on Bacillus pumilis and Eschericia coli by disc diffusion method.

  19. ANTIMICROBIAL PROPERTIES OF ROOTS OF MEDICINAL PLANTS

    PubMed Central

    Sini, S.; Malathy, N.S.

    2005-01-01

    Antibacterial properties of hexane, chloroform and aqueous extracts of roots of Acorus calamus, Aristolochia indica, Cyperus rotundus, Desmodium gangeticum, Holostemma ada– kodien and Kaempferia galanga, used in the traditional medicine were studied on Bacillus pumilis and Eschericia coli by disc diffusion method. PMID:22557193

  20. Integrating water by plant roots over spatially distributed soil salinity

    NASA Astrophysics Data System (ADS)

    Homaee, Mehdi; Schmidhalter, Urs

    2010-05-01

    In numerical simulation models dealing with water movement and solute transport in vadose zone, the water budget largely depends on uptake patterns by plant roots. In real field conditions, the uptake pattern largely changes in time and space. When dealing with soil and water salinity, most saline soils demonstrate spatially distributed osmotic head over the root zone. In order to quantify such processes, the major difficulty stems from lacking a sink term function that adequately accounts for the extraction term especially under variable soil water osmotic heads. The question of how plants integrate such space variable over its rooting depth remains as interesting issue for investigators. To move one step forward towards countering this concern, a well equipped experiment was conducted under heterogeneously distributed salinity over the root zone with alfalfa. The extraction rates of soil increments were calculated with the one dimensional form of Richards equation. The results indicated that the plant uptake rate under different mean soil salinities preliminary reacts to soil salinity, whereas at given water content and salinity the "evaporative demand" and "root activity" become more important to control the uptake patterns. Further analysis revealed that root activity is inconstant when imposed to variable soil salinity. It can be concluded that under heterogeneously distributed salinity, most water is taken from the less saline increment while the extraction from other root zone increments with higher salinities never stops.

  1. Helical growth trajectories in plant roots interacting with stiff barriers

    NASA Astrophysics Data System (ADS)

    Gerbode, Sharon; Noar, Roslyn; Harrison, Maria

    2009-03-01

    Plant roots successfully navigate heterogeneous soil environments with varying nutrient and water concentrations, as well as a variety of stiff obstacles. While it is thought that the ability of roots to penetrate into a stiff lower soil layer is important for soil erosion, little is known about how a root actually responds to a rigid interface. We have developed a laser sheet imaging technique for recording the 3D growth dynamics of plant roots interacting with stiff barriers. We find that a root encountering an angled interface does not grow in a straight line along the surface, but instead follows a helical trajectory. These experiments build on the pioneering studies of roots grown on a tilted 2D surface, which reported ``root waving,'' a similar curved pattern thought to be caused by the root's sensitivity to both gravity and the rigid surface on which it is grown. Our measurements extend these results to the more physiologically relevant case of 3D growth, where the spiral trajectory can be altered by tuning the relative strengths of the gravity and touch stimuli, providing some intuition for the physical mechanism driving it.

  2. Chemical Mowing: Effect of Plant Growth Retardants on Plant Roots

    DTIC Science & Technology

    1991-08-01

    fructose, sucrose, and fructans were considerably greater in leaf and stem tissue than in roots. Annual bluegrass stems were the major storage organ...for fructans , with only minor fructan storage occurring in roots. The carbohydrate content of mefluidide-treated annual bluegrass decreased

  3. A meta-analysis of plant responses to dark septate root endophytes.

    PubMed

    Newsham, K K

    2011-05-01

    • Dark septate endophytes (DSE) frequently colonize roots in the natural environment, but the effects of these fungi on plants are obscure, with previous studies indicating negative, neutral or positive effects on plant performance. • In order to reach a consensus for how DSE influence plant performance, meta-analyses were performed on data from 18 research articles, in which plants had been inoculated with DSE in sterile substrates. • Negative effects of DSE on plant performance were not recorded. Positive effects were identified on total, shoot and root biomass, and on shoot nitrogen (N) and phosphorus contents, with increases of 26-103% in these parameters for plants inoculated with DSE, relative to uninoculated controls. Inoculation increased total, shoot and root biomass by 52-138% when plants had not been supplied with additional inorganic N, or when all, or the majority, of N was supplied in organic form. Inoculation with the DSE Phialocephala fortinii was found to increase shoot and root biomass, shoot P concentration and shoot N content by 44-116%, relative to uninoculated controls. • The analyses here suggest that DSE enhance plant performance under controlled conditions, particularly when all, or the majority, of N is available in organic form.

  4. [Fine root nitrogen contents and morphological adaptations of alpine plants].

    PubMed

    Salpagarova, F S; van Logtestijn, R S P; Onipchenko, V G; Akhmetzhanova, A A; Agafonov, V A

    2013-01-01

    Nitrogen and carbon contents of fine roots were studied for 92 alpine plant species in the Northwest Caucasus. Nitrogen content ranged from 0.43% (Bromus variegatus) to 3.75% (Corydalis conorhiza) with mean value 1.3%. Carbon content ranged from 40.3% (Corydalis conorhiza) to 51.7% (Empetrum nigrum) with mean value 43.4%. C:N ratio was found to be 34:1 which is higher than the worldwide mean. Eudicot's roots had higher N concentration (1.37 +/- 0.07) than monocot's ones (0.95 +/- 0.09). Among the life forms, carbon content increased in the following order: geophytes < hemicriptophytes < chamaephytes. Specific root length positively correlated with nitrogen root content and negatively--with carbon root content. Species with larger leaves and higher specific root area had more nitrogen and less carbon in roots in comparison with species with small leaves. There were positive correlations between leaf and root nitrogen, as well as carbon, contents. Regrowth rate; seed size, aboveground biomass, and vegetation mobility were not related with root nitrogen content. Our results corroborate the poor and rich soil adaptation syndromes. Species of competitive and ruderal (sensu Grime) strategies are more typical for alpine meadows and snow bed communities. They had higher nitrogen contents in leaves and roots, larger leaves with higher water content and higher rate of seed production. On the other hand, stress-tolerant plants had higher carbon and less nitrogen concentrations in their roots and leaves, smaller leaves and specific leaf area.

  5. Genetic improvement for root growth angle to enhance crop production

    PubMed Central

    Uga, Yusaku; Kitomi, Yuka; Ishikawa, Satoru; Yano, Masahiro

    2015-01-01

    The root system is an essential organ for taking up water and nutrients and anchoring shoots to the ground. On the other hand, the root system has rarely been regarded as breeding target, possibly because it is more laborious and time-consuming to evaluate roots (which require excavation) in a large number of plants than aboveground tissues. The root growth angle (RGA), which determines the direction of root elongation in the soil, affects the area in which roots capture water and nutrients. In this review, we describe the significance of RGA as a potential trait to improve crop production, and the physiological and molecular mechanisms that regulate RGA. We discuss the prospects for breeding to improve RGA based on current knowledge of quantitative trait loci for RGA in rice. PMID:26069440

  6. Root Zone Respiration on Hydroponically Grown Wheat Plant Systems

    NASA Technical Reports Server (NTRS)

    Soler-Crespo, R. A.; Monje, O. A.

    2010-01-01

    Root respiration is a biological phenomenon that controls plant growth and physiological development during a plant's lifespan. This process is dependent on the availability of oxygen in the system where the plant is located. In hydroponic systems, where plants are submerged in a solution containing vital nutrients but no type of soil, the availability of oxygen arises from the dissolved oxygen concentration in the solution. This oxygen concentration is dependent on the , gas-liquid interface formed on the upper surface of the liquid, as given by Henry's Law, depending on pressure and temperature conditions. Respiration rates of the plants rise as biomass and root zone increase with age. The respiration rate of Apogee wheat plants (Triticum aestivum) was measured as a function of light intensity (catalytic for photosynthesis) and CO2 concentration to determine their effect on respiration rates. To determine their effects on respiration rate and plant growth microbial communities were introduced into the system, by Innoculum. Surfactants were introduced, simulating gray-water usage in space, as another factor to determine their effect on chemical oxygen demand of microbials and on respiration rates of the plants. It is expected to see small effects from changes in CO2 concentration or light levels, and to see root respiration decrease in an exponential manner with plant age and microbial activity.

  7. Production and metabolic engineering of bioactive substances in plant hairy root culture.

    PubMed

    Zhou, Mei-Liang; Zhu, Xue-Mei; Shao, Ji-Rong; Tang, Yi-Xiong; Wu, Yan-Min

    2011-05-01

    In the past three decades, hairy roots research for the production of valuable biological active substances has received a lot of attention. The addition of knowledge to enhance the yields of desired substances and the development of novel tools for biomass engineering offer new possibilities for large-scale cultivation of the plant hairy root. Hairy roots can also produce recombinant proteins through the transfer of Agrobacterium T-DNA into the plant genome, and thereby hold immense potential for the pharmaceutical industry. This review highlights some of the significant progress made in the past few years and outlines future prospects for exploiting the potential utility of hairy root cultures as "chemical factories" for producing bioactive substances.

  8. The roles of peptide hormones during plant root development.

    PubMed

    Yamada, Masashi; Sawa, Shinichiro

    2013-02-01

    Peptide hormones are a key mechanism that plants use for cell-cell interactions; these interactions function to coordinate development, growth, and environmental responses among different cells. Peptide signals are produced by one cell and received by receptors in neighboring cells. It has previously been reported that peptide hormones regulate various aspects of plant development. The mechanism of action of peptides in the shoot is well known. However, the function of peptides in the root has been relatively uncharacterized. Recent studies have discovered important roles for peptide hormones in the development of the root meristem, lateral roots, and nodules. In this review, we focus on current findings regarding the function of peptide hormones in root development.

  9. Plant Rooting Depth, Soil Hydrology, and Implications to Terrestrial Environmental Change

    NASA Astrophysics Data System (ADS)

    Fan, Y.; Miguez-Macho, G.

    2016-12-01

    Plant rooting depth is a first-order indicator of the depth of the Earth's crust penetrated, exploited and altered by terrestrial vegetation. Deep root penetration accelerates rock weathering while reducing erosion thus actively shaping the evolution of terrestrial and global environment (through long-term carbon cycle). Deeper roots allow plant access to deeper resources enhancing resilience to environmental stress, thus in part underlying plant biogeography. Unlike their aboveground counterparts, roots are difficult to observe, and basic knowledge, such as their vertical extent, remain poorly constrained. Here we shed new lights on roots through (a) a global compilation and synthesis of rooting depth observations, (b) correlations with biotic and abiotic drivers, (c) a multiscale hydrologic framework to explain the emerging patterns, and (d) global, ecosystem-level (<1km grid) inverse modeling of seasonal root water-uptake profiles driven by observed atmosphere and productivity. Results indicate highly variable uptake-depth across seasonal and local hydrologic gradients, and a far more common occurrence of deep (>5m) uptake than previous thought. Implications to past and future environmental change are briefly discussed.

  10. Plant-enhanced subsurface bioremediation of nonvolatile hydrocarbons

    SciTech Connect

    Chang, Y.Y.; Corapcioglu, M.Y.

    1998-02-01

    In recent years, phytoremediation, i.e., the use of plants to clean up soils contaminated with organics, has become a promising new area of research, particularly for in-situ cleanup of large volumes of slightly contaminated soils. A model that can be used as a predictive tool in phytoremediation operations was developed to simulate the transport and fate of a residual hydrocarbon contaminant interacting with plant roots in a partially saturated soil. Time-specific distribution of root quantity through soil, as well as root uptake of soil water and hydrocarbon, was incorporated into the model. In addition, the microbial activity in the soil rhizosphere was modeled with a biofilm theory. A sandy loam, which is dominate in soils of agricultural importance, was selected for simulations. Cotton, which has well-documented plant properties, was used as the model plant. Model parameters involving root growth and root distribution were obtained from the actual field data reported in the literature and ranges of reported literature values were used to obtain a realistic simulation of a phytoremediation operation. Following the verification of the root growth model with published experimental data, it has been demonstrated that plant characteristics such as the root radius are more dominant than contaminant properties in the overall rate of phytoremediation operation. The simulation results showed enhanced biodegradation of a hydrocarbon contaminant mostly because of increased biofilm metabolism of organic contaminants in a growing root system of cotton. Simulations also show that a high mean daily root-water uptake rate increases the contaminant retardation factors because of the resulting low water content. The ability to simulate the fate of a hydrocarbon contaminant is essential in designing technically efficient and cost-effective, plant-aided remedial strategies and in evaluating the effectiveness of a proposed phytoremediation scheme.

  11. Repression of Pseudomonas putida phenanthrene-degrading activity by plant root extracts and exudates.

    PubMed

    Rentz, Jeremy A; Alvarez, Pedro J J; Schnoor, Jerald L

    2004-06-01

    The phenanthrene-degrading activity (PDA) of Pseudomonas putida ATCC 17484 was repressed after incubation with plant root extracts of oat (Avena sativa), osage orange (Maclura pomifera), hybrid willow (Salix alba x matsudana), kou (Cordia subcordata) and milo (Thespesia populnea) and plant root exudates of oat (Avena sativa) and hybrid poplar (Populus deltoides x nigra DN34). Total organic carbon content of root extracts ranged from 103 to 395 mg l(-1). Characterization of root extracts identified acetate (not detectable to 8.0 mg l(-1)), amino acids (1.7-17.3 mg l(-1)) and glucose (1.6-14.0 mg l(-1)), indicating a complex mixture of substrates. Repression was also observed after exposure to potential root-derived substrates, including organic acids, glucose (carbohydrate) and glutamate (amino acid). Carbon source regulation (e.g. catabolite repression) was apparently responsible for the observed repression of P. putida PDA by root extracts. However, we showed that P. putida grows on root extracts and exudates as sole carbon and energy sources. Enhanced growth on root products may compensate for partial repression, because larger microbial populations are conducive to faster degradation rates. This would explain the commonly reported increase in phenanthrene removal in the rhizosphere.

  12. Analysis of peptide uptake and location of root hair-promoting peptide accumulation in plant roots.

    PubMed

    Matsumiya, Yoshiki; Taniguchi, Rikiya; Kubo, Motoki

    2012-03-01

    Peptide uptake by plant roots from degraded soybean-meal products was analyzed in Brassica rapa and Solanum lycopersicum. B. rapa absorbed about 40% of the initial water volume, whereas peptide concentration was decreased by 75% after 24 h. Analysis by reversed-phase HPLC showed that number of peptides was absorbed by the roots during soaking in degraded soybean-meal products for 24 h. Carboxyfluorescein-labeled root hair-promoting peptide was synthesized, and its localization, movement, and accumulation in roots were investigated. The peptide appeared to be absorbed by root hairs and then moved to trichoblasts. Furthermore, the peptide was moved from trichoblasts to atrichoblasts after 24 h. The peptide was accumulated in epidermal cells, suggesting that the peptide may have a function in both trichoblasts and atrichoblasts. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.

  13. Nitrogen metabolism and translocation in soybean plants subjected to root oxygen deficiency.

    PubMed

    Oliveira, Halley C; Freschi, Luciano; Sodek, Ladaslav

    2013-05-01

    Although nitrate (NO3(-)) but not ammonium (NH4(+)) improves plant tolerance to oxygen deficiency, the mechanisms involved in this phenomenon are just beginning to be understood. By using gas chromatography-mass spectrometry, we investigated the metabolic fate of (15)NO3(-) and (15)NH4(+) in soybean plants (Glycine max L. Merril cv. IAC-23) subjected to root hypoxia. This stress reduced the uptake of (15)NO3(-) and (15)NH4(+) from the medium and decreased the overall assimilation of these nitrogen sources into amino acids in roots and leaves. Root (15)NO3(-) assimilation was more affected by hypoxia than that of (15)NH4(+), resulting in enhanced nitrite and nitric oxide release in the solution. However, (15)NO3(-) was translocated in substantial amounts by xylem sap and considerable (15)NO3(-) assimilation into amino acids also occurred in the leaves, both under hypoxia and normoxia. By contrast, (15)NH4(+) assimilation occurred predominantly in roots, resulting in accumulation of mainly (15)N-alanine in this tissue during hypoxia. Analysis of lactate levels suggested higher fermentation in roots from NH4(+)-treated plants compared to the NO3(-) treatment. Thus, foliar NO3(-) assimilation may be relevant to plant tolerance to oxygen deficiency, since it would economize energy expenditure by hypoxic roots. Additionally, the involvement of nitric oxide synthesis from nitrite in the beneficial effect of NO3(-) is discussed. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  14. Silicon Enhances Water Stress Tolerance by Improving Root Hydraulic Conductance in Solanum lycopersicum L.

    PubMed Central

    Shi, Yu; Zhang, Yi; Han, Weihua; Feng, Ru; Hu, Yanhong; Guo, Jia; Gong, Haijun

    2016-01-01

    Silicon (Si) can improve drought tolerance in plants, but the mechanism is still not fully understood. Previous research has been concentrating on Si’s role in leaf water maintenance in Si accumulators, while little information is available on its role in water uptake and in less Si-accumulating plants. Here, we investigated the effects of Si on root water uptake and its role in decreasing oxidative damage in relation to root hydraulic conductance in tomato (Solanum lycopersicum ‘Zhongza No.9’) under water stress. Tomato seedlings were subjected to water stress induced by 10% (w/v) polyethylene glycol-6000 in the absence or presence of 2.5 mM added silicate. The results showed that Si addition ameliorated the inhibition in tomato growth and photosynthesis, and improved water status under water stress. The root hydraulic conductance of tomato plants was decreased under water stress, and it was significantly increased by added Si. There was no significant contribution of osmotic adjustment in Si-enhanced root water uptake under water stress. The transcriptions of plasma membrane aquaporin genes were not obviously changed by Si under water stress. Water stress increased the production of reactive oxygen species and induced oxidative damage, while added Si reversed these. In addition, Si addition increased the activities of superoxide dismutase and catalase and the levels of ascorbic acid and glutathione in the roots under stress. It is concluded that Si enhances the water stress tolerance via enhancing root hydraulic conductance and water uptake in tomato plants. Si-mediated decrease in membrane oxidative damage may have contributed to the enhanced root hydraulic conductance. PMID:26941762

  15. Silicon Enhances Water Stress Tolerance by Improving Root Hydraulic Conductance in Solanum lycopersicum L.

    PubMed

    Shi, Yu; Zhang, Yi; Han, Weihua; Feng, Ru; Hu, Yanhong; Guo, Jia; Gong, Haijun

    2016-01-01

    Silicon (Si) can improve drought tolerance in plants, but the mechanism is still not fully understood. Previous research has been concentrating on Si's role in leaf water maintenance in Si accumulators, while little information is available on its role in water uptake and in less Si-accumulating plants. Here, we investigated the effects of Si on root water uptake and its role in decreasing oxidative damage in relation to root hydraulic conductance in tomato (Solanum lycopersicum 'Zhongza No.9') under water stress. Tomato seedlings were subjected to water stress induced by 10% (w/v) polyethylene glycol-6000 in the absence or presence of 2.5 mM added silicate. The results showed that Si addition ameliorated the inhibition in tomato growth and photosynthesis, and improved water status under water stress. The root hydraulic conductance of tomato plants was decreased under water stress, and it was significantly increased by added Si. There was no significant contribution of osmotic adjustment in Si-enhanced root water uptake under water stress. The transcriptions of plasma membrane aquaporin genes were not obviously changed by Si under water stress. Water stress increased the production of reactive oxygen species and induced oxidative damage, while added Si reversed these. In addition, Si addition increased the activities of superoxide dismutase and catalase and the levels of ascorbic acid and glutathione in the roots under stress. It is concluded that Si enhances the water stress tolerance via enhancing root hydraulic conductance and water uptake in tomato plants. Si-mediated decrease in membrane oxidative damage may have contributed to the enhanced root hydraulic conductance.

  16. Transcriptional control of tissue formation throughout plant root development

    PubMed Central

    Moreno-Risueno, Miguel A.; Sozzani, Rosangela; Yardımcı, Galip Gürkan; Petricka, Jalean J.; Vernoux, Teva; Blilou, Ikram; Alonso, Jose; Winter, Cara M.; Ohler, Uwe; Scheres, Ben; Benfey, Philip N.

    2016-01-01

    Tissue patterns are dynamically maintained. Continuous formation of plant tissues during postembryonic growth requires asymmetric divisions and the specification of cell lineages. We show that the transcription factors, the BIRDs and SCARECROW, regulate lineage identity, positional signals, patterning, and formative divisions throughout Arabidopsis root growth. These transcription factors are postembryonic determinants of the ground tissue stem cells and their lineage. Upon further activation by the positional signal SHORT-ROOT (a mobile transcription factor), they direct asymmetric cell divisions and patterning of cell types. The BIRDs and SCARECROW with SHORT-ROOT organize tissue patterns at all formative steps during growth, ensuring developmental plasticity. PMID:26494755

  17. Tuned in: plant roots use sound to locate water.

    PubMed

    Gagliano, Monica; Grimonprez, Mavra; Depczynski, Martial; Renton, Michael

    2017-05-01

    Because water is essential to life, organisms have evolved a wide range of strategies to cope with water limitations, including actively searching for their preferred moisture levels to avoid dehydration. Plants use moisture gradients to direct their roots through the soil once a water source is detected, but how they first detect the source is unknown. We used the model plant Pisum sativum to investigate the mechanism by which roots sense and locate water. We found that roots were able to locate a water source by sensing the vibrations generated by water moving inside pipes, even in the absence of substrate moisture. When both moisture and acoustic cues were available, roots preferentially used moisture in the soil over acoustic vibrations, suggesting that acoustic gradients enable roots to broadly detect a water source at a distance, while moisture gradients help them to reach their target more accurately. Our results also showed that the presence of noise affected the abilities of roots to perceive and respond correctly to the surrounding soundscape. These findings highlight the urgent need to better understand the ecological role of sound and the consequences of acoustic pollution for plant as well as animal populations.

  18. Evaluating mechano-transduction and touch responses in plant roots.

    PubMed

    Swanson, Sarah J; Barker, Richard; Ye, Yonggeng; Gilroy, Simon

    2015-01-01

    Mechanical forces can be imposed on plants either from the environment, through factors such as the weather, mechanical properties of the soil and animal movement, or through the internal forces generated by the interplay between turgor-driven growth and the rigid plant cell wall. Such mechanical cues have profound effects on plant growth and development leading to responses ranging from directional growth patterns as seen, e.g., in tendrils coiling around supports, to the reprogramming of entire developmental programs. Thus, assays to assess mechanical sensitivity and response provide important tools for helping understand a wide range of plant physiological and developmental responses. Here, we describe simple assays to monitor mechanical response in the plant root system focusing on the quantification of root skewing, waving and obstacle avoidance.

  19. Composite Cucurbita pepo plants with transgenic roots as a tool to study root development

    PubMed Central

    Ilina, Elena L.; Logachov, Anton A.; Laplaze, Laurent; Demchenko, Nikolay P.; Pawlowski, Katharina; Demchenko, Kirill N.

    2012-01-01

    Background and Aims In most plant species, initiation of lateral root primordia occurs above the elongation zone. However, in cucurbits and some other species, lateral root primordia initiation and development takes place in the apical meristem of the parental root. Composite transgenic plants obtained by Agrobacterium rhizogenes-mediated transformation are known as a suitable model to study root development. The aim of the present study was to establish this transformation technique for squash. Methods The auxin-responsive promoter DR5 was cloned into the binary vectors pKGW-RR-MGW and pMDC162-GFP. Incorporation of 5-ethynyl-2′-deoxyuridine (EdU) was used to evaluate the presence of DNA-synthesizing cells in the hypocotyl of squash seedlings to find out whether they were suitable for infection. Two A. rhizogenes strains, R1000 and MSU440, were used. Roots containing the respective constructs were selected based on DsRED1 or green fluorescent protein (GFP) fluorescence, and DR5::Egfp-gusA or DR5::gusA insertion, respectively, was verified by PCR. Distribution of the response to auxin was visualized by GFP fluorescence or β-glucuronidase (GUS) activity staining and confirmed by immunolocalization of GFP and GUS proteins, respectively. Key Results Based on the distribution of EdU-labelled cells, it was determined that 6-day-old squash seedlings were suited for inoculation by A. rhizogenes since their root pericycle and the adjacent layers contain enough proliferating cells. Agrobacterium rhizogenes R1000 proved to be the most virulent strain on squash seedlings. Squash roots containing the respective constructs did not exhibit the hairy root phenotype and were morphologically and structurally similar to wild-type roots. Conclusions The auxin response pattern in the root apex of squash resembled that in arabidopsis roots. Composite squash plants obtained by A. rhizogenes-mediated transformation are a good tool for the investigation of root apical meristem

  20. Performance of Slash Pine Bare-Root Seedlings and Containerized Rooted Cuttings Planted on Five Dates in Louisiana

    Treesearch

    Alper Akgul; Michael G. Messina; Alan Wilson; Joe Weber

    2004-01-01

    Landowners are interested in extending the normal planting season, as well as the comparative field performance, of nursery bare-root seedlings and containerized rooted cuttings. The effect of seasonal planting dates on field performance of two stock types of slash pine (Pinus elliottii Engelm.) was examined. Slash pine bare-root seedlings (BRS) and...

  1. Unleashing the potential of the root hair cell as a single plant cell type model in root systems biology.

    PubMed

    Qiao, Zhenzhen; Libault, Marc

    2013-01-01

    Plant root is an organ composed of multiple cell types with different functions. This multicellular complexity limits our understanding of root biology because -omics studies performed at the level of the entire root reflect the average responses of all cells composing the organ. To overcome this difficulty and allow a more comprehensive understanding of root cell biology, an approach is needed that would focus on one single cell type in the plant root. Because of its biological functions (i.e., uptake of water and various nutrients; primary site of infection by nitrogen-fixing bacteria in legumes), the root hair cell is an attractive single cell model to study root cell response to various stresses and treatments. To fully study their biology, we have recently optimized procedures in obtaining root hair cell samples. We culture the plants using an ultrasound aeroponic system maximizing root hair cell density on the entire root systems and allowing the homogeneous treatment of the root system. We then isolate the root hair cells in liquid nitrogen. Isolated root hair yields could be up to 800 to 1000~mg of plant cells from 60 root systems. Using soybean as a model, the purity of the root hair was assessed by comparing the expression level of genes previously identified as soybean root hair specific between preparations of isolated root hair cells and stripped roots, roots devoid in root hairs. Enlarging our tests to include other plant species, our results support the isolation of large quantities of highly purified root hair cells which is compatible with a systems biology approach.

  2. Enhancement of root growth and nitrogen fixation in Trigonella by UV-exclusion from solar radiation.

    PubMed

    Sharma, Sonika; Guruprasad, K N

    2012-12-01

    A field experiment was conducted to study the impact of solar UV on root growth and nitrogen fixation in Trigonella foenum-graecum. Plants were grown in iron mesh cages covered with polyester filters that could specifically cut off UV-B (280-315 nm) or UV-A + B (280-400 nm) part of the solar spectrum. The control plants were grown under a polythene filter transmissible to UV. Root biomass, number of nodules and nodule fresh weight were enhanced after exclusion of solar UV. Nitrogenase activity was significantly enhanced by 120% and 80% in the UV-B and UV-A + B excluded plants respectively. Along with nitrogenase there was concomitant increase in leghemoglobin and hemechrome content in the nodules after exclusion of solar UV. These components of sunlight limits nitrogen fixation and their elimination can enhance nitrogen fixation with agricultural advantages like reduction in the use of fertilizers. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  3. Role of root microbiota in plant productivity

    PubMed Central

    Tkacz, Andrzej; Poole, Philip

    2015-01-01

    The growing human population requires increasing amounts of food, but modern agriculture has limited possibilities for increasing yields. New crop varieties may be bred to have increased yields and be more resistant to environmental stress and pests. However, they still require fertilization to supplement essential nutrients that are normally limited in the soil. Soil microorganisms present an opportunity to reduce the requirement for inorganic fertilization in agriculture. Microorganisms, due to their enormous genetic pool, are also a potential source of biochemical reactions that recycle essential nutrients for plant growth. Microbes that associate with plants can be considered to be part of the plant’s pan-genome. Therefore, it is essential for us to understand microbial community structure and their ‘metagenome’ and how it is influenced by different soil types and crop varieties. In the future we may be able to modify and better utilize the soil microbiota potential for promoting plant growth. PMID:25908654

  4. Root Branching Is a Leading Root Trait of the Plant Economics Spectrum in Temperate Trees

    PubMed Central

    Liese, Rebecca; Alings, Katrin; Meier, Ina C.

    2017-01-01

    lifespan. We conclude that branching of lower order roots can be considered a leading root trait of the plant economics spectrum of temperate trees, since it relates to the mycorrhizal association type and belowground resource exploitation; while the dominance of the phylogenetic signal over environmental filtering makes morphological root traits less central for tree economics spectra across different environments. PMID:28337213

  5. Root Branching Is a Leading Root Trait of the Plant Economics Spectrum in Temperate Trees.

    PubMed

    Liese, Rebecca; Alings, Katrin; Meier, Ina C

    2017-01-01

    lifespan. We conclude that branching of lower order roots can be considered a leading root trait of the plant economics spectrum of temperate trees, since it relates to the mycorrhizal association type and belowground resource exploitation; while the dominance of the phylogenetic signal over environmental filtering makes morphological root traits less central for tree economics spectra across different environments.

  6. DynamicRoots: A Software Platform for the Reconstruction and Analysis of Growing Plant Roots.

    PubMed

    Symonova, Olga; Topp, Christopher N; Edelsbrunner, Herbert

    2015-01-01

    We present a software platform for reconstructing and analyzing the growth of a plant root system from a time-series of 3D voxelized shapes. It aligns the shapes with each other, constructs a geometric graph representation together with the function that records the time of growth, and organizes the branches into a hierarchy that reflects the order of creation. The software includes the automatic computation of structural and dynamic traits for each root in the system enabling the quantification of growth on fine-scale. These are important advances in plant phenotyping with applications to the study of genetic and environmental influences on growth.

  7. Root-parasitic nematodes enhance soil microbial activities and nitrogen mineralization.

    PubMed

    Tu, C; Koenning, S R; Hu, S

    2003-07-01

    Obligate root-parasitic nematodes can affect soil microbes positively by enhancing C and nutrient leakage from roots but negatively by restricting total root growth. However, it is unclear how the resulting changes in C availability affect soil microbial activities and N cycling. In a microplot experiment, effects of root-parasitic reniform nematodes ( Rotylenchulus reniformis) on soil microbial biomass and activities were examined in six different soils planted with cotton. Rotylenchulus reniformis was introduced at 900 nematodes kg(-1) soil in May 2000 prior to seeding cotton. In 2001, soil samples were collected in May before cotton was seeded and in November at the final harvest. Extractable C and N were consistently higher in the R. reniformis treatments than in the non-nematode controls across the six different soils. Nematode inoculation significantly reduced microbial biomass C, but increased microbial biomass N, leading to marked decreases in microbial biomass C:N ratios. Soil microbial respiration and net N mineralization rates were also consistently higher in the nematode treatments than in the controls. However, soil types did not have a significant impact on the effects of nematodes on these microbial parameters. These findings indicate that nematode infection of plant roots may enhance microbial activities and the turnover of soil microbial biomass, facilitating soil N cycling. The present study provides the first evidence about the direct role of root-feeding nematodes in enhancing soil N mineralization.

  8. Enhanced root production in Haplopappus gracilis grown under spaceflight conditions

    NASA Technical Reports Server (NTRS)

    Levine, H. G.; Krikorian, A. D.

    1996-01-01

    The production and growth of roots in two aseptically maintained clonal populations of Haplopappus gracilis (family Compositae), each with a distinctive pattern of root production, were studied after they had been exposed to space for 5 days aboard a NASA Space Shuttle. Total root production of both populations was 67-95% greater when compared with their Earth-grown controls. Roots were generated: (1) laterally from pre-formed roots, the tips of which had been severed at the time of plantlet insertion into a "horticultural foam" substrate supplied with a nutrient solution; (2) adventitiously from the basal or cut-end portion of shoots; (3) de novo, i.e. from primordial which were non-existent at the outset of the experiment. Roots grew in all directions in space but were uniformly positively gravitropic in ground controls. In space and on Earth, both clonal populations maintained their clone-specific root formation and growth characteristics and produced an equivalent amount of tissue when compared to each other. As on Earth, and as expected, there were fewer and shorter roots on plantlets that formed floral buds. The significance of altered moisture distribution in the "horticultural foam" substrate in space for root growth and the significance of our findings for growing plants in altered gravity environments are discussed.

  9. Enhanced root production in Haplopappus gracilis grown under spaceflight conditions

    NASA Technical Reports Server (NTRS)

    Levine, H. G.; Krikorian, A. D.

    1996-01-01

    The production and growth of roots in two aseptically maintained clonal populations of Haplopappus gracilis (family Compositae), each with a distinctive pattern of root production, were studied after they had been exposed to space for 5 days aboard a NASA Space Shuttle. Total root production of both populations was 67-95% greater when compared with their Earth-grown controls. Roots were generated: (1) laterally from pre-formed roots, the tips of which had been severed at the time of plantlet insertion into a "horticultural foam" substrate supplied with a nutrient solution; (2) adventitiously from the basal or cut-end portion of shoots; (3) de novo, i.e. from primordial which were non-existent at the outset of the experiment. Roots grew in all directions in space but were uniformly positively gravitropic in ground controls. In space and on Earth, both clonal populations maintained their clone-specific root formation and growth characteristics and produced an equivalent amount of tissue when compared to each other. As on Earth, and as expected, there were fewer and shorter roots on plantlets that formed floral buds. The significance of altered moisture distribution in the "horticultural foam" substrate in space for root growth and the significance of our findings for growing plants in altered gravity environments are discussed.

  10. Enhanced root production in Haplopappus gracilis grown under spaceflight conditions.

    PubMed

    Levine, H G; Krikorian, A D

    1996-04-01

    The production and growth of roots in two aseptically maintained clonal populations of Haplopappus gracilis (family Compositae), each with a distinctive pattern of root production, were studied after they had been exposed to space for 5 days aboard a NASA Space Shuttle. Total root production of both populations was 67-95% greater when compared with their Earth-grown controls. Roots were generated: (1) laterally from pre-formed roots, the tips of which had been severed at the time of plantlet insertion into a "horticultural foam" substrate supplied with a nutrient solution; (2) adventitiously from the basal or cut-end portion of shoots; (3) de novo, i.e. from primordial which were non-existent at the outset of the experiment. Roots grew in all directions in space but were uniformly positively gravitropic in ground controls. In space and on Earth, both clonal populations maintained their clone-specific root formation and growth characteristics and produced an equivalent amount of tissue when compared to each other. As on Earth, and as expected, there were fewer and shorter roots on plantlets that formed floral buds. The significance of altered moisture distribution in the "horticultural foam" substrate in space for root growth and the significance of our findings for growing plants in altered gravity environments are discussed.

  11. Defense mutualisms enhance plant diversification

    PubMed Central

    Weber, Marjorie G.; Agrawal, Anurag A.

    2014-01-01

    The ability of plants to form mutualistic relationships with animal defenders has long been suspected to influence their evolutionary success, both by decreasing extinction risk and by increasing opportunity for speciation through an expanded realized niche. Nonetheless, the hypothesis that defense mutualisms consistently enhance plant diversification across lineages has not been well tested due to a lack of phenotypic and phylogenetic information. Using a global analysis, we show that the >100 vascular plant families in which species have evolved extrafloral nectaries (EFNs), sugar-secreting organs that recruit arthropod mutualists, have twofold higher diversification rates than families that lack species with EFNs. Zooming in on six distantly related plant clades, trait-dependent diversification models confirmed the tendency for lineages with EFNs to display increased rates of diversification. These results were consistent across methodological approaches. Inference using reversible-jump Markov chain Monte Carlo (MCMC) to model the placement and number of rate shifts revealed that high net diversification rates in EFN clades were driven by an increased number of positive rate shifts following EFN evolution compared with sister clades, suggesting that EFNs may be indirect facilitators of diversification. Our replicated analysis indicates that defense mutualisms put lineages on a path toward increased diversification rates within and between clades, and is concordant with the hypothesis that mutualistic interactions with animals can have an impact on deep macroevolutionary patterns and enhance plant diversity. PMID:25349406

  12. Defense mutualisms enhance plant diversification.

    PubMed

    Weber, Marjorie G; Agrawal, Anurag A

    2014-11-18

    The ability of plants to form mutualistic relationships with animal defenders has long been suspected to influence their evolutionary success, both by decreasing extinction risk and by increasing opportunity for speciation through an expanded realized niche. Nonetheless, the hypothesis that defense mutualisms consistently enhance plant diversification across lineages has not been well tested due to a lack of phenotypic and phylogenetic information. Using a global analysis, we show that the >100 vascular plant families in which species have evolved extrafloral nectaries (EFNs), sugar-secreting organs that recruit arthropod mutualists, have twofold higher diversification rates than families that lack species with EFNs. Zooming in on six distantly related plant clades, trait-dependent diversification models confirmed the tendency for lineages with EFNs to display increased rates of diversification. These results were consistent across methodological approaches. Inference using reversible-jump Markov chain Monte Carlo (MCMC) to model the placement and number of rate shifts revealed that high net diversification rates in EFN clades were driven by an increased number of positive rate shifts following EFN evolution compared with sister clades, suggesting that EFNs may be indirect facilitators of diversification. Our replicated analysis indicates that defense mutualisms put lineages on a path toward increased diversification rates within and between clades, and is concordant with the hypothesis that mutualistic interactions with animals can have an impact on deep macroevolutionary patterns and enhance plant diversity.

  13. Root exudates drive interspecific facilitation by enhancing nodulation and N2 fixation.

    PubMed

    Li, Bai; Li, Yu-Ying; Wu, Hua-Mao; Zhang, Fang-Fang; Li, Chun-Jie; Li, Xue-Xian; Lambers, Hans; Li, Long

    2016-06-07

    Plant diversity in experimental systems often enhances ecosystem productivity, but the mechanisms causing this overyielding are only partly understood. Intercropping faba beans (Vicia faba L.) and maize (Zea mays L.) result in overyielding and also, enhanced nodulation by faba beans. By using permeable and impermeable root barriers in a 2-y field experiment, we show that root-root interactions between faba bean and maize significantly increase both nodulation and symbiotic N2 fixation in intercropped faba bean. Furthermore, root exudates from maize promote faba bean nodulation, whereas root exudates from wheat and barley do not. Thus, a decline of soil nitrate concentrations caused by intercropped cereals is not the sole mechanism for maize promoting faba bean nodulation. Intercropped maize also caused a twofold increase in exudation of flavonoids (signaling compounds for rhizobia) in the systems. Roots of faba bean treated with maize root exudates exhibited an immediate 11-fold increase in the expression of chalcone-flavanone isomerase (involved in flavonoid synthesis) gene together with a significantly increased expression of genes mediating nodulation and auxin response. After 35 d, faba beans treated with maize root exudate continued to show up-regulation of key nodulation genes, such as early nodulin 93 (ENOD93), and promoted nitrogen fixation. Our results reveal a mechanism for how intercropped maize promotes nitrogen fixation of faba bean, where maize root exudates promote flavonoid synthesis in faba bean, increase nodulation, and stimulate nitrogen fixation after enhanced gene expression. These results indicate facilitative root-root interactions and provide a mechanism for a positive relationship between species diversity and ecosystem productivity.

  14. Humic Acids Isolated from Earthworm Compost Enhance Root Elongation, Lateral Root Emergence, and Plasma Membrane H+-ATPase Activity in Maize Roots1

    PubMed Central

    Canellas, Luciano Pasqualoto; Olivares, Fabio Lopes; Okorokova-Façanha, Anna L.; Façanha, Arnoldo Rocha

    2002-01-01

    Earthworms (Eisenia foetida) produce humic substances that can influence plant growth by mechanisms that are not yet clear. In this work, we investigated the effects of humic acids (HAs) isolated from cattle manure earthworm compost on the earliest stages of lateral root development and on the plasma membrane H+-ATPase activity. These HAs enhance the root growth of maize (Zea mays) seedlings in conjunction with a marked proliferation of sites of lateral root emergence. They also stimulate the plasma membrane H+-ATPase activity, apparently associated with an ability to promote expression of this enzyme. In addition, structural analysis reveals the presence of exchangeable auxin groups in the macrostructure of the earthworm compost HA. These results may shed light on the hormonal activity that has been postulated for these humic substances. PMID:12481077

  15. Humic acids isolated from earthworm compost enhance root elongation, lateral root emergence, and plasma membrane H+-ATPase activity in maize roots.

    PubMed

    Canellas, Luciano Pasqualoto; Olivares, Fabio Lopes; Okorokova-Façanha, Anna L; Façanha, Arnoldo Rocha

    2002-12-01

    Earthworms (Eisenia foetida) produce humic substances that can influence plant growth by mechanisms that are not yet clear. In this work, we investigated the effects of humic acids (HAs) isolated from cattle manure earthworm compost on the earliest stages of lateral root development and on the plasma membrane H(+)-ATPase activity. These HAs enhance the root growth of maize (Zea mays) seedlings in conjunction with a marked proliferation of sites of lateral root emergence. They also stimulate the plasma membrane H(+)-ATPase activity, apparently associated with an ability to promote expression of this enzyme. In addition, structural analysis reveals the presence of exchangeable auxin groups in the macrostructure of the earthworm compost HA. These results may shed light on the hormonal activity that has been postulated for these humic substances.

  16. Enhanced phenanthrene biodegradation in soil by slender oat root exudates and root debris.

    PubMed

    Miya, R K; Firestone, M K

    2001-01-01

    To investigate the mechanisms by which slender oat (Avena barbata Pott ex Link) enhances phenanthrene biodegradation, we analyzed the impacts of root exudates and root debris on phenanthrene biodegradation and degrader community dynamics. Accelerated phenanthrene biodegradation rates occurred in soils amended with slender oat root exudates as well as combined root debris + root exudate as compared with unamended controls. Root exudates significantly enhanced phenanthrene biodegradation in rhizosphere soils, either by increasing contaminant bioavailability and/or increasing microbial population size and activity. A modified most probable number (MPN) method was used to determine quantitative shifts in heterotrophic and phenanthrene degrader communities. During the first 4 to 6 d of treatment, heterotrophic populations increased in all amended soils. Both root debris-amended and exudate-amended soil then maintained larger phenanthrene degrader populations than in control soils later in the experiment after much of the phenanthrene had been utilized. Thus, root amendments had a greater impact over time on phenanthrene degraders than heterotrophs resulting in selective maintenance of degrader populations in amended soils compared with controls.

  17. Allometric scaling laws for water uptake by plant roots.

    PubMed

    Biondini, Mario

    2008-03-07

    This paper develops scaling laws for plant roots of any arbitrary volume and branching configuration that maximize water uptake. Water uptake can occur along any part of the root network, and thus there is no branch-to-branch fluid conservation. Maximizing water uptake, therefore, involves balancing two flows that are inversely related: axial and radial conductivity. The scaling laws are tested against the root data of 1759 plants from 77 herbaceous species, and compared with those from the WBE model. I further discuss whether the scaling laws are invariant to soil water distribution. A summary of some of the results follows. (1) The optimal radius for a single root (no branches) scales with volume as r approximately volume(2/(8+a))(0root radius branches (r(i+1)=beta*r(i)) is of the form beta=f(N)((2*epsilon(N))/(8+a)), where f(N)=A(N)/(n(b)*(1+A(N))), n(b) is the number of branches, and A(N) and epsilon(N) are functions of the number of root diameter classes (not constants as in the WBE model). (3) For large N, beta converges to the beta from the WBE model. For small N, the beta's for the two models diverge, but are highly correlated. (4) The fractal assumption of volume filling of the WBE model are also met in the root model even though they are not explicitly incorporated into it. (5) The WBE model for rigid tubes is an asymptotic solution for large root systems (large N and biomass). (6) The optimal scaling solutions for the root network appears to be independent of soil water distribution or water demand. The data set used for testing is included in the electronic supplementary archive of the journal.

  18. Lessons learned from non-medical industries: root cause analysis as culture change at a chemical plant

    PubMed Central

    Carroll, J; Rudolph, J; Hatakenaka, S

    2002-01-01

    

 Root cause analysis was introduced to a chemical plant as a way of enhancing performance and safety, exemplified by the investigation of an explosion. The cultural legacy of the root cause learning intervention was embodied in managers' increased openness to new ideas, individuals' questioning attitude and disciplined thinking, and a root cause analysis process that provided continual opportunities to learn and improve. Lessons for health care are discussed, taking account of differences between the chemical and healthcare industries. PMID:12486993

  19. Abiotic stress responses in plant roots: a proteomics perspective

    PubMed Central

    Ghosh, Dipanjana; Xu, Jian

    2014-01-01

    Abiotic stress conditions adversely affect plant growth, resulting in significant decline in crop productivity. To mitigate and recover from the damaging effects of such adverse environmental conditions, plants have evolved various adaptive strategies at cellular and metabolic levels. Most of these strategies involve dynamic changes in protein abundance that can be best explored through proteomics. This review summarizes comparative proteomic studies conducted with roots of various plant species subjected to different abiotic stresses especially drought, salinity, flood, and cold. The main purpose of this article is to highlight and classify the protein level changes in abiotic stress response pathways specifically in plant roots. Shared as well as stressor-specific proteome signatures and adaptive mechanism(s) are simultaneously described. Such a comprehensive account will facilitate the design of genetic engineering strategies that enable the development of broad-spectrum abiotic stress-tolerant crops. PMID:24478786

  20. Fluorescence Imaging of the Cytoskeleton in Plant Roots.

    PubMed

    Dyachok, Julia; Paez-Garcia, Ana; Yoo, Cheol-Min; Palanichelvam, Karuppaiah; Blancaflor, Elison B

    2016-01-01

    During the past two decades the use of live cytoskeletal probes has increased dramatically due to the introduction of the green fluorescent protein. However, to make full use of these live cell reporters it is necessary to implement simple methods to maintain plant specimens in optimal growing conditions during imaging. To image the cytoskeleton in living Arabidopsis roots, we rely on a system involving coverslips coated with nutrient supplemented agar where the seeds are directly germinated. This coverslip system can be conveniently transferred to the stage of a confocal microscope with minimal disturbance to the growth of the seedling. For roots with a larger diameter such as Medicago truncatula, seeds are first germinated in moist paper, grown vertically in between plastic trays, and roots mounted on glass slides for confocal imaging. Parallel with our live cell imaging approaches, we routinely process fixed plant material via indirect immunofluorescence. For these methods we typically use non-embedded vibratome-sectioned and whole mount permeabilized root tissue. The clearly defined developmental regions of the root provide us with an elegant system to further understand the cytoskeletal basis of plant development.

  1. Root ABA Accumulation Enhances Rice Seedling Drought Tolerance under Ammonium Supply: Interaction with Aquaporins

    PubMed Central

    Ding, Lei; Li, Yingrui; Wang, Ying; Gao, Limin; Wang, Min; Chaumont, François; Shen, Qirong; Guo, Shiwei

    2016-01-01

    In previous studies, we demonstrated that ammonium nutrition enhances the drought tolerance of rice seedlings compared to nitrate nutrition and contributes to a higher root water uptake ability. It remains unclear why rice seedlings maintain a higher water uptake ability when supplied with ammonium under drought stress. Here, we focused on the effects of nitrogen form and drought stress on root abscisic acid (ABA) concentration and aquaporin expression using hydroponics experiments and stimulating drought stress with 10% PEG6000. Drought stress decreased the leaf photosynthetic rate and stomatal conductivity and increased the leaf temperature of plants supplied with either ammonium or nitrate, but especially under nitrate supply. After 4 h of PEG treatment, the root protoplast water permeability and the expression of root PIP and TIP genes decreased in plants supplied with ammonium or nitrate. After 24 h of PEG treatment, the root hydraulic conductivity, the protoplast water permeability, and the expression of some aquaporin genes increased in plants supplied with ammonium compared to those under non-PEG treatment. Root ABA accumulation was induced by 24 h of PEG treatment, especially in plants supplied with ammonium. The addition of exogenous ABA decreased the expression of PIP and TIP genes under non-PEG treatment but increased the expression of some of them under PEG treatment. We concluded that drought stress induced a down-regulation of aquaporin expression, which appeared earlier than did root ABA accumulation. With continued drought stress, aquaporin expression and activity increased due to root ABA accumulation in plants supplied with ammonium. PMID:27559341

  2. Development and recovery of iron deficiency by iron resupply to roots or leaves of strawberry plants.

    PubMed

    Pestana, Maribela; Correia, Pedro José; Saavedra, Teresa; Gama, Florinda; Abadía, Anunciación; de Varennes, Amarilis

    2012-04-01

    Bare-root transplants of strawberry (Fragaria ananassa Duch. cv. 'Selva') were transferred to nutrient solutions with or without iron (Fe). After six weeks of growth, plants grown in solution lacking Fe were chlorotic and showed morphological changes in roots typical of Fe deficiency. Subsequently, four treatments were applied for nine days: plants grown in continued absence of Fe (Fe0); plants grown in continued presence of 10 μM Fe (Fe10); foliar application of ferrous sulphate every two days to chlorotic plants (Fe-leaves); and growth of chlorotic plants in solution with ferrous sulphate (Fe-solution). After six days, the chlorophyll (Chl) content in leaves of Fe-solution plants was similar to that in Fe10 plants. Under the Fe-leaves treatment, a slight regreening of new leaves was observed only by the end of the experiment. After nine days, ferric chelate reductase (FC-R) activity was unchanged in Fe10 but increased in Fe0 plants. The FC-R activity of Fe-solution plants was similar to the initial value for chlorotic plants, whereas it was reduced drastically under the Fe-leaves treatment. The Fe concentration in leaves of Fe0 and Fe10 was similar, whereas the Fe-solution and Fe-leaves treatments enhanced leaf Fe concentration. In contrast to the Fe-solution treatment, foliar application of Fe did not increase the Fe concentration in roots. Under our experimental conditions, FC-R activity in strawberry appeared to be deactivated rapidly by pulses of Fe applied by foliar sprays. Deactivation was slower if Fe was applied directly to roots, which suggested that the plants had greater opportunity to take Fe.

  3. Plant responsiveness to root–root communication of stress cues

    PubMed Central

    Falik, Omer; Mordoch, Yonat; Ben-Natan, Daniel; Vanunu, Miriam; Goldstein, Oron; Novoplansky, Ariel

    2012-01-01

    Background and Aims Phenotypic plasticity is based on the organism's ability to perceive, integrate and respond to multiple signals and cues informative of environmental opportunities and perils. A growing body of evidence demonstrates that plants are able to adapt to imminent threats by perceiving cues emitted from their damaged neighbours. Here, the hypothesis was tested that unstressed plants are able to perceive and respond to stress cues emitted from their drought- and osmotically stressed neighbours and to induce stress responses in additional unstressed plants. Methods Split-root Pisum sativum, Cynodon dactylon, Digitaria sanguinalis and Stenotaphrum secundatum plants were subjected to osmotic stress or drought while sharing one of their rooting volumes with an unstressed neighbour, which in turn shared its other rooting volume with additional unstressed neighbours. Following the kinetics of stomatal aperture allowed testing for stress responses in both the stressed plants and their unstressed neighbours. Key Results In both P. sativum plants and the three wild clonal grasses, infliction of osmotic stress or drought caused stomatal closure in both the stressed plants and in their unstressed neighbours. While both continuous osmotic stress and drought induced prolonged stomatal closure and limited acclimation in stressed plants, their unstressed neighbours habituated to the stress cues and opened their stomata 3–24 h after the beginning of stress induction. Conclusions The results demonstrate a novel type of plant communication, by which plants might be able to increase their readiness to probable future osmotic and drought stresses. Further work is underway to decipher the identity and mode of operation of the involved communication vectors and to assess the potential ecological costs and benefits of emitting and perceiving drought and osmotic stress cues under various ecological scenarios. PMID:22408186

  4. Sodium efflux in plant roots: what do we really know?

    PubMed

    Britto, D T; Kronzucker, H J

    2015-08-15

    The efflux of sodium (Na(+)) ions across the plasma membrane of plant root cells into the external medium is surprisingly poorly understood. Nevertheless, Na(+) efflux is widely regarded as a major mechanism by which plants restrain the rise of Na(+) concentrations in the cytosolic compartments of root cells and, thus, achieve a degree of tolerance to saline environments. In this review, several key ideas and bodies of evidence concerning root Na(+) efflux are summarized with a critical eye. Findings from decades past are brought to bear on current thinking, and pivotal studies are discussed, both "purely physiological", and also with regard to the SOS1 protein, the only major Na(+) efflux transporter that has, to date, been genetically characterized. We find that the current model of rapid transmembrane sodium cycling (RTSC), across the plasma membrane of root cells, is not adequately supported by evidence from the majority of efflux studies. An alternative hypothesis cannot be ruled out, that most Na(+) tracer efflux from the root in the salinity range does not proceed across the plasma membrane, but through the apoplast. Support for this idea comes from studies showing that Na(+) efflux, when measured with tracers, is rarely affected by the presence of inhibitors or the ionic composition in saline rooting media. We conclude that the actual efflux of Na(+) across the plasma membrane of root cells may be much more modest than what is often reported in studies using tracers, and may predominantly occur in the root tips, where SOS1 expression has been localized. Copyright © 2015 Elsevier GmbH. All rights reserved.

  5. Benefits of flooding-induced aquatic adventitious roots depend on the duration of submergence: linking plant performance to root functioning.

    PubMed

    Zhang, Qian; Huber, Heidrun; Beljaars, Simone J M; Birnbaum, Diana; de Best, Sander; de Kroon, Hans; Visser, Eric J W

    2017-07-01

    Temporal flooding is a common environmental stress for terrestrial plants. Aquatic adventitious roots (aquatic roots) are commonly formed in flooding-tolerant plant species and are generally assumed to be beneficial for plant growth by supporting water and nutrient uptake during partial flooding. However, the actual contribution of these roots to plant performance under flooding has hardly been quantified. As the investment into aquatic root development in terms of carbohydrates may be costly, these costs may - depending on the specific environmental conditions - offset the beneficial effects of aquatic roots. This study tested the hypothesis that the balance between potential costs and benefits depends on the duration of flooding, as the benefits are expected to outweigh the costs in long-term but not in short-term flooding. The contribution of aquatic roots to plant performance was tested in Solanum dulcamara during 1-4 weeks of partial submergence and by experimentally manipulating root production. Nutrient uptake by aquatic roots, transpiration and photosynthesis were measured in plants differing in aquatic root development to assess the specific function of these roots. As predicted, flooded plants benefited from the presence of aquatic roots. The results showed that this was probably due to the contribution of roots to resource uptake. However, these beneficial effects were only present in long-term but not in short-term flooding. This relationship could be explained by the correlation between nutrient uptake and the flooding duration-dependent size of the aquatic root system. The results indicate that aquatic root formation is likely to be selected for in habitats characterized by long-term flooding. This study also revealed only limited costs associated with adventitious root formation, which may explain the maintenance of the ability to produce aquatic roots in habitats characterized by very rare or short flooding events.

  6. Deep rooting conferred by DEEPER ROOTING 1 enhances rice yield in paddy fields

    PubMed Central

    Arai-Sanoh, Yumiko; Takai, Toshiyuki; Yoshinaga, Satoshi; Nakano, Hiroshi; Kojima, Mikiko; Sakakibara, Hitoshi; Kondo, Motohiko; Uga, Yusaku

    2014-01-01

    To clarify the effect of deep rooting on grain yield in rice (Oryza sativa L.) in an irrigated paddy field with or without fertilizer, we used the shallow-rooting IR64 and the deep-rooting Dro1-NIL (a near-isogenic line homozygous for the Kinandang Patong allele of DEEPER ROOTING 1 (DRO1) in the IR64 genetic background). Although total root length was similar in both lines, more roots were distributed within the lower soil layer of the paddy field in Dro1-NIL than in IR64, irrespective of fertilizer treatment. At maturity, Dro1-NIL showed approximately 10% higher grain yield than IR64, irrespective of fertilizer treatment. Higher grain yield of Dro1-NIL was mainly due to the increased 1000-kernel weight and increased percentage of ripened grains, which resulted in a higher harvest index. After heading, the uptake of nitrogen from soil and leaf nitrogen concentration were higher in Dro1-NIL than in IR64. At the mid-grain-filling stage, Dro1-NIL maintained higher cytokinin fluxes from roots to shoots than IR64. These results suggest that deep rooting by DRO1 enhances nitrogen uptake and cytokinin fluxes at late stages, resulting in better grain filling in Dro1-NIL in a paddy field in this study. PMID:24988911

  7. Hydraulic resistance of a plant root to water-uptake: A slender-body theory.

    PubMed

    Chen, Kang Ping

    2016-05-07

    A slender-body theory for calculating the hydraulic resistance of a single plant root is developed. The work provides an in-depth discussion on the procedure and the assumptions involved in calculating a root׳s internal hydraulic resistance as well as the physical and the mathematical aspects of the external three-dimensional flow around the tip of a root in a saturated soil and how this flow pattern enhances uptake and reduces hydraulic resistance. Analytical solutions for the flux density distribution on the stele-cortex interface, local water-uptake profile inside the stele core, the overall water-uptake at the base of the stele, and the total hydraulic resistance of a root are obtained in the slender-body limit. It is shown that a key parameter controlling a root's hydraulic resistance is the dimensionless axial conductivity in the stele, which depends on the permeabilities of the stele and the cortex as well as the root's radial and axial dimensions. Three-dimensional tip effect reduces a root's hydraulic resistance by as much as 36% when compared to the radial flow theory of Landsberg and Fowkes. In addition, the total hydraulic resistance cannot be generally decomposed into the direct sum of a radial resistance and an axial resistance.

  8. Enhanced hyphal growth of arbuscular mycorrhizae by root exudates derived from high R/FR treated Lotus japonicus.

    PubMed

    Nagata, Maki; Yamamoto, Naoya; Miyamoto, Taro; Shimomura, Aya; Arima, Susumu; Hirsch, Ann M; Suzuki, Akihiro

    2016-06-02

    Red/Far Red (R/FR) sensing positively influences the arbuscular mycorrhizal (AM) symbiosis of both legume and nonlegume plants through jasmonic acid (JA) and strigolactone signaling. We previously reported that root exudates obtained from high R/FR-grown plants contained more strigolactone than low R/FR-grown plants. To determine whether JA and JA derivatives were secreted from roots, we investigated the expression levels of JA-responsive genes in L. japonicus Miyakojima MG20 plants treated with root exudates prepared from either high or low R/FR light-treated plants. The root exudates from high R/FR light-treated plants were found to enhance the expression levels of JA-responsive genes significantly. Moreover, exogenous JA increased AM fungal hyphal elongation as did the root exudates derived from high R/FR-grown L. japonicus plants. We conclude that increased JA accumulation and secretion into root exudates from high R/FR light-grown plants is the best explanation for increased colonization and enhanced mycorrhization under these conditions.

  9. Is nutrient uptake by plant roots sensitive to the rate of mass flow? Reappraisal of an old chestnut for spatially distributed root systems

    NASA Astrophysics Data System (ADS)

    McMurtrie, R. E.; Näsholm, T.

    2015-12-01

    Numerous modelling papers have considered the contribution of mass flow to nutrient uptake by a single plant root, but few have evaluated its contribution at the scale of an entire root system. We derive equations for nitrogen (N) influx per unit root surface area (J) and N uptake by a single root (U) as functions of soil nitrogen supply, root-length density (RLD) and the velocity of water at the root surface (vo). This model of N uptake by a single root can be used to evaluate N uptake by an entire root system if spatial distributions are known for soil N supply, root biomass and water-uptake velocity. In this paper we show that spatial distributions of RLD and vo can be estimated simultaneously under an optimisation hypothesis (MaxNup, McMurtrie et al. 2012), according to which total root mass and total water uptake are distributed vertically in order to maximise total N uptake. The MaxNup hypothesis leads to equations for optimal vertical profiles of RLD, vo, J and U, maximum rooting depth and the fraction of total available soil nitrogen taken up by the root system. Predicted values of vo are enhanced at depths where nitrogen influx per unit root surface area (J) is more sensitive to vo and diminished at depths where J is less sensitive to vo. Predicted vo is largest at the base of the root system where RLD is lowest, and is smallest in upper soil layers where RLD is highest. MaxNup thus predicts that water uptake will be distributed preferentially to soil depths where it will enhance nitrogen uptake U; this tendency will amplify the sensitivity of total N uptake to total water uptake, compared with strategies where vo is the same for all roots, or where vo is elevated for roots in upper soil layers. Reference McMurtrie RE, Iversen CM, Dewar RC, Medlyn BE, Näsholm T, Pepper DA, Norby RJ. 2012. Plant root distributions and nitrogen uptake predicted by a hypothesis of optimal root foraging. Ecology and Evolution 2: 1235-1250.

  10. Nitrate reductase-mediated NO production enhances Cd accumulation in Panax notoginseng roots by affecting root cell wall properties.

    PubMed

    Kan, Qi; Wu, Wenwei; Yu, Wenqian; Zhang, Jiarong; Xu, Jin; Rengel, Zed; Chen, Limei; Cui, Xiuming; Chen, Qi

    2016-04-01

    Panax notoginseng (Burk) F. H. Chen is a traditional medicinal herb in China. However, the high capacity of its roots to accumulate cadmium (Cd) poses a potential risk to human health. Although there is some evidence for the involvement of nitric oxide (NO) in mediating Cd toxicity, the origin of Cd-induced NO and its function in plant responses to Cd remain unknown. In this study, we examined NO synthesis and its role in Cd accumulation in P. notoginseng roots. Cd-induced NO production was significantly decreased by application of the nitrate reductase inhibitor tungstate but not the nitric oxide synthase inhibitor L-NAME (N(G)-methyl-l-arginine acetate), indicating that nitrate reductase is the major contributor to Cd-induced NO production in P. notoginseng roots. Under conditions of Cd stress, sodium nitroprusside (SNP, an NO donor) increased Cd accumulation in root cell walls but decreased Cd translocation to the shoot. In contrast, the NO scavenger cPTIO (2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) and tungstate both significantly decreased NO-increased Cd retention in root cell walls. The amounts of hemicellulose 1 and pectin, together with pectin methylesterase activity, were increased with the addition of SNP but were decreased by cPTIO and tungstate. Furthermore, increases or decreases in hemicellulose 1 and pectin contents as well as pectin methylesterase activity fit well with the increased or decreased retention of Cd in the cell walls of P. notoginseng roots. The results suggest that nitrate reductase-mediated NO production enhances Cd retention in P. notoginseng roots by modulating the properties of the cell wall.

  11. Effect of Root System Morphology on Root-sprouting and Shoot-rooting Abilities in 123 Plant Species from Eroded Lands in North-east Spain

    PubMed Central

    GUERRERO-CAMPO, JOAQUÍN; PALACIO, SARA; PÉREZ-RONTOMÉ, CARMEN; MONTSERRAT-MARTÍ, GABRIEL

    2006-01-01

    • Background and Aims The objective of this study was to test whether the mean values of several root morphological variables were related to the ability to develop root-borne shoots and/or shoot-borne roots in a wide range of vascular plants. • Methods A comparative study was carried out on the 123 most common plant species from eroded lands in north-east Spain. After careful excavations in the field, measurements were taken of the maximum root depth, absolute and relative basal root diameter, specific root length (SRL), and the root depth/root lateral spread ratio on at least three individuals per species. Shoot-rooting and root-sprouting were observed in a large number of individuals in many eroded and sedimentary environments. The effect of life history and phylogeny on shoot-rooting and root-sprouting abilities was also analysed. • Key Results The species with coarse and deep tap-roots tended to be root-sprouting and those with fine, fasciculate and long main roots (which generally spread laterally), tended to be shoot-rooting. Phylogeny had an important influence on root system morphology and shoot-rooting and root-sprouting capacities. However, the above relations stood after applying analyses based on phylogenetically independent contrasts (PICs). • Conclusions The main morphological features of the root system of the study species are related to their ability to sprout from their roots and form roots from their shoots. According to the results, such abilities might only be functionally viable in restricted root system morphologies and ecological strategies. PMID:16790468

  12. Trichoderma spp. Improve growth of Arabidopsis seedlings under salt stress through enhanced root development, osmolite production, and Na⁺ elimination through root exudates.

    PubMed

    Contreras-Cornejo, Hexon Angel; Macías-Rodríguez, Lourdes; Alfaro-Cuevas, Ruth; López-Bucio, José

    2014-06-01

    Salt stress is an important constraint to world agriculture. Here, we report on the potential of Trichoderma virens and T. atroviride to induce tolerance to salt in Arabidopsis seedlings. We first characterized the effect of several salt concentrations on shoot biomass production and root architecture of Arabidopsis seedlings. We found that salt repressed plant growth and root development in a dose-dependent manner by blocking auxin signaling. Analysis of the wild type and eir1, aux1-7, arf7arf19, and tir1abf2abf19 auxin-related mutants revealed a key role for indole-3-acetic acid (IAA) signaling in mediating salt tolerance. We also found that T. virens (Tv29.8) and T. atroviride (IMI 206040) promoted plant growth in both normal and saline conditions, which was related to the induction of lateral roots and root hairs through auxin signaling. Arabidopsis seedlings grown under saline conditions inoculated with Trichoderma spp. showed increased levels of abscissic acid, L-proline, and ascorbic acid, and enhanced elimination of Na⁺ through root exudates. Our data show the critical role of auxin signaling and root architecture to salt tolerance in Arabidopsis and suggest that these fungi may enhance the plant IAA level as well as the antioxidant and osmoprotective status of plants under salt stress.

  13. Root exudates drive interspecific facilitation by enhancing nodulation and N2 fixation

    PubMed Central

    Li, Bai; Li, Yu-Ying; Wu, Hua-Mao; Zhang, Fang-Fang; Li, Chun-Jie; Li, Xue-Xian; Lambers, Hans; Li, Long

    2016-01-01

    Plant diversity in experimental systems often enhances ecosystem productivity, but the mechanisms causing this overyielding are only partly understood. Intercropping faba beans (Vicia faba L.) and maize (Zea mays L.) result in overyielding and also, enhanced nodulation by faba beans. By using permeable and impermeable root barriers in a 2-y field experiment, we show that root–root interactions between faba bean and maize significantly increase both nodulation and symbiotic N2 fixation in intercropped faba bean. Furthermore, root exudates from maize promote faba bean nodulation, whereas root exudates from wheat and barley do not. Thus, a decline of soil nitrate concentrations caused by intercropped cereals is not the sole mechanism for maize promoting faba bean nodulation. Intercropped maize also caused a twofold increase in exudation of flavonoids (signaling compounds for rhizobia) in the systems. Roots of faba bean treated with maize root exudates exhibited an immediate 11-fold increase in the expression of chalcone–flavanone isomerase (involved in flavonoid synthesis) gene together with a significantly increased expression of genes mediating nodulation and auxin response. After 35 d, faba beans treated with maize root exudate continued to show up-regulation of key nodulation genes, such as early nodulin 93 (ENOD93), and promoted nitrogen fixation. Our results reveal a mechanism for how intercropped maize promotes nitrogen fixation of faba bean, where maize root exudates promote flavonoid synthesis in faba bean, increase nodulation, and stimulate nitrogen fixation after enhanced gene expression. These results indicate facilitative root–root interactions and provide a mechanism for a positive relationship between species diversity and ecosystem productivity. PMID:27217575

  14. Effect of nitrogen on root release of phytosiderophores and root uptake of Fe(III)-phytosiderophore in Fe-deficient wheat plants.

    PubMed

    Aciksoz, Seher Bahar; Ozturk, Levent; Gokmen, Ozay Ozgur; Römheld, Volker; Cakmak, Ismail

    2011-07-01

    Root release of phytosiderophores (PSs) is an important step in iron (Fe) acquisition of grasses, and this adaptive reaction of plants is affected by various plant and environmental factors. The objectives of this study were to study the effects of varied nitrogen (N) supply on (1) root and leaf concentrations of methionine, a precursor in the PS biosynthesis, (2) PS release from roots, (3) mobilization and uptake of Fe from (59) Fe-labeled Fe(III)-hydroxide [(59) Fe(OH)(3) ] and (4) root uptake of (59) Fe-labeled Fe(III)-deoxymugineic acid (DMA) by durum wheat (Triticum durum, cv. Balcali2000) plants grown in a nutrient solution. Enhanced N supply from 0.5 to 6 mM in a nutrient solution significantly increased the root release of PS under Fe deficiency. High N supply was also highly effective in increasing mobilization and root uptake of Fe from (59) Fe-hydroxide under low Fe supply. With adequate Fe, N nutrition did not affect mobilization and uptake of Fe from (59) Fe(OH)(3) . Root uptake and shoot translocation of Fe supplied as (59) Fe(III)-DMA were also stimulated by increasing N supply. Leaf concentration of methionine was reduced by low Fe supply, and this decline was pronounced in high N plants. The results show that the root release of PS, mobilization of Fe from (59) Fe(OH)(3) and root uptake and shoot translocation of Fe(III)-PS by durum wheat are markedly affected by N nutritional status of plants. These positive N effects may have important implications for Fe nutrition of human populations and should be considered in biofortification of food crops with Fe. Copyright © Physiologia Plantarum 2011.

  15. Aeration for plant root respiration in a tidal marsh

    NASA Astrophysics Data System (ADS)

    Li, Hailong; Li, Ling; Lockington, David

    2005-06-01

    This paper investigates the tidal effects on aeration conditions for plant root respiration in a tidal marsh. We extend the work of Ursino et al. (2004) by using a two-phase model for air and water flows in the marsh. Simulations have been conducted to examine directly the link between the airflow dynamics and the aeration condition in the marsh soil. The results show that the effects of entrapped air on water movement in the vadose zone are significant in certain circumstances. Single-phase models based on Richards' equation, which neglect such effects, may not be adequate for quantifying the aeration condition in tidal marsh. The optimal aeration condition, represented by the maximum of the integral magnitude of tidally advected air mass (TAAM) flux, is found to occur near the tidal creek for the four soil textures simulated. This may explain the observation that some salt marsh plant species grow better near tidal creeks than in the inner marsh areas. Our analyses, based on the two-phase model and predicted TAAM flux magnitude, provide further insight into the "positive feedback" mechanism proposed by Ursino et al. (2004). That is, pioneer plants may grow successfully near the creek where the root aeration condition is optimal. The roots of the pioneer plants can soften and loosen the rhizosphere soil, which increases the evapotranspiration rate, the soil porosity, and absolute permeability and weakens the capillary effects. These, in turn, improve further the root aeration conditions and may lead to colonization by plants less resistant to anaerobic conditions.

  16. Aeration for plant root respiration in a tidal marsh

    NASA Astrophysics Data System (ADS)

    Li, Hailong; Li, Ling; Lockington, David

    2005-06-01

    This paper investigates the tidal effects on aeration conditions for plant root respiration in a tidal marsh. We extend the work of Ursino et al. (2004) by using a two-phase model for air and water flows in the marsh. Simulations have been conducted to examine directly the link between the airflow dynamics and the aeration condition in the marsh soil. The results show that the effects of entrapped air on water movement in the vadose zone are significant in certain circumstances. Single-phase models based on Richards' equation, which neglect such effects, may not be adequate for quantifying the aeration condition in tidal marsh. The optimal aeration condition, represented by the maximum of the integral magnitude of tidally advected air mass (TAAM) flux, is found to occur near the tidal creek for the four soil textures simulated. This may explain the observation that some salt marsh plant species grow better near tidal creeks than in the inner marsh areas. Our analyses, based on the two-phase model and predicted TAAM flux magnitude, provide further insight into the ``positive feedback'' mechanism proposed by Ursino et al. (2004). That is, pioneer plants may grow successfully near the creek where the root aeration condition is optimal. The roots of the pioneer plants can soften and loosen the rhizosphere soil, which increases the evapotranspiration rate, the soil porosity, and absolute permeability and weakens the capillary effects. These, in turn, improve further the root aeration conditions and may lead to colonization by plants less resistant to anaerobic conditions.

  17. A Latex Metabolite Benefits Plant Fitness under Root Herbivore Attack

    PubMed Central

    Huber, Meret; Epping, Janina; Schulze Gronover, Christian; Fricke, Julia; Aziz, Zohra; Brillatz, Théo; Swyers, Michael; Köllner, Tobias G.; Vogel, Heiko; Hammerbacher, Almuth; Triebwasser-Freese, Daniella; Robert, Christelle A. M.; Verhoeven, Koen; Preite, Veronica; Gershenzon, Jonathan; Erb, Matthias

    2016-01-01

    Plants produce large amounts of secondary metabolites in their shoots and roots and store them in specialized secretory structures. Although secondary metabolites and their secretory structures are commonly assumed to have a defensive function, evidence that they benefit plant fitness under herbivore attack is scarce, especially below ground. Here, we tested whether latex secondary metabolites produced by the common dandelion (Taraxacum officinale agg.) decrease the performance of its major native insect root herbivore, the larvae of the common cockchafer (Melolontha melolontha), and benefit plant vegetative and reproductive fitness under M. melolontha attack. Across 17 T. officinale genotypes screened by gas and liquid chromatography, latex concentrations of the sesquiterpene lactone taraxinic acid β-D-glucopyranosyl ester (TA-G) were negatively associated with M. melolontha larval growth. Adding purified TA-G to artificial diet at ecologically relevant concentrations reduced larval feeding. Silencing the germacrene A synthase ToGAS1, an enzyme that was identified to catalyze the first committed step of TA-G biosynthesis, resulted in a 90% reduction of TA-G levels and a pronounced increase in M. melolontha feeding. Transgenic, TA-G-deficient lines were preferred by M. melolontha and suffered three times more root biomass reduction than control lines. In a common garden experiment involving over 2,000 T. officinale individuals belonging to 17 different genotypes, high TA-G concentrations were associated with the maintenance of high vegetative and reproductive fitness under M. melolontha attack. Taken together, our study demonstrates that a latex secondary metabolite benefits plants under herbivore attack, a result that provides a mechanistic framework for root herbivore driven natural selection and evolution of plant defenses below ground. PMID:26731567

  18. A Latex Metabolite Benefits Plant Fitness under Root Herbivore Attack.

    PubMed

    Huber, Meret; Epping, Janina; Schulze Gronover, Christian; Fricke, Julia; Aziz, Zohra; Brillatz, Théo; Swyers, Michael; Köllner, Tobias G; Vogel, Heiko; Hammerbacher, Almuth; Triebwasser-Freese, Daniella; Robert, Christelle A M; Verhoeven, Koen; Preite, Veronica; Gershenzon, Jonathan; Erb, Matthias

    2016-01-01

    Plants produce large amounts of secondary metabolites in their shoots and roots and store them in specialized secretory structures. Although secondary metabolites and their secretory structures are commonly assumed to have a defensive function, evidence that they benefit plant fitness under herbivore attack is scarce, especially below ground. Here, we tested whether latex secondary metabolites produced by the common dandelion (Taraxacum officinale agg.) decrease the performance of its major native insect root herbivore, the larvae of the common cockchafer (Melolontha melolontha), and benefit plant vegetative and reproductive fitness under M. melolontha attack. Across 17 T. officinale genotypes screened by gas and liquid chromatography, latex concentrations of the sesquiterpene lactone taraxinic acid β-D-glucopyranosyl ester (TA-G) were negatively associated with M. melolontha larval growth. Adding purified TA-G to artificial diet at ecologically relevant concentrations reduced larval feeding. Silencing the germacrene A synthase ToGAS1, an enzyme that was identified to catalyze the first committed step of TA-G biosynthesis, resulted in a 90% reduction of TA-G levels and a pronounced increase in M. melolontha feeding. Transgenic, TA-G-deficient lines were preferred by M. melolontha and suffered three times more root biomass reduction than control lines. In a common garden experiment involving over 2,000 T. officinale individuals belonging to 17 different genotypes, high TA-G concentrations were associated with the maintenance of high vegetative and reproductive fitness under M. melolontha attack. Taken together, our study demonstrates that a latex secondary metabolite benefits plants under herbivore attack, a result that provides a mechanistic framework for root herbivore driven natural selection and evolution of plant defenses below ground.

  19. Rooting depth and distributions of deep-rooted plants in the 200 Area control zone of the Hanford Site

    SciTech Connect

    Klepper, E.L.; Gano, K.A.; Cadwell, L.L.

    1985-01-01

    This study was conducted to document rooting depths and distributions of deep-rooted plants common to the Hanford Site 200-Area plateau. The effort concentrated on excavating plant species suspected of having deep root systems, and species that have been reported in previous studies to contain radionuclides in above ground parts. The information obtained in this study will be useful in modeling radionuclide transport by plants and in designing covers and barriers for decommissioning low-level radioactive waste burial sites. Fourteen species including 58 individual plants were excavated to measure maximum rooting depth and root density distribution (g dry root/dm/sup 3/) through the root zone. Age and canopy volumes of shrubs were also determined. Eight of the 14 species excavated had average rooting depths of 150 cm or more. The two deepest rooted plants were antelope bitterbrush and sagebrush with average depths of 296 and 200 cm, respectively. Gray rabbitbrush had an average rooting depth of 183 cm. Summer annuals, Russian thistle and bursage, had average rooting depths of 172 and 162 cm, respectively. 7 references, 4 figures, 5 tables.

  20. [Root architecture of two desert plants in central Hexi Corridor of Northwest China].

    PubMed

    Shan, Li-Shan; Li, Yi; Ren, Wei; Su, Shi-Ping; Dong, Qiu-Lian; Geng, Dong-Mei

    2013-01-01

    In this study, the root systems of desert plant species Reaumuria soongorica and Nitraria tangutorum in the central Hexi Corridor of Northwest China were excavated by shovel, and the characteristics of the plant root architecture were analyzed by using topology and fractal theory. The root topological indices of the two desert plants were small, and the root branching patterns were herringbone-like. The roots of the two desert plants had obvious fractal characteristics, with the fractal dimension of R. soongorica and N. tangutorum being (1.18 +/- 0.04) and (1.36 +/- 0.06), respectively. The root fractal dimension and fractal abundance were significantly positively correlated with the root average link length. The root average link lengths of the two plants were long, which enlarged the plants' effective nutrition space, and thus, made the plants adapt to the dry and infertile soil environment. The sums of the root cross-sectional areas before and after the root bifurcation of the two desert plants were equal, which verified the principle of Leonardo da Vinci. A total of 17 parameters of root architecture were analyzed by the principal component analysis. The parameters of root topological structure, numbers of root links, stepwise branching ratio, and root diameter could well present the root architecture characteristics of the two desert plants.

  1. Overexpression of cinnamate 4-hydroxylase gene enhances biosynthesis of decursinol angelate in Angelica gigas hairy roots.

    PubMed

    Park, Nam Il; Park, Jee Hee; Park, Sang Un

    2012-02-01

    Angelica gigas is a medicinal plant that produces pyranocoumarins, including decursin (D) and decursinol angelate (DA), which have neuroprotective, anticancer, and antiandrogenic effects. In this study, the coumarin biosynthetic pathway was engineered to increase the production of DA. Specifically, a vector was constructed which contained the A. gigas phenylalanine ammonia-lyase (AgPAL) and cinnamate 4-hydroxylase (AgC4H) genes that were driven by the cauliflower mosaic virus (CaMV) 35S promoter. Transgenic hairy roots that overexpressed AgPAL or AgC4H genes were obtained by using an Agrobacterium rhizogenes-mediated transformation system. Among them, only AgC4H-transgenic hairy root lines produced more DA than control transgenic hairy root lines. The enhanced gene expression corresponded to elevated C4H activities. This study showed the importance of C4H in the production of DA in A. gigas hairy root culture.

  2. Root profile in Multi-layered Dehesas: an approach to plant-to-plant Interaction

    NASA Astrophysics Data System (ADS)

    Rolo, V.; Moreno, G.

    2009-04-01

    Assessing plant-to-plant relationship is a key issue in agroforestry systems. Due to the sessile feature of plants most of these interactions take place within a restricted space, so characterizing the zone where the plant alters its environment is important to find overlapping areas where the facilitation or competition could occur. Main part of plan-to-plant interactions in the dehesa are located at belowground level, thus the main limited resources in Mediterranean ecosystems are soil nutrient and water. Hence a better knowledge of rooting plant profile can be useful to understand the functioning of the dehesa. The Iberian dehesa has always been considered as a silvopastoral system where, at least, two strata of vegetation coexist: native grasses and trees. However the dehesa is also a diverse system where cropland and encroached territories have been systematically combined, more or less periodically, with native pasture in order to obtain agricultural, pastoral and forestry outputs. These multipurpose mosaic-type systems generate several scenarios where the plant influence zone may be overlapped and the interaction, competition or facilitation, between plants can play an important role in the ecosystem functioning in terms of productivity and stability. In the present study our aim was to characterize the rooting profile of multi-layered dehesas in order to understand the competitive, and/or facilitative, relationships within the different plant strata. The root profile of Quercus ilex subsp. ballota, Cistus ladanifer, Retama spaherocarpa and natural grasses was studied. So 48 trenches, up to 2 meters deep, were excavated in 4 different environments: (i) grass; (ii) tree-grass; (iii) tree-shrub and (iv) tree-shrub-grass (12 trenches in each environment). The study was carried out in 4 dehesas, 2 encroached with C. ladanifer and 2 with R. spaherocarpa. In every trench soil samples were taken each 20 cm. Subsequently, all samples were sieved using different mesh

  3. Plant iodine-131 uptake in relation to root concentration as measured in minirhizotron by video camera:

    SciTech Connect

    Moss, K.J.

    1990-09-01

    Glass viewing tubes (minirhizotrons) were placed in the soil beneath native perennial bunchgrass (Agropyron spicatum). The tubes provided access for observing and quantifying plant roots with a miniature video camera and soil moisture estimates by neutron hydroprobe. The radiotracer I-131 was delivered to the root zone at three depths with differing root concentrations. The plant was subsequently sampled and analyzed for I-131. Plant uptake was greater when I-131 was applied at soil depths with higher root concentrations. When I-131 was applied at soil depths with lower root concentrations, plant uptake was less. However, the relationship between root concentration and plant uptake was not a direct one. When I-131 was delivered to deeper soil depths with low root concentrations, the quantity of roots there appeared to be less effective in uptake than the same quantity of roots at shallow soil depths with high root concentration. 29 refs., 6 figs., 11 tabs.

  4. The Root Herbivore History of the Soil Affects the Productivity of a Grassland Plant Community and Determines Plant Response to New Root Herbivore Attack

    PubMed Central

    Sonnemann, Ilja; Hempel, Stefan; Beutel, Maria; Hanauer, Nicola; Reidinger, Stefan; Wurst, Susanne

    2013-01-01

    Insect root herbivores can alter plant community structure by affecting the competitive ability of single plants. However, their effects can be modified by the soil environment. Root herbivory itself may induce changes in the soil biota community, and it has recently been shown that these changes can affect plant growth in a subsequent season or plant generation. However, so far it is not known whether these root herbivore history effects (i) are detectable at the plant community level and/or (ii) also determine plant species and plant community responses to new root herbivore attack. The present greenhouse study determined root herbivore history effects of click beetle larvae (Elateridae, Coleoptera, genus Agriotes) in a model grassland plant community consisting of six common species (Achillea millefolium, Plantago lanceolata, Taraxacum officinale, Holcus lanatus, Poa pratensis, Trifolium repens). Root herbivore history effects were generated in a first phase of the experiment by growing the plant community in soil with or without Agriotes larvae, and investigated in a second phase by growing it again in the soils that were either Agriotes trained or not. The root herbivore history of the soil affected plant community productivity (but not composition), with communities growing in root herbivore trained soil producing more biomass than those growing in untrained soil. Additionally, it influenced the response of certain plant species to new root herbivore attack. Effects may partly be explained by herbivore-induced shifts in the community of arbuscular mycorrhizal fungi. The root herbivore history of the soil proved to be a stronger driver of plant growth on the community level than an actual root herbivore attack which did not affect plant community parameters. History effects have to be taken into account when predicting the impact of root herbivores on grasslands. PMID:23441201

  5. The root herbivore history of the soil affects the productivity of a grassland plant community and determines plant response to new root herbivore attack.

    PubMed

    Sonnemann, Ilja; Hempel, Stefan; Beutel, Maria; Hanauer, Nicola; Reidinger, Stefan; Wurst, Susanne

    2013-01-01

    Insect root herbivores can alter plant community structure by affecting the competitive ability of single plants. However, their effects can be modified by the soil environment. Root herbivory itself may induce changes in the soil biota community, and it has recently been shown that these changes can affect plant growth in a subsequent season or plant generation. However, so far it is not known whether these root herbivore history effects (i) are detectable at the plant community level and/or (ii) also determine plant species and plant community responses to new root herbivore attack. The present greenhouse study determined root herbivore history effects of click beetle larvae (Elateridae, Coleoptera, genus Agriotes) in a model grassland plant community consisting of six common species (Achillea millefolium, Plantago lanceolata, Taraxacum officinale, Holcus lanatus, Poa pratensis, Trifolium repens). Root herbivore history effects were generated in a first phase of the experiment by growing the plant community in soil with or without Agriotes larvae, and investigated in a second phase by growing it again in the soils that were either Agriotes trained or not. The root herbivore history of the soil affected plant community productivity (but not composition), with communities growing in root herbivore trained soil producing more biomass than those growing in untrained soil. Additionally, it influenced the response of certain plant species to new root herbivore attack. Effects may partly be explained by herbivore-induced shifts in the community of arbuscular mycorrhizal fungi. The root herbivore history of the soil proved to be a stronger driver of plant growth on the community level than an actual root herbivore attack which did not affect plant community parameters. History effects have to be taken into account when predicting the impact of root herbivores on grasslands.

  6. Perception of neighboring plants by rhizomes and roots: morphological manifestations of a clonal plant

    USGS Publications Warehouse

    Huber-Sannwald, Elisabeth; Pyke, David A.; Caldwell, M.M.

    1997-01-01

    A previous study showed that clonal morphology of the rhizomatous grass Elymus lanceolatus ssp. lanceolatus (Scibner & J.G. Smith Gould) was influenced more by neighbouring root systems than by the local distribution of nutrients. In this study we determine whether individual rhizomes or roots of E. lanceolatus perceive neighbouring root systems and how this is manifested in morphological responses of E. lanceolatus clones. Elymus lanceolatus was grown in the same bin with Pseudoroegneria spicata (Pursh) A. Love or Agropyron desertorum (Fisch. ex Link) Schult. plants. Elymus lanceolatus was separated from its neighbours by different barriers. The barriers allowed either only E. lanceolatus roots; only a single E. lanceolatus primary rhizome; or both roots and rhizomes to contact the neighbour root system. When only a single E. lanceolatus primary rhizome with potentially developing branching rhizomes made contact with the neighbour, the clonal structure of E. lanceolatus was modified more with P. spicata as the neighbour than with A. desertorum. With root contact of E. lanceolatus alone there was a similar effect with the neighbouring plants, but there was a more marked inhibitory effect on E. lanceolatus clonal growth with P. spicata than with A. desertorum, compared with the treatment with only a single rhizome in contact with the neighbour. Root resource competition in the unconstrained treatment (roots and rhizomes) between neighbouring plant and E. lanceolatus was more apparent with A. desertorum than with P. spicata. This study is one of the first to document that rhizome and root contact of a clonal plant with its neighbours may induce different clonal responses depending on the species of neighbour.

  7. Use of sediment CO2 by submersed rooted plants

    PubMed Central

    Winkel, Anders; Borum, Jens

    2009-01-01

    Background and Aims Submersed plants have different strategies to overcome inorganic carbon limitation. It is generally assumed that only small rosette species (isoetids) are able to utilize the high sediment CO2 availability. The present study examined to what extent five species of submersed freshwater plants with different morphology and growth characteristics (Lobelia dortmanna, Lilaeopsis macloviana, Ludwigia repens, Vallisneria americana and Hydrocotyle verticillata) are able to support photosynthesis supplied by uptake of CO2 from the sediment. Methods Gross photosynthesis was measured in two-compartment split chambers with low inorganic carbon availability in leaf compartments and variable CO2 availability (0 to >8 mmol L−1) in root compartments. Photosynthetic rates based on root-supplied CO2 were compared with maximum rates obtained at saturating leaf CO2 availability, and 14C experiments were conducted for two species to localize bottlenecks for utilization of sediment CO2. Key Results All species except Hydrocotyle were able to use sediment CO2, however, with variable efficiency, and with the isoetid, Lobelia, as clearly the most effective and the elodeid, Ludwigia, as the least efficient. At a water column CO2 concentration in equilibrium with air, Lobelia, Lilaeopsis and Vallisneria covered >75% of their CO2 requirements by sediment uptake, and sediment CO2 contributed substantially to photosynthesis at water CO2 concentrations up to 1000 µmol L−1. For all species except Ludwigia, the shoot to root ratio on an areal basis was the single factor best explaining variability in the importance of sediment CO2. For Ludwigia, diffusion barriers limited uptake or transport from roots to stems and transport from stems to leaves. Conclusions Submersed plants other than isoetids can utilize sediment CO2, and small and medium sized elodeids with high root to shoot area in particular may benefit substantially from uptake of sediment CO2 in low alkaline lakes

  8. Predicting fine root lifespan from plant functional traits in temperate trees.

    PubMed

    Luke McCormack, M; Adams, Thomas S; Smithwick, Erica A H; Eissenstat, David M

    2012-09-01

    Although linkages of leaf and whole-plant traits to leaf lifespan have been rigorously investigated, there is a limited understanding of similar linkages of whole-plant and fine root traits to root lifespan. In comparisons across species, do suites of traits found in leaves also exist for roots, and can these traits be used to predict root lifespan? We observed the fine root lifespan of 12 temperate tree species using minirhizotrons in a common garden and compared their median lifespans with fine-root and whole-plant traits. We then determined which set of combined traits would be most useful in predicting patterns of root lifespan. Median root lifespan ranged widely among species (95-336 d). Root diameter, calcium content, and tree wood density were positively related to root lifespan, whereas specific root length, nitrogen (N) : carbon (C) ratio, and plant growth rate were negatively related to root lifespan. Root diameter and plant growth rate, together (R² = 0.62) or in combination with root N : C ratio (R² = 0.76), were useful predictors of root lifespan across the 12 species. Our results highlight linkages between fine root lifespan in temperate trees and plant functional traits that may reduce uncertainty in predictions of root lifespan or turnover across species at broader spatial scales. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

  9. Enhanced Mineral Uptake by Zea mays and Sorghum bicolor Roots Inoculated with Azospirillum brasilense†

    PubMed Central

    Lin, Willy; Okon, Yaacov; Hardy, Ralph W. F.

    1983-01-01

    Inoculation of corn (Zea mays) seeds with Azospirillum brasilense strain Cd or Sp 7 significantly enhanced (30 to 50% over controls) the uptake of NO3−, K+, and H2PO4− into 3- to 4-day- and 2-week-old root segments. No gross changes in root morphology were observed; altered cell arrangement in the outer four or five layers of the cortex was seen in photomicrographs of cross sections of inoculated corn roots. The surface activity involved in ion uptake probably increased, as shown by the darker staining by methylene blue of the affected area. Shoot dry weight increased 20 to 30% in inoculated plants after 3 weeks, presumably by enhancement of mineral uptake. Corn and sorghum plants grown to maturity on limiting nutrients in the greenhouse showed improved growth from inoculation approaching that of plants grown on normal nutrient concentrations. Enhanced ion uptake may be a significant factor in the crop yield enhancement reported for Azospirillum inoculation. PMID:16346311

  10. Auxin modulates the enhanced development of root hairs in Arabidopsis thaliana (L.) Heynh. under elevated CO(2).

    PubMed

    Niu, Yaofang; Jin, Chongwei; Jin, Gulei; Zhou, Qingyan; Lin, Xianyong; Tang, Caixian; Zhang, Yongsong

    2011-08-01

    Root hairs may play a critical role in nutrient acquisition of plants grown under elevated CO(2) . This study investigated how elevated CO(2) enhanced the development of root hairs in Arabidopsis thaliana (L.) Heynh. The plants under elevated CO(2) (800 µL L(-1)) had denser and longer root hairs, and more H-positioned cells in root epidermis than those under ambient CO(2) (350 µL L(-1)). The elevated CO(2) increased auxin production in roots. Under elevated CO(2) , application of either 1-naphthoxyacetic acid (1-NOA) or N-1-naphthylphthalamic acid (NPA) blocked the enhanced development of root hairs. The opposite was true when the plants under ambient CO(2) were treated with 1-naphthylacetic acid (NAA), an auxin analogue. Furthermore, the elevated CO(2) did not enhance the development of root hairs in auxin-response mutants, axr1-3, and auxin-transporter mutants, axr4-1, aux1-7 and pin1-1. Both elevated CO(2) and NAA application increased expressions of caprice, triptychon and rho-related protein from plants 2, and decreased expressions of werewolf, GLABRA2, GLABRA3 and the transparent testa glabra 1, genes related to root-hair development, while 1-NOA and NPA application had an opposite effect. Our study suggests that elevated CO(2) enhanced the development of root hairs in Arabidopsis via the well-characterized auxin signalling and transport that modulate the initiation of root hairs and the expression of its specific genes.

  11. Interaction of sulfur and nitrogen nutrition in tobacco (Nicotiana tabacum) plants: significance of nitrogen source and root nitrate reductase.

    PubMed

    Kruse, J; Kopriva, S; Hänsch, R; Krauss, G-J; Mendel, R-R; Rennenberg, H

    2007-09-01

    The significance of root nitrate reductase for sulfur assimilation was studied in tobacco (NICOTIANA TABACUM) plants. For this purpose, uptake, assimilation, and long-distance transport of sulfur were compared between wild-type tobacco and transformants lacking root nitrate reductase, cultivated either with nitrate or with ammonium nitrate. A recently developed empirical model of plant internal nitrogen cycling was adapted to sulfur and applied to characterise whole plant sulfur relations in wild-type tobacco and the transformant. Both transformation and nitrogen nutrition strongly affected sulfur pools and sulfur fluxes. Transformation decreased the rate of sulfate uptake in nitrate-grown plants and root sulfate and total sulfur contents in root biomass, irrespective of N nutrition. Nevertheless, glutathione levels were enhanced in the roots of transformed plants. This may be a consequence of enhanced APR activity in the leaves that also resulted in enhanced organic sulfur content in the leaves of the tranformants. The lack of nitrate reductase in the roots in the transformants caused regulatory changes in sulfur metabolism that resembled those observed under nitrogen deficiency. Nitrate nutrition reduced total sulfur content and all the major fractions analysed in the leaves, but not in the roots, compared to ammonium nitrate supply. The enhanced organic sulfur and glutathione levels in ammonium nitrate-fed plants corresponded well to elevated APR activity. But foliar sulfate contents also increased due to decreased re-allocation of sulfate into the phloem of ammonium nitrate-fed plants. Further studies will elucidate whether this decrease is achieved by downregulation of a specific sulfate transporter in vascular tissues.

  12. Change of soil organic matter quality and quantity by deep-rooting plants - a molecular approach

    NASA Astrophysics Data System (ADS)

    Gocke, Martina; Derenne, Sylvie; Anquetil, Christelle; Huguet, Arnaud; Dignac, Marie-France; Rumpel, Cornelia; Wiesenberg, Guido L. B.

    2015-04-01

    Under predicted rising atmospheric CO2 concentration, soils are discussed to potentially act as C sinks. Stability and long-term storage of soil OM are affected by both molecular structure of incorporated organic remains and environmental factors. It is increasingly accepted that roots contribute to significant portions of topsoil OM, whereas their role for C cycling is less known for depths >> 1 m, i.e. the deep subsoil and underlying soil parent material like terrestrial sediments. To trace root-related features and organic remains, transects were sampled from ancient (3-10 ky) and recent calcified roots (rhizoliths) via surrounding sediment towards sediment free of visible root remains, at two sites. At the Nussloch loess-paleosol sequence (SW Germany), transects were collected as intact cores and scanned by X-ray microtomography for visualization of rhizoliths and rhizosphere. Afterwards, cores were cut into concentric slices and, similar to rhizolith and sediment samples from the sandy deep subsoil at Sopron (NW Hungary), analyzed for suberin molecular markers. Suberin biomarkers were found in both recent and ancient root systems, demonstrating their suitability to identify root-derived OM in terrestrial sediments with ages of several tens of ky. Varying relative portions of the respective suberin markers enabled the attribution of Sopron rhizoliths to oak origin, and assessment of the rhizosphere, which extended up to several cm. This confirms recent studies which demonstrated the possible postsedimentary incorporation of considerable amounts of root and rhizomicrobial remains in loess, based on biomarkers deriving either from plants and microorganisms (alkanes, fatty acids) or solely from microorganisms (GDGTs). 3D scanning of Nussloch rhizoliths and surrounding loess showed large channels of former root growth, whereas the root tissue was commonly degraded. Additionally, microtomography enabled assessment of abundant fine calcified roots as well as biopores

  13. Root traits contributing to plant productivity under drought

    USDA-ARS?s Scientific Manuscript database

    ROOT TRAITS CONTRIBUTING TO PLANT PRODUCTIVITY UNDER DROUGHT L.H. Comas1, S.R. Becker2, V.M.V. Cruz3,4, P.F. Byrne2, D.A. Dierig3 1USDA-ARS, Water Management Research Unit, Fort Collins, CO, USA 2Colorado State University, Soil and Crop Sciences, Fort Collins, CO, USA 3USDA-ARS, National Center fo...

  14. Hydraulic lift: consequences of water efflux from the roots of plants.

    PubMed

    Caldwell, Martyn M; Dawson, Todd E; Richards, James H

    1998-01-01

    Hydraulic lift is the passive movement of water from roots into soil layers with lower water potential, while other parts of the root system in moister soil layers, usually at depth, are absorbing water. Here, we review the brief history of laboratory and field evidence supporting this phenomenon and discuss some of the consequences of this below-ground behavior for the ecology of plants. Hydraulic lift has been shown in a relatively small number of species (27 species of herbs, grasses, shrubs, and trees), but there is no fundamental reason why it should not be more common as long as active root systems are spanning a gradient in soil water potential (Ψs) and that the resistance to water loss from roots is low. While the majority of documented cases of hydraulic lift in the field are for semiarid and arid land species inhabiting desert and steppe environments, recent studies indicate that hydraulic lift is not restricted to these species or regions. Large quantities of water, amounting to an appreciable fraction of daily transpiration, are lifted at night. This temporary partial rehydration of upper soil layers provides a source of water, along with soil moisture deeper in the profile, for transpiration the following day and, under conditions of high atmospheric demand, can substantially facilitate water movement through the soil-plant-atmosphere system. Release of water into the upper soil layers has been shown to afford the opportunity for neighboring plants to utilize this source of water. Also, because soils tend to dry from the surface downward and nutrients are usually most plentiful in the upper soil layers, lifted water may provide moisture that facilitates favorable biogeochemical conditions for enhancing mineral nutrient availability, microbial processes, and the acquisition of nutrients by roots. Hydraulic lift may also prolong or enhance fine-root activity by keeping them hydrated. Such indirect benefits of hydraulic lift may have been the primary

  15. Do Sebacinales commonly associate with plant roots as endophytes?

    PubMed

    Selosse, Marc-André; Dubois, Marie-Pierre; Alvarez, Nadir

    2009-10-01

    Sebacinales are basal Hymenomycetes with diverse mycorrhizal abilities, ranging from ectomycorrhizae to ericoid and orchid mycorrhizae. Several previous PCR or isolation works raised the possibility that Sebacinales are endophytes in plant roots. We tested this hypothesis in an isolation-independent approach by using specific PCR primers for ribosomal DNA of Sebacinales on AM mycorrhizal or non-mycorrhizal roots. Thirty-nine plant species were sampled on a Caribbean and two European sites (3 repetition per species and site), covering 25 families in monocots and eudicots. PCR signals were obtained from 40 samples (28.9%) from 27 species (69.2%) and all sites. Whenever sequencing was successful, a sequence belonging to Sebacinales was recovered. A phylogenetic approach revealed that 13 of them belonged to clade B (encompassing ericoid and orchid mycorrhizal species) and 4 to clade A (usually encompassing only ectomycorrhizal species). These data suggest that Sebacinales may be endophytic in many angiosperm roots, and that this condition is plesiomorphic in Sebacinales. They bridge the gap between physiological studies, inoculating Sebacinales (Piriformospora indica or Sebacina vermifera) on diverse plants and molecular ecology, hitherto restricting Sebacinales to mycorrhizal interactions. Structural and functional aspects of the interaction deserve further studies.

  16. Establishment of Azotobacter on plant roots: chemotactic response, development and analysis of root exudates of cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.).

    PubMed

    Kumar, Rakesh; Bhatia, Ranjana; Kukreja, K; Behl, Rishi Kumar; Dudeja, Surjit Singh; Narula, Neeru

    2007-10-01

    Biofertilizers contribute in N(2) fixation, P solubilization, phytohormone production and thus enhance plant growth. Beneficial plant-microbe interactions and the stability and effectiveness of biofertilizer depend upon the establishment of bacterial strains in the rhizosphere of the plant. This interaction depends upon many factors, one of them being plant exudates. Root exudates are composed of small organic molecules like carbonic acids, amino acids or sugars etc., which are released into the soil and bacteria can be attracted towards these exudates due to chemotaxis. The chemotactic behaviour of Azotobacter strains was studied using cotton (Desi HD 123 and American H 1098) and wheat (WH 711) seedlings and the root exudates of these two plants were chemically characterized. Analysis of the root exudates revealed the presence of sugars and simple polysaccharides (glucose), amino acids (glutamate, lysine) and organic acids (citric acid, succinic acid, maleic acid, malonic acid). Differences between cotton cultivars in root exudates were observed which influenced chemotactic response in Azotobacter. These results indicate colonization with rhizobacteria which implies that optimal symbionts, on the sides of both plant cultivar and bioinoculant bacteria can lead to better plant growth under cultivation conditions.

  17. Root-synthesized cytokinins improve shoot growth and fruit yield in salinized tomato (Solanum lycopersicum L.) plants.

    PubMed

    Ghanem, Michel Edmond; Albacete, Alfonso; Smigocki, Ann C; Frébort, Ivo; Pospísilová, Hana; Martínez-Andújar, Cristina; Acosta, Manuel; Sánchez-Bravo, José; Lutts, Stanley; Dodd, Ian C; Pérez-Alfocea, Francisco

    2011-01-01

    Salinity limits crop productivity, in part by decreasing shoot concentrations of the growth-promoting and senescence-delaying hormones cytokinins. Since constitutive cytokinin overproduction may have pleiotropic effects on plant development, two approaches assessed whether specific root-localized transgenic IPT (a key enzyme for cytokinin biosynthesis) gene expression could substantially improve tomato plant growth and yield under salinity: transient root IPT induction (HSP70::IPT) and grafting wild-type (WT) shoots onto a constitutive IPT-expressing rootstock (WT/35S::IPT). Transient root IPT induction increased root, xylem sap, and leaf bioactive cytokinin concentrations 2- to 3-fold without shoot IPT gene expression. Although IPT induction reduced root biomass (by 15%) in control (non-salinized) plants, in salinized plants (100 mM NaCl for 22 d), increased cytokinin concentrations delayed stomatal closure and leaf senescence and almost doubled shoot growth (compared with WT plants), with concomitant increases in the essential nutrient K(+) (20%) and decreases in the toxic ion Na(+) (by 30%) and abscisic acid (by 20-40%) concentrations in transpiring mature leaves. Similarly, WT/35S::IPT plants (scion/rootstock) grown with 75 mM NaCl for 90 d had higher fruit trans-zeatin concentrations (1.5- to 2-fold) and yielded 30% more than WT/non-transformed plants. Enhancing root cytokinin synthesis modified both shoot hormonal and ionic status, thus ameliorating salinity-induced decreases in growth and yield.

  18. Plant growth regulators enhance gold uptake in Brassica juncea.

    PubMed

    Kulkarni, Manoj G; Stirk, Wendy A; Southway, Colin; Papenfus, Heino B; Swart, Pierre A; Lux, Alexander; Vaculík, Marek; Martinka, Michal; Van Staden, Johannes

    2013-01-01

    The use of plant growth regulators is well established and they are used in many fields of plant science for enhancing growth. Brassica juncea plants were treated with 2.5, 5.0 and 7.5 microM auxin indole-3-butyric acid (IBA), which promotes rooting. The IBA-treated plants were also sprayed with 100 microM gibberellic acid (GA3) and kinetin (Kin) to increase leaf-foliage. Gold (I) chloride (AuCl) was added to the growth medium of plants to achieve required gold concentration. The solubilizing agent ammonium thiocyanate (1 g kg(-1)) (commonly used in mining industries to solubilize gold) was added to the nutrient solution after six weeks of growth and, two weeks later, plants were harvested. Plant growth regulators improved shoot and root dry biomass of B. juncea plants. Inductively Coupled Plasma Optical Emission Spectrometry analysis showed the highest Au uptake for plants treated with 5.0 microM IBA. The average recovery of Au with this treatment was significantly greater than the control treatment by 45.8 mg kg(-1) (155.7%). The other IBA concentrations (2.5 and 7.5 microM) also showed a significant increase in Au uptake compared to the control plants by 14.7 mg kg(-1) (50%) and 42.5 mg kg(-1) (144.5%) respectively. A similar trend of Au accumulation was recorded in the roots of B. juncea plants. This study conducted in solution culture suggests that plant growth regulators can play a significant role in improving phytoextraction of Au.

  19. Composite potato plants with transgenic roots on non-transgenic shoots: a model system for studying gene silencing in roots.

    PubMed

    Horn, Patricia; Santala, Johanna; Nielsen, Steen Lykke; Hühns, Maja; Broer, Inge; Valkonen, Jari P T

    2014-12-01

    Composite potato plants offer an extremely fast, effective and reliable system for studies on gene functions in roots using antisense or inverted-repeat but not sense constructs for gene inactivation. Composite plants, with transgenic roots on a non-transgenic shoot, can be obtained by shoot explant transformation with Agrobacterium rhizogenes. The aim of this study was to generate composite potato plants (Solanum tuberosum) to be used as a model system in future studies on root-pathogen interactions and gene silencing in the roots. The proportion of transgenic roots among the roots induced was high (80-100%) in the four potato cultivars tested (Albatros, Desirée, Sabina and Saturna). No wild-type adventitious roots were formed at mock inoculation site. All strains of A. rhizogenes tested induced phenotypically normal roots which, however, showed a reduced response to cytokinin as compared with non-transgenic roots. Nevertheless, both types of roots were infected to a similar high rate with the zoospores of Spongospora subterranea, a soilborne potato pathogen. The transgenic roots of composite potato plants expressed significantly higher amounts of β-glucuronidase (GUS) than the roots of a GUS-transgenic potato line event. Silencing of the uidA transgene (GUS) was tested by inducing roots on the GUS-transgenic cv. Albatros event with strains of A. rhizogenes over-expressing either the uidA sense or antisense transcripts, or inverted-repeat or hairpin uidA RNA. The three last mentioned constructs caused 2.5-4.0 fold reduction in the uidA mRNA expression. In contrast, over-expression of uidA resulted in over 3-fold increase in the uidA mRNA and GUS expression, indicating that sense-mediated silencing (co-suppression) was not functional in roots. The results suggest that composite plants offer a useful experimental system for potato research, which has gained little previous attention.

  20. Influence of arbuscular mycorrhizae on the root system of maize plants under salt stress.

    PubMed

    Sheng, Min; Tang, Ming; Chen, Hui; Yang, Baowei; Zhang, Fengfeng; Huang, Yanhui

    2009-07-01

    Salt stress has become a severe global problem, and salinity is one of the most important abiotic factors limiting plant growth and yield. It is known that arbuscular mycorrhizal (AM) fungi decrease plant yield losses under salinity. With the aim of determining whether AM inoculation would give an advantage to root development under salt stress, a greenhouse experiment was carried out with AM or without AM fungi. Maize plants were grown in a sand and soil mixture with 5 NaCl levels (0, 0.5, 1.0, 1.5, and 2.0 g/kg dry substrate) for 55 days, following 15 days of nonsaline pretreatment. At all salt levels, mycorrhizal plants had higher dry shoot and root mass, higher root activity, and lower root to shoot ratios than non-mycorrhizal plants. In salt-free soil, root length, root surface area, root volume, and number of root tips and forks were significantly larger in mycorrhizal plants than in non-mycorrhizal plants, whereas, under salt stress, average root diameter and root volume of mycorrhizal plants were larger than those of non-mycorrhizal plants. Regardless of the NaCl level, mycorrhizal plants had lower specific root length, lower percentage of root length in the 0-0.2 mm diameter class, and higher percentage of root length in both the 0.2-0.4 mm and 0.4-0.6 mm diameter classes, which suggests that the root system shows a significant shift towards a thicker root system when maize plants were inoculated with Glomus mosseae (Nicolson & Gerdemann). The results presented here indicate that the improvements in root activity and the coarse root system of mycorrhizal maize may help in alleviating salt stress on the plant.

  1. Tall fescue cultivar and fungal endophyte combinations influence plant growth and root exudate composition

    PubMed Central

    Guo, Jingqi; McCulley, Rebecca L.; McNear, David H.

    2015-01-01

    Tall fescue [Lolium arundinaceum (Schreb.)] is a cool-season perennial grass used in pastures throughout the Southeastern United States. The grass can harbor a shoot-specific fungal endophyte (Epichloë coenophiala) thought to provide the plant with enhanced resistance to biotic and abiotic stresses. Because alkaloids produced by the common variety of the endophyte cause severe animal health issues, focus has been on replacing the common-toxic strain with novel varieties that do not produce the mammal-toxic alkaloids but maintain abiotic and biotic stress tolerance benefits. Little attention has been given to the influence of the plant-fungal symbiosis on rhizosphere processes. Therefore, our objective was to study the influence of this relationship on plant biomass production and root exudate composition in tall fescue cultivars PDF and 97TF1, which were either not infected with the endophyte (E-), infected with the common toxic endophyte (CTE+) strain or with one of two novel endophytes (AR542E+, AR584E+). Plants were grown sterile for 3 weeks after which plant biomass, total organic carbon, total phenolic content and detailed chemical composition of root exudates were determined. Plant biomass production and exudate phenolic and organic carbon content were influenced by endophyte status, tall fescue cultivar, and their interaction. GC-TOF MS identified 132 compounds, including lipids, carbohydrates and carboxylic acids. Cluster analysis showed that the interaction between endophyte and cultivar resulted in unique exudate profiles. This is the first detailed study to assess how endophyte infection, notably with novel endophytes, and tall fescue cultivar interact to influence root exudate composition. Our results illustrate that tall fescue cultivar and endophyte status can influence plant growth and root exudate composition, which may help explain the observed influence of this symbiosis on rhizosphere biogeochemical processes. PMID:25914697

  2. Root morphological and proteomic responses to growth restriction in maize plants supplied with sufficient N.

    PubMed

    Yan, Huifeng; Li, Ke; Ding, Hong; Liao, Chengsong; Li, Xuexian; Yuan, Lixing; Li, Chunjian

    2011-07-01

    The primary objective of this study was to better understand how root morphological alteration stimulates N uptake in maize plants after root growth restriction, by investigating the changes in length and number of lateral roots, (15)NO(3)(-) influx, the expression level of the low-affinity Nitrate transporter ZmNrt1.1, and proteomic composition of primary roots. Maize seedlings were hydroponically cultured with three different types of root systems: an intact root system, embryonic roots only, or primary roots only. In spite of sufficient N supply, root growth restriction stimulated compensatory growth of remaining roots, as indicated by the increased lateral root number and root density. On the other hand, there was no significant difference in (15)NO(3)(-) influx between control and primary root plants; neither in ZmNrt1.1 expression levels in primary roots of different treatments. Our data suggested that increased N uptake by maize seedlings experiencing root growth restriction is attributed to root morphological adaptation, rather than explained by the variation in N uptake activity. Eight proteins were differentially accumulated in embryonic and primary root plants compared to control plants. These differentially accumulated proteins were closely related to signal transduction and increased root growth.

  3. Transgenic plants for enhanced biodegradation and phytoremediation of organic xenobiotics.

    PubMed

    Abhilash, P C; Jamil, Sarah; Singh, Nandita

    2009-01-01

    Phytoremediation--the use of plants to clean up polluted soil and water resources--has received much attention in the last few years. Although plants have the inherent ability to detoxify xenobiotics, they generally lack the catabolic pathway for the complete degradation of these compounds compared to microorganisms. There are also concerns over the potential for the introduction of contaminants into the food chain. The question of how to dispose of plants that accumulate xenobiotics is also a serious concern. Hence the feasibility of phytoremediation as an approach to remediate environmental contamination is still somewhat in question. For these reasons, researchers have endeavored to engineer plants with genes that can bestow superior degradation abilities. A direct method for enhancing the efficacy of phytoremediation is to overexpress in plants the genes involved in metabolism, uptake, or transport of specific pollutants. Furthermore, the expression of suitable genes in root system enhances the rhizodegradation of highly recalcitrant compounds like PAHs, PCBs etc. Hence, the idea to amplify plant biodegradation of xenobiotics by genetic manipulation was developed, following a strategy similar to that used to develop transgenic crops. Genes from human, microbes, plants, and animals are being used successfully for this venture. The introduction of these genes can be readily achieved for many plant species using Agrobacterium tumefaciens-mediated plant transformation or direct DNA methods of gene transfer. One of the promising developments in transgenic technology is the insertion of multiple genes (for phase 1 metabolism (cytochrome P450s) and phase 2 metabolism (GSH, GT etc.) for the complete degradation of the xenobiotics within the plant system. In addition to the use of transgenic plants overexpressed with P450 and GST genes, various transgenic plants expressing bacterial genes can be used for the enhanced degradation and remediation of herbicides, explosives

  4. Wired to the roots: impact of root-beneficial microbe interactions on aboveground plant physiology and protection.

    PubMed

    Kumar, Amutha Sampath; Bais, Harsh P

    2012-12-01

    Often, plant-pathogenic microbe interactions are discussed in a host-microbe two-component system, however very little is known about how the diversity of rhizospheric microbes that associate with plants affect host performance against pathogens. There are various studies, which specially direct the importance of induced systemic defense (ISR) response in plants interacting with beneficial rhizobacteria, yet we don't know how rhizobacterial associations modulate plant physiology. In here, we highlight the many dimensions within which plant roots associate with beneficial microbes by regulating aboveground physiology. We review approaches to study the causes and consequences of plant root association with beneficial microbes on aboveground plant-pathogen interactions. The review provides the foundations for future investigations into the impact of the root beneficial microbial associations on plant performance and innate defense responses.

  5. Fast-cycling unit of root turnover in perennial herbaceous plants in a cold temperate ecosystem.

    PubMed

    Sun, Kai; McCormack, M Luke; Li, Le; Ma, Zeqing; Guo, Dali

    2016-01-21

    Roots of perennial plants have both persistent portion and fast-cycling units represented by different levels of branching. In woody species, the distal nonwoody branch orders as a unit are born and die together relatively rapidly (within 1-2 years). However, whether the fast-cycling units also exist in perennial herbs is unknown. We monitored root demography of seven perennial herbs over two years in a cold temperate ecosystem and we classified the largest roots on the root collar or rhizome as basal roots, and associated finer laterals as secondary, tertiary and quaternary roots. Parallel to woody plants in which distal root orders form a fast-cycling module, basal root and its finer laterals also represent a fast-cycling module in herbaceous plants. Within this module, basal roots had a lifespan of 0.5-2 years and represented 62-87% of total root biomass, thus dominating annual root turnover (60%-81% of the total). Moreover, root traits including root length, tissue density, and biomass were useful predictors of root lifespan. We conclude that both herbaceous and woody plants have fast-cycling modular units and future studies identifying the fast-cycling module across plant species should allow better understanding of how root construction and turnover are linked to whole-plant strategies.

  6. Fast-cycling unit of root turnover in perennial herbaceous plants in a cold temperate ecosystem

    PubMed Central

    Sun, Kai; Luke McCormack, M.; Li, Le; Ma, Zeqing; Guo, Dali

    2016-01-01

    Roots of perennial plants have both persistent portion and fast-cycling units represented by different levels of branching. In woody species, the distal nonwoody branch orders as a unit are born and die together relatively rapidly (within 1–2 years). However, whether the fast-cycling units also exist in perennial herbs is unknown. We monitored root demography of seven perennial herbs over two years in a cold temperate ecosystem and we classified the largest roots on the root collar or rhizome as basal roots, and associated finer laterals as secondary, tertiary and quaternary roots. Parallel to woody plants in which distal root orders form a fast-cycling module, basal root and its finer laterals also represent a fast-cycling module in herbaceous plants. Within this module, basal roots had a lifespan of 0.5–2 years and represented 62–87% of total root biomass, thus dominating annual root turnover (60%–81% of the total). Moreover, root traits including root length, tissue density, and biomass were useful predictors of root lifespan. We conclude that both herbaceous and woody plants have fast-cycling modular units and future studies identifying the fast-cycling module across plant species should allow better understanding of how root construction and turnover are linked to whole-plant strategies. PMID:26791578

  7. Fast-cycling unit of root turnover in perennial herbaceous plants in a cold temperate ecosystem

    NASA Astrophysics Data System (ADS)

    Sun, Kai; Luke McCormack, M.; Li, Le; Ma, Zeqing; Guo, Dali

    2016-01-01

    Roots of perennial plants have both persistent portion and fast-cycling units represented by different levels of branching. In woody species, the distal nonwoody branch orders as a unit are born and die together relatively rapidly (within 1-2 years). However, whether the fast-cycling units also exist in perennial herbs is unknown. We monitored root demography of seven perennial herbs over two years in a cold temperate ecosystem and we classified the largest roots on the root collar or rhizome as basal roots, and associated finer laterals as secondary, tertiary and quaternary roots. Parallel to woody plants in which distal root orders form a fast-cycling module, basal root and its finer laterals also represent a fast-cycling module in herbaceous plants. Within this module, basal roots had a lifespan of 0.5-2 years and represented 62-87% of total root biomass, thus dominating annual root turnover (60%-81% of the total). Moreover, root traits including root length, tissue density, and biomass were useful predictors of root lifespan. We conclude that both herbaceous and woody plants have fast-cycling modular units and future studies identifying the fast-cycling module across plant species should allow better understanding of how root construction and turnover are linked to whole-plant strategies.

  8. Enhanced Gravitropism of Roots with a Disrupted Cap Actin Cytoskeleton1

    PubMed Central

    Hou, Guichuan; Mohamalawari, Deepti R.; Blancaflor, Elison B.

    2003-01-01

    The actin cytoskeleton has been proposed to be a major player in plant gravitropism. However, understanding the role of actin in this process is far from complete. To address this problem, we conducted an analysis of the effect of Latrunculin B (Lat B), a potent actin-disrupting drug, on root gravitropism using various parameters that included detailed curvature kinetics, estimation of gravitropic sensitivity, and monitoring of curvature development after extended clinorotation. Lat B treatment resulted in a promotion of root curvature after a 90° reorientation in three plant species tested. More significantly, the sensitivity of maize (Zea mays) roots to gravity was enhanced after actin disruption, as determined from a comparison of presentation time of Lat B-treated versus untreated roots. A short 10-min gravistimulus followed by extended rotation on a 1-rpm clinostat resulted in extensive gravitropic responses, manifested as curvature that often exceeded 90°. Application of Lat B to the cap or elongation zone of maize roots resulted in the disruption of the actin cytoskeleton, which was confined to the area of localized Lat B application. Only roots with Lat B applied to the cap displayed the strong curvature responses after extended clinorotation. Our study demonstrates that disrupting the actin cytoskeleton in the cap leads to the persistence of a signal established by a previous gravistimulus. Therefore, actin could function in root gravitropism by providing a mechanism to regulate the proliferation of a gravitropic signal originating from the cap to allow the root to attain its correct orientation or set point angle. PMID:12644685

  9. Oxygen absorption by adventitious roots promotes the survival of completely submerged terrestrial plants

    PubMed Central

    Ayi, Qiaoli; Zeng, Bo; Liu, Jianhui; Li, Siqi; van Bodegom, Peter M.; Cornelissen, Johannes H. C.

    2016-01-01

    Background and Aims Flooding imposes stress upon terrestrial plants because it results in oxygen deficiency, which is considered a major problem for submerged plants. A common response of terrestrial plants to flooding is the formation of aquatic adventitious roots. Some studies have shown that adventitious roots on submerged plants are capable of absorbing water and nutrients. However, there is no experimental evidence for the possible oxygen uptake function of adventitious roots or for how important this function might be for the survival of plants during prolonged submergence. This study aims to investigate whether adventitious roots absorb oxygen from the water column, and whether this new function is beneficial to the survival of completely submerged plants. Methods Taking Alternanthera philoxeroides (Mart.) Griseb. as a representative species, the profiling of the underwater oxygen gradient towards living and dead adventitious roots on completely submerged plants was conducted, the oxygen concentration in stem nodes with and without adventitious roots was measured, and the growth, survival and non-structural carbohydrate content of completely submerged plants with and without adventitious roots was investigated. Key Results Oxygen profiles in the water column of adventitious roots showed that adventitious roots absorbed oxygen from water. It is found that the oxygen concentration in stem nodes having adventitious roots was higher than that in stem nodes without adventitious roots, which implies that the oxygen absorbed by adventitious roots from water was subsequently transported from the roots to other plant tissues. Compared with plants whose adventitious roots had been pruned, those with intact adventitious roots had slower leaf shedding, slower plant mass reduction, more efficient carbohydrate economy and prolonged survival when completely submerged. Conclusions The adventitious roots of A. philoxeroides formed upon submergence can absorb oxygen from

  10. Oxygen absorption by adventitious roots promotes the survival of completely submerged terrestrial plants.

    PubMed

    Ayi, Qiaoli; Zeng, Bo; Liu, Jianhui; Li, Siqi; van Bodegom, Peter M; Cornelissen, Johannes H C

    2016-04-10

    Flooding imposes stress upon terrestrial plants because it results in oxygen deficiency, which is considered a major problem for submerged plants. A common response of terrestrial plants to flooding is the formation of aquatic adventitious roots. Some studies have shown that adventitious roots on submerged plants are capable of absorbing water and nutrients. However, there is no experimental evidence for the possible oxygen uptake function of adventitious roots or for how important this function might be for the survival of plants during prolonged submergence. This study aims to investigate whether adventitious roots absorb oxygen from the water column, and whether this new function is beneficial to the survival of completely submerged plants. TakingAlternanthera philoxeroides(Mart.) Griseb. as a representative species, the profiling of the underwater oxygen gradient towards living and dead adventitious roots on completely submerged plants was conducted, the oxygen concentration in stem nodes with and without adventitious roots was measured, and the growth, survival and non-structural carbohydrate content of completely submerged plants with and without adventitious roots was investigated. Oxygen profiles in the water column of adventitious roots showed that adventitious roots absorbed oxygen from water. It is found that the oxygen concentration in stem nodes having adventitious roots was higher than that in stem nodes without adventitious roots, which implies that the oxygen absorbed by adventitious roots from water was subsequently transported from the roots to other plant tissues. Compared with plants whose adventitious roots had been pruned, those with intact adventitious roots had slower leaf shedding, slower plant mass reduction, more efficient carbohydrate economy and prolonged survival when completely submerged. The adventitious roots ofA. philoxeroidesformed upon submergence can absorb oxygen from ambient water, thereby alleviating the adverse effects of

  11. Adhesion of plant roots to poly-L-lysine coated polypropylene substrates.

    PubMed

    Towler, Melissa J; Weathers, Pamela J

    2003-03-06

    The ability to immobilize plant tissue in a bioreactor is an important process tool. We have shown that roots of several species rapidly attach to poly-L-lysine coated polypropylene mesh in a liquid environment. Using transformed roots of Artemisia annua as a model, the attachment process was found to be enhanced by sheep serum, but not BSA and inhibited by excess Mn(2+), but unaffected by Ca(2+) or Mg(2+). Attempts to characterize the molecule(s) responsible for binding using lectins and antibodies showed that the binding site does not appear to be glycosylated or vitronectin-like. This method of rapid attachment should prove useful for controlled immobilization of roots in bioreactors. Copyright 2002 Elsevier Science B.V.

  12. Transport of silicon from roots to panicles in plants.

    PubMed

    Ma, Jian Feng; Yamaji, Naoki; Mitani-Ueno, Namiki

    2011-01-01

    Silicon (Si) is the most abundant minerals in soil and exerts beneficial effects on plant growth by alleviating various stresses. The transport of Si from soil to the panicles is mediated by different transporters. Lsi1, belonging to a NIP group of the aquaporin family, is responsible for the uptake of Si from soil into the root cells in both dicots and monocots although its expression patterns and cellular localization differ with plant species. The subsequent transport of Si out of the root cells towards the stele is medicated by an active efflux transporter, Lsi2. Lsi1 and Lsi2 are polarly localized at the distal and proximal sides, respectively, of both exodermis and endodermis in rice root. Silicon in the xylem sap is presented in the form of monosilicic acid and is unloaded by Lsi6, a homolog of Lsi1 in rice. Lsi6 is also involved in the inter-vascular transfer of Si at the node, which is necessary for preferential Si distribution to the panicles.

  13. Transport of silicon from roots to panicles in plants

    PubMed Central

    MA, Jian Feng; YAMAJI, Naoki; MITANI-UENO, Namiki

    2011-01-01

    Silicon (Si) is the most abundant minerals in soil and exerts beneficial effects on plant growth by alleviating various stresses. The transport of Si from soil to the panicles is mediated by different transporters. Lsi1, belonging to a NIP group of the aquaporin family, is responsible for the uptake of Si from soil into the root cells in both dicots and monocots although its expression patterns and cellular localization differ with plant species. The subsequent transport of Si out of the root cells towards the stele is medicated by an active efflux transporter, Lsi2. Lsi1 and Lsi2 are polarly localized at the distal and proximal sides, respectively, of both exodermis and endodermis in rice root. Silicon in the xylem sap is presented in the form of monosilicic acid and is unloaded by Lsi6, a homolog of Lsi1 in rice. Lsi6 is also involved in the inter-vascular transfer of Si at the node, which is necessary for preferential Si distribution to the panicles. PMID:21785256

  14. Induction of root colonization by Piriformospora indica leads to enhanced asiaticoside production in Centella asiatica.

    PubMed

    Satheesan, Jisha; Narayanan, Anith K; Sakunthala, Manjula

    2012-04-01

    Centella asiatica (Indian pennywort) has wide application in Indian and Chinese traditional medicines with documented evidence for wound healing and neuroprotective and anti-aging potential. Asiaticoside, a trisaccharide triterpene, is the most medicinally active compound in the plant. β-Amyrin synthase and squalene synthase have been identified as the two key genes in the triterpenoid pathway which regulate the production of asiaticoside in C. asiatica. The paper reports salient findings of our study utilizing the growth-promoting endophytic fungus Piriformospora indica to successfully colonize roots of C. asiatica in vitro cultures for investigating the effect of the mutualistic association on asiaticoside production. Co-cultivation of P. indica resulted in the rapid enhancement of root and shoot biomass of host plant, which was visible after 7 days of culture and continued up to 45 days. P. indica co-cultivation also favored the synthesis of asiaticosides, as evidenced by HPLC analysis which indicated about twofold increase (0.53% (w/w) in leaves and 0.23% (w/w) in whole plant) over control (0.33% (w/w) in leaves and 0.14% (w/w) in whole plant). Real-time PCR results confirmed the strong upregulation of squalene synthase and β-amyrin synthase transcripts in P. indica-challenged plants compared with the control. Our data demonstrate the potential use of P. indica as a means to enhance plant secondary metabolite production in planta with scope for further field evaluation. © Springer-Verlag 2011

  15. Partial flooding enhances aeration in adventitious roots of black willow (Salix nigra) cuttings.

    PubMed

    Li, Shuwen; Reza Pezeshki, S; Douglas Shields, F

    2006-04-01

    Black willow (Salix nigra) cuttings are used for streambank stabilization where they are subjected to a range of soil moisture conditions including flooding. Flooding has been shown to adversely impact cutting performance, and improved understanding of natural adaptations to flooding might suggest handling and planting techniques to enhance success. However, data assessing the root aeration in adventitious roots that are developed on cuttings of woody species are scant. In addition, it appears that no data are available regarding aeration of the root system under partially flooded conditions. This experiment was designed to examine the effects of continuous flooding (CF) and partial flooding (PF) on aerenchyma formation and radial oxygen loss (ROL) in black willow cuttings. Photosynthetic and growth responses to these conditions were also investigated. Under laboratory condition, replicated potted cuttings were subjected to three treatments: no flooding (control, C), CF, and PF. Water was maintained above the soil surface in CF and at 10 cm depth in PF. Results indicated that after the 28-d treatments, root porosity ranged between 28.6% and 33.0% for the CF and C plants but was greater for the PF plants (39.2% for the drained and 37.2% for the flooded portions). A similar response pattern was found for ROL. In addition, CF treatment led to decreases in final root biomass and root/shoot ratio. Neither CF nor PF had any detectable adverse effects on plant gas exchange or photosystem II functioning. Our results indicated that S. nigra cuttings exhibited avoidance mechanisms in response to flooding, especially the partially flooded condition which is the most common occurrence in riparian systems.

  16. A root moisture sensor for plants in microgravity

    NASA Astrophysics Data System (ADS)

    Clark, G. J.; Neville, G. E.; Dreschel, T. W.

    1994-11-01

    Development of components for bioregenerative life-support systems is a vital step toward long-term space exploration. The culturing of plants in a microgravity environment may be optimized by the use of appropriate sensors and controllers. This paper describes a sensor developed for determining the amount of fluid (nutrient solution) available on the surface of a porous ceramic nutrient delivery substrate to the roots of conventional crop plants. The sensor is based on the change in thermal capacitance and thermal conductance near the surface as the moisture content changes. The sensor could be employed as a data acquisition and control sensor to support the automated monitoring of plants grown in a microgravity environment.

  17. A root moisture sensor for plants in microgravity.

    PubMed

    Clark, G J; Neville, G E; Dreschel, T W

    1994-11-01

    Development of components for bioregenerative life-support systems is a vital step toward long-term space exploration. The culturing of plants in a microgravity environment may be optimized by the use of appropriate sensors and controllers. This paper describes a sensor developed for determining the amount of fluid (nutrient solution) available on the surface of a porous ceramic nutrient delivery substrate to the roots of conventional crop plants. The sensor is based on the change in thermal capacitance and thermal conductance near the surface as the moisture content changes. The sensor could be employed as a data acquisition and control sensor to support the automated monitoring of plants grown in a microgravity environment.

  18. Aquatic adventitious roots of the wetland plant Meionectes brownii can photosynthesize: implications for root function during flooding.

    PubMed

    Rich, Sarah Meghan; Ludwig, Martha; Pedersen, Ole; Colmer, Timothy David

    2011-04-01

    • Many wetland plants produce aquatic adventitious roots from submerged stems. Aquatic roots can form chloroplasts, potentially producing endogenous carbon and oxygen. Here, aquatic root photosynthesis was evaluated in the wetland plant Meionectes brownii, which grows extensive stem-borne aquatic roots during submergence. • Underwater photosynthetic light and CO(2) response curves were determined for aquatic-adapted leaves, stems and aquatic roots of M. brownii. Oxygen microelectrode and (14)CO(2)-uptake experiments determined shoot inputs of O(2) and photosynthate into aquatic roots. • Aquatic adventitious roots contain a complete photosynthetic pathway. Underwater photosynthetic rates are similar to those of stems, with a maximum net photosynthetic rate (P(max)) of 0.38 μmol O(2) m(-2) s(-1); however, this is c. 30-fold lower than that of aquatic-adapted leaves. Under saturating light with 300 mmol m(-3) dissolved CO(2), aquatic roots fix carbon at 0.016 μmol CO(2) g(-1) DM s(-1). Illuminated aquatic roots do not rely on exogenous inputs of O(2). • The photosynthetic ability of aquatic roots presumably offers an advantage to submerged M. brownii as aquatic roots, unlike sediment roots, need little O(2) and carbohydrate inputs from the shoot when illuminated. © 2010 The Authors. New Phytologist © 2010 New Phytologist Trust.

  19. Root exudates of wetland plants influenced by nutrient status and types of plant cultivation.

    PubMed

    Wu, Fu Yong; Chung, Anna King Chuen; Tam, Nora Fung Yee; Wong, Ming Hung

    2012-07-01

    The present study investigated the amounts of root exudates and composition of organic acids released from two wetland plants (Typha latifolia and Vetiver zizanioides) under two nutrient treatments: low level (0.786 mM N and 0.032 mM P) and high level (7.86 mM N and 0.32 mM P) and two types of plant cultivation: monoculture and co-culture of the two plants. Low nutrient treatment significantly (p < 0.05) increased the root exudates of T. latifolia during the initial growth period (1-21 d) and those of V. zizanioides and the co-culture during the whole growth period. The concentrations of dissolved organic carbon in the root exudates of the co-culture in the low nutrient treatment were 3.23-7.91 times of those in the high nutrient treatment during the medium growth period (7-28 d). The compositions of organic acids varied between the two plant species and between the two nutrient treatments. The pattern of organic acids was also different between the co-culture and the monoculture. Oxalic acid was by far the major organic acid exuded from the two wetland plants. The present study on root exudates suggests that co-culture of wetland plant species would be more useful in the reclamation of waste water than a monoculture system.

  20. Denitrification by plant roots? New aspects of plant plasma membrane-bound nitrate reductase.

    PubMed

    Eick, Manuela; Stöhr, Christine

    2012-10-01

    A specific form of plasma membrane-bound nitrate reductase in plants is restricted to roots. Two peptides originated from plasma membrane integral proteins isolated from Hordeum vulgare have been assigned as homologues to the subunit NarH of respiratory nitrate reductase of Escherichia coli. Corresponding sequences have been detected for predicted proteins of Populus trichocarpa with high degree of identities for the subunits NarH (75%) and NarG (65%), however, with less accordance for the subunit NarI. These findings coincide with biochemical properties, particularly in regard to the electron donors menadione and succinate. Together with the root-specific and plasma membrane-bound nitrite/NO reductase, nitric oxide is produced under hypoxic conditions in the presence of nitrate. In this context, a possible function in nitrate respiration of plant roots and an involvement of plants in denitrification processes are discussed.

  1. Plant-in-chip: Microfluidic system for studying root growth and pathogenic interactions in Arabidopsis

    NASA Astrophysics Data System (ADS)

    Parashar, Archana; Pandey, Santosh

    2011-06-01

    We report a microfluidic platform for the hydroponic growth of Arabidopsis plants with high-resolution visualization of root development and root-pathogen interactions. The platform comprises a set of parallel microchannels with individual input/output ports where 1-day old germinated seedlings are initially placed. Under optimum conditions, a root system grows in each microchannel and its images are recorded over a 198-h period. Different concentrations of plant growth media show different root growth characteristics. Later, the developed roots are inoculated with two plant pathogens (nematodes and zoospores) and their physicochemical interactions with the live root systems are observed.

  2. Community- Weighted Mean Plant Traits Predict Small Scale Distribution of Insect Root Herbivore Abundance

    PubMed Central

    Jeltsch, Florian; Wurst, Susanne

    2015-01-01

    Small scale distribution of insect root herbivores may promote plant species diversity by creating patches of different herbivore pressure. However, determinants of small scale distribution of insect root herbivores, and impact of land use intensity on their small scale distribution are largely unknown. We sampled insect root herbivores and measured vegetation parameters and soil water content along transects in grasslands of different management intensity in three regions in Germany. We calculated community-weighted mean plant traits to test whether the functional plant community composition determines the small scale distribution of insect root herbivores. To analyze spatial patterns in plant species and trait composition and insect root herbivore abundance we computed Mantel correlograms. Insect root herbivores mainly comprised click beetle (Coleoptera, Elateridae) larvae (43%) in the investigated grasslands. Total insect root herbivore numbers were positively related to community-weighted mean traits indicating high plant growth rates and biomass (specific leaf area, reproductive- and vegetative plant height), and negatively related to plant traits indicating poor tissue quality (leaf C/N ratio). Generalist Elaterid larvae, when analyzed independently, were also positively related to high plant growth rates and furthermore to root dry mass, but were not related to tissue quality. Insect root herbivore numbers were not related to plant cover, plant species richness and soil water content. Plant species composition and to a lesser extent plant trait composition displayed spatial autocorrelation, which was not influenced by land use intensity. Insect root herbivore abundance was not spatially autocorrelated. We conclude that in semi-natural grasslands with a high share of generalist insect root herbivores, insect root herbivores affiliate with large, fast growing plants, presumably because of availability of high quantities of food. Affiliation of insect root

  3. Community-Weighted Mean Plant Traits Predict Small Scale Distribution of Insect Root Herbivore Abundance.

    PubMed

    Sonnemann, Ilja; Pfestorf, Hans; Jeltsch, Florian; Wurst, Susanne

    2015-01-01

    Small scale distribution of insect root herbivores may promote plant species diversity by creating patches of different herbivore pressure. However, determinants of small scale distribution of insect root herbivores, and impact of land use intensity on their small scale distribution are largely unknown. We sampled insect root herbivores and measured vegetation parameters and soil water content along transects in grasslands of different management intensity in three regions in Germany. We calculated community-weighted mean plant traits to test whether the functional plant community composition determines the small scale distribution of insect root herbivores. To analyze spatial patterns in plant species and trait composition and insect root herbivore abundance we computed Mantel correlograms. Insect root herbivores mainly comprised click beetle (Coleoptera, Elateridae) larvae (43%) in the investigated grasslands. Total insect root herbivore numbers were positively related to community-weighted mean traits indicating high plant growth rates and biomass (specific leaf area, reproductive- and vegetative plant height), and negatively related to plant traits indicating poor tissue quality (leaf C/N ratio). Generalist Elaterid larvae, when analyzed independently, were also positively related to high plant growth rates and furthermore to root dry mass, but were not related to tissue quality. Insect root herbivore numbers were not related to plant cover, plant species richness and soil water content. Plant species composition and to a lesser extent plant trait composition displayed spatial autocorrelation, which was not influenced by land use intensity. Insect root herbivore abundance was not spatially autocorrelated. We conclude that in semi-natural grasslands with a high share of generalist insect root herbivores, insect root herbivores affiliate with large, fast growing plants, presumably because of availability of high quantities of food. Affiliation of insect root

  4. Graphene quantum dots as enhanced plant growth regulators: effects on coriander and garlic plants.

    PubMed

    Chakravarty, Disha; Erande, Manisha B; Late, Dattatray J

    2015-10-01

    We report investigations on the use of graphene quantum dots for growth enhancement in coriander (Coriandrum sativam L.) and garlic (Allium sativum) plants. The as-received seeds of coriander and garlic were treated with 0.2 mg mL(-1) of graphene quantum dots for 3 h before planting. Graphene quantum dots enhanced the growth rate in coriander and garlic plants, including leaves, roots, shoots, flowers and fruits, when the seeds were treated with graphene quantum dots. Our investigations open up the opportunity to use graphene quantum dots as plant growth regulators that can be used in a variety of other food plants for high yield. © 2015 Society of Chemical Industry.

  5. Withania somnifera Root Extract Enhances Chemotherapy through ‘Priming’

    PubMed Central

    Yang, Ling; Chuang, Kun-Lin; Sahuri-Arisoylu, Meliz; Wu, Li-Hong; Bligh, S. W. Annie; Bell, Jimmy David

    2017-01-01

    Withania somnifera extracts are known for their anti-cancerous, anti-inflammatory and antioxidative properties. One of their mechanisms of actions is to modulate mitochondrial function through increasing oxidative stress. Recently ‘priming’ has been suggested as a potential mechanism for enhancing cancer cell death. In this study we demonstrate that ‘priming’, in HT-29 colon cells, with W. somnifera root extract increased the potency of the chemotherapeutic agent cisplatin. We have also showed the W. somnifera root extract enhanced mitochondrial dysfunction and that the underlying mechanism of ‘priming’ was selectively through increased ROS. Moreover, we showed that this effect was not seen in non-cancerous cells. PMID:28129345

  6. Ammonium enhances resistance to salinity stress in citrus plants.

    PubMed

    Fernández-Crespo, Emma; Camañes, Gemma; García-Agustín, Pilar

    2012-08-15

    In this work, we demonstrate that NH₄⁺ nutrition in citrange Carrizo plants acts as an inducer of resistance against salinity conditions. We investigated its mode of action and provide evidence that NH₄⁺ confers resistance by priming abscisic acid and polyamines, and enhances H₂O₂ and proline basal content. Moreover, we observed reduced Cl⁻ uptake as well as enhanced PHGPx expression after salt stress. Control and N-NH₄⁺ plants showed optimal growth. However, N-NH₄⁺ plants displayed greater dry weight and total lateral roots than control plants, but these differences were not observed for primary root length. Our results revealed that N-NH₄⁺ treatment induces a similar phenotypical response to the recent stress-induced morphogenetic response (SIMRs). The hypothesis is that N-NH₄⁺ treatment triggers mild chronic stress in citrange Carrizo plants, which might explain the SIMR observed. Moreover, we observed modulators of stress signaling, such as H₂O₂ in N-NH₄⁺ plants, which could acts as an intermediary between stress and the development of the SIMR phenotype. This observation suggests that NH₄⁺ treatments induce a mild stress condition that primes the citrange Carrizo defense response by stress imprinting and confers protection against subsequent salt stress.

  7. Nitric oxide mediates root K+/Na+ balance in a mangrove plant, Kandelia obovata, by enhancing the expression of AKT1-type K+ channel and Na+/H+ antiporter under high salinity.

    PubMed

    Chen, Juan; Xiong, Duan-Ye; Wang, Wen-Hua; Hu, Wen-Jun; Simon, Martin; Xiao, Qiang; Chen, Juan; Liu, Ting-Wu; Liu, Xiang; Zheng, Hai-Lei

    2013-01-01

    It is well known that nitric oxide (NO) enhances salt tolerance of glycophytes. However, the effect of NO on modulating ionic balance in halophytes is not very clear. This study focuses on the role of NO in mediating K(+)/Na(+) balance in a mangrove species, Kandelia obovata Sheue, Liu and Yong. We first analyzed the effects of sodium nitroprusside (SNP), an NO donor, on ion content and ion flux in the roots of K. obovata under high salinity. The results showed that 100 μM SNP significantly increased K(+) content and Na(+) efflux, but decreased Na(+) content and K(+) efflux. These effects of NO were reversed by specific NO synthesis inhibitor and scavenger, which confirmed the role of NO in retaining K(+) and reducing Na(+) in K. obovata roots. Using western-blot analysis, we found that NO increased the protein expression of plasma membrane (PM) H(+)-ATPase and vacuolar Na(+)/H(+) antiporter, which were crucial proteins for ionic balance. To further clarify the molecular mechanism of NO-modulated K(+)/Na(+) balance, partial cDNA fragments of inward-rectifying K(+) channel, PM Na(+)/H(+) antiporter, PM H(+)-ATPase, vacuolar Na(+)/H(+) antiporter and vacuolar H(+)-ATPase subunit c were isolated. Results of quantitative real-time PCR showed that NO increased the relative expression levels of these genes, while this increase was blocked by NO synthesis inhibitors and scavenger. Above results indicate that NO greatly contribute to K(+)/Na(+) balance in high salinity-treated K. obovata roots, by activating AKT1-type K(+) channel and Na(+)/H(+) antiporter, which are the critical components in K(+)/Na(+) transport system.

  8. Nitric Oxide Mediates Root K+/Na+ Balance in a Mangrove Plant, Kandelia obovata, by Enhancing the Expression of AKT1-Type K+ Channel and Na+/H+ Antiporter under High Salinity

    PubMed Central

    Wang, Wen-Hua; Hu, Wen-Jun; Simon, Martin; Xiao, Qiang; Chen, Juan; Liu, Ting-Wu; Liu, Xiang; Zheng, Hai-Lei

    2013-01-01

    It is well known that nitric oxide (NO) enhances salt tolerance of glycophytes. However, the effect of NO on modulating ionic balance in halophytes is not very clear. This study focuses on the role of NO in mediating K+/Na+ balance in a mangrove species, Kandelia obovata Sheue, Liu and Yong. We first analyzed the effects of sodium nitroprusside (SNP), an NO donor, on ion content and ion flux in the roots of K. obovata under high salinity. The results showed that 100 μM SNP significantly increased K+ content and Na+ efflux, but decreased Na+ content and K+ efflux. These effects of NO were reversed by specific NO synthesis inhibitor and scavenger, which confirmed the role of NO in retaining K+ and reducing Na+ in K. obovata roots. Using western-blot analysis, we found that NO increased the protein expression of plasma membrane (PM) H+-ATPase and vacuolar Na+/H+ antiporter, which were crucial proteins for ionic balance. To further clarify the molecular mechanism of NO-modulated K+/Na+ balance, partial cDNA fragments of inward-rectifying K+ channel, PM Na+/H+ antiporter, PM H+-ATPase, vacuolar Na+/H+ antiporter and vacuolar H+-ATPase subunit c were isolated. Results of quantitative real-time PCR showed that NO increased the relative expression levels of these genes, while this increase was blocked by NO synthesis inhibitors and scavenger. Above results indicate that NO greatly contribute to K+/Na+ balance in high salinity-treated K. obovata roots, by activating AKT1-type K+ channel and Na+/H+ antiporter, which are the critical components in K+/Na+ transport system. PMID:23977070

  9. Topsoil drying combined with increased sulfur supply leads to enhanced aliphatic glucosinolates in Brassica juncea leaves and roots.

    PubMed

    Tong, Yu; Gabriel-Neumann, Elke; Ngwene, Benard; Krumbein, Angelika; George, Eckhard; Platz, Stefanie; Rohn, Sascha; Schreiner, Monika

    2014-01-01

    The decrease of water availability is leading to an urgent demand to reduce the plants' water supply. This study evaluates the effect of topsoil drying, combined with varying sulfur (S) supply on glucosinolates in Brassica juncea in order to reveal whether a partial root drying may already lead to a drought-induced glucosinolate increase promoted by an enhanced S supply. Without decreasing biomass, topsoil drying initiated an increase in aliphatic glucosinolates in leaves and in topsoil dried roots supported by increased S supply. Simultaneously, abscisic acid was determined, particularly in dehydrated roots, associated with an increased abscisic acid concentration in leaves under topsoil drying. This indicates that the dehydrated roots were the direct interface for the plants' stress response and that the drought-induced accumulation of aliphatic glucosinolates is related to abscisic acid formation. Indole and aromatic glucosinolates decreased, suggesting that these glucosinolates are less involved in the plants' response to drought.

  10. Characterizing the Physics of Plant Root Gravitropism: A Systems Modeling Approach

    DTIC Science & Technology

    1999-01-01

    with its root directly downward, the root and stem undergo a gravitropic response. Statoliths (gravity-sensing organelles) within the root cap respond...this study is to model the plant root gravitropic response using classical controls and system identification principles. Specific objectives of this

  11. Significance of Plant Root Microorganisms in Reclaiming Water in CELSS

    NASA Technical Reports Server (NTRS)

    Bubenheim, David L.; Greene, Catherine; Wignarajah, Kanapathipillai; Kliss, Mark H. (Technical Monitor)

    1996-01-01

    Since many microorganisms demonstrate the ability to quickly break down complex mixtures of waste and environmental contaminants, examining their potential use for water recycling in a closed environment is appealing. Water contributes approximately 90 percent of the life sustaining provisions in a human space habitat. Nearly half of the daily water requirements will be used for personal hygiene and dish washing. The primary contaminants of the used "gray" water will be the cleansing agents or soaps used to carry out these functions. Reclaiming water from the gray water waste streams is one goal of the NASA program, Controlled Ecological Life Support Systems (CELSS). The microorganisms of plane roots are well documented to be of a beneficial effect to promote plant growth. Most plants exhibit a range of bacteria and fungi which can be highly plant-specific. In our investigations with lettuce grown in hydroponic culture, we identified a microflora of normal rhizosphere. When the roots were exposed to an anionic surfactant, the species diversity changed, based on morphological characteristics, with the numbers of species being reduced from 7 to 2 after 48 hours of exposure. In addition, the species that became dominant in the presence of the anionic surfactant also demonstrated a dramatic increase in population density which corresponded to the degradation of the surfactant in the root zone. The potential for using these or other rhizosphere bacteria as a primary or secondary waste processor is promising, but a number of issues still warrant investigation; these include but are not limited to: (1) the full identification of the microbes, (2) the classes of surfactants the microbes will degrade, (3) the environmental conditions required for optimal processing efficiency and (4) the ability of transferring the microbes to a non-living solid matrix such as a bioreactor.

  12. Significance of Plant Root Microorganisms in Reclaiming Water in CELSS

    NASA Technical Reports Server (NTRS)

    Bubenheim, David L.; Greene, Catherine; Wignarajah, Kanapathipillai; Kliss, Mark H. (Technical Monitor)

    1996-01-01

    Since many microorganisms demonstrate the ability to quickly break down complex mixtures of waste and environmental contaminants, examining their potential use for water recycling in a closed environment is appealing. Water contributes approximately 90 percent of the life sustaining provisions in a human space habitat. Nearly half of the daily water requirements will be used for personal hygiene and dish washing. The primary contaminants of the used "gray" water will be the cleansing agents or soaps used to carry out these functions. Reclaiming water from the gray water waste streams is one goal of the NASA program, Controlled Ecological Life Support Systems (CELSS). The microorganisms of plane roots are well documented to be of a beneficial effect to promote plant growth. Most plants exhibit a range of bacteria and fungi which can be highly plant-specific. In our investigations with lettuce grown in hydroponic culture, we identified a microflora of normal rhizosphere. When the roots were exposed to an anionic surfactant, the species diversity changed, based on morphological characteristics, with the numbers of species being reduced from 7 to 2 after 48 hours of exposure. In addition, the species that became dominant in the presence of the anionic surfactant also demonstrated a dramatic increase in population density which corresponded to the degradation of the surfactant in the root zone. The potential for using these or other rhizosphere bacteria as a primary or secondary waste processor is promising, but a number of issues still warrant investigation; these include but are not limited to: (1) the full identification of the microbes, (2) the classes of surfactants the microbes will degrade, (3) the environmental conditions required for optimal processing efficiency and (4) the ability of transferring the microbes to a non-living solid matrix such as a bioreactor.

  13. Strigolactones, host recognition signals for root parasitic plants and arbuscular mycorrhizal fungi, from Fabaceae plants.

    PubMed

    Yoneyama, Kaori; Xie, Xiaonan; Sekimoto, Hitoshi; Takeuchi, Yasutomo; Ogasawara, Shin; Akiyama, Kohki; Hayashi, Hideo; Yoneyama, Koichi

    2008-07-01

    Both root parasitic plants and arbuscular mycorrhizal (AM) fungi take advantage of strigolactones, released from plant roots as signal molecules in the initial communication with host plants, in order to commence parasitism and mutualism, respectively. In this study, strigolactones in root exudates from 12 Fabaceae plants, including hydroponically grown white lupin (Lupinus albus), a nonhost of AM fungi, were characterized by comparing retention times of germination stimulants on reverse-phase high-performance liquid chromatography (HPLC) with those of standards and by using tandem mass spectrometry (LC/MS/MS). All the plant species examined were found to exude known strigolactones, such as orobanchol, orobanchyl acetate, and 5-deoxystrigol, suggesting that these strigolactones are widely distributed in the Fabaceae. It should be noted that even the nonmycotrophic L. albus exuded orobanchol, orobanchyl acetate, 5-deoxystrigol, and novel germination stimulants. By contrast to the mycotrophic Fabaceae plant Trifolium pratense, in which phosphorus deficiency promoted strigolactone exudation, neither phosphorus nor nitrogen deficiency increased exudation of these strigolactones in L. albus. Therefore, the regulation of strigolactone production and/or exudation seems to be closely related to the nutrient acquisition strategy of the plants.

  14. Effects of partial root-zone irrigation on hydraulic conductivity in the soil–root system of maize plants

    PubMed Central

    Hu, Tiantian; Kang, Shaozhong; Li, Fusheng; Zhang, Jianhua

    2011-01-01

    Effects of partial root-zone irrigation (PRI) on the hydraulic conductivity in the soil–root system (Lsr) in different root zones were investigated using a pot experiment. Maize plants were raised in split-root containers and irrigated on both halves of the container (conventional irrigation, CI), on one side only (fixed PRI, FPRI), or alternately on one of two sides (alternate PRI, APRI). Results show that crop water consumption was significantly correlated with Lsr in both the whole and irrigated root zones for all three irrigation methods but not with Lsr in the non-irrigated root zone of FPRI. The total Lsr in the irrigated root zone of two PRIs was increased by 49.0–92.0% compared with that in a half root zone of CI, suggesting that PRI has a significant compensatory effect of root water uptake. For CI, the contribution of Lsr in a half root zone to Lsr in the whole root zone was ∼50%. For FPRI, the Lsr in the irrigated root zone was close to that of the whole root zone. As for APRI, the Lsr in the irrigated root zone was greater than that of the non-irrigated root zone. In comparison, the Lsr in the non-irrigated root zone of APRI was much higher than that in the dried zone of FPRI. The Lsr in both the whole and irrigated root zones was linearly correlated with soil moisture in the irrigated root zone for all three irrigation methods. For the two PRI treatments, total water uptake by plants was largely determined by the soil water in the irrigated root zone. Nevertheless, the non-irrigated root zone under APRI also contributed to part of the total crop water uptake, but the continuously non-irrigated root zone under FPRI gradually ceased to contribute to crop water uptake, suggesting that it is the APRI that can make use of all the root system for water uptake, resulting in higher water use efficiency. PMID:21527627

  15. Effects of partial root-zone irrigation on hydraulic conductivity in the soil-root system of maize plants.

    PubMed

    Hu, Tiantian; Kang, Shaozhong; Li, Fusheng; Zhang, Jianhua

    2011-08-01

    Effects of partial root-zone irrigation (PRI) on the hydraulic conductivity in the soil-root system (L(sr)) in different root zones were investigated using a pot experiment. Maize plants were raised in split-root containers and irrigated on both halves of the container (conventional irrigation, CI), on one side only (fixed PRI, FPRI), or alternately on one of two sides (alternate PRI, APRI). Results show that crop water consumption was significantly correlated with L(sr) in both the whole and irrigated root zones for all three irrigation methods but not with L(sr) in the non-irrigated root zone of FPRI. The total L(sr) in the irrigated root zone of two PRIs was increased by 49.0-92.0% compared with that in a half root zone of CI, suggesting that PRI has a significant compensatory effect of root water uptake. For CI, the contribution of L(sr) in a half root zone to L(sr) in the whole root zone was ∼50%. For FPRI, the L(sr) in the irrigated root zone was close to that of the whole root zone. As for APRI, the L(sr) in the irrigated root zone was greater than that of the non-irrigated root zone. In comparison, the L(sr) in the non-irrigated root zone of APRI was much higher than that in the dried zone of FPRI. The L(sr) in both the whole and irrigated root zones was linearly correlated with soil moisture in the irrigated root zone for all three irrigation methods. For the two PRI treatments, total water uptake by plants was largely determined by the soil water in the irrigated root zone. Nevertheless, the non-irrigated root zone under APRI also contributed to part of the total crop water uptake, but the continuously non-irrigated root zone under FPRI gradually ceased to contribute to crop water uptake, suggesting that it is the APRI that can make use of all the root system for water uptake, resulting in higher water use efficiency.

  16. Iron deficiency enhances the levels of ascorbate, glutathione, and related enzymes in sugar beet roots.

    PubMed

    Zaharieva, Tatiana B; Abadía, Javier

    2003-06-01

    The effects of Fe deficiency stress on the levels of ascorbate and glutathione, and on the activities of the enzymes ferric chelate reductase, glutathione reductase (EC 1.6.4.2), ascorbate free-radical reductase (EC 1.6.5.4) and ascorbate peroxidase (EC 1.11.1.11), have been investigated in sugar beet ( Beta vulgaris L.) roots. Plasma membrane vesicles and cytosolic fractions were isolated from the roots of the plants grown in nutrient solutions in the absence or presence of Fe for two weeks. Plants responded to Fe deficiency not only with a 20-fold increase in root ferric chelate reductase activity, but also with moderately increased levels of the general reductants ascorbate (2-fold) and glutathione (1.6-fold). The enzymes of the ascorbate-glutathione cycle in roots were also affected by Fe deficiency. Glutathione reductase activity was enhanced 1.4-fold with Fe deficiency, associated to an increased ratio of reduced to oxidized glutathione, from 3.1 to 5.2. The plasma membrane fraction from iron-deficient roots showed 1.7-fold higher ascorbate free-radical reductase activity, whereas in the cytosolic fraction the enzyme activity was not affected by Fe deficiency. The activity of the cytosolic hemoprotein ascorbate peroxidase decreased approximately by 50% with Fe deprivation. These results show that sugar beet responds to Fe deficiency with metabolic changes affecting components of the ascorbate-glutathione cycle in root cells. This suggests that the ascorbate-glutathione cycle would play certain roles in the general Fe deficiency stress responses in strategy I plants.

  17. Ancestral QTL Alleles from Wild Emmer Wheat Enhance Root Development under Drought in Modern Wheat.

    PubMed

    Merchuk-Ovnat, Lianne; Fahima, Tzion; Ephrath, Jhonathan E; Krugman, Tamar; Saranga, Yehoshua

    2017-01-01

    A near-isogenic line (NIL-7A-B-2), introgressed with a quantitative trait locus (QTL) on chromosome 7AS from wild emmer wheat (Triticum turgidum ssp. dicoccoides) into the background of bread wheat (T. aestivum L.) cv. BarNir, was recently developed and studied in our lab. NIL-7A-B-2 exhibited better productivity and photosynthetic capacity than its recurrent parent across a range of environments. Here we tested the hypothesis that root-system modifications play a major role in NIL-7A-B-2's agronomical superiority. Root-system architecture (dry matter and projected surface area) and shoot parameters of NIL-7A-B-2 and 'BarNir' were evaluated at 40, 62, and 82 days after planting (DAP) in a sand-tube experiment, and root tip number was assessed in a 'cigar-roll' seedling experiment, both under well-watered and water-limited (WL) treatments. At 82 DAP, under WL treatment, NIL-7A-B-2 presented greater investment in deep roots (depth 40-100 cm) than 'BarNir,' with the most pronounced effect recorded in the 60-80 cm soil depth (60 and 40% increase for root dry matter and surface area, respectively). NIL-7A-B-2 had significantly higher root-tip numbers (∼48%) per plant than 'BarNir' under both treatments. These results suggest that the introgression of 7AS QTL from wild emmer wheat induced a deeper root system under progressive water stress, which may enhance abiotic stress resistance and productivity of domesticated wheat.

  18. The consequence of peroxidase overexpression in transgenic plants on root growth and development.

    PubMed

    Lagrimini, L M; Joly, R J; Dunlap, J R; Liu, T T

    1997-03-01

    Transgenic tobacco plants that overproduce the tobacco anionic peroxidase wilt upon reaching maturity, although having functional stomata and normal vascular anatomy and physiology. These plants were examined further to determine the cause for wilting, and thus better understand how the anionic peroxidase functions in plant growth and development. Shoots from young peroxidase overproducing plants were grafted onto wild-type tobacco root stock to determine if the roots could absorb and transmit sufficient water to maintain leaf turgidity. These grafted plants never wilted when grown in the greenhouse though shoot peroxidase activity remained ten-fold greater than in control plants, thus indicating that wilting is a consequence of peroxidase expression in the roots. Close examination of root systems revealed considerably less root mass in the transformed plant, primarily exhibited through a decrease in branching. At flowering, root growth rate and total root mass in transformed plants were less than 50% of control plants although shoot mass and growth rate were unchanged. This is in contrast to root growth in young seedlings where transformed plants performed equivalently to controls. Root hydraulic conductivity was measured to evaluate the effect of elevated peroxidase expression on water absorption and transport; however, no significant change in hydraulic conductivity was found in transformed plants. The consequence of anionic peroxidase overexpression on indoleacetic acid (IAA) metabolism was also examined. No significant difference in IAA levels was observed; however, root elongation in plants overexpressing peroxidase was insensitive to exogenous IAA. It can be concluded that the overexpression of the tobacco anionic peroxidase in transformed plants results in diminished root mass from fewer root branches, which contributes to the wilting phenomenon seen in these plants. Further, this developmental change in transformed plants may be a consequence of the

  19. 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

  20. 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.

  1. Potential involvement of drought-induced Ran GTPase CLRan1 in root growth enhancement in a xerophyte wild watermelon.

    PubMed

    Akashi, Kinya; Yoshimura, Kazuya; Kajikawa, Masataka; Hanada, Kouhei; Kosaka, Rina; Kato, Atsushi; Katoh, Akira; Nanasato, Yoshihiko; Tsujimoto, Hisashi; Yokota, Akiho

    2016-10-01

    Enhanced root growth is known as the survival strategy of plants under drought. Previous proteome analysis in drought-resistant wild watermelon has shown that Ran GTPase, an essential regulator of cell division and proliferation, was induced in the roots under drought. In this study, two cDNAs were isolated from wild watermelon, CLRan1 and CLRan2, which showed a high degree of structural similarity with those of other plant Ran GTPases. Quantitative RT-PCR and promoter-GUS assays suggested that CLRan1 was expressed mainly in the root apex and lateral root primordia, whereas CLRan2 was more broadly expressed in other part of the roots. Immunoblotting analysis confirmed that the abundance of CLRan proteins was elevated in the root apex region under drought stress. Transgenic Arabidopsis overexpressing CLRan1 showed enhanced primary root growth, and the growth was maintained under osmotic stress, indicating that CLRan1 functions as a positive factor for maintaining root growth under stress conditions.

  2. Root respiratory costs of ion uptake, root growth, and root maintenance in wetland plants: efficiency and strategy of O2 use for adaptation to hypoxia.

    PubMed

    Nakamura, Takatoshi; Nakamura, Motoka

    2016-11-01

    Oxygen use in roots is an important aspect of wetland plant ecophysiology, and it depends on the respiratory costs of three major processes: ion uptake, root growth, and root maintenance. However, O2 allocation in wetland plants has received little attention. This study aimed to determine the O2 allocation and specific respiratory cost of each process under hypoxic conditions, to better understand the strategy and efficiency of O2 use in wetland plants. The root respiration rate, nitrogen uptake, and root growth in three Carex species with different growth rates were examined under hypoxic conditions using different N sources, and the respiratory costs of ion uptake, root growth, and root maintenance were statistically estimated. All species exhibited low specific costs and low ratios of O2 allocation for root growth (2.0 ± 0.4 mmol O2 g(-1) and 15.2 ± 2.7 %, respectively). The specific cost of ion uptake was 20-30 % lower in fast-growing species than in slow-growing species. As plant growth rate increased, the O2 allocation ratio for ion uptake increased, and that for root maintenance decreased. The cost was higher when NO3 (-) was fed, than when NH4 (+) was fed, although the pattern of O2 allocation ratios for three processes was similar for NO3 (-) and NH4 (+). Our results indicate that wetland plants primarily employ an O2 use strategy of minimising the respiratory costs of root growth, and fast-growing plants specifically use O2 to maximise ion uptake. These findings provide new insights into ecophysiological behaviours of roots in adaptation to hypoxia.

  3. Adaptive shoot and root responses collectively enhance growth at optimum temperature and limited phosphorus supply of three herbaceous legume species

    PubMed Central

    Suriyagoda, Lalith D. B.; Ryan, Megan H.; Renton, Michael; Lambers, Hans

    2012-01-01

    Background and Aims 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. Methods 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. Key Results 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. Conclusions 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. PMID:22847657

  4. Plant hormone cross-talk: the pivot of root growth.

    PubMed

    Pacifici, Elena; Polverari, Laura; Sabatini, Sabrina

    2015-02-01

    Root indeterminate growth and its outstanding ability to produce new tissues continuously make this organ a highly dynamic structure able to respond promptly to external environmental stimuli. Developmental processes therefore need to be finely tuned, and hormonal cross-talk plays a pivotal role in the regulation of root growth. In contrast to what happens in animals, plant development is a post-embryonic process. A pool of stem cells, placed in a niche at the apex of the meristem, is a source of self-renewing cells that provides cells for tissue formation. During the first days post-germination, the meristem reaches its final size as a result of a balance between cell division and cell differentiation. A complex network of interactions between hormonal pathways co-ordinates such developmental inputs. In recent years, by means of molecular and computational approaches, many efforts have been made aiming to define the molecular components of these networks. In this review, we focus our attention on the molecular mechanisms at the basis of hormone cross-talk during root meristem size determination.

  5. Operational Evaluation of the Root Modules of the Advanced Plant Habitat

    NASA Technical Reports Server (NTRS)

    Monje, O.

    2014-01-01

    Photosynthetic and growth data were collected on APH Root Module. Described Stand pipe system for active moisture control. Tested germination in wicks. Evaluated EC-5 moisture sensors. Demonstrated that Wheat plants can grow in the APH Root Module.

  6. Characterization of Azospirillum Isolated from Nitrogen-Fixing Roots of Harvested Sorghum Plants

    PubMed Central

    Wong, Peter P.; Stenberg, Nancy E.

    1979-01-01

    Root segments of harvested sorghum plants had acetylene reduction activity ranging from 11 to 61 nmol of ethylene formed per h per g (dry weight). Five strains of Azospirillum brasilense sp. nov. were isolated from root segments. PMID:16345484

  7. 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

  8. 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.

  9. Plant Enhancers: A Call for Discovery.

    PubMed

    Weber, Blaise; Zicola, Johan; Oka, Rurika; Stam, Maike

    2016-11-01

    Higher eukaryotes typically contain many different cell types, displaying different cellular functions that are influenced by biotic and abiotic cues. The different functions are characterized by specific gene expression patterns mediated by regulatory sequences such as transcriptional enhancers. Recent genome-wide approaches have identified thousands of enhancers in animals, reviving interest in enhancers in gene regulation. Although the regulatory roles of plant enhancers are as crucial as those in animals, genome-wide approaches have only very recently been applied to plants. Here we review characteristics of enhancers at the DNA and chromatin level in plants and other species, their similarities and differences, and techniques widely used for genome-wide discovery of enhancers in animal systems that can be implemented in plants.

  10. Release from belowground enemies and shifts in root traits as interrelated drivers of alien plant invasion success: a hypothesis.

    PubMed

    Dawson, Wayne

    2015-10-01

    Our understanding of the interrelated mechanisms driving plant invasions, such as the interplay between enemy release and resource-acquisition traits, is biased by an aboveground perspective. To address this bias, I hypothesize that plant release from belowground enemies (especially fungal pathogens) will give invasive plant species a fitness advantage in the alien range, via shifts in root traits (e.g., increased specific root length and branching intensity) that increase resource uptake and competitive ability compared to native species in the alien range, and compared to plants of the invader in its native range. Such root-trait changes could be ecological or evolutionary in nature. I explain how shifts in root traits could occur as a consequence of enemy release and contribute to invasion success of alien plants, and how they could be interrelated with other potential belowground drivers of invasion success (allelopathy, mutualist enhancement). Finally, I outline the approaches that could be taken to test whether belowground enemy release results in increased competitive ability and nutrient uptake by invasive alien plants, via changes in root traits in the alien range.

  11. The RootChip: an integrated microfluidic chip for plant science.

    PubMed

    Grossmann, Guido; Guo, Woei-Jiun; Ehrhardt, David W; Frommer, Wolf B; Sit, Rene V; Quake, Stephen R; Meier, Matthias

    2011-12-01

    Studying development and physiology of growing roots is challenging due to limitations regarding cellular and subcellular analysis under controlled environmental conditions. We describe a microfluidic chip platform, called RootChip, that integrates live-cell imaging of growth and metabolism of Arabidopsis thaliana roots with rapid modulation of environmental conditions. The RootChip has separate chambers for individual regulation of the microenvironment of multiple roots from multiple seedlings in parallel. We demonstrate the utility of The RootChip by monitoring time-resolved growth and cytosolic sugar levels at subcellular resolution in plants by a genetically encoded fluorescence sensor for glucose and galactose. The RootChip can be modified for use with roots from other plant species by adapting the chamber geometry and facilitates the systematic analysis of root growth and metabolism from multiple seedlings, paving the way for large-scale phenotyping of root metabolism and signaling.

  12. The root endophyte fungus Piriformospora indica leads to early flowering, higher biomass and altered secondary metabolites of the medicinal plant, Coleus forskohlii

    PubMed Central

    Das, Aparajita; Kamal, Shwet; Shakil, Najam Akhtar; Sherameti, Irena; Oelmüller, Ralf; Dua, Meenakshi; Tuteja, Narendra; Johri, Atul Kumar; Varma, Ajit

    2012-01-01

    This study was undertaken to investigate the influence of plant probiotic fungus Piriformospora indica on the medicinal plant C. forskohlii. Interaction of the C. forskohlii with the root endophyte P. indica under field conditions, results in an overall increase in aerial biomass, chlorophyll contents and phosphorus acquisition. The fungus also promoted inflorescence development, consequently the amount of p-cymene in the inflorescence increased. Growth of the root thickness was reduced in P. indica treated plants as they became fibrous, but developed more lateral roots. Because of the smaller root biomass, the content of forskolin was decreased. The symbiotic interaction of C. forskohlii with P. indica under field conditions promoted biomass production of the aerial parts of the plant including flower development. The plant aerial parts are important source of metabolites for medicinal application. Therefore we suggest that the use of the root endophyte fungus P. indica in sustainable agriculture will enhance the medicinally important chemical production. PMID:22301976

  13. Functional biology of plant phosphate uptake at root and mycorrhiza interfaces.

    PubMed

    Bucher, Marcel

    2007-01-01

    Phosphorus (P) is an essential plant nutrient and one of the most limiting in natural habitats as well as in agricultural production world-wide. The control of P acquisition efficiency and its subsequent uptake and translocation in vascular plants is complex. The physiological role of key cellular structures in plant P uptake and underlying molecular mechanisms are discussed in this review, with emphasis on phosphate transport across the cellular membrane at the root and arbuscular-mycorrhizal (AM) interfaces. The tools of molecular genetics have facilitated novel approaches and provided one of the major driving forces in the investigation of the basic transport mechanisms underlying plant P nutrition. Genetic engineering holds the potential to modify the system in a targeted way at the root-soil or AM symbiotic interface. Such approaches should assist in the breeding of crop plants that exhibit improved P acquisition efficiency and thus require lower inputs of P fertilizer for optimal growth. Whether engineering of P transport systems can contribute to enhanced P uptake will be discussed.

  14. Microbial Population and Community Dynamics on Plant Roots and Their Feedbacks on Plant Communities

    PubMed Central

    Bever, James D.; Platt, Thomas G.; Morton, Elise R.

    2012-01-01

    The composition of the soil microbial community can be altered dramatically due to association with individual plant species, and these effects on the microbial community can have important feedbacks on plant ecology. Negative plant-soil feedback plays primary roles in maintaining plant community diversity, whereas positive plant-soil feedback may cause community conversion. Host-specific differentiation of the microbial community results from the trade-offs associated with overcoming plant defense and the specific benefits associated with plant rewards. Accumulation of host-specific pathogens likely generates negative feedback on the plant, while changes in the density of microbial mutualists likely generate positive feedback. However, the competitive dynamics among microbes depends on the multidimensional costs of virulence and mutualism, the fine-scale spatial structure within plant roots, and active plant allocation and localized defense. Because of this, incorporating a full view of microbial dynamics is essential to explaining the dynamics of plant-soil feedbacks and therefore plant community ecology. PMID:22726216

  15. Microbial population and community dynamics on plant roots and their feedbacks on plant communities.

    PubMed

    Bever, James D; Platt, Thomas G; Morton, Elise R

    2012-01-01

    The composition of the soil microbial community can be altered dramatically due to association with individual plant species, and these effects on the microbial community can have important feedbacks on plant ecology. Negative plant-soil feedback plays primary roles in maintaining plant community diversity, whereas positive plant-soil feedback may cause community conversion. Host-specific differentiation of the microbial community results from the trade-offs associated with overcoming plant defense and the specific benefits associated with plant rewards. Accumulation of host-specific pathogens likely generates negative feedback on the plant, while changes in the density of microbial mutualists likely generate positive feedback. However, the competitive dynamics among microbes depends on the multidimensional costs of virulence and mutualism, the fine-scale spatial structure within plant roots, and active plant allocation and localized defense. Because of this, incorporating a full view of microbial dynamics is essential to explaining the dynamics of plant-soil feedbacks and therefore plant community ecology.

  16. Plant roots and spectroscopic methods – analyzing species, biomass and vitality

    PubMed Central

    Rewald, Boris; Meinen, Catharina

    2013-01-01

    In order to understand plant functioning, plant community composition, and terrestrial biogeochemistry, it is decisive to study standing root biomass, (fine) root dynamics, and interactions belowground. While most plant taxa can be identified by visual criteria aboveground, roots show less distinctive features. Furthermore, root systems of neighboring plants are rarely spatially segregated; thus, most soil horizons and samples hold roots of more than one species necessitating root sorting according to taxa. In the last decades, various approaches, ranging from anatomical and morphological analyses to differences in chemical composition and DNA sequencing were applied to discern species’ identity and biomass belowground. Among those methods, a variety of spectroscopic methods was used to detect differences in the chemical composition of roots. In this review, spectroscopic methods used to study root systems of herbaceous and woody species in excised samples or in situ will be discussed. In detail, techniques will be reviewed according to their usability to discern root taxa, to determine root vitality, and to quantify root biomass non-destructively or in soil cores holding mixtures of plant roots. In addition, spectroscopic methods which may be able to play an increasing role in future studies on root biomass and related traits are highlighted. PMID:24130565

  17. Tracing Plant Defense Responses in Roots upon MAMP/DAMP Treatment.

    PubMed

    Hiruma, Kei; Saijo, Yusuke

    2016-01-01

    This chapter describes how to apply microbe-associated molecular pattern (MAMP) or damage-associated molecular pattern (DAMP) solutions to Arabidopsis roots to trace defense responses in the root. Plants sense the presence of microbes via the perception of MAMPs or DAMPs by surface-localized pattern recognition receptors. The mechanisms governing plant root immunity are poorly characterized compared with those underlying plant immunity in the leaf, despite the fact that plant roots constantly interact with countless microbes living in soils that carry potential MAMPs and could stimulate the production of plant-derived DAMPs during colonization. To understand how a plant root immune system detects and reacts to the potential sources of a stimulus, we describe a simple method to monitor activation of root immunity upon MAMP/DAMP treatment by measuring relative expression of defense-related genes by RT-qPCR.

  18. 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

  19. Mesoscopic aspects of root water uptake modeling - Hydraulic resistances and root geometry interpretations in plant transpiration analysis

    NASA Astrophysics Data System (ADS)

    Vogel, Tomas; Votrubova, Jana; Dusek, Jaromir; Dohnal, Michal

    2016-02-01

    In the context of soil water flow modeling, root water uptake is often evaluated based on water potential difference between the soil and the plant (the water potential gradient approach). Root water uptake rate is modulated by hydraulic resistance of both the root itself, and the soil in the root vicinity. The soil hydraulic resistance is a function of actual soil water content and can be assessed assuming radial axisymmetric water flow toward a single root (at the mesoscopic scale). In the present study, three approximate solutions of mesoscopic root water uptake - finite difference approximation, steady-state solution, and steady-rate solution - are examined regarding their ability to capture the pressure head variations in the root vicinity. Insignificance of their differences when implemented in the macroscopic soil water flow model is demonstrated using the critical root water uptake concept. Subsequently, macroscopic simulations of coupled soil water flow and root water uptake are presented for a forest site under temperate humid climate. Predicted soil water pressure heads and actual transpiration rates are compared with observed data. Scenario simulations illustrate uncertainties associated with estimates of root geometrical and hydraulic properties. Regarding the actual transpiration prediction, the correct characterization of active root system geometry and hydraulic properties seems far more important than the choice of a particular mesoscopic model.

  20. Soybean NAC transcription factors promote abiotic stress tolerance and lateral root formation in transgenic plants.

    PubMed

    Hao, Yu-Jun; Wei, Wei; Song, Qing-Xin; Chen, Hao-Wei; Zhang, Yu-Qin; Wang, Fang; Zou, Hong-Feng; Lei, Gang; Tian, Ai-Guo; Zhang, Wan-Ke; Ma, Biao; Zhang, Jin-Song; Chen, Shou-Yi

    2011-10-01

    NAC transcription factors play important roles in plant growth, development and stress responses. Previously, we identified multiple NAC genes in soybean (Glycine max). Here, we identify the roles of two genes, GmNAC11 and GmNAC20, in stress responses and other processes. The two genes were differentially induced by multiple abiotic stresses and plant hormones, and their transcripts were abundant in roots and cotyledons. Both genes encoded proteins that localized to the nucleus and bound to the core DNA sequence CGT[G/A]. In the protoplast assay system, GmNAC11 acts as a transcriptional activator, whereas GmNAC20 functions as a mild repressor; however, the C-terminal end of GmANC20 has transcriptional activation activity. Over-expression of GmNAC20 enhances salt and freezing tolerance in transgenic Arabidopsis plants; however, GmNAC11 over-expression only improves salt tolerance. Over-expression of GmNAC20 also promotes lateral root formation. GmNAC20 may regulate stress tolerance through activation of the DREB/CBF-COR pathway, and may control lateral root development by altering auxin signaling-related genes. GmNAC11 probably regulates DREB1A and other stress-related genes. The roles of the two GmNAC genes in stress tolerance were further analyzed in soybean transgenic hairy roots. These results provide a basis for genetic manipulation to improve the agronomic traits of important crops. © 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.

  1. Fate of polycyclic aromatic hydrocarbons in plant-soil systems: Plant responses to a chemical stress in the root zone

    SciTech Connect

    Hoylman, A.M.

    1993-01-01

    Plant uptake and translocation of polycyclic aromatic hydrocarbons (PAHs) from soil was investigated to explore plant-microbial interactions in response to a chemical stress in the root zone. Plant uptake of individual PAHs was examined under laboratory conditions which maximized root exposure. White sweetclover, Melilotus alba, was grown in soils dosed with [sup 14]C-naphthalene, -phenanthrene, -pyrene, and -fluoranthene. The highest [sup 14]C concentrations were associated with roots, with decreasing concentrations observed in stems and leaves; however, the greatest percentage of recoverable [sup 14]C remained in the soil ([ge]86%) for all four PAHs. No evidence of bioaccumulation of the individual PAHs was found in M. alba over a 5-day exposure period. Root uptake and translocation of PAHs from soil to aboveground plant tissues proved to be a limited mechanism for PAH transport into terrestrial food chains. However, root surface sorption of PAHs may be important for plants in soils containing elevated concentrations of PAHs. Consequently, the root-soil interface may be important for plant-microbial interactions in response to a chemical stress. [sup 14]CO[sub 2] pulse-labeling studies provide evidence of a shift in [sup 14]C-allocation from aboveground tissue to the root zone when plants were exposed simultaneously to phenanthrene in soil. In addition, soil respiration and heterotrophic plate counts of rhizosphere microorganisms increased in plants exposed to phenanthrene as compared to controls. This study demonstrates the importance of the root-soil interface for plants growing in PAH contaminated soil and provides supportive evidence for a plant-microbial defense response to chemical toxicants in the root zone. Lipophilic toxicants in soils may reach high concentrations in the root zone, but rhizosphere microbial communities under the influence of the plant may reduce the amount of the compound that is actually taken up by the root.

  2. A novel interaction between plant-beneficial rhizobacteria and roots: colonization induces corn resistance against the root herbivore Diabrotica speciosa.

    PubMed

    Santos, Franciele; Peñaflor, Maria Fernanda G V; Paré, Paul W; Sanches, Patrícia A; Kamiya, Aline C; Tonelli, Mateus; Nardi, Cristiane; Bento, José Mauricio S

    2014-01-01

    A number of soil-borne microorganisms, such as mycorrhizal fungi and rhizobacteria, establish mutualistic interactions with plants, which can indirectly affect other organisms. Knowledge of the plant-mediated effects of mutualistic microorganisms is limited to aboveground insects, whereas there is little understanding of what role beneficial soil bacteria may play in plant defense against root herbivory. Here, we establish that colonization by the beneficial rhizobacterium Azospirillum brasilense affects the host selection and performance of the insect Diabrotica speciosa. Root larvae preferentially orient toward the roots of non-inoculated plants versus inoculated roots and gain less weight when feeding on inoculated plants. As inoculation by A. brasilense induces higher emissions of (E)-β-caryophyllene compared with non-inoculated plants, it is plausible that the non-preference of D. speciosa for inoculated plants is related to this sesquiterpene, which is well known to mediate belowground insect-plant interactions. To the best of our knowledge, this is the first study showing that a beneficial rhizobacterium inoculant indirectly alters belowground plant-insect interactions. The role of A. brasilense as part of an integrative pest management (IPM) program for the protection of corn against the South American corn rootworm, D. speciosa, is considered.

  3. A Novel Interaction between Plant-Beneficial Rhizobacteria and Roots: Colonization Induces Corn Resistance against the Root Herbivore Diabrotica speciosa

    PubMed Central

    Santos, Franciele; Peñaflor, Maria Fernanda G. V.; Paré, Paul W.; Sanches, Patrícia A.; Kamiya, Aline C.; Tonelli, Mateus; Nardi, Cristiane; Bento, José Mauricio S.

    2014-01-01

    A number of soil-borne microorganisms, such as mycorrhizal fungi and rhizobacteria, establish mutualistic interactions with plants, which can indirectly affect other organisms. Knowledge of the plant-mediated effects of mutualistic microorganisms is limited to aboveground insects, whereas there is little understanding of what role beneficial soil bacteria may play in plant defense against root herbivory. Here, we establish that colonization by the beneficial rhizobacterium Azospirillum brasilense affects the host selection and performance of the insect Diabrotica speciosa. Root larvae preferentially orient toward the roots of non-inoculated plants versus inoculated roots and gain less weight when feeding on inoculated plants. As inoculation by A. brasilense induces higher emissions of (E)-β-caryophyllene compared with non-inoculated plants, it is plausible that the non-preference of D. speciosa for inoculated plants is related to this sesquiterpene, which is well known to mediate belowground insect-plant interactions. To the best of our knowledge, this is the first study showing that a beneficial rhizobacterium inoculant indirectly alters belowground plant-insect interactions. The role of A. brasilense as part of an integrative pest management (IPM) program for the protection of corn against the South American corn rootworm, D. speciosa, is considered. PMID:25405495

  4. Plant and root endophyte assembly history: interactive effects on native and exotic plants.

    PubMed

    Sikes, Benjamin A; Hawkes, Christine V; Fukami, Tadashi

    2016-02-01

    Differences in the arrival timing of plants and soil biota may result in different plant communities through priority effects, potentially affecting the success of native vs. exotic plants, but experimental evidence is largely lacking. We conducted a greenhouse experiment to investigate whether the assembly history of plants and fungal root endophytes could interact to influence plant emergence and biomass. We introduced a grass species and eight fungal species from one of three land-use types (undisturbed, disturbed, or pasture sites in a Florida scrubland) in factorial combinations. We then introduced all plants and fungi from the other land-use types 2 weeks later. Plant emergence was monitored for 6 months, and final plant biomass and fungal species composition assessed. The emergence and growth of the exotic Melinis repens and the native Schizacharyium niveum were affected negatively when introduced early with their "home" fungi, but early introduction of a different plant species or fungi from a different site type eliminated these negative effects, providing evidence for interactive priority effects. Interactive effects of plant and fungal arrival history may be an overlooked determinant of plant community structure and may provide an effective management tool to inhibit biological invasion and aid ecosystem restoration.

  5. Rhizosphere engineering: Enhancing sustainable plant ecosystem productivity

    DOE PAGES

    Ahkami, Amir H.; White, III, Richard Allen; Handakumbura, Pubudu P.; ...

    2017-04-21

    Here, the rhizosphere is arguably the most complex microbial habitat on earth, comprising an integrated network of plant roots, soil and a diverse microbial consortium of bacteria, archaea, viruses, and microeukaryotes. Understanding, predicting and controlling the structure and function of the rhizosphere will allow us to harness plant-microbe interactions and other rhizosphere activities as a means to increase or restore plant ecosystem productivity, improve plant responses to a wide range of environmental perturbations, and mitigate effects of climate change by designing ecosystems for long-term soil carbon storage. Here, we review critical knowledge gaps in rhizosphere science, and how mechanistic understandingmore » of rhizosphere interactions can be leveraged in rhizosphere engineering efforts with the goal of maintaining sustainable plant ecosystem services for food and bioenergy production in an ever changing global climate.« less

  6. Rhizosphere engineering: Enhancing sustainable plant ecosystem productivity

    DOE PAGES

    Ahkami, Amir H.; White, III, Richard Allen; Handakumbura, Pubudu P.; ...

    2017-04-21

    The rhizosphere is arguably the most complex microbial habitat on earth, comprising an integrated network of plant roots, the soil and a diverse microbial consortium of bacteria, archaea, viruses, and microeukaryotes. Understanding, predicting and controlling the structure and function of the rhizosphere will allow us to harness plant-microbe interactions and other rhizosphere activities as a means to increase plant ecosystem productivity, improve plant responses to a wide range of environmental perturbations, and mitigate effects of climate change by designing ecosystems for long-term soil carbon storage. Furthermore, we review critical knowledge gaps in rhizosphere science, and how mechanistic understanding of rhizospheremore » interactions can be leveraged in rhizosphere engineering efforts with the goal of maintaining sustainable plant ecosystem services for food and bioenergy production in an ever changing global climate.« less

  7. The enl mutants enhance the lrx1 root hair mutant phenotype of Arabidopsis thaliana.

    PubMed

    Diet, Anouck; Brunner, Susanne; Ringli, Christoph

    2004-06-01

    The development of root hairs serves as an excellent model to study cell growth using both cytological and genetic approaches. In the past, we have characterized LRX1, an extracellular protein of Arabidopsis consisting of an LRR-domain and a structural extensin domain. LRX1 is specifically expressed in root hairs and lrx1 mutants show severe deficiencies in root hair development. In this work, we describe the characterization of enl (enhancer of lrx1) mutants that were isolated in a visual screen of an ethylmethanesulfonate -mutagenized lrx1 line for plants exhibiting an enhanced lrx1 phenotype. Four recessive enl mutants were analyzed, three of which define new genetic loci involved in root hair development. The mutations at the enl loci and lrx1 result in additive phenotypes in enl/lrx1 double mutants. One enl mutant is affected in the ACTIN2 gene and encodes a protein with a 22 amino acid deletion at the C-terminus. The comparison of molecular and phenotypic data of different actin2 alleles suggests that the truncated ACTIN2 protein is still partially functional.

  8. Roots under attack: contrasting plant responses to below- and aboveground insect herbivory.

    PubMed

    Johnson, Scott N; Erb, Matthias; Hartley, Susan E

    2016-04-01

    The distinctive ecology of root herbivores, the complexity and diversity of root-microbe interactions, and the physical nature of the soil matrix mean that plant responses to root herbivory extrapolate poorly from our understanding of responses to aboveground herbivores. For example, root attack induces different changes in phytohormones to those in damaged leaves, including a lower but more potent burst of jasmonates in several plant species. Root secondary metabolite responses also differ markedly, although patterns between roots and shoots are harder to discern. Root defences must therefore be investigated in their own ecophysiological and evolutionary context, specifically one which incorporates root microbial symbionts and antagonists, if we are to better understand the battle between plants and their hidden herbivores.

  9. Arguments for and against self and non-self root recognition in plants.

    PubMed

    Depuydt, Stephen

    2014-01-01

    Root-root interaction research gained more and more attention over the past few years. Roots are pivotal for plant survival because they ensure uptake of water and nutrients. Therefore, detection of adjacent roots might lead to competitive advantages. Several lines of experimental evidence suggest that roots have ways to discriminate non-related roots, kin, and-importantly-that they can sense self/non-self roots to avoid intra-plant competition. In this mini-review, the existence of self/non-self recognition in plant roots will be discussed and the current knowledge on the mechanisms that could be involved will be summarized. Although the process of identity recognition is still not completely understood, interesting data are available and emerging new technologies will certainly aid to better understand this research field that can have an important biological, ecological, and agricultural impact.

  10. A novel life cycle arising from leaf segments in plants regenerated from horseradish hairy roots.

    PubMed

    Mano, Y; Matsuhashi, M

    1995-03-01

    Horseradish (Armoracia rusticana) hairy root clones were established from hairy roots which were transformed with the Ri plasmid in Agrobacterium rhizogenes 15834. The transformed plants, which were regenerated from hairy root clones, had thicker roots with extensive lateral branches and thicker stems, and grew faster compared with non-transformed horseradish plants. Small sections of leaves of the transformed plants generated adventitious roots in phytohormone-free G (modified Gamborg's) medium. Root proliferation was followed by adventitious shoot formation and plant regeneration. Approximately twenty plants were regenerated per square centimeter of leaf. The transformed plants were easily transferable from sterile conditions to soil. When leaf segments of the transformed plants were cultured in a liquid fertilizer under non-sterile conditions, adventitious roots were generated at the cut ends of the leaves. Adventitious shoots were generated at the boundary between the leaf and the adventitious roots and developed into complete plants. This novel life cycle arising from leaf segments is a unique property of the transformed plants derived from hairy root clones.

  11. Improvement of cadmium uptake and accumulation in Sedum alfredii by endophytic bacteria Sphingomonas SaMR12: effects on plant growth and root exudates.

    PubMed

    Chen, Bao; Zhang, Yibin; Rafiq, Muhammad Tariq; Khan, Kiran Yasmin; Pan, Fengshan; Yang, Xiaoe; Feng, Ying

    2014-12-01

    Inoculating endophytic bacteria was proven as a promising way to enhance phytoremediation. By a hydroponic experiment, the role of this study was to clarify the effects of inoculating endophytic bacterium Sphingomonas SaMR12 on phytoremediation, with special emphasis on changes of cadmium uptake, plant growth, root morphology, and organic acids secretion at different cadmium treated levels (0, 5, 50, and 100 μM). The results showed that SaMR12 inoculation improved the accumulation of cadmium as well as plant biomass, length of roots, number of root tips, and root surface area. Root secretion of oxalic, citric, and succinic acids was also increased after inoculated, which may alleviate the cadmium toxicity to plant or inhibit the rising trend of oxidative stress of plant. The major finding of this work suggested that in the root, SaMR12 improves cadmium bioavailability and absorption facility by increasing root-soil contact area and root organic acid secretion; and in the shoot, SaMR12 increases cadmium tolerance by alleviating oxidative stress of plant, so as to enhance the capability of cadmium extraction by plant.

  12. Enhanced glucosinolates in root exudates of Brassica rapa ssp. rapa mediated by salicylic acid and methyl jasmonate.

    PubMed

    Schreiner, Monika; Krumbein, Angelika; Knorr, Dietrich; Smetanska, Iryna

    2011-02-23

    Elicitation studies with salicylic acid (SA) and methyl jasmonate (MJ) inducing a targeted rhizosecretion of high levels of anticarcinogenic glucosinolates in Brassica rapa ssp. rapa plants were conducted. Elicitor applications not only led to an accumulation of individual indole glucosinolates and the aromatic 2-phenylethyl glucosinolate in the turnip organs but also in turnip root exudates. This indicates an extended systemic response, which comprises the phyllosphere with all aboveground plant organs and the rhizosphere including the belowground root system and also root exudates. Both elicitor applications induced a doubling in 2-phenylethyl glucosinolate in root exudates, whereas application of MJ enhanced rhizosecreted indole glucosinolates up to 4-fold. In addition, the time course study revealed that maximal elicitation was observed on the 10th day of SA and MJ treatment. This study may provide an essential contribution using these glucosinolates as bioactive additives in functional foods and nutraceuticals.

  13. Growth, nitrogen uptake and flow in maize plants affected by root growth restriction.

    PubMed

    Xu, Liangzheng; Niu, Junfang; Li, Chunjian; Zhang, Fusuo

    2009-07-01

    The objective of the present study was to investigate the influence of a reduced maize root-system size on root growth and nitrogen (N) uptake and flow within plants. Restriction of shoot-borne root growth caused a strong decrease in the absorption of root: shoot dry weight ratio and a reduction in shoot growth. On the other hand, compensatory growth and an increased N uptake rate in the remaining roots were observed. Despite the limited long-distance transport pathway in the mesocotyl with restriction of shoot-borne root growth, N cycling within these plants was higher than those in control plants, implying that xylem and phloem flow velocities via the mesocotyl were considerably higher than in plants with an intact root system. The removal of the seminal roots in addition to restricting shoot-borne root development did not affect whole plant growth and N uptake, except for the stronger compensatory growth of the primary roots. Our results suggest that an adequate N supply to maize plant is maintained by compensatory growth of the remaining roots, increased N uptake rate and flow velocities within the xylem and phloem via the mesocotyl, and reduction in the shoot growth rate.

  14. Aquatic adventitious root development in partially and completely submerged wetland plants Cotula coronopifolia and Meionectes brownii.

    PubMed

    Rich, Sarah Meghan; Ludwig, Martha; Colmer, Timothy David

    2012-07-01

    A common response of wetland plants to flooding is the formation of aquatic adventitious roots. Observations of aquatic root growth are widespread; however, controlled studies of aquatic roots of terrestrial herbaceous species are scarce. Submergence tolerance and aquatic root growth and physiology were evaluated in two herbaceous, perennial wetland species Cotula coronopifolia and Meionectes brownii. Plants were raised in large pots with 'sediment' roots in nutrient solution and then placed into individual tanks and shoots were left in air or submerged (completely or partially). The effects on growth of aquatic root removal, and of light availability to submerged plant organs, were evaluated. Responses of aquatic root porosity, chlorophyll and underwater photosynthesis, were studied. Both species tolerated 4 weeks of complete or partial submergence. Extensive, photosynthetically active, aquatic adventitious roots grew from submerged stems and contributed up to 90 % of the total root dry mass. When aquatic roots were pruned, completely submerged plants grew less and had lower stem and leaf chlorophyll a, as compared with controls with intact roots. Roots exposed to the lowest PAR (daily mean 4.7 ± 2.4 µmol m(-2) s(-1)) under water contained less chlorophyll, but there was no difference in aquatic root biomass after 4 weeks, regardless of light availability in the water column (high PAR was available to all emergent shoots). Both M. brownii and C. coronopifolia responded to submergence with growth of aquatic adventitious roots, which essentially replaced the existing sediment root system. These aquatic roots contained chlorophyll and were photosynthetically active. Removal of aquatic roots had negative effects on plant growth during partial and complete submergence.

  15. Aquatic adventitious root development in partially and completely submerged wetland plants Cotula coronopifolia and Meionectes brownii

    PubMed Central

    Rich, Sarah Meghan; Ludwig, Martha; Colmer, Timothy David

    2012-01-01

    Background and Aims A common response of wetland plants to flooding is the formation of aquatic adventitious roots. Observations of aquatic root growth are widespread; however, controlled studies of aquatic roots of terrestrial herbaceous species are scarce. Submergence tolerance and aquatic root growth and physiology were evaluated in two herbaceous, perennial wetland species Cotula coronopifolia and Meionectes brownii. Methods Plants were raised in large pots with ‘sediment’ roots in nutrient solution and then placed into individual tanks and shoots were left in air or submerged (completely or partially). The effects on growth of aquatic root removal, and of light availability to submerged plant organs, were evaluated. Responses of aquatic root porosity, chlorophyll and underwater photosynthesis, were studied. Key Results Both species tolerated 4 weeks of complete or partial submergence. Extensive, photosynthetically active, aquatic adventitious roots grew from submerged stems and contributed up to 90 % of the total root dry mass. When aquatic roots were pruned, completely submerged plants grew less and had lower stem and leaf chlorophyll a, as compared with controls with intact roots. Roots exposed to the lowest PAR (daily mean 4·7 ± 2·4 µmol m−2 s−1) under water contained less chlorophyll, but there was no difference in aquatic root biomass after 4 weeks, regardless of light availability in the water column (high PAR was available to all emergent shoots). Conclusions Both M. brownii and C. coronopifolia responded to submergence with growth of aquatic adventitious roots, which essentially replaced the existing sediment root system. These aquatic roots contained chlorophyll and were photosynthetically active. Removal of aquatic roots had negative effects on plant growth during partial and complete submergence. PMID:22419759

  16. Deciphering composition and function of the root microbiome of a legume plant.

    PubMed

    Hartman, Kyle; van der Heijden, Marcel Ga; Roussely-Provent, Valexia; Walser, Jean-Claude; Schlaeppi, Klaus

    2017-01-17

    Diverse assemblages of microbes colonize plant roots and collectively function as a microbiome. Earlier work has characterized the root microbiomes of numerous plant species, but little information is available for legumes despite their key role in numerous ecosystems including agricultural systems. Legumes form a root nodule symbiosis with nitrogen-fixing Rhizobia bacteria and thereby account for large, natural nitrogen inputs into soils. Here, we describe the root bacteria microbiome of the legume Trifolium pratense combining culture-dependent and independent methods. For a functional understanding of individual microbiome members and their impact on plant growth, we began to inoculate root microbiome members alone or in combination to Trifolium roots. At a whole-root scale, Rhizobia bacteria accounted for ~70% of the root microbiome. Other enriched members included bacteria from the genera Pantoea, Sphingomonas, Novosphingobium, and Pelomonas. We built a reference stock of 200 bacteria isolates, and we found that they corresponded to ~20% of the abundant root microbiome members. We developed a microcosm system to conduct simplified microbiota inoculation experiments with plants. We observed that while an abundant root microbiome member reduced plant growth when inoculated alone, this negative effect was alleviated if this Flavobacterium was co-inoculated with other root microbiome members. The Trifolium root microbiome was dominated by nutrient-providing Rhizobia bacteria and enriched for bacteria from genera that may provide disease protection. First microbiota inoculation experiments indicated that individual community members can have plant growth compromising activities without being apparently pathogenic, and a more diverse root community can alleviate plant growth compromising activities of its individual members. A trait-based characterization of the reference stock bacteria will permit future microbiota manipulation experiments to decipher overall

  17. Where do roots take up water? Neutron radiography of water flow into the roots of transpiring plants growing in soil.

    PubMed

    Zarebanadkouki, Mohsen; Kim, Yangmin X; Carminati, Andrea

    2013-09-01

    Where and how fast does water flow from soil into roots? The answer to this question requires direct and in situ measurement of local flow of water into roots of transpiring plants growing in soil. We used neutron radiography to trace the transport of deuterated water (D₂O) in lupin (Lupinus albus) roots. Lupins were grown in aluminum containers (30 × 25 × 1 cm) filled with sandy soil. D₂O was injected in different soil regions and its transport in soil and roots was monitored by neutron radiography. The transport of water into roots was then quantified using a convection-diffusion model of D₂O transport into roots. The results showed that water uptake was not uniform along roots. Water uptake was higher in the upper soil layers than in the lower ones. Along an individual root, the radial flux was higher in the proximal segments than in the distal segments. In lupins, most of the water uptake occurred in lateral roots. The function of the taproot was to collect water from laterals and transport it to the shoot. This function is ensured by a low radial conductivity and a high axial conductivity. Lupin root architecture seems well designed to take up water from deep soil layers. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

  18. Leaf wounding or simulated herbivory in young N. attenuata plants reduces carbon delivery to roots and root tips.

    PubMed

    Schmidt, Lilian; Hummel, Grégoire M; Thiele, Björn; Schurr, Ulrich; Thorpe, Michael R

    2015-04-01

    In Nicotiana attenuata seedlings, simulated herbivo ry by the specialist Manduca sexta decreases root growth and partitioning of recent photoassimilates to roots in contrast to increased partitioning reported for older plants. Root elongation rate in Nicotiana attenuata has been shown to decrease after leaf herbivory, despite reports of an increased proportion of recently mobilized photoassimilate being delivered towards the root system in many species after similar treatments. To study this apparent contradiction, we measured the distribution of recent photoassimilate within root tissues after wounding or simulated herbivory of N. attenuata leaves. We found no contradiction: herbivory reduced carbon delivery to root tips. However, the speed of phloem transport in both shoot and root, and the delivery of recently assimilated carbon to the entire root system, declined after wounding or simulated herbivory, in contrast with the often-reported increase in root partitioning. We conclude that the herbivory response in N. attenuata seedlings is to favor the shoot and not bunker carbon in the root system.

  19. Belowground volatiles facilitate interactions between plant roots and soil organisms.

    PubMed

    Wenke, Katrin; Kai, Marco; Piechulla, Birgit

    2010-02-01

    Many interactions between organisms are based on the emission and perception of volatiles. The principle of using volatile metabolites as communication signals for chemo-attractant or repellent for species-specific interactions or mediators for cell-to-cell recognition does not stop at an apparently unsuitable or inappropriate environment. These infochemicals do not only diffuse through the atmosphere to process their actions aboveground, but belowground volatile interactions are similarly complex. This review summarizes various eucaryotes (e.g., plant (roots), invertebrates, fungi) and procaryotes (e.g., rhizobacteria) which are involved in these volatile-mediated interactions. The soil volatiles cannot be neglected anymore, but have to be considered in the future as valuable infochemicals to understand the entire integrity of the ecosystems.

  20. Elicitation Based Enhancement of Secondary Metabolites in Rauwolfia serpentina and Solanum khasianum Hairy Root Cultures

    PubMed Central

    Srivastava, Mrinalini; Sharma, Swati; Misra, Pratibha

    2016-01-01

    Background: Rauwolfia serpentina and Solanum khasianum are well-known medicinally important plants contained important alkaloids in their different parts. Elicitation of these alkaloids is important because of associated pharmaceutical properties. Targeted metabolites were ajmaline and ajmalicine in R. serpentina; solasodine and α-solanine in S. khasianum. Objective: Enhancement of secondary metabolites through biotic and abiotic elicitors in hairy root cultures of R. serpentina and S. khasianum. Materials and Methods: In this report, hairy root cultures of these two plants were established through Agrobacterium rhizogenes mediated transformation by optimizing various parameters as age of explants, duration of preculture, and co-cultivation period. NaCl was used as abiotic elicitors in these two plants. Cellulase from Aspergillus niger was used as biotic elicitor in S. khasianum and mannan from Saccharomyces cerevisiae was used in R. serpentina. Results: First time we have reported the effect of biotic and abiotic elicitors on the production of important metabolites in hairy root cultures of these two plants. Ajmalicine production was stimulated up to 14.8-fold at 100 mM concentration of NaCl after 1 week of treatment. Ajmaline concentration was also increased 2.9-fold at 100 mg/l dose of mannan after 1 week. Solasodine content was enhanced up to 4.0-fold and 3.6-fold at 100 mM and 200 mM NaCl, respectively, after 6 days of treatments. Conclusion: This study explored the potential of the elicitation strategy in A. rhizogenes transformed cell cultures and this potential further used for commercial production of these pharmaceutically important secondary metabolites. SUMMARY Hairy roots of Rauwolfia serpentina were subjected to salt (abiotic stress) and mannan (biotic stress) treatment for 1 week. Ajmaline and ajmalicine secondary metabolites were quantified before and after stress treatmentAjmalicine yield was enhanced up to 14.8-fold at 100 mM concentration of Na

  1. Root growth and hydraulic conductivity of southern pine seedlings in response to soil temperature and water availability after planting

    Treesearch

    Mary Anne Sword Sayer; John C. Brissette; James P. Barnett

    2005-01-01

    Comparison of the root system growth and water transport of southern pine species after planting in different root-zone environments is needed to guide decisions regarding when, and what species to plant. Evaluation of how seed source affects root system responses to soil conditions will allow seed sources to be matched to planting conditions. The root growth and...

  2. Evolutionary conservation of a core root microbiome across plant phyla along a tropical soil chronosequence.

    PubMed

    Yeoh, Yun Kit; Dennis, Paul G; Paungfoo-Lonhienne, Chanyarat; Weber, Lui; Brackin, Richard; Ragan, Mark A; Schmidt, Susanne; Hugenholtz, Philip

    2017-08-09

    Culture-independent molecular surveys of plant root microbiomes indicate that soil type generally has a stronger influence on microbial communities than host phylogeny. However, these studies have mostly focussed on model plants and crops. Here, we examine the root microbiomes of multiple plant phyla including lycopods, ferns, gymnosperms, and angiosperms across a soil chronosequence using 16S rRNA gene amplicon profiling. We confirm that soil type is the primary determinant of root-associated bacterial community composition, but also observe a significant correlation with plant phylogeny. A total of 47 bacterial genera are associated with roots relative to bulk soil microbial communities, including well-recognized plant-associated genera such as Bradyrhizobium, Rhizobium, and Burkholderia, and major uncharacterized lineages such as WPS-2, Ellin329, and FW68. We suggest that these taxa collectively constitute an evolutionarily conserved core root microbiome at this site. This lends support to the inference that a core root microbiome has evolved with terrestrial plants over their 400 million year history.Yeoh et al. study root microbiomes of different plant phyla across a tropical soil chronosequence. They confirm that soil type is the primary determinant of root-associated bacterial communities, but also observe a clear correlation with plant phylogeny and define a core root microbiome at this site.

  3. Root-zone temperature and water availability affect early root growth of planted longleaf pine

    Treesearch

    M.A. Sword

    1995-01-01

    Longleaf pine seedlings from three seed sources were exposed to three root-zone temperatures and three levels of water availability for 28 days. Root growth declined as temperature and water availability decreased. Root growth differed by seed source. Results suggest that subtle changes in the regeneration environment may influence early root growth of longleaf pine...

  4. Root Exudate-Induced Alterations in Bacillus cereus Cell Wall Contribute to Root Colonization and Plant Growth Promotion

    PubMed Central

    Dutta, Swarnalee; Rani, T. Swaroopa; Podile, Appa Rao

    2013-01-01

    The outcome of an interaction between plant growth promoting rhizobacteria and plants may depend on the chemical composition of root exudates (REs). We report the colonization of tobacco, and not groundnut, roots by a non-rhizospheric Bacillus cereus (MTCC 430). There was a differential alteration in the cell wall components of B. cereus in response to the REs from tobacco and groundnut. Attenuated total reflectance infrared spectroscopy revealed a split in amide I region of B. cereus cells exposed to tobacco-root exudates (TRE), compared to those exposed to groundnut-root exudates (GRE). In addition, changes in exopolysaccharides and lipid-packing were observed in B. cereus grown in TRE-amended minimal media that were not detectable in GRE-amended media. Cell-wall proteome analyses revealed upregulation of oxidative stress-related alkyl hydroperoxide reductase, and DNA-protecting protein chain (Dlp-2), in response to GRE and TRE, respectively. Metabolism-related enzymes like 2-amino-3-ketobutyrate coenzyme A ligase and 2-methylcitrate dehydratase and a 60 kDa chaperonin were up-regulated in response to TRE and GRE. In response to B. cereus, the plant roots altered their exudate-chemodiversity with respect to carbohydrates, organic acids, alkanes, and polyols. TRE-induced changes in surface components of B. cereus may contribute to successful root colonization and subsequent plant growth promotion. PMID:24205213

  5. Root and bacterial secretions regulate the interaction between plants and PGPR leading to distinct plant growth promotion effects

    USDA-ARS?s Scientific Manuscript database

    Plant growth-promoting rhizobacteria (PGPR) have garnered interest in agriculture due to their ability to influence the growth and production of host plants. ATP-binding cassette (ABC) transporters play important roles in plant-microbe interactions by modulating plant root exudation. The present stu...

  6. Bacillus pumilus ES4: candidate plant growth-promoting bacterium to enhance establishment of plants in mine tailings

    PubMed Central

    de-Bashan, Luz E.; Hernandez, Juan-Pablo; Bashan, Yoav; Maier, Raina

    2014-01-01

    Three plant growth-promoting bacteria (PGPB; Bacillus pumilus ES4, B. pumilus RIZO1, and Azospirillum brasilense Cd) were tested for their ability to enhance plant growth and development of the native Sonoran Desert shrub quailbush (Atriplex lentiformis) and for their effect on the native bacterial community in moderately acidic, high-metal content (AHMT) and in neutral, low metal content natural tailings (NLMT) in controlled greenhouse experiments. Inoculation of quailbush with all three PGPB significantly enhanced plant growth parameters, such as germination, root length, dry weight of shoots and roots, and root/shoot ratio in both types of tailings. The effect of inoculation on the indigenous bacterial community by the most successful PGPB Bacillus pumilus ES4 was evaluated by denaturating gradient gel electrophoresis (PCR-DGGE) fingerprinting and root colonization was followed by specific fluorescent in situ hybridization (FISH). Inoculation with this strain significantly changed the bacterial community over a period of 60 days. FISH analysis showed that the preferred site of colonization was the root tips and root elongation area. This study shows that inoculation of native perennial plants with PGPB can be used for developing technologies for phytostabilizing mine tailings. PMID:25009362

  7. Bacillus pumilus ES4: candidate plant growth-promoting bacterium to enhance establishment of plants in mine tailings.

    PubMed

    de-Bashan, Luz E; Hernandez, Juan-Pablo; Bashan, Yoav; Maier, Raina

    2010-12-01

    Three plant growth-promoting bacteria (PGPB; Bacillus pumilus ES4, B. pumilus RIZO1, and Azospirillum brasilense Cd) were tested for their ability to enhance plant growth and development of the native Sonoran Desert shrub quailbush (Atriplex lentiformis) and for their effect on the native bacterial community in moderately acidic, high-metal content (AHMT) and in neutral, low metal content natural tailings (NLMT) in controlled greenhouse experiments. Inoculation of quailbush with all three PGPB significantly enhanced plant growth parameters, such as germination, root length, dry weight of shoots and roots, and root/shoot ratio in both types of tailings. The effect of inoculation on the indigenous bacterial community by the most successful PGPB Bacillus pumilus ES4 was evaluated by denaturating gradient gel electrophoresis (PCR-DGGE) fingerprinting and root colonization was followed by specific fluorescent in situ hybridization (FISH). Inoculation with this strain significantly changed the bacterial community over a period of 60 days. FISH analysis showed that the preferred site of colonization was the root tips and root elongation area. This study shows that inoculation of native perennial plants with PGPB can be used for developing technologies for phytostabilizing mine tailings.

  8. Electric Current Precedes Emergence of a Lateral Root in Higher Plants

    PubMed Central

    Hamada, Shingo; Ezaki, Shu; Hayashi, Kenshi; Toko, Kiyoshi; Yamafuji, Kaoru

    1992-01-01

    Stable electrochemical patterns appear spontaneously around roots of higher plants and are closely related to growth. An electric potential pattern accompanied by lateral root emergence was measured along the surface of the primary root of adzuki bean (Phaseolus angularis) over 21 h using a microelectrode manipulated by a newly developed apparatus. The electric potential became lower at the point where a lateral root emerged. This change preceded the emergence of the lateral root by about 10 h. A theory is presented for calculating two-dimensional patterns of electric potential and electric current density around the primary root (and a lateral root) using only data on the one-dimensional electric potential measured near the surface of the primary root. The development of the lateral root inside the primary root is associated with the influx of electric current of about 0.7 μA·cm−2 at the surface. Images Figure 7 PMID:16653036

  9. Artemisinin production by plant hairy root cultures in gas- and liquid-phase bioreactors.

    PubMed

    Patra, Nivedita; Srivastava, Ashok K

    2016-01-01

    Alternative biotechnological protocol for large-scale artemisinin production was established. It featured enhanced growth and artemisinin production by cultivation of hairy roots in nutrient mist bioreactor (NMB) coupled with novel cultivation strategies. Artemisinin is used for the treatment of cerebral malaria. Presently, its main source is from seasonal plant Artemisia annua. This study featured investigation of growth and artemisinin production by A. annua hairy roots (induced by Agrobacterium rhizogenes-mediated genetic transformation of explants) in three bioreactor configurations-bubble column reactor, NMB and modified NMB particularly to establish their suitability for commercial production. It was observed that cultivation of hairy roots in a non-stirred bubble column reactor exhibited a biomass accumulation of 5.68 g/l only while batch cultivation in a custom-made NMB exhibited a higher biomass concentration of 8.52 g/l but relatively lower artemisinin accumulation of 0.22 mg/g was observed in this reactor. A mixture of submerged liquid-phase growth (for 5 days) followed by gas-phase cultivation in nutrient mist reactor operation strategy (for next 15 days) was adopted for hairy root cultivation in this investigation. Reasonably, high (23.02 g/l) final dry weight along with the artemisinin accumulation (1.12 mg/g, equivalent to 25.78 mg/l artemisinin) was obtained in this bioreactor, which is the highest reported artemisinin yield in the gas-phase NMB cultivation.

  10. High root temperature affects the tolerance to high light intensity in Spathiphyllum plants.

    PubMed

    Soto, Adriana; Hernández, Laura; Quiles, María José

    2014-10-01

    Spathiphyllum wallisii plants were sensitive to temperature stress under high illumination, although the susceptibility of leaves to stress may be modified by root temperature. Leaves showed higher tolerance to high illumination, in both cold and heat conditions, when the roots were cooled, probably because the chloroplast were protected by excess excitation energy dissipation mechanisms such as cyclic electron transport. When the roots were cooled both the activity of electron donation by NADPH and ferredoxin to plastoquinone and the amount of PGR5 polypeptide, an essential component of cyclic electron flow around PSI, increased. However, when the stems were heated or cooled under high illumination, but the roots were heated, the quantum yield of PSII decreased considerably and neither the electron donation activity by NADPH and ferredoxin to plastoquinone nor the amount of PGR5 polypeptide increased. In such conditions, the cyclic electron flow cannot be enhanced by high light and PSII is damaged as a result of insufficient dissipation of excess light energy. Additionally, the damage to PSII induced the increase in both chlororespiratory enzymes, NDH complex and PTOX. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  11. RGB and Spectral Root Imaging for Plant Phenotyping and Physiological Research: Experimental Setup and Imaging Protocols.

    PubMed

    Bodner, Gernot; Alsalem, Mouhannad; Nakhforoosh, Alireza; Arnold, Thomas; Leitner, Daniel

    2017-08-08

    Better understanding of plant root dynamics is essential to improve resource use efficiency of agricultural systems and increase the resistance of crop cultivars against environmental stresses. An experimental protocol is presented for RGB and hyperspectral imaging of root systems. The approach uses rhizoboxes where plants grow in natural soil over a longer time to observe fully developed root systems. Experimental settings are exemplified for assessing rhizobox plants under water stress and studying the role of roots. An RGB imaging setup is described for cheap and quick quantification of root development over time. Hyperspectral imaging improves root segmentation from the soil background compared to RGB color based thresholding. The particular strength of hyperspectral imaging is the acquisition of chemometric information on the root-soil system for functional understanding. This is demonstrated with high resolution water content mapping. Spectral imaging however is more complex in image acquisition, processing and analysis compared to the RGB approach. A combination of both methods can optimize a comprehensive assessment of the root system. Application examples integrating root and aboveground traits are given for the context of plant phenotyping and plant physiological research. Further improvement of root imaging can be obtained by optimizing RGB image quality with better illumination using different light sources and by extension of image analysis methods to infer on root zone properties from spectral data.

  12. Volatile oils from the plant and hairy root cultures of Ageratum conyzoides L.

    PubMed

    Abdelkader, Mohamed Salaheldin A; Lockwood, George B

    2011-05-01

    Two lines of hairy root culture of Ageratum conyzoides L. induced by Agrobacterium rhizogenes ATCC 15834 were established under either complete darkness or 16 h light/8 h dark photoperiod conditions. The volatile oil yields from aerial parts and roots of the parent plant, the hairy root culture photoperiod line and the hairy root culture dark line were 0.2%, 0.08%, 0.03% and 0.02%, (w/w), respectively. The compositions of the volatiles from the hairy roots, plant roots and aerial parts were analysed by GC and GC-MS. The main components of the volatiles from the hairy root cultures were β-farnesene, precocene I and β-caryophyllene, in different amounts, depending on light conditions and also on the age of cultures. Precocene I, β-farnesene, precocene II and β-caryophyllene were the main constituents of the volatile oils from the parent plant roots, whereas precocene I, germacrene D, β-caryophyllene and precocene II were the main constituents of the aerial parts of the parent plant. Growth and time-course studies of volatile constituents of the two hairy root lines were compared. Qualitative and quantitative differences were found between the volatile oils from the roots of the parent plant and those from the hairy roots.

  13. A fungal endophyte helps plants to tolerate root herbivory through changes in gibberellin and jasmonate signaling.

    PubMed

    Cosme, Marco; Lu, Jing; Erb, Matthias; Stout, Michael Joseph; Franken, Philipp; Wurst, Susanne

    2016-08-01

    Plant-microbe mutualisms can improve plant defense, but the impact of root endophytes on below-ground herbivore interactions remains unknown. We investigated the effects of the root endophyte Piriformospora indica on interactions between rice (Oryza sativa) plants and its root herbivore rice water weevil (RWW; Lissorhoptrus oryzophilus), and how plant jasmonic acid (JA) and GA regulate this tripartite interaction. Glasshouse experiments with wild-type rice and coi1-18 and Eui1-OX mutants combined with nutrient, jasmonate and gene expression analyses were used to test: whether RWW adult herbivory above ground influences subsequent damage caused by larval herbivory below ground; whether P. indica protects plants against RWW; and whether GA and JA signaling mediate these interactions. The endophyte induced plant tolerance to root herbivory. RWW adults and larvae acted synergistically via JA signaling to reduce root growth, while endophyte-elicited GA biosynthesis suppressed the herbivore-induced JA in roots and recovered plant growth. Our study shows for the first time the impact of a root endophyte on plant defense against below-ground herbivores, adds to growing evidence that induced tolerance may be an important root defense, and implicates GA as a signal component of inducible plant tolerance against biotic stress.

  14. The Influence of Plant Root Systems on Subsurface Flow: Implications for Slope Stability

    EPA Science Inventory

    Although research has explained how plant roots mechanically stabilize soils, in this article we explore how root systems create networks of preferential flow and thus influence water pressures in soils to trigger landslides. Root systems may alter subsurface flow: Hydrological m...

  15. Bioremediation of phenolic compounds from water with plant root surface peroxidases

    SciTech Connect

    Adler, P.R.; Arora, R.; El Ghaouth, A.

    1994-09-01

    Peroxidases have been shown to polymerize phenolic compounds, thereby removing them from solution by precipitation. Others have studied the role of root surface associated peroxidases as a defense against fungal root pathogens; however, their use in detoxification of organic pollutants in vivo at the root surface has not been studied. Two plant species, waterhyacinth [Eichhornia crassipes (C. Mart) Solms-Laub.] and tomato (Lycopersicon esculentum L.), were tested for both in vitro and in vivo peroxidase activity on the root surface. In vitro studies indicated that root surface peroxidase activities were 181 and 78 nmol tetraguaiacol formed min{sup -1} g{sup -1} root fresh wt., for tomato and waterhyacinth, respectively. Light microscope studies revealed that guaiacol was polymerized in vivo at the root surface. Although peroxidase was evenly distributed on tomato roots, it was distributed patchily on waterhyacinth roots. In vitro studies using gas chromatography-mass spectrometry (GC-MS) showed that the efficiency of peroxidase to polymerize phenols vary with phenolic compound. We suggest that plants may be utilized as a source of peroxidases for removal of phenolic compounds that are on the EPA priority pollutant list and that root surface peroxidases may minimize the absorption of phenolic compounds into plants by precipitating them at the root surface. In this study we have identified a new use for root-associated proteins in ecologically engineering plant systems for bioremediation of phenolic compounds in the soil and water environment. 25 refs., 2 figs., 2 tabs.

  16. The Influence of Plant Root Systems on Subsurface Flow: Implications for Slope Stability

    EPA Science Inventory

    Although research has explained how plant roots mechanically stabilize soils, in this article we explore how root systems create networks of preferential flow and thus influence water pressures in soils to trigger landslides. Root systems may alter subsurface flow: Hydrological m...

  17. Overexpression of hns in the plant growth-promoting bacterium Enterobacter cloacae UW5 increases root colonization.

    PubMed

    English, M M; Coulson, T J D; Horsman, S R; Patten, C L

    2010-06-01

    Plant growth-promoting rhizobacteria (PGPR) introduced into soil often do not compete effectively with indigenous micro-organisms for plant colonization. The aim of this study was to identify novel genes that are important for root colonization by the PGPR Enterobacter cloacae UW5. A library of transposon mutants of Ent. cloacae UW5 was screened for mutants with altered ability to colonize canola roots using a thermal asymmetric interlaced (TAIL)-PCR-based approach. A PCR fragment from one mutant was reproducibly amplified at greater levels from genomic DNA extracted from mutant pools recovered from seedling roots 6 days after seed inoculation compared to that from the cognate inoculum cultures. Competition assays confirmed that the purified mutant designated Ent. cloacae J28 outcompetes the wild-type strain on roots but not in liquid cultures. In Ent. cloacae J28, the transposon is inserted upstream of the hns gene. Quantitative RT-PCR showed that transposon insertion increased expression of hns on roots. These results indicate that increased expression of hns in Ent. cloacae enhances competitive colonization of roots. A better understanding of the genes involved in plant colonization will contribute to the development of PGPR that can compete more effectively in agricultural soils.

  18. Root-synthesized cytokinins improve shoot growth and fruit yield in salinized tomato (Solanum lycopersicum L.) plants

    PubMed Central

    Ghanem, Michel Edmond; Smigocki, Ann C.; Frébort, Ivo; Pospíšilová, Hana; Martínez-Andújar, Cristina; Acosta, Manuel; Sánchez-Bravo, José; Lutts, Stanley; Dodd, Ian C.; Pérez-Alfocea, Francisco

    2011-01-01

    Salinity limits crop productivity, in part by decreasing shoot concentrations of the growth-promoting and senescence-delaying hormones cytokinins. Since constitutive cytokinin overproduction may have pleiotropic effects on plant development, two approaches assessed whether specific root-localized transgenic IPT (a key enzyme for cytokinin biosynthesis) gene expression could substantially improve tomato plant growth and yield under salinity: transient root IPT induction (HSP70::IPT) and grafting wild-type (WT) shoots onto a constitutive IPT-expressing rootstock (WT/35S::IPT). Transient root IPT induction increased root, xylem sap, and leaf bioactive cytokinin concentrations 2- to 3-fold without shoot IPT gene expression. Although IPT induction reduced root biomass (by 15%) in control (non-salinized) plants, in salinized plants (100 mM NaCl for 22 d), increased cytokinin concentrations delayed stomatal closure and leaf senescence and almost doubled shoot growth (compared with WT plants), with concomitant increases in the essential nutrient K+ (20%) and decreases in the toxic ion Na+ (by 30%) and abscisic acid (by 20–40%) concentrations in transpiring mature leaves. Similarly, WT/35S::IPT plants (scion/rootstock) grown with 75 mM NaCl for 90 d had higher fruit trans-zeatin concentrations (1.5- to 2-fold) and yielded 30% more than WT/non-transformed plants. Enhancing root cytokinin synthesis modified both shoot hormonal and ionic status, thus ameliorating salinity-induced decreases in growth and yield. PMID:20959628

  19. Dark exposure of petunia cuttings strongly improves adventitious root formation and enhances carbohydrate availability during rooting in the light.

    PubMed

    Klopotek, Yvonne; Haensch, Klaus-Thomas; Hause, Bettina; Hajirezaei, Mohammad-Reza; Druege, Uwe

    2010-05-01

    The effect of temporary dark exposure on adventitious root formation (ARF) in Petuniaxhybrida 'Mitchell' cuttings was investigated. Histological and metabolic changes in the cuttings during the dark treatment and subsequent rooting in the light were recorded. Excised cuttings were exposed to the dark for seven days at 10 degrees C followed by a nine-day rooting period in perlite or were rooted immediately for 16 days in a climate chamber at 22/20 degrees C (day/night) and a photosynthetic photon flux density (PPFD) of 100micromolm(-2)s(-1). Dark exposure prior to rooting increased, accelerated and synchronized ARF. The rooting period was reduced from 16 days (non-treated cuttings) to 9 days (treated cuttings). Under optimum conditions, despite the reduced rooting period, dark-exposed cuttings produced a higher number and length of roots than non-treated cuttings. An increase in temperature to 20 degrees C during the dark treatment or extending the cold dark exposure to 14 days caused a similar enhancement of root development compared to non-treated cuttings. Root meristem formation had already started during the dark treatment and was enhanced during the subsequent rooting period. Levels of soluble sugars (glucose, fructose and sucrose) and starch in leaf and basal stem tissues significantly decreased during the seven days of dark exposure. This depletion was, however, compensated during rooting after 6 and 24h for soluble sugars in leaves and the basal stem, respectively, whereas the sucrose level in the basal stem was already increased at 6h. The association of higher carbohydrate levels with improved rooting in previously dark-exposed versus non-treated cuttings indicates that increased post-darkness carbohydrate availability and allocation towards the stem base contribute to ARF under the influence of dark treatment and provide energy for cell growth subject to a rising sink intensity in the base of the cutting. Copyright 2009 Elsevier GmbH. All rights reserved.

  20. A global Fine-Root Ecology Database to address below-ground challenges in plant ecology.

    PubMed

    Iversen, Colleen M; McCormack, M Luke; Powell, A Shafer; Blackwood, Christopher B; Freschet, Grégoire T; Kattge, Jens; Roumet, Catherine; Stover, Daniel B; Soudzilovskaia, Nadejda A; Valverde-Barrantes, Oscar J; van Bodegom, Peter M; Violle, Cyrille

    2017-02-28

    Variation and tradeoffs within and among plant traits are increasingly being harnessed by empiricists and modelers to understand and predict ecosystem processes under changing environmental conditions. While fine roots play an important role in ecosystem functioning, fine-root traits are underrepresented in global trait databases. This has hindered efforts to analyze fine-root trait variation and link it with plant function and environmental conditions at a global scale. This Viewpoint addresses the need for a centralized fine-root trait database, and introduces the Fine-Root Ecology Database (FRED, http://roots.ornl.gov) which so far includes > 70 000 observations encompassing a broad range of root traits and also includes associated environmental data. FRED represents a critical step toward improving our understanding of below-ground plant ecology. For example, FRED facilitates the quantification of variation in fine-root traits across root orders, species, biomes, and environmental gradients while also providing a platform for assessments of covariation among root, leaf, and wood traits, the role of fine roots in ecosystem functioning, and the representation of fine roots in terrestrial biosphere models. Continued input of observations into FRED to fill gaps in trait coverage will improve our understanding of changes in fine-root traits across space and time.

  1. Plant traits that enhance pollutant removal from stormwater in biofiltration systems.

    PubMed

    Read, Jennifer; Fletcher, Tim D; Wevill, Tricia; Deletic, Ana

    2010-01-01

    Plants species have been shown to improve the performance of stormwater biofiltration systems, particularly in removal of N and P. Recent research has shown that plants vary in their contribution to pollutant removal but little is known about the type of plant that is best suited to use in biofilters in terms of survival, growth rate, and performance. In this study, growth responses of 20 species to applications of semi-synthetic stormwater were measured, and the roles of key plant traits in removal of N, P, and several metals were investigated. There was no evidence of negative effects of stormwater application on plant growth, and plant traits, particularly root traits, were strongly correlated negatively with N and P concentrations of effluent stormwater. The most common and strong contributors to N and P removal appeared to be the length of the longest root, rooting depth, total root length, and root mass. The plants that made the strongest contribution to pollutant removal, e.g, Carex appressa, combined these traits with high growth rates. Investigation of other plant traits (e.g, physiology), causal mechanisms, and effects of more complex planting environments (e.g, species mixtures) should further guide the selection of plants to enhance performance of biofiltration systems.

  2. Probiotic Diversity Enhances Rhizosphere Microbiome Function and Plant Disease Suppression

    PubMed Central

    Hu, Jie; Friman, Ville-Petri; Gu, Shao-hua; Wang, Xiao-fang; Eisenhauer, Nico; Yang, Tian-jie; Ma, Jing; Shen, Qi-rong; Jousset, Alexandre

    2016-01-01

    ABSTRACT Bacterial communities associated with plant roots play an important role in the suppression of soil-borne pathogens, and multispecies probiotic consortia may enhance disease suppression efficacy. Here we introduced defined Pseudomonas species consortia into naturally complex microbial communities and measured the importance of Pseudomonas community diversity for their survival and the suppression of the bacterial plant pathogen Ralstonia solanacearum in the tomato rhizosphere microbiome. The survival of introduced Pseudomonas consortia increased with increasing diversity. Further, high Pseudomonas diversity reduced pathogen density in the rhizosphere and decreased the disease incidence due to both intensified resource competition and interference with the pathogen. These results provide novel mechanistic insights into elevated pathogen suppression by diverse probiotic consortia in naturally diverse plant rhizospheres. Ecologically based community assembly rules could thus play a key role in engineering functionally reliable microbiome applications. PMID:27965449

  3. Induced root-secreted phenolic compounds as a belowground plant defense

    PubMed Central

    Burlat, Vincent; Schurr, Ulrich; Röse, Ursula SR

    2010-01-01

    Rhizosphere is the complex place of numerous interactions between plant roots, microbes and soil fauna. Whereas plant interactions with aboveground organisms are largely described, unravelling plant belowground interactions remains challenging. Plant root chemical communication can lead to positive interactions with nodulating bacteria, mycorriza or biocontrol agents or to negative interactions with pathogens or root herbivores. A recent study1 suggested that root exudates contribute to plant pathogen resistance via secretion of antimicrobial compounds. These findings point to the importance of plant root exudates as belowground signalling molecules, particularly in defense responses. In our report,2 we showed that under Fusarium attack the barley root system launched secretion of phenolic compounds with antimicrobial activity. The secretion of de novo biosynthesized t-cinnamic acid induced within 2 days illustrates the dynamic of plant defense mechanisms at the root level. We discuss the costs and benefits of induced defense responses in the rhizosphere. We suggest that plant defense through root exudation may be cultivar dependent and higher in wild or less domesticated varieties. PMID:20699651

  4. Tree root systems competing for soil moisture in a 3D soil–plant model

    Treesearch

    Gabriele Manoli; Sara Bonetti; Jean-Christophe Domec; Mario Putti; Gabriel Katul; Marco Marani

    2014-01-01

    Competition for water among multiple tree rooting systems is investigated using a soil–plant model that accounts for soil moisture dynamics and root water uptake (RWU), whole plant transpiration, and leaflevel photosynthesis. The model is based on a numerical solution to the 3D Richards equation modified to account for a 3D RWU, trunk xylem, and stomatal conductances....

  5. Adventitious Root Formation of Forest Trees and Horticultural Plants - From Genes to Applications

    USDA-ARS?s Scientific Manuscript database

    Adventitious root formation is a key step in the clonal propagation of forest trees and horticultural crops. Difficulties in forming adventitious roots (ARs) on stem cuttings and plants produced in vitro hinders the propagation of elite trees and efficient production of many horticultural plant spec...

  6. Vitamins for enhancing plant resistance.

    PubMed

    Boubakri, Hatem; Gargouri, Mahmoud; Mliki, Ahmed; Brini, Faiçal; Chong, Julie; Jbara, Moez

    2016-09-01

    This paper provides an overview on vitamins with inducing activities in plants, the molecular and cellular mechanisms implicated, and the hormonal signalling-network regulating this process. Moreover, it reports how vitamins might be part of the molecular events linked to induced resistance by the conventional elicitors. Induced resistance (IR), exploiting the plant innate-defense system is a sustainable strategy for plant disease control. In the last decade, vitamins have been proven to act as inducers of disease resistance, and these findings have received an important attention owing to their safety and cost effectiveness. Vitamins, including thiamine (TH, vitamin B1), riboflavin (RF, vitamin B2), menadione sodium bisulfite (MSB, vitamin K3), Para-aminobenzoic acid (PABA, vitamin Bx), and folic acid (FA, vitamin B9) provided an efficient protection against a wide range of pathogens through the modulation of specific host-defense facets. However, other vitamins, such as ascorbic acid (AA, vitamin C) and tocopherols (vitamin E), have been shown to be a part of the molecular mechanisms associated to IR. The present review is the first to summarize what vitamins are acting as inducers of disease resistance in plants and how could they be modulated by the conventional elicitors. Thus, this report provides an overview on the protective abilities of vitamins and the molecular and cellular mechanisms underlying their activities. Moreover, it describes the hormonal-signalling network regulating vitamin-signal transduction during IR. Finally, a biochemical model describing how vitamins are involved in the establishment of IR process is discussed.

  7. Searching for plant root traits to improve soil cohesion and resist soil erosion

    NASA Astrophysics Data System (ADS)

    De Baets, Sarah; Smyth, Kevin; Denbigh, Tom; Weldon, Laura; Higgins, Ben; Matyjaszkiewicz, Antoni; Meersmans, Jeroen; Chenchiah, Isaac; Liverpool, Tannie; Quine, Tim; Grierson, Claire

    2017-04-01

    Soil erosion poses a serious threat to future food and environmental security. Soil erosion protection measures are therefore of great importance for soil conservation and food security. Plant roots have proven to be very effective in stabilizing the soil and protecting the soil against erosion. However, no clear insights are yet obtained into the root traits that are responsible for root-soil cohesion. This is important in order to better select the best species for soil protection. Research using Arabidopsis mutants has made great progress towards explaining how root systems are generated by growth, branching, and responses to gravity, producing mutants that affect root traits. In this study, the performance of selected Arabidopsis mutants is analyzed in three root-soil cohesion assays. Measurements of detachment, uprooting force and soil detachment are here combined with the microscopic analysis of root properties, such as the presence, length and density of root hairs in this case. We found that Arabidopsis seedlings with root hairs (wild type, wer myb23, rsl4) were more difficult to detach from gel media than hairless (cpc try) or short haired (rsl4, rhd2) roots. Hairy roots (wild type, wer myb23) on mature, non-reproductive rosettes were more difficult to uproot from compost or clay soil than hairless roots (cpc try). At high root densities, erosion rates from soils with hairless roots (cpc try) were as much as 10 times those seen from soils occupied by roots with hairs (wer myb23, wild type). We find therefore root hairs play a significant role in root-soil cohesion and in minimizing erosion. This framework and associated suite of experimental assays demonstrates its ability to measure the effect of any root phenotype on the effectiveness of plant roots in binding substrates and reducing erosion.

  8. Transgenic plants with enhanced growth characteristics

    DOEpatents

    Unkefer, Pat J.; Anderson, Penelope S.; Knight, Thomas J.

    2016-09-06

    The invention relates to transgenic plants exhibiting dramatically enhanced growth rates, greater seed and fruit/pod yields, earlier and more productive flowering, more efficient nitrogen utilization, increased tolerance to high salt conditions, and increased biomass yields. In one embodiment, transgenic plants engineered to over-express both glutamine phenylpyruvate transaminase (GPT) and glutamine synthetase (GS) are provided. The GPT+GS double-transgenic plants of the invention consistently exhibit enhanced growth characteristics, with T0 generation lines showing an increase in biomass over wild type counterparts of between 50% and 300%. Generations that result from sexual crosses and/or selfing typically perform even better, with some of the double-transgenic plants achieving an astounding four-fold biomass increase over wild type plants.

  9. Enhanced Lignin Monomer Production Caused by Cinnamic Acid and Its Hydroxylated Derivatives Inhibits Soybean Root Growth

    PubMed Central

    Lima, Rogério Barbosa; Salvador, Victor Hugo; dos Santos, Wanderley Dantas; Bubna, Gisele Adriana; Finger-Teixeira, Aline; Soares, Anderson Ricardo; Marchiosi, Rogério; Ferrarese, Maria de Lourdes Lucio; Ferrarese-Filho, Osvaldo

    2013-01-01

    Cinnamic acid and its hydroxylated derivatives (p-coumaric, caffeic, ferulic and sinapic acids) are known allelochemicals that affect the seed germination and root growth of many plant species. Recent studies have indicated that the reduction of root growth by these allelochemicals is associated with premature cell wall lignification. We hypothesized that an influx of these compounds into the phenylpropanoid pathway increases the lignin monomer content and reduces the root growth. To confirm this hypothesis, we evaluated the effects of cinnamic, p-coumaric, caffeic, ferulic and sinapic acids on soybean root growth, lignin and the composition of p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) monomers. To this end, three-day-old seedlings were cultivated in nutrient solution with or without allelochemical (or selective enzymatic inhibitors of the phenylpropanoid pathway) in a growth chamber for 24 h. In general, the results showed that 1) cinnamic, p-coumaric, caffeic and ferulic acids reduced root growth and increased lignin content; 2) cinnamic and p-coumaric acids increased p-hydroxyphenyl (H) monomer content, whereas p-coumaric, caffeic and ferulic acids increased guaiacyl (G) content, and sinapic acid increased sinapyl (S) content; 3) when applied in conjunction with piperonylic acid (PIP, an inhibitor of the cinnamate 4-hydroxylase, C4H), cinnamic acid reduced H, G and S contents; and 4) when applied in conjunction with 3,4-(methylenedioxy)cinnamic acid (MDCA, an inhibitor of the 4-coumarate:CoA ligase, 4CL), p-coumaric acid reduced H, G and S contents, whereas caffeic, ferulic and sinapic acids reduced G and S contents. These results confirm our hypothesis that exogenously applied allelochemicals are channeled into the phenylpropanoid pathway causing excessive production of lignin and its main monomers. By consequence, an enhanced stiffening of the cell wall restricts soybean root growth. PMID:24312480

  10. Enhanced lignin monomer production caused by cinnamic Acid and its hydroxylated derivatives inhibits soybean root growth.

    PubMed

    Lima, Rogério Barbosa; Salvador, Victor Hugo; dos Santos, Wanderley Dantas; Bubna, Gisele Adriana; Finger-Teixeira, Aline; Soares, Anderson Ricardo; Marchiosi, Rogério; Ferrarese, Maria de Lourdes Lucio; Ferrarese-Filho, Osvaldo

    2013-01-01

    Cinnamic acid and its hydroxylated derivatives (p-coumaric, caffeic, ferulic and sinapic acids) are known allelochemicals that affect the seed germination and root growth of many plant species. Recent studies have indicated that the reduction of root growth by these allelochemicals is associated with premature cell wall lignification. We hypothesized that an influx of these compounds into the phenylpropanoid pathway increases the lignin monomer content and reduces the root growth. To confirm this hypothesis, we evaluated the effects of cinnamic, p-coumaric, caffeic, ferulic and sinapic acids on soybean root growth, lignin and the composition of p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) monomers. To this end, three-day-old seedlings were cultivated in nutrient solution with or without allelochemical (or selective enzymatic inhibitors of the phenylpropanoid pathway) in a growth chamber for 24 h. In general, the results showed that 1) cinnamic, p-coumaric, caffeic and ferulic acids reduced root growth and increased lignin content; 2) cinnamic and p-coumaric acids increased p-hydroxyphenyl (H) monomer content, whereas p-coumaric, caffeic and ferulic acids increased guaiacyl (G) content, and sinapic acid increased sinapyl (S) content; 3) when applied in conjunction with piperonylic acid (PIP, an inhibitor of the cinnamate 4-hydroxylase, C4H), cinnamic acid reduced H, G and S contents; and 4) when applied in conjunction with 3,4-(methylenedioxy)cinnamic acid (MDCA, an inhibitor of the 4-coumarate:CoA ligase, 4CL), p-coumaric acid reduced H, G and S contents, whereas caffeic, ferulic and sinapic acids reduced G and S contents. These results confirm our hypothesis that exogenously applied allelochemicals are channeled into the phenylpropanoid pathway causing excessive production of lignin and its main monomers. By consequence, an enhanced stiffening of the cell wall restricts soybean root growth.

  11. Root cortical aerenchyma enhances the growth of maize on soils with suboptimal availability of nitrogen, phosphorus, and potassium.

    PubMed

    Postma, Johannes Auke; Lynch, Jonathan Paul

    2011-07-01

    Root cortical aerenchyma (RCA) is induced by hypoxia, drought, and several nutrient deficiencies. Previous research showed that RCA formation reduces the respiration and nutrient content of root tissue. We used SimRoot, a functional-structural model, to provide quantitative support for the hypothesis that RCA formation is a useful adaptation to suboptimal availability of phosphorus, nitrogen, and potassium by reducing the metabolic costs of soil exploration in maize (Zea mays). RCA increased the growth of simulated 40-d-old maize plants up to 55%, 54%, or 72% on low nitrogen, phosphorus, or potassium soil, respectively, and reduced critical fertility levels by 13%, 12%, or 7%, respectively. The greater utility of RCA on low-potassium soils is associated with the fact that root growth in potassium-deficient plants was more carbon limited than in phosphorus- and nitrogen-deficient plants. In contrast to potassium-deficient plants, phosphorus- and nitrogen-deficient plants allocate more carbon to the root system as the deficiency develops. The utility of RCA also depended on other root phenes and environmental factors. On low-phosphorus soils (7.5 μM), the utility of RCA was 2.9 times greater in plants with increased lateral branching density than in plants with normal branching. On low-nitrate soils, the utility of RCA formation was 56% greater in coarser soils with high nitrate leaching. Large genetic variation in RCA formation and the utility of RCA for a range of stresses position RCA as an interesting crop-breeding target for enhanced soil resource acquisition.

  12. Do root traits affect a plant's ability to influence soil erosion?

    NASA Astrophysics Data System (ADS)

    Burak, Emma; Quinton, John; Dodd, Ian

    2017-04-01

    With the ever increasing global population the agricultural sector is put under increasing pressure. This pressure is imposed on the soil and results in wide spread degradation that ultimately decreases productivity. Soil erosion is one of the main features of this degradation. Much focus has been put on the ability of plant canopies to mitigate soil erosion but little research has assessed the impact of below ground biomass. It is understood that woody roots reinforce slopes and lateral roots are believed to support the soil surface but the impact of root hairs is completely unknown. This study used two root hairless mutants one of barley (brb) and one of maize (rth3) along with their wild types (WT) to assess the capacity of different root traits to bind soil particles to the root system, creating a physical coating called a rhizosheath. The two genotypes were grown in a clay loam and periodically harvested during vegetative development. Rhizosheath weight was used to measure the ability of the root system to effectively bind soil particles, while root length was measured to standardise the results between genotypes. Overall, rhizosheath weight increased linearly with root length. When compared to WT plants of the same age, the root length of brb was, on average, 37% greater, suggesting that they compensated for the absence of root hairs by proliferating lateral roots. However, WT plants were far superior at binding soil particles as the rhizosheath weights were 5 fold greater, when expressed per unit root length. Thus root hairs are more important in binding soil particles than lateral roots. Whether these genotypic differences in root traits affect soil erosion will be assessed using mesocosm and field trials. Keywords: Soil erosion, Roots, Barley, Rhizosheath

  13. A global Fine-Root Ecology Database to address below-ground challenges in plant ecology

    DOE PAGES

    Iversen, Colleen M.; McCormack, M. Luke; Powell, A. Shafer; ...

    2017-02-28

    Variation and tradeoffs within and among plant traits are increasingly being harnessed by empiricists and modelers to understand and predict ecosystem processes under changing environmental conditions. And while fine roots play an important role in ecosystem functioning, fine-root traits are underrepresented in global trait databases. This has hindered efforts to analyze fine-root trait variation and link it with plant function and environmental conditions at a global scale. This Viewpoint addresses the need for a centralized fine-root trait database, and introduces the Fine-Root Ecology Database (FRED, http://roots.ornl.gov) which so far includes > 70 000 observations encompassing a broad range of rootmore » traits and also includes associated environmental data. FRED represents a critical step toward improving our understanding of below-ground plant ecology. For example, FRED facilitates the quantification of variation in fine-root traits across root orders, species, biomes, and environmental gradients while also providing a platform for assessments of covariation among root, leaf, and wood traits, the role of fine roots in ecosystem functioning, and the representation of fine roots in terrestrial biosphere models. There has been a continued input of observations into FRED to fill gaps in trait coverage will improve our understanding of changes in fine-root traits across space and time.« less

  14. Spatial heterogeneity of plant-soil feedback affects root interactions and interspecific competition.

    PubMed

    Hendriks, Marloes; Ravenek, Janneke M; Smit-Tiekstra, Annemiek E; van der Paauw, Jan Willem; de Caluwe, Hannie; van der Putten, Wim H; de Kroon, Hans; Mommer, Liesje

    2015-08-01

    Plant-soil feedback is receiving increasing interest as a factor influencing plant competition and species coexistence in grasslands. However, we do not know how spatial distribution of plant-soil feedback affects plant below-ground interactions. We investigated the way in which spatial heterogeneity of soil biota affects competitive interactions in grassland plant species. We performed a pairwise competition experiment combined with heterogeneous distribution of soil biota using four grassland plant species and their soil biota. Patches were applied as quadrants of 'own' and 'foreign' soils from all plant species in all pairwise combinations. To evaluate interspecific root responses, species-specific root biomass was quantified using real-time PCR. All plant species suffered negative soil feedback, but strength was species-specific, reflected by a decrease in root growth in own compared with foreign soil. Reduction in root growth in own patches by the superior plant competitor provided opportunities for inferior competitors to increase root biomass in these patches. These patterns did not cascade into above-ground effects during our experiment. We show that root distributions can be determined by spatial heterogeneity of soil biota, affecting plant below-ground competitive interactions. Thus, spatial heterogeneity of soil biota may contribute to plant species coexistence in species-rich grasslands.

  15. The RootScope: a simple high-throughput screening system for quantitating gene expression dynamics in plant roots.

    PubMed

    Kast, Erin J; Nguyen, Minh-Duyen T; Lawrence, Rosalie E; Rabeler, Christina; Kaplinsky, Nicholas J

    2013-10-12

    High temperature stress responses are vital for plant survival. The mechanisms that plants use to sense high temperatures are only partially understood and involve multiple sensing and signaling pathways. Here we describe the development of the RootScope, an automated microscopy system for quantitating heat shock responses in plant roots. The promoter of Hsp17.6 was used to build a Hsp17.6p:GFP transcriptional reporter that is induced by heat shock in Arabidopsis. An automated fluorescence microscopy system which enables multiple roots to be imaged in rapid succession was used to quantitate Hsp17.6p:GFP response dynamics. Hsp17.6p:GFP signal increased with temperature increases from 28°C to 37°C. At 40°C the kinetics and localization of the response are markedly different from those at 37°C. This suggests that different mechanisms mediate heat shock responses above and below 37°C. Finally, we demonstrate that Hsp17.6p:GFP expression exhibits wave like dynamics in growing roots. The RootScope system is a simple and powerful platform for investigating the heat shock response in plants.

  16. The RootScope: a simple high-throughput screening system for quantitating gene expression dynamics in plant roots

    PubMed Central

    2013-01-01

    Background High temperature stress responses are vital for plant survival. The mechanisms that plants use to sense high temperatures are only partially understood and involve multiple sensing and signaling pathways. Here we describe the development of the RootScope, an automated microscopy system for quantitating heat shock responses in plant roots. Results The promoter of Hsp17.6 was used to build a Hsp17.6p:GFP transcriptional reporter that is induced by heat shock in Arabidopsis. An automated fluorescence microscopy system which enables multiple roots to be imaged in rapid succession was used to quantitate Hsp17.6p:GFP response dynamics. Hsp17.6p:GFP signal increased with temperature increases from 28°C to 37°C. At 40°C the kinetics and localization of the response are markedly different from those at 37°C. This suggests that different mechanisms mediate heat shock responses above and below 37°C. Finally, we demonstrate that Hsp17.6p:GFP expression exhibits wave like dynamics in growing roots. Conclusions The RootScope system is a simple and powerful platform for investigating the heat shock response in plants. PMID:24119322

  17. CLE peptides regulate lateral root development in response to nitrogen nutritional status of plants.

    PubMed

    Araya, Takao; von Wirén, Nicolaus; Takahashi, Hideki

    2014-05-23

    CLE (CLAVATA3/EMBRYO SURROUNDING REGION (ESR)) peptides control meristem functions in plants. Our recent study highlights the critical role of a peptide-receptor signaling module composed of nitrogen (N)-responsive CLE peptides and the CLAVATA1 (CLV1) leucine-rich repeat receptor-like kinase in controlling lateral root development in Arabidopsis thaliana. CLE1, -3, -4 and -7 are expressed in root pericycle cells in Arabidopsis roots under N-limited growth conditions. Overexpression of these CLE genes inhibits lateral root emergence from the primary root. The inhibitory action of N-responsive CLE peptides on lateral root development requires the function of CLV1 expressed in phloem companion cells in roots, suggesting that downstream signals are transferred through phloem for systemic regulation of root system architecture. An additional mechanism downstream of CLV1 feedback-regulates transcript levels of N-responsive CLE genes in roots for fine-tuning the signal amplitude.

  18. CLE peptides regulate lateral root development in response to nitrogen nutritional status of plants.

    PubMed

    Araya, Takao; von Wirén, Nicolaus; Takahashi, Hideki

    2014-01-01

    CLE (CLAVATA3/embryo surrounding region (ESR)) peptides control meristem functions in plants. Our recent study highlights the critical role of a peptide-receptor signaling module composed of nitrogen (N)-responsive CLE peptides and the CLAVATA1 (CLV1) leucine-rich repeat receptor-like kinase in controlling lateral root development in Arabidopsis thaliana. CLE1, -3, -4 and -7 are expressed in root pericycle cells in Arabidopsis roots under N-limited growth conditions. Overexpression of these CLE genes inhibits lateral root emergence from the primary root. The inhibitory action of N-responsive CLE peptides on lateral root development requires the function of CLV1 expressed in phloem companion cells in roots, suggesting that downstream signals are transferred through phloem for systemic regulation of root system architecture. An additional mechanism downstream of CLV1 feedback-regulates transcript levels of N-responsive CLE genes in roots for fine-tuning the signal amplitude.

  19. [Disease resistance signal transfer between roots of different tomato plants through common arbuscular mycorrhiza networks].

    PubMed

    Xie, Li-Jun; Song, Yuan-Yuan; Zeng, Ren-Sen; Wang, Rui-Long; Wei, Xiao-Chen; Ye, Mao; Hu, Lin; Zhang, Hui

    2012-05-01

    Common mycorrhizal networks (CMNs) are the underground conduits of nutrient exchange between plants. However, whether the CMNs can serve as the underground conduits of chemical communication to transfer the disease resistance signals between plants are unknown. By inoculating arbuscular mycorrhizal fungus (AMF) Glomus mosseae to establish CMNs between 'donor' and 'receiver' tomato plants, and by inoculating Alternaria solani, the causal agent of tomato early blight disease, to the 'donor' plants, this paper studied whether the potential disease resistance signals can be transferred between the 'donor' and 'receiver' plants roots. The real time RT-PCR analysis showed that after inoculation with A. solani, the AMF-inoculated 'donor' plants had strong expression of three test defense-related genes in roots, with the transcript levels of the phenylalanine ammonia-lyase (PAL), lipoxygenase (LOX) and chitinase (PR3) being significantly higher than those in the roots of the 'donor' plants only inoculated with A. solani, not inoculated with both A. solani and AMF, and only inoculated with AMF. More importantly, in the presence of CMNs, the expression levels of the three genes in the roots of the 'receiver' plants were significantly higher than those of the 'receiver' plants without CMNs connection, with the connection blocking, and with the connection but the 'donor' plants not A. solani-inoculated. Compared with the control (without CMNs connection), the transcript level of the PAL, LOX and PR3 in the roots of the 'receiver' plants having CMNs connection with the 'donor' plants was 4.2-, 4.5- and 3.5-fold higher, respectively. In addition, the 'donor' plants activated their defensive responses more quickly than the 'receiver' plants (18 and 65 h vs. 100 and 140 h). These findings suggested that the disease resistance signals produced by the pathogen-induced 'donor' tomato plant roots could be transferred to the 'receiver' plant roots through CMNs.

  20. Mitigation of antagonistic effects on plant growth due to root co-colonization by dark septate endophytes and ectomycorrhiza.

    PubMed

    Reininger, Vanessa; Sieber, Thomas N

    2013-12-01

    Dark septate endophytes (DSE) are very common root colonizers of woody plant species. Ascomycetes of the Phialocephala fortinii s.l.-Acephala applanata species complex (PAC) are the main representatives of DSE fungi in forest ecosystems. PAC and mycorrhizal fungi share the same habitat, but interactions among PAC, mycorrhizal fungi and plants are poorly understood. We compared the effects of single and dual inoculation of Norway spruce seedlings with PAC and the ectomycorrhizal (ECM) fungus Hebeloma crustuliniforme on host growth, degree of mycorrhization and density of endophytic PAC biomass. Single colonization by H. crustuliniforme or PAC significantly reduced plant biomass. Dual colonization reduced or neutralized plant growth depression caused by single fungal colonization. The degree of mycorrhization was independent on PAC colonization, and mycorrhization significantly reduced endophytic PAC biomass. Plant biomass of dually colonized plants positively correlated with PAC biomass. These results demonstrate the ability of dual inoculation of PAC and H. crustuliniforme to neutralize plant growth depression caused by single fungal inoculation. Our explanations of enhanced plant growth in dually inoculated plants are the inhibition of PAC during root colonization by the ECM mantle and ECM-mediated access to plant growth-promoting nutrients resulting from the mineralization of the potting medium by PAC.

  1. Vesicular-arbuscular mycorrhizae and the enzymatic utilization of inorganic phosphate by plant roots: Progress report 1985

    SciTech Connect

    Marx, D. H.

    1985-01-01

    It is well known that phosphorus absorption, especially from soil with low phosphorus levels, by plant roots can be enhanced by mycorrhizal infection. Root cortical cells colonized by vesicular-arbuscular mycorrhizal fungi (VAM) have higher concentrations of phosphorus than noninfected cells. Polyphosphate is the major phosphorus reserve in many fungi and is reported to be present abundantly in young and proliferating arbuscules. We propose that mycorrhizal polyphosphate can be utilized by the VAM-plant symbiont system as a phosphorus donor and an energy source in the glycolytic pathway, possibly after being hydrolyzed to pytrophosphate (PPi). The VAM systems of infected and noninfected roots of sweetgum (Liquidambar styraciflua L.) and onion (Allium cepa L. var. Texas Grand) were used to compare the activity of PPI-dependent phosphofructokinase (PFK), an enzyme utilizing PPi to convert frutose-6-phosphate into fructosel,6-bisphosphate. The ATP-PKF activity was measured also. 1 fig., 3 tabs.

  2. Rooting out Defense Mechanisms in Wheat against Plant Parasitic Nematodes

    USDA-ARS?s Scientific Manuscript database

    Root-lesion nematodes (Pratylenchus spp.) are soil borne pathogens of many important agricultural crops including wheat. Pratylenchus invade root cells and feed using a stylet, resulting in cell death. Common signs of Pratylenchus damage are root lesions, girdling, and lack of lateral branching. ...

  3. Zn2+ -induced changes at the root level account for the increased tolerance of acclimated tobacco plants.

    PubMed

    Bazihizina, Nadia; Taiti, Cosimo; Marti, Lucia; Rodrigo-Moreno, Ana; Spinelli, Francesco; Giordano, Cristiana; Caparrotta, Stefania; Gori, Massimo; Azzarello, Elisa; Mancuso, Stefano

    2014-09-01

    Evidence suggests that heavy-metal tolerance can be induced in plants following pre-treatment with non-toxic metal concentrations, but the results are still controversial. In the present study, tobacco plants were exposed to increasing Zn2+ concentrations (up to 250 and/or 500 μM ZnSO4) with or without a 1-week acclimation period with 30 μM ZnSO4. Elevated Zn2+ was highly toxic for plants, and after 3 weeks of treatments there was a marked (≥50%) decline in plant growth in non-acclimated plants. Plant acclimation, on the other hand, increased plant dry mass and leaf area up to 1.6-fold compared with non-acclimated ones. In non-acclimated plants, the addition of 250 μM ZnSO4 led to transient membrane depolarization and stomatal closure within 24h from the addition of the stress; by contrast, the acclimation process was associated with an improved stomatal regulation and a superior ability to maintain a negative root membrane potential, with values on average 37% more negative compared with non-acclimated plants. The different response at the plasma-membrane level between acclimated and non-acclimated plants was associated with an enhanced vacuolar Zn2+ sequestration and up to 2-fold higher expression of the tobacco orthologue of the Arabidopsis thaliana MTP1 gene. Thus, the acclimation process elicited specific detoxification mechanisms in roots that enhanced Zn2+ compartmentalization in vacuoles, thereby improving root membrane functionality and stomatal regulation in leaves following elevated Zn2+ stress.

  4. Zn2+-induced changes at the root level account for the increased tolerance of acclimated tobacco plants

    PubMed Central

    Bazihizina, Nadia; Taiti, Cosimo; Marti, Lucia; Rodrigo-Moreno, Ana; Spinelli, Francesco; Giordano, Cristiana; Caparrotta, Stefania; Gori, Massimo; Azzarello, Elisa; Mancuso, Stefano

    2014-01-01

    Evidence suggests that heavy-metal tolerance can be induced in plants following pre-treatment with non-toxic metal concentrations, but the results are still controversial. In the present study, tobacco plants were exposed to increasing Zn2+ concentrations (up to 250 and/or 500 μM ZnSO4) with or without a 1-week acclimation period with 30 μM ZnSO4. Elevated Zn2+ was highly toxic for plants, and after 3 weeks of treatments there was a marked (≥50%) decline in plant growth in non-acclimated plants. Plant acclimation, on the other hand, increased plant dry mass and leaf area up to 1.6-fold compared with non-acclimated ones. In non-acclimated plants, the addition of 250 μM ZnSO4 led to transient membrane depolarization and stomatal closure within 24h from the addition of the stress; by contrast, the acclimation process was associated with an improved stomatal regulation and a superior ability to maintain a negative root membrane potential, with values on average 37% more negative compared with non-acclimated plants. The different response at the plasma-membrane level between acclimated and non-acclimated plants was associated with an enhanced vacuolar Zn2+ sequestration and up to 2-fold higher expression of the tobacco orthologue of the Arabidopsis thaliana MTP1 gene. Thus, the acclimation process elicited specific detoxification mechanisms in roots that enhanced Zn2+ compartmentalization in vacuoles, thereby improving root membrane functionality and stomatal regulation in leaves following elevated Zn2+ stress. PMID:24928985

  5. Water release through plant roots: new insights into its consequences at the plant and ecosystem level.

    PubMed

    Prieto, Iván; Armas, Cristina; Pugnaire, Francisco I

    2012-03-01

    Hydraulic redistribution (HR) is the passive movement of water between different soil parts via plant root systems, driven by water potential gradients in the soil-plant interface. New data suggest that HR is a heterogeneous and patchy process. In this review we examine the main biophysical and environmental factors controlling HR and its main implications at the plant, community and ecosystem levels. Experimental evidence and the use of novel modelling approaches suggest that HR may have important implications at the community scale, affecting net primary productivity as well as water and vegetation dynamics. Globally, HR may influence hydrological and biogeochemical cycles and, ultimately, climate. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

  6. Cadmium induces hypodermal periderm formation in the roots of the monocotyledonous medicinal plant Merwilla plumbea

    PubMed Central

    Lux, Alexander; Vaculík, Marek; Martinka, Michal; Lišková, Desana; Kulkarni, Manoj G.; Stirk, Wendy A.; Van Staden, Johannes

    2011-01-01

    Background and Aims Merwilla plumbea is an important African medicinal plant. As the plants grow in soils contaminated with metals from mining activities, the danger of human intoxication exists. An experiment with plants exposed to cadmium (Cd) was performed to investigate the response of M. plumbea to this heavy metal, its uptake and translocation to plant organs and reaction of root tissues. Methods Plants grown from seeds were cultivated in controlled conditions. Hydroponic cultivation is not suitable for this species as roots do not tolerate aquatic conditions, and additional stress by Cd treatment results in total root growth inhibition and death. After cultivation in perlite the plants exposed to 1 and 5 mg Cd L−1 in half-strength Hoagland's solution were compared with control plants. Growth parameters were evaluated, Cd content was determined by inductively coupled plasma mass spectroscopy (ICP-MS) and root structure was investigated using various staining procedures, including the fluorescent stain Fluorol yellow 088 to detect suberin deposition in cell walls. Key Results The plants exposed to Cd were significantly reduced in growth. Most of the Cd taken up by plants after 4 weeks cultivation was retained in roots, and only a small amount was translocated to bulbs and leaves. In reaction to higher Cd concentrations, roots developed a hypodermal periderm close to the root tip. Cells produced by cork cambium impregnate their cell walls by suberin. Conclusions It is suggested that the hypodermal periderm is developed in young root parts in reaction to Cd toxicity to protect the root from radial uptake of Cd ions. Secondary meristems are usually not present in monocotyledonous species. Another interpretation explaining formation of protective suberized layers as a result of periclinal divisions of the hypodermis is discussed. This process may represent an as yet unknown defence reaction of roots when exposed to elemental stress. PMID:21118841

  7. Cadmium induces hypodermal periderm formation in the roots of the monocotyledonous medicinal plant Merwilla plumbea.

    PubMed

    Lux, Alexander; Vaculík, Marek; Martinka, Michal; Lisková, Desana; Kulkarni, Manoj G; Stirk, Wendy A; Van Staden, Johannes

    2011-02-01

    Merwilla plumbea is an important African medicinal plant. As the plants grow in soils contaminated with metals from mining activities, the danger of human intoxication exists. An experiment with plants exposed to cadmium (Cd) was performed to investigate the response of M. plumbea to this heavy metal, its uptake and translocation to plant organs and reaction of root tissues. Plants grown from seeds were cultivated in controlled conditions. Hydroponic cultivation is not suitable for this species as roots do not tolerate aquatic conditions, and additional stress by Cd treatment results in total root growth inhibition and death. After cultivation in perlite the plants exposed to 1 and 5 mg Cd L(-1) in half-strength Hoagland's solution were compared with control plants. Growth parameters were evaluated, Cd content was determined by inductively coupled plasma mass spectroscopy (ICP-MS) and root structure was investigated using various staining procedures, including the fluorescent stain Fluorol yellow 088 to detect suberin deposition in cell walls. The plants exposed to Cd were significantly reduced in growth. Most of the Cd taken up by plants after 4 weeks cultivation was retained in roots, and only a small amount was translocated to bulbs and leaves. In reaction to higher Cd concentrations, roots developed a hypodermal periderm close to the root tip. Cells produced by cork cambium impregnate their cell walls by suberin. It is suggested that the hypodermal periderm is developed in young root parts in reaction to Cd toxicity to protect the root from radial uptake of Cd ions. Secondary meristems are usually not present in monocotyledonous species. Another interpretation explaining formation of protective suberized layers as a result of periclinal divisions of the hypodermis is discussed. This process may represent an as yet unknown defence reaction of roots when exposed to elemental stress.

  8. Root Herbivores Drive Changes to Plant Primary Chemistry, but Root Loss Is Mitigated under Elevated Atmospheric CO2

    PubMed Central

    McKenzie, Scott W.; Johnson, Scott N.; Jones, T. Hefin; Ostle, Nick J.; Hails, Rosemary S.; Vanbergen, Adam J.

    2016-01-01

    Above- and belowground herbivory represents a major challenge to crop productivity and sustainable agriculture worldwide. How this threat from multiple herbivore pests will change under anthropogenic climate change, via altered trophic interactions and plant response traits, is key to understanding future crop resistance to herbivory. In this study, we hypothesized that atmospheric carbon enrichment would increase the amount (biomass) and quality (C:N ratio) of crop plant resources for above- and belowground herbivore species. In a controlled environment facility, we conducted a microcosm experiment using the large raspberry aphid (Amphorophora idaei), the root feeding larvae of the vine weevil (Otiorhynchus sulcatus), and the raspberry (Rubus idaeus) host-plant. There were four herbivore treatments (control, aphid only, weevil only and a combination of both herbivores) and an ambient (aCO2) or elevated (eCO2) CO2 treatment (390 versus 650 ± 50 μmol/mol) assigned to two raspberry cultivars (cv Glen Ample or Glen Clova) varying in resistance to aphid herbivory. Contrary to our predictions, eCO2 did not increase crop biomass or the C:N ratio of the plant tissues, nor affect herbivore abundance either directly or via the host-plant. Root herbivory reduced belowground crop biomass under aCO2 but not eCO2, suggesting that crops could tolerate attack in a CO2 enriched environment. Root herbivory also increased the C:N ratio in leaf tissue at eCO2, potentially due to decreased N uptake indicated by lower N concentrations found in the roots. Root herbivory greatly increased root C concentrations under both CO2 treatments. Our findings confirm that responses of crop biomass and biochemistry to climate change need examining within the context of herbivory, as biotic interactions appear as important as direct effects of eCO2 on crop productivity. PMID:27379129

  9. Root Herbivores Drive Changes to Plant Primary Chemistry, but Root Loss Is Mitigated under Elevated Atmospheric CO2.

    PubMed

    McKenzie, Scott W; Johnson, Scott N; Jones, T Hefin; Ostle, Nick J; Hails, Rosemary S; Vanbergen, Adam J

    2016-01-01

    Above- and belowground herbivory represents a major challenge to crop productivity and sustainable agriculture worldwide. How this threat from multiple herbivore pests will change under anthropogenic climate change, via altered trophic interactions and plant response traits, is key to understanding future crop resistance to herbivory. In this study, we hypothesized that atmospheric carbon enrichment would increase the amount (biomass) and quality (C:N ratio) of crop plant resources for above- and belowground herbivore species. In a controlled environment facility, we conducted a microcosm experiment using the large raspberry aphid (Amphorophora idaei), the root feeding larvae of the vine weevil (Otiorhynchus sulcatus), and the raspberry (Rubus idaeus) host-plant. There were four herbivore treatments (control, aphid only, weevil only and a combination of both herbivores) and an ambient (aCO2) or elevated (eCO2) CO2 treatment (390 versus 650 ± 50 μmol/mol) assigned to two raspberry cultivars (cv Glen Ample or Glen Clova) varying in resistance to aphid herbivory. Contrary to our predictions, eCO2 did not increase crop biomass or the C:N ratio of the plant tissues, nor affect herbivore abundance either directly or via the host-plant. Root herbivory reduced belowground crop biomass under aCO2 but not eCO2, suggesting that crops could tolerate attack in a CO2 enriched environment. Root herbivory also increased the C:N ratio in leaf tissue at eCO2, potentially due to decreased N uptake indicated by lower N concentrations found in the roots. Root herbivory greatly increased root C concentrations under both CO2 treatments. Our findings confirm that responses of crop biomass and biochemistry to climate change need examining within the context of herbivory, as biotic interactions appear as important as direct effects of eCO2 on crop productivity.

  10. Soil abiotic factors influence interactions between belowground herbivores and plant roots.

    PubMed

    Erb, Matthias; Lu, Jing

    2013-03-01

    Root herbivores are important ecosystem drivers and agricultural pests, and, possibly as a consequence, plants protect their roots using a variety of defensive strategies. One aspect that distinguishes belowground from aboveground plant-insect interactions is that roots are constantly exposed to a set of soil-specific abiotic factors. These factors can profoundly influence root resistance, and, consequently, the outcome of the interaction with belowground feeders. In this review, we synthesize the current literature on the impact of soil moisture, nutrients, and texture on root-herbivore interactions. We show that soil abiotic factors influence the interaction by modulating herbivore abundance and behaviour, root growth and resistance, beneficial microorganisms, as well as natural enemies of the herbivores. We suggest that abiotic heterogeneity may explain the high variability that is often encountered in root-herbivore systems. We also propose that under abiotic stress, the relative fitness value of the roots and the potential negative impact of herbivory increases, which may lead to a higher defensive investment and an increased recruitment of beneficial microorganisms by the plant. At the same time, both root-feeding herbivores and natural enemies are likely to decrease in abundance under extreme environmental conditions, leading to a context- and species-specific impact on plant fitness. Only by using tightly controlled experiments that include soil abiotic heterogeneity will it be possible to understand the impact of root feeders on an ecosystem scale and to develop predictive models for pest occurrence and impact.

  11. Global-scale latitudinal patterns of plant fine-root nitrogen and phosphorus.

    PubMed

    Yuan, Z Y; Chen, Han Y H; Reich, Peter B

    2011-06-14

    Most water and essential soil nutrient uptake is carried out by fine roots in plants. It is therefore important to understand the global geographic patterns of fine-root nitrogen and phosphorus cycling. Here, by compiling plant root data from 211 studies in 51 countries, we show that live fine roots have low nitrogen (N) and phosphorus (P), but similar N:P ratios when compared with green leaves. The fine-root N:P ratio differs between biomes and declines exponentially with latitude in roots of all diameter classes. This is in contrast to previous reports of a linear latitudinal decline in green leaf N:P, but consistent with nonlinear declines in leaf litter N:P. Whereas the latitudinal N:P decline in both roots and leaves reflects collective influences of climate, soil age and weathering, differences in the shape of the response function may be a result of their different N and P use strategies.

  12. Amelioration of root-knot disease of lady's finger plants by potentized Cina and Santonin.

    PubMed

    Sukul, N C; Ghosh, S; Sukul, A; Sinhababu, S P

    2006-07-01

    Lady's finger plants (Hibiscus esculentus), grown in pots, were inoculated with the second-stage larvae (76+/-6) of root-knot nematodes Meloidogyne incognita, starting 7 days later they were treated with Cina 30c, Santonin 30c or Ethanol 30c by foliar spray for 10 consecutive days. The drugs in 90% ethanol were diluted with distilled water 1:1000 before application on plants. Thirty days after the last treatment the plants were uprooted. Cina 30c and Santonin 30c reduced nematode infestation of plants significantly in terms of root-gall number, root-protein content and nematode population in roots. Santonin 30c reduced root water content. Santonin 30c may have influenced the water channel proteins of root tissues thereby altering the water contents of roots. The reduced water content in roots might have adversely affected the root-knot nematodes and thus reduced nematode infestation. Ethanol 30c also has some effect on treated plants.

  13. Silicon enhanced salt tolerance by improving the root water uptake and decreasing the ion toxicity in cucumber

    PubMed Central

    Wang, Shiwen; Liu, Peng; Chen, Daoqian; Yin, Lina; Li, Hongbing; Deng, Xiping

    2015-01-01

    Although the effects of silicon application on enhancing plant salt tolerance have been widely investigated, the underlying mechanism has remained unclear. In this study, seedlings of cucumber, a medium silicon accumulator plant, grown in 0.83 mM silicon solution for 2 weeks were exposed to 65 mM NaCl solution for another 1 week. The dry weight and shoot/root ratio were reduced by salt stress, but silicon application significantly alleviated these decreases. The chlorophyll concentration, net photosynthetic rate, transpiration rate and leaf water content were higher in plants treated with silicon than in untreated plants under salt stress conditions. Further investigation showed that salt stress decreased root hydraulic conductance (Lp), but that silicon application moderated this salt-induced decrease in Lp. The higher Lp in silicon-treated plants may account for the superior plant water balance. Moreover, silicon application significantly decreased Na+ concentration in the leaves while increasing K+ concentration. Simultaneously, both free and conjugated types of polyamines were maintained at high levels in silicon-treated plants, suggesting that polyamines may be involved in the ion toxicity. Our results indicate that silicon enhances the salt tolerance of cucumber through improving plant water balance by increasing the Lp and reducing Na+ content by increasing polyamine accumulation. PMID:26442072

  14. Classroom Modified Split-Root Technique and Its Application in a Plant Habitat Selection Experiment at the College Level

    ERIC Educational Resources Information Center

    Elliott, Shannon S.; Winter, Peggy A.

    2011-01-01

    The split-root technique produces a plant with two equal root masses. Traditionally, the two root masses of the single plant are cultivated in adjacent pots with or without roots from competitors for the purpose of elucidating habitat preferences. We have tailored this technology for the classroom, adjusting protocols to match resources and time…

  15. Legume presence reduces the decomposition rate of non-legume roots, role of plant traits?

    NASA Astrophysics Data System (ADS)

    De Deyn, Gerlinde B.; Saar, Sirgi; Barel, Janna; Semchenko, Marina

    2016-04-01

    Plant litter traits are known to play an important role in the rate of litter decomposition and mineralization, both for aboveground and belowground litter. However also the biotic and abiotic environment in which the litter decomposes plays a significant role in the rate of decomposition. The presence of living plants may accelerate litter decomposition rates via a priming effects. The size of this effect is expected to be related to the traits of the litter. In this study we focus on root litter, given that roots and their link to ecosystem processes have received relatively little attention in trait-based research. To test the effect of a growing legume plant on root decomposition and the role of root traits in this we used dead roots of 7 different grassland species (comprising grasses, a forb and legumes), determined their C, N, P content and quantified litter mass loss after eight weeks of incubation in soil with and without white clover. We expected faster root decomposition with white clover, especially for root litter with low N content. In contrast we found slower decomposition of grass and forb roots which were poor in N (negative priming) in presence of white clover, while decomposition rates of legume roots were not affected by the presence of white clover. Overall we found that root decomposition can be slowed down in the presence of a living plant and that this effect depends on the traits of the decomposing roots, with a pronounced reduction in root litter poor in N and P, but not in the relatively nutrient-rich legume root litters. The negative priming effect of legume plants on non-legume litter decomposition may have resulted from preferential substrate utilisation by soil microbes.

  16. Rhizosphere microbial community structure in relation to root location and plant iron nutritional status.

    PubMed

    Yang, C H; Crowley, D E

    2000-01-01

    Root exudate composition and quantity vary in relation to plant nutritional status, but the impact of the differences on rhizosphere microbial communities is not known. To examine this question, we performed an experiment with barley (Hordeum vulgare) plants under iron-limiting and iron-sufficient growth conditions. Plants were grown in an iron-limiting soil in root box microcosms. One-half of the plants were treated with foliar iron every day to inhibit phytosiderophore production and to alter root exudate composition. After 30 days, the bacterial communities associated with different root zones, including the primary root tips, nonelongating secondary root tips, sites of lateral root emergence, and older roots distal from the tip, were characterized by using 16S ribosomal DNA (rDNA) fingerprints generated by PCR-denaturing gradient gel electrophoresis (DGGE). Our results showed that the microbial communities associated with the different root locations produced many common 16S rDNA bands but that the communities could be distinguished by using correspondence analysis. Approximately 40% of the variation between communities could be attributed to plant iron nutritional status. A sequence analysis of clones generated from a single 16S rDNA band obtained at all of the root locations revealed that there were taxonomically different species in the same band, suggesting that the resolving power of DGGE for characterization of community structure at the species level is limited. Our results suggest that the bacterial communities in the rhizosphere are substantially different in different root zones and that a rhizosphere community may be altered by changes in root exudate composition caused by changes in plant iron nutritional status.

  17. Rhizosphere Microbial Community Structure in Relation to Root Location and Plant Iron Nutritional Status

    PubMed Central

    Yang, Ching-Hong; Crowley, David E.

    2000-01-01

    Root exudate composition and quantity vary in relation to plant nutritional status, but the impact of the differences on rhizosphere microbial communities is not known. To examine this question, we performed an experiment with barley (Hordeum vulgare) plants under iron-limiting and iron-sufficient growth conditions. Plants were grown in an iron-limiting soil in root box microcosms. One-half of the plants were treated with foliar iron every day to inhibit phytosiderophore production and to alter root exudate composition. After 30 days, the bacterial communities associated with different root zones, including the primary root tips, nonelongating secondary root tips, sites of lateral root emergence, and older roots distal from the tip, were characterized by using 16S ribosomal DNA (rDNA) fingerprints generated by PCR-denaturing gradient gel electrophoresis (DGGE). Our results showed that the microbial communities associated with the different root locations produced many common 16S rDNA bands but that the communities could be distinguished by using correspondence analysis. Approximately 40% of the variation between communities could be attributed to plant iron nutritional status. A sequence analysis of clones generated from a single 16S rDNA band obtained at all of the root locations revealed that there were taxonomically different species in the same band, suggesting that the resolving power of DGGE for characterization of community structure at the species level is limited. Our results suggest that the bacterial communities in the rhizosphere are substantially different in different root zones and that a rhizosphere community may be altered by changes in root exudate composition caused by changes in plant iron nutritional status. PMID:10618246

  18. Plant growth-promoting potential of endophytic bacteria isolated from roots of coastal sand dune plants.

    PubMed

    Shin, Dong-Sung; Park, Myung Soo; Jung, Sera; Lee, Myoung Sook; Lee, Kang Hyun; Bae, Kyung Sook; Kim, Seung Bum

    2007-08-01

    Endophytic bacteria associated with the roots of coastal sand dune plants were isolated, taxonomically characterized, and tested for their plant growth-promoting activities. Ninety-one endophytic bacterial isolates were collected and assigned to 17 different genera of 6 major bacterial phyla based on partial 16S rDNA sequence analyses. Gammaproteobacteria represented the majority of the isolates (65.9%), and members of Pseudomonas constituted 49.5% of the total isolates. When testing for antagonism towards plant pathogenic fungi, 25 strains were antagonistic towards Rhizoctonia solani, 57 strains were antagonistic towards Pythium ultimum, 53 strains were antagonistic towards Fusarium oxysporum, and 41 strains were antagonistic towards Botrytis cinerea. Seven strains were shown to produce indole acetic acid (IAA), 33 to produce siderophores, 23 to produce protease, 37 to produce pectinase, and 38 to produce chitinase. The broadest spectra of activities were observed among the Pseudomonas strains, indicating outstanding plant growth-promoting potential. The isolates from C. kobomugi and M. sibirica also exhibited good plant growth-promoting potential. The correlations among individual plant growth-promoting activities were examined using phi coefficients, and the resulting data indicated that the production of protease, pectinase, chitinase, and siderophores was highly related.

  19. COMPREHENSIVE CHEMICAL PROFILING OF GRAMINEOUS PLANT ROOT EXUDATES USING HIGH-RESOLUTION NMR AND MS. (R825433C007)

    EPA Science Inventory

    Root exudates released into soil have important functions in mobilizing metal micronutrients and for causing selective enrichment of plant beneficial soil micro-organisms that colonize the rhizosphere. Analysis of plant root exudates typically has involved chromatographic meth...

  20. COMPREHENSIVE CHEMICAL PROFILING OF GRAMINEOUS PLANT ROOT EXUDATES USING HIGH-RESOLUTION NMR AND MS. (R825433C007)

    EPA Science Inventory

    Root exudates released into soil have important functions in mobilizing metal micronutrients and for causing selective enrichment of plant beneficial soil micro-organisms that colonize the rhizosphere. Analysis of plant root exudates typically has involved chromatographic meth...

  1. Can diversity in root architecture explain plant water use efficiency? A modeling study

    PubMed Central

    Tron, Stefania; Bodner, Gernot; Laio, Francesco; Ridolfi, Luca; Leitner, Daniel

    2015-01-01

    Drought stress is a dominant constraint to crop production. Breeding crops with adapted root systems for effective uptake of water represents a novel strategy to increase crop drought resistance. Due to complex interaction between root traits and high diversity of hydrological conditions, modeling provides important information for trait based selection. In this work we use a root architecture model combined with a soil-hydrological model to analyze whether there is a root system ideotype of general adaptation to drought or water uptake efficiency of root systems is a function of specific hydrological conditions. This was done by modeling transpiration of 48 root architectures in 16 drought scenarios with distinct soil textures, rainfall distributions, and initial soil moisture availability. We find that the efficiency in water uptake of root architecture is strictly dependent on the hydrological scenario. Even dense and deep root systems are not superior in water uptake under all hydrological scenarios. Our results demonstrate that mere architectural description is insufficient to find root systems of optimum functionality. We find that in environments with sufficient rainfall before the growing season, root depth represents the key trait for the exploration of stored water, especially in fine soils. Root density, instead, especially near the soil surface, becomes the most relevant trait for exploiting soil moisture when plant water supply is mainly provided by rainfall events during the root system development. We therefore concluded that trait based root breeding has to consider root systems with specific adaptation to the hydrology of the target environment. PMID:26412932

  2. Mechanical Failure of Fine Root Cortical Cells Initiates Plant Hydraulic Decline during Drought.

    PubMed

    Cuneo, Italo F; Knipfer, Thorsten; Brodersen, Craig R; McElrone, Andrew J

    2016-11-01

    Root systems perform the crucial task of absorbing water from the soil to meet the demands of a transpiring canopy. Roots are thought to operate like electrical fuses, which break when carrying an excessive load under conditions of drought stress. Yet the exact site and sequence of this dysfunction in roots remain elusive. Using in vivo x-ray computed microtomography, we found that drought-induced mechanical failure (i.e. lacunae formation) in fine root cortical cells is the initial and primary driver of reduced fine root hydraulic conductivity (Lpr) under mild to moderate drought stress. Cortical lacunae started forming under mild drought stress (-0.6 MPa Ψstem), coincided with a dramatic reduction in Lpr, and preceded root shrinkage or significant xylem embolism. Only under increased drought stress was embolism formation observed in the root xylem, and it appeared first in the fine roots (50% loss of hydraulic conductivity [P50] reached at -1.8 MPa) and then in older, coarse roots (P50 = -3.5 MPa). These results suggest that cortical cells in fine roots function like hydraulic fuses that decouple plants from drying soil, thus preserving the hydraulic integrity of the plant's vascular system under early stages of drought stress. Cortical lacunae formation led to permanent structural damage of the root cortex and nonrecoverable Lpr, pointing to a role in fine root mortality and turnover under drought stress.

  3. Hyperaccumulation of nickel by hairy roots of alyssum species: comparison with whole regenerated plants.

    PubMed

    Nedelkoska, T V; Doran, P M

    2001-01-01

    Hairy roots were used to investigate nickel uptake by the hyperaccumulator species, Alyssum bertolonii, A. tenium, and A. troodii. The Ni biosorption capacity of A. tenium hairy roots was lower than for other types of biomass such as bacteria and algae; in short-term (9-h) equilibrium studies, the highest Ni content measured in the roots was 17 500 microg g(-1) dry weight at a liquid concentration of about 4000 ppm. Using long-term hairy root cultures, it was demonstrated that Ni tolerance and hyperaccumulation do not necessarily depend on the presence of shoots or root-shoot translocation. A. bertolonii hairy roots remained healthy in appearance and continued to grow in the presence of 20-100 ppm Ni, accumulating up to 7200 microg g(-1) dry weight Ni. In contrast, hairy roots of Nicotiana tabacum turned dark brown at 20 ppm Ni and growth was negligible. The ability to grow at high external Ni concentrations allowed hyperaccumulator hairy roots to remove much greater amounts of heavy metals from the culture liquid than nonhyperaccumulator hairy roots, even though biomass Ni concentrations were similar. Although hairy roots proved to be a useful tool for investigating Ni hyperaccumulation, there were significant differences in the Ni uptake capacity of hairy roots and whole plants. Regenerated plants of A. tenium were much more tolerant of Ni and capable of accumulating higher Ni concentrations than hairy roots of this species.

  4. Uptake, distribution, and metabolism of four organic chemicals by soybean plants and barley roots

    SciTech Connect

    McFarlane, C.; Nolt, C.; Wickliff, C.; Pfleeger, T.; Shimabuku, R.

    1987-01-01

    The uptake of bromacil, dichlorobenzonitrile (DCBN), nitrobenzene (NB) and dinitrobenzene (DNB) was studied in isolated barley roots and mature soybean plants. The uptake rate constants for soybean plants were in the order of DCBN = bromacil < NB < DNB. The same pattern was evident for the root tissue test, except for DNB. Metabolism of the (14)C-labeled chemicals indicated that DCBN was metabolized in the leaves but not in the roots. DNB was metabolized in the roots, and bromacil remained primarily as parent compound. A method for obtaining uptake rate constants is described.

  5. Beta-carboline and quinoline alkaloids in root cultures and intact plants of Peganum harmala.

    PubMed

    Zayed, Rawin; Wink, Michael

    2005-01-01

    Alkaloid profiles of root and shoot cultures, seedlings and mature plants were analysed by capillary GLC and GLC-MS. beta-Carboline alkaloids, such as harmine, harmaline dominate in normal and root cultures transformed by Agrobacterium rhizogenes, as well as in roots and fruits of the plant. In shoots, flowers and shoot cultures quinoline alkaloids such as peganine, deoxypeganine, vasicinone and deoxyvasicinone widely replace the beta-carboline alkaloids. In root cultures, the formation of beta-carboline alkaloids can be induced by methyljasmonate and several other elicitors indicating that these alkaloids are part of the reactive chemical defence system of Peganum harmala.

  6. Field performance of Quercus bicolor established as repeatedly air-root-pruned container and bareroot planting stock

    Treesearch

    J.W." Jerry" Van Sambeek; Larry D. Godsey; William D. Walter; Harold E. Garrett; John P. Dwyer

    2016-01-01

    Benefits of repeated air-root-pruning of seedlings when stepping up to progressively larger containers include excellent lateral root distribution immediately below the root collar and an exceptionally fibrous root ball. To evaluate long-term field performance of repeatedly air-root-pruned container stock, three plantings of swamp white oak (Quercus bicolor...

  7. A manifold learning based identification of latent variations in root cross sections of plants

    NASA Astrophysics Data System (ADS)

    Chakravarty, Sumit; Banerjee, Madhushri

    2012-06-01

    Currently a lot of plant biology research focuses on understanding the genetic, physiological, and ecology of plants. Root is an important organ for plant to uptake nutrient and water from the surrounding soil. The capability of plant to obtain nutrient and water is closely related to root physiology. Quantitative measurement and analysis of plant root architecture parameters are very important for understanding and study growth of plant. A fundamental aim of developmental plant root biology is to understand how the three-dimensional morphology of plant roots arises through cellular mechanisms. However, traditional anatomical studies of plant development have mainly relied on two-dimensional images. Though this may be sufficient for some aspects of plant biology, deeper understanding of plant growth and function increasingly requires at least some amount of three dimensional measures and use chemical staining as a technique to bring pseudo structure and segmentation to the cross section image data. Thus parameters like uniformity of illumination and thickness of the specimen then becomes critical. Unfortunately these are also the causes of major variations. The variation of thickness of specimen can be interpreted as an effect which increases the latent dimensionality of the data. Addressing the variability due to specimen thickness can then be viewed in a manifold learning framework, wherein it is assumed that the data of interest lies on an embedded manifold within the higher-dimensional space and can be visualized in low dimensional space, using manifold learning constraints.

  8. Systems biology for enhanced plant nitrogen nutrition.

    PubMed

    Gutiérrez, Rodrigo A

    2012-06-29

    Nitrogen (N)-based fertilizers increase agricultural productivity but have detrimental effects on the environment and human health. Research is generating improved understanding of the signaling components plants use to sense N and regulate metabolism, physiology, and growth and development. However, we still need to integrate these regulatory factors into signal transduction pathways and connect them to downstream response pathways. Systems biology approaches facilitate identification of new components and N-regulatory networks linked to other plant processes. A holistic view of plant N nutrition should open avenues to translate this knowledge into effective strategies to improve N-use efficiency and enhance crop production systems for more sustainable agricultural practices.

  9. Different Bacterial Populations Associated with the Roots and Rhizosphere of Rice Incorporate Plant-Derived Carbon

    PubMed Central

    Hernández, Marcela; Yuan, Quan; Conrad, Ralf

    2015-01-01

    Microorganisms associated with the roots of plants have an important function in plant growth and in soil carbon sequestration. Rice cultivation is the second largest anthropogenic source of atmospheric CH4, which is a significant greenhouse gas. Up to 60% of fixed carbon formed by photosynthesis in plants is transported below ground, much of it as root exudates that are consumed by microorganisms. A stable isotope probing (SIP) approach was used to identify microorganisms using plant carbon in association with the roots and rhizosphere of rice plants. Rice plants grown in Italian paddy soil were labeled with 13CO2 for 10 days. RNA was extracted from root material and rhizosphere soil and subjected to cesium gradient centrifugation followed by 16S rRNA amplicon pyrosequencing to identify microorganisms enriched with 13C. Thirty operational taxonomic units (OTUs) were labeled and mostly corresponded to Proteobacteria (13 OTUs) and Verrucomicrobia (8 OTUs). These OTUs were affiliated with the Alphaproteobacteria, Betaproteobacteria, and Deltaproteobacteria classes of Proteobacteria and the “Spartobacteria” and Opitutae classes of Verrucomicrobia. In general, different bacterial groups were labeled in the root and rhizosphere, reflecting different physicochemical characteristics of these locations. The labeled OTUs in the root compartment corresponded to a greater proportion of the 16S rRNA sequences (∼20%) than did those in the rhizosphere (∼4%), indicating that a proportion of the active microbial community on the roots greater than that in the rhizosphere incorporated plant-derived carbon within the time frame of the experiment. PMID:25616793

  10. Chemical signals from plants previously infected with root knot nematodes affect behavior of infective juvenile root knot nematodes

    USDA-ARS?s Scientific Manuscript database

    Nematodes are a worldwide problem in agriculture, with losses estimated to $100 billion per year in the US. Damage caused by root-knot nematodes (Meloidogyne spp.) (RKN) disrupts the flow of water and nutrients to the plant and increases the plant’s vulnerability to other pathogens. While studies ...

  11. Exploring the transfer of recent plant photosynthates to soil microbes: mycorrhizal pathway vs direct root exudation

    PubMed Central

    Kaiser, Christina; Kilburn, Matt R; Clode, Peta L; Fuchslueger, Lucia; Koranda, Marianne; Cliff, John B; Solaiman, Zakaria M; Murphy, Daniel V

    2015-01-01

    Plants rapidly release photoassimilated carbon (C) to the soil via direct root exudation and associated mycorrhizal fungi, with both pathways promoting plant nutrient availability. This study aimed to explore these pathways from the root's vascular bundle to soil microbial communities. Using nanoscale secondary ion mass spectrometry (NanoSIMS) imaging and 13C-phospho- and neutral lipid fatty acids, we traced in-situ flows of recently photoassimilated C of 13CO2-exposed wheat (Triticum aestivum) through arbuscular mycorrhiza (AM) into root- and hyphae-associated soil microbial communities. Intraradical hyphae of AM fungi were significantly 13C-enriched compared to other root-cortex areas after 8 h of labelling. Immature fine root areas close to the root tip, where AM features were absent, showed signs of passive C loss and co-location of photoassimilates with nitrogen taken up from the soil solution. A significant and exclusively fresh proportion of 13C-photosynthates was delivered through the AM pathway and was utilised by different microbial groups compared to C directly released by roots. Our results indicate that a major release of recent photosynthates into soil leave plant roots via AM intraradical hyphae already upstream of passive root exudations. AM fungi may act as a rapid hub for translocating fresh plant C to soil microbes. PMID:25382456

  12. Exploring the transfer of recent plant photosynthates to soil microbes: mycorrhizal pathway vs direct root exudation.

    PubMed

    Kaiser, Christina; Kilburn, Matt R; Clode, Peta L; Fuchslueger, Lucia; Koranda, Marianne; Cliff, John B; Solaiman, Zakaria M; Murphy, Daniel V

    2015-03-01

    Plants rapidly release photoassimilated carbon (C) to the soil via direct root exudation and associated mycorrhizal fungi, with both pathways promoting plant nutrient availability. This study aimed to explore these pathways from the root's vascular bundle to soil microbial communities. Using nanoscale secondary ion mass spectrometry (NanoSIMS) imaging and (13) C-phospho- and neutral lipid fatty acids, we traced in-situ flows of recently photoassimilated C of (13) CO2 -exposed wheat (Triticum aestivum) through arbuscular mycorrhiza (AM) into root- and hyphae-associated soil microbial communities. Intraradical hyphae of AM fungi were significantly (13) C-enriched compared to other root-cortex areas after 8 h of labelling. Immature fine root areas close to the root tip, where AM features were absent, showed signs of passive C loss and co-location of photoassimilates with nitrogen taken up from the soil solution. A significant and exclusively fresh proportion of (13) C-photosynthates was delivered through the AM pathway and was utilised by different microbial groups compared to C directly released by roots. Our results indicate that a major release of recent photosynthates into soil leave plant roots via AM intraradical hyphae already upstream of passive root exudations. AM fungi may act as a rapid hub for translocating fresh plant C to soil microbes. © 2014 The Authors New Phytologist © 2014 New Phytologist Trust.

  13. Quantitative 3D Analysis of Plant Roots Growing in Soil Using Magnetic Resonance Imaging1[OPEN

    PubMed Central

    Kochs, Johannes; Pflugfelder, Daniel

    2016-01-01

    Precise measurements of root system architecture traits are an important requirement for plant phenotyping. Most of the current methods for analyzing root growth require either artificial growing conditions (e.g. hydroponics), are severely restricted in the fraction of roots detectable (e.g. rhizotrons), or are destructive (e.g. soil coring). On the other hand, modalities such as magnetic resonance imaging (MRI) are noninvasive and allow high-quality three-dimensional imaging of roots in soil. Here, we present a plant root imaging and analysis pipeline using MRI together with an advanced image visualization and analysis software toolbox named NMRooting. Pots up to 117 mm in diameter and 800 mm in height can be measured with the 4.7 T MRI instrument used here. For 1.5 l pots (81 mm diameter, 300 mm high), a fully automated system was developed enabling measurement of up to 18 pots per day. The most important root traits that can be nondestructively monitored over time are root mass, length, diameter, tip number, and growth angles (in two-dimensional polar coordinates) and spatial distribution. Various validation measurements for these traits were performed, showing that roots down to a diameter range between 200 μm and 300 μm can be quantitatively measured. Root fresh weight correlates linearly with root mass determined by MRI. We demonstrate the capabilities of MRI and the dedicated imaging pipeline in experimental series performed on soil-grown maize (Zea mays) and barley (Hordeum vulgare) plants. PMID:26729797

  14. Quantitative 3D Analysis of Plant Roots Growing in Soil Using Magnetic Resonance Imaging.

    PubMed

    van Dusschoten, Dagmar; Metzner, Ralf; Kochs, Johannes; Postma, Johannes A; Pflugfelder, Daniel; Bühler, Jonas; Schurr, Ulrich; Jahnke, Siegfried

    2016-03-01

    Precise measurements of root system architecture traits are an important requirement for plant phenotyping. Most of the current methods for analyzing root growth require either artificial growing conditions (e.g. hydroponics), are severely restricted in the fraction of roots detectable (e.g. rhizotrons), or are destructive (e.g. soil coring). On the other hand, modalities such as magnetic resonance imaging (MRI) are noninvasive and allow high-quality three-dimensional imaging of roots in soil. Here, we present a plant root imaging and analysis pipeline using MRI together with an advanced image visualization and analysis software toolbox named NMRooting. Pots up to 117 mm in diameter and 800 mm in height can be measured with the 4.7 T MRI instrument used here. For 1.5 l pots (81 mm diameter, 300 mm high), a fully automated system was developed enabling measurement of up to 18 pots per day. The most important root traits that can be nondestructively monitored over time are root mass, length, diameter, tip number, and growth angles (in two-dimensional polar coordinates) and spatial distribution. Various validation measurements for these traits were performed, showing that roots down to a diameter range between 200 μm and 300 μm can be quantitatively measured. Root fresh weight correlates linearly with root mass determined by MRI. We demonstrate the capabilities of MRI and the dedicated imaging pipeline in experimental series performed on soil-grown maize (Zea mays) and barley (Hordeum vulgare) plants.

  15. An assessment of models that predict soil reinforcement by plant roots

    NASA Astrophysics Data System (ADS)

    Hallett, P. D.; Loades, K. W.; Mickovski, S.; Bengough, A. G.; Bransby, M. F.; Davies, M. C. R.; Sonnenberg, R.

    2009-04-01

    Predicting soil reinforcement by plant roots is fraught with uncertainty because of spatio-temporal variability, the mechanical complexity of roots and soil, and the limitations of existing models. In this study, the validity of root-reinforcement models was tested with data from numerous controlled laboratory tests of both fibrous and woody root systems. By using pot experiments packed with homogeneous soil, each planted with one plant species and grown in glasshouses with controlled water and temperature regimes, spatio-temporal variability was reduced. After direct shear testing to compare the mechanical behaviour of planted versus unplanted samples, the size distribution of roots crossing the failure surface was measured accurately. Separate tensile tests on a wide range of root sizes for each test series provided information on the scaling of root strength and stiffness, which was fitted using power-law relationships. These data were used to assess four root-reinforcement models: (1) Wu et al.'s (1979) root-reinforcement model, (2) Rip-Root fibre bundle model (FBM) proposed by Pollen & Simon (2005), (3) a stress-based FBM and (4) a strain-based FBM. For both fibrous (barley) and woody (willow) root systems, all of the FBMs provided a better prediction of reinforcement than Wu's root-reinforcement model. As FBMs simulate progressive failure of roots, they reflect reality better than the Wu model which assumes all roots break (and contribute to increased shear strength) simultaneously. However, all of the FBMs contain assumptions about the distribution of the applied load within the bundle of roots and the failure criterion. The stress-based FBM assumes the same stiffness for different sized roots, resulting in progressive failure from the largest to smallest roots. This is not observed in testing where the smallest roots fail first. The Rip-Root FBM predicts failure from smallest to largest roots, but the distribution of load between different sized roots is

  16. The Response of the Root Apex in Plant Adaptation to Iron Heterogeneity in Soil

    PubMed Central

    Li, Guangjie; Kronzucker, Herbert J.; Shi, Weiming

    2016-01-01

    Iron (Fe) is an essential micronutrient for plant growth and development, and is frequently limiting. By contrast, over-accumulation of Fe in plant tissues leads to toxicity. In soils, the distribution of Fe is highly heterogeneous. To cope with this heterogeneity, plant roots engage an array of adaptive responses to adjust their morphology and physiology. In this article, we review root morphological and physiological changes in response to low- and high-Fe conditions and highlight differences between these responses. We especially focus on the role of the root apex in dealing with the stresses resulting from Fe shortage and excess. PMID:27047521

  17. The qid74 gene from Trichoderma harzianum has a role in root architecture and plant biofertilization.

    PubMed

    Samolski, Ilanit; Rincón, Ana M; Pinzón, Luz Mary; Viterbo, Ada; Monte, Enrique

    2012-01-01

    The Trichoderma harzianum qid74 gene encodes a cysteine-rich cell wall protein that has an important role in adherence to hydrophobic surfaces and cellular protection; this gene was upregulated in Trichoderma high-density oligonucleotide (HDO) microarrays in interaction with tomato roots. Using a collection of qid74-overexpressing and disrupted mutants the role of this gene in cucumber and tomato root architecture was analysed in hydroponic and soil systems under greenhouse conditions. No significant differences were found in the pattern of root colonization and the length of primary roots of cucumber or tomato plants inoculated by T. harzianum CECT 2413 wild-type (wt) strain or any of the qid74 transformants. However, compared to the wt treatment, lateral roots were significantly longer in plants inoculated with the overexpressing transformants, and shorter in those treated with the disruptant strains. Microscopic observations revealed more and longer secondary root hairs in cucumber plants treated with the qid74-overexpressing mutants and fewer and shorter hairs in roots treated with qid74-disrupted transformants, compared to those observed in plants inoculated with the wt strain. qid74-induced modifications in root architecture increased the total absorptive surface, facilitating nutrient uptake and translocation of nutrients in the shoots, resulting in increased plant biomass through an efficient use of NPK and micronutrients.

  18. Inoculation effects on root-colonizing arbuscular mycorrhizal fungal communities spread beyond directly inoculated plants.

    PubMed

    Janoušková, Martina; Krak, Karol; Vosátka, Miroslav; Püschel, David; Štorchová, Helena

    2017-01-01

    Inoculation with arbuscular mycorrhizal fungi (AMF) may improve plant performance at disturbed sites, but inoculation may also suppress root colonization by native AMF and decrease the diversity of the root-colonizing AMF community. This has been shown for the roots of directly inoculated plants, but little is known about the stability of inoculation effects, and to which degree the inoculant and the inoculation-induced changes in AMF community composition spread into newly emerging seedlings that were not in direct contact with the introduced propagules. We addressed this topic in a greenhouse experiment based on the soil and native AMF community of a post-mining site. Plants were cultivated in compartmented pots with substrate containing the native AMF community, where AMF extraradical mycelium radiating from directly inoculated plants was allowed to inoculate neighboring plants. The abundances of the inoculated isolate and of native AMF taxa were monitored in the roots of the directly inoculated plants and the neighboring plants by quantitative real-time PCR. As expected, inoculation suppressed root colonization of the directly inoculated plants by other AMF taxa of the native AMF community and also by native genotypes of the same species as used for inoculation. In the neighboring plants, high abundance of the inoculant and the suppression of native AMF were maintained. Thus, we demonstrate that inoculation effects on native AMF propagate into plants that were not in direct contact with the introduced inoculum, and are therefore likely to persist at the site of inoculation.

  19. Identification and chemical enhancement of two ornamental plants for phytoremediation.

    PubMed

    Liu, Jia-Nv; Zhou, Qi-Xing; Sun, Ting; Ma, Lena Q; Wang, Song

    2008-03-01

    With an increase in the contamination of urban areas, more and more attention has been paid to the role of ornamental plants in remedying contaminated soils. Thus, cadmium (Cd) tolerance and accumulation characteristics of Calendula officinalis and Althaea rosea as ornamental plants under the concentration gradient experiment with single Cd, as well as the effect of ethylenegluatarotriacetic acid (EGTA) and sodium dodecyl sulfate (SDS) on their Cd phytoremediation capacity under the chemically enhanced experiment was further investigated. It was showed that they had strong tolerance and accumulation capacity of Cd under single Cd treatments, thus they had great potential to be used for Cd contaminated soil remediation. Furthermore, under chemically enhanced treatments, the great efficiency was found through applying EGTA and SDS, they could not only increase the dry biomass of the plants, but also promote the Cd accumulation in shoots and roots. Particularly, Althaea rosea can be regarded as a potential Cd-hyperaccumulator through applying chemical agents. In conclusion, the two ornamental plants are promising to be used for phytoremediation.

  20. Effects of the Magnetic Resonance Imaging Contrast Agent Gd-DTPA on Plant Growth and Root Imaging in Rice

    PubMed Central

    Liu, Binmei; Wang, Qi; Ni, Xiaoyu; Dong, Yaling; Zhong, Kai; Wu, Yuejin

    2014-01-01

    Although paramagnetic contrast agents have a wide range of applications in medical studies involving magnetic resonance imaging (MRI), these agents are seldom used to enhance MRI images of plant root systems. To extend the application of MRI contrast agents to plant research and to develop related techniques to study root systems, we examined the applicability of the MRI contrast agent Gd-DTPA to the imaging of rice roots. Specifically, we examined the biological effects of various concentrations of Gd-DTPA on rice growth and MRI images. Analysis of electrical conductivity and plant height demonstrated that 5 mmol Gd-DTPA had little impact on rice in the short-term. The results of signal intensity and spin-lattice relaxation time (T1) analysis suggested that 5 mmol Gd-DTPA was the appropriate concentration for enhancing MRI signals. In addition, examination of the long-term effects of Gd-DTPA on plant height showed that levels of this compound up to 5 mmol had little impact on rice growth and (to some extent) increased the biomass of rice. PMID:24945975

  1. Effects of the magnetic resonance imaging contrast agent Gd-DTPA on plant growth and root imaging in rice.

    PubMed

    Liu, Zan; Qian, Junchao; Liu, Binmei; Wang, Qi; Ni, Xiaoyu; Dong, Yaling; Zhong, Kai; Wu, Yuejin

    2014-01-01

    Although paramagnetic contrast agents have a wide range of applications in medical studies involving magnetic resonance imaging (MRI), these agents are seldom used to enhance MRI images of plant root systems. To extend the application of MRI contrast agents to plant research and to develop related techniques to study root systems, we examined the applicability of the MRI contrast agent Gd-DTPA to the imaging of rice roots. Specifically, we examined the biological effects of various concentrations of Gd-DTPA on rice growth and MRI images. Analysis of electrical conductivity and plant height demonstrated that 5 mmol Gd-DTPA had little impact on rice in the short-term. The results of signal intensity and spin-lattice relaxation time (T1) analysis suggested that 5 mmol Gd-DTPA was the appropriate concentration for enhancing MRI signals. In addition, examination of the long-term effects of Gd-DTPA on plant height showed that levels of this compound up to 5 mmol had little impact on rice growth and (to some extent) increased the biomass of rice.

  2. Plant roots: understanding structure and function in an ocean of complexity

    PubMed Central

    Ryan, Peter R.; Delhaize, Emmanuel; Watt, Michelle; Richardson, Alan E.

    2016-01-01

    Background The structure and function of plant roots and their interactions with soil are exciting scientific frontiers that will ultimately reveal much about our natural systems, global water and mineral and carbon cycles, and help secure food supplies into the future. This Special Issue presents a collection of papers that address topics at the forefront of our understanding of root biology. Scope These papers investigate how roots cope with drought, nutrient deficiencies, toxicities and soil compaction as well as the interactions that roots have with soil microorganisms. Roots of model plant species, annual crops and perennial species are studied in short-term experiments through to multi-year trials. Spatial scales range from the gene up to farming systems and nutrient cycling. The diverse, integrated approaches described by these studies encompass root genetics as applied to soil management, as well as documenting the signalling processes occurring between roots and shoots and between roots and soil. Conclusions This Special Issue on roots presents invited reviews and research papers covering a span of topics ranging from fundamental aspects of anatomy, growth and water uptake to roots in crop and pasture systems. Understanding root structure and function and adaptation to the abiotic and biotic stresses encountered in field conditions is important for sustainable agricultural production and better management of natural systems.

  3. Enhancement of reproductive heat tolerance in plants

    USDA-ARS?s Scientific Manuscript database

    The current study investigated the enhancement of plant reproductive heat tolerance through the use of a gene encoding the Arabidopsis thaliana heat shock protein 101 (AtHSP101) not normally expressed in pollen but reported to play a crucial role in vegetative thermotolerance. The Arabidopsis thali...

  4. Stacked propagation: a new way to grow native plants from root cuttings

    Treesearch

    David R. Dreesen; Thomas D. Landis; Jeremy R. Pinto

    2006-01-01

    Stacked propagation is a novel method of growing quaking aspen (Populus tremuloides Michx. [Salicaceae]) and other plants that reproduce from underground stems or root cuttings. Because the mother plant is not damaged, it is particularly well suited for rare plants or those that can’t be propagated by normal methods. Our initial trials indicate that...

  5. A PLANT ROOT SYSTEM ARCHITECTURAL TAXONOMY: A FRAMEWORK FOR ROOT NOMENCLATURE

    USDA-ARS?s Scientific Manuscript database

    Research into root system morphology over the last two centuries, has developed a diverse set of terminologies that are difficult to apply consistently across species and research specialties. In response to a need for better communication, a workshop held by the International Society for Root Rese...

  6. Plant root exudates mediate neighbour recognition and trigger complex behavioural changes.

    PubMed

    Semchenko, Marina; Saar, Sirgi; Lepik, Anu

    2014-11-01

    Some plant species are able to distinguish between neighbours of different genetic identity and attempt to pre-empt resources through root proliferation in the presence of unrelated competitors, but avoid competition with kin. However, studies on neighbour recognition have met with some scepticism because the mechanisms by which plants identify their neighbours have remained unclear. In order to test whether root exudates could mediate neighbour recognition in plants, we performed a glasshouse experiment in which plants of Deschampsia caespitosa were subjected to root exudates collected from potential neighbours of different genetic identities, including siblings and individuals belonging to the same or a different population or species. Our results show that root exudates can carry specific information about the genetic relatedness, population origin and species identity of neighbours, and trigger different responses at the whole root system level and at the level of individual roots in direct contact with locally applied exudates. Increased root density was mainly achieved through changes in morphology rather than biomass allocation, suggesting that plants are able to limit the energetic cost of selfish behaviour. This study reveals a new level of complexity in the ability of plants to interpret and react to their surroundings. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  7. Discovery of novel plant interaction determinants from the genomes of 163 root nodule bacteria

    SciTech Connect

    Seshadri, Rekha; Reeve, Wayne G.; Ardley, Julie K.; Tennessen, Kristin; Woyke, Tanja; Kyrpides, Nikos C.; Ivanova, Natalia N.

    2015-11-20

    Root nodule bacteria (RNB) or “rhizobia” are a type of plant growth promoting bacteria, typified by their ability to fix nitrogen for their plant host, fixing nearly 65% of the nitrogen currently utilized in sustainable agricultural production of legume crops and pastures. In this study, we sequenced the genomes of 110 RNB from diverse hosts and biogeographical regions, and undertook a global exploration of all available RNB genera with the aim of identifying novel genetic determinants of symbiotic association and plant growth promotion. Specifically, we performed a subtractive comparative analysis with non-RNB genomes, employed relevant transcriptomic data, and leveraged phylogenetic distribution patterns and sequence signatures based on known precepts of symbioticand host-microbe interactions. A total of 184 protein families were delineated, including known factors for nodulation and nitrogen fixation, and candidates with previously unexplored functions, for which a role in host-interaction, -regulation, biocontrol, and more, could be posited. Lastly, these analyses expand our knowledge of the RNB purview and provide novel targets for strain improvement in the ultimate quest to enhance plant productivity and agricultural sustainability.

  8. Discovery of Novel Plant Interaction Determinants from the Genomes of 163 Root Nodule Bacteria

    PubMed Central

    Seshadri, Rekha; Reeve, Wayne G.; Ardley, Julie K.; Tennessen, Kristin; Woyke, Tanja; Kyrpides, Nikos C.; Ivanova, Natalia N.

    2015-01-01

    Root nodule bacteria (RNB) or “rhizobia” are a type of plant growth promoting bacteria, typified by their ability to fix nitrogen for their plant host, fixing nearly 65% of the nitrogen currently utilized in sustainable agricultural production of legume crops and pastures. In this study, we sequenced the genomes of 110 RNB from diverse hosts and biogeographical regions, and undertook a global exploration of all available RNB genera with the aim of identifying novel genetic determinants of symbiotic association and plant growth promotion. Specifically, we performed a subtractive comparative analysis with non-RNB genomes, employed relevant transcriptomic data, and leveraged phylogenetic distribution patterns and sequence signatures based on known precepts of symbiotic- and host-microbe interactions. A total of 184 protein families were delineated, including known factors for nodulation and nitrogen fixation, and candidates with previously unexplored functions, for which a role in host-interaction, -regulation, biocontrol, and more, could be posited. These analyses expand our knowledge of the RNB purview and provide novel targets for strain improvement in the ultimate quest to enhance plant productivity and agricultural sustainability. PMID:26584898

  9. Discovery of novel plant interaction determinants from the genomes of 163 root nodule bacteria

    DOE PAGES

    Seshadri, Rekha; Reeve, Wayne G.; Ardley, Julie K.; ...

    2015-11-20

    Root nodule bacteria (RNB) or “rhizobia” are a type of plant growth promoting bacteria, typified by their ability to fix nitrogen for their plant host, fixing nearly 65% of the nitrogen currently utilized in sustainable agricultural production of legume crops and pastures. In this study, we sequenced the genomes of 110 RNB from diverse hosts and biogeographical regions, and undertook a global exploration of all available RNB genera with the aim of identifying novel genetic determinants of symbiotic association and plant growth promotion. Specifically, we performed a subtractive comparative analysis with non-RNB genomes, employed relevant transcriptomic data, and leveraged phylogeneticmore » distribution patterns and sequence signatures based on known precepts of symbioticand host-microbe interactions. A total of 184 protein families were delineated, including known factors for nodulation and nitrogen fixation, and candidates with previously unexplored functions, for which a role in host-interaction, -regulation, biocontrol, and more, could be posited. Lastly, these analyses expand our knowledge of the RNB purview and provide novel targets for strain improvement in the ultimate quest to enhance plant productivity and agricultural sustainability.« less

  10. Influence of Merosesquiterpenoids from Marine Sponges on Seedling Root Growth of Agricultural Plants.

    PubMed

    Chaikina, Elena L; Utkina, Natalia K; Anisimov, Mikhail M

    2016-01-01

    The impact of the merosesquiterpenoids avarol (1), avarone (2), 18-methylaminoavarone (3), melemeleone A (4), isospongiaquinone (5), ilimaquinone (6), and smenoquinone (7), isolated from marine sponges of the Dictyoceratida order, was studied on the root growth of seedlings of buckwheat (Fagopyrumesculentum Moench), wheat (Triticumaestivum L.), soy (Glycine max (L.) Merr.), and barley (Hordeumvulgare L.). Compounds 2and 6 were effective for the root growth of wheat seedlings, compound 3 stimulated the root growth of seedlings of buckwheat and soy, compound 4 affected the roots of barley seedlings, and compound 5 stimulated the root growth of seedlings of buckwheat and barley. Compounds 1 and 7 showed no activity on the root growth of the seedlings of any of the studied plants. The stimulatory effect depends on the chemical structure of the compounds and the type of crop plant.

  11. Experimentally increased nutrient availability at the permafrost thaw front selectively enhances biomass production of deep-rooting subarctic peatland species.

    PubMed

    Keuper, Frida; Dorrepaal, Ellen; van Bodegom, Peter M; van Logtestijn, Richard; Venhuizen, Gemma; van Hal, Jurgen; Aerts, Rien

    2017-10-01

    Climate warming increases nitrogen (N) mineralization in superficial soil layers (the dominant rooting zone) of subarctic peatlands. Thawing and subsequent mineralization of permafrost increases plant-available N around the thaw-front. Because plant production in these peatlands is N-limited, such changes may substantially affect net primary production and species composition. We aimed to identify the potential impact of increased N-availability due to permafrost thawing on subarctic peatland plant production and species performance, relative to the impact of increased N-availability in superficial organic layers. Therefore, we investigated whether plant roots are present at the thaw-front (45 cm depth) and whether N-uptake ((15) N-tracer) at the thaw-front occurs during maximum thaw-depth, coinciding with the end of the growing season. Moreover, we performed a unique 3-year belowground fertilization experiment with fully factorial combinations of deep- (thaw-front) and shallow-fertilization (10 cm depth) and controls. We found that certain species are present with roots at the thaw-front (Rubus chamaemorus) and have the capacity (R. chamaemorus, Eriophorum vaginatum) for N-uptake from the thaw-front between autumn and spring when aboveground tissue is largely senescent. In response to 3-year shallow-belowground fertilization (S) both shallow- (Empetrum hermaphroditum) and deep-rooting species increased aboveground biomass and N-content, but only deep-rooting species responded positively to enhanced nutrient supply at the thaw-front (D). Moreover, the effects of shallow-fertilization and thaw-front fertilization on aboveground biomass production of the deep-rooting species were similar in magnitude (S: 71%; D: 111% increase compared to control) and additive (S + D: 181% increase). Our results show that plant-available N released from thawing permafrost can form a thus far overlooked additional N-source for deep-rooting subarctic plant species and increase their

  12. Plant Roots Increase Bacterivorous Nematode Dispersion through Nonuniform Glass-bead Media

    PubMed Central

    Trap, Jean; Bernard, Laetitia; Brauman, Alain; Pablo, Anne-Laure; Plassard, Claude; Ranoarisoa, Mahafaka Patricia; Blanchart, Eric

    2015-01-01

    Dispersion of bacterivorous nematodes in soil is a crucial ecological process that permits settlement and exploitation of new bacterial-rich patches. Although plant roots, by modifying soil structure, are likely to influence this process, they have so far been neglected. In this study, using an original three-compartment microcosm experimental design and polyvinyl chloride (PVC) bars to mimic plant roots, we tested the ability of roots to improve the dispersion of bacterivorous nematode populations through two wet, nonuniform granular (glass bead) media imitating contrasting soil textures. We showed that artificial roots increased migration time of bacterivorous nematode populations in the small-bead medium, suggesting that plant roots may play an important role in nematode dispersion in fine-textured soils or when soil compaction is high. PMID:26941457

  13. Ethylene supports colonization of plant roots by the mutualistic fungus Piriformospora indica.

    PubMed

    Khatabi, Behnam; Molitor, Alexandra; Lindermayr, Christian; Pfiffi, Stefanie; Durner, Jörg; von Wettstein, Diter; Kogel, Karl-Heinz; Schäfer, Patrick

    2012-01-01

    The mutualistic basidiomycete Piriformospora indica colonizes roots of mono- and dicotyledonous plants, and thereby improves plant health and yield. Given the capability of P. indica to colonize a broad range of hosts, it must be anticipated that the fungus has evolved efficient strategies to overcome plant immunity and to establish a proper environment for nutrient acquisition and reproduction. Global gene expression studies in barley identified various ethylene synthesis and signaling components that were differentially regulated in P. indica-colonized roots. Based on these findings we examined the impact of ethylene in the symbiotic association. The data presented here suggest that P. indica induces ethylene synthesis in barley and Arabidopsis roots during colonization. Moreover, impaired ethylene signaling resulted in reduced root colonization, Arabidopsis mutants exhibiting constitutive ethylene signaling, -synthesis or ethylene-related defense were hyper-susceptible to P. indica. Our data suggest that ethylene signaling is required for symbiotic root colonization by P. indica.

  14. Plant Roots Increase Bacterivorous Nematode Dispersion through Nonuniform Glass-bead Media.

    PubMed

    Trap, Jean; Bernard, Laetitia; Brauman, Alain; Pablo, Anne-Laure; Plassard, Claude; Ranoarisoa, Mahafaka Patricia; Blanchart, Eric

    2015-12-01

    Dispersion of bacterivorous nematodes in soil is a crucial ecological process that permits settlement and exploitation of new bacterial-rich patches. Although plant roots, by modifying soil structure, are likely to influence this process, they have so far been neglected. In this study, using an original three-compartment microcosm experimental design and polyvinyl chloride (PVC) bars to mimic plant roots, we tested the ability of roots to improve the dispersion of bacterivorous nematode populations through two wet, nonuniform granular (glass bead) media imitating contrasting soil textures. We showed that artificial roots increased migration time of bacterivorous nematode populations in the small-bead medium, suggesting that plant roots may play an important role in nematode dispersion in fine-textured soils or when soil compaction is high.

  15. Ethylene Supports Colonization of Plant Roots by the Mutualistic Fungus Piriformospora indica

    PubMed Central

    Khatabi, Behnam; Molitor, Alexandra; Lindermayr, Christian; Pfiffi, Stefanie; Durner, Jörg; von Wettstein, Diter; Kogel, Karl-Heinz; Schäfer, Patrick

    2012-01-01

    The mutualistic basidiomycete Piriformospora indica colonizes roots of mono- and dicotyledonous plants, and thereby improves plant health and yield. Given the capability of P. indica to colonize a broad range of hosts, it must be anticipated that the fungus has evolved efficient strategies to overcome plant immunity and to establish a proper environment for nutrient acquisition and reproduction. Global gene expression studies in barley identified various ethylene synthesis and signaling components that were differentially regulated in P. indica-colonized roots. Based on these findings we examined the impact of ethylene in the symbiotic association. The data presented here suggest that P. indica induces ethylene synthesis in barley and Arabidopsis roots during colonization. Moreover, impaired ethylene signaling resulted in reduced root colonization, Arabidopsis mutants exhibiting constitutive ethylene signaling, -synthesis or ethylene-related defense were hyper-susceptible to P. indica. Our data suggest that ethylene signaling is required for symbiotic root colonization by P. indica. PMID:22536394

  16. Plant Functional Traits Associated with Mycorrhizal Root Foraging in Arbuscular Mycorrhizal and Ectomycorrhizal Trees

    NASA Astrophysics Data System (ADS)

    Eissenstat, D. M.; Chen, W.; Cheng, L.; Liu, B.; Koide, R. T.; Guo, D.

    2016-12-01

    Root foraging for nutrient "hot spots" is a key strategy by which some plants maximize nutrient gain from their carbon investment in root and mycorrhizal hyphae. Foraging strategies may depend on costs of root construction, with thick roots generally costing more per unit length than thin roots. Investment in mycorrhizal hyphae, which are considerably thinner than roots, may represent an alternative strategy for cost-effective nutrient foraging, especially for thick-root species. Type of mycorrhiza may matter, as ectomycorrhizal (EM) fungi are more associated with longer hyphae and ability to mineralize organic matter than arbuscular mycorrhizal (AM) fungi. Among AM trees in both subtropical forests in SE China and in temperate forests in central Pennsylvania, USA, we found that tree species with thin roots proliferated their roots in soil patches enriched with mineral nutrients to a greater extent than species with thick roots. In addition, thick-root species were consistently colonized more heavily with mycorrhizal fungi than thin root species, although nutrient addition tended to diminish colonization. In a common garden in central Pennsylvania of both AM and EM tree species, we found that nutrient patches enriched with organic materials resulted in greater root and mycorrhizal fungal proliferation compared to those enriched with inorganic nutrients and that thick-root species proliferated more with their mycorrhizal fungi whereas thin-root species proliferated more with their roots. We further examined with many more species, patterns of root and mycorrhizal fungal proliferation in organic-nutrient-enriched patches. Foraging precision, or the extent that roots or mycorrhizal hyphae grew in the enriched patch relative to the unenriched patch, was related to both root thickness and type of mycorrhiza. In both AM and EM trees, thick-root species were not selective foragers of either their roots or hyphae. In thin-root species, there was strong selectivity in

  17. Production and function of jasmonates in nodulated roots of soybean plants inoculated with Bradyrhizobium japonicum.

    PubMed

    Costanzo, María Emilia; Andrade, Andrea; del Carmen Tordable, María; Cassán, Fabricio; Abdala, Guillermina

    2012-10-01

    Little is known regarding production and function of endogenous jasmonates (JAs) in root nodules of soybean plants inoculated with Bradyrhizobium japonicum. We investigated (1) production of jasmonic acid (JA) and 12-oxophytodienoic acid (OPDA) in roots of control and inoculated plants and in isolated nodules; (2) correlations between JAs levels, nodule number, and plant growth during the symbiotic process; and (3) effects of exogenous JA and OPDA on nodule cell number and size. In roots of control plants, JA and OPDA levels reached a maximum at day 18 after inoculation; OPDA level was 1.24 times that of JA. In roots of inoculated plants, OPDA peaked at day 15, whereas JA level did not change appreciably. Shoot dry matter of inoculated plants was higher than that of control at day 21. Chlorophyll a decreased more abruptly in control plants than in inoculated plants, whereas b decreased gradually in both cases. Exogenous JA or OPDA changed number and size of nodule central cells and peripheral cells. Findings from this and previous studies suggest that increased levels of JA and OPDA in control plants are related to senescence induced by nutritional stress. OPDA accumulation in nodulated roots suggests its involvement in "autoregulation of nodulation."

  18. Optical methods for creating delivery systems of chemical compounds to plant roots

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Pavel E.; Rogacheva, Svetlana M.; Arefeva, Oksana A.; Minin, Dmitryi V.; Tolmachev, Sergey A.; Kupadze, Machammad S.

    2004-08-01

    Spectrophotometric and fluorescence methods have been used for creation and investigation of various systems of target delivery of chemical compounds to roots of plants. The possibility of using liposomes, incrusted by polysaccharides of the external surface of nitrogen-fixing rizospheric bacteria Azospirillum brasilense SP 245, and nanoparticles incrusted by polysaccharides of wheat roots, as the named systems has been shown. The important role of polysaccharide-polysaccharide interaction in the adsorption processes of bacteria on wheat roots has been demonstrated.

  19. [Some peculiar features of liquid supply to the root medium of plants growing in microgravity

    NASA Technical Reports Server (NTRS)

    Podol'skii, I. G.; Sychev, V. N.; Levinskikh, M. A.; Strugov, O. M.; Bingham, G. E.; Salisbury, F. B. (Principal Investigator)

    1998-01-01

    Sixteen point probes monitored moisture level in the root medium of the wheat plants grown in greenhouse SVET on the MIR/NASA space science program. The article outlines types of water migration in the absence of gravity. Hydrophysical characteristics of perspective root media have been explored. Results of the water supply monitoring and control in the course of experiment are reported. The authors put forward porous root media to facilitate water migration and aeration.

  20. [Some peculiar features of liquid supply to the root medium of plants growing in microgravity

    NASA Technical Reports Server (NTRS)

    Podol'skii, I. G.; Sychev, V. N.; Levinskikh, M. A.; Strugov, O. M.; Bingham, G. E.; Salisbury, F. B. (Principal Investigator)

    1998-01-01

    Sixteen point probes monitored moisture level in the root medium of the wheat plants grown in greenhouse SVET on the MIR/NASA space science program. The article outlines types of water migration in the absence of gravity. Hydrophysical characteristics of perspective root media have been explored. Results of the water supply monitoring and control in the course of experiment are reported. The authors put forward porous root media to facilitate water migration and aeration.

  1. Root Foraging Increases Performance of the Clonal Plant Potentilla reptans in Heterogeneous Nutrient Environments

    PubMed Central

    Wang, Zhengwen; van Kleunen, Mark; During, Heinjo J.; Werger, Marinus J. A.

    2013-01-01

    Background Plastic root-foraging responses have been widely recognized as an important strategy for plants to explore heterogeneously distributed resources. However, the benefits and costs of root foraging have received little attention. Methodology/Principal Findings In a greenhouse experiment, we grew pairs of connected ramets of 22 genotypes of the stoloniferous plant Potentilla reptans in paired pots, between which the contrast in nutrient availability was set as null, medium and high, but with the total nutrient amount kept the same. We calculated root-foraging intensity of each individual ramet pair as the difference in root mass between paired ramets divided by the total root mass. For each genotype, we then calculated root-foraging ability as the slope of the regression of root-foraging intensity against patch contrast. For all genotypes, root-foraging intensity increased with patch contrast and the total biomass and number of offspring ramets were lowest at high patch contrast. Among genotypes, root-foraging intensity was positively related to production of offspring ramets and biomass in the high patch-contrast treatment, which indicates an evolutionary benefit of root foraging in heterogeneous environments. However, we found no significant evidence that the ability of plastic foraging imposes costs under homogeneous conditions (i.e. when foraging is not needed). Conclusions/Significance Our results show that plants of P. reptans adjust their root-foraging intensity according to patch contrast. Moreover, the results show that the root foraging has an evolutionary advantage in heterogeneous environments, while costs of having the ability of plastic root foraging were absent or very small. PMID:23472211

  2. Root foraging increases performance of the clonal plant Potentilla reptans in heterogeneous nutrient environments.

    PubMed

    Wang, Zhengwen; van Kleunen, Mark; During, Heinjo J; Werger, Marinus J A

    2013-01-01

    Plastic root-foraging responses have been widely recognized as an important strategy for plants to explore heterogeneously distributed resources. However, the benefits and costs of root foraging have received little attention. In a greenhouse experiment, we grew pairs of connected ramets of 22 genotypes of the stoloniferous plant Potentilla reptans in paired pots, between which the contrast in nutrient availability was set as null, medium and high, but with the total nutrient amount kept the same. We calculated root-foraging intensity of each individual ramet pair as the difference in root mass between paired ramets divided by the total root mass. For each genotype, we then calculated root-foraging ability as the slope of the regression of root-foraging intensity against patch contrast. For all genotypes, root-foraging intensity increased with patch contrast and the total biomass and number of offspring ramets were lowest at high patch contrast. Among genotypes, root-foraging intensity was positively related to production of offspring ramets and biomass in the high patch-contrast treatment, which indicates an evolutionary benefit of root foraging in heterogeneous environments. However, we found no significant evidence that the ability of plastic foraging imposes costs under homogeneous conditions (i.e. when foraging is not needed). Our results show that plants of P. reptans adjust their root-foraging intensity according to patch contrast. Moreover, the results show that the root foraging has an evolutionary advantage in heterogeneous environments, while costs of having the ability of plastic root foraging were absent or very small.

  3. Composite Medicago truncatula plants harbouring Agrobacterium rhizogenes-transformed roots reveal normal mycorrhization by Glomus intraradices

    PubMed Central

    Mrosk, Cornelia; Forner, Susanne; Hause, Gerd; Küster, Helge; Kopka, Joachim; Hause, Bettina

    2009-01-01

    Composite plants consisting of a wild-type shoot and a transgenic root are frequently used for functional genomics in legume research. Although transformation of roots using Agrobacterium rhizogenes leads to morphologically normal roots, the question arises as to whether such roots interact with arbuscular mycorrhizal (AM) fungi in the same way as wild-type roots. To address this question, roots transformed with a vector containing the fluorescence marker DsRed were used to analyse AM in terms of mycorrhization rate, morphology of fungal and plant subcellular structures, as well as transcript and secondary metabolite accumulations. Mycorrhization rate, appearance, and developmental stages of arbuscules were identical in both types of roots. Using Mt16kOLI1Plus microarrays, transcript profiling of mycorrhizal roots showed that 222 and 73 genes exhibited at least a 2-fold induction and less than half of the expression, respectively, most of them described as AM regulated in the same direction in wild-type roots. To verify this, typical AM marker genes were analysed by quantitative reverse transcription-PCR and revealed equal transcript accumulation in transgenic and wild-type roots. Regarding secondary metabolites, several isoflavonoids and apocarotenoids, all known to accumulate in mycorrhizal wild-type roots, have been found to be up-regulated in mycorrhizal in comparison with non-mycorrhizal transgenic roots. This set of data revealed a substantial similarity in mycorrhization of transgenic and wild-type roots of Medicago truncatula, validating the use of composite plants for studying AM-related effects. PMID:19574251

  4. On the longevity of desert plants and the production of new fine roots

    NASA Astrophysics Data System (ADS)

    Vargas, R.; Czimczik, C. I.; Bullock, S.; Xu, X.; Djuricin, S.

    2012-12-01

    There is evidence that some plants in arid regions can live for several hundreds of years suggesting a strong resilience to climate variability including drought events. Therefore, an important question is: Which are the physiological mechanisms of survival that are present in long-lived plants? Recent studies have shown that plants are able to store nonstructural carbon (NSC) for several years and then allocate them for production of new structures such as fine roots. We established an experiment to measure the radiocarbon age of new fine roots of desert plants between 150 and 400 years old. The study site was located at the Central Desert of Baja California, Mexico and included individuals of Brahea armata, Washingtonia robusta, and Pachycereus pringlei. Our results showed that on average all the plant species were able to use stored old carbon for production of new fine roots. These results suggest that NSC pools are important in determining belowground responses of long-lived desert plants.

  5. Green Roots: Photosynthesis and Photoautotrophy in an Underground Plant Organ.

    PubMed Central

    Flores, H. E.; Dai, Yr.; Cuello, J. L.; Maldonado-Mendoza, I. E.; Loyola-Vargas, V. M.

    1993-01-01

    The potential for photosynthetic and photoautotrophic growth was studied in hairy root cultures of Asteraceae and Solanaceae species. Upon transfer to light, initially heterotrophic root cultures of Acmella oppositifolia and Datura innoxia greened rapidly, differentiated chloroplasts, and developed light-dependent CO2 fixation in the cortical cells. Photosynthetic potential was expressed in root cultures of all the Asteraceae genera examined (Acmella, Artemisia, Rudbeckia, Stevia, and Tagetes). Hairy roots of A. oppositifolia and D. innoxia were further adapted to photoautotrophy by growing in the presence of light and added CO2 (1-5%) and by direct or sequential transfers into media containing progressively lower sugar concentrations. The transition to photoautotrophy was accompanied by an increase in CO2 fixation and in the specific activity of 1,5-ribulose-bisphosphate carboxylase/ oxygenase (Rubisco). During the adaptation of A. oppositifolia roots to photoautotrophy, the ratio of Rubisco to phosphoenolpyruvate carboxylase increased significantly, approaching that found in the leaves. The levels and patterns of alkaloids and polyacetylenes produced by Solanaceae and Asteraceae hairy roots, respectively, were dramatically altered in photomixotrophic and photoautotrophic cultures. Photoautotrophic roots of A. oppositifolia have been mainitained in vitro for over 2 years. PMID:12231691

  6. Green Roots: Photosynthesis and Photoautotrophy in an Underground Plant Organ.

    PubMed

    Flores, H. E.; Dai, Yr.; Cuello, J. L.; Maldonado-Mendoza, I. E.; Loyola-Vargas, V. M.

    1993-02-01

    The potential for photosynthetic and photoautotrophic growth was studied in hairy root cultures of Asteraceae and Solanaceae species. Upon transfer to light, initially heterotrophic root cultures of Acmella oppositifolia and Datura innoxia greened rapidly, differentiated chloroplasts, and developed light-dependent CO2 fixation in the cortical cells. Photosynthetic potential was expressed in root cultures of all the Asteraceae genera examined (Acmella, Artemisia, Rudbeckia, Stevia,