Science.gov

Sample records for fine root growth

  1. Cottonwood growth rate and fine root condensed tannin concentration.

    PubMed

    Kosola, Kevin R; Dickmann, Donald I; Hall, Richard B; Workmaster, Beth Ann A

    2004-09-01

    We examined the relationship between trunk diameter and diameter relative growth rate (RGR) and fine root condensed tannin concentration in 12 genotypes of eastern cottonwood (Populus deltoides Bartr. ex Marsh.) planted in three locations across the north central United States. Across genotypes, trunk diameter, diameter RGR and root condensed tannin concentration were negatively correlated at one location (Wisconsin), but showed no significant correlation at the other locations (Iowa and Michigan). The factors responsible for this difference among sites remain unidentified, but may be related to soil fertility.

  2. Growth patterns and morphology of fine roots of size-controlling and invigorating peach rootstocks.

    PubMed

    Basile, Boris; Bryla, David R; Salsman, Michelle L; Marsal, Jordi; Cirillo, Chiara; Johnson, R Scott; Dejong, Theodore M

    2007-02-01

    We compared growth patterns and morphology of fine roots of size-controlling and invigorating peach (Prunus persica (L.) Batsch) rootstocks. Peach trees were grafted on five rootstocks: a vigorous control (Nemaguard), three intermediate vigor rootstocks (K119-50, P30-135 and Hiawatha), and a semi-dwarfing rootstock (K146-43). Minirhizotron tubes were installed at the base of trees on each rootstock and root images captured with a minirhizotron digital camera system. Number, visible length, and diameter of new roots were recorded at fixed soil depths from April 19, 2000 to December 19, 2001. Root diameter, specific root length, root tissue density and root length density were also measured periodically for each rootstock on roots collected from in-growth cores. Rootstocks had similar seasonal patterns of new root production. Fine root production was lowest in winter and appeared to decline during the final stages of fruit growth. A rootstock with almond in its genetic background (K119-50) produced the greatest quantity of fine roots and had the greatest number of new roots below 69 cm, whereas there were no differences among the other four rootstocks in the total number of roots produced. Rootstock K146-43 had thicker fine roots than the other rootstocks. Independent of rootstock, fine roots produced during spring had greater specific root length than those produced later in the season. The seasonal pattern of fine root production did not appear to be associated with the previously reported effects of these dwarfing rootstocks on shoot growth and stem water potential early in the growing season.

  3. Effects of water and nutrient availability on fine root growth in eastern Amazonian forest regrowth, Brazil.

    PubMed

    Lima, Tâmara Thaiz Santana; Miranda, Izildinha Souza; Vasconcelos, Steel Silva

    2010-08-01

    *Fine root dynamics is widely recognized as an important biogeochemical process, but there are few data on fine root growth and its response to soil resource availability, especially for tropical forests. *We evaluated the response of fine root dynamics to altered availability of soil water and nutrients in a 20-yr-old forest regrowth in eastern Amazonia. In one experiment the dry season reduction in soil moisture was alleviated by irrigation. In the other experiment, nutrient supply was reduced by litter removal. We used the ingrowth core technique to measure fine root mass growth, length growth, mortality and specific root length. *Dry-season irrigation had no significant effect on mass and length of live and dead roots, whereas litter removal reduced mass and length of live roots. For both irrigation and litter removal experiments, root growth was significantly greater in the dry season than in the wet season. *Increased root growth was associated with decreased soil water availability. However, root growth did not increase in response to nutrient reduction in litter removal plots. Overall, our results suggest that belowground allocation may differ according to the type of soil resource limitation. PMID:20524991

  4. Direct and legacy effects of long-term elevated CO₂ on fine root growth and plant-insect interactions.

    PubMed

    Stiling, Peter; Moon, Daniel; Rossi, Anthony; Forkner, Rebecca; Hungate, Bruce A; Day, Frank P; Schroeder, Rachel E; Drake, Bert

    2013-11-01

    Increasing atmospheric CO₂ concentrations alter leaf physiology, with effects that cascade to communities and ecosystems. Yet, responses over cycles of disturbance and recovery are not well known, because most experiments span limited ecological time. We examined the effects of CO₂ on root growth, herbivory and arthropod biodiversity in a woodland from 1996 to 2006, and the legacy of CO₂ enrichment on these processes during the year after the CO₂ treatment ceased. We used minirhizotrons to study root growth, leaf censuses to study herbivory and pitfall traps to determine the effects of elevated CO₂ on arthropod biodiversity. Elevated CO₂ increased fine root biomass, but decreased foliar nitrogen and herbivory on all plant species. Insect biodiversity was unchanged in elevated CO₂. Legacy effects of elevated CO₂ disappeared quickly as fine root growth, foliar nitrogen and herbivory levels recovered in the next growing season following the cessation of elevated CO₂. Although the effects of elevated CO₂ cascade through plants to herbivores, they do not reach other trophic levels, and biodiversity remains unchanged. The legacy of 10 yr of elevated CO₂ on plant-herbivore interactions in this system appear to be minimal, indicating that the effects of elevated CO₂ may not accumulate over cycles of disturbance and recovery.

  5. Replicated throughfall exclusion experiment in an Indonesian perhumid rainforest: wood production, litter fall and fine root growth under simulated drought.

    PubMed

    Moser, Gerald; Schuldt, Bernhard; Hertel, Dietrich; Horna, Viviana; Coners, Heinz; Barus, Henry; Leuschner, Christoph

    2014-05-01

    Climate change scenarios predict increases in the frequency and duration of ENSO-related droughts for parts of South-East Asia until the end of this century exposing the remaining rainforests to increasing drought risk. A pan-tropical review of recorded drought-related tree mortalities in more than 100 monitoring plots before, during and after drought events suggested a higher drought-vulnerability of trees in South-East Asian than in Amazonian forests. Here, we present the results of a replicated (n = 3 plots) throughfall exclusion experiment in a perhumid tropical rainforest in Sulawesi, Indonesia. In this first large-scale roof experiment outside semihumid eastern Amazonia, 60% of the throughfall was displaced during the first 8 months and 80% during the subsequent 17 months, exposing the forest to severe soil desiccation for about 17 months. In the experiment's second year, wood production decreased on average by 40% with largely different responses of the tree families (ranging from -100 to +100% change). Most sensitive were trees with high radial growth rates under moist conditions. In contrast, tree height was only a secondary factor and wood specific gravity had no influence on growth sensitivity. Fine root biomass was reduced by 35% after 25 months of soil desiccation while fine root necromass increased by 250% indicating elevated fine root mortality. Cumulative aboveground litter production was not significantly reduced in this period. The trees from this Indonesian perhumid rainforest revealed similar responses of wood and litter production and root dynamics as those in two semihumid Amazonian forests subjected to experimental drought. We conclude that trees from paleo- or neotropical forests growing in semihumid or perhumid climates may not differ systematically in their growth sensitivity and vitality under sublethal drought stress. Drought vulnerability may depend more on stem cambial activity in moist periods than on tree height or wood

  6. Replicated throughfall exclusion experiment in an Indonesian perhumid rainforest: wood production, litter fall and fine root growth under simulated drought.

    PubMed

    Moser, Gerald; Schuldt, Bernhard; Hertel, Dietrich; Horna, Viviana; Coners, Heinz; Barus, Henry; Leuschner, Christoph

    2014-05-01

    Climate change scenarios predict increases in the frequency and duration of ENSO-related droughts for parts of South-East Asia until the end of this century exposing the remaining rainforests to increasing drought risk. A pan-tropical review of recorded drought-related tree mortalities in more than 100 monitoring plots before, during and after drought events suggested a higher drought-vulnerability of trees in South-East Asian than in Amazonian forests. Here, we present the results of a replicated (n = 3 plots) throughfall exclusion experiment in a perhumid tropical rainforest in Sulawesi, Indonesia. In this first large-scale roof experiment outside semihumid eastern Amazonia, 60% of the throughfall was displaced during the first 8 months and 80% during the subsequent 17 months, exposing the forest to severe soil desiccation for about 17 months. In the experiment's second year, wood production decreased on average by 40% with largely different responses of the tree families (ranging from -100 to +100% change). Most sensitive were trees with high radial growth rates under moist conditions. In contrast, tree height was only a secondary factor and wood specific gravity had no influence on growth sensitivity. Fine root biomass was reduced by 35% after 25 months of soil desiccation while fine root necromass increased by 250% indicating elevated fine root mortality. Cumulative aboveground litter production was not significantly reduced in this period. The trees from this Indonesian perhumid rainforest revealed similar responses of wood and litter production and root dynamics as those in two semihumid Amazonian forests subjected to experimental drought. We conclude that trees from paleo- or neotropical forests growing in semihumid or perhumid climates may not differ systematically in their growth sensitivity and vitality under sublethal drought stress. Drought vulnerability may depend more on stem cambial activity in moist periods than on tree height or wood

  7. Response of leaf and fine roots proteomes of Salix viminalis L. to growth on Cr-rich tannery waste.

    PubMed

    Zemleduch-Barylska, Agata; Lorenc-Plucińska, Gabriela

    2016-09-01

    The tannery industry is a major source of anthropogenic chromium (Cr) contamination due to the large amounts of solid waste produced and its problematic management. The unique composition of tannery waste, usually high concentrations of Cr and other metals as well as organic matter and nutrients, makes it a great risk for soil and water environment but also a possible effective fertilizer for non-food plants that can tolerate metals. The goal of this study was to understand the adaptation mechanism of Salix viminalis to growth on Cr-rich tannery waste from an active landfill. We used a proteomic approach to identify leaf and fine roots proteins altered by tannery waste as compared to control soil conditions. We found no obvious symptoms of oxidative stress in leaves or fine roots. Proteomic results indicated some changes in metabolism, with increases in energy production processes and their greater efficiency for leaves rather than root development. Comparison between S. viminalis and P. × canescens response to tannery waste suggested that S. viminalis is not suitable for remediation of Cr-contaminated areas of a tannery waste landfill site.

  8. Response of leaf and fine roots proteomes of Salix viminalis L. to growth on Cr-rich tannery waste.

    PubMed

    Zemleduch-Barylska, Agata; Lorenc-Plucińska, Gabriela

    2016-09-01

    The tannery industry is a major source of anthropogenic chromium (Cr) contamination due to the large amounts of solid waste produced and its problematic management. The unique composition of tannery waste, usually high concentrations of Cr and other metals as well as organic matter and nutrients, makes it a great risk for soil and water environment but also a possible effective fertilizer for non-food plants that can tolerate metals. The goal of this study was to understand the adaptation mechanism of Salix viminalis to growth on Cr-rich tannery waste from an active landfill. We used a proteomic approach to identify leaf and fine roots proteins altered by tannery waste as compared to control soil conditions. We found no obvious symptoms of oxidative stress in leaves or fine roots. Proteomic results indicated some changes in metabolism, with increases in energy production processes and their greater efficiency for leaves rather than root development. Comparison between S. viminalis and P. × canescens response to tannery waste suggested that S. viminalis is not suitable for remediation of Cr-contaminated areas of a tannery waste landfill site. PMID:27282371

  9. Stored carbon partly fuels fine-root respiration but is not used for production of new fine roots

    SciTech Connect

    Lynch, Douglas J; Matamala-Paradeda, Roser; Iversen, Colleen M; Norby, Richard J; Gonzalez-Meler, Miguel A

    2013-01-01

    The relative use of new photosynthate compared to stored C for the production and maintenance of fine roots, and the rate of C turnover in heterogeneous fine-root populations, are poorly understood. We followed the relaxation of a 13C tracer in fine roots in a Liquidambar styraciflua plantation at the conclusion of a free-air CO2 enrichment experiment. Goals included quantifying the relative fractions of new photosynthate versus stored C used in root growth and root respiration, as well as the turnover rate of fine-root C fixed during [CO2] fumigation. New fine-root growth was largely from recent photosynthate, while nearly one-quarter of respired C was from a storage pool. Changes in the isotopic composition of the fine-root population over two full growing seasons indicated heterogeneous C pools; less than 10% of root C had a residence time < 3 months, while a majority of root C had a residence time > 2 years. Compared to a 1-pool model, a 2-pool model for C turnover in fine roots (with 5 and 0.37 yr-1 turnover times) doubles the fine-root contribution to forest NPP (9-13%) and supports the 50% root-to-soil transfer rate often used in models.

  10. ADVANCING FINE ROOT RESEARCH WITH MINIRHIZOTRONS

    EPA Science Inventory

    Minirhizotrons provide a nondestructive, in situ method for directly viewing and studying fine roots. Although many insights into fine roots have been gained using minirhizotrons, it is clear from the literature that there is still wide variation in how minirhizotrons and minirhi...

  11. Unresolving the "real age" of fine roots in forest ecosystems

    NASA Astrophysics Data System (ADS)

    Solly, Emily; Brunner, Ivano; Herzog, Claude; Schöning, Ingo; Schrumpf, Marion; Schweigruber, Fritz; Trumbore, Susan; Hagedorn, Frank

    2016-04-01

    Estimating the turnover time of tree fine roots is crucial for modelling soil organic matter dynamics, but it is one of the biggest challenges in soil ecology and one of the least understood aspects of the belowground carbon cycle. The methods used - ranging from radiocarbon to ingrowth cores and root cameras (minirhizotrons) - yield very diverse pictures of fine root dynamics in forest ecosystems with turnover rates reaching from less than one year to decades. These have huge implications on estimates of carbon allocation to root growth and maintenance and on the persistence of root carbon in soils before it is decomposed or leached. We will present a new approach, involving techniques to study plant anatomy, which unravels the "real age" of fine roots. For a range of forests with diverse water and nutrient limitations located at different latitudes, we investigated the annual growth rings in the secondary xylem of thin transversal sections of fine roots belonging to tree species which form distinct growth rings. In temperate forests we find mean root "ring ages" of 1-2 years while in sub-arctic forests living fine roots can also persist for several years. The robustness of these results were tested by counting the maximum yearly growth rings in tree seedlings of known age and by counting the maximum number of growth rings of fine roots grown in ingrowth cores which were kept in temperate forest soils for one and two years. Radiocarbon estimates of mean "carbon ages", which define the time elapsed since structural carbon was fixed from the atmosphere, instead average around a decade in root systems of temperate forests (mixture of newly produced and older living roots). This dramatic difference may not be related to methodological bias, but to a time lag between C assimilation and production of a portion of fine root tissues due to the storage of older carbon components. The time lag depends very likely on tree species and environmental conditions. We further

  12. Fine Root Longevity Still Under Debate

    NASA Astrophysics Data System (ADS)

    Keel, S. G.; Blackburn, M.; Campbell, C.; Högberg, M. N.; Richter, A.; Wild, B.; Högberg, P.

    2008-12-01

    Assuming that fine roots (< 2 mm in diameter) turn over once per year, they represent a third of the global annual net primary productivity. These turnover estimates are based on rhizotron studies, where root longevity is determined by monitoring the appearance/disappearance of roots on a screen, which is inserted into the soil. Much slower fine root turnover rates were found using carbon (C) isotope methods (either 14C dating or continuous 13C-labelling), resulting in root longevities of several years. Stable C isotope tracer experiments, are argued to overestimate fine root longevities, mainly because the smallest roots with the highest turn over, are easily missed during sampling. The goal of the present study was therefore to carry out a C-labelling experiment, and specifically focus on the finest roots, namely root tips. In addition we sampled whole fine roots (<1 mm and 1-3 mm in diameter), as in other studies. We pulse labelled 14-year-old Pinus sylvestris (Pine) trees in the field for only three hours with highly 13C-enriched CO2 (24 atom percent). The mean residence time (MRT) of recently assimilated C in root tips was determined, as a measure for root longevity. Already two days after labelling, recent C had been translocated from the crowns to fine roots indicating rapid belowground C allocation. 13C signals in root tips were stronger than in whole roots, which shows that they are the most active part of the root system. MRT of C calculated using first order exponential decay functions of C in bulk roots were around 20 days in both <1mm and 1-3mm roots and 29 days in root tips. A rapid decline in 13C signals was observed which could be explained by a rapid decrease in the signal of the sucrose pool, which had a MRT of 5 days. However, part of the labelled C had been allocated to a pool with a slower turnover rate (most likely structural compounds such as cellulose) as indicated by persisting 13C signals measured 120 days after labelling. MRT of C in

  13. Impacts of environmental factors on fine root lifespan

    PubMed Central

    McCormack, M. Luke; Guo, Dali

    2014-01-01

    The lifespan of fast-cycling roots is a critical parameter determining a large flux of plant carbon into soil through root turnover and is a biological feature regulating the capacity of a plant to capture soil water and nutrients via root-age-related physiological processes. While the importance of root lifespan to whole-plant and ecosystem processes is increasingly recognized, robust descriptions of this dynamic process and its response to changes in climatic and edaphic factors are lacking. Here we synthesize available information and propose testable hypotheses using conceptual models to describe how changes in temperature, water, nitrogen (N), and phosphorus (P) availability impact fine root lifespan within a species. Each model is based on intrinsic responses including root physiological activity and alteration of carbohydrate allocation at the whole-plant level as well as extrinsic factors including mycorrhizal fungi and pressure from pathogens, herbivores, and other microbes. Simplifying interactions among these factors, we propose three general principles describing fine root responses to complex environmental gradients. First, increases in a factor that strongly constrains plant growth (temperature, water, N, or P) should result in increased fine root lifespan. Second, increases in a factor that exceeds plant demand or tolerance should result in decreased lifespan. Third, as multiple factors interact fine root responses should be determined by the most dominant factor controlling plant growth. Moving forward, field experiments should determine which types of species (e.g., coarse vs. fine rooted, obligate vs. facultative mycotrophs) will express greater plasticity in response to environmental gradients while ecosystem models may begin to incorporate more detailed descriptions of root lifespan and turnover. Together these efforts will improve quantitative understanding of root dynamics and help to identify areas where future research should be focused

  14. The effect of limited availability of N or water on C allocation to fine roots and annual fine root turnover in Alnus incana and Salix viminalis.

    PubMed

    Rytter, Rose-Marie

    2013-09-01

    The effect of limited nitrogen (N) or water availability on fine root growth and turnover was examined in two deciduous species, Alnus incana L. and Salix viminalis L., grown under three different regimes: (i) supply of N and water in amounts which would not hamper growth, (ii) limited N supply and (iii) limited water supply. Plants were grown outdoors during three seasons in covered and buried lysimeters placed in a stand structure and filled with quartz sand. Computer-controlled irrigation and fertilization were supplied through drip tubes. Production and turnover of fine roots were estimated by combining minirhizotron observations and core sampling, or by sequential core sampling. Annual turnover rates of fine roots <1 mm (5-6 year(-1)) and 1-2 mm (0.9-2.8 year(-1)) were not affected by changes in N or water availability. Fine root production (<1 mm) differed between Alnus and Salix, and between treatments in Salix; i.e., absolute length and biomass production increased in the order: water limited < unlimited < N limited. Few treatment effects were detected for fine roots 1-2 mm. Proportionally more C was allocated to fine roots (≤2 mm) in N or water-limited Salix; 2.7 and 2.3 times the allocation to fine roots in the unlimited regime, respectively. Estimated input to soil organic carbon increased by ca. 20% at N limitation in Salix. However, future studies on fine root decomposition under various environmental conditions are required. Fine root growth responses to N or water limitation were less pronounced in Alnus, thus indicating species differences caused by N-fixing capacity and slower initial growth in Alnus, or higher fine root plasticity in Salix. A similar seasonal growth pattern across species and treatments suggested the influence of outer stimuli, such as temperature and light.

  15. Applicability of optical scanner method for fine root dynamics

    NASA Astrophysics Data System (ADS)

    Kume, Tomonori; Ohashi, Mizue; Makita, Naoki; Khoon Kho, Lip; Katayama, Ayumi; Matsumoto, Kazuho; Ikeno, Hidetoshi

    2016-04-01

    Fine root dynamics is one of the important components in forest carbon cycling, as ~60 % of tree photosynthetic production can be allocated to root growth and metabolic activities. Various techniques have been developed for monitoring fine root biomass, production, mortality in order to understand carbon pools and fluxes resulting from fine roots dynamics. The minirhizotron method is now a widely used technique, in which a transparent tube is inserted into the soil and researchers count an increase and decrease of roots along the tube using images taken by a minirhizotron camera or minirhizotron video camera inside the tube. This method allows us to observe root behavior directly without destruction, but has several weaknesses; e.g., the difficulty of scaling up the results to stand level because of the small observation windows. Also, most of the image analysis are performed manually, which may yield insufficient quantitative and objective data. Recently, scanner method has been proposed, which can produce much bigger-size images (A4-size) with lower cost than those of the minirhizotron methods. However, laborious and time-consuming image analysis still limits the applicability of this method. In this study, therefore, we aimed to develop a new protocol for scanner image analysis to extract root behavior in soil. We evaluated applicability of this method in two ways; 1) the impact of different observers including root-study professionals, semi- and non-professionals on the detected results of root dynamics such as abundance, growth, and decomposition, and 2) the impact of window size on the results using a random sampling basis exercise. We applied our new protocol to analyze temporal changes of root behavior from sequential scanner images derived from a Bornean tropical forests. The results detected by the six observers showed considerable concordance in temporal changes in the abundance and the growth of fine roots but less in the decomposition. We also examined

  16. Patterns in soil fertility and root herbivory interact to influence fine-root dynamics.

    PubMed

    Stevens, Glen N; Jones, Robert H

    2006-03-01

    Fine-scale soil nutrient enrichment typically stimulates root growth, but it may also increase root herbivory, resulting in trade-offs for plant species and potentially influencing carbon cycling patterns. We used root ingrowth cores to investigate the effects of microsite fertility and root herbivory on root biomass in an aggrading upland forest in the coastal plain of South Carolina, USA. Treatments were randomly assigned to cores from a factorial combination of fertilizer and insecticide. Soil, soil fauna, and roots were removed from the cores at the end of the experiment (8-9 mo), and roots were separated at harvest into three diameter classes. Each diameter class responded differently to fertilizer and insecticide treatments. The finest roots (< 1.0 mm diameter), which comprised well over half of all root biomass, were the only ones to respond significantly to both treatments, increasing when fertilizer and when insecticide were added (each P < 0.0001), with maximum biomass found where the treatments were combined (interaction term significant, P < 0.001). These results suggest that root-feeding insects have a strong influence on root standing crop with stronger herbivore impacts on finer roots and within more fertile microsites. Thus, increased vulnerability to root herbivory is a potentially significant cost of root foraging in nutrient-rich patches.

  17. PATTERNS IN SOIL FERTILITY AND ROOT HERBIVORY INTERACT TO INFLUENCE FINE-ROOT DYNAMICS.

    SciTech Connect

    Stevens, Glen, N.; Jones, Robert, H.

    2006-03-01

    Fine-scale soil nutrient enrichment typically stimulates root growth, but it may also increase root herbivory, resulting in trade-offs for plant species and potentially influencing carbon cycling patterns. We used root ingrowth cores to investigate the effects of microsite fertility and root herbivory on root biomass in an aggrading upland forest in the coastal plain of South Carolina, USA. Treatments were randomly assigned to cores from a factorial combination of fertilizer and insecticide. Soil, soil fauna, and roots were removed from the cores at the end of the experiment (8–9 mo), and roots were separated at harvest into three diameter classes. Each diameter class responded differently to fertilizer and insecticide treatments. The finest roots (,1.0 mm diameter), which comprised well over half of all root biomass, were the only ones to respond significantly to both treatments, increasing when fertilizer and when insecticide were added (each P , 0.0001), with maximum biomass found where the treatments were combined (interaction term significant, P , 0.001). These results suggest that root-feeding insects have a strong influence on root standing crop with stronger herbivore impacts on finer roots and within more fertile microsites. Thus, increased vulnerability to root herbivory is a potentially significant cost of root foraging in nutrient-rich patches.

  18. Fine-root mortality rates in a temperate forest: Estimates using radiocarbon data and numerical modeling

    SciTech Connect

    Riley, W.J.; Gaudinski, J.B.; Torn, M.S.; Joslin, J.D.; Hanson, P.J.

    2009-09-01

    We used an inadvertent whole-ecosystem {sup 14}C label at a temperate forest in Oak Ridge, Tennessee, USA to develop a model (Radix1.0) of fine-root dynamics. Radix simulates two live-root pools, two dead-root pools, non-normally distributed root mortality turnover times, a stored carbon (C) pool, and seasonal growth and respiration patterns. We applied Radix to analyze measurements from two root size classes (< 0.5 and 0.5-2.0 mm diameter) and three soil-depth increments (O horizon, 0-15 cm and 30-60 cm). Predicted live-root turnover times were < 1 yr and 10 yr for short- and long-lived pools, respectively. Dead-root pools had decomposition turnover times of 2 yr and 10 yr. Realistic characterization of C flows through fine roots requires a model with two live fine-root populations, two dead fine-root pools, and root respiration. These are the first fine-root turnover time estimates that take into account respiration, storage, seasonal growth patterns, and non-normal turnover time distributions. The presence of a root population with decadal turnover times implies a lower amount of belowground net primary production used to grow fine-root tissue than is currently predicted by models with a single annual turnover pool.

  19. 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.

  20. Novel temporal, fine-scale and growth variation phenotypes in roots of adult-stage maize (Zea mays L.) in response to low nitrogen stress.

    PubMed

    Gaudin, Amelie C M; McClymont, Sarah A; Holmes, Bridget M; Lyons, Eric; Raizada, Manish N

    2011-12-01

    There is interest in discovering root traits associated with acclimation to nutrient stress. Large root systems, such as in adult maize, have proven difficult to be phenotyped comprehensively and over time, causing target traits to be missed. These challenges were overcome here using aeroponics, a system where roots grow in the air misted with a nutrient solution. Applying an agriculturally relevant degree of low nitrogen (LN) stress, 30-day-old plants responded by increasing lengths of individual crown roots (CRs) by 63%, compensated by a 40% decline in CR number. LN increased the CR elongation rate rather than lengthening the duration of CR growth. Only younger CR were significantly responsive to LN stress, a novel finding. LN shifted the root system architectural balance, increasing the lateral root (LR)-to-CR ratio, adding ∼70 m to LR length. LN caused a dramatic increase in second-order LR density, not previously reported in adult maize. Despite the near-uniform aeroponics environment, LN induced increased variation in the relative lengths of opposing LR pairs. Large-scale analysis of root hairs (RHs) showed that LN decreased RH length and density. Time-course experiments suggested the RH responses may be indirect consequences of decreased biomass/demand under LN. These results identify novel root traits for genetic dissection. PMID:21848860

  1. Estimate of fine root production including the impact of decomposed roots in a Bornean tropical rainforest

    NASA Astrophysics Data System (ADS)

    Katayama, Ayumi; Khoon Koh, Lip; Kume, Tomonori; Makita, Naoki; Matsumoto, Kazuho; Ohashi, Mizue

    2016-04-01

    Considerable carbon is allocated belowground and used for respiration and production of roots. It is reported that approximately 40 % of GPP is allocated belowground in a Bornean tropical rainforest, which is much higher than those in Neotropical rainforests. This may be caused by high root production in this forest. Ingrowth core is a popular method for estimating fine root production, but recent study by Osawa et al. (2012) showed potential underestimates of this method because of the lack of consideration of the impact of decomposed roots. It is important to estimate fine root production with consideration for the decomposed roots, especially in tropics where decomposition rate is higher than other regions. Therefore, objective of this study is to estimate fine root production with consideration of decomposed roots using ingrowth cores and root litter-bag in the tropical rainforest. The study was conducted in Lambir Hills National Park in Borneo. Ingrowth cores and litter bags for fine roots were buried in March 2013. Eighteen ingrowth cores and 27 litter bags were collected in May, September 2013, March 2014 and March 2015, respectively. Fine root production was comparable to aboveground biomass increment and litterfall amount, and accounted only 10% of GPP in this study site, suggesting most of the carbon allocated to belowground might be used for other purposes. Fine root production was comparable to those in Neotropics. Decomposed roots accounted for 18% of fine root production. This result suggests that no consideration of decomposed fine roots may cause underestimate of fine root production.

  2. Fine root dynamics along an elevational gradient in tropical Amazonian and Andean forests

    NASA Astrophysics Data System (ADS)

    Girardin, C. A. J.; AragãO, L. E. O. C.; Malhi, Y.; Huaraca Huasco, W.; Metcalfe, D. B.; Durand, L.; Mamani, M.; Silva-Espejo, J. E.; Whittaker, R. J.

    2013-01-01

    The key role of tropical forest belowground carbon stocks and fluxes is well recognised as one of the main components of the terrestrial ecosystem carbon cycle. This study presents the first detailed investigation of spatial and temporal patterns of fine root stocks and fluxes in tropical forests along an elevational gradient, ranging from the Peruvian Andes (3020 m) to lowland Amazonia (194 m), with mean annual temperatures of 11.8°C to 26.4 °C and annual rainfall values of 1900 to 1560 mm yr-1, respectively. Specifically, we analyse abiotic parameters controlling fine root dynamics, fine root growth characteristics, and seasonality of net primary productivity along the elevation gradient. Root and soil carbon stocks were measured by means of soil cores, and fine root productivity was recorded using rhizotron chambers and ingrowth cores. We find that mean annual fine root below ground net primary productivity in the montane forests (0-30 cm depth) ranged between 4.27±0.56 Mg C ha-1 yr-1 (1855 m) and 1.72±0.87 Mg C ha-1 yr-1 (3020 m). These values include a correction for finest roots (<0.6 mm diameter), which we suspect are under sampled, resulting in an underestimation of fine roots by up to 31% in current ingrowth core counting methods. We investigate the spatial and seasonal variation of fine root dynamics using soil depth profiles and an analysis of seasonal amplitude along the elevation gradient. We report a stronger seasonality of NPPFineRoot within the cloud immersion zone, most likely synchronised to seasonality of solar radiation. Finally, we provide the first insights into root growth characteristics along a tropical elevation transect: fine root area and fine root length increase significantly in the montane cloud forest. These insights into belowground carbon dynamics of tropical lowland and montane forests have significant implications for our understanding of the global tropical forest carbon cycle.

  3. Moving forward with fine-root definitions and research

    DOE PAGESBeta

    McCormack, M. Luke; Iversen, Colleen M.; Eissenstat, David M.

    2016-08-30

    Here, in the letter published in this issue of New Phytologist (pp. 310-312), 'Fine roots - functional definition expanded to crop species?' Dr. Zobel emphasizes the importance of heterogeneity within crop-root systems.

  4. Fine-root responses to fertilization reveal multiple nutrient limitation in a lowland tropical forest.

    PubMed

    Wurzburger, Nina; Wright, S Joseph

    2015-08-01

    Questions remain as to which soil nutrients limit primary production in tropical forests. Phosphorus (P) has long been considered the primary limiting element in lowland forests, but recent evidence demonstrates substantial heterogeneity in response to nutrient addition, highlighting a need to understand and diagnose nutrient limitation across diverse forests. Fine-root characteristics including their abundance, functional traits, and mycorrhizal symbionts can be highly responsive to changes in soil nutrients and may help to diagnose nutrient limitation. Here, we document the response of fine roots to long-term nitrogen (N), P, and potassium (K) fertilization in a lowland forest in Panama. Because this experiment has demonstrated that N and K together limit tree growth and P limits fine litter production, we hypothesized that fine roots would also respond to nutrient addition. Specifically we hypothesized that N, P, and K addition would reduce the biomass, diameter, tissue density, and mycorrhizal colonization of fine roots, and increase nutrient concentration in root tissue. Most morphological root traits responded to the single addition of K and the paired addition of N and P, with the greatest response to all three nutrients combined. The addition of N, P, and K together reduced fine-root biomass, length, and tissue density, and increased specific root length, whereas root diameter remained unchanged. Nitrogen addition did not alter root N concentration, but P and K addition increased root P and K concentration, respectively. Mycorrhizal colonization of fine roots declined with N, increased with P, and was unresponsive to K addition. Although plant species composition remains unchanged after 14 years of fertilization, fine-root characteristics responded to N, P, and K addition, providing some of the strongest stand-level responses in this experiment. Multiple soil nutrients regulate fine-root abundance, morphological and chemical traits, and their association

  5. Heterorhizy can lead to underestimation of fine-root production when using mesh-based techniques

    NASA Astrophysics Data System (ADS)

    Montagnoli, A.; Terzaghi, M.; Scippa, G. S.; Chiatante, D.

    2014-08-01

    This study investigates the relationship between fine-root morphology and net mesh size in fine-root production (FRP) measurements (ingrowth core and net method). The data collected show that when a fine root has an apical diameter equal or bigger than the mesh size, the degree of difficulty in passing through the net determines a response that arrests growth or deviation from the initial direction of growth. Both reactions prevent the root from crossing the net and induce the fine root to produce new laterals with thinner diameters. The investment in biomass necessary to form the new laterals is smaller than that needed to support the parental fine root and this leads to determines an underestimation of FRP. In particular, a considerable reduction of fine-root biomass in the area outside the netting was detected with a mesh size below 1.5 mm. The choice of net mesh size to be used for FRP measurement cannot be arbitrary, but should be evaluated through a preliminary analysis of fine-root morphology of experimental species prior to net installation.

  6. Quantifying Fine Root Carbon Inputs To Soil: Results From Combining Radiocarbon And Traditional Methodologies.

    NASA Astrophysics Data System (ADS)

    Gaudinski, J. B.; Trumbore, S. E.; Dawson, T.; Torn, M.; Pregitzer, K.; Joslin, J. D.

    2002-12-01

    Estimates of high belowground net primary productivity (50% or more) in forest ecosystems are often based on assumptions that almost all fine roots (< 2 mm in diameter) live and die within one year. Recent radiocarbon (14C) measurements of fine root cellulose in three eastern temperate forests of the United States show that at least a portion of fine roots are living for more than 8 years (Gaudinski et al. 2001) and that fine root lifespans likely vary as a function of both diameter and position on the root branch system. New data from investigations under way in several different temperate forests further support the idea of large variations in root lifespans with radiocarbon-derived ages ranging from approximately one year to several years. In forests where both mini-rhizotron and 14C lifespan estimates have been made, the two techniques agree well when the 14C sampling is made on the same types of roots viewed by mini-rhizotron cameras (i.e. first and second order roots; the most distal and newest roots on the root branching system), and the 14C signature of new root growth is known. We have quantified the signature of new tree roots by taking advantage of locally-elevated 14C at Oak Ridge Tennessee, which shows that carbon making up new roots was photosynthesized approximately 1.5 years prior to new root growth. Position on the root branching system shows a correlation with age, with ages up to 7 years for 4th order roots of red maple. The method by which roots are sampled also affects the 14C-estimated age, with total fine root population, sampled via soil cores, showing longer lifespans relative to roots sampled by position on the root branch system (when similar diameter classes are compared). Overall, the implication of our studies is that assumptions of turnover times of 1 year result in underestimates of the true lifespan of a large portion of fine root biomass in temperate forests. This suggests that future calculations of belowground net primary

  7. Fine root respiration in the mangrove Rhizophora mangle over variation in forest stature and nutrient availability.

    PubMed

    Lovelock, Catherine E; Ruess, Roger W; Feller, Ilka C

    2006-12-01

    Root respiration uses a significant proportion of photosynthetically fixed carbon (C) and is a globally important source of C liberated from soils. Mangroves, which are an important and productive forest resource in many tropical and subtropical countries, sustain a high ratio of root to shoot biomass which may indicate that root respiration is a particularly important component in mangrove forest carbon budgets. Mangroves are often exposed to nutrient pollution from coastal waters. Here we assessed the magnitude of fine root respiration in mangrove forests in Belize and investigated how root respiration is influenced by nutrient additions. Respiration rates of excised fine roots of the mangrove, Rhizophora mangle L., were low (4.01 +/- 0.16 nmol CO(2) g(-1) s(-1)) compared to those measured in temperate tree species at similar temperatures. In an experiment where trees where fertilized with nitrogen (N) or phosphorus (P) in low productivity dwarf forests (1-2 m height) and more productive, taller (4- 7 m height) seaward fringing forests, respiration of fine roots did not vary consistently with fertilization treatments or with forest stature. Fine roots of taller fringe trees had higher concentrations of both N and P compared to dwarf trees. Fertilization with P enhanced fine root P concentrations in both dwarf and fringe trees, but reduced root N concentrations compared to controls. Fertilization with N had no effect on root N or P concentrations. Unlike photosynthetic C gain and growth, which is strongly limited by P availability in dwarf forests at this site, fine root respiration (expressed on a mass basis) was variable, but showed no significant enhancements with nutrient additions. Variation in fine root production and standing biomass are, therefore, likely to be more important factors determining C efflux from mangrove sediments than variations in fine root respiration per unit mass. PMID:17169899

  8. Fine Root Mortality Rates in a Temperate Forest: Estimates using Radiocarbon Data and Numerical Modeling

    SciTech Connect

    Riley, William J.; Gaudinski, Julia B.; Torn, Margaret S.; JoslinJr., John D.; Hanson, Paul J

    2009-01-01

    Carbon (C) fluxes through roots are the most uncertain of all C exchanges between the atmosphere, plants, and soil. Yet the three dominant methods to characterize root C fluxes (minirhizotron, sequential coring, and isotopes) yield significantly different estimates of temperate forest root mortality turnover times. We contend that these discrepancies result from limitations in interpreting these very distinct types of observations. In this study we used a whole-ecosystem 14C label to develop, parameterize, and test a model (Radix1.0) of fine-root mortality and decomposition. Radix simulates two live roots pools (one with structural and non-structural C components), two dead root pools, non-normally distributed root mortality turnover times, a stored C pool, seasonal growth and respiration patterns, a best-fit to measurements approach to estimate model parameters, and Monte Carlo uncertainty analysis. We applied Radix at a temperate forest in Oak Ridge Tennessee using 14C measurements from two root size classes (<0.5 mm and 0.5−2.0 mm) and three soil depth increments (O horizon, 0−15, and 30−60 cm). Predicted root lifetimes were 0.1-0.9 y and 11-14 y for fast and slow live root pools respectively, and 0.1-4 y and 11-14 y for fast and slow dead root pool decomposition turnover times, respectively. We estimated that C fluxes through fine roots <2 mm diameter are ~40, 220, and 90 g C m-2 y 1 in the O horizon, 0−15 cm, and 30−60 cm depth intervals, respectively. We conclude that accurate characterization of C flows through fine roots required a model with two live fine-root pools, two dead fine-root pools, and root respiration. Further, root turnover times on the order of a decade imply different response times in biomass and growth than are currently predicted by models with a single annual turnover pool.

  9. Strigolactones Effects on Root Growth

    NASA Astrophysics Data System (ADS)

    Koltai, Hinanit

    2012-07-01

    Strigolactones (SLs) were defined as a new group of plant hormones that suppress lateral shoot branching. Our previous studies suggested SLs to be regulators of root development. SLs were shown to alter root architecture by regulating lateral root formation and to affect root hair elongation in Arabidopsis. Another important effect of SLs on root growth was shown to be associated with root directional growth. Supplementation of SLs to roots led to alterations in root directional growth, whereas associated mutants showed asymmetrical root growth, which was influenced by environmental factors. The regulation by SLs of root development was shown to be conducted via a cross talk of SLs with other plant hormones, including auxin. SLs were shown to regulate auxin transport, and to interfere with the activity of auxin-efflux carriers. Therefore, it might be that SLs are regulators of root directional growth as a result of their ability to regulated auxin transport. However, other evidences suggest a localized effect of SLs on cell division, which may not necessarily be associated with auxin efflux. These and other, recent hypothesis as to the SLs mode of action and the associated root perception and response to environmental factors will be discussed.

  10. Tree species richness affecting fine root biomass in European forests

    NASA Astrophysics Data System (ADS)

    Finér, Leena; Domisch, Timo; Vesterdal, Lars; Dawud, Seid M.; Raulund-Rasmussen, Karsten

    2016-04-01

    Fine roots are an important factor in the forest carbon cycle, contributing significantly to below-ground biomass and soil carbon storage. Therefore it is essential to understand the role of the forest structure, indicated by tree species diversity in controlling below-ground biomass and managing the carbon pools of forest soils. We studied how tree species richness would affect fine root biomass and its distribution in the soil profile and biomass above- and below-ground allocation patterns of different tree species. Our main hypothesis was that increasing tree species richness would lead to below-ground niche differentiation and more efficient soil exploitation by the roots, resulting in a higher fine root biomass in the soil. We sampled fine roots of trees and understorey vegetation in six European forest types in Finland, Poland, Germany, Romania, Italy and Spain, representing boreal, temperate and Mediterranean forests, established within the FunDivEUROPE project for studying the effects of tree species diversity on forest functioning. After determining fine root biomasses, we identified the percentages of different tree species in the fine root samples using the near infrared reflectance spectroscopy (NIRS) method. Opposite to our hypothesis we did not find any general positive relationship between tree species richness and fine root biomass. A weak positive response found in Italy and Spain seemed to be related to dry environmental conditions during Mediterranean summers. At the Polish site where we could sample deeper soil layers (down to 40 cm), we found more tree fine roots in the deeper layers under species-rich forests, as compared to the monocultures, indicating the ability of trees to explore more resources and to increase soil carbon stocks. Tree species richness did not affect biomass allocation patterns between above- and below-ground parts of the trees.

  11. Effects of warming treatment and precipitation manipulation on fine root length of Pinus densiflora seedlings.

    NASA Astrophysics Data System (ADS)

    Han, S. H.; Yoon, S. J.; Lee, J.; Kim, S.; Li, G.; Park, M.; An, J.; Son, Y.

    2015-12-01

    Fine roots are important for water and nutrient uptake and storage of carbon and nutrients in terrestrial ecosystems. In order to examine effects of climate change on fine root of Pinus densiflora seedlings, an open-field experiment with the warming treatment and precipitation manipulation had been conducted at a nursery in Seoul, South Korea. Two-year-old P. seedlings were planted in April, 2013. The air temperature of the warmed plots (W) was set to increase by 3°C compared to the temperature control plots (C) using infrared lamps. The precipitation manipulation consisted of the precipitation decreased using transparent panel (-30%; P-), the precipitation increased using pump and drip-irrigation (+30%; P+), and the precipitation control (0%; P0). The fine root length of the seedlings near the soil surface (0-15 cm depth) was estimated from January, 2014 to January, 2015 trimonthly using minirhizotrons. The mean fine root length (mm mm-2) were 115.0 (WP0), 163.7 (WP-), 90.5 (WP+), 114.4 (CP0), 130.2 (CP-), and 100.6 (CP+) during the study period, respectively. The mean fine root length was significantly affected by the precipitation manipulation (P<0.0001); however, it was not influenced by the warming treatment (P>0.1). There was no interaction between warming and precipitation effects in fine root length. The fine root length in P- plot was higher than those in P0 plot and P+ plot, regardless of the warming treatment, which indicated that water stress caused by P- might stimulate the fine root growth. Meanwhile, the no consistent patterns of fine root length by warming treatment was found under P+ plot and P0 plot, but a positive effect of warming on fine root length was observed under P+ plot only. Estimations of fine root production and mortality are required to determine the interaction between warming and precipitation effects on fine root dynamics more exactly. This study was supported by Korea Ministry of Environment (2014001310008).

  12. Fine Roots – functional definition expanded to crop species

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A recent review (McCormack et al., 2015) proposes to split fine roots (roots less than 2 mm diameter) into two different functional groups: Absorptive and Transport. This is a significant step forward to account for some of the previous comments by Pregitzer (2002) and Zobel (2003) on the situatio...

  13. Dynamics of fine roots in five Chinese temperate forests

    SciTech Connect

    Quan, Xiankuai; Wang, Chuankuan; Zhang, Q.; Wang, X.; Luo, Y.; Bond-Lamberty, Benjamin

    2010-07-01

    Quantifying fine root production and mortality is crucially needed for modeling forest ecosystem carbon cycling, but the fine root dynamics are poorly understood in Chinese temperate forests. We used a minirhizotron method to investigate spatial and temporal dynamics of fine roots (diameter ≤ 2 mm) in five representative temperate forests in northeastern China. Our specific objectives were to: (1) compare standing crop, production and mortality of fine roots among the five stands; (2) examine fine root phenology for the stands; and (3) examine vertical distribution patterns of fine roots for the stands. Fine root dynamics were significantly affected by forest type, soil layer, sampling time and their interactions. The mean values of fine root standing crop varied from 8.0 to 12.8 mm cm-2; those of production varied from 0.027 to 0.046 mm cm-2 d-1; and those of mortality varied from 0.013 to 0.024 mm cm-2 d-1. All stands had a similar seasonal “sinusoidal” pattern of fine root standing crop, and a “unimodal” pattern of production. However, the seasonal dynamics of the mortality was unsynchronized with that of the production. The minimum values of standing crop, production and mortality occurred in March for all stands, while the maximum values and occurring time differed among forest types. The occurrence of the maximum standing crop varied from DOY (day of year) 222 for the oak stand to DOY 271 for the aspen-birch stand; that of the maximum production varied from DOY 188 for the pine and hardwood stands to DOY 239 for the larch stand; and that of the maximum mortality varied from DOY 222 for the oak and aspen-birch stands to DOY 287 for the larch stand. The standing crop, production and mortality of fine roots tended to decrease with soil depths, of which the relative contribution at 0 -10 cm depth averaged 38%, 46%, and 58% of total, respectively. The fact that the production was approximate twice as great as the mortality suggested a net carbon input to

  14. MES Buffer Affects Arabidopsis Root Apex Zonation and Root Growth by Suppressing Superoxide Generation in Root Apex.

    PubMed

    Kagenishi, Tomoko; Yokawa, Ken; Baluška, František

    2016-01-01

    In plants, growth of roots and root hairs is regulated by the fine cellular control of pH and reactive oxygen species (ROS). MES, 2-(N-morpholino)ethanesulfonic acid as one of the Good's buffers has broadly been used for buffering medium, and it is thought to suit for plant growth with the concentration at 0.1% (w/v) because the buffer capacity of MES ranging pH 5.5-7.0 (for Arabidopsis, pH 5.8). However, many reports have shown that, in nature, roots require different pH values on the surface of specific root apex zones, namely meristem, transition zone, and elongation zone. Despite the fact that roots always grow on a media containing buffer molecule, little is known about impact of MES on root growth. Here, we have checked the effects of different concentrations of MES buffer using growing roots of Arabidopsis thaliana. Our results show that 1% of MES significantly inhibited root growth, the number of root hairs and length of meristem, whereas 0.1% promoted root growth and root apex area (region spanning from the root tip up to the transition zone). Furthermore, superoxide generation in root apex disappeared at 1% of MES. These results suggest that MES disturbs normal root morphogenesis by changing the ROS homeostasis in root apex. PMID:26925066

  15. MES Buffer Affects Arabidopsis Root Apex Zonation and Root Growth by Suppressing Superoxide Generation in Root Apex

    PubMed Central

    Kagenishi, Tomoko; Yokawa, Ken; Baluška, František

    2016-01-01

    In plants, growth of roots and root hairs is regulated by the fine cellular control of pH and reactive oxygen species (ROS). MES, 2-(N-morpholino)ethanesulfonic acid as one of the Good’s buffers has broadly been used for buffering medium, and it is thought to suit for plant growth with the concentration at 0.1% (w/v) because the buffer capacity of MES ranging pH 5.5–7.0 (for Arabidopsis, pH 5.8). However, many reports have shown that, in nature, roots require different pH values on the surface of specific root apex zones, namely meristem, transition zone, and elongation zone. Despite the fact that roots always grow on a media containing buffer molecule, little is known about impact of MES on root growth. Here, we have checked the effects of different concentrations of MES buffer using growing roots of Arabidopsis thaliana. Our results show that 1% of MES significantly inhibited root growth, the number of root hairs and length of meristem, whereas 0.1% promoted root growth and root apex area (region spanning from the root tip up to the transition zone). Furthermore, superoxide generation in root apex disappeared at 1% of MES. These results suggest that MES disturbs normal root morphogenesis by changing the ROS homeostasis in root apex. PMID:26925066

  16. Dynamics of fine roots in five Chinese temperate forests.

    PubMed

    Quan, Xiankuai; Wang, Chuankuan; Zhang, Quanzhi; Wang, Xingchang; Luo, Yiqi; Bond-Lamberty, Ben

    2010-07-01

    We used a minirhizotron method to investigate spatial and temporal dynamics of fine roots (diameter < or =2 mm) in five Chinese temperate forests: Mongolian oak forest, aspen-birch forest, hardwood forest, Korean pine plantation and Dahurian larch plantation. Fine root dynamics were significantly influenced by forest type, soil layer, and sampling time. The grand mean values varied from 1.99 to 3.21 mm cm(-2) (root length per minirhizotron viewing area) for the fine root standing crop; from 6.7 to 11.6 microm cm(-2) day(-1) for the production; and from 3.2 to 6.1 microm cm(-2) day(-1) for the mortality. All forests had a similar seasonal "sinusoidal" pattern of standing crop, and a "unimodal" pattern of production. However, the seasonal dynamics of the mortality were largely unsynchronized with those of the production. The minimum values of standing crop, production and mortality occurred in March for all forests, whereas the maximum values and occurrence time differed among forest types. The standing crop, production and mortality tended to decrease with soil depth. The different spatiotemporal patterns of fine roots among the forests highlight the need for forest-specific measurements and modeling of fine root dynamics and forest carbon allocation. PMID:20217175

  17. Acclimation of fine root respiration to soil warming involves starch deposition in very fine and fine roots: a case study in Fagus sylvatica saplings.

    PubMed

    Di Iorio, Antonino; Giacomuzzi, Valentino; Chiatante, Donato

    2016-03-01

    Root activities in terms of respiration and non-structural carbohydrates (NSC) storage and mobilization have been suggested as major physiological roles in fine root lifespan. As more frequent heat waves and drought periods within the next decades are expected, to what extent does thermal acclimation in fine roots represent a mechanism to cope with such upcoming climatic conditions? In this study, the possible changes in very fine (diameter < 0.5 mm) and fine (0.5-1 mm) root morphology and physiology in terms of respiration rate and NSC [soluble sugars (SS) and starch] concentrations, were investigated on 2-year-old Fagus sylvatica saplings subjected to a simulated long-lasting heat wave event and to co-occurring soil drying. For both very fine and fine roots, soil temperature (ST) resulted inversely correlated with specific root length, respiration rates and SSs concentration, but directly correlated with root mass, root tissue density and starch concentration. In particular, starch concentration increased under 28 °C for successively decreasing under 21 °C ST. These findings showed that thermal acclimation in very fine and fine roots due to 24 days exposure to high ST (∼ 28 °C), induced starch accumulation. Such 'carbon-savings strategy' should bear the maintenance costs associated to the recovery process in case of restored favorable environmental conditions, such as those occurring at the end of a heat wave event. Drought condition seems to affect the fine root vitality much more under moderate than high temperature condition, making the temporary exposure to high ST less threatening to root vitality than expected.

  18. [Seasonal dynamics of carbon and nitrogen in fine roots and their differences between successive rotation poplar plantations].

    PubMed

    Wang, Yan-ping; Xu, Tan; Zhu, Wan-rui; Wang, Hua-tian; Zhang, Guang-can; Li, Chuan-rong; Jiang, Yue-zhong

    2015-11-01

    In this study, poplar fine roots in two successive rotation plantations were sampled over seasons. Root samples were grouped from first to five orders to examine the seasonal dynamics of carbon and nitrogen contents of poplar fine roots with orders, and compared their differences between two successive rotation plantations, and finally to find the relationships between the fine root growth and the productivity decline of successive rotation poplar plantations. The results showed that non-structure carbohydrates (NSC) content increased significantly with root orders, while nitrogen content decreased. The contents of total carbon and NSC were significantly related to total nitrogen content. Root orders explained 98.2% variance of carbon and nitrogen contents of poplar fine roots, and the difference between rotations only explained 1.7% of variance. Poplar fine roots consisted of more carbon and less nitrogen with root orders, and the seasonal changes in contents of total carbon, total nitrogen and NSC showed significant difference between rotations, while.that of the C:N ratio didn' t show significant difference. Root order and season showed interaction effect on carbon and nitrogen dynamic. The C:N ratio was about 20:1 in lower order roots, and more than 30:1 in higher order roots. The C:N ratio in summer and autumn was significantly less than those in other seasons, while NSC content was the highest in November. This study indicated that the allocation of carbon and nitrogen in fine roots was closely correlated with fine root orders. Both NSC content and C:N ratio were of greatly important ecological significance in fine root turnover and growth regulation.

  19. Changes in fine-root production, phenology and spatial distribution in response to N application in irrigated sweet cherry trees.

    PubMed

    Artacho, Pamela; Bonomelli, Claudia

    2016-05-01

    Factors regulating fine-root growth are poorly understood, particularly in fruit tree species. In this context, the effects of N addition on the temporal and spatial distribution of fine-root growth and on the fine-root turnover were assessed in irrigated sweet cherry trees. The influence of other exogenous and endogenous factors was also examined. The rhizotron technique was used to measure the length-based fine-root growth in trees fertilized at two N rates (0 and 60 kg ha(-1)), and the above-ground growth, leaf net assimilation, and air and soil variables were simultaneously monitored. N fertilization exerted a basal effect throughout the season, changing the magnitude, temporal patterns and spatial distribution of fine-root production and mortality. Specifically, N addition enhanced the total fine-root production by increasing rates and extending the production period. On average, N-fertilized trees had a length-based production that was 110-180% higher than in control trees, depending on growing season. Mortality was proportional to production, but turnover rates were inconsistently affected. Root production and mortality was homogeneously distributed in the soil profile of N-fertilized trees while control trees had 70-80% of the total fine-root production and mortality concentrated below 50 cm depth. Root mortality rates were associated with soil temperature and water content. In contrast, root production rates were primarily under endogenous control, specifically through source-sink relationships, which in turn were affected by N supply through changes in leaf photosynthetic level. Therefore, exogenous and endogenous factors interacted to control the fine-root dynamics of irrigated sweet cherry trees.

  20. Changes in fine-root production, phenology and spatial distribution in response to N application in irrigated sweet cherry trees.

    PubMed

    Artacho, Pamela; Bonomelli, Claudia

    2016-05-01

    Factors regulating fine-root growth are poorly understood, particularly in fruit tree species. In this context, the effects of N addition on the temporal and spatial distribution of fine-root growth and on the fine-root turnover were assessed in irrigated sweet cherry trees. The influence of other exogenous and endogenous factors was also examined. The rhizotron technique was used to measure the length-based fine-root growth in trees fertilized at two N rates (0 and 60 kg ha(-1)), and the above-ground growth, leaf net assimilation, and air and soil variables were simultaneously monitored. N fertilization exerted a basal effect throughout the season, changing the magnitude, temporal patterns and spatial distribution of fine-root production and mortality. Specifically, N addition enhanced the total fine-root production by increasing rates and extending the production period. On average, N-fertilized trees had a length-based production that was 110-180% higher than in control trees, depending on growing season. Mortality was proportional to production, but turnover rates were inconsistently affected. Root production and mortality was homogeneously distributed in the soil profile of N-fertilized trees while control trees had 70-80% of the total fine-root production and mortality concentrated below 50 cm depth. Root mortality rates were associated with soil temperature and water content. In contrast, root production rates were primarily under endogenous control, specifically through source-sink relationships, which in turn were affected by N supply through changes in leaf photosynthetic level. Therefore, exogenous and endogenous factors interacted to control the fine-root dynamics of irrigated sweet cherry trees. PMID:26888890

  1. Effects of soil moisture manipulations on fine root dynamics in a mature balsam fir (Abies balsamea L. Mill.) forest.

    PubMed

    Olesinski, Jakub; Lavigne, Michael B; Krasowski, Marek J

    2011-03-01

    We tested the hypothesis that moisture stress affects fine root dynamics during and after the stress. To this end, we investigated the effects of soil moisture on annual and seasonal fine root production and mortality over 4 years in a mature balsam fir (Abies balsamea L. Mill.) stand using a minirhizotron and soil coring. Droughting and irrigating treatments were imposed for 17 weeks during the third year of the study, and post-treatment recovery was measured during the fourth year. Monthly fine root production was often reduced by low soil water content (SWC) during July-September in the pre-treatment years and by imposed drought. Irrigation resulted in higher summer fine root production than in pre-treatment years. In the recovery year, increased fine root production was observed in the previously droughted plots despite low SWC in August and September. Droughting decreased year-end fine root biomass in the treatment year, but biomass returned to pre-treatment levels during the recovery year. Droughting and irrigating did not affect foliage production during the treatment and recovery years. Our results suggest that for balsam fir, establishment and maintenance of a functional balance between foliage and fine root biomass, with respect to moisture supply and demand, can depend on fine root dynamics occurring over more than one growing season. In addition, our findings provided insights into tree growth responses to interannual variation in moisture supply.

  2. Do ectomycorrhizal and arbuscular mycorrhizal temperate tree species systematically differ in root order-related fine root morphology and biomass?

    PubMed Central

    Kubisch, Petra; Hertel, Dietrich; Leuschner, Christoph

    2015-01-01

    While most temperate broad-leaved tree species form ectomycorrhizal (EM) symbioses, a few species have arbuscular mycorrhizas (AM). It is not known whether EM and AM tree species differ systematically with respect to fine root morphology, fine root system size and root functioning. In a species-rich temperate mixed forest, we studied the fine root morphology and biomass of three EM and three AM tree species from the genera Acer, Carpinus, Fagus, Fraxinus, and Tilia searching for principal differences between EM and AM trees. We further assessed the evidence of convergence or divergence in root traits among the six co-occurring species. Eight fine root morphological and chemical traits were investigated in root segments of the first to fourth root order in three different soil depths and the relative importance of the factors root order, tree species and soil depth for root morphology was determined. Root order was more influential than tree species while soil depth had only a small effect on root morphology All six species showed similar decreases in specific root length and specific root area from the 1st to the 4th root order, while the species patterns differed considerably in root tissue density, root N concentration, and particularly with respect to root tip abundance. Most root morphological traits were not significantly different between EM and AM species (except for specific root area that was larger in AM species), indicating that mycorrhiza type is not a key factor influencing fine root morphology in these species. The order-based root analysis detected species differences more clearly than the simple analysis of bulked fine root mass. Despite convergence in important root traits among AM and EM species, even congeneric species may differ in certain fine root morphological traits. This suggests that, in general, species identity has a larger influence on fine root morphology than mycorrhiza type. PMID:25717334

  3. Estimation of fine-root production using rates of diameter-dependent root mortality, decomposition and thickening in forests.

    PubMed

    Van Do, Tran; Osawa, Akira; Sato, Tamotsu

    2016-04-01

    Current studies indicate that fine roots of different diameter classes show different rates of decomposition. This study developed a new method to estimate fine-root production by considering the difference in the production of fine roots of two size classes, fine roots thinner than 1 mm and those between 1 and 2 mm, and their corresponding rates of decomposition. A litter bag experiment was used to estimate the decomposition rates, while the sequential soil core technique was used to identify mass values of live roots and dead roots at a given period of observation. The continuous inflow method was applied to estimate the amount of root decomposition, mortality and production with a framework of two diameter classes of fine roots and for quantification of the amount of mass transfer from the thicker fine-root class to the coarser root category (>2 mm). The results indicated that the estimate of fine-root production was greater when two size classes of fine roots were distinguished. Using a framework of two size classes developed in this study resulted in 21.3% higher fine-root production than a method that did not recognize fine-root size classes or mass transfer to the category of coarse roots. In addition, using shorter collection intervals led to higher production estimates than longer intervals. The production estimate with a 1-month interval was 21.4% higher than that with a 6-month interval. We consider that the use of the sequential soil core technique with continuous inflow estimate method by differentiating size classes of fine roots is likely to minimize the underestimation of the parameters of fine-root dynamics by accounting for decomposition and mortality of fine roots more appropriately.

  4. Fine root dynamics for forests on contrasting soils in the Colombian Amazon

    NASA Astrophysics Data System (ADS)

    Jiménez, E. M.; Moreno, F. H.; Peñuela, M. C.; Patiño, S.; Lloyd, J.

    2009-12-01

    It has been hypothesized that as soil fertility increases, the amount of carbon allocated to below-ground production (fine roots) should decrease. To evaluate this hypothesis, we measured the standing crop fine root mass and the production of fine roots (<2 mm) by two methods: (1) ingrowth cores and, (2) sequential soil coring, during 2.2 years in two lowland forests growing on different soils types in the Colombian Amazon. Differences of soil resources were defined by the type and physical and chemical properties of soil: a forest on clay loam soil (Endostagnic Plinthosol) at the Amacayacu National Natural Park and, the other on white sand (Ortseinc Podzol) at the Zafire Biological Station, located in the Forest Reservation of the Calderón River. We found that the standing crop fine root mass and the production was significantly different between soil depths (0-10 and 10-20 cm) and also between forests. The loamy sand forest allocated more carbon to fine roots than the clay loam forest with the production in loamy sand forest twice (mean±standard error=2.98±0.36 and 3.33±0.69 Mg C ha-1 yr-1, method 1 and 2, respectively) as much as for the more fertile loamy soil forest (1.51±0.14, method 1, and from 1.03±0.31 to 1.36±0.23 Mg C ha-1 yr-1, method 2). Similarly, the average of standing crop fine root mass was higher in the white-sands forest (10.94±0.33 Mg C ha-1) as compared to the forest on the more fertile soil (from 3.04±0.15 to 3.64±0.18 Mg C ha-1). The standing crop fine root mass also showed a temporal pattern related to rainfall, with the production of fine roots decreasing substantially in the dry period of the year 2005. These results suggest that soil resources may play an important role in patterns of carbon allocation to the production of fine roots in these forests as the proportion of carbon allocated to above- and below-ground organs is different between forest types. Thus, a trade-off between above- and below-ground growth seems to exist

  5. [Distribution of fine root biomass of main planting tree species in Loess Plateau, China].

    PubMed

    Jian, Sheng-Qi; Zhao, Chuan-Yan; Fang, Shu-Min; Yu, Kai

    2014-07-01

    The distribution of fine roots of Pinus tabuliformis, Populus tomentosa, Prunus armeniaca, Robinia pseudoacacia, Hippophae rhamnoides, and Caragana korshinskii was investigated by using soil core method and the fine root was defined as root with diameter less than 2 mm. The soil moisture and soil properties were measured. The results showed that in the horizontal direction, the distribution of fine root biomass of P. tabuliformis presented a conic curve, and the fine root biomass of the other species expressed logarithm correlation. Radial roots developed, the fine root biomass were concentrated within the scope of the 2-3 times crown, indicating that trees extended their roots laterally to seek water farther from the tree. In the vertical direction, the fine root biomass decreased with the increasing soil depth. Fine root biomass had significant negative correlation with soil water content and bulk density, while significant positive correlation with organic matter and total N contents.

  6. OPTIMIZING MINIRHIZOTRON SAMPLE FREQUENCY FOR ESTIMATING FINE ROOT PRODUCTION AND TURNOVER

    EPA Science Inventory

    The most frequent reason for using minirhizotrons in natural ecosystems is the determination of fine root production and turnover. Our objective is to determine the optimum sampling frequency for estimating fine root production and turnover using data from evergreen (Pseudotsuga ...

  7. ASSESSING THE EFFECTS OF GLOBAL CLIMATE CHANGE ON THE PRODUCTION AND MORTALITY OF DOUGLAS FIR FINE ROOTS USING MINIRHIZOTRONS

    EPA Science Inventory

    Fine roots (roots 2 mm in diameter) are one of the principal absorptive surfaces for water and nutrients in terrestrial plants. As such they are vital for plant growth and survival, while their turnover serves as a primary mechanism for carbon addition to soil. Little is known...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  9. Redefining fine roots improves understanding of below-ground contributions to terrestrial biosphere processes.

    PubMed

    McCormack, M Luke; Dickie, Ian A; Eissenstat, David M; Fahey, Timothy J; Fernandez, Christopher W; Guo, Dali; Helmisaari, Heljä-Sisko; Hobbie, Erik A; Iversen, Colleen M; Jackson, Robert B; Leppälammi-Kujansuu, Jaana; Norby, Richard J; Phillips, Richard P; Pregitzer, Kurt S; Pritchard, Seth G; Rewald, Boris; Zadworny, Marcin

    2015-08-01

    Fine roots acquire essential soil resources and mediate biogeochemical cycling in terrestrial ecosystems. Estimates of carbon and nutrient allocation to build and maintain these structures remain uncertain because of the challenges of consistently measuring and interpreting fine-root systems. Traditionally, fine roots have been defined as all roots ≤ 2 mm in diameter, yet it is now recognized that this approach fails to capture the diversity of form and function observed among fine-root orders. Here, we demonstrate how order-based and functional classification frameworks improve our understanding of dynamic root processes in ecosystems dominated by perennial plants. In these frameworks, fine roots are either separated into individual root orders or functionally defined into a shorter-lived absorptive pool and a longer-lived transport fine-root pool. Using these frameworks, we estimate that fine-root production and turnover represent 22% of terrestrial net primary production globally - a c. 30% reduction from previous estimates assuming a single fine-root pool. Future work developing tools to rapidly differentiate functional fine-root classes, explicit incorporation of mycorrhizal fungi into fine-root studies, and wider adoption of a two-pool approach to model fine roots provide opportunities to better understand below-ground processes in the terrestrial biosphere.

  10. Redefining fine roots improves understanding of belowground contributions to terrestrial biosphere processes

    SciTech Connect

    McCormack, M. Luke; Dickie, Ian A.; Eissenstat, David M.; Fahey, Timothy J.; Fernandez, Christopher W.; Guo, Dali; Helmisaari, Helja -Sisko; Hobbie, Erik A.; Iversen, Colleen M.; Jackson, Robert B.; Leppälammi-Kujansuu, Jaana; Norby, Richard J.; Phillips, Richard P.; Pregitzer, Kurt S.; Pritchard, Seth G.; Rewald, Boris; Zadworny, Marcin

    2015-03-10

    Fine roots acquire essential soil resources and mediate biogeochemical cycling in terrestrial ecosystems. Estimates of carbon and nutrient allocation to build and maintain these structures remain uncertain due to challenges in consistent measurement and interpretation of fine-root systems. We define fine roots as all roots less than or equal to 2 mm in diameter, yet it is now recognized that this approach fails to capture the diversity of form and function observed among fine-root orders. We demonstrate how order-based and functional classification frameworks improve our understanding of dynamic root processes in ecosystems dominated by perennial plants. In these frameworks, fine roots are separated into either individual root orders or functionally defined into a shorter-lived absorptive pool and a longer-lived transport fine root pool. Furthermore, using these frameworks, we estimate that fine-root production and turnover represent 22% of terrestrial net primary production globally a ca. 30% reduction from previous estimates assuming a single fine-root pool. In the future we hope to develop tools to rapidly differentiate functional fine-root classes, explicit incorporation of mycorrhizal fungi in fine-root studies, and wider adoption of a two-pool approach to model fine roots provide opportunities to better understand belowground processes in the terrestrial biosphere.

  11. Fine root dynamics in lodgepole pine and white spruce stands along productivity gradients in reclaimed oil sands sites.

    PubMed

    Jamro, Ghulam Murtaza; Chang, Scott X; Naeth, M Anne; Duan, Min; House, Jason

    2015-10-01

    Open-pit mining activities in the oil sands region of Alberta, Canada, create disturbed lands that, by law, must be reclaimed to a land capability equivalent to that existed before the disturbance. Re-establishment of forest cover will be affected by the production and turnover rate of fine roots. However, the relationship between fine root dynamics and tree growth has not been studied in reclaimed oil sands sites. Fine root properties (root length density, mean surface area, total root biomass, and rates of root production, turnover, and decomposition) were assessed from May to October 2011 and 2012 using sequential coring and ingrowth core methods in lodgepole pine (Pinus contorta Dougl.) and white spruce (Picea glauca (Moench.) Voss) stands. The pine and spruce stands were planted on peat mineral soil mix placed over tailings sand and overburden substrates, respectively, in reclaimed oil sands sites in Alberta. We selected stands that form a productivity gradient (low, medium, and high productivities) of each tree species based on differences in tree height and diameter at breast height (DBH) increments. In lodgepole pine stands, fine root length density and fine root production, and turnover rates were in the order of high > medium > low productivity sites and were positively correlated with tree height and DBH and negatively correlated with soil salinity (P < 0.05). In white spruce stands, fine root surface area was the only parameter that increased along the productivity gradient and was negatively correlated with soil compaction. In conclusion, fine root dynamics along the stand productivity gradients were closely linked to stand productivity and were affected by limiting soil properties related to the specific substrate used for reconstructing the reclaimed soil. Understanding the impact of soil properties on fine root dynamics and overall stand productivity will help improve land reclamation outcomes. PMID:26668730

  12. Fine root dynamics in lodgepole pine and white spruce stands along productivity gradients in reclaimed oil sands sites.

    PubMed

    Jamro, Ghulam Murtaza; Chang, Scott X; Naeth, M Anne; Duan, Min; House, Jason

    2015-10-01

    Open-pit mining activities in the oil sands region of Alberta, Canada, create disturbed lands that, by law, must be reclaimed to a land capability equivalent to that existed before the disturbance. Re-establishment of forest cover will be affected by the production and turnover rate of fine roots. However, the relationship between fine root dynamics and tree growth has not been studied in reclaimed oil sands sites. Fine root properties (root length density, mean surface area, total root biomass, and rates of root production, turnover, and decomposition) were assessed from May to October 2011 and 2012 using sequential coring and ingrowth core methods in lodgepole pine (Pinus contorta Dougl.) and white spruce (Picea glauca (Moench.) Voss) stands. The pine and spruce stands were planted on peat mineral soil mix placed over tailings sand and overburden substrates, respectively, in reclaimed oil sands sites in Alberta. We selected stands that form a productivity gradient (low, medium, and high productivities) of each tree species based on differences in tree height and diameter at breast height (DBH) increments. In lodgepole pine stands, fine root length density and fine root production, and turnover rates were in the order of high > medium > low productivity sites and were positively correlated with tree height and DBH and negatively correlated with soil salinity (P < 0.05). In white spruce stands, fine root surface area was the only parameter that increased along the productivity gradient and was negatively correlated with soil compaction. In conclusion, fine root dynamics along the stand productivity gradients were closely linked to stand productivity and were affected by limiting soil properties related to the specific substrate used for reconstructing the reclaimed soil. Understanding the impact of soil properties on fine root dynamics and overall stand productivity will help improve land reclamation outcomes.

  13. Redefining fine roots improves understanding of belowground contributions to terrestrial biosphere processes

    DOE PAGESBeta

    McCormack, M. Luke; Dickie, Ian A.; Eissenstat, David M.; Fahey, Timothy J.; Fernandez, Christopher W.; Guo, Dali; Helmisaari, Helja -Sisko; Hobbie, Erik A.; Iversen, Colleen M.; Jackson, Robert B.; et al

    2015-03-10

    Fine roots acquire essential soil resources and mediate biogeochemical cycling in terrestrial ecosystems. Estimates of carbon and nutrient allocation to build and maintain these structures remain uncertain due to challenges in consistent measurement and interpretation of fine-root systems. We define fine roots as all roots less than or equal to 2 mm in diameter, yet it is now recognized that this approach fails to capture the diversity of form and function observed among fine-root orders. We demonstrate how order-based and functional classification frameworks improve our understanding of dynamic root processes in ecosystems dominated by perennial plants. In these frameworks, finemore » roots are separated into either individual root orders or functionally defined into a shorter-lived absorptive pool and a longer-lived transport fine root pool. Furthermore, using these frameworks, we estimate that fine-root production and turnover represent 22% of terrestrial net primary production globally a ca. 30% reduction from previous estimates assuming a single fine-root pool. In the future we hope to develop tools to rapidly differentiate functional fine-root classes, explicit incorporation of mycorrhizal fungi in fine-root studies, and wider adoption of a two-pool approach to model fine roots provide opportunities to better understand belowground processes in the terrestrial biosphere.« less

  14. The decomposition of fine and coarse roots: their global patterns and controlling factors.

    PubMed

    Zhang, Xinyue; Wang, Wei

    2015-05-05

    Fine root decomposition represents a large carbon (C) cost to plants, and serves as a potential soil C source, as well as a substantial proportion of net primary productivity. Coarse roots differ markedly from fine roots in morphology, nutrient concentrations, functions, and decomposition mechanisms. Still poorly understood is whether a consistent global pattern exists between the decomposition of fine (<2 mm root diameter) and coarse (≥2 mm) roots. A comprehensive terrestrial root decomposition dataset, including 530 observations from 71 sampling sites, was thus used to compare global patterns of decomposition of fine and coarse roots. Fine roots decomposed significantly faster than coarse roots in middle latitude areas, but their decomposition in low latitude regions was not significantly different from that of coarse roots. Coarse root decomposition showed more dependence on climate, especially mean annual temperature (MAT), than did fine roots. Initial litter lignin content was the most important predictor of fine root decomposition, while lignin to nitrogen ratios, MAT, and mean annual precipitation were the most important predictors of coarse root decomposition. Our study emphasizes the necessity of separating fine roots and coarse roots when predicting the response of belowground C release to future climate changes.

  15. Root growth dynamics linked to above-ground growth in walnut (Juglans regia)

    PubMed Central

    Contador, Maria Loreto; Comas, Louise H.; Metcalf, Samuel G.; Stewart, William L.; Porris Gomez, Ignacio; Negron, Claudia; Lampinen, Bruce D.

    2015-01-01

    Background and Aims Examination of plant growth below ground is relatively scant compared with that above ground, and is needed to understand whole-plant responses to the environment. This study examines whether the seasonal timing of fine root growth and the spatial distribution of this growth through the soil profile varies in response to canopy manipulation and soil temperature. Methods Plasticity in the seasonal timing and vertical distribution of root production in response to canopy and soil water manipulation was analysed in field-grown walnut (Juglans regia ‘Chandler’) using minirhizotron techniques. Key Results Root production in walnuts followed a unimodal curve, with one marked flush of root growth starting in mid-May, with a peak in mid-June. Root production declined later in the season, corresponding to increased soil temperature, as well as to the period of major carbohydrate allocation to reproduction. Canopy and soil moisture manipulation did not influence the timing of root production, but did influence the vertical distribution of roots through the soil profile. Water deficit appeared to promote root production in deeper soil layers for mining soil water. Canopy removal appeared to promote shallow root production. Conclusions The findings of this study add to growing evidence that root growth in many ecosystems follows a unimodal curve with one marked flush of root growth in coordination with the initial leaf flush of the season. Root vertical distribution appeared to have greater plasticity than timing of root production in this system, with temperature and/or carbohydrate competition constraining the timing of root growth. Effects on root distribution can have serious impacts on trees, with shallow rooting having negative impacts in years with limited soil water or positive impacts in years with wet springs, and deep rooting having positive impacts on soil water mining from deeper soil layers but negative impacts in years with wet springs

  16. New theories of root growth modelling

    NASA Astrophysics Data System (ADS)

    Landl, Magdalena; Schnepf, Andrea; Vanderborght, Jan; Huber, Katrin; Javaux, Mathieu; Bengough, A. Glyn; Vereecken, Harry

    2016-04-01

    In dynamic root architecture models, root growth is represented by moving root tips whose line trajectory results in the creation of new root segments. Typically, the direction of root growth is calculated as the vector sum of various direction-affecting components. However, in our simulations this did not reproduce experimental observations of root growth in structured soil. We therefore developed a new approach to predict the root growth direction. In this approach we distinguish between, firstly, driving forces for root growth, i.e. the force exerted by the root which points in the direction of the previous root segment and gravitropism, and, secondly, the soil mechanical resistance to root growth or penetration resistance. The latter can be anisotropic, i.e. depending on the direction of growth, which leads to a difference between the direction of the driving force and the direction of the root tip movement. Anisotropy of penetration resistance can be caused either by microscale differences in soil structure or by macroscale features, including macropores. Anisotropy at the microscale is neglected in our model. To allow for this, we include a normally distributed random deflection angle α to the force which points in the direction of the previous root segment with zero mean and a standard deviation σ. The standard deviation σ is scaled, so that the deflection from the original root tip location does not depend on the spatial resolution of the root system model. Similarly to the water flow equation, the direction of the root tip movement corresponds to the water flux vector while the driving forces are related to the water potential gradient. The analogue of the hydraulic conductivity tensor is the root penetrability tensor. It is determined by the inverse of soil penetration resistance and describes the ease with which a root can penetrate the soil. By adapting the three dimensional soil and root water uptake model R-SWMS (Javaux et al., 2008) in this way

  17. Interspecific coordination and intraspecific plasticity of fine root traits in North American temperate tree species

    PubMed Central

    Tobner, Cornelia M.; Paquette, Alain; Messier, Christian

    2013-01-01

    Fine roots play an important role in nutrient and water absorption and hence overall tree performance. However, current understanding of the ecological role of belowground traits lags considerably behind those of aboveground traits. In this study, we used data on specific root length (SRL), fine root diameter (D) and branching intensity (BI) of two datasets to examine interspecific trait coordination as well as intraspecific trait variation across ontogenetic stage and soil conditions (i.e., plasticity). The first dataset included saplings of 12 North American temperate tree species grown in monocultures in a common garden experiment to examine interspecific trait coordination. The second dataset included adult and juvenile individuals of four species (present in both datasets) co-occurring in natural forests on contrasting soils (i.e., humid organic, mesic, and xeric podzolic).The three fine root traits investigated were strongly coordinated, with high SRL being related to low D and high BI. Fine root traits and aboveground life-strategies (i.e., relative growth rate) were weakly coordinated and never significant. Intraspecific responses to changes in ontogenetic stage or soil conditions were trait dependent. SRL was significantly higher in juveniles compared to adults for Abies balsamea and Acer rubrum, but did not vary with soil condition. BI did not vary significantly with either ontogeny or soil conditions, while D was generally significantly lower in juveniles and higher in humid organic soils. D also had the least total variability most of which was due to changes in the environment (plasticity). This study brings support for the emerging evidence for interspecific root trait coordination in trees. It also indicates that intraspecific responses to both ontogeny and soil conditions are trait dependent and less concerted. D appears to be a better indicator of environmental change than SRL and BI. PMID:23874347

  18. Elevated CO2 and O3 effects on fine-root survivorship in ponderosa pine mesocosms.

    PubMed

    Phillips, Donald L; Johnson, Mark G; Tingey, David T; Storm, Marjorie J

    2009-07-01

    Atmospheric carbon dioxide (CO(2)) and ozone (O(3)) concentrations are rising, which may have opposing effects on tree C balance and allocation to fine roots. More information is needed on interactive CO(2) and O(3) effects on roots, particularly fine-root life span, a critical demographic parameter and determinant of soil C and N pools and cycling rates. We conducted a study in which ponderosa pine (Pinus ponderosa) seedlings were exposed to two levels of CO(2) and O(3) in sun-lit controlled-environment mesocosms for 3 years. Minirhizotrons were used to monitor individual fine roots in three soil horizons every 28 days. Proportional hazards regression was used to analyze effects of CO(2), O(3), diameter, depth, and season of root initiation on fine-root survivorship. More fine roots were produced in the elevated CO(2) treatment than in ambient CO(2). Elevated CO(2), increasing root diameter, and increasing root depth all significantly increased fine-root survivorship and median life span. Life span was slightly, but not significantly, lower in elevated O(3), and increased O(3) did not reduce the effect of elevated CO(2). Median life spans varied from 140 to 448 days depending on the season of root initiation. These results indicate the potential for elevated CO(2) to increase the number of fine roots and their residence time in the soil, which is also affected by root diameter, root depth, and phenology. PMID:19415339

  19. Species-specific fine root biomass distribution alters competition in mixed forests under climate change

    NASA Astrophysics Data System (ADS)

    Reyer, Christopher; Gutsch, Martin; Lasch, Petra; Suckow, Felicitas; Sterck, Frank; Mohren, Frits

    2010-05-01

    The importance of mixed forests in European silviculture has increased due to forest conversion policies and multifunctional forest management. Concurrently, evidences for substantial impacts of climate change on forest ecosystems accumulate. Projected drier and warmer conditions alter the water relations of tree species, their growth and ultimately their inter-specific competition in mixed stands. Process-based models are scientific tools to study the impact of climate change on and to deepen the understanding of the functioning of these systems based on ecological mechanisms. They allow for long-term, stand-level studies of forest dynamics which could only be addressed with great difficulty in an experimental or empirical setup. We used the process-based forest model 4C to simulate inter-specific competition in mixed stands of Douglas-fir (Pseudotsuga menziesii) and Common beech (Fagus sylvatica) as well as Scots pine (Pinus sylvestris) and Sessile / Pedunculate oak (Quercus petraea and Quercus robur) under a) historical climate for model verification and b) under climate change scenario realizations of the climate model STAR 2.0 in Brandenburg, Germany. Some of the climate change scenario realizations feature a substantially drier and warmer summer climate which decreases the climatic water balance during the growing season. We assumed species-specific fine root biomass distributions which feature broadleaved fine roots in deeper soil layers and coniferous fine roots in upper soil layers according to several root excavation studies from mixed stands. The stands themselves were constructed from yield tables of the contributing species. The model verification provided good results for the basal area predictions under the historical climate. Under climate change, the number of days when the tree water demand exceeded the soil water supply was higher for the coniferous species than for broadleaved species. Furthermore, after 45 simulation years the basal area

  20. Elevated CO2 or O3 effects on fine-root survivorship in ponderosa pine

    EPA Science Inventory

    Atmospheric carbon dioxide (CO2) and ozone (O3) concentrations are rising, which may have opposing effects on tree C balance and allocation to fine roots. More information is needed on interactive CO2 and O3 effects on roots, particularly fine-root life span, a critical demograp...

  1. ELEVATED CO2 AND O3 EFFECTS ON FINE-ROOT SURVIVORSHIP IN PONDEROSA PINE MESOCOSMS

    EPA Science Inventory

    Atmospheric carbon dioxide (CO2) and ozone (O3) concentrations are rising, which may have opposing effects on tree C balance and allocation to fine roots. More information is needed on interactive CO2 and O3 effects on roots, particularly fine-root life span, a critical demograph...

  2. Brassinosteroids Regulate Root Growth, Development, and Symbiosis.

    PubMed

    Wei, Zhuoyun; Li, Jia

    2016-01-01

    Brassinosteroids (BRs) are natural plant hormones critical for growth and development. BR deficient or signaling mutants show significantly shortened root phenotypes. However, for a long time, it was thought that these phenotypes were solely caused by reduced cell elongation in the mutant roots. Functions of BRs in regulating root development have been largely neglected. Nonetheless, recent detailed analyses, revealed that BRs are not only involved in root cell elongation but are also involved in many aspects of root development, such as maintenance of meristem size, root hair formation, lateral root initiation, gravitropic response, mycorrhiza formation, and nodulation in legume species. In this review, current findings on the functions of BRs in mediating root growth, development, and symbiosis are discussed.

  3. An Invariant Allometric Scaling of Nitrogen and Phosphorus in Leaves, Stems and Fine roots Along an Altitudinal Gradient

    NASA Astrophysics Data System (ADS)

    Zhao, Ning; He, Nianpeng; Wang, Qiufeng; Wang, Ruili; Xu, Zhiwei; YU, Guirui

    2014-05-01

    Plant nutrient allocation explicitly links the plant resource capture strategy to the material and energy cycles of ecosystems. The nitrogen (N) to phosphorus (P) relationship in plant organs is of particular interest, as N and P are the major limiting elements for plant growth. Here we analyze the relations of N and P in leaves, stems and fine roots of 269 species along an altitudinal transect on the northern slope of Changbai Mountain, China, to explore the partitioning of nutrients in major plant organs and its response to environmental gradient. We find that N, P contents as well as N: P ratio are significantly higher in leaves than in stems and fine roots. Nutrient contents of major plant organs show consistent response to the altitudinal gradient. N and P contents of leaves, stems and fine roots increased while N:P ratios decreased with elevation. Moreover, general allometric scaling relations of N and P is found in leaves, stems and fine roots with slopes of 0.78, 0.72 and 0.87, respectively, and differences exist among different plant growth forms. In general, the exponent values of the allometric scaling of N and P in leaves, stems and fine roots keep as an invariant constant along the altitudinal gradient, which implies the existence of conserved nutrient allocation strategies in plant.

  4. Impact of Heterobasidion root-rot on fine root morphology and associated fungi in Picea abies stands on peat soils.

    PubMed

    Gaitnieks, Talis; Klavina, Darta; Muiznieks, Indrikis; Pennanen, Taina; Velmala, Sannakajsa; Vasaitis, Rimvydas; Menkis, Audrius

    2016-07-01

    We examined differences in fine root morphology, mycorrhizal colonisation and root-inhabiting fungal communities between Picea abies individuals infected by Heterobasidion root-rot compared with healthy individuals in four stands on peat soils in Latvia. We hypothesised that decreased tree vitality and alteration in supply of photosynthates belowground due to root-rot infection might lead to changes in fungal communities of tree roots. Plots were established in places where trees were infected and in places where they were healthy. Within each stand, five replicate soil cores with roots were taken to 20 cm depth in each root-rot infected and uninfected plot. Root morphological parameters, mycorrhizal colonisation and associated fungal communities, and soil chemical properties were analysed. In three stands root morphological parameters and in all stands root mycorrhizal colonisation were similar between root-rot infected and uninfected plots. In one stand, there were significant differences in root morphological parameters between root-rot infected versus uninfected plots, but these were likely due to significant differences in soil chemical properties between the plots. Sequencing of the internal transcribed spacer of fungal nuclear rDNA from ectomycorrhizal (ECM) root morphotypes of P. abies revealed the presence of 42 fungal species, among which ECM basidiomycetes Tylospora asterophora (24.6 % of fine roots examined), Amphinema byssoides (14.5 %) and Russula sapinea (9.7 %) were most common. Within each stand, the richness of fungal species and the composition of fungal communities in root-rot infected versus uninfected plots were similar. In conclusion, Heterobasidion root-rot had little or no effect on fine root morphology, mycorrhizal colonisation and composition of fungal communities in fine roots of P. abies growing on peat soils.

  5. Impact of Heterobasidion root-rot on fine root morphology and associated fungi in Picea abies stands on peat soils.

    PubMed

    Gaitnieks, Talis; Klavina, Darta; Muiznieks, Indrikis; Pennanen, Taina; Velmala, Sannakajsa; Vasaitis, Rimvydas; Menkis, Audrius

    2016-07-01

    We examined differences in fine root morphology, mycorrhizal colonisation and root-inhabiting fungal communities between Picea abies individuals infected by Heterobasidion root-rot compared with healthy individuals in four stands on peat soils in Latvia. We hypothesised that decreased tree vitality and alteration in supply of photosynthates belowground due to root-rot infection might lead to changes in fungal communities of tree roots. Plots were established in places where trees were infected and in places where they were healthy. Within each stand, five replicate soil cores with roots were taken to 20 cm depth in each root-rot infected and uninfected plot. Root morphological parameters, mycorrhizal colonisation and associated fungal communities, and soil chemical properties were analysed. In three stands root morphological parameters and in all stands root mycorrhizal colonisation were similar between root-rot infected and uninfected plots. In one stand, there were significant differences in root morphological parameters between root-rot infected versus uninfected plots, but these were likely due to significant differences in soil chemical properties between the plots. Sequencing of the internal transcribed spacer of fungal nuclear rDNA from ectomycorrhizal (ECM) root morphotypes of P. abies revealed the presence of 42 fungal species, among which ECM basidiomycetes Tylospora asterophora (24.6 % of fine roots examined), Amphinema byssoides (14.5 %) and Russula sapinea (9.7 %) were most common. Within each stand, the richness of fungal species and the composition of fungal communities in root-rot infected versus uninfected plots were similar. In conclusion, Heterobasidion root-rot had little or no effect on fine root morphology, mycorrhizal colonisation and composition of fungal communities in fine roots of P. abies growing on peat soils. PMID:26861482

  6. Changes in arbuscular mycorrhizal associations and fine root traits in sites under different plant successional phases in southern Brazil.

    PubMed

    Zangaro, Waldemar; de Assis, Rafael Leandro; Rostirola, Leila Vergal; de Souza, Priscila Bochi; Gonçalves, Melissa Camargo; Andrade, Galdino; Nogueira, Marco Antonio

    2008-12-01

    Fine root morphological traits and distribution, arbuscular mycorrhizal (AM) fungi, soil fertility, and nutrient concentration in fine root tissue were compared in sites under different successional phases: grass plants, secondary forest, and mature forest in Londrina county, Paraná state, southern Brazil. Soil cores were collected randomly at the 0-10- and 10-20-cm depths in three quadrants (50 m2) in each site. Plants from the different successional stages displayed high differences in fine root distribution, fine root traits, and mycorrhizal root colonization. There were increases in the concentration of nutrients both in soil and fine roots and decrease of bulk soil density along the succession. The fine root biomass and diameter increased with the succession progress. The total fine root length, specific root length, root hair length, and root hair incidence decreased with the succession advance. Similarly, the mycorrhizal root colonization and the density of AM fungi spores in the soil decreased along the succession. Mycorrhizal root colonization and spore density were positively correlated with fine root length, specific root length, root hair length, root hair incidence, and bulk density and negatively correlated with fine root diameter and concentration of some nutrients both in soil and root tissues. Nutrient concentration in root tissue and in soil was positively correlated with fine root diameter and negatively correlated with specific root length, root hair length, and root hair incidence. These results suggest different adaptation strategies of plant roots for soil exploration and mineral acquisition among the different successional stages. Early successional stages displayed plants with fine root morphology and AM fungi colonization to improve the root functional efficiencies for uptake of nutrients and faster soil resource exploration. Late successional stages displayed plants with fine root morphology and mycorrhizal symbiosis for both a lower

  7. Global-scale latitudinal patterns of plant fine-root nitrogen and phosphorus.

    PubMed

    Yuan, Z Y; Chen, Han Y H; Reich, Peter B

    2011-01-01

    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. PMID:21673665

  8. 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.

  9. Regional scale patterns of fine root lifespan and turnover under current and future climate.

    PubMed

    McCormack, Luke M; Eissenstat, David M; Prasad, Anantha M; Smithwick, Erica A H

    2013-06-01

    Fine root dynamics control a dominant flux of carbon from plants and into soils and mediate potential uptake and cycling of nutrients and water in terrestrial ecosystems. Understanding of these patterns is needed to accurately describe critical processes like productivity and carbon storage from ecosystem to global scales. However, limited observations of root dynamics make it difficult to define and predict patterns of root dynamics across broad spatial scales. Here, we combine species-specific estimates of fine root dynamics with a model that predicts current distribution and future suitable habitat of temperate tree species across the eastern United States (US). Estimates of fine root lifespan and turnover are based on empirical observations and relationships with fine root and whole-plant traits and apply explicitly to the fine root pool that is relatively short-lived and most active in nutrient and water uptake. Results from the combined model identified patterns of faster root turnover rates in the North Central US and slower turnover rates in the Southeastern US. Portions of Minnesota, Ohio, and Pennsylvania were also predicted to experience >10% increases in root turnover rates given potential shifts in tree species composition under future climate scenarios while root turnover rates in other portions of the eastern US were predicted to decrease. Despite potential regional changes, the average estimates of root lifespan and turnover for the entire study area remained relatively stable between the current and future climate scenarios. Our combined model provides the first empirically based, spatially explicit, and spatially extensive estimates of fine root lifespan and turnover and is a potentially powerful tool allowing researchers to identify reasonable approximations of forest fine root turnover in areas where no direct observations are available. Future efforts should focus on reducing uncertainty in estimates of root dynamics by better understanding how

  10. EFFECTS OF CO2 AND TEMPERATURE ON FINE ROOT PRODUCTION AND MORTALITY IN DOUGLAS FIR

    EPA Science Inventory

    Little is known about the effects of global climate change on the production and mortality of fine roots. We conducted a 4-year study to determine the effects of elevated CO2 and temperature on Douglas fir fine ( 2 mm in diameter) roots. The study was conducted in sun-lit cont...

  11. RELATING FINE ROOT BIOMASS TO SOIL AND CLIMATE CONDITIONS IN THE PACIFIC NORTHWEST

    EPA Science Inventory

    The additive contribution of fine root biomass for Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) and western hemlock (Tsuga heterophylla (Raf.) Sarg.) to the stand average fine root biomass were estimated for eight conifer stands in the Pacific Northwest. Base...

  12. [Fine root biomass of four main vegetation types in Daluo Mountain of Ningxia, Northwest China].

    PubMed

    Su, Ji-Shuai; Cheng, Ji-Min; Gao, Yang; Qiu, Zhi-Hu; Cao, Huai-qing

    2013-03-01

    By the method of soil core sampling, this paper studied the fine root biomass, soil water content, and soil bulk density in 0-40 cm soil layer of four main vegetation types (Picea crassifolia forest, Pinus tabulaeformis forest, deciduous shrubs, and desert grassland) in Daluo Mountain of Ningxia, and the fine root biomass in the 0-40 cm soil layer of P. crassifolia forests with the ages of 50-, 70-, and 100 a. The fine root biomass of the four vegetation types was mainly distributed in 0-20 cm soil layer, with the rank of P. tabulaeformis forest > P. crassifolia forest > deciduous shrubs > desert grassland, and the fine root biomass of P. tabulaeformis forest was significantly higher than that of the other three vegetation types. The fine root biomass of the P. crassifolia forests with different ages was 70 a > 100 a > 50 a, and there were no significant differences in the live fine root biomass ratio and dead fine root biomass ratio among the three P. crassifolia forests. The soil water content in the 0-40 cm soil layer of the four vegetation types was P. crassifolia forest > P. tabulaeformis forest > deciduous shrubs > desert grassland, while the soil bulk density followed an opposite pattern, and was significantly negatively correlated with the fine root biomass.

  13. Carbon cycling in fine roots of several mature forests: results using either locally-derived or bomb-derived radiocarbon enrichment

    NASA Astrophysics Data System (ADS)

    Gaudinski, J. B.; Riley, W. J.; Torn, M. S.; Dawson, T. E.; Trumbore, S. E.; Joslin, J. D.; Majdi, H.; Hanson, P. J.; Swanston, C.

    2008-12-01

    This work seeks to improve our ability to quantify C cycling rates in fine roots of trees in mature deciduous and coniferous forests. We use two different types of atmospheric 14CO2 enrichment to trace the time elapsed since C in plant tissues was fixed from the atmosphere by photosynthesis. The first uses a local enrichment of 14CO2 which occurred in early summer 1999, at the Oak Ridge Reservation, Tennessee. The second, employed at three different sites, uses the global enrichment in background atmospheric 14CO2 caused by thermonuclear weapons testing (bomb-14C). In both cases we employ a new model (Radix1.0) to track C and 14C fluxes through fine root populations. Radix simulates two live-root populations (the longer-lived one having structural and non-structural C components), two dead-root pools, non-normally distributed root mortality turnover times, a stored C pool, seasonal growth and respiration patterns, a best-fit to measurements approach to estimate model parameters, and Monte Carlo uncertainty analysis. Our results show that: (1) New fine-root growth contains a lot of stored C (~55%) but it is young in age (0.7 y). (2) The effect of stored reserves on estimated ages of fine roots is unlikely to be large in most natural abundance isotope studies. However, models should take stored reserves into account, particularly for pulse labeling studies and fast-cycling roots (< 1 y). (3) Radiocarbon values show a stronger correlation with position on the root branch system than they do with diameter or depth in the soil profile. (4) Live fine root dynamics are well described by a short-lived and a long-lived population, with mean turnover times <1 y and ~12 y, respectively. (5) Dead root decomposition is best modeled with (at least) two pools, with moderate (~2 y) and slow (~10 y) decomposition turnover times. (6) Root respiration has a large effect on fine root biomass and isotopic composition, and should be included in ecosystem C and isotope models. (7) It is

  14. Long-term interval burning alters fine root and mycorrhizal dynamics in a ponderosa pine forest

    SciTech Connect

    Hart, Stephen C; Classen, Aimee T; Robert, Wright J.

    2005-01-01

    1. Plant roots and their mycorrhizal symbionts are critical components of forest eco- systems, being largely responsible for soil resource acquisition by plants and the main- tenance of soil structure, as well as influencing soil nutrient cycling. Silvicultural treatments should be guided by knowledge of how these below-ground components respond to different forest management practices. 2. We examined the cumulative effects of 20 years of prescribed burning at 2-year inter- vals. We measured fine root length density and fine root and mycorrhizal root biomass in the upper 15 cm of mineral soil in a south-western ponderosa pine forest over a com- plete burn cycle. 3. Repeated burning reduced fine root length, fine root biomass and mycorrhizal root biomass, as well as the amount of nitrogen and phosphorus stored in these below- ground pools. 4. Estimates of fine root production, fine root decomposition and nutrient dynamics were similar in burned and control plots. 5. Synthesis and applications . Although repeated-prescribed fire may be an effective, low-cost approach for reducing fuel loads and lessening the chance of a catastrophic wildfire in ponderosa pine forests, our results suggest that this strategy may negatively affect below-ground biomass pools and nutrient cycling processes in the long term. We recommend that mechanical reductions in fuel loads be conducted in these and similar forests that have not experienced fire for decades, before fire is reintroduced as a man- agement tool.

  15. Deficit irrigation promotes arbuscular colonization of fine roots by mycorrhizal fungi in grapevines (Vitis vinifera L.) in an arid climate.

    PubMed

    Schreiner, R Paul; Tarara, Julie M; Smithyman, Russell P

    2007-10-01

    Regulated deficit irrigation (RDI) is a common practice applied in irrigated vineyards to control canopy growth and improve fruit quality, but little is known of how imposed water deficits may alter root growth and colonization by beneficial arbuscular mycorrhizal fungi (AMF). Thus, root growth and mycorrhizal colonization were determined throughout the growing season for 3 years in own-rooted, field-grown, 'Cabernet Sauvignon' grapevines exposed to three RDI treatments. Vines under standard RDI were irrigated at 60 to 70% of full-vine evapotranspiration (FVET) from 2 weeks after fruit set until harvest, a standard commercial practice. Early deficit vines were exposed to a more extreme deficit (30% FVET) during the period from 2 weeks after fruit set until the commencement of ripening (veraison), and thereafter reverted to standard RDI. Late deficit vines were under standard RDI until veraison, then exposed to a more extreme deficit (30% FVET) between veraison and harvest. The production of fine roots was reduced in both the early and late deficit treatments, but the reduction was more consistent in the early deficit vines because the additional deficit was imposed when roots were more rapidly growing. The frequency of arbuscules in fine roots was greater in both of the additional deficit treatments than in the standard RDI, a response that appeared chronic, as the higher frequency of arbuscules was observed throughout the season despite the additional deficits being applied at discrete times. It appears that grapevines compensated for a lower density of fine roots by stimulating arbuscular colonization. Irrigation did not affect yield or quality of grapes, but reduced whole-vine photosynthesis during the additional deficit periods. It appears that high-quality grapes can be produced in this region with less water than that applied under the current RDI practice because the root system of the vine may be more efficient due to greater arbuscular colonization by AMF

  16. [Seasonal dynamics of quantitative and morphological traits of poplar fine roots and their differences between successive rotation plantations].

    PubMed

    Wang, Yan-ping; Xu, Tan; Zhu, Wan-rui; Wang, Qi-tong; Liu, Meng-ling; Wang, Hua-tian; Li, Chuan-rong; Dong, Yu-feng

    2016-02-01

    Based on the fine root samples of the first and second generations of poplar (Populus x euramericana ' Neva'), this study examined the response of quantitative and morphological traits of fine roots of different orders and the difference between generations. The results showed that, the quantitative traits of fine roots, such as root length, root surface area and root biomass, presented obvious seasonal variation, and the fine root traits had obvious difference among root orders. The quantitative traits of lower-order fine roots showed significant seasonal difference, and the fine root biomass increased in the growing season and then decreased significantly. The specific root length (SRL) of higher-order roots also showed significant change with season, while the root length density (RLD) and root tissue density (RTD) changed a little. The successive rotation resulted in the significant increase of root length, root biomass, SRL and RLD of 1-2 orders in the growing season. The quantitative traits of first order root significantly positively correlated with soil temperature and moisture, and significantly negatively correlated with the soil organic matter and soil available nitrogen content. However, the quantitative traits of second order root only showed significant correlation with soil nutrient content. The seasonal dynamics of poplar fine roots and the difference between successive rotation plantations implied carbon investment change of poplar to roots. Soil nutrient deficiency induced more carbon investment into roots, and this carbon allocation pattern might affect the aboveground productivity of poplar plantation.

  17. [Seasonal dynamics of quantitative and morphological traits of poplar fine roots and their differences between successive rotation plantations].

    PubMed

    Wang, Yan-ping; Xu, Tan; Zhu, Wan-rui; Wang, Qi-tong; Liu, Meng-ling; Wang, Hua-tian; Li, Chuan-rong; Dong, Yu-feng

    2016-02-01

    Based on the fine root samples of the first and second generations of poplar (Populus x euramericana ' Neva'), this study examined the response of quantitative and morphological traits of fine roots of different orders and the difference between generations. The results showed that, the quantitative traits of fine roots, such as root length, root surface area and root biomass, presented obvious seasonal variation, and the fine root traits had obvious difference among root orders. The quantitative traits of lower-order fine roots showed significant seasonal difference, and the fine root biomass increased in the growing season and then decreased significantly. The specific root length (SRL) of higher-order roots also showed significant change with season, while the root length density (RLD) and root tissue density (RTD) changed a little. The successive rotation resulted in the significant increase of root length, root biomass, SRL and RLD of 1-2 orders in the growing season. The quantitative traits of first order root significantly positively correlated with soil temperature and moisture, and significantly negatively correlated with the soil organic matter and soil available nitrogen content. However, the quantitative traits of second order root only showed significant correlation with soil nutrient content. The seasonal dynamics of poplar fine roots and the difference between successive rotation plantations implied carbon investment change of poplar to roots. Soil nutrient deficiency induced more carbon investment into roots, and this carbon allocation pattern might affect the aboveground productivity of poplar plantation. PMID:27396110

  18. Fine root tradeoffs between nitrogen concentration and xylem vessel traits preclude unified whole-plant resource strategies in Helianthus.

    PubMed

    Bowsher, Alan W; Mason, Chase M; Goolsby, Eric W; Donovan, Lisa A

    2016-02-01

    Recent work suggests variation in plant growth strategies is governed by a tradeoff in resource acquisition and use, ranging from a rapid resource acquisition strategy to a resource-conservative strategy. While evidence for this tradeoff has been found in leaves, knowledge of root trait strategies, and whether they reflect adaptive differentiation across environments, is limited. In the greenhouse, we investigated variation in fine root morphology (specific root length and tissue density), chemistry (nitrogen concentration and carbon:nitrogen), and anatomy (root cross-sectional traits) in populations of 26 Helianthus species and sister Phoebanthus tenuifolius. We also compared root trait variation in this study with leaf trait variation previously reported in a parallel study of these populations. Root traits varied widely and exhibited little phylogenetic signal, suggesting high evolutionary lability. Specific root length and root tissue density were weakly negatively correlated, but neither was associated with root nitrogen, providing little support for a single axis of root trait covariation. Correlations between traits measured in the greenhouse and native site characteristics were generally weak, suggesting a variety of equally viable root trait combinations exist within and across environments. However, high root nitrogen was associated with lower xylem vessel number and cross-sectional area, suggesting a tradeoff between nutrient investment and water transport capacity. This led to correlations between root and leaf traits that were not always consistent with an acquisition-conservation tradeoff at the whole-plant level. Given that roots must balance acquisition of water and nutrients with functions like anchorage, exudation, and microbial symbioses, the varied evidence for root trait covariation likely reflects the complexity of interacting selection pressures belowground. Similarly, the lack of evidence for a single acquisition-conservation tradeoff at the

  19. Stochastic roots of growth phenomena

    NASA Astrophysics Data System (ADS)

    De Lauro, E.; De Martino, S.; De Siena, S.; Giorno, V.

    2014-05-01

    We show that the Gompertz equation describes the evolution in time of the median of a geometric stochastic process. Therefore, we induce that the process itself generates the growth. This result allows us further to exploit a stochastic variational principle to take account of self-regulation of growth through feedback of relative density variations. The conceptually well defined framework so introduced shows its usefulness by suggesting a form of control of growth by exploiting external actions.

  20. Belowground Biomass Sampling to Estimate Fine Root Mass across NEON Sites

    NASA Astrophysics Data System (ADS)

    Spencer, J. J.; Meier, C. L.; Abercrombie, H.; Everhart, J. C.

    2013-12-01

    Production of belowground biomass is an important and relatively uncharacterized component of the net primary productivity (NPP) of ecosystems. Fine root productivity makes up a significant portion of total belowground production because fine roots turn over rapidly, and therefore contribute disproportionately to annual estimates of belowground net primary productivity (BNPP). One of the major goals of the National Ecological Observatory Network (NEON) is to quantify above- and below-ground NPP at 60 sites within 20 different eco-climactic regions. NEON's Terrestrial Observation System will carry out belowground biomass sampling throughout the life of the observatory to estimate fine root production. However, belowground biomass sampling during NEON operations will be constrained to a maximum depth of 50cm. This limited depth range leaves the question of what proportion of total fine root mass is being collected and how to optimally characterize belowground biomass given sampling depth limitations. During the construction period, NEON is characterizing fine root biomass distribution at depth down to 2m at each site, as well as physical and chemical properties in each soil horizon. Each sampling unit is a pit (2m deep and approximately 1.5m wide), dug in the site's dominant vegetation type where fine root biomass sampling will also occur during Operations. To sample fine root biomass in each pit, soil samples of a known volume are taken from three vertical profiles down the face of the pit. Samples are then wet sieved to extract fine root mass, and roots are dried at 65°C for 48 hours and then weighed. The soil pit data are used to estimate the proportion of total fine root biomass from each site as a function of depth. Non-linear curves are fitted to the data to calculate total fine root mass at depth and to provide estimates of the proportion of the total fine root mass that is sampled at each site during NEON's 30 year operational sampling. The belowground

  1. Viewing forests from below: fine root mass declines relative to leaf area in aging lodgepole pine stands.

    PubMed

    Schoonmaker, A S; Lieffers, V J; Landhäusser, S M

    2016-07-01

    In the continued quest to explain the decline in productivity and vigor with aging forest stands, the most poorly studied area relates to root system change in time. This paper measures the wood production, root and leaf area (and mass) in a chronosequence of fire-origin lodgepole pine (Pinus contorta Loudon) stands consisting of four age classes (12, 21, 53, and ≥100 years), each replicated ~ five times. Wood productivity was greatest in the 53-year-old stands and then declined in the ≥100-year-old stands. Growth efficiency, the quantity of wood produced per unit leaf mass, steadily declined with age. Leaf mass and fine root mass plateaued between the 53- and ≥100-year-old stands, but leaf area index actually increased in the older stands. An increase in the leaf area index:fine root area ratio supports the idea that older stand are potentially limited by soil resources. Other factors contributing to slower growth in older stands might be lower soil temperatures and increased self-shading due to the clumped nature of crowns. Collectively, the proportionally greater reduction in fine roots in older stands might be the variable that predisposes these forests to be at a potentially greater risk of stress-induced mortality. PMID:27041684

  2. CO2 enrichment increases carbon and nitrogen input from fine roots in a deciduous forest.

    PubMed

    Iversen, Colleen M; Ledford, Joanne; Norby, Richard J

    2008-01-01

    * Greater fine-root production under elevated [CO2] may increase the input of carbon (C) and nitrogen (N) to the soil profile because fine root populations turn over quickly in forested ecosystems. * Here, the effect of elevated [CO)] was assessed on root biomass and N inputs at several soil depths by combining a long-term minirhizotron dataset with continuous, root-specific measurements of root mass and [N]. The experiment was conducted in a CO(2)-enriched sweetgum (Liquidambar styraciflua) plantation. * CO2) enrichment had no effect on root tissue density or [N] within a given diameter class. Root biomass production and standing crop were doubled under elevated [CO2]. Though fine-root turnover declined under elevated [CO2], fine-root mortality was also nearly doubled under CO2 enrichment. Over 9 yr, root mortality resulted in 681 g m(-2) of extra C and 9 g m(-2) of extra N input to the soil system under elevated [CO2]. At least half of these inputs were below 30 cm soil depth. * Increased C and N input to the soil under CO2 enrichment, especially below 30 cm depth, might alter soil C storage and N mineralization. Future research should focus on quantifying root decomposition dynamics and C and N mineralization deeper in the soil.

  3. [Fine root biomass and production of four vegetation types in Loess Plateau, China].

    PubMed

    Deng, Qiang; Li, Ting; Yuan, Zhi-You; Jiao, Feng

    2014-11-01

    Fine roots (≤ 2 mm) play a major role in biogeochemical cycling in ecosystems. By the methods of soil cores and ingrowth soil cores, we studied the biomass and annual production of fine roots in 0-40 cm soil layers of four main vegetation types, i. e. , Robinia pseudoacacia plantation, deciduous shrubs, abandoned grassland, and Artemisia desertorum community in Loess Plateau, China. The spatial patterns of fine root biomass and production were negatively associated with latitudes. The fine root biomass in the 0-40 cm soil layer was in the order of deciduous shrubs (220 g · m(-2)), R. pseudoacacia plantation (163 g · m(-2)), abandoned grassland (162 g · m(-2)) and A. desertorum community (79 g · m(-2)). The proportion of ≤ 1 mm fine root biomass (74.1%) in the 0-40 cm soil layer of abandoned grassland was significantly higher than those in the other three vegetation types. The fine root biomass of the four vegetation types was mainly distributed in the 0-10 cm soil layer and decreased with soil depth. The proportion of fine root biomass (44.1%) in the 0-10 cm soil layer of abandoned grassland was significantly higher than those in other three vegetation types. The fine root productions of four vegetation types were in the order of abandoned grassland (315 g · m(-2) · a(-1)) > deciduous shrubs (249 g · m(-2) a(-1)) > R. pseudoacacia plantation (219 g · m(-2) · a(-1)) > A. desertorum community (115 g · m(-2) · a(-1)), and mainly concentrated in the 0-10 cm top soil layer and decreased with the soil depth. The proportion of the annual production (40.4%) in the 0-10 cm soil layer was the highest in abandoned grassland. Fine roots of abandoned grassland turned over faster than those from the other three vegetation types.

  4. Relations of fine-root morphology on (137)Cs uptake by fourteen Brassica species.

    PubMed

    Aung, Han Phyo; Aye, Yi Swe; Mensah, Akwasi Dwira; Omari, Richard Ansong; Djedidi, Salem; Oikawa, Yosei; Ohkama-Ohtsu, Naoko; Yokoyama, Tadashi; Bellingrath-Kimura, Sonoko Dorothea

    2015-12-01

    Fourteen Brassica species consisting of seven leafy vegetables and seven root vegetables were examined for (137)Cs uptake differences in relation to their fine-root morphological characters. A pot experiment was conducted from November 2014 to February 2015 in a Phytroton using a contaminated soil of Fukushima prefecture. Leafy vegetables showed bigger root diameters, larger root surface area and larger root volume. Consequently, leafy vegetables had higher (137)Cs uptake compared to root vegetables. Among the three fine-root parameters, only root surface area was observed as a significant contributing factor to higher (137)Cs uptake in terms of transfer factor (TF, dry weight basis). Kakina exhibited higher (137)Cs TF value (0.20) followed by Chinese cabbage (0.18) and mizuna (0.17). Lower TF values were observed in turnip (0.059), rutabaga (Kitanoshou) (0.062) and radish (Ha daikon) (0.064). PMID:26355648

  5. Relations of fine-root morphology on (137)Cs uptake by fourteen Brassica species.

    PubMed

    Aung, Han Phyo; Aye, Yi Swe; Mensah, Akwasi Dwira; Omari, Richard Ansong; Djedidi, Salem; Oikawa, Yosei; Ohkama-Ohtsu, Naoko; Yokoyama, Tadashi; Bellingrath-Kimura, Sonoko Dorothea

    2015-12-01

    Fourteen Brassica species consisting of seven leafy vegetables and seven root vegetables were examined for (137)Cs uptake differences in relation to their fine-root morphological characters. A pot experiment was conducted from November 2014 to February 2015 in a Phytroton using a contaminated soil of Fukushima prefecture. Leafy vegetables showed bigger root diameters, larger root surface area and larger root volume. Consequently, leafy vegetables had higher (137)Cs uptake compared to root vegetables. Among the three fine-root parameters, only root surface area was observed as a significant contributing factor to higher (137)Cs uptake in terms of transfer factor (TF, dry weight basis). Kakina exhibited higher (137)Cs TF value (0.20) followed by Chinese cabbage (0.18) and mizuna (0.17). Lower TF values were observed in turnip (0.059), rutabaga (Kitanoshou) (0.062) and radish (Ha daikon) (0.064).

  6. Fine-root production dominates response of a deciduous forest to atmospheric CO2 enrichment.

    PubMed

    Norby, Richard J; Ledford, Joanne; Reilly, Carolyn D; Miller, Nicole E; O'Neill, Elizabeth G

    2004-06-29

    Fine-root production and turnover are important regulators of the biogeochemical cycles of ecosystems and key components of their response to global change. We present a nearly continuous 6-year record of fine-root production and mortality from minirhizotron analysis of a closed-canopy, deciduous sweetgum forest in a free-air CO(2) enrichment experiment. Annual production of fine roots was more than doubled in plots with 550 ppm CO(2) compared with plots in ambient air. This response was the primary component of the sustained 22% increase in net primary productivity. Annual fine-root mortality matched annual production, and the mean residence time of roots was not altered by elevated CO(2), but peak fine-root standing crop in midsummer was significantly higher in CO(2)-enriched plots, especially deeper in the soil profile. The preferential allocation of additional carbon to fine roots, which have a fast turnover rate in this species, rather than to stemwood reduces the possibility of long-term enhancement by elevated CO(2) of carbon sequestration in biomass. However, sequestration of some of the fine-root carbon in soil pools is not precluded, and there may be other benefits to the tree from a seasonally larger and deeper fine-root system. Root-system dynamics can explain differences among ecosystems in their response to elevated atmospheric CO(2); hence, accurate assessments of carbon flux and storage in forests in a globally changing atmosphere must account for this unseen and difficult-to-measure component.

  7. Fine-root production dominates response of a deciduous forest to atmospheric CO2 enrichment

    PubMed Central

    Norby, Richard J.; Ledford, Joanne; Reilly, Carolyn D.; Miller, Nicole E.; O'Neill, Elizabeth G.

    2004-01-01

    Fine-root production and turnover are important regulators of the biogeochemical cycles of ecosystems and key components of their response to global change. We present a nearly continuous 6-year record of fine-root production and mortality from minirhizotron analysis of a closed-canopy, deciduous sweetgum forest in a free-air CO2 enrichment experiment. Annual production of fine roots was more than doubled in plots with 550 ppm CO2 compared with plots in ambient air. This response was the primary component of the sustained 22% increase in net primary productivity. Annual fine-root mortality matched annual production, and the mean residence time of roots was not altered by elevated CO2, but peak fine-root standing crop in midsummer was significantly higher in CO2-enriched plots, especially deeper in the soil profile. The preferential allocation of additional carbon to fine roots, which have a fast turnover rate in this species, rather than to stemwood reduces the possibility of long-term enhancement by elevated CO2 of carbon sequestration in biomass. However, sequestration of some of the fine-root carbon in soil pools is not precluded, and there may be other benefits to the tree from a seasonally larger and deeper fine-root system. Root-system dynamics can explain differences among ecosystems in their response to elevated atmospheric CO2; hence, accurate assessments of carbon flux and storage in forests in a globally changing atmosphere must account for this unseen and difficult-to-measure component. PMID:15210962

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Plant litter is a major source of soil organic carbon (C). This litter is not homogenous, but instead primarily composed of fine root and leaf litter that adapted to different physiological functions. These unique functions suggest that root and leaf litter likely have different biochemical traits, and thus different decomposition patterns. However, few studies have compared their substrate quality and contributions to soil C. Also, much less attention has been given to fine roots although they can represent a substantial litter production. Here we hypothesize that 1) leaf litter and fine roots have different substrate quality as they are highly different in biochemical composition; 2) the biochemical composition of leaf litter and fine roots responds differently to the simulated nitrogen (N) deposition. To test these hypotheses, we collected leaf litter and fine roots of Acer saccharum (the dominant species in the northern temperate ecosystems we studied) in both ambient and N addition treatment plots at four sites of Michigan N deposition gradient study. We quantified ten biochemical components thought to be important on decomposition. Strikingly, we found a consistently three-fold higher lignin concentration in fine roots than that in leaf litter (P< 0.01). On average, lignin concentration of fine roots was 45.4±0.3% while that of leaf litter was 13.5±0.2%. Lignin has been considered highly recalcitrant and hypothesized as the major precursor of humus substance. Condensed tannin (CT) concentration in fine roots (13.13±0.51%) was also substantially higher than that in leaf litter (P< 0.01, 4.63±0.42 %). Tissue CT can inhibit litter decay by both precipitating proteins and by having antimicrobial properties. In contrast, fine roots exhibited lower concentrations of non-structural carbohydrates (NSC), soluble phenolics, and holocellulose (hemicelluloses & cellulose) than leaf litter (P< 0.01). These components are considered more easily accessible, and may

  9. Long-term control of root growth

    DOEpatents

    Burton, Frederick G.; Cataldo, Dominic A.; Cline, John F.; Skiens, W. Eugene

    1992-05-26

    A method and system for long-term control of root growth without killing the plants bearing those roots involves incorporating a 2,6-dinitroaniline in a polymer and disposing the polymer in an area in which root control is desired. This results in controlled release of the substituted aniline herbicide over a period of many years. Herbicides of this class have the property of preventing root elongation without translocating into other parts of the plant. The herbicide may be encapsulated in the polymer or mixed with it. The polymer-herbicide mixture may be formed into pellets, sheets, pipe gaskets, pipes for carrying water, or various other forms. The invention may be applied to other protection of buried hazardous wastes, protection of underground pipes, prevention of root intrusion beneath slabs, the dwarfing of trees or shrubs and other applications. The preferred herbicide is 4-difluoromethyl-N,N-dipropyl-2,6-dinitro-aniline, commonly known as trifluralin.

  10. Effect of lead on root growth

    PubMed Central

    Fahr, Mouna; Laplaze, Laurent; Bendaou, Najib; Hocher, Valerie; Mzibri, Mohamed El; Bogusz, Didier; Smouni, Abdelaziz

    2013-01-01

    Lead (Pb) is one of the most widespread heavy metal contaminant in soils. It is highly toxic to living organisms. Pb has no biological function but can cause morphological, physiological, and biochemical dysfunctions in plants. Plants have developed a wide range of tolerance mechanisms that are activated in response to Pb exposure. Pb affects plants primarily through their root systems. Plant roots rapidly respond either (i) by the synthesis and deposition of callose, creating a barrier that stops Pb entering (ii) through the uptake of large amounts of Pb and its sequestration in the vacuole accompanied by changes in root growth and branching pattern or (iii) by its translocation to the aboveground parts of plant in the case of hyperaccumulators plants. Here we review the interactions of roots with the presence of Pb in the rhizosphere and the effect of Pb on the physiological and biochemical mechanisms of root development. PMID:23750165

  11. Long-term control of root growth

    SciTech Connect

    Burton, F.G.; Cataldo, D.A.; Cline, J.F.; Skiens, W.E.

    1992-05-26

    A method and system for long-term control of root growth without killing the plants bearing those roots involves incorporating a 2,6-dinitroaniline in a polymer and disposing the polymer in an area in which root control is desired. This results in controlled release of the substituted aniline herbicide over a period of many years. Herbicides of this class have the property of preventing root elongation without translocating into other parts of the plant. The herbicide may be encapsulated in the polymer or mixed with it. The polymer-herbicide mixture may be formed into pellets, sheets, pipe gaskets, pipes for carrying water, or various other forms. The invention may be applied to other protection of buried hazardous wastes, protection of underground pipes, prevention of root intrusion beneath slabs, the dwarfing of trees or shrubs and other applications. The preferred herbicide is 4-difluoromethyl-N,N-dipropyl-2,6-dinitro-aniline, commonly known as trifluralin. 7 figs.

  12. Effect of lead on root growth.

    PubMed

    Fahr, Mouna; Laplaze, Laurent; Bendaou, Najib; Hocher, Valerie; Mzibri, Mohamed El; Bogusz, Didier; Smouni, Abdelaziz

    2013-01-01

    Lead (Pb) is one of the most widespread heavy metal contaminant in soils. It is highly toxic to living organisms. Pb has no biological function but can cause morphological, physiological, and biochemical dysfunctions in plants. Plants have developed a wide range of tolerance mechanisms that are activated in response to Pb exposure. Pb affects plants primarily through their root systems. Plant roots rapidly respond either (i) by the synthesis and deposition of callose, creating a barrier that stops Pb entering (ii) through the uptake of large amounts of Pb and its sequestration in the vacuole accompanied by changes in root growth and branching pattern or (iii) by its translocation to the aboveground parts of plant in the case of hyperaccumulators plants. Here we review the interactions of roots with the presence of Pb in the rhizosphere and the effect of Pb on the physiological and biochemical mechanisms of root development.

  13. Nutrient limitation in three lowland tropical forests in southern China receiving high nitrogen deposition: insights from fine root responses to nutrient additions.

    PubMed

    Zhu, Feifei; Yoh, Muneoki; Gilliam, Frank S; Lu, Xiankai; Mo, Jiangming

    2013-01-01

    Elevated nitrogen (N) deposition to tropical forests may accelerate ecosystem phosphorus (P) limitation. This study examined responses of fine root biomass, nutrient concentrations, and acid phosphatase activity (APA) of bulk soil to five years of N and P additions in one old-growth and two younger lowland tropical forests in southern China. The old-growth forest had higher N capital than the two younger forests from long-term N accumulation. From February 2007 to July 2012, four experimental treatments were established at the following levels: Control, N-addition (150 kg N ha(-1) yr(-1)), P-addition (150 kg P ha(-1) yr(-1)) and N+P-addition (150 kg N ha(-1) yr(-1) plus 150 kg P ha(-1) yr(-1)). We hypothesized that fine root growth in the N-rich old-growth forest would be limited by P availability, and in the two younger forests would primarily respond to N additions due to large plant N demand. Results showed that five years of N addition significantly decreased live fine root biomass only in the old-growth forest (by 31%), but significantly elevated dead fine root biomass in all the three forests (by 64% to 101%), causing decreased live fine root proportion in the old-growth and the pine forests. P addition significantly increased live fine root biomass in all three forests (by 20% to 76%). The combined N and P treatment significantly increased live fine root biomass in the two younger forests but not in the old-growth forest. These results suggest that fine root growth in all three study forests appeared to be P-limited. This was further confirmed by current status of fine root N:P ratios, APA in bulk soil, and their responses to N and P treatments. Moreover, N addition significantly increased APA only in the old-growth forest, consistent with the conclusion that the old-growth forest was more P-limited than the younger forests.

  14. Root-growth-inhibiting sheet

    DOEpatents

    Burton, Frederick G.; Cataldo, Dominic A.; Cline, John F.; Skiens, W. Eugene; Van Voris, Peter

    1993-01-01

    In accordance with this invention, a porous sheet material is provided at intervals with bodies of a polymer which contain a 2,6-dinitroaniline. The sheet material is made porous to permit free passage of water. It may be either a perforated sheet or a woven or non-woven textile material. A particularly desirable embodiment is a non-woven fabric of non-biodegradable material. This type of material is known as a "geotextile" and is used for weed control, prevention of erosion on slopes, and other landscaping purposes. In order to obtain a root repelling property, a dinitroaniline is blended with a polymer which is attached to the geotextile or other porous material.

  15. Root-growth-inhibiting sheet

    DOEpatents

    Burton, F.G.; Cataldo, D.A.; Cline, J.F.; Skiens, W.E.; Van Voris, P.

    1993-01-26

    In accordance with this invention, a porous sheet material is provided at intervals with bodies of a polymer which contain a 2,6-dinitroaniline. The sheet material is made porous to permit free passage of water. It may be either a perforated sheet or a woven or non-woven textile material. A particularly desirable embodiment is a non-woven fabric of non-biodegradable material. This type of material is known as a geotextile'' and is used for weed control, prevention of erosion on slopes, and other landscaping purposes. In order to obtain a root repelling property, a dinitroaniline is blended with a polymer which is attached to the geotextile or other porous material.

  16. Fine root chemistry and decomposition in model communities of north-temperate tree species show little response to elevated atmospheric CO2 and varying soil resource availability.

    PubMed

    King, J S; Pregitzer, K S; Zak, D R; Holmes, W E; Schmidt, K

    2005-12-01

    Rising atmospheric [CO2] has the potential to alter soil carbon (C) cycling by increasing the content of recalcitrant constituents in plant litter, thereby decreasing rates of decomposition. Because fine root turnover constitutes a large fraction of annual NPP, changes in fine root decomposition are especially important. These responses will likely be affected by soil resource availability and the life history characteristics of the dominant tree species. We evaluated the effects of elevated atmospheric [CO2] and soil resource availability on the production and chemistry, mycorrhizal colonization, and decomposition of fine roots in an early- and late-successional tree species that are economically and ecologically important in north temperate forests. Open-top chambers were used to expose young trembling aspen (Populus tremuloides) and sugar maple (Acer saccharum) trees to ambient (36 Pa) and elevated (56 Pa) atmospheric CO2. Soil resource availability was composed of two treatments that bracketed the range found in the Upper Lake States, USA. After 2.5 years of growth, sugar maple had greater fine root standing crop due to relatively greater allocation to fine roots (30% of total root biomass) relative to aspen (7% total root biomass). Relative to the low soil resources treatment, aspen fine root biomass increased 76% with increased soil resource availability, but only under elevated [CO2]. Sugar maple fine root biomass increased 26% with increased soil resource availability (relative to the low soil resources treatment), and showed little response to elevated [CO2]. Concentrations of N and soluble phenolics, and C/N ratio in roots were similar for the two species, but aspen had slightly higher lignin and lower condensed tannins contents compared to sugar maple. As predicted by source-sink models of carbon allocation, pooled constituents (C/N ratio, soluble phenolics) increased in response to increased relative carbon availability (elevated [CO2]/low soil resource

  17. Fine root chemistry and decomposition in model communities of north-temperate tree species show little response to elevated atmospheric CO2 and varying soil resource availability.

    PubMed

    King, J S; Pregitzer, K S; Zak, D R; Holmes, W E; Schmidt, K

    2005-12-01

    Rising atmospheric [CO2] has the potential to alter soil carbon (C) cycling by increasing the content of recalcitrant constituents in plant litter, thereby decreasing rates of decomposition. Because fine root turnover constitutes a large fraction of annual NPP, changes in fine root decomposition are especially important. These responses will likely be affected by soil resource availability and the life history characteristics of the dominant tree species. We evaluated the effects of elevated atmospheric [CO2] and soil resource availability on the production and chemistry, mycorrhizal colonization, and decomposition of fine roots in an early- and late-successional tree species that are economically and ecologically important in north temperate forests. Open-top chambers were used to expose young trembling aspen (Populus tremuloides) and sugar maple (Acer saccharum) trees to ambient (36 Pa) and elevated (56 Pa) atmospheric CO2. Soil resource availability was composed of two treatments that bracketed the range found in the Upper Lake States, USA. After 2.5 years of growth, sugar maple had greater fine root standing crop due to relatively greater allocation to fine roots (30% of total root biomass) relative to aspen (7% total root biomass). Relative to the low soil resources treatment, aspen fine root biomass increased 76% with increased soil resource availability, but only under elevated [CO2]. Sugar maple fine root biomass increased 26% with increased soil resource availability (relative to the low soil resources treatment), and showed little response to elevated [CO2]. Concentrations of N and soluble phenolics, and C/N ratio in roots were similar for the two species, but aspen had slightly higher lignin and lower condensed tannins contents compared to sugar maple. As predicted by source-sink models of carbon allocation, pooled constituents (C/N ratio, soluble phenolics) increased in response to increased relative carbon availability (elevated [CO2]/low soil resource

  18. DNA analysis of soil extracts can be used to investigate fine root depth distribution of trees.

    PubMed

    Bithell, Sean L; Tran-Nguyen, Lucy T T; Hearnden, Mark N; Hartley, Diana M

    2014-01-01

    Understanding the root distribution of trees by soil coring is time -: consuming as it requires the separation of roots from soil and classification of roots into particular size classes. This labour-intensive process can limit sample throughput and therefore sampling intensity. We investigated the use of quantitative polymerase chain reaction (qPCR) on soil DNA extractions to determine live fine root DNA density (RDD, mg DNA m(-2)) for mango (Mangifera indica) trees. The specificity of the qPCR was tested against DNA extracted from 10 mango cultivars and 14 weed species. All mango cultivars and no weeds were detected. Mango DNA was successfully quantified from control soil spiked with mango roots and weed species. The DNA yield of mango root sections stored in moist soil at 23-28 °C declined after 15 days to low concentrations as roots decayed, indicating that dead root materials in moist soil would not cause false-positive results. To separate large roots from samples, a root separation method for field samples was used to target the root fragments remaining in sieved (minimum 2 mm aperture) soil for RDD comparisons. Using this method we compared the seasonal RDD values of fine roots for five mango rootstock cultivars in a field trial. The mean cultivar DNA yields by depth from root fragments in the sieved soil samples had the strongest relationship (adjusted multiple R(2) = 0.9307, P < 0.001) with the dry matter (g m(-2)) of fine (diameter <0.64 mm) roots removed from the soil by sieving. This method provides a species-specific and rapid means of comparing the distribution and concentration of live fine roots of trees in orchards using soil samples up to 500 g.

  19. DNA analysis of soil extracts can be used to investigate fine root depth distribution of trees

    PubMed Central

    Bithell, Sean L.; Tran-Nguyen, Lucy T. T.; Hearnden, Mark N.; Hartley, Diana M.

    2015-01-01

    Understanding the root distribution of trees by soil coring is time-consuming as it requires the separation of roots from soil and classification of roots into particular size classes. This labour-intensive process can limit sample throughput and therefore sampling intensity. We investigated the use of quantitative polymerase chain reaction (qPCR) on soil DNA extractions to determine live fine root DNA density (RDD, mg DNA m−2) for mango (Mangifera indica) trees. The specificity of the qPCR was tested against DNA extracted from 10 mango cultivars and 14 weed species. All mango cultivars and no weeds were detected. Mango DNA was successfully quantified from control soil spiked with mango roots and weed species. The DNA yield of mango root sections stored in moist soil at 23–28 °C declined after 15 days to low concentrations as roots decayed, indicating that dead root materials in moist soil would not cause false-positive results. To separate large roots from samples, a root separation method for field samples was used to target the root fragments remaining in sieved (minimum 2 mm aperture) soil for RDD comparisons. Using this method we compared the seasonal RDD values of fine roots for five mango rootstock cultivars in a field trial. The mean cultivar DNA yields by depth from root fragments in the sieved soil samples had the strongest relationship (adjusted multiple R2 = 0.9307, P < 0.001) with the dry matter (g m−2) of fine (diameter <0.64 mm) roots removed from the soil by sieving. This method provides a species-specific and rapid means of comparing the distribution and concentration of live fine roots of trees in orchards using soil samples up to 500 g. PMID:25552675

  20. Effects of elevated concentrations of atmospheric CO2 and tropospheric O3 on decomposition of fine roots.

    PubMed

    Chapman, Jack A; King, John S; Pregitzer, Kurt S; Zak, Donald R

    2005-12-01

    Rising atmospheric carbon dioxide (CO2) concentration ([CO2]) could alter terrestrial carbon (C) cycling by affecting plant growth, litter chemistry and decomposition. How the concurrent increase in tropospheric ozone (O3) concentration ([O3]) will interact with rising atmospheric [CO2] to affect C cycling is unknown. A major component of carbon cycling in forests is fine root production, mortality and decomposition. To better understand the effects of elevated [CO2] and [O3] on the dynamics of fine root C, we conducted a combined field and laboratory incubation experiment to monitor decomposition dynamics and changes in fine root litter chemistry. Free-air CO2 enrichment (FACE) technology at the FACTS-II Aspen FACE project in Rhinelander, Wisconsin, elevated [CO2] (535 microl 1-1) and [O3] (53 nl 1-1) in intact stands of pure trembling aspen (Populus tremuloides Michx.) and in mixed stands of trembling aspen plus paper birch (Betula papyrifera Marsh.) and trembling aspen plus sugar maple (Acer saccharum Marsh.). We hypothesized that the trees would react to increased C availability (elevated [CO2]) by increasing allocation to C-based secondary compounds (CBSCs), thereby decreasing rates of decomposition. Because of its lower growth potential, we reasoned this effect would be greatest in the aspen-maple community relative to the aspen and aspen-birch communities. As a result of decreased C availability, we expected elevated [O3] to counteract shifts in C allocation induced by elevated [CO2]. Concentrations of CBSCs were rarely significantly affected by the CO2 and O3 treatments in decomposing fine roots. Rates of microbial respiration and mass loss from fine roots were unaffected by the treatments, although the production of dissolved organic C differed among communities. We conclude that elevated [CO2] and [O3] induce only small changes in fine root chemistry that are insufficient to significantly influence fine root decomposition. If changes in soil C cycling

  1. Effects of elevated concentrations of atmospheric CO2 and tropospheric O3 on decomposition of fine roots.

    PubMed

    Chapman, Jack A; King, John S; Pregitzer, Kurt S; Zak, Donald R

    2005-12-01

    Rising atmospheric carbon dioxide (CO2) concentration ([CO2]) could alter terrestrial carbon (C) cycling by affecting plant growth, litter chemistry and decomposition. How the concurrent increase in tropospheric ozone (O3) concentration ([O3]) will interact with rising atmospheric [CO2] to affect C cycling is unknown. A major component of carbon cycling in forests is fine root production, mortality and decomposition. To better understand the effects of elevated [CO2] and [O3] on the dynamics of fine root C, we conducted a combined field and laboratory incubation experiment to monitor decomposition dynamics and changes in fine root litter chemistry. Free-air CO2 enrichment (FACE) technology at the FACTS-II Aspen FACE project in Rhinelander, Wisconsin, elevated [CO2] (535 microl 1-1) and [O3] (53 nl 1-1) in intact stands of pure trembling aspen (Populus tremuloides Michx.) and in mixed stands of trembling aspen plus paper birch (Betula papyrifera Marsh.) and trembling aspen plus sugar maple (Acer saccharum Marsh.). We hypothesized that the trees would react to increased C availability (elevated [CO2]) by increasing allocation to C-based secondary compounds (CBSCs), thereby decreasing rates of decomposition. Because of its lower growth potential, we reasoned this effect would be greatest in the aspen-maple community relative to the aspen and aspen-birch communities. As a result of decreased C availability, we expected elevated [O3] to counteract shifts in C allocation induced by elevated [CO2]. Concentrations of CBSCs were rarely significantly affected by the CO2 and O3 treatments in decomposing fine roots. Rates of microbial respiration and mass loss from fine roots were unaffected by the treatments, although the production of dissolved organic C differed among communities. We conclude that elevated [CO2] and [O3] induce only small changes in fine root chemistry that are insufficient to significantly influence fine root decomposition. If changes in soil C cycling

  2. Evidence of old carbon used to grow new fine roots in a tropical forest.

    PubMed

    Vargas, Rodrigo; Trumbore, Susan E; Allen, Michael F

    2009-01-01

    In this study, we explore how a hurricane disturbance influenced carbon allocation for the production of new fine roots. Before and after a hurricane, we measured the age of carbon (time since fixation from the atmosphere) in fine root structural tissues using natural abundance radiocarbon (14C) measured by accelerator mass spectrometry. Roots were sampled from five seasonally dry tropical forests ranging in age from 6 yr to a mature forest. Structural carbon in combined live + dead roots picked from soil cores sampled 1 month before the hurricane had mean ages ranging from 4 to 11 yr, whereas live roots alone had ages of 1-2 yr. Structural carbon in new live fine roots produced over a period lasting from 3 wk before the hurricane to 2 months after the event had mean ages of between 2 and 10 yr. Contrary to expectations, our results showed that plants allocate long-lived storage carbon pools to the production of new fine roots after canopy defoliation and root mortality. The age of the carbon allocated for new roots increased with forest age and forest above-ground biomass, suggesting an adaptation of plants to survive and recover from severe disturbances.

  3. Quest for Continual Growth Takes Root

    ERIC Educational Resources Information Center

    Surdey, Mary M.; Hashey, Jane M.

    2006-01-01

    In this article, the authors describe how the quest for continual growth has taken its root at Vestal Central School district. Located at the heart of upstate New York, educators at Vestal Central School district have created a spirit of "kaizen," a Japanese word meaning the relentless quest for continual improvement and higher-quality…

  4. The continuous incorporation of carbon into existing Sassafras albidum fine roots and its implications for estimating root turnover.

    PubMed

    Adams, Thomas S; Eissenstat, David M

    2014-01-01

    Although understanding the timing of the deposition of recent photosynthate into fine roots is critical for determining root lifespan and turnover using isotopic techniques, few studies have directly examined the deposition and subsequent age of root carbon. To gain a better understanding of the timing of the deposition of root carbon, we labeled four individual Sassafras albidum trees with 99% 13C CO2. We then tracked whether the label appeared in roots that were at least two weeks old and no longer elongating, at the time of labeling. We found that not only were the non-structural carbon pools (soluble sugars and starch) of existing first-order tree roots incorporating carbon from current photosynthate, but so were the structural components of the roots, even in roots that were more than one year old at the time of labeling.Our findings imply that carbon used in root structural and nonstructural pools is not derived solely from photosynthate at root initiation and have implications regarding the determination of root age and turnover using isotopic techniques.

  5. The Continuous Incorporation of Carbon into Existing Sassafras albidum Fine Roots and Its Implications for Estimating Root Turnover

    PubMed Central

    Adams, Thomas S.; Eissenstat, David M.

    2014-01-01

    Although understanding the timing of the deposition of recent photosynthate into fine roots is critical for determining root lifespan and turnover using isotopic techniques, few studies have directly examined the deposition and subsequent age of root carbon. To gain a better understanding of the timing of the deposition of root carbon, we labeled four individual Sassafras albidum trees with 99% 13C CO2. We then tracked whether the label appeared in roots that were at least two weeks old and no longer elongating, at the time of labeling. We found that not only were the non-structural carbon pools (soluble sugars and starch) of existing first-order tree roots incorporating carbon from current photosynthate, but so were the structural components of the roots, even in roots that were more than one year old at the time of labeling.Our findings imply that carbon used in root structural and nonstructural pools is not derived solely from photosynthate at root initiation and have implications regarding the determination of root age and turnover using isotopic techniques. PMID:24788762

  6. SEASONAL PATTERNS OF FINE ROOT PRODUCTION AND TURNOVER IN PONDEROSA PINE STANDS OF DIFFERENT AGES

    EPA Science Inventory

    Root minirhizotron tubes were installed in two ponderosa pine (Pinus ponderosa Laws.) stands around three different tree age classes (16, 45, and > 250 yr old) to examine root spatial distribution in relation to canopy size and tree distribution, and to determine if rates of fine...

  7. Organic matter and nutrients associated with fine root turnover in a white oak stand. [Quercus albus

    SciTech Connect

    Joslin, J.D.; Henderson, G.S.

    1987-06-01

    Organic matter and nutrients cycled by fine root turnover were quantified in a mature white oak (Quercus alba L.) stand and compared to contributions from litterfall. The budget method, a revised version of the traditional repeated sampling method, was used to measure root turnover. The magnitude of the live and dead pools of three size classes of fine (<5 mm diameter) roots were monitored bimonthly for 14 months. Decomposition rates over these intervals were also measured, while production and mortality were calculated. Litterfall was collected simultaneously, and the nutrient concentrations of the various detritus components determined. Root pools fluctuated less, and total root turnover biomass (220 g m/sup -2/ yr/sup -1/) was also less than previously noted in most other stands studied. Fine root turnover accounted for 30% of the total detritus production and 20-40% of the turnover of the five macronutrients (N, P, K, Ca, Mg) studied. Differences with previous studies suggest that there may be rather large species and/or site-related differences in the amount of energy various stands allocate for fine root maintenance. For. Sci. 33(2):330-346.

  8. Do increased summer precipitation and N deposition alter fine root dynamics in a Mojave Desert ecosystem?

    PubMed

    Verburg, Paul S J; Young, Andrew C; Stevenson, Bryan A; Glanzmann, Isabelle; Arnone, John A; Marion, Giles M; Holmes, Christopher; Nowak, Robert S

    2013-03-01

    Climate change is expected to impact the amount and distribution of precipitation in the arid southwestern United States. In addition, nitrogen (N) deposition is increasing in these regions due to increased urbanization. Responses of belowground plant activity to increases in soil water content and N have shown inconsistent patterns between biomes. In arid lands, plant productivity is limited by water and N availability so it is expected that changes in these factors will affect fine root dynamics. The objectives of this study were to quantify the effects of increased summer precipitation and N deposition on fine root dynamics in a Mojave Desert ecosystem during a 2-year field experiment using minirhizotron measurements. Root length density, production, and mortality were measured in field plots in the Mojave Desert receiving three 25 mm summer rain events and/or 40 kg N ha(-1)  yr(-1) . Increased summer precipitation and N additions did not have an overall significant effect on any of the measured root parameters. However, differences in winter precipitation resulting from interannual variability in rainfall appeared to affect root parameters with root production and turnover increasing following a wet winter most likely due to stimulation of annual grasses. In addition, roots were distributed more deeply in the soil following the wet winter. Root length density was initially higher under canopies compared to canopy interspaces, but converged toward the end of the study. In addition, roots tended to be distributed more deeply into the soil in canopy interspace areas. Results from this study indicated that increased summer precipitation and N deposition in response to climate change and urbanization are not likely to affect fine root dynamics in these Mojave Desert ecosystems, despite studies showing aboveground plant physiological responses to these environmental perturbations. However, changes in the amount and possibly distribution of winter precipitation

  9. Dynamics of root growth in microgravity.

    PubMed

    Johnsson, A; Karlsson, C; Chapman, D K; Braseth, J D; Iversen, T H

    1996-06-27

    An experiment to study the growth of garden cress roots in microgravity is described. The experiment, denoted RANDOM, was an ESA Biorack experiment in the IML-2 flight in July 1994. In the absence of gravity, it can be anticipated that the roots would show random growth, changing their direction randomly. The hypothesis that such random growth movements occur according to random walk theory, leads to predictions as to the detailed manner in which deviations increase with time. The experiment was designed to test this random walk hypothesis. The paper concentrates on the technological aspects of studying the roots in microgravity. The development of suitable plant chambers, fitting containers developed by ESA, is described as well as the techniques used to grow the seeds between agar slices. hardware was developed to record photographically root movements between the agar slices. Photos were taken once per hour. Some plant chambers were designed to allow fixation of plant material in space. The practical solutions found using glutaraldehyde for prefixation in the Spacelab, within the restrictions given, are described. The experimental results show that the growth pattern in fact followed the prediction from the random walk approach. The average changes in the growth direction stayed constant and equal to zero during the experiment while the squared angular deviations increased proportional to time. Furthermore, plant material prefixed in orbit was permanently fixed after the flight. Light microscopy and electron microscopy pictures are shown as examples of the results achieved. The long prefixation period meant a drawback for the quality of the fixation process. However, sections suitable for study were achieved. The main goals of the RANDOM experiment were therefore achieved.

  10. Endosomal Interactions during Root Hair Growth

    PubMed Central

    von Wangenheim, Daniel; Rosero, Amparo; Komis, George; Šamajová, Olga; Ovečka, Miroslav; Voigt, Boris; Šamaj, Jozef

    2016-01-01

    The dynamic localization of endosomal compartments labeled with targeted fluorescent protein tags is routinely followed by time lapse fluorescence microscopy approaches and single particle tracking algorithms. In this way trajectories of individual endosomes can be mapped and linked to physiological processes as cell growth. However, other aspects of dynamic behavior including endosomal interactions are difficult to follow in this manner. Therefore, we characterized the localization and dynamic properties of early and late endosomes throughout the entire course of root hair formation by means of spinning disc time lapse imaging and post-acquisition automated multitracking and quantitative analysis. Our results show differential motile behavior of early and late endosomes and interactions of late endosomes that may be specified to particular root hair domains. Detailed data analysis revealed a particular transient interaction between late endosomes—termed herein as dancing-endosomes—which is not concluding to vesicular fusion. Endosomes preferentially located in the root hair tip interacted as dancing-endosomes and traveled short distances during this interaction. Finally, sizes of early and late endosomes were addressed by means of super-resolution structured illumination microscopy (SIM) to corroborate measurements on the spinning disc. This is a first study providing quantitative microscopic data on dynamic spatio-temporal interactions of endosomes during root hair tip growth. PMID:26858728

  11. Massive turnover rates of fine root detrital carbon in tropical Australian mangroves.

    PubMed

    Robertson, Alistar I; Alongi, Daniel M

    2016-03-01

    Dead fine roots are the major component of organic carbon (C) stored in mangrove forests. We measured the mass and decomposition of fine root detritus in three mangrove forests along an intertidal gradient in tropical Australia to provide the first integrated estimates of the rate of turnover of fine root detritus. The grand mean dry masses of dead fine roots in the forests decreased in the order mid-intertidal Rhizophora (mean 28.4 kg m(-2)), low-intertidal Rhizophora (16.3 kg m(-2)) and high-intertidal Ceriops (mean 8.9 kg m(-2)), and were some of the highest on record. The first-order decay coefficients (day(-1)) for dead fine roots in the low Rhizophora, mid Rhizophora and high Ceriops forest sites were 0.0014, 0.0017 and 0.0007, respectively, and were the lowest on record. The estimated mean fluxes of C via decomposition of dead fine roots were very high in all forests, decreasing in the order mid Rhizophora (18.8 g C m(-2) day(-1)), low Rhizophora (8.4 g C m(-2) day(-1)) and high Ceriops (2.5 g C m(-2) day(-1)). There were relatively low levels of uncertainty in these estimates when all sources of error were considered. The fluxes of C for the two Rhizophora sites integrate all losses from saprophytic decay and leaching of dissolved C and were 50-200 % higher than the estimated total annual loss of C derived by summing rates of bacterial metabolism and export via groundwater and surface waters in these forests. The significant difference reflects both the very high dead root masses and the incorporation of the impact of fungi in our estimates. PMID:26581419

  12. Massive turnover rates of fine root detrital carbon in tropical Australian mangroves.

    PubMed

    Robertson, Alistar I; Alongi, Daniel M

    2016-03-01

    Dead fine roots are the major component of organic carbon (C) stored in mangrove forests. We measured the mass and decomposition of fine root detritus in three mangrove forests along an intertidal gradient in tropical Australia to provide the first integrated estimates of the rate of turnover of fine root detritus. The grand mean dry masses of dead fine roots in the forests decreased in the order mid-intertidal Rhizophora (mean 28.4 kg m(-2)), low-intertidal Rhizophora (16.3 kg m(-2)) and high-intertidal Ceriops (mean 8.9 kg m(-2)), and were some of the highest on record. The first-order decay coefficients (day(-1)) for dead fine roots in the low Rhizophora, mid Rhizophora and high Ceriops forest sites were 0.0014, 0.0017 and 0.0007, respectively, and were the lowest on record. The estimated mean fluxes of C via decomposition of dead fine roots were very high in all forests, decreasing in the order mid Rhizophora (18.8 g C m(-2) day(-1)), low Rhizophora (8.4 g C m(-2) day(-1)) and high Ceriops (2.5 g C m(-2) day(-1)). There were relatively low levels of uncertainty in these estimates when all sources of error were considered. The fluxes of C for the two Rhizophora sites integrate all losses from saprophytic decay and leaching of dissolved C and were 50-200 % higher than the estimated total annual loss of C derived by summing rates of bacterial metabolism and export via groundwater and surface waters in these forests. The significant difference reflects both the very high dead root masses and the incorporation of the impact of fungi in our estimates.

  13. [Fine root biomass and carbon storage in surface soil of Cinnamomum camphora plantation in rainy area of West China].

    PubMed

    Wei, Peng; Li, Xian-Wei; Fan, Chuan; Zhang, Teng-Fei; Liu, Yun-Ke; Su, Yu; Yang, Zheng-Ju

    2013-10-01

    Fine root in forest ecosystems plays an important role in global C cycle. In this study, a measurement was made on the fine root biomass and carbon storage in the surface soil (0-30 cm) of a 31 year-old Cinnamomum camphora plantation in the Rainy Area of West China in November, 2010-December, 2011. The total biomass and carbon storage of the fine roots (living and dead) in the surface soil were 1592.29 kg x hm(-2) and 660.68 kg C x hm(-2), in which, living fine roots accounted for 91.1% and 91.8% respectively. The total biomass and carbon storage of the first five order living roots and dead roots decreased significantly with increasing soil depth, and the living root biomass and carbon storage increased significantly with root order. The sum of the biomass and carbon storage of living and dead fine roots was the largest in autumn and the smallest in winter, but the biomass and carbon storage of the dead fine roots were the largest in winter and the smallest in summer. The biomass and carbon storage of the first two order roots were the largest in summer and the smallest in winter, while those of the last three order roots were the largest in autumn and the smallest in winter. The spatial heterogeneity of soil moisture and nutrients was the main factor affecting the fine root biomass and carbon storage.

  14. Roots Revealed - Neutron imaging insight of spatial distribution, morphology, growth and function

    NASA Astrophysics Data System (ADS)

    Warren, J.; Bilheux, H.; Kang, M.; Voisin, S.; Cheng, C.; Horita, J.; Perfect, E.

    2013-05-01

    Root production, distribution and turnover are not easily measured, yet their dynamics are an essential part of understanding and modeling ecosystem response to changing environmental conditions. Root age, order, morphology and mycorrhizal associations all regulate root uptake of water and nutrients, which along with along with root distribution determines plant response to, and impact on its local environment. Our objectives were to demonstrate the ability to non-invasively monitor fine root distribution, root growth and root functionality in Zea mays L. (maize) and Panicum virgatum L. (switchgrass) seedlings using neutron imaging. Plants were propagated in aluminum chambers containing sand then placed into a high flux cold neutron beam line. Dynamics of root distribution and growth were assessed by collecting consecutive CCD radiographs through time. Root functionality was assessed by tracking individual root uptake of water (H2O) or deuterium oxide (D2O) through time. Since neutrons strongly scatter H atoms, but not D atoms, biological materials such as plants are prime candidates for neutron imaging. 2D and 3D neutron radiography readily illuminated root structure, root growth, and relative plant and soil water content. Fungal hyphae associated with the roots were also visible and appeared as dark masses since their diameter was likely several orders of magnitude less than ~100 μm resolution of the detector. The 2D pulse-chase irrigation experiments with H2O and D2O successfully allowed observation of uptake and mass flow of water within the root system. Water flux within individual roots responded differentially to foliar illumination based on internal water potential gradients, illustrating the ability to track root functionality based on root size, order and distribution within the soil. (L) neutron image of switchgrass growing in sandy soil with 100 μm diameter roots (R) 3D reconstruction of maize seedling following neutron tomography

  15. 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.

  16. Hydraulic properties and fine root mass of Larix sibirica along forest edge-interior gradients

    NASA Astrophysics Data System (ADS)

    Chenlemuge, Tselmeg; Dulamsuren, Choimaa; Hertel, Dietrich; Schuldt, Bernhard; Leuschner, Christoph; Hauck, Markus

    2015-02-01

    At its southernmost distribution limit in Inner Asia, the boreal forest disintegrates into forest fragments on moist sites (e.g. north-facing slopes), which are embedded in grasslands. This landscape mosaic is characterized by a much higher forest edge-to-interior ratio than in closed boreal forests. Earlier work in the forest-steppe ecotone of Mongolia has shown that Larix sibirica trees at forest edges grow faster than in the forest interior, as the more xeric environment at the edge promotes self-thinning and edges are preferentially targeted by selective logging and livestock grazing. Lowered stand density reduces competition for water in these semi-arid forests, where productivity is usually limited by summer drought. We studied how branch and coarse root hydraulic architecture and xylem conductivity, fine root biomass and necromass, and fine root morphology of L. sibirica respond to sites differing in water availability. Studying forest edge-interior gradients in two regions of western Mongolia, we found a significant reduction of branch theoretical (Kp) and empirical conductivity (Ks) in the putatively more drought-affected forest interior in the Mongolian Altai (mean precipitation: 120 mm yr-1), while no branch xylem modification occurred in the moister Khangai Mountains (215 mm yr-1). Kp and Ks were several times larger in roots than in branches, but root hydraulics were not influenced by stand density or mean annual precipitation. Very low fine root biomass: necromass ratios at all sites, and in the forest interior in particular, suggest that L. sibirica seeks to maintain a relatively high root conductivity by producing large conduits, which results in high root mortality due to embolism during drought. Our results suggest that L. sibirica is adapted to the semi-arid climate at its southernmost distribution limit by considerable plasticity of the branch hydraulic system and a small but apparently dynamic fine root system.

  17. 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.

  18. Hormone symphony during root growth and development.

    PubMed

    Garay-Arroyo, Adriana; De La Paz Sánchez, María; García-Ponce, Berenice; Azpeitia, Eugenio; Alvarez-Buylla, Elena R

    2012-12-01

    Hormones regulate plant growth and development in response to external environmental stimuli via complex signal transduction pathways, which in turn form complex networks of interaction. Several classes of hormones have been reported, and their activity depends on their biosynthesis, transport, conjugation, accumulation in the vacuole, and degradation. However, the activity of a given hormone is also dependent on its interaction with other hormones. Indeed, there is a complex crosstalk between hormones that regulates their biosynthesis, transport, and/or signaling functionality, although some hormones have overlapping or opposite functions. The plant root is a particularly useful system in which to study the complex role of plant hormones in the plastic control of plant development. Physiological, cellular, and molecular genetic approaches have been used to study the role of plant hormones in root meristem homeostasis. In this review, we discuss recent findings on the synthesis, signaling, transport of hormones and role during root development and examine the role of hormone crosstalk in maintaining homeostasis in the apical root meristem.

  19. Effect of nitrogen fertilizer, root branch order and temperature on respiration and tissue N concentration of fine roots in Larix gmelinii and Fraxinus mandshurica.

    PubMed

    Jia, Shuxia; Wang, Zhengquan; Li, Xingpeng; Zhang, Xiaoping; McLaughlin, Neil B

    2011-07-01

    Root respiration is closely related to root morphology, yet it is unclear precisely how to distinguish respiration-related root physiological functions within the branching fine root system. Root respiration and tissue N concentration were examined for different N fertilization treatments, sampling dates, branch orders and temperatures of larch (Larix gmelinii L.) and ash (Fraxinus mandshurica L.) using the excised roots method. The results showed that N fertilization enhanced both root respiration and tissue N concentration for all five branch orders. The greatest increases in average root respiration for N fertilization treatment were 13.30% in larch and 18.25% in ash at 6°C. However, N fertilization did not change the seasonal dynamics of root respiration. Both root respiration and root tissue N concentration decreased with increase in root branch order. First-order (finest) roots exhibited the highest respiration rates and tissue N concentrations out of the five root branch orders examined. There was a highly significant linear relationship between fine root N concentration and root respiration rate. Root N concentration explained >60% of the variation in respiration rate at any given combination of root order and temperature. Root respiration showed a classical exponential relationship with temperature, with the Q(10) for root respiration in roots of different branching orders ranging from 1.62 to 2.20. The variation in root respiration by order illustrates that first-order roots are more metabolically active, suggesting that roots at different branch order positions have different physiological functions. The highly significant relationship between root respiration at different branch orders and root tissue N concentration suggests that root tissue N concentration may be used as a surrogate for root respiration, simplifying future research into the C dynamics of rooting systems. PMID:21849591

  20. Fine root dynamics and forest production across a calcium gradient in northern hardwood and conifer ecosystems

    USGS Publications Warehouse

    Park, B.B.; Yanai, R.D.; Fahey, T.J.; Bailey, S.W.; Siccama, T.G.; Shanley, J.B.; Cleavitt, N.L.

    2008-01-01

    Losses of soil base cations due to acid rain have been implicated in declines of red spruce and sugar maple in the northeastern USA. We studied fine root and aboveground biomass and production in five northern hardwood and three conifer stands differing in soil Ca status at Sleepers River, VT; Hubbard Brook, NH; and Cone Pond, NH. Neither aboveground biomass and production nor belowground biomass were related to soil Ca or Ca:Al ratios across this gradient. Hardwood stands had 37% higher aboveground biomass (P = 0.03) and 44% higher leaf litter production (P < 0.01) than the conifer stands, on average. Fine root biomass (<2 mm in diameter) in the upper 35 cm of the soil, including the forest floor, was very similar in hardwoods and conifers (5.92 and 5.93 Mg ha-1). The turnover coefficient (TC) of fine roots smaller than 1 mm ranged from 0.62 to 1.86 y-1 and increased significantly with soil exchangeable Ca (P = 0.03). As a result, calculated fine root production was clearly higher in sites with higher soil Ca (P = 0.02). Fine root production (biomass times turnover) ranged from 1.2 to 3.7 Mg ha-1 y-1 for hardwood stands and from 0.9 to 2.3 Mg ha-1 y -1 for conifer stands. The relationship we observed between soil Ca availability and root production suggests that cation depletion might lead to reduced carbon allocation to roots in these ecosystems. ?? 2008 Springer Science+Business Media, LLC.

  1. FINE ROOT TURNOVER IN PONDEROSA PINE STANDS OF DIFFERENT AGES: FIRST-YEAR RESULTS

    EPA Science Inventory

    Root minirhizotron tubs were installed in two ponderosa pine (Pinus ponderosa Laws.) Stands of different ages to examine patterns of root growth and death. The old-growth site (OS) consists of a mixture of old (>250 years) and young trees (ca.45 yrs)< and is located near clamp S...

  2. Digging deeper: Fine root responses to rising atmospheric [CO2] in forested ecosystems

    SciTech Connect

    Iversen, Colleen M

    2010-01-01

    Experimental evidence from a diverse set of forested ecosystems indicates that CO2 enrichment may lead to deeper rooting distributions. While the causes of greater root production at deeper soil depths under elevated CO2 concentration ([CO2]) require further investigation, altered rooting distributions are expected to affect important ecosystem processes. The depth at which fine roots are produced may influence root chemistry, physiological function, and mycorrhizal infection, leading to altered nitrogen (N) uptake rates and slower turnover. Also, soil processes such as microbial decomposition are slowed at depth in the soil, potentially affecting the rate at which root detritus becomes incorporated into soil organic matter. Deeper rooting distributions under elevated [CO2] provide exciting opportunities to use novel sensors and chemical analyses throughout the soil profile to track the effects of root proliferation on carbon (C) and N cycling. Models do not currently incorporate information on root turnover and C and N cycling at depth in the soil, and modification is necessary to accurately represent processes associated with altered rooting depth distributions. Progress in understanding and modeling the interface between deeper rooting distributions under elevated [CO2] and soil C and N cycling will be critical in projecting the sustainability of forest responses to rising atmospheric [CO2].

  3. [Effects of tree species diversity on fine-root biomass and morphological characteristics in subtropical Castanopsis carlesii forests].

    PubMed

    Wang, Wei-Wei; Huang, Jin-Xue; Chen, Feng; Xiong, De-Cheng; Lu, Zheng-Li; Huang, Chao-Chao; Yang, Zhi-Jie; Chen, Guang-Shui

    2014-02-01

    Fine roots in the Castanopsis carlesii plantation forest (MZ), the secondary forest of C. carlesii through natural regeneration with anthropogenic promotion (AR), and the secondary forest of C. carlesii through natural regeneration (NR) in Sanming City, Fujian Province, were estimated by soil core method to determine the influence of tree species diversity on biomass, vertical distribution and morphological characteristics of fine roots. The results showed that fine root biomass for the 0-80 cm soil layer in the MZ, AR and NR were (182.46 +/- 10.81), (242.73 +/- 17.85) and (353.11 +/- 16.46) g x m(-2), respectively, showing an increased tendency with increasing tree species diversity. In the three forests, fine root biomass was significantly influenced by soil depth, and fine roots at the 0-10 cm soil layer accounted for more than 35% of the total fine root biomass. However, the interaction of stand type and soil depth on fine-root distribution was not significant, indicating no influence of tree species diversity on spatial niche segregation in fine roots. Root surface area density and root length density were the highest in NR and lowest in the MZ. Specific root length was in the order of AR > MZ > NR, while specific root surface area was in the order of NR > MZ > AR. There was no significant interaction of stand type and soil depth on specific root length and specific root surface area. Fine root morphological plasticity at the stand level had no significant response to tree species diversity. PMID:24830228

  4. [Effects of tree species diversity on fine-root biomass and morphological characteristics in subtropical Castanopsis carlesii forests].

    PubMed

    Wang, Wei-Wei; Huang, Jin-Xue; Chen, Feng; Xiong, De-Cheng; Lu, Zheng-Li; Huang, Chao-Chao; Yang, Zhi-Jie; Chen, Guang-Shui

    2014-02-01

    Fine roots in the Castanopsis carlesii plantation forest (MZ), the secondary forest of C. carlesii through natural regeneration with anthropogenic promotion (AR), and the secondary forest of C. carlesii through natural regeneration (NR) in Sanming City, Fujian Province, were estimated by soil core method to determine the influence of tree species diversity on biomass, vertical distribution and morphological characteristics of fine roots. The results showed that fine root biomass for the 0-80 cm soil layer in the MZ, AR and NR were (182.46 +/- 10.81), (242.73 +/- 17.85) and (353.11 +/- 16.46) g x m(-2), respectively, showing an increased tendency with increasing tree species diversity. In the three forests, fine root biomass was significantly influenced by soil depth, and fine roots at the 0-10 cm soil layer accounted for more than 35% of the total fine root biomass. However, the interaction of stand type and soil depth on fine-root distribution was not significant, indicating no influence of tree species diversity on spatial niche segregation in fine roots. Root surface area density and root length density were the highest in NR and lowest in the MZ. Specific root length was in the order of AR > MZ > NR, while specific root surface area was in the order of NR > MZ > AR. There was no significant interaction of stand type and soil depth on specific root length and specific root surface area. Fine root morphological plasticity at the stand level had no significant response to tree species diversity.

  5. Fine-root turnover patterns and their relationship to root diameter and soil depth in a 14C-labeled hardwood forest

    SciTech Connect

    Joslin, Jr., John D; Gaudinski, Julia B.; Torn, Margaret S.; Riley, W. J.; Hanson, Paul J

    2006-01-01

    Characterization of turnover times of fine roots is essential to understanding patterns of carbon allocation in plants and describing forest C cycling. We used the rate of decline in the ratio of 14C to 12C in a mature hardwood forest, enriched by an inadvertent 14C pulse, to investigate fine-root turnover and its relationship with fine-root diameter and soil depth. Biomass and ?14C values were determined for fine roots collected during three consecutive winters from four sites, by depth, diameter size classes (<0.5 or 0.5-2 mm), and live-or-dead status. Live-root pools retained significant 14C enrichment over 3 yr, demonstrating a mean turnover time on the order of years. However, elevated ?14C values in dead-root pools within 18 months of the pulse indicated an additional component of live roots with short turnover times (months). Our results challenge assumptions of a single live fine-root pool with a unimodal and normal age distribution. Live fine roots <0.5 mm and those near the surface, especially those in the O horizon, had more rapid turnover than 0.5-2 mm roots and deeper roots, respectively.

  6. Fine-root turnover patterns and their relationship to root diameter and soil depth in a 14C-labeled hardwood forest.

    PubMed

    Joslin, J D; Gaudinski, J B; Torn, M S; Riley, W J; Hanson, P J

    2006-01-01

    Characterization of turnover times of fine roots is essential to understanding patterns of carbon allocation in plants and describing forest C cycling. We used the rate of decline in the ratio of 14C to 12C in a mature hardwood forest, enriched by an inadvertent 14C pulse, to investigate fine-root turnover and its relationship with fine-root diameter and soil depth. Biomass and Delta14C values were determined for fine roots collected during three consecutive winters from four sites, by depth, diameter size classes (< 0.5 or 0.5-2 mm), and live-or-dead status. Live-root pools retained significant 14C enrichment over 3 yr, demonstrating a mean turnover time on the order of years. However, elevated Delta14C values in dead-root pools within 18 months of the pulse indicated an additional component of live roots with short turnover times (months). Our results challenge assumptions of a single live fine-root pool with a unimodal and normal age distribution. Live fine roots < 0.5 mm and those near the surface, especially those in the O horizon, had more rapid turnover than 0.5-2 mm roots and deeper roots, respectively. PMID:17083682

  7. Fine roots in stands of Fagus sylvatica and Picea abies along a gradient of soil acidification.

    PubMed

    Braun, Sabine; Cantaluppi, Leonardo; Flückiger, Walter

    2005-10-01

    Root length of naturally grown young beech trees (Fagus sylvatica L.) was investigated in 26 forest plots of differing base saturation and nitrogen deposition. The relative length of finest roots (<0.25 mm) was found to decrease in soils with low base saturation. A similar reduction of finest roots in plots with high nitrogen deposition was masked by the effect of base saturation. The formation of adventitious roots was enhanced in acidic soils. The analysis of 128 soil profiles for fine roots of all species present in stands of either Fagus sylvatica L., Picea abies [Karst.] L. or both showed a decreased rooting depth in soils with < or =20% base saturation and in hydromorphic soils. For base rich, well drained soils an average rooting depth of 108 cm was found. This decreased by 28 cm on acidic, well drained soils. The results suggest an effect of the current soil acidification in Switzerland and possibly also of nitrogen deposition on the fine root systems of forest trees.

  8. Identification of coniferous fine roots to species using ribosomal PCR products of pooled root samples

    EPA Science Inventory

    Background/Question/Methods To inform an individual-based forest stand model emphasizing belowground competition, we explored the potential of using the relative abundances of ribosomal PCR products from pooled and milled roots, to allocate total root biomass to each of the thre...

  9. Differences in Fine-Root Biomass of Trees and Understory Vegetation among Stand Types in Subtropical Forests.

    PubMed

    Fu, Xiaoli; Wang, Jianlei; Di, Yuebao; Wang, Huimin

    2015-01-01

    Variation of total fine-root biomass among types of tree stands has previously been attributed to the characteristics of the stand layers. The effects of the understory vegetation on total fine-root biomass are less well studied. We examined the variation of total fine-root biomass in subtropical tree stands at two sites of Datian and Huitong in China. The two sites have similar humid monsoon climate but different soil organic carbon. One examination compared two categories of basal areas (high vs. low basal area) in stands of single species. A second examination compared single-species and mixed stands with comparable basal areas. Low basal area did not correlate with low total fine-root biomass in the single-species stands. The increase in seedling density but decrease in stem density for the low basal area stands at Datian and the quite similar stand structures for the basal-area contrast at Huitong helped in the lack of association between basal area and total fine-root biomass at the two sites, respectively. The mixed stands also did not yield higher total fine-root biomasses. In addition to the lack of niche complementarity between tree species, the differences in stem and seedling densities and the belowground competition between the tree and non-tree species also contributed to the similarity of the total fine-root biomasses in the mixed and single-species stands. Across stand types, the more fertile site Datian yielded higher tree, non-tree and total fine-root biomasses than Huitong. However, the contribution of non-tree fine-root biomass to the total fine-root biomass was higher at Huitong (29.4%) than that at Datian (16.7%). This study suggests that the variation of total fine-root biomass across stand types not only was associated with the characteristics of trees, but also may be highly dependent on the understory layer.

  10. Fine-tuning of bioactive glass for root canal disinfection.

    PubMed

    Waltimo, T; Mohn, D; Paqué, F; Brunner, T J; Stark, W J; Imfeld, T; Schätzle, M; Zehnder, M

    2009-03-01

    An ideal preparation of 45S5 bioactive glass suspensions/slurries for root canal disinfection should combine high pH induction with capacity for continuing release of alkaline species. The hypothesis of this study was that more material per volume of bioactive glass slurry is obtained with a micrometric material (< 5 microm particle size) or a micrometric/ nanometric hybrid, rather than a solely nanometric counterpart. This should correlate with alkaline capacity and antimicrobial effectiveness. Slurries at the plastic limit were prepared with test and reference materials in physiological saline. Total mass and specific surface area of glass material per volume were determined. Continuous titration with hydrochloric acid was performed, and antimicrobial effectiveness was tested in extracted human premolars mono-infected with E. faecalis ATTC 29212 (N = 12 per material). While the nanometric slurry had a 12-fold higher specific surface area than the micrometric counterpart, the latter had a considerably higher alkaline capacity and disinfected significantly better (Fisher's exact test, P < 0.05). The hybrid slurry behaved similarly to the micrometric preparation.

  11. ESTIMATES OF DOUGLAS-FIR FINE ROOT PRODUCTION AND MORTALITY FROM MINIRHIZOTRONS

    EPA Science Inventory

    Minirhizotrons were used to assess the influence of soil resources on fine root (diameter < 2 mm) production, mortality, and standing crop over a two-year period. Two study sites were located, along an elevational transect, in the Oregon Cascade Mountains in mature (> 100 years o...

  12. EFFECTS OF ELEVATED CO2 AND N-FERTILIZATION ON SURVIVAL OF PONDEROSA PINE FINE ROOTS

    EPA Science Inventory

    We used minihizaotrons to assess the effects of elevated CO2N and season on the life-span of ponderosa pine (Pinus ponderosa Dougl. Ex Laws.) fine roots. CO2 levels were ambient air (A), ambient air + 175 ?mol mol-1 (A+175) and ambient air + 350 ?mol mol-1 (A+350). N treatments ...

  13. Water Uptake along the Length of Grapevine Fine Roots: Developmental Anatomy, Tissue-Specific Aquaporin Expression, and Pathways of Water Transport1[W][OPEN

    PubMed Central

    Gambetta, Gregory A.; Fei, Jiong; Rost, Thomas L.; Knipfer, Thorsten; Matthews, Mark A.; Shackel, Ken A.; Walker, M. Andrew; McElrone, Andrew J.

    2013-01-01

    To better understand water uptake patterns in root systems of woody perennial crops, we detailed the developmental anatomy and hydraulic physiology along the length of grapevine (Vitis berlandieri × Vitis rupestris) fine roots from the tip to secondary growth zones. Our characterization included the localization of suberized structures and aquaporin gene expression and the determination of hydraulic conductivity (Lpr) and aquaporin protein activity (via chemical inhibition) in different root zones under both osmotic and hydrostatic pressure gradients. Tissue-specific messenger RNA levels of the plasma membrane aquaporin isogenes (VvPIPs) were quantified using laser-capture microdissection and quantitative polymerase chain reaction. Our results highlight dramatic changes in structure and function along the length of grapevine fine roots. Although the root tip lacked suberization altogether, a suberized exodermis and endodermis developed in the maturation zone, which gave way to the secondary growth zone containing a multilayer suberized periderm. Longitudinally, VvPIP isogenes exhibited strong peaks of expression in the root tip that decreased precipitously along the root length in a pattern similar to Arabidopsis (Arabidopsis thaliana) roots. In the radial orientation, expression was always greatest in interior tissues (i.e. stele, endodermis, and/or vascular tissues) for all root zones. High Lpr and aquaporin protein activity were associated with peak VvPIP expression levels in the root tip. This suggests that aquaporins play a limited role in controlling water uptake in secondary growth zones, which contradicts existing theoretical predictions. Despite having significantly lower Lpr, woody roots can constitute the vast majority of the root system surface area in mature vines and thus provide for significant water uptake potential. PMID:24047863

  14. Fine root dynamics for forests on contrasting soils in the colombian Amazon

    NASA Astrophysics Data System (ADS)

    Jiménez, E. M.; Moreno, F. H.; Lloyd, J.; Peñuela, M. C.; Patiño, S.

    2009-03-01

    It has been hypothesized that in a gradient of increase of soil resources carbon allocated to belowground production (fine roots) decreases. To evaluate this hypothesis, we measured the mass and production of fine roots (<2 mm) by two methods: 1) ingrowth cores and, 2) sequential soil coring, during 2.2 years in two lowland forests with different soils in the colombian Amazon. Differences of soil resources were determined by the type and physical and chemical properties of soil: a forest on loamy soil (Ultisol) at the Amacayacu National Natural Park and, the other on white sands (Spodosol) at the Zafire Biological Station, located in the Forest Reservation of the Calderón River. We found that mass and production of fine roots was significantly different between soil depths (0-10 and 10-20 cm) and also between forests. White-sand forest allocated more carbon to fine roots than the clayey forest; the production in white-sand forest was twice (2.98 and 3.33 Mg C ha-1 year-1, method 1 and 2, respectively) as much as in clayey forest (1.51 and 1.36-1.03 Mg C ha-1 year-1, method 1 and 2, respectively); similarly, the average of fine root mass was higher in the white-sand forest (10.94 Mg C ha-1) than in the forest on clay soils (3.04-3.64 Mg C ha-1). The mass of fine roots also showed a temporal variation related to rainfall, such that production of fine roots decreased substantially in the dry period of the year 2005. Our results suggest that soil resources play an important role in patterns of carbon allocation in these forests; carbon allocated to above-and belowground organs is different between forest types, in such a way that a trade-off above/belowground seems to exist; as a result, it is probable that there are not differences in total net primary productivity between these two forests: does belowground offset lower aboveground production in poorer soils?

  15. Temperature sensitivity of microbial respiration of fine root litter in a temperate broad-leaved forest.

    PubMed

    Makita, Naoki; Kawamura, Ayumi

    2015-01-01

    The microbial decomposition respiration of plant litter generates a major CO2 efflux from terrestrial ecosystems that plays a critical role in the regulation of carbon cycling on regional and global scales. However, the respiration from root litter decomposition and its sensitivity to temperature changes are unclear in current models of carbon turnover in forest soils. Thus, we examined seasonal changes in the temperature sensitivity and decomposition rates of fine root litter of two diameter classes (0-0.5 and 0.5-2.0 mm) of Quercus serrata and Ilex pedunculosa in a deciduous broad-leaved forest. During the study period, fine root litter of both diameter classes and species decreased approximately exponentially over time. The Q10 values of microbial respiration rates of root litter for the two classes were 1.59-3.31 and 1.28-6.27 for Q. serrata and 1.36-6.31 and 1.65-5.86 for I. pedunculosa. A significant difference in Q10 was observed between the diameter classes, indicating that root diameter represents the initial substrate quality, which may determine the magnitude of Q10 value of microbial respiration. Changes in these Q10 values were related to seasonal soil temperature patterns; the values were higher in winter than in summer. Moreover, seasonal variations in Q10 were larger during the 2-year decomposition period than the 1-year period. These results showed that the Q10 values of fine root litter of 0-0.5 and 0.5-2.0 mm have been shown to increase with lower temperatures and with the higher recalcitrance pool of the decomposed substrate during 2 years of decomposition. Thus, the temperature sensitivity of microbial respiration in root litter showed distinct patterns according to the decay period and season because of the temperature acclimation and adaptation of the microbial decomposer communities in root litter. PMID:25658106

  16. Temperature sensitivity of microbial respiration of fine root litter in a temperate broad-leaved forest.

    PubMed

    Makita, Naoki; Kawamura, Ayumi

    2015-01-01

    The microbial decomposition respiration of plant litter generates a major CO2 efflux from terrestrial ecosystems that plays a critical role in the regulation of carbon cycling on regional and global scales. However, the respiration from root litter decomposition and its sensitivity to temperature changes are unclear in current models of carbon turnover in forest soils. Thus, we examined seasonal changes in the temperature sensitivity and decomposition rates of fine root litter of two diameter classes (0-0.5 and 0.5-2.0 mm) of Quercus serrata and Ilex pedunculosa in a deciduous broad-leaved forest. During the study period, fine root litter of both diameter classes and species decreased approximately exponentially over time. The Q10 values of microbial respiration rates of root litter for the two classes were 1.59-3.31 and 1.28-6.27 for Q. serrata and 1.36-6.31 and 1.65-5.86 for I. pedunculosa. A significant difference in Q10 was observed between the diameter classes, indicating that root diameter represents the initial substrate quality, which may determine the magnitude of Q10 value of microbial respiration. Changes in these Q10 values were related to seasonal soil temperature patterns; the values were higher in winter than in summer. Moreover, seasonal variations in Q10 were larger during the 2-year decomposition period than the 1-year period. These results showed that the Q10 values of fine root litter of 0-0.5 and 0.5-2.0 mm have been shown to increase with lower temperatures and with the higher recalcitrance pool of the decomposed substrate during 2 years of decomposition. Thus, the temperature sensitivity of microbial respiration in root litter showed distinct patterns according to the decay period and season because of the temperature acclimation and adaptation of the microbial decomposer communities in root litter.

  17. Fine root biomass, necromass and chemistry during seven years of elevated aluminium concentrations in the soil solution of a middle-aged Picea abies stand.

    PubMed

    Eldhuset, Toril D; Lange, Holger; de Wit, Helene A

    2006-10-01

    Toxic effects of aluminium (Al) on Picea abies (L.) Karst. (Norway spruce) trees are well documented in laboratory-scale experiments, but field-based evidence is scarce. This paper presents results on fine root growth and chemistry from a field manipulation experiment in a P. abies stand that was 45 years old when the experiment started in 1996. Different amounts of dissolved aluminium were added as AlCl3 by means of periodic irrigation during the growing season in the period 1997-2002. Potentially toxic concentrations of Al in the soil solution were obtained. Fine roots were studied from direct cores (1996) and sequential root ingrowth cores (1999, 2001, 2002) in the mineral soil (0-40 cm). We tested two hypotheses: (1) elevated concentration of Al in the root zone leads to significant changes in root biomass, partitioning into fine, coarse, living or dead fractions, and distribution with depth; (2) elevated Al concentration leads to a noticeable uptake of Al and reduced uptake of Ca and Mg; this results in Ca and Mg depletion in roots. Hypothesis 1 was only marginally supported, as just a few significant treatment effects on biomass were found. Hypothesis 2 was supported in part; Al addition led to increased root concentrations of Al in 1999 and 2002 and reduced Mg/Al in 1999. Comparison of roots from subsequent root samplings showed a decrease in Al and S over time. The results illustrated that 7 years of elevated Al(tot) concentrations in the soil solution up to 200 microM are not likely to affect root growth. We also discuss possible improvements of the experimental approach.

  18. Determinate Root Growth and Meristem Maintenance in Angiosperms

    PubMed Central

    Shishkova, S.; Rost, T. L.; Dubrovsky, J. G.

    2008-01-01

    Background The difference between indeterminate and determinate growth in plants consists of the presence or absence of an active meristem in the fully developed organ. Determinate root growth implies that the root apical meristem (RAM) becomes exhausted. As a consequence, all cells in the root tip differentiate. This type of growth is widely found in roots of many angiosperm taxa and might have evolved as a developmental adaptation to water deficit (in desert Cactaceae), or low mineral content in the soil (proteoid roots in various taxa). Scope and Conclusions This review considers the mechanisms of determinate root growth to better understand how the RAM is maintained, how it functions, and the cellular and genetic bases of these processes. The role of the quiescent centre in RAM maintenance and exhaustion will be analysed. During root ageing, the RAM becomes smaller and its organization changes; however, it remains unknown whether every root is truly determinate in the sense that its RAM becomes exhausted before senescence. We define two types of determinate growth: constitutive where determinacy is a natural part of root development; and non-constitutive where determinacy is induced usually by an environmental factor. Determinate root growth is proposed to include two phases: the indeterminate growth phase, when the RAM continuously produces new cells; and the termination growth phase, when cell production gradually decreases and eventually ceases. Finally, new concepts regarding stem cells and a stem cell niche are discussed to help comprehend how the meristem is maintained in a broad taxonomic context. PMID:17954472

  19. Factors Controlling Decomposition Rates of Fine Root Litter in Temperate Forests and Grasslands

    NASA Astrophysics Data System (ADS)

    Solly, E.; Schöning, I.; Trumbore, S.; Michalzik, B.; Schrumpf, M.

    2013-12-01

    Fine root decomposition contributes significantly to biogeochemical cycling in terrestrial ecosystems. Recent studies suggest that root litter is stabilized preferentially compared to shoot litter, contributing in high amounts to soil organic matter. Land use and management may affect root litter decomposition through changes in plant species composition, effects on the decomposer community and differences in soil nutrient availability. We established a large scale root litter decomposition study in three German study regions using a combination of litterbags deployed in forest and grassland sites under different management and soil types. In all three study regions, we compared site-level differences in decomposition by deploying bags containing standardized forest litter in a total of 150 forest plots (50 in each of the three study regions). Bags with standardized grass litter, which had lower lignin content and lignin:N than standardized forest root litter, were similarly distributed across 50 grassland sites in each of the three regions. Standardized fine grass roots decomposed on average faster 23.5 × 6.3% compared to forest roots 11.7 × 4.4% (p < 0.001) when deployed in their respective land use. Fine root decomposition of standardized litter was affected by study region with higher mass losses in northern Germany followed by mass loss rates in central and southern Germany (p < 0.05). Given the standardized litter chemistry, these differences mainly reflect the influence of climate and soil differences between study regions. Within the central German region (Hainich-Dün), we also compared rates of mass loss of root litter collected on-site as part of a second, parallel litterbag deployment to tease apart the influences of litter quality from other factors (such as soil properties and climate) that affect mass loss rates. Despite differences in the initial fine root litter quality, the average mass lost during 12 months for on-site litter was similar to

  20. Phene synergism between root hair length and basal root growth angle for phosphorus acquisition.

    PubMed

    Miguel, Magalhaes Amade; Postma, Johannes Auke; Lynch, Jonathan Paul

    2015-04-01

    Shallow basal root growth angle (BRGA) increases phosphorus acquisition efficiency by enhancing topsoil foraging because in most soils, phosphorus is concentrated in the topsoil. Root hair length and density (RHL/D) increase phosphorus acquisition by expanding the soil volume subject to phosphorus depletion through diffusion. We hypothesized that shallow BRGA and large RHL/D are synergetic for phosphorus acquisition, meaning that their combined effect is greater than the sum of their individual effects. To evaluate this hypothesis, phosphorus acquisition in the field in Mozambique was compared among recombinant inbred lines of common bean (Phaseolus vulgaris) having four distinct root phenotypes: long root hairs and shallow basal roots, long root hairs and deep basal roots, short root hairs and shallow basal roots, and short root hairs and deep basal roots. The results revealed substantial synergism between BRGA and RHL/D. Compared with short-haired, deep-rooted phenotypes, long root hairs increased shoot biomass under phosphorus stress by 89%, while shallow roots increased shoot biomass by 58%. Genotypes with both long root hairs and shallow roots had 298% greater biomass accumulation than short-haired, deep-rooted phenotypes. Therefore, the utility of shallow basal roots and long root hairs for phosphorus acquisition in combination is twice as large as their additive effects. We conclude that the anatomical phene of long, dense root hairs and the architectural phene of shallower basal root growth are synergetic for phosphorus acquisition. Phene synergism may be common in plant biology and can have substantial importance for plant fitness, as shown here.

  1. Phene Synergism between Root Hair Length and Basal Root Growth Angle for Phosphorus Acquisition1[OPEN

    PubMed Central

    Miguel, Magalhaes Amade

    2015-01-01

    Shallow basal root growth angle (BRGA) increases phosphorus acquisition efficiency by enhancing topsoil foraging because in most soils, phosphorus is concentrated in the topsoil. Root hair length and density (RHL/D) increase phosphorus acquisition by expanding the soil volume subject to phosphorus depletion through diffusion. We hypothesized that shallow BRGA and large RHL/D are synergetic for phosphorus acquisition, meaning that their combined effect is greater than the sum of their individual effects. To evaluate this hypothesis, phosphorus acquisition in the field in Mozambique was compared among recombinant inbred lines of common bean (Phaseolus vulgaris) having four distinct root phenotypes: long root hairs and shallow basal roots, long root hairs and deep basal roots, short root hairs and shallow basal roots, and short root hairs and deep basal roots. The results revealed substantial synergism between BRGA and RHL/D. Compared with short-haired, deep-rooted phenotypes, long root hairs increased shoot biomass under phosphorus stress by 89%, while shallow roots increased shoot biomass by 58%. Genotypes with both long root hairs and shallow roots had 298% greater biomass accumulation than short-haired, deep-rooted phenotypes. Therefore, the utility of shallow basal roots and long root hairs for phosphorus acquisition in combination is twice as large as their additive effects. We conclude that the anatomical phene of long, dense root hairs and the architectural phene of shallower basal root growth are synergetic for phosphorus acquisition. Phene synergism may be common in plant biology and can have substantial importance for plant fitness, as shown here. PMID:25699587

  2. Forest fine-root production and nitrogen use under elevated CO2: Contrasting responses explained by a common principle

    SciTech Connect

    Franklin, Oscar; McMurtrie, Ross E; Iversen, Colleen M; Crous, Kristine; Finzi, Adrien C; Tissue, David Thomas; Ellsworth, David; Oren, Ram; Norby, Richard J

    2009-01-01

    Despite the importance of nitrogen (N) limitation of forest carbon (C) sequestration at rising atmospheric CO2 concentration, the mechanisms responsible are not well understood. To elucidate the interactive effects of elevated CO2 (eCO2) and soil N availability on forest productivity and C allocation, we hypothesized that 1) trees maximize fitness by allocating N and C to maximize their net growth, and 2) that N uptake is controlled by root exploration for N. We tested this model using data collected in FACE sites dominated by evergreen (Pinus taeda; Duke Forest) and deciduous (Liquidambar styraciflua; Oak Ridge National Laboratory ORNL) trees. The model explained 80-95% of variation in productivity and N-uptake data among eCO2, N fertilization and control treatments over six years. The model explains why fine-root production increased, and why N uptake increased despite reduced soil N availability under eCO2 at ORNL and Duke. In agreement with observations at other sites, soil N availability reduced below a critical level diminishes all eCO2 responses. At Duke, a negative feedback between reduced soil N availability and N uptake counteracted progressive reduction in soil N availability at eCO2. At ORNL, decreasing soil N availability was perpetuated as it generated no reduction in N uptake, due to strongly increased production of fast turnover fine-roots. This implies that species with fast root turnover could be more prone to progressive N limitation of carbon sequestration in woody biomass than species with slow root turnover, such as evergreens.

  3. Differential responses of grapevine rootstocks to water stress are associated with adjustments in fine root hydraulic physiology and suberization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Water deficits are known to alter fine root structure and function, but little is known about how these responses contribute to differences in drought resistance across grapevine rootstocks. We studied how water deficit affects root anatomical and physiological characteristics in two grapevine root...

  4. The Effect of Phosphorus Availability on Fine Root Decomposition in Western Oregon

    NASA Astrophysics Data System (ADS)

    van Huysen, T.; Harmon, M.; Perakis, S.

    2005-12-01

    We are examining fine root decomposition at three sites in western Oregon, USA to determine whether phosphorus availability serves as a proximate control of nitrogen dynamics in fine root decomposition. More specifically, we are testing the hypothesis that external (soil P) and internal (root P content) supplies of P influence release of N from roots decomposing in soils that are low in available P. A factorial fertilization experiment is being used to test this hypothesis. At each of the three sites, P fertilizer has been added to six plots to enhance soil P availability and six plots have remained unfertilized. Litterbags containing Douglas-fir roots, needles, or twigs were placed in all plots. Half of the litterbags contain plant material from seedlings that were fertilized with P, resulting in four treatments: P added to soil and litter, P added to soil but not to litter, P added to litter but not to soil, and P not added to soil or litter (control). Data from soil cores collected in the treatment plots at each site and extracted with Bray solution indicate that extractable P is significantly higher (P < 0.001) in the plots that have been fertilized with P. Extractable P (mg P/kg soil) is approximately 50 mg higher in the fertilized plots than the unfertilized plots. Material from litterbags collected this summer is currently being processed and analyzed for C, N, and P content and mass loss to determine decomposition rates for the three litter types.

  5. Scots pine fine roots adjust along a 2000-km latitudinal climatic gradient.

    PubMed

    Zadworny, Marcin; McCormack, M Luke; Mucha, Joanna; Reich, Peter B; Oleksyn, Jacek

    2016-10-01

    Patterns of plant biomass allocation and functional adjustments along climatic gradients are poorly understood, particularly belowground. Generally, low temperatures suppress nutrient release and uptake, and forests under such conditions have a greater proportion of their biomass in roots. However, it is not clear whether 'more roots' means better capacity to acquire soil resources. Herein we quantified patterns of fine-root anatomy and their biomass distribution across Scots pine (Pinus sylvestris) populations both along a 2000-km latitudinal gradient and within a common garden experiment with a similar range of populations. We found that with decreasing mean temperature, a greater percentage of Scots pine root biomass was allocated to roots with higher potential absorptive capacity. Similar results were seen in the common experimental site, where cold-adapted populations produced roots with greater absorptive capacity than populations originating from warmer climates. These results demonstrate that plants growing in or originated from colder climates have more acquisitive roots, a trait that is likely adaptive in the face of the low resource availability typical of cold soils. PMID:27301778

  6. Effects of spatiotemporal variation of soil salinity on fine root distribution in different plant configuration modes in new reclamation coastal saline field.

    PubMed

    Jiang, Hong; Du, Hongyu; Bai, Yingying; Hu, Yue; Rao, Yingfu; Chen, Chong; Cai, Yongli

    2016-04-01

    In order to study the effects of salinity on plant fine roots, we considered three different plant configuration modes (tree stand model (TSM), shrub stand model (SSM), and tree-shrub stand model (TSSM)). Soil samples were collected with the method of soil drilling. Significant differences of electrical conductivity (EC) in the soil depth of 0-60 cm were observed among the three modes (p < 0.05). In the above three modes, the variation of soil salinity among various soil layers and monthly variation of soil salinity were the highest in SSM and reached 2.30 and 2.23 mS/cm (EC1:5), respectively. Due to the effect of salinity, fine root biomass (FRB) showed significant differences in different soil depths (p < 0.05). More than 60% of FRB was concentrated in the soil depth above 30 cm. FRB showed exponential decline with soil depth (p < 0.05). FRB showed spatial heterogeneity in the 40-cm soil depth. In the above three modes, compared with FRB, specific root length (SRL) and fine root length density (FRLD) showed the similar changing trend. Fine roots showed significant seasonal differences among different modes (p < 0.05). FRB showed the bimodal variation and was the highest in July. However, we found that the high content of salts had obvious inhibitory effect on the distribution of FRB. Therefore, the salinity should be below 1.5 mS/cm, which was suitable for the growth of plant roots. Among the three modes, TSSM had the highest FRB, SRL, and FRLD and no obvious soil salt accumulation was observed. The results indicated that fine root biomass was affected by high salt and that TSSM had the strong effects of salt suppression and control. In our study, TSSM may be the optimal configuration mode for salt suppression and control in saline soil.

  7. Effects of spatiotemporal variation of soil salinity on fine root distribution in different plant configuration modes in new reclamation coastal saline field.

    PubMed

    Jiang, Hong; Du, Hongyu; Bai, Yingying; Hu, Yue; Rao, Yingfu; Chen, Chong; Cai, Yongli

    2016-04-01

    In order to study the effects of salinity on plant fine roots, we considered three different plant configuration modes (tree stand model (TSM), shrub stand model (SSM), and tree-shrub stand model (TSSM)). Soil samples were collected with the method of soil drilling. Significant differences of electrical conductivity (EC) in the soil depth of 0-60 cm were observed among the three modes (p < 0.05). In the above three modes, the variation of soil salinity among various soil layers and monthly variation of soil salinity were the highest in SSM and reached 2.30 and 2.23 mS/cm (EC1:5), respectively. Due to the effect of salinity, fine root biomass (FRB) showed significant differences in different soil depths (p < 0.05). More than 60% of FRB was concentrated in the soil depth above 30 cm. FRB showed exponential decline with soil depth (p < 0.05). FRB showed spatial heterogeneity in the 40-cm soil depth. In the above three modes, compared with FRB, specific root length (SRL) and fine root length density (FRLD) showed the similar changing trend. Fine roots showed significant seasonal differences among different modes (p < 0.05). FRB showed the bimodal variation and was the highest in July. However, we found that the high content of salts had obvious inhibitory effect on the distribution of FRB. Therefore, the salinity should be below 1.5 mS/cm, which was suitable for the growth of plant roots. Among the three modes, TSSM had the highest FRB, SRL, and FRLD and no obvious soil salt accumulation was observed. The results indicated that fine root biomass was affected by high salt and that TSSM had the strong effects of salt suppression and control. In our study, TSSM may be the optimal configuration mode for salt suppression and control in saline soil. PMID:26645228

  8. [Effects nutrients on the seedlings root hair development and root growth of Poncirus trifoliata under hydroponics condition].

    PubMed

    Cao, Xiu; Xia, Ren-Xue; Zhang, De-Jian; Shu, Bo

    2013-06-01

    Ahydroponics experiment was conducted to study the effects of nutrients (N, P, K, Ca, Mg, Fe, and Mn) deficiency on the length of primary root, the number of lateral roots, and the root hair density, length, and diameter on the primary root and lateral roots of Poncirus trifoliata seedlings. Under the deficiency of each test nutrient, root hair could generate, but was mainly concentrated on the root base and fewer on the root tip. The root hair density on lateral roots was significantly larger than that on primary root, but the root hair length was in adverse. The deficiency of each test nutrient had greater effects on the growth and development of root hairs, with the root hair density on primary root varied from 55.0 to 174.3 mm(-2). As compared with the control, Ca deficiency induced the significant increase of root hair density and length on primary root, P deficiency promoted the root hair density and length on the base and middle part of primary root and on the lateral roots significantly, Fe deficiency increased the root hair density but decreased the root hair length on the tip of primary root significantly, K deficiency significantly decreased the root hair density, length, and diameter on primary root and lateral roots, whereas Mg deficiency increased the root hair length of primary root significantly. In all treatments of nutrient deficiency, the primary root had the similar growth rate, but, with the exceptions of N and Mg deficiency, the lateral roots exhibited shedding and regeneration.

  9. Fine roots are the dominant source of recalcitrant plant litter in sugar maple-dominated northern hardwood forests.

    PubMed

    Xia, Mengxue; Talhelm, Alan F; Pregitzer, Kurt S

    2015-11-01

    Most studies of forest litter dynamics examine the biochemical characteristics and decomposition of leaf litter, but fine roots are also a large source of litter in forests. We quantified the concentrations of eight biochemical fractions and nitrogen (N) in leaf litter and fine roots at four sugar maple (Acer saccharum)-dominated hardwood forests in the north-central United States. We combined these results with litter production data to estimate ecosystem biochemical fluxes to soil. We also compared how leaf litter and fine root biochemistry responded to long-term simulated N deposition. Compared with leaf litter, fine roots contained 2.9-fold higher acid-insoluble fraction (AIF) and 2.3-fold more condensed tannins; both are relatively difficult to decompose. Comparatively, leaf litter had greater quantities of more labile components: nonstructural carbohydrates, cellulose and soluble phenolics. At an ecosystem scale, fine roots contributed over two-thirds of the fluxes of AIF and condensed tannins to soil. Fine root biochemistry was also less responsive than leaf litter to long-term simulated N deposition. Fine roots were the dominant source of difficult-to-decompose plant carbon fractions entering the soil at our four study sites. Based on our synthesis of the literature, this pattern appears to be widespread in boreal and temperate forests.

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

    PubMed Central

    Kubisch, Petra; Hertel, Dietrich; Leuschner, Christoph

    2016-01-01

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

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

    PubMed Central

    Kubisch, Petra; Hertel, Dietrich; Leuschner, Christoph

    2016-01-01

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

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

    PubMed

    Kubisch, Petra; Hertel, Dietrich; Leuschner, Christoph

    2016-01-01

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

  13. Plant uptake, translocation, and return of polycyclic aromatic hydrocarbons via fine root branch orders in a subtropical forest ecosystem.

    PubMed

    Chen, Zheng-Xia; Ni, Hong-Gang; Jing, Xin; Chang, Wen-Jing; Sun, Jian-Lin; Zeng, Hui

    2015-07-01

    Fine roots of woody plants are a heterogeneous system differing markedly in structure and function. Nevertheless, knowledge about the plant uptake of organic pollutants via fine roots is scarce to date. In the present study, plant uptake, translocation, and return of polycyclic aromatic hydrocarbons (PAHs) via fine roots in a subtropical forest ecosystem were investigated. Levels of Σ15PAHs in different fine root branch orders of Michelia macclurei, Cryptocarya concinna, Cryptocarya chinensis, and Canthium dicoccums varied from 5072±1419 ng g(-1) to 6080±1656 ng g(-1), 4037±410 ng g(-1) to 6101±972 ng g(-1), 3308±1191 ng g(-1) to 4283±237 ng g(-1), and 3737±800 ng g(-1) to 4895±1216 ng g(-1), respectively. Overall, concentrations of low-molecular-weight PAHs with 2-3 aromatic rings were higher than high-molecular-weight PAHs with 4-6 aromatic rings in all fine root branch orders. There were obvious translocations of PAHs between adjacent branch orders and a net accumulation of PAHs may occur in the fourth- and fifth-order roots. The storage of PAHs in the fine root system showed an obvious increasing trend along the branch orders ascending for all tree species. The return flux of PAHs via fine roots mortality showed an obvious decreasing trend with the branch orders ascending across the four tree species. Lower order roots contributed greatly to the total PAHs return flux. Our results indicated that fine roots turnover is an effective pathway for perennial tree species to remove environmental toxicants absorbed into them.

  14. Plant uptake, translocation, and return of polycyclic aromatic hydrocarbons via fine root branch orders in a subtropical forest ecosystem.

    PubMed

    Chen, Zheng-Xia; Ni, Hong-Gang; Jing, Xin; Chang, Wen-Jing; Sun, Jian-Lin; Zeng, Hui

    2015-07-01

    Fine roots of woody plants are a heterogeneous system differing markedly in structure and function. Nevertheless, knowledge about the plant uptake of organic pollutants via fine roots is scarce to date. In the present study, plant uptake, translocation, and return of polycyclic aromatic hydrocarbons (PAHs) via fine roots in a subtropical forest ecosystem were investigated. Levels of Σ15PAHs in different fine root branch orders of Michelia macclurei, Cryptocarya concinna, Cryptocarya chinensis, and Canthium dicoccums varied from 5072±1419 ng g(-1) to 6080±1656 ng g(-1), 4037±410 ng g(-1) to 6101±972 ng g(-1), 3308±1191 ng g(-1) to 4283±237 ng g(-1), and 3737±800 ng g(-1) to 4895±1216 ng g(-1), respectively. Overall, concentrations of low-molecular-weight PAHs with 2-3 aromatic rings were higher than high-molecular-weight PAHs with 4-6 aromatic rings in all fine root branch orders. There were obvious translocations of PAHs between adjacent branch orders and a net accumulation of PAHs may occur in the fourth- and fifth-order roots. The storage of PAHs in the fine root system showed an obvious increasing trend along the branch orders ascending for all tree species. The return flux of PAHs via fine roots mortality showed an obvious decreasing trend with the branch orders ascending across the four tree species. Lower order roots contributed greatly to the total PAHs return flux. Our results indicated that fine roots turnover is an effective pathway for perennial tree species to remove environmental toxicants absorbed into them. PMID:25863163

  15. Traceable calibration, performance metrics, and uncertainty estimates of minirhizotron digital imagery for fine-root measurements.

    PubMed

    Roberti, Joshua A; SanClements, Michael D; Loescher, Henry W; Ayres, Edward

    2014-01-01

    Even though fine-root turnover is a highly studied topic, it is often poorly understood as a result of uncertainties inherent in its sampling, e.g., quantifying spatial and temporal variability. While many methods exist to quantify fine-root turnover, use of minirhizotrons has increased over the last two decades, making sensor errors another source of uncertainty. Currently, no standardized methodology exists to test and compare minirhizotron camera capability, imagery, and performance. This paper presents a reproducible, laboratory-based method by which minirhizotron cameras can be tested and validated in a traceable manner. The performance of camera characteristics was identified and test criteria were developed: we quantified the precision of camera location for successive images, estimated the trueness and precision of each camera's ability to quantify root diameter and root color, and also assessed the influence of heat dissipation introduced by the minirhizotron cameras and electrical components. We report detailed and defensible metrology analyses that examine the performance of two commercially available minirhizotron cameras. These cameras performed differently with regard to the various test criteria and uncertainty analyses. We recommend a defensible metrology approach to quantify the performance of minirhizotron camera characteristics and determine sensor-related measurement uncertainties prior to field use. This approach is also extensible to other digital imagery technologies. In turn, these approaches facilitate a greater understanding of measurement uncertainties (signal-to-noise ratio) inherent in the camera performance and allow such uncertainties to be quantified and mitigated so that estimates of fine-root turnover can be more confidently quantified.

  16. Traceable calibration, performance metrics, and uncertainty estimates of minirhizotron digital imagery for fine-root measurements.

    PubMed

    Roberti, Joshua A; SanClements, Michael D; Loescher, Henry W; Ayres, Edward

    2014-01-01

    Even though fine-root turnover is a highly studied topic, it is often poorly understood as a result of uncertainties inherent in its sampling, e.g., quantifying spatial and temporal variability. While many methods exist to quantify fine-root turnover, use of minirhizotrons has increased over the last two decades, making sensor errors another source of uncertainty. Currently, no standardized methodology exists to test and compare minirhizotron camera capability, imagery, and performance. This paper presents a reproducible, laboratory-based method by which minirhizotron cameras can be tested and validated in a traceable manner. The performance of camera characteristics was identified and test criteria were developed: we quantified the precision of camera location for successive images, estimated the trueness and precision of each camera's ability to quantify root diameter and root color, and also assessed the influence of heat dissipation introduced by the minirhizotron cameras and electrical components. We report detailed and defensible metrology analyses that examine the performance of two commercially available minirhizotron cameras. These cameras performed differently with regard to the various test criteria and uncertainty analyses. We recommend a defensible metrology approach to quantify the performance of minirhizotron camera characteristics and determine sensor-related measurement uncertainties prior to field use. This approach is also extensible to other digital imagery technologies. In turn, these approaches facilitate a greater understanding of measurement uncertainties (signal-to-noise ratio) inherent in the camera performance and allow such uncertainties to be quantified and mitigated so that estimates of fine-root turnover can be more confidently quantified. PMID:25391023

  17. Fine roots, arbuscular mycorrhizal hyphae and soil nutrients in four neotropical rain forests: patterns across large geographic distances.

    PubMed

    Powers, Jennifer S; Treseder, Kathleen K; Lerdau, Manuel T

    2005-03-01

    * It is commonly hypothesized that stand-level fine root biomass increases as soil fertility decreases both within and among tropical forests, but few data exist to test this prediction across broad geographic scales. This study investigated the relationships among fine roots, arbuscular mycorrhizal (AM) fungi and soil nutrients in four lowland, neotropical rainforests. * Within each forest, samples were collected from plots that differed in fertility and above-ground biomass, and fine roots, AM hyphae and total soil nutrients were measured. * Among sites, total fine root mass varied by a factor of three, from 237+/-19 g m-2 in Costa Rica to 800+/-116 g m-2 in Brazil (0-40 cm depth). Both root mass and length were negatively correlated to soil nitrogen and phosphorus, but AM hyphae were not related to nutrients, root properties or above-ground biomass. * These results suggest that understanding how soil fertility affects fine roots is an additional factor that may improve the representation of root functions in global biogeochemical models or biome-wide averages of root properties in tropical forests. PMID:15720702

  18. A Simple Device to Measure Root Growth Rates

    ERIC Educational Resources Information Center

    Rauser, Wilfried E.; Horton, Roger F.

    1975-01-01

    Describes construction and use of a simple auxanometer which students can use to accurately measure root growth rates of intact seedlings. Typical time course data are presented for the effect of ethylene and indole acetic acid on pea root growth. (Author/BR)

  19. Fine-scale genetic structure of grape phylloxera from the roots and leaves of Vitis.

    PubMed

    Corrie, A M; Hoffmann, A A

    2004-02-01

    Patterns of variation at microsatellite loci suggest that root populations of the pest grape phylloxera (Daktulosphaira vitifoliae) are largely parthenogenetic in Australian vineyards. To investigate reproduction in leaf galling phylloxera and the association between these individuals and phylloxera on roots, we examined in detail genetic variation in phylloxera from a vineyard block. Some genotypes found on leaf galls within this block were not present on roots, whereas others spanned both zones. There was no evidence that genotypes on roots were the product of sexual reproduction in leaf galls. mtDNA variation was not associated with the location of the phylloxera clones. The spatial distribution of genotypes within a root population was further investigated by intensively sampling phylloxera from another vineyard block. Join-count spatial autocorrelation statistics were used to explore fine-scale spatial structure. Clones were nonrandomly distributed within the block and there was evidence that the distribution of clones followed rows. These findings suggest firstly that there is limited dispersal of root and leaf feeding phylloxera, and secondly that factors, other than vine host, are likely to be important and contribute to clonal structure within populations.

  20. Melatonin promotes seminal root elongation and root growth in transgenic rice after germination.

    PubMed

    Park, Sangkyu; Back, Kyoungwhan

    2012-11-01

    The effect of melatonin on root growth after germination was examined in transgenic rice seedlings expressing sheep serotonin N-acetyltransferase (NAT). Enhanced melatonin levels were found in T(3) homozygous seedlings because of the ectopic overexpression of sheep NAT, which is believed to be the rate-limiting enzyme in melatonin biosynthesis in animals. Compared with wild-type rice seeds, the transgenic rice seeds showed enhanced seminal root growth and an analogous number of adventitious roots 4 and 10 days after seeding on half-strength Murashige and Skoog medium. The enhanced initial seminal root growth in the transgenic seedlings matched their increased root biomass well. We also found that treatment with 0.5 and 1 μM melatonin promoted seminal root growth of the wild type under continuous light. These results indicate that melatonin plays an important role in regulating both seminal root length and root growth after germination in monocotyledonous rice plants. This is the first report on the effects of melatonin on root growth in gain-of-function mutant plants that produce high levels of melatonin.

  1. Root growth, secondary root formation and root gravitropism in carotenoid-deficient seedlings of Zea mays L

    NASA Technical Reports Server (NTRS)

    Ng, Y. K.; Moore, R.

    1985-01-01

    The effect of ABA on root growth, secondary-root formation and root gravitropism in seedlings of Zea mays was investigated by using Fluridone-treated seedlings and a viviparous mutant, both of which lack carotenoids and ABA. Primary roots of seedlings grown in the presence of Fluridone grew significantly slower than those of control (i.e. untreated) roots. Elongation of Fluridone-treated roots was inhibited significantly by the exogenous application of 1 mM ABA. Exogenous application of 1 micromole and 1 nmole ABA had either no effect or only a slight stimulatory effect on root elongation, depending on the method of application. The absence of ABA in Fluridone-treated plants was not an important factor in secondary-root formation in seedlings less than 9-10 d old. However, ABA may suppress secondary-root formation in older seedlings, since 11-d-old control seedlings had significantly fewer secondary roots than Fluridone-treated seedlings. Roots of Fluridone-treated and control seedlings were graviresponsive. Similar data were obtained for vp-9 mutants of Z. mays, which are phenotypically identical to Fluridone-treated seedlings. These results indicate that ABA is necessary for neither secondary-root formation nor for positive gravitropism by primary roots.

  2. Tree Age Effects on Fine Root Biomass and Morphology over Chronosequences of Fagus sylvatica, Quercus robur and Alnus glutinosa Stands.

    PubMed

    Jagodzinski, Andrzej M; Ziółkowski, Jędrzej; Warnkowska, Aleksandra; Prais, Hubert

    2016-01-01

    There are few data on fine root biomass and morphology change in relation to stand age. Based on chronosequences for beech (9-140 years old), oak (11-140 years) and alder (4-76 years old) we aimed to examine how stand age affects fine root biomass and morphology. Soil cores from depths of 0-15 cm and 16-30 cm were used for the study. In contrast to previously published studies that suggested that maximum fine root biomass is reached at the canopy closure stage of stand development, we found almost linear increases of fine root biomass over stand age within the chronosequences. We did not observe any fine root biomass peak in the canopy closure stage. However, we found statistically significant increases of mean fine root biomass for the average individual tree in each chronosequence. Mean fine root biomass (0-30 cm) differed significantly among tree species chronosequences studied and was 4.32 Mg ha(-1), 3.71 Mg ha(-1) and 1.53 Mg ha(-1), for beech, oak and alder stands, respectively. The highest fine root length, surface area, volume and number of fine root tips (0-30 cm soil depth), expressed on a stand area basis, occurred in beech stands, with medium values for oak stands and the lowest for alder stands. In the alder chronosequence all these values increased with stand age, in the beech chronosequence they decreased and in the oak chronosequence they increased until ca. 50 year old stands and then reached steady-state. Our study has proved statistically significant negative relationships between stand age and specific root length (SRL) in 0-30 cm soil depth for beech and oak chronosequences. Mean SRLs for each chronosequence were not significantly different among species for either soil depth studied. The results of this study indicate high fine root plasticity. Although only limited datasets are currently available, these data have provided valuable insight into fine root biomass and morphology of beech, oak and alder stands.

  3. Tree Age Effects on Fine Root Biomass and Morphology over Chronosequences of Fagus sylvatica, Quercus robur and Alnus glutinosa Stands

    PubMed Central

    Jagodzinski, Andrzej M.; Ziółkowski, Jędrzej; Warnkowska, Aleksandra; Prais, Hubert

    2016-01-01

    There are few data on fine root biomass and morphology change in relation to stand age. Based on chronosequences for beech (9–140 years old), oak (11–140 years) and alder (4–76 years old) we aimed to examine how stand age affects fine root biomass and morphology. Soil cores from depths of 0–15 cm and 16–30 cm were used for the study. In contrast to previously published studies that suggested that maximum fine root biomass is reached at the canopy closure stage of stand development, we found almost linear increases of fine root biomass over stand age within the chronosequences. We did not observe any fine root biomass peak in the canopy closure stage. However, we found statistically significant increases of mean fine root biomass for the average individual tree in each chronosequence. Mean fine root biomass (0–30 cm) differed significantly among tree species chronosequences studied and was 4.32 Mg ha-1, 3.71 Mg ha-1 and 1.53 Mg ha-1, for beech, oak and alder stands, respectively. The highest fine root length, surface area, volume and number of fine root tips (0–30 cm soil depth), expressed on a stand area basis, occurred in beech stands, with medium values for oak stands and the lowest for alder stands. In the alder chronosequence all these values increased with stand age, in the beech chronosequence they decreased and in the oak chronosequence they increased until ca. 50 year old stands and then reached steady-state. Our study has proved statistically significant negative relationships between stand age and specific root length (SRL) in 0–30 cm soil depth for beech and oak chronosequences. Mean SRLs for each chronosequence were not significantly different among species for either soil depth studied. The results of this study indicate high fine root plasticity. Although only limited datasets are currently available, these data have provided valuable insight into fine root biomass and morphology of beech, oak and alder stands. PMID:26859755

  4. 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.

  5. Complementarity in nutrient foraging strategies of absorptive fine roots and arbuscular mycorrhizal fungi across 14 coexisting subtropical tree species.

    PubMed

    Liu, Bitao; Li, Hongbo; Zhu, Biao; Koide, Roger T; Eissenstat, David M; Guo, Dali

    2015-10-01

    In most cases, both roots and mycorrhizal fungi are needed for plant nutrient foraging. Frequently, the colonization of roots by arbuscular mycorrhizal (AM) fungi seems to be greater in species with thick and sparsely branched roots than in species with thin and densely branched roots. Yet, whether a complementarity exists between roots and mycorrhizal fungi across these two types of root system remains unclear. We measured traits related to nutrient foraging (root morphology, architecture and proliferation, AM colonization and extramatrical hyphal length) across 14 coexisting AM subtropical tree species following root pruning and nutrient addition treatments. After root pruning, species with thinner roots showed more root growth, but lower mycorrhizal colonization, than species with thicker roots. Under multi-nutrient (NPK) addition, root growth increased, but mycorrhizal colonization decreased significantly, whereas no significant changes were found under nitrogen or phosphate additions. Moreover, root length proliferation was mainly achieved by altering root architecture, but not root morphology. Thin-root species seem to forage nutrients mainly via roots, whereas thick-root species rely more on mycorrhizal fungi. In addition, the reliance on mycorrhizal fungi was reduced by nutrient additions across all species. These findings highlight complementary strategies for nutrient foraging across coexisting species with contrasting root traits.

  6. Effect of drought on fine roots productivity in poplar-based short rotation coppice

    NASA Astrophysics Data System (ADS)

    Mani Tripathi, Abhishek; Fischer, Milan; Berhongaray, Gonzalo; Orság, Matěj; Trnka, Miroslav

    2015-04-01

    Short rotation woody crops (SRWC) are alternative source of bioenergy, which apart from their 'carbon neutrality' have potential to store carbon (C) into soil and mitigate the increasing CO2 emission. Studies of below ground biomass of trees are divided into two types according to root diameter - analysis of fine roots (less than 2 mm) and coarse roots (more than 2 mm). Trees roots are spatially highly heterogeneous and it requires large number of samples to obtain a representative estimate of belowground biomass. For this study we used hybrid poplar clone J-105 (Populus nigra x P. maximowiczii) grown under short rotation coppice system in the region of Bohemian-Moravian Highland (49o32'N, 16o15'E and altitude 530 m a.s.l.) since April 2000. The plantation with planting density of 9,216 trees ha-1 was established on the former agricultural land and the length of the rotation cycle was set to 6-8 years. While mean annual rainfall was 609 mm with mean annual temperature 7.2oC during 1981-2013 significant increase of temperature and more frequent droughts are expected. In 2011, we established drought experiment based on throughfall exclusion system, reducing up to 70 % of throughfall precipitation. Thus 2 treatments with normal and lowered soil moisture levels were introduced. In January and February 2014, we cored 18 places including drought and control using root bipartite auger. The main goal of the study is to assess the response of fine roots productivity and fine roots vertical distribution on the reduced soil water availability. Results will be presented at the conference. Acknowledgements: This study was funded by research project IGA Mendel University 2014 "Study of below ground biomass in short rotation poplar coppice (J-105) in the Czech-Moravian Highlands", project PASED (KONTAKT II LH12037 ʺDevelopment of models for the assessment of abiotic stresses in selected energy woody plantsʺ and "Building up a multidisciplinary scientific team focused on drought

  7. Ozone decreases spring root growth and root carbohydrate content in ponderosa pine the year following exposure

    SciTech Connect

    Andersen, C.P.; Hogsett, W.E.; Wessling, R.; Plocher, M.

    1991-01-01

    Storage carbohydrates are extremely important for new shoot and root development following dormancy or during periods of high stress. The hypothesis that ozone decreases carbohydrate storage and decreases new root growth during the year following exposure was investigated. The results suggest that (1) ponderosa pine seedlings exposed to 122 and 169 ppm hrs ozone for one season have significantly less root starch reserves available just prior to and during bud break the following year, and (2) spring root growth is decreased following ozone exposure. The carry-over effects of ozone stress may be important in long-lived perennial species which are annually subjected to ozone.

  8. Phenolic profile within the fine-root branching orders of an evergreen species highlights a disconnect in root tissue quality predicted by elemental- and molecular-level carbon composition.

    PubMed

    Wang, Jun-Jian; Tharayil, Nishanth; Chow, Alex T; Suseela, Vidya; Zeng, Hui

    2015-06-01

    Fine roots constitute a significant source of plant productivity and litter turnover across terrestrial ecosystems, but less is known about the quantitative and qualitative profile of phenolic compounds within the fine-root architecture, which could regulate the potential contribution of plant roots to the soil organic matter pool. To understand the linkage between traditional macro-elemental and morphological traits of roots and their molecular-level carbon chemistry, we analyzed seasonal variations in monomeric yields of the free, bound, and lignin phenols in fine roots (distal five orders) and leaves of Ardisia quinquegona. Fine roots contained two-fold higher concentrations of bound phenols and three-fold higher concentrations of lignin phenols than leaves. Within fine roots, the concentrations of free and bound phenols decreased with increasing root order, and seasonal variation in the phenolic profile was more evident in lower order than in higher order roots. The morphological and macro-elemental root traits were decoupled from the quantity, composition and tissue association of phenolic compounds, revealing the potential inability of these traditional parameters to capture the molecular identity of phenolic carbon within the fine-root architecture and between fine roots and leaves. Our results highlight the molecular-level heterogeneity in phenolic carbon composition within the fine-root architecture, and imply that traits that capture the molecular identity of the root construct might better predict the decomposition dynamics within fine-root orders.

  9. Phenolic profile within the fine-root branching orders of an evergreen species highlights a disconnect in root tissue quality predicted by elemental- and molecular-level carbon composition.

    PubMed

    Wang, Jun-Jian; Tharayil, Nishanth; Chow, Alex T; Suseela, Vidya; Zeng, Hui

    2015-06-01

    Fine roots constitute a significant source of plant productivity and litter turnover across terrestrial ecosystems, but less is known about the quantitative and qualitative profile of phenolic compounds within the fine-root architecture, which could regulate the potential contribution of plant roots to the soil organic matter pool. To understand the linkage between traditional macro-elemental and morphological traits of roots and their molecular-level carbon chemistry, we analyzed seasonal variations in monomeric yields of the free, bound, and lignin phenols in fine roots (distal five orders) and leaves of Ardisia quinquegona. Fine roots contained two-fold higher concentrations of bound phenols and three-fold higher concentrations of lignin phenols than leaves. Within fine roots, the concentrations of free and bound phenols decreased with increasing root order, and seasonal variation in the phenolic profile was more evident in lower order than in higher order roots. The morphological and macro-elemental root traits were decoupled from the quantity, composition and tissue association of phenolic compounds, revealing the potential inability of these traditional parameters to capture the molecular identity of phenolic carbon within the fine-root architecture and between fine roots and leaves. Our results highlight the molecular-level heterogeneity in phenolic carbon composition within the fine-root architecture, and imply that traits that capture the molecular identity of the root construct might better predict the decomposition dynamics within fine-root orders. PMID:25858344

  10. [Response of fine root decomposition to simulated nitrogen deposition in Pleioblastus amarus plantation, rainy area of West China].

    PubMed

    Tu, Li-Hua; Chen, Gang; Peng, Yong; Hu, Hong-Ling; Hu, Ting-Xing; Zhang, Jian

    2014-08-01

    As an important contributor to carbon (C) flux in the global C cycle, fine root litter decomposition in forests has the potential to be affected by the elevated nitrogen (N) deposition observed globally. From November 2007 to January 2013, a field experiment involving monthly simulated deposition of N in a Pleioblastus amarus plantation was conducted in the Rainy Area of West China. Four levels of nitrogen deposition were included as control (0 g N x m(-2) x a(-1)), low nitrogen (5 g N x m(-2) x a(-1)), medium nitrogen (15 g N x m(-2) x a(-1)) and high nitrogen (30 g N x m(-2) x a(-1)). After 3 years of simulated N deposition experiment (January 2011) , a two-year fine root decomposition experiment was conducted in the simulated N deposition plots using litterbag method, under monthly experimental N deposition. The decomposition rates of fine roots were fast first and then slow. Mass loss of fine roots in the first year of decomposition was up to 60%, and the change of the remaining mass was very slow in the second year. The time of 50% and 95% mass loss of fine roots was 1.20 and 5.17 years, respectively, under the conditions of no addition N input. In general, decomposition rates were underestimated using negative exponential model. Simulated N deposition significantly inhibited the decomposition of fine roots. The remaining mass in the high nitrogen treatment was 51.0% higher than that in the control, after two years of decomposition. Simulated N deposition increased C, P and K contents in the remaining mass of litter. Compared with the control, soil pH decreased significantly in the medium and high nitrogen treatments, soil organic C, total N, ammonium and nitrate contents and fine root biomass of P. amarus increased significantly in the high nitrogen treatment after simulated N deposition for 4. 5 years. Key words: nitrogen deposition; fine root decomposition; Pleioblastus amarus.

  11. Plant Root Growth In Granular Media

    NASA Astrophysics Data System (ADS)

    Wendell, Dawn; Hosoi, Peko

    2010-03-01

    Roots grow in a variety of granular substrates. However, the substrates are often treated in ways which minimize or neglect the inhomogeneities arising from the influence of inter-particle forces. Experiments are often run using gels or average stress measurements. This presentation discusses the effect of the local structure of the particulate environment on the root's direction. Using photoelastic particles and particles with a variety of Young's Moduli, we investigate the influence of inter-particle forces and particle stiffness on a pinto bean root's ability to grow through a fully-saturated granular medium. The level of particle contact force through which the roots successfully grow is determined and the influence of particle stiffness on root direction is investigated.

  12. Use of Stored Carbon Reserves in Growth of Temperate Tree Roots and Leaf Buds: Analyses Using Radiocarbon Measurements and Modeling

    SciTech Connect

    Gaudinski, Julia B.; Torn, Margaret S.; Riley, W. J.; Swanston, Christopher W.; Trumbore, Susan E.; JoslinJr., John D.; Majdi, H; Dawson, Todd E.; Hanson, Paul J

    2009-01-01

    Characterizing the use of C reserves in trees is important for understanding stress responses, impacts of asynchrony between photosynthesis and growth demand, and isotopic exchanges in plant dynamic studies. Using an inadvertent, whole ecosystem radiocarbon (14C) exposure in a temperate deciduous oak forest and numerical modeling, we calculated that the mean age of stored C used to grow leaf buds and new fine root tissue is 0.5-1.0 y. The mean age of stored C used to grow new roots was about 0.7 y across a range of realistic values of 14C inputs to the system. The amount of stored C used on an annual basis to grow fine roots was between 15 and 55% of total root growth, with the range defined by the assumed 14C input profile. We estimate the annually-averaged mean age of C in new root tissues is 1-5 months. Therefore, accounting for storage C use in isotope root models may be unnecessary in all but the fastest cycling root populations (i.e., mean age <1 y). Consistent with the whole ecosystem labeling results, we found, using "bomb-14C," that the mean C age of new root tissues in three additional forest sites (one deciduous, two coniferous) was less than 2 years. We conclude that in many ecosystem types, growth from stored C is insufficient to impact bomb-14C based estimates of long root lifetimes.

  13. Effects of elevated CO2 on fine root dynamics in a Mojave Desert community: A FACE study

    USGS Publications Warehouse

    Phillips, D.L.; Johnson, M.G.; Tingey, D.T.; Catricala, C.E.; Hoyman, T.L.; Nowak, R.S.

    2006-01-01

    Fine roots (??? 1mm diameter) are critical in plant water and nutrient absorption, and it is important to understand how rising atmospheric CO2 will affect them as part of terrestrial ecosystem responses to global change. This study's objective was to determine effects of elevated CO2 on production, mortality, and standing crops of fine root length over 2 years in a free-air CO2 enrichment (FACE) facility in the Mojave Desert of southern Nevada, USA. Three replicate 25m diameter FACE rings were maintained at ambient (??? 370 ??mol mol-1) and elevated CO2 (??? 550 ??mol mol-1) atmospheric concentrations. Twenty-eight minirhizotron tubes were placed in each ring to sample three microsite locations: evergreen Larrea shrubs, drought-deciduous Ambrosia shrubs, and along systematic community transects (primarily in shrub interspaces which account for ??? 85% of the area). Seasonal dynamics were similar for ambient and elevated CO2: fine root production peaked in April-June, with peak standing crop occurring about 1 month later, and peak mortality occurring during the hot summer months, with higher values for all three measures in a wet year compared with a dry year. Fine root standing crop, production, and mortality were not significantly different between treatments except standing crop along community transects, where fine root length was significantly lower in elevated CO2. Fine root turnover (annual cumulative mortality/mean standing crop) ranged from 2.33 to 3.17 year-1, and was not significantly different among CO2 treatments, except for community transect tubes where it was significantly lower for elevated CO2. There were no differences in fine root responses to CO2 between evergreen (Larrea) and drought-deciduous (Ambrosia) shrubs. Combined with observations of increased leaf-level water-use efficiency and lack of soil moisture differences, these results suggest that under elevated CO2 conditions, reduced root systems (compared with ambient CO2) appear sufficient

  14. Combining stable isotope and carbohydrate analyses in phloem sap and fine roots to study seasonal changes of source-sink relationships in a Mediterranean beech forest.

    PubMed

    Scartazza, Andrea; Moscatello, Stefano; Matteucci, Giorgio; Battistelli, Alberto; Brugnoli, Enrico

    2015-08-01

    Carbon isotope composition (δ(13)C) and carbohydrate content of phloem sap and fine roots were measured in a Mediterranean beech (Fagus sylvatica L.) forest throughout the growing season to study seasonal changes of source-sink relationships. Seasonal variations of δ(13)C and content of phloem sap sugars, collected during the daylight period, reflected the changes in soil and plant water status. The correlation between δ(13)C and content of phloem sap sugars, collected from plants belonging to different social classes, was significantly positive only during the driest month of July. In this month, δ(13)C of phloem sap sugars was inversely related to the increment of trunk radial growth and positively related to δ(13)C of fine roots. We conclude that the relationship between δ(13)C and the amount of phloem sap sugars is affected by a combination of causes, such as sink strength, tree social class, changes in phloem anatomy and transport capacity, and phloem loading of sugars to restore sieve tube turgor following the reduced plant water potential under drought conditions. However, δ(13)C and sugar composition of fine roots suggested that phloem transport of leaf sucrose to this belowground component was not impaired by mild drought and that sucrose was in a large part allocated towards fine roots in July, depending on tree social class. Hence, fine roots could represent a functional carbon sink during the dry seasonal periods, when transport and use of assimilates in other sink tissues are reduced. These results indicate a strict link between above- and belowground processes and highlight a rapid response of this Mediterranean forest to changes in environmental drivers to regulate source-sink relationships and carbon sink capacity.

  15. 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.

  16. Jatropha curcas L. Root Structure and Growth in Diverse Soils

    PubMed Central

    Valdés-Rodríguez, Ofelia Andrea; Sánchez-Sánchez, Odilón; Pérez-Vázquez, Arturo; Caplan, Joshua S.; Danjon, Frédéric

    2013-01-01

    Unlike most biofuel species, Jatropha curcas has promise for use in marginal lands, but it may serve an additional role by stabilizing soils. We evaluated the growth and structural responsiveness of young J. curcas plants to diverse soil conditions. Soils included a sand, a sandy-loam, and a clay-loam from eastern Mexico. Growth and structural parameters were analyzed for shoots and roots, although the focus was the plasticity of the primary root system architecture (the taproot and four lateral roots). The sandy soil reduced the growth of both shoot and root systems significantly more than sandy-loam or clay-loam soils; there was particularly high plasticity in root and shoot thickness, as well as shoot length. However, the architecture of the primary root system did not vary with soil type; the departure of the primary root system from an index of perfect symmetry was 14 ± 5% (mean ± standard deviation). Although J. curcas developed more extensively in the sandy-loam and clay-loam soils than in sandy soil, it maintained a consistent root to shoot ratio and root system architecture across all types of soil. This strong genetic determination would make the species useful for soil stabilization purposes, even while being cultivated primarily for seed oil. PMID:23844412

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

    PubMed

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

    2016-06-01

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

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

    PubMed

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

    2016-06-01

    Roots interact with soil properties and irrigation water quality leading to changes in root growth, structure and function. We studied these interactions in an orchard and in lysimeters with clay and sandy loam soils. Minirhizotron imaging and manual sampling showed that root growth was three times lower in the clay relative to sandy loam soil. Treated wastewater (TWW) led to a large reduction in root growth with clay (45-55%) but not with sandy loam soil (<20%). Treated wastewater increased salt uptake, membrane leakage and proline content, and decreased root viability, carbohydrate content and osmotic potentials in the fine roots, especially in clay. These results provide evidence that TWW challenges and damages the root system. The phenology and physiology of root orders were studied in lysimeters. Soil type influenced diameter, specific root area, tissue density and cortex area similarly in all root orders, while TWW influenced these only in clay soil. Respiration rates were similar in both soils, and root hydraulic conductivity was severely reduced in clay soil. Treated wastewater increased respiration rate and reduced hydraulic conductivity of all root orders in clay but only of the lower root orders in sandy loam soil. Loss of hydraulic conductivity increased with root order in clay and clay irrigated with TWW. Respiration and hydraulic properties of all root orders were significantly affected by sodium-amended TWW in sandy loam soil. These changes in root order morphology, anatomy, physiology and hydraulic properties indicate rapid and major modifications of root systems in response to differences in soil type and water quality. PMID:27022106

  19. Biomass and morphology of fine roots in temperate broad-leaved forests differing in tree species diversity: is there evidence of below-ground overyielding?

    PubMed

    Meinen, Catharina; Hertel, Dietrich; Leuschner, Christoph

    2009-08-01

    Biodiversity effects on ecosystem functioning in forests have only recently attracted increasing attention. The vast majority of studies in forests have focused on above-ground responses to differences in tree species diversity, while systematic analyses of the effects of biodiversity on root systems are virtually non-existent. By investigating the fine root systems in 12 temperate deciduous forest stands in Central Europe, we tested the hypotheses that (1) stand fine root biomass increases with tree diversity, and (2) 'below-ground overyielding' of species-rich stands in terms of fine root biomass is the consequence of spatial niche segregation of the roots of different species. The selected stands represent a gradient in tree species diversity on similar bedrock from almost pure beech forests to medium-diverse forests built by beech, ash, and lime, and highly-diverse stands dominated by beech, ash, lime, maple, and hornbeam. We investigated fine root biomass and necromass at 24 profiles per stand and analyzed species differences in fine root morphology by microscopic analysis. Fine root biomass ranged from 440 to 480 g m(-2) in the species-poor to species-rich stands, with 63-77% being concentrated in the upper 20 cm of the soil. In contradiction to our two hypotheses, the differences in tree species diversity affected neither stand fine root biomass nor vertical root distribution patterns. Fine root morphology showed marked distinctions between species, but these root morphological differences did not lead to significant differences in fine root surface area or root tip number on a stand area basis. Moreover, differences in species composition of the stands did not alter fine root morphology of the species. We conclude that 'below-ground overyielding' in terms of fine root biomass does not occur in the species-rich stands, which is most likely caused by the absence of significant spatial segregation of the root systems of these late-successional species.

  20. Arabidopsis thaliana root growth kinetics and lunisolar tidal acceleration.

    PubMed

    Fisahn, Joachim; Yazdanbakhsh, Nima; Klingele, Emile; Barlow, Peter

    2012-07-01

    • All living organisms on Earth are continually exposed to diurnal variations in the gravitational tidal force due to the Sun and Moon. • Elongation of primary roots of Arabidopsis thaliana seedlings maintained at a constant temperature was monitored for periods of up to 14 d using high temporal- and spatial-resolution video imaging. The time-course of the half-hourly elongation rates exhibited an oscillation which was maintained when the roots were placed in the free-running condition of continuous illumination. • Correlation between the root growth kinetics collected from seedlings initially raised under several light protocols but whose roots were subsequently in the free-running condition and the lunisolar tidal profiles enabled us to identify that the latter is the probable exogenous determinant of the rhythmic variation in root elongation rate. Similar observations and correlations using roots of Arabidopsis starch mutants suggest a central function of starch metabolism in the response to the lunisolar tide. The periodicity of the lunisolar tidal signal and the concomitant adjustments in root growth rate indicate that an exogenous timer exists for the modulation of root growth and development. • We propose that, in addition to the sensitivity to Earthly 1G gravity, which is inherent to all animals and plants, there is another type of responsiveness which is attuned to the natural diurnal variations of the lunisolar tidal force. PMID:22583121

  1. Arabidopsis thaliana root growth kinetics and lunisolar tidal acceleration.

    PubMed

    Fisahn, Joachim; Yazdanbakhsh, Nima; Klingele, Emile; Barlow, Peter

    2012-07-01

    • All living organisms on Earth are continually exposed to diurnal variations in the gravitational tidal force due to the Sun and Moon. • Elongation of primary roots of Arabidopsis thaliana seedlings maintained at a constant temperature was monitored for periods of up to 14 d using high temporal- and spatial-resolution video imaging. The time-course of the half-hourly elongation rates exhibited an oscillation which was maintained when the roots were placed in the free-running condition of continuous illumination. • Correlation between the root growth kinetics collected from seedlings initially raised under several light protocols but whose roots were subsequently in the free-running condition and the lunisolar tidal profiles enabled us to identify that the latter is the probable exogenous determinant of the rhythmic variation in root elongation rate. Similar observations and correlations using roots of Arabidopsis starch mutants suggest a central function of starch metabolism in the response to the lunisolar tide. The periodicity of the lunisolar tidal signal and the concomitant adjustments in root growth rate indicate that an exogenous timer exists for the modulation of root growth and development. • We propose that, in addition to the sensitivity to Earthly 1G gravity, which is inherent to all animals and plants, there is another type of responsiveness which is attuned to the natural diurnal variations of the lunisolar tidal force.

  2. Root growth and development in response to CO2 enrichment

    NASA Technical Reports Server (NTRS)

    Day, Frank P., Jr.

    1994-01-01

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

  3. Growth and development of the root apical meristem.

    PubMed

    Perilli, Serena; Di Mambro, Riccardo; Sabatini, Sabrina

    2012-02-01

    A key question in plant developmental biology is how cell division and cell differentiation are balanced to modulate organ growth and shape organ size. In recent years, several advances have been made in understanding how this balance is achieved during root development. In the Arabidopsis root meristem, stem cells in the apical region of the meristem self-renew and produce daughter cells that differentiate in the distal meristem transition zone. Several factors have been implicated in controlling the different functional zones of the root meristem to modulate root growth; among these, plant hormones have been shown to play a main role. In this review, we summarize recent findings regarding the role of hormone signaling and transcriptional networks in regulating root development.

  4. Modelling of root growth and bending in two dimensions.

    PubMed

    Zieschang, H E; Brain, P; Barlow, P W

    1997-02-01

    A special co-ordinate system is developed for modelling the gravitropic bending of plant roots. It is based on the Local Theory of Curves in differential geometry and describes, in one dimension, growth events that may actually occur in two, or even three, dimensions. With knowledge of the spatial distributions of relative elemental growth rates (RELELs) for the upper and lower flanks of a gravistimulated root, and also their temporal dependencies, it is possible to compute the development of curvature along the root and hence describe the time-course of gravitropic bending. In addition, the RELEL distributions give information about the velocity field and the basipetal displacement of points along the root's surface. According to the Fundamental Theorem of Local Curve Theory, the x and y co-ordinates of the root in its bending plane are then determined from the associated values of local curvature and local velocity. With the aid of this model, possible mathematical growth functions that correspond to biological mechanisms involved in differential growth can be tested. Hence, the model can help not only to distinguish the role of various physiological or biophysical parameters in the bending process, but also to validate hypotheses that make assumptions concerning their relative importance. However, since the model is constructed at the level of the organ and treats the root as a fluid continuum, none of the parameters relate to cellular behaviour; the parameters must instead necessarily apply to properties that impinge on the behaviour of the external boundary of the root. PMID:11536796

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

    PubMed

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

    2015-03-01

    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.

  7. Radial force development during root growth measured by photoelasticity

    NASA Astrophysics Data System (ADS)

    Kolb, Evelyne; Hartmann, Christian; Genet, Patricia

    2012-02-01

    The mechanical and topological properties of a soil like the global porosity and the distribution of void sizes greatly affect the development of a plant root, which in turn affects the shoot development. In particular, plant roots growing in heterogeneous medium like sandy soils or cracked substrates have to adapt their morphology and exert radial forces depending on the pore size in which they penetrate. We propose a model experiment in which a pivot root (chick-pea seeds) of millimetric diameter has to grow in a size-controlled gap δ (δ ranging 0.5-2.3 mm) between two photoelastic grains. By time-lapse imaging, we continuously monitored the root growth and the development of optical fringes in the photoelastic neighbouring grains when the root enters the gap. Thus we measured simultaneously and in situ the root morphological changes (length and diameter growth rates, circumnutation) as well as the radial forces the root exerts. Radial forces were increasing in relation with gap constriction and experiment duration but a levelling of the force was not observed, even after 5 days and for narrow gaps. The inferred mechanical stress was consistent with the turgor pressure of compressed cells. Therefore our set-up could be a basis for testing mechanical models of cellular growth.

  8. Physical effects of soil drying on roots and crop growth.

    PubMed

    Whitmore, Andrew P; Whalley, W Richard

    2009-01-01

    The nature and effect of the stresses on root growth in crops subject to drying is reviewed. Drought is a complex stress, impacting on plant growth in a number of interacting ways. In response, there are a number of ways in which the growing plant is able to adapt to or alleviate these stresses. It is suggested that the most significant opportunity for progress in overcoming drought stress and increasing crop yields is to understand and exploit the conditions in soil by which plant roots are able to maximize their use of resources. This may not be straightforward, with multiple stresses, sometimes competing functions of roots, and conditions which impact upon roots very differently depending upon what soil, what depth or what stage of growth the root is at. Several processes and the interaction between these processes in soil have been neglected. It is our view that drought is not a single, simple stress and that agronomic practice which seeks to adapt to climate change must take account of the multiple facets of both the stress induced by insufficient water as well as other interacting stresses such as heat, disease, soil strength, low nutrient status, and even hypoxia. The potential for adaptation is probably large, however. The possible changes in stress as a result of the climate change expected under UK conditions are assessed and it appears possible that wet warm winters will impact on root growth as much if not more than dry warm summers. PMID:19584120

  9. 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

    2013-01-01

    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.

  10. 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

  11. Synergistic growth effect among bacteria recovered from root canal infections

    PubMed Central

    Moreira Júnior, Gil; Ribeiro Sobrinho, Antônio Paulino; Bambirra, Bernardo Henrique Silva; Bambirra, Felipe Henrique Silva; Carvalho, Maria Auxiliadora Roque; Farias, Luiz Macedo; Nicoli, Jacques Robert; Moreira, Elizabeth Spangler

    2011-01-01

    The objective of this study was to determine the ecological relationships between bacterial species that colonize infected root canals. Root canal bacteria recovered from one patient with pulp canal necrosis were evaluated in vitro for synergistic and antagonistic activities determined by mono and co-culture growth kinetics and the production of bacteriocin-like substances using the double layer diffusion method. Peptostreptococcus prevotii triggered a significant increase of Fusobacterium nucleatum growth, while the former bacteria did not affect the growth of P. prevotii. The bacterial species did not produce antagonism activity against itself or against any of the other two species. Despite many studies have demonstrated the capability of root canal microorganisms to produce antagonistic substances, these in vitro experimental tests show the synergistic effect of P. prevotii on the growth of F. nucleatum. PMID:24031714

  12. Correlations between polyamine ratios and growth patterns in seedling roots

    NASA Technical Reports Server (NTRS)

    Shen, H. J.; Galston, A. W.

    1985-01-01

    The levels of putrescine, cadaverine, spermidine and spermine were determined in seedling roots of pea, tomato, millet and corn, as well as in corn coleoptiles and pea internodes. In all roots, putrescine content increased as elongation progressed, and the putrescine/spermine ratio closely paralleled the sigmoid growth curve up until the time of lateral root initiation. Spermidine and spermine were most abundant near the apices and declined progressively with increasing age of the cells. In the zone of differentiation of root hairs in pea roots, putrescine rose progressively with increasing age, while cadaverine declined. In both pea internodes and corn coleoptiles, the putrescine/spermidine ratio rises with increasing age and elongation. Thus, a block in the conversion of the diamine putrescine to the triamine spermidine may be an important step in the change from cell division to cell elongation.

  13. Mixing Eucalyptus and Acacia trees leads to fine root over-yielding and vertical segregation between species.

    PubMed

    Laclau, Jean-Paul; Nouvellon, Yann; Reine, Caroline; Gonçalves, José Leonardo de Moraes; Krushe, Alex Vladimir; Jourdan, Christophe; le Maire, Guerric; Bouillet, Jean-Pierre

    2013-07-01

    The consequences of diversity on belowground processes are still poorly known in tropical forests. The distributions of very fine roots (diameter <1 mm) and fine roots (diameter <3 mm) were studied in a randomized block design close to the harvest age of fast-growing plantations. A replacement series was set up in Brazil with mono-specific Eucalyptus grandis (100E) and Acacia mangium (100A) stands and a mixture with the same stocking density and 50% of each species (50A:50E). The total fine root (FR) biomass down to a depth of 2 m was about 27% higher in 50A:50E than in 100A and 100E. Fine root over-yielding in 50A:50E resulted from a 72 % rise in E. grandis fine root biomass per tree relative to 100E, whereas A. mangium FR biomass per tree was 17% lower than in 100A. Mixing A. mangium with E. grandis trees led to a drop in A. mangium FR biomass in the upper 50 cm of soil relative to 100A, partially balanced by a rise in deep soil layers. Our results highlight similarities in the effects of directional resources on leaf and FR distributions in the mixture, with A. mangium leaves below the E. grandis canopy and a low density of A. mangium fine roots in the resource-rich soil layers relative to monospecific stands. The vertical segregation of resource-absorbing organs did not lead to niche complementarity expected to increase the total biomass production. PMID:23180423

  14. Plasma membrane proteomics in the maize primary root growth zone: novel insights into root growth adaptation to water stress.

    PubMed

    Voothuluru, Priyamvada; Anderson, Jeffrey C; Sharp, Robert E; Peck, Scott C

    2016-09-01

    Previous work on maize (Zea mays L.) primary root growth under water stress showed that cell elongation is maintained in the apical region of the growth zone but progressively inhibited further from the apex. These responses involve spatially differential and coordinated regulation of osmotic adjustment, modification of cell wall extensibility, and other cellular growth processes that are required for root growth under water-stressed conditions. As the interface between the cytoplasm and the apoplast (including the cell wall), the plasma membrane likely plays critical roles in these responses. Using a simplified method for enrichment of plasma membrane proteins, the developmental distribution of plasma membrane proteins was analysed in the growth zone of well-watered and water-stressed maize primary roots. The results identified 432 proteins with differential abundances in well-watered and water-stressed roots. The majority of changes involved region-specific patterns of response, and the identities of the water stress-responsive proteins suggest involvement in diverse biological processes including modification of sugar and nutrient transport, ion homeostasis, lipid metabolism, and cell wall composition. Integration of the distinct, region-specific plasma membrane protein abundance patterns with results from previous physiological, transcriptomic and cell wall proteomic studies reveals novel insights into root growth adaptation to water stress.

  15. Plasma membrane proteomics in the maize primary root growth zone: novel insights into root growth adaptation to water stress.

    PubMed

    Voothuluru, Priyamvada; Anderson, Jeffrey C; Sharp, Robert E; Peck, Scott C

    2016-09-01

    Previous work on maize (Zea mays L.) primary root growth under water stress showed that cell elongation is maintained in the apical region of the growth zone but progressively inhibited further from the apex. These responses involve spatially differential and coordinated regulation of osmotic adjustment, modification of cell wall extensibility, and other cellular growth processes that are required for root growth under water-stressed conditions. As the interface between the cytoplasm and the apoplast (including the cell wall), the plasma membrane likely plays critical roles in these responses. Using a simplified method for enrichment of plasma membrane proteins, the developmental distribution of plasma membrane proteins was analysed in the growth zone of well-watered and water-stressed maize primary roots. The results identified 432 proteins with differential abundances in well-watered and water-stressed roots. The majority of changes involved region-specific patterns of response, and the identities of the water stress-responsive proteins suggest involvement in diverse biological processes including modification of sugar and nutrient transport, ion homeostasis, lipid metabolism, and cell wall composition. Integration of the distinct, region-specific plasma membrane protein abundance patterns with results from previous physiological, transcriptomic and cell wall proteomic studies reveals novel insights into root growth adaptation to water stress. PMID:27341663

  16. Impact of tapping and soil water status on fine root dynamics in a rubber tree plantation in Thailand

    PubMed Central

    Chairungsee, Naruenat; Gay, Frederic; Thaler, Philippe; Kasemsap, Poonpipope; Thanisawanyangkura, Sornprach; Chantuma, Arak; Jourdan, Christophe

    2013-01-01

    Fine roots (FR) play a major role in the water and nutrient uptake of plants and contribute significantly to the carbon and nutrient cycles of ecosystems through their annual production and turnover. FR growth dynamics were studied to understand the endogenous and exogenous factors driving these processes in a 14-year-old plantation of rubber trees located in eastern Thailand. FR dynamics were observed using field rhizotrons from October 2007 to October 2009. This period covered two complete dry seasons (November to March) and two complete rainy seasons (April to October), allowing us to study the effect of rainfall seasonality on FR dynamics. Rainfall and its distribution during the two successive years showed strong differences with 1500 and 950 mm in 2008 and 2009, respectively. FR production (FRP) completely stopped during the dry seasons and resumed quickly after the first rains. During the rainy seasons, FRP and the daily root elongation rate (RER) were highly variable and exhibited strong annual variations with a total FRP of 139.8 and 40.4 mm-2 and an average RER of 0.16 and 0.12 cm day-1 in 2008 and 2009, respectively. The significant positive correlations found between FRP, RER, the appearance of new roots, and rainfall at monthly intervals revealed the impact of rainfall seasonality on FR dynamics. However, the rainfall patterns failed to explain the weekly variations of FR dynamics observed particularly during the rainy seasons. At this time step, FRP, RER, and the appearance of new FR were negatively correlated to the average soil matric potential measured at a depth of between 30 and 60 cm. In addition, our study revealed a significant negative correlation between FR dynamics and the monthly production of dry rubber. Consequently, latex harvesting might disturb carbon dynamics in the whole tree, far beyond the trunk where the tapping was performed. These results exhibit the impact of climatic conditions and tapping system in the carbon budget of

  17. A novel bioassay using root re-growth in Lemna.

    PubMed

    Park, Areum; Kim, Youn-Jung; Choi, Eun-Mi; Brown, Murray T; Han, Taejun

    2013-09-15

    A new phytotoxicity test method based on root elongation of three Lemna species (Lemna gibba, L. minor, and L. paucicostata) has been developed. Tests with aquatic plants have, typically, favored measurements on fronds (e.g. frond number, area, biomass) rather than on roots, due, in part, to issues associated with handling fragile roots and the time-consuming procedures of selecting roots with identical root lengths. The present method differs in that roots were excised prior to exposure with subsequent measurements on newly developed roots. Results show that there were species-specific difference in sensitivity to the five metals tested (Ag, Cd, Cr, Cu and Hg), with Ag being the most toxic (EC50=5.3-37.6 μgL(-1)) to all three species, and Cr the least toxic for L. gibba and L. minor (1148.3 and 341.8 μgL(-1), respectively) and Cu for L. paucicostata (470.4 μgL(-1)). Direct comparisons were made with measurements of frond area, which were found to be less sensitive. More generally, root re-growth was shown to reflect the toxic responses of all three Lemna species to these five important metals. The root growth bioassay differs from three internationally standardized methods (ISO, OCED and US EPA) in that it is completed in 48 h, the required volume of test solutions is only 3 ml and non-axenic plants are used. Our results show that the Lemna root method is a simple, rapid, cost-effective, sensitive and precise bioassay to assess the toxic risks of metals and has practical application for monitoring municipal and industrial waste waters where metals are common constituents.

  18. A novel bioassay using root re-growth in Lemna.

    PubMed

    Park, Areum; Kim, Youn-Jung; Choi, Eun-Mi; Brown, Murray T; Han, Taejun

    2013-09-15

    A new phytotoxicity test method based on root elongation of three Lemna species (Lemna gibba, L. minor, and L. paucicostata) has been developed. Tests with aquatic plants have, typically, favored measurements on fronds (e.g. frond number, area, biomass) rather than on roots, due, in part, to issues associated with handling fragile roots and the time-consuming procedures of selecting roots with identical root lengths. The present method differs in that roots were excised prior to exposure with subsequent measurements on newly developed roots. Results show that there were species-specific difference in sensitivity to the five metals tested (Ag, Cd, Cr, Cu and Hg), with Ag being the most toxic (EC50=5.3-37.6 μgL(-1)) to all three species, and Cr the least toxic for L. gibba and L. minor (1148.3 and 341.8 μgL(-1), respectively) and Cu for L. paucicostata (470.4 μgL(-1)). Direct comparisons were made with measurements of frond area, which were found to be less sensitive. More generally, root re-growth was shown to reflect the toxic responses of all three Lemna species to these five important metals. The root growth bioassay differs from three internationally standardized methods (ISO, OCED and US EPA) in that it is completed in 48 h, the required volume of test solutions is only 3 ml and non-axenic plants are used. Our results show that the Lemna root method is a simple, rapid, cost-effective, sensitive and precise bioassay to assess the toxic risks of metals and has practical application for monitoring municipal and industrial waste waters where metals are common constituents. PMID:23917640

  19. Arabidopsis alcohol dehydrogenase expression in both shoots and roots is conditioned by root growth environment

    NASA Technical Reports Server (NTRS)

    Chung, H. J.; Ferl, R. J.

    1999-01-01

    It is widely accepted that the Arabidopsis Adh (alcohol dehydrogenase) gene is constitutively expressed at low levels in the roots of young plants grown on agar media, and that the expression level is greatly induced by anoxic or hypoxic stresses. We questioned whether the agar medium itself created an anaerobic environment for the roots upon their growing into the gel. beta-Glucuronidase (GUS) expression driven by the Adh promoter was examined by growing transgenic Arabidopsis plants in different growing systems. Whereas roots grown on horizontal-positioned plates showed high Adh/GUS expression levels, roots from vertical-positioned plates had no Adh/GUS expression. Additional results indicate that growth on vertical plates closely mimics the Adh/GUS expression observed for soil-grown seedlings, and that growth on horizontal plates results in induction of high Adh/GUS expression that is consistent with hypoxic or anoxic conditions within the agar of the root zone. Adh/GUS expression in the shoot apex is also highly induced by root penetration of the agar medium. This induction of Adh/GUS in shoot apex and roots is due, at least in part, to mechanisms involving Ca2+ signal transduction.

  20. Sampling open-top chambers and plantations for live fine-root biomass of loblolly pine. Forest Service research note

    SciTech Connect

    Zarnoch, S.J.; Marx, D.H.; Ruehle, J.L.; Baldwin, V.C.

    1993-09-08

    A soil-core sampling protocol was developed for estimating the standing crop of live fine-root biomass in young loblolly pines (Pinus taeda L.). Some of the pines were in ozone experiments in open-top chambers. Others were in young plantations. Attempts were made to find strata that would reduce the variability of estimates. With the pilot study estimates of variability, sampling designs were developed to meet specified criteria of precision. Estimates of fine-root biomass based on three soil-core sizes increased monotonically with core size.

  1. Auxin carrier and signaling dynamics during gravitropic root growth.

    PubMed

    Feraru, Mugurel I; Kleine-Vehn, Jürgen; Feraru, Elena

    2015-01-01

    Plant growth relates to gravity, ensuring that roots grow downwards into the soil and shoots expand aerially. The phytohormone auxin mediates tropistic growth responses, such as root gravitropism. Gravity perception in the very tip of the roots triggers carrier-dependent, asymmetric redistribution of auxin, leading to differential auxin responses and growth regulation at the upper and lower root flanks. This cellular, asymmetry-breaking event will eventually lead to root bending towards the gravity vector. Here, we show how to investigate auxin signaling and auxin carrier dynamics during root gravitropic response, using a chambered cover glass in combination with a confocal live cell imaging approach. To exemplify this method, we used established lines expressing transcriptional and translational green fluorescent protein (GFP) fusions to the auxin responsive promoter element DR5rev and the prominent auxin carrier PIN-FORMED2 (PIN2), respectively. Transgenic seedlings were placed and grown in the chambered cover glasses, enabling defined gravitropic stimulations prior to imaging. This method is optimal for inverted microscopes and significantly reduces stressful manipulations during specimen preparation.

  2. Tungsten disrupts root growth in Arabidopsis thaliana by PIN targeting.

    PubMed

    Adamakis, Ioannis-Dimosthenis S; Panteris, Emmanuel; Eleftheriou, Eleftherios P

    2014-08-15

    Tungsten is a heavy metal with increasing concern over its environmental impact. In plants it is extensively used to deplete nitric oxide by inhibiting nitrate reductase, but its presumed toxicity as a heavy metal has been less explored. Accordingly, its effects on Arabidopsis thaliana primary root were assessed. The effects on root growth, mitotic cell percentage, nitric oxide and hydrogen peroxide levels, the cytoskeleton, cell ultrastructure, auxin and cytokinin activity, and auxin carrier distribution were investigated. It was found that tungsten reduced root growth, particularly by inhibiting cell expansion in the elongation zone, so that root hairs emerged closer to the root tip than in the control. Although extensive vacuolation was observed, even in meristematic cells, cell organelles were almost unaffected and microtubules were not depolymerized but reoriented. Tungsten affected auxin and cytokinin activity, as visualized by the DR5-GFP and TCS-GFP expressing lines, respectively. Cytokinin fluctuations were similar to those of the mitotic cell percentage. DR5-GFP signal appeared ectopically expressed, while the signals of PIN2-GFP and PIN3-GFP were diminished even after relatively short exposures. The observed effects were not reminiscent of those of any nitric oxide scavengers. Taken together, inhibition of root growth by tungsten might rather be related to a presumed interference with the basipetal flow of auxin, specifically affecting cell expansion in the elongation zone.

  3. Root growth regulation and gravitropism in maize roots does not require the epidermis

    NASA Technical Reports Server (NTRS)

    Bjorkman, T.; Cleland, R. E.

    1991-01-01

    We have earlier published observations showing that endogenous alterations in growth rate during gravitropism in maize roots (Zea mays L.) are unaffected by the orientation of cuts which remove epidermal and cortical tissue in the growing zone (Bjorkman and Cleland, 1988, Planta 176, 513-518). We concluded that the epidermis and cortex are not essential for transporting a growth-regulating signal in gravitropism or straight growth, nor for regulating the rate of tissue expansion. This conclusion has been challenged by Yang et al. (1990, Planta 180, 530-536), who contend that a shallow girdle around the entire perimeter of the root blocks gravitropic curvature and that this inhibition is the result of a requirement for epidermal cells to transport the growth-regulating signal. In this paper we demonstrate that the entire epidermis can be removed without blocking gravitropic curvature and show that the position of narrow girdles does not affect the location of curvature. We therefore conclude that the epidermis is not required for transport of a growth-regulating substance from the root cap to the growing zone, nor does it regulate the growth rate of the elongating zone of roots.

  4. Control of root growth and development by reactive oxygen species.

    PubMed

    Tsukagoshi, Hironaka

    2016-02-01

    Reactive oxygen species (ROS) are relatively simple molecules that exist within cells growing in aerobic conditions. ROS were originally associated with oxidative stress and seen as highly reactive molecules that are injurious to many cell components. More recently, however, the function of ROS as signal molecules in many plant cellular processes has become more evident. One of the most important functions of ROS is their role as a plant growth regulator. For example, ROS are key molecules in regulating plant root development, and as such, are comparable to plant hormones. In this review, the molecular mechanisms of ROS that are mainly associated with plant root growth are discussed. The molecular links between root growth regulation by ROS and other signals will also be briefly discussed.

  5. Root growth studies of willow cuttings using Rhizoboxes

    NASA Astrophysics Data System (ADS)

    Omarova, Dinara; Lammeranner, Walter; Florineth, Florin

    2014-05-01

    Riparian forests (Tugay forests) in Central Asia (Kazakhstan) play a significant in soil protection. However, unadapted forest use leads to damage and loss of these fragile ecosystems. Willows have a crucial function in the ecosystem of these riparian forests. Willows facilitate the colonization with other important tree species and furthermore they protect the soil from wind and water erosion. To propagate willows and to estimate the beneficial effects of these plants it is important to know the root growth development. The research design is planned as model experiment with rhizoboxes. Rhizoboxes are non-invasive investigation methods which offer the possibility to survey the root system growth dynamics in time and space. A total of 33 rhizoboxes in size of 50cm x 75 cm x 5 cm will be constructed. The rhizoboxes will be tilted by 45 degrees using the gravitropism of the roots. The willow cuttings (Salix purpurea) will be planted in three different soil types. Each test series (growth period) will take three months. Investigated parameters will be root architecture, dynamic of root growth and above and below ground biomass allocation. Data will be drawn from photographic surveys which will be performed once a week. The contribution will present the methodology of these rhizobox investigations.

  6. 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.

  7. 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. PMID:25268503

  8. 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

  9. Response of the Fine Root Production, Phenology, and Turnover Rate of Six Shrub Species from a Subtropical Forest to a Soil Moisture Gradient and Shading

    NASA Astrophysics Data System (ADS)

    Fu, X.; Dai, X.; Wang, H.

    2015-12-01

    Knowledge of the fine root dynamics of different life forms in forest ecosystems is critical to understanding how the overall belowground carbon cycling is affected by climate change. However, our current knowledge regarding how endogenous or exogenous factors regulate the root dynamics of understory vegetation is limited. We selected a suite of study sites representing different habitats with gradients of soil moisture and solar radiation (shading or no shading). We assessed the fine root production phenology, the total fine root production, and the turnover among six understory shrub species in a subtropical climate, and examined the responses of the fine root dynamics to gradients in the soil moisture and solar radiation. The shrubs included three evergreen species, Loropetalum chinense, Vaccinium bracteatum, and Adinandra millettii, and three deciduous species, Serissa serissoides, Rubus corchorifolius, and Lespedeza davidii. We observed that variations in the annual fine root production and turnover among species were significant in the deciduous group but not in the evergreen group. Notably, V. bracteatum and S. serissoides presented the greatest responses in terms of root phenology to gradients in the soil moisture and shading: high-moisture habitat led to a decrease and shade led to an increase in fine root production during spring. Species with smaller fine roots of the 1st+2nd-order diameter presented more sensitive responses in terms of fine root phenology to a soil moisture gradient. Species with a higher fine root nitrogen-to -carbon ratio exhibited more sensitive responses in terms of fine root annual production to shading. Soil moisture and shading did not change the annual fine root production as much as the turnover rate. The fine root dynamics of some understory shrubs varied significantly with soil moisture and solar radiation status and may be different from tree species. Our results emphasize the need to study the understory fine root dynamics

  10. EFFECTS OF ELEVATED CO2 ON FINE ROOT DYNAMICS IN A MOJAVE DESERT COMMUNITY: A FACE STUDY

    EPA Science Inventory

    Fine roots ('1 mm diameter) are critical in plant water and nutrient absorption, and it is important to understand how rising atmospheric CO2 will affect them as part of terrestrial ecosystem responses to global change. This study's objective was to determine the effects of elev...

  11. CO2 AND N-FERTILIZATION EFFECTS ON FINE ROOT LENGTH, PRODUCTION, AND MORTALITY: A 4-YEAR PONDEROSA PINE STUDY

    EPA Science Inventory

    We conducted a 4-year study of Pinus ponderosa fine root (<2 mm) responses to atmospheric CO2 and N-fertilization. Seedlings were grown in open-top chambers at 3 CO2 levels (ambient, ambient+175 mol/mol, ambient+350 mol/mol) and 3 N-fertilization levels (0, 10, 20 g?m-2?yr-1). ...

  12. Fine root productivity varies along nitrogen and phosphorus gradients in high-rainfall mangrove forests of Micronesia

    USGS Publications Warehouse

    Cormier, Nicole; Twilley, Robert R.; Ewel, Katherine C.; Krauss, Ken W.

    2015-01-01

    Belowground biomass is thought to account for much of the total biomass in mangrove forests and may be related to soil fertility. The Yela River and the Sapwalap River, Federated States of Micronesia, contain a natural soil resource gradient defined by total phosphorus (P) density ranging from 0.05 to 0.42 mg cm−3 in different hydrogeomorphic settings. We used this fertility gradient to test the hypothesis that edaphic conditions constrain mangrove productivity through differential allocation of biomass to belowground roots. We removed sequential cores and implanted root ingrowth bags to measure in situ biomass and productivity, respectively. Belowground root biomass values ranged among sites from 0.448 ± 0.096 to 2.641 ± 0.534 kg m−2. Root productivity (roots ≤20 mm) did not vary significantly along the gradient (P = 0.3355) or with P fertilization after 6 months (P = 0.2968). Fine root productivity (roots ≤2 mm), however, did vary significantly among sites (P = 0.0363) and ranged from 45.88 ± 21.37 to 118.66 ± 38.05 g m−2 year−1. The distribution of total standing root biomass and fine root productivity followed patterns of N:P ratios as hypothesized, with larger root mass generally associated with lower relative P concentrations. Many of the processes of nutrient acquisition reported from nutrient-limited mangrove forests may also occur in forests of greater biomass and productivity when growing along soil nutrient gradients.

  13. Cinnamic acid increases lignin production and inhibits soybean root growth.

    PubMed

    Salvador, Victor Hugo; Lima, Rogério Barbosa; dos Santos, Wanderley Dantas; Soares, Anderson Ricardo; Böhm, Paulo Alfredo Feitoza; Marchiosi, Rogério; Ferrarese, Maria de Lourdes Lucio; Ferrarese-Filho, Osvaldo

    2013-01-01

    Cinnamic acid is a known allelochemical that affects seed germination and plant root growth and therefore influences several metabolic processes. In the present work, we evaluated its effects on growth, indole-3-acetic acid (IAA) oxidase and cinnamate 4-hydroxylase (C4H) activities and lignin monomer composition in soybean (Glycine max) roots. The results revealed that exogenously applied cinnamic acid inhibited root growth and increased IAA oxidase and C4H activities. The allelochemical increased the total lignin content, thus altering the sum and ratios of the p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) lignin monomers. When applied alone or with cinnamic acid, piperonylic acid (PIP, a quasi-irreversible inhibitor of C4H) reduced C4H activity, lignin and the H, G, S monomer content compared to the cinnamic acid treatment. Taken together, these results indicate that exogenously applied cinnamic acid can be channeled into the phenylpropanoid pathway via the C4H reaction, resulting in an increase in H lignin. In conjunction with enhanced IAA oxidase activity, these metabolic responses lead to the stiffening of the cell wall and are followed by a reduction in soybean root growth.

  14. Cinnamic acid increases lignin production and inhibits soybean root growth.

    PubMed

    Salvador, Victor Hugo; Lima, Rogério Barbosa; dos Santos, Wanderley Dantas; Soares, Anderson Ricardo; Böhm, Paulo Alfredo Feitoza; Marchiosi, Rogério; Ferrarese, Maria de Lourdes Lucio; Ferrarese-Filho, Osvaldo

    2013-01-01

    Cinnamic acid is a known allelochemical that affects seed germination and plant root growth and therefore influences several metabolic processes. In the present work, we evaluated its effects on growth, indole-3-acetic acid (IAA) oxidase and cinnamate 4-hydroxylase (C4H) activities and lignin monomer composition in soybean (Glycine max) roots. The results revealed that exogenously applied cinnamic acid inhibited root growth and increased IAA oxidase and C4H activities. The allelochemical increased the total lignin content, thus altering the sum and ratios of the p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) lignin monomers. When applied alone or with cinnamic acid, piperonylic acid (PIP, a quasi-irreversible inhibitor of C4H) reduced C4H activity, lignin and the H, G, S monomer content compared to the cinnamic acid treatment. Taken together, these results indicate that exogenously applied cinnamic acid can be channeled into the phenylpropanoid pathway via the C4H reaction, resulting in an increase in H lignin. In conjunction with enhanced IAA oxidase activity, these metabolic responses lead to the stiffening of the cell wall and are followed by a reduction in soybean root growth. PMID:23922685

  15. Abscisic acid inhibits root growth in Arabidopsis through ethylene biosynthesis.

    PubMed

    Luo, Xingju; Chen, Zhizhong; Gao, Junping; Gong, Zhizhong

    2014-07-01

    When first discovered in 1963, abscisic acid (ABA) was called abscisin II because it promotes abscission. Later, researchers found that ABA accelerates abscission via ethylene. In Arabidopsis, previous studies have shown that high concentrations of ABA inhibit root growth through ethylene signaling but not ethylene production. In the present study in Arabidopsis, we found that ABA inhibits root growth by promoting ethylene biosynthesis. The ethylene biosynthesis inhibitor L-α-(2-aminoethoxyvinyl)-glycine reduces ABA inhibition of root growth, and multiple mutants of ACS (1-aminocyclopropane-1-carboxylate synthase) are more resistant to ABA in terms of root growth than the wild-type is. Two ABA-activated calcium-dependent protein kinases, CPK4 and CPK11, phosphorylate the C-terminus of ACS6 and increase the stability of ACS6 in ethylene biosynthesis. Plants expressing an ACS6 mutant that mimics the phosphorylated form of ACS6 produce more ethylene than the wild-type. Our results reveal an important mechanism by which ABA promotes ethylene production. This mechanism may be highly conserved among higher plants.

  16. ASSESSING THE EFFECTS OF ELEVATED ATMOSP;HERIC CO2 AND TEMPERATURE ON FINE ROOT PRODUCTION AND MORTALITY IN FORESTED SYSTEMS

    EPA Science Inventory

    Little is known about the effects of global climate change on the production and mortality of fine roots. To better understand these processes we have conducted a number of studies to investigate the factors that influence the production and mortality of fine roots in coniferous...

  17. Fine-root carbon and nitrogen concentration of European beech (Fagus sylvatica L.) in Italy Prealps: possible implications of coppice conversion to high forest.

    PubMed

    Terzaghi, Mattia; Montagnoli, Antonio; Di Iorio, Antonino; Scippa, Gabriella S; Chiatante, Donato

    2013-01-01

    Fine-root systems represent a very sensitive plant compartment to environmental changes. Gaining further knowledge about their dynamics would improve soil carbon input understanding. This paper investigates C and N concentrations in fine roots in relation to different stand characteristics resulting from conversion of coppiced forests to high forests. In order to evaluate possible interferences due to different vegetative stages of vegetation, fine-root sampling was repeated six times in each stand during the same 2008 growing season. Fine-root sampling was conducted within three different soil depths (0-10; 10-20; and 20-30 cm). Fine-root traits were measured by means of WinRHIZO software which enable us to separate them into three different diameter classes (0-0.5, 0.5-1.0 and 1.0-2.0 mm). The data collected indicate that N concentration was higher in converted stands than in the coppiced stand whereas C concentration was higher in the coppiced stand than in converted stands. Consequently the fine-root C:N ratio was significantly higher in coppiced than in converted stands and showed an inverse relationship with fine-root turnover rate, confirming a significant change of fine-root status after the conversion of a coppice to high forest.

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

    PubMed

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

    2015-09-01

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

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

    PubMed

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

    2015-09-01

    Flavonoids are a class of distinct compounds produced by plant secondary metabolism that inhibit or promote plant development and have a relationship with auxin transport. We showed that, in terms of root development, Copaifera langsdorffii leaf extracts has an inhibitory effect on most flavonoid components compared with the application of exogenous flavonoids (glycosides and aglycones). These compounds alter the pattern of expression of the SHORT-ROOT and HD-ZIP III transcription factor gene family and cause morpho-physiological alterations in sorghum roots. In addition, to examine the flavonoid auxin interaction in stress, we correlated the responses with the effects of exogenous application of auxin and an auxin transport inhibitor. The results show that exogenous flavonoids inhibit primary root growth and increase the development of lateral roots. Exogenous flavonoids also change the pattern of expression of specific genes associated with root tissue differentiation. These findings indicate that flavonoid glycosides can influence the polar transport of auxin, leading to stress responses that depend on auxin. PMID:26473454

  20. Effects of plant growth promoting rhizobacteria (PGPR) on rooting and root growth of kiwifruit (Actinidia deliciosa) stem cuttings.

    PubMed

    Erturk, Yasar; Ercisli, Sezai; Haznedar, Ayhan; Cakmakci, Ramazan

    2010-01-01

    The effects of plant growth promoting rhizobacteria (PGPR) on the rooting and root growth of semi-hardwood and hardwood kiwifruit stem cuttings were investigated. The PGPR used were Bacillus RC23, Paenibacillus polymyxa RC05, Bacillus subtilis OSU142, Bacillus RC03, Comamonas acidovorans RC41, Bacillus megaterium RC01 and Bacillus simplex RC19. All the bacteria showed indole-3-acetic acid (IAA) producing capacity. Among the PGPR used, the highest rooting ratios were obtained at 47.50% for semi-hardwood stem cuttings from Bacillus RC03 and Bacillus simplex RC19 treatments and 42.50% for hardwood stem cuttings from Bacillus RC03. As well, Comamonas acidovorans RC41 inoculations indicated higher value than control treatments. The results suggest that these PGPR can be used in organic nursery material production and point to the feasibility of synthetic auxin (IBA) replacement by organic management based on PGPR. PMID:21157636

  1. Effects of plant growth promoting rhizobacteria (PGPR) on rooting and root growth of kiwifruit (Actinidia deliciosa) stem cuttings.

    PubMed

    Erturk, Yasar; Ercisli, Sezai; Haznedar, Ayhan; Cakmakci, Ramazan

    2010-01-01

    The effects of plant growth promoting rhizobacteria (PGPR) on the rooting and root growth of semi-hardwood and hardwood kiwifruit stem cuttings were investigated. The PGPR used were Bacillus RC23, Paenibacillus polymyxa RC05, Bacillus subtilis OSU142, Bacillus RC03, Comamonas acidovorans RC41, Bacillus megaterium RC01 and Bacillus simplex RC19. All the bacteria showed indole-3-acetic acid (IAA) producing capacity. Among the PGPR used, the highest rooting ratios were obtained at 47.50% for semi-hardwood stem cuttings from Bacillus RC03 and Bacillus simplex RC19 treatments and 42.50% for hardwood stem cuttings from Bacillus RC03. As well, Comamonas acidovorans RC41 inoculations indicated higher value than control treatments. The results suggest that these PGPR can be used in organic nursery material production and point to the feasibility of synthetic auxin (IBA) replacement by organic management based on PGPR.

  2. Transient growth responses of the primary roots of Zea mays.

    PubMed

    List, A

    1969-03-01

    1. The technique of streak photography was modified to use seven parallel cameras, each focused on an individual root in a guide holding flowing nutrient. Streak photographs representing displacement of points on the longitudinal axis of the root were projected on the table of an image plane digitizer. The displacement data are collected on cards by an IBM 526 key punch and processed by an IBM 360-65 computer. All graphic data were plotted by an EAI line plotter having a resolution of 600 lines per inch. 2. Roots of corn held at a temperature of 25°, a pH of 5.6, with constant oxygen concentration and basic nutrient composition, were subjected to step changes in oxygen and auxin (3-indoleacetic acid, IAA) concentrations. When O2 was lowered the response of the root consisted of a large reduction in growth rate followed by a series of oscillations with a period of about 30-50 min. Step changes in IAA from 0-10(-8)M (or less) resulted in heavily dampened oscillatory responses as well as reduction in growth rate. 10(-7) M IAA, however, elicited the initial inhibition followed by full recovery of growth rate after a few hours. PMID:24504710

  3. The effect of increased air humidity on fine root and rhizome biomass and turnover of silver birch forest ecosystem - a FAHM study.

    NASA Astrophysics Data System (ADS)

    Ostonen, I.; Kupper, P.; Sõber, J.; Aosaar, J.; Varik, M.; Lõhmus, K.

    2012-04-01

    A facility for free air humidity manipulation (FAHM) was established to investigate the effect of increased air humidity on belowground biomass and turnover in silver birch (Betula pendula Roth.) forest ecosystems with respect to rising air humidity predicted for Northern Europe. Fine root and rhizomes are short-lived and recognized as the most important component contributing to below-ground C fluxes in forests. The FAHM system enables air relative humidity to be increased on average 7 units (%) over the ambient level during mist fumigation. The experimental site contains humidified (H) and control (C) plots; each plot contains sectors with diverse "forest" understory and early successional grasses. The trees were planted in 2006, humidification started in spring 2008, and soil cores to study fine root and rhizome biomass and turnover were taken in 2007, 2009 and 2010. In July 2009, total fine root and rhizome biomass was 8 tons per ha in C and 16 tons per ha in H plots. The roots of understory formed 86% in C and 93% H plots, respectively. Our preliminary data suggest that the increased humidity affected more the roots of understory plants: fine root and rhizome biomass and production increased approximately twice by increasing air humidity. However, the tendency was similar for fine root biomass and production of silver birch. Fine root turnover speeded up for both silver birch and understory roots in H plots. Hence, changes in air humidity can significantly affect forest carbon cycling.

  4. Root ethylene signalling is involved in Miscanthus sinensis growth promotion by the bacterial endophyte Herbaspirillum frisingense GSF30(T).

    PubMed

    Straub, Daniel; Yang, Huaiyu; Liu, Yan; Tsap, Tatsiana; Ludewig, Uwe

    2013-11-01

    The bacterial endophyte Herbaspirillum frisingense GSF30(T) is a colonizer of several grasses grown in temperate climates, including the highly nitrogen-efficient perennial energy grass Miscanthus. Inoculation of Miscanthus sinensis seedlings with H. frisingense promoted root and shoot growth but had only a minor impact on nutrient concentrations. The bacterium affected the root architecture and increased fine-root structures. Although H. frisingense has the genetic requirements to fix nitrogen, only minor changes in nitrogen concentrations were observed. Herbaspirillum agglomerates were identified primarily in the root apoplast but also in the shoots. The short-term (3h) and long-term (3 weeks) transcriptomic responses of the plant to bacterial inoculation revealed that H. frisingense induced rapid changes in plant hormone signalling, most prominent in jasmonate signalling. Ethylene signalling pathways were also affected and persisted after 3 weeks in the root. Growth stimulation of the root by the ethylene precursor 1-aminocyclopropane 1-carboxylic acid was dose dependent and was affected by H. frisingense inoculation. Minor changes in the proteome were identified after 3 weeks. This study suggests that H. frisingense improves plant growth by modulating plant hormone signalling pathways and provides a framework to understand the beneficial effects of diazotrophic plant-growth-promoting bacteria, such as H. frisingense, on the biomass grass Miscanthus.

  5. A Simple Technique for Recording Root and Shoot Growth in Plants.

    ERIC Educational Resources Information Center

    Murray, Philip J.; Bristow, Andrew W.

    1997-01-01

    Presents a simple method of recording root growth which can be used in schools. A slant board system was designed to facilitate access to roots to enable measurements to be made, essentially forcing the roots to grow in a two-dimensional form which allows each student to observe and record root growth over several weeks. (AIM)

  6. Impact of root growth and root hydraulic conductance on water availability of young walnut trees

    NASA Astrophysics Data System (ADS)

    Jerszurki, Daniela; Couvreur, Valentin; Hopmans, Jan W.; Silva, Lucas C. R.; Shackel, Kenneth A.; de Souza, Jorge L. M.

    2015-04-01

    Walnut (Juglans regia L.) is a tree species of high economic importance in the Central Valley of California. This crop has particularly high water requirements, which makes it highly dependent on irrigation. The context of decreasing water availability in the state calls for efficient water management practices, which requires improving our understanding of the relationship between water application and walnut water availability. In addition to the soil's hydraulic conductivity, two plant properties are thought to control the supply of water from the bulk soil to the canopy: (i) root distribution and (ii) plant hydraulic conductance. Even though these properties are clearly linked to crop water requirements, their quantitative relation remains unclear. The aim of this study is to quantitatively explain walnut water requirements under water deficit from continuous measurements of its water consumption, soil and stem water potential, root growth and root system hydraulic conductance. For that purpose, a greenhouse experiment was conducted for a two month period. Young walnut trees were planted in transparent cylindrical pots, equipped with: (i) rhizotron tubes, which allowed for non-invasive monitoring of root growth, (ii) pressure transducer tensiometers for soil water potential, (iii) psychrometers attached to non-transpiring leaves for stem water potential, and (iv) weighing scales for plant transpiration. Treatments consisted of different irrigation rates: 100%, 75% and 50% of potential crop evapotranspiration. Plant responses were compared to predictions from three simple process-based soil-plant-atmosphere models of water flow: (i) a hydraulic model of stomatal regulation based on stem water potential and vapor pressure deficit, (ii) a model of plant hydraulics predicting stem water potential from soil-root interfaces water potential, and (iii) a model of soil water depletion predicting the water potential drop between the bulk soil and soil-root interfaces

  7. Apical control, gravitropic signaling, and the growth of lateral roots in Arabidopsis

    NASA Astrophysics Data System (ADS)

    Mullen, Jack L.; Wolverton, Chris; Hangarter, Roger P.

    Most research on gravity responses in plants has focused on primary roots and shoots, which typically grow in a vertical orientation. However, the patterns of lateral organ growth, which generally have large effects on overall plant architecture, are such that the organs are typically not vertical. In lateral roots of Arabidopsis, growth is initially in a nearly horizontal orientation but changes to a near-vertical orientation as the lateral root develops. Although the non-vertical lateral roots are gravitropically competent, following gravitropic reorientation of seedlings, the lateral roots on the upper flank of the primary root have different growth patterns from those on the lower side of the primary root. The differences are in part dependent on reorientation of the primary root, suggesting that gravitropic signaling from the primary root also contributes to the control of lateral root growth. The hormone auxin appears to play a role in this signaling between the primary and lateral roots, as auxin transport inhibitors applied to the primary root affect lateral root growth. Also, lateral roots of pin3 mutants, which are impaired in polar auxin transport, have altered lateral root orientations. However, other signals from the primary root tip also play an important role in regulating lateral root growth.

  8. 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.

  9. High-throughput two-dimensional root system phenotyping platform facilitates genetic analysis of root growth and development.

    PubMed

    Clark, Randy T; Famoso, Adam N; Zhao, Keyan; Shaff, Jon E; Craft, Eric J; Bustamante, Carlos D; McCouch, Susan R; Aneshansley, Daniel J; Kochian, Leon V

    2013-02-01

    High-throughput phenotyping of root systems requires a combination of specialized techniques and adaptable plant growth, root imaging and software tools. A custom phenotyping platform was designed to capture images of whole root systems, and novel software tools were developed to process and analyse these images. The platform and its components are adaptable to a wide range root phenotyping studies using diverse growth systems (hydroponics, paper pouches, gel and soil) involving several plant species, including, but not limited to, rice, maize, sorghum, tomato and Arabidopsis. The RootReader2D software tool is free and publicly available and was designed with both user-guided and automated features that increase flexibility and enhance efficiency when measuring root growth traits from specific roots or entire root systems during large-scale phenotyping studies. To demonstrate the unique capabilities and high-throughput capacity of this phenotyping platform for studying root systems, genome-wide association studies on rice (Oryza sativa) and maize (Zea mays) root growth were performed and root traits related to aluminium (Al) tolerance were analysed on the parents of the maize nested association mapping (NAM) population.

  10. Differential responses of grapevine rootstocks to water stress are associated with adjustments in fine root hydraulic physiology and suberization.

    PubMed

    Barrios-Masias, F H; Knipfer, T; McElrone, A J

    2015-09-01

    Water deficits are known to alter fine root structure and function, but little is known about how these responses contribute to differences in drought resistance across grapevine rootstocks. The ways in which water deficit affects root anatomical and physiological characteristics were studied in two grapevine rootstocks considered as low-medium (101-14Mgt) and highly (110R) drought resistant. Rootstocks were grown under prolonged and repeated drying cycles or frequent watering ('dry' and 'wet' treatments, respectively), and the following parameters were evaluated: root osmotic and hydrostatic hydraulic conductivity (Lp os and Lp hyd, respectively), suberization, steady-state root pressure (P rs), sap exudation rates, sap osmotic potential, and exosmotic relaxation curves. For both rootstocks, the 'dry' treatment reduced fine root Lp, elicited earlier root suberization and higher sap osmotic potential, and generated greater P rs after rewatering, but the rootstocks responded differently under these conditions. Lp os, Lp hyd, and sap exudation rates were significantly higher in 110R than in 101-14Mgt, regardless of moisture treatment. Under 'dry' conditions, 110R maintained a similar Lp os and decreased the Lp hyd by 36% compared with 'wet' conditions, while both parameters were decreased by at least 50% for 101-14Mgt under 'dry' conditions. Interestingly, build-up of P rs in 110R was 34% lower on average than in 101-14Mgt, suggesting differences in the development of suberized apoplastic barriers between the rootstocks as visualized by analysis of suberization from fluorescence microscopy. Consistent with this pattern, 110R exhibited the greatest exosmotic Lp os (i.e. Lp os of water flowing from roots to the soil) as determined from relaxation curves under wet conditions, where backflow may have limited its capacity to generate positive xylem pressure. The traits studied here can be used in combination to provide new insights needed for screening drought resistance

  11. Differential responses of grapevine rootstocks to water stress are associated with adjustments in fine root hydraulic physiology and suberization

    PubMed Central

    Barrios-Masias, F.H.; Knipfer, T.; McElrone, A.J.

    2015-01-01

    Water deficits are known to alter fine root structure and function, but little is known about how these responses contribute to differences in drought resistance across grapevine rootstocks. The ways in which water deficit affects root anatomical and physiological characteristics were studied in two grapevine rootstocks considered as low–medium (101-14Mgt) and highly (110R) drought resistant. Rootstocks were grown under prolonged and repeated drying cycles or frequent watering (‘dry’ and ‘wet’ treatments, respectively), and the following parameters were evaluated: root osmotic and hydrostatic hydraulic conductivity (Lp os and Lp hyd, respectively), suberization, steady-state root pressure (P rs), sap exudation rates, sap osmotic potential, and exosmotic relaxation curves. For both rootstocks, the ‘dry’ treatment reduced fine root Lp, elicited earlier root suberization and higher sap osmotic potential, and generated greater P rs after rewatering, but the rootstocks responded differently under these conditions. Lp os, Lp hyd, and sap exudation rates were significantly higher in 110R than in 101-14Mgt, regardless of moisture treatment. Under ‘dry’ conditions, 110R maintained a similar Lp os and decreased the Lp hyd by 36% compared with ‘wet’ conditions, while both parameters were decreased by at least 50% for 101-14Mgt under ‘dry’ conditions. Interestingly, build-up of P rs in 110R was 34% lower on average than in 101-14Mgt, suggesting differences in the development of suberized apoplastic barriers between the rootstocks as visualized by analysis of suberization from fluorescence microscopy. Consistent with this pattern, 110R exhibited the greatest exosmotic Lp os (i.e. Lp os of water flowing from roots to the soil) as determined from relaxation curves under wet conditions, where backflow may have limited its capacity to generate positive xylem pressure. The traits studied here can be used in combination to provide new insights needed for

  12. Differential responses of grapevine rootstocks to water stress are associated with adjustments in fine root hydraulic physiology and suberization.

    PubMed

    Barrios-Masias, F H; Knipfer, T; McElrone, A J

    2015-09-01

    Water deficits are known to alter fine root structure and function, but little is known about how these responses contribute to differences in drought resistance across grapevine rootstocks. The ways in which water deficit affects root anatomical and physiological characteristics were studied in two grapevine rootstocks considered as low-medium (101-14Mgt) and highly (110R) drought resistant. Rootstocks were grown under prolonged and repeated drying cycles or frequent watering ('dry' and 'wet' treatments, respectively), and the following parameters were evaluated: root osmotic and hydrostatic hydraulic conductivity (Lp os and Lp hyd, respectively), suberization, steady-state root pressure (P rs), sap exudation rates, sap osmotic potential, and exosmotic relaxation curves. For both rootstocks, the 'dry' treatment reduced fine root Lp, elicited earlier root suberization and higher sap osmotic potential, and generated greater P rs after rewatering, but the rootstocks responded differently under these conditions. Lp os, Lp hyd, and sap exudation rates were significantly higher in 110R than in 101-14Mgt, regardless of moisture treatment. Under 'dry' conditions, 110R maintained a similar Lp os and decreased the Lp hyd by 36% compared with 'wet' conditions, while both parameters were decreased by at least 50% for 101-14Mgt under 'dry' conditions. Interestingly, build-up of P rs in 110R was 34% lower on average than in 101-14Mgt, suggesting differences in the development of suberized apoplastic barriers between the rootstocks as visualized by analysis of suberization from fluorescence microscopy. Consistent with this pattern, 110R exhibited the greatest exosmotic Lp os (i.e. Lp os of water flowing from roots to the soil) as determined from relaxation curves under wet conditions, where backflow may have limited its capacity to generate positive xylem pressure. The traits studied here can be used in combination to provide new insights needed for screening drought resistance

  13. Growth, biomass allocation and photosynthetic responses are related to intensity of root severance and soil moisture conditions in the plantation tree Cunninghamia lanceolata.

    PubMed

    Dong, Tingfa; Duan, Baoli; Zhang, Sheng; Korpelainen, Helena; Niinemets, Ülo; Li, Chunyang

    2016-07-01

    We employed the warm temperate conifer Cunninghamia lanceolata (Lamb.) Hook. as a model of plantation forest species to investigate ecophysiological responses to root treatments (control (0%), and ∼25, 50 or 75% of the initial root mass) under well-watered and water-limited conditions. Our results indicated that total root dry mass accumulation was negatively associated with the severity of root pruning, but there was evidence of multiple compensatory responses. The plants exhibited higher instantaneous and long-term (assessed by carbon isotope composition, δ(13)C) water-use efficiency in pruning treatments, especially under low water availability. Root pruning also increased the fine root/total root mass ratio, specific root length and fine root vitality in both water availability treatments. As a result of the compensatory responses, under well-watered conditions, height, stem dry mass accumulation, leaf/fine root biomass ratio (L/FR), transpiration rate, photosynthetic capacity and photosynthetic nitrogen-use efficiency (EN) were the highest under 25% pruning. Yet, all these traits except L/FR and foliage nitrogen content were severely reduced under 75% pruning. Drought negatively affected growth and leaf gas exchange rates, and there was a greater negative effect on growth, water potential, gas exchange and EN when >25% of total root biomass was removed. The stem/aboveground mass ratio was the highest under 25% pruning in both watering conditions. These results indicate that the responses to root severance are related to the excision intensity and soil moisture content. A moderate root pruning proved to be an effective means to improve stem dry mass accumulation. PMID:27122365

  14. Temporal and Spatial Profiling of Root Growth Revealed Novel Response of Maize Roots under Various Nitrogen Supplies in the Field

    PubMed Central

    Peng, Yunfeng; Li, Xuexian; Li, Chunjian

    2012-01-01

    A challenge for Chinese agriculture is to limit the overapplication of nitrogen (N) without reducing grain yield. Roots take up N and participate in N assimilation, facilitating dry matter accumulation in grains. However, little is known about how the root system in soil profile responds to various N supplies. In the present study, N uptake, temporal and spatial distributions of maize roots, and soil mineral N (Nmin) were thoroughly studied under field conditions in three consecutive years. The results showed that in spite of transient stimulation of growth of early initiated nodal roots, N deficiency completely suppressed growth of the later-initiated nodal roots and accelerated root death, causing an early decrease in the total root length at the rapid vegetative growth stage of maize plants. Early N excess, deficiency, or delayed N topdressing reduced plant N content, resulting in a significant decrease in dry matter accumulation and grain yield. Notably, N overapplication led to N leaching that stimulated root growth in the 40–50 cm soil layer. It was concluded that the temporal and spatial growth patterns of maize roots were controlled by shoot growth and local soil Nmin, respectively. Improving N management involves not only controlling the total amount of chemical N fertilizer applied, but also synchronizing crop N demand and soil N supply by split N applications. PMID:22624062

  15. Carbon Allocation into Different Fine-Root Classes of Young Abies alba Trees Is Affected More by Phenology than by Simulated Browsing

    PubMed Central

    Endrulat, Tina; Buchmann, Nina; Brunner, Ivano

    2016-01-01

    Abies alba (European silver fir) was used to investigate possible effects of simulated browsing on C allocation belowground by 13CO2 pulse-labelling at spring, summer or autumn, and by harvesting the trees at the same time point of the labelling or at a later season for biomass and for 13C-allocation into the fine-root system. Before budburst in spring, the leader shoots and 50% of all lateral shoots of half of the investigated 5-year old Abies alba saplings were clipped to simulate browsing. At harvest, different fine-root classes were separated, and starch as an important storage compartment was analysed for concentrations. The phenology had a strong effect on the allocation of the 13C-label from shoots to roots. In spring, shoots did not supply the fine-roots with high amounts of the 13C-label, because the fine-roots contained less than 1% of the applied 13C. In summer and autumn, however, shoots allocated relatively high amounts of the 13C-label to the fine roots. The incorporation of the 13C-label as structural C or as starch into the roots is strongly dependent on the root type and the root diameter. In newly formed fine roots, 3–5% of the applied 13C was incorporated, whereas 1–3% in the ≤0.5 mm root class and 1–1.5% in the >0.5–1.0 mm root class were recorded. Highest 13C-enrichment in the starch was recorded in the newly formed fine roots in autumn. The clipping treatment had a significant positive effect on the amount of allocated 13C-label to the fine roots after the spring labelling, with high relative 13C-contents observed in the ≤0.5 mm and the >0.5–1.0 mm fine-root classes of clipped trees. No effects of the clipping were observed after summer and autumn labelling in the 13C-allocation patterns. Overall, our data imply that the season of C assimilation and, thus, the phenology of trees is the main determinant of the C allocation from shoots to roots and is clearly more important than browsing. PMID:27123860

  16. Carbon Allocation into Different Fine-Root Classes of Young Abies alba Trees Is Affected More by Phenology than by Simulated Browsing.

    PubMed

    Endrulat, Tina; Buchmann, Nina; Brunner, Ivano

    2016-01-01

    Abies alba (European silver fir) was used to investigate possible effects of simulated browsing on C allocation belowground by 13CO2 pulse-labelling at spring, summer or autumn, and by harvesting the trees at the same time point of the labelling or at a later season for biomass and for 13C-allocation into the fine-root system. Before budburst in spring, the leader shoots and 50% of all lateral shoots of half of the investigated 5-year old Abies alba saplings were clipped to simulate browsing. At harvest, different fine-root classes were separated, and starch as an important storage compartment was analysed for concentrations. The phenology had a strong effect on the allocation of the 13C-label from shoots to roots. In spring, shoots did not supply the fine-roots with high amounts of the 13C-label, because the fine-roots contained less than 1% of the applied 13C. In summer and autumn, however, shoots allocated relatively high amounts of the 13C-label to the fine roots. The incorporation of the 13C-label as structural C or as starch into the roots is strongly dependent on the root type and the root diameter. In newly formed fine roots, 3-5% of the applied 13C was incorporated, whereas 1-3% in the ≤0.5 mm root class and 1-1.5% in the >0.5-1.0 mm root class were recorded. Highest 13C-enrichment in the starch was recorded in the newly formed fine roots in autumn. The clipping treatment had a significant positive effect on the amount of allocated 13C-label to the fine roots after the spring labelling, with high relative 13C-contents observed in the ≤0.5 mm and the >0.5-1.0 mm fine-root classes of clipped trees. No effects of the clipping were observed after summer and autumn labelling in the 13C-allocation patterns. Overall, our data imply that the season of C assimilation and, thus, the phenology of trees is the main determinant of the C allocation from shoots to roots and is clearly more important than browsing. PMID:27123860

  17. Analysis of cake growth in cake filtration: Effect of fine particle retention

    SciTech Connect

    Tien, C.; Bai, R.; Ramarao, B.V.

    1997-01-01

    Equations were derived that describe the dynamics of cake growth in cake filtration, and methods for their solutions were developed. In deriving the equations, the moving boundary nature of the cake formation process and the effect of fine particle retention were considered. It was shown that fine particle retention may contribute significantly to the decrease of cake permeability and thus alters the performance of cake filtration even if the amount of fine particles involved is small. Through numerical examples, it was also demonstrated that fine particle retention in filter cakes may cause serious errors in determining the constitutive relationships from filter test data.

  18. Growth in Turface® clay permits root hair phenotyping along the entire crown root in cereal crops and demonstrates that root hair growth can extend well beyond the root hair zone.

    PubMed

    Goron, Travis L; Watts, Sophia; Shearer, Charles; Raizada, Manish N

    2015-04-12

    In cereal crops, root hairs are reported to function within the root hair zone to carry out important roles in nutrient and water absorption. Nevertheless, these single cells remain understudied due to the practical challenges of phenotyping these delicate structures in large cereal crops growing on soil or other growth systems. Here we present an alternative growth system for examining the root hairs of cereal crops: the use of coarse Turface® clay alongside fertigation. This system allowed for root hairs to be easily visualized along the entire lengths of crown roots in three different cereal crops (maize, wheat, and finger millet). Surprisingly, we observed that the root hairs in these crops continued to grow beyond the canonical root hair zone, with the most root hair growth occurring on older crown root segments. We suggest that the Turface® fertigation system may permit a better understanding of the changing dynamics of root hairs as they age in large plants, and may facilitate new avenues for crop improvement below ground. However, the relevance of this system to field conditions must be further evaluated in other crops.

  19. [Effects of different irrigation patterns on the growth of maize root hair].

    PubMed

    Hu, Tian-Tian; Kang, Shao-Zhong; Yuan, Li-Na; Li, Zhi-Jun; Zhang, Fu-Cang

    2008-06-01

    With split-root pot experiment and using optical and electrical microscopes, the growth of root hair of maize under different irrigation patterns, i. e. , irrigated on both halves of the pot (conventional irrigation, CI), on one half only (fixed partial root zone irrigation, FPRI), and on both halves alternatively (alternate partial root zone irrigation, APRI), was observed. The observation after 40 days of treatment showed that in non-irrigated root zone of FPRI, the length proportion of root covered by vestigial root hairs was 20.96%, being higher than that in other zones. In addition to some bletting spots, the root system in irrigated zone of FPRI turned yellow, root-branching deteriorated to some extent, and the root hair density on the section with thick root hairs was lower than that in non-irrigated zone. However, both the length proportion of root covered by vestigial root hairs (15.72%) and the deterioration of root hair were lower than those in non-irrigated zone. As for CI, the root appearance and root hair growth were similar to those of the FPRI irrigated zone. As for the early and late irrigated root zones of APRI, the root hair density on the section with thick root hairs was high. The length proportion of root covered by vestigial root hairs was 9.77% and 10.38% for these two root zones, respectively, being lower than that in any root zones of FPRI and CI. It was suggested that alternative partial root zone irrigation was more beneficial to the growth of root hair than fixed partial root zone irrigation and conventional irrigation.

  20. Phytotoxicity of nanoparticles: inhibition of seed germination and root growth.

    PubMed

    Lin, Daohui; Xing, Baoshan

    2007-11-01

    Plants need to be included to develop a comprehensive toxicity profile for nanoparticles. Effects of five types of nanoparticles (multi-walled carbon nanotube, aluminum, alumina, zinc, and zinc oxide) on seed germination and root growth of six higher plant species (radish, rape, ryegrass, lettuce, corn, and cucumber) were investigated. Seed germination was not affected except for the inhibition of nanoscale zinc (nano-Zn) on ryegrass and zinc oxide (nano-ZnO) on corn at 2000 mg/L. Inhibition on root growth varied greatly among nanoparticles and plants. Suspensions of 2000 mg/L nano-Zn or nano-ZnO practically terminated root elongation of the tested plant species. Fifty percent inhibitory concentrations (IC50) of nano-Zn and nano-ZnO were estimated to be near 50mg/L for radish, and about 20mg/L for rape and ryegrass. The inhibition occurred during the seed incubation process rather than seed soaking stage. These results are significant in terms of use and disposal of engineered nanoparticles.

  1. Growth and physiology of olive pioneer and fibrous roots exposed to soil moisture deficits.

    PubMed

    Polverigiani, S; McCormack, M L; Mueller, C W; Eissenstat, D M

    2011-11-01

    In woody plants, pioneer roots are the main roots used to expand the root system horizontally and vertically whereas fibrous 'feeder' roots are chiefly used in the absorption of water and nutrients. Because of their different roles, we expected newly emerged pioneer and fibrous roots to respond differently to restrictions in soil moisture. We hypothesized that fibrous roots would exhibit greater growth plasticity and greater physiological impairment from soil moisture deficits, especially under heterogeneous conditions. We compared the responses of fibrous and pioneer roots of olive seedlings (Olea europaea) to localized and uniform soil moisture deficits in transparent containers in the greenhouse. In comparison with uniformly wet conditions, uniformly dry conditions caused reduced shoot photosynthesis and reduced shoot growth, but no significant effect on root morphology, root respiration (measured in aerated buffer solution using excised roots) or electrolyte leakage as a function of root age. Under heterogeneous soil moisture conditions, root growth tended to preferentially occur in the moist sector, especially in the pioneer roots. In comparison with pioneer roots in the moist sector, pioneer roots in the dry sector had higher tissue density and higher suberin content, but no shift in root respiration, non-structural carbohydrates or electrolyte leakage. In contrast, fibrous roots in the dry sector exhibited evidence of impaired physiology in older (>38 days) roots compared with similar age fibrous roots in the moist sector. While we anticipated that, compared with pioneer roots, fibrous roots would be more sensitive to soil moisture deficits as expressed by higher electrolyte leakage, we did not expect the strong growth plasticity of pioneer roots under heterogeneous soil moisture conditions. Differentiating the responses of these two very different root types can improve our understanding of how different portions of the root system of woody plants cope with

  2. CO2 enrichment increases carbon and nitrogen input from fine roots in a deciduous forest.

    SciTech Connect

    Iversen, Colleen M; Childs, Joanne; Norby, Richard J

    2008-08-01

    Greater root production under elevated [CO2] may drive changes in soil C storage and N cycling. However, this depends on root population turnover and chemistry, and the soil depth at which the roots are produced. We assessed the effect of elevated [CO2] on root biomass and N inputs at several soil depths using a long-term minirhizotron data set combined with continuous, root-specific measurements of root mass per unit length and [N]. Our experiment was conducted in a Liquidambar styraciflua forest stand exposed to current or elevated atmospheric [CO2] for 9 years. CO2-enrichment had no effect on root tissue density or [N] within a given diameter class. Root biomass production, standing crop and mortality were doubled under elevated [CO2]. Over 9 years, root mortality resulted in 681 g m-2 of extra C and 9 g m-2 of extra N input to the soil system under elevated [CO2]. At least half of these inputs were below 30 cm soil depth. Quantification of the effects of elevated CO2 on root detritus, especially at depth in the soil, will provide critical information needed for predicting processes such as long-term soil C storage and N cycling.

  3. Elevated atmospheric CO2 stimulates soil fungal diversity through increased fine root production in a semiarid shrubland ecosystem.

    PubMed

    Lipson, David A; Kuske, Cheryl R; Gallegos-Graves, La Verne; Oechel, Walter C

    2014-08-01

    Soil fungal communities are likely to be central in mediating microbial feedbacks to climate change through their effects on soil carbon (C) storage, nutrient cycling, and plant health. Plants often produce increased fine root biomass in response to elevated atmospheric carbon dioxide (CO2 ), but the responses of soil microbial communities are variable and uncertain, particularly in terms of species diversity. In this study, we describe the responses of the soil fungal community to free air CO2 enrichment (FACE) in a semiarid chaparral shrubland in Southern California (dominated by Adenomstoma fasciculatum) using large subunit rRNA gene sequencing. Community composition varied greatly over the landscape and responses to FACE were subtle, involving a few specific groups. Increased frequency of Sordariomycetes and Leotiomycetes, the latter including the Helotiales, a group that includes many dark septate endophytes known to associate positively with roots, was observed in the FACE plots. Fungal diversity, both in terms of richness and evenness, increased consistently in the FACE treatment, and was relatively high compared to other studies that used similar methods. Increases in diversity were observed across multiple phylogenetic levels, from genus to class, and were distributed broadly across fungal lineages. Diversity was also higher in samples collected close to (5 cm) plants compared to samples in canopy gaps (30 cm away from plants). Fungal biomass correlated well with soil organic matter (SOM) content, but patterns of diversity were correlated with fine root production rather than SOM. We conclude that the fungal community in this ecosystem is tightly linked to plant fine root production, and that future changes in the fungal community in response to elevated CO2 and other climatic changes will be primarily driven by changes in plant belowground allocation. Potential feedbacks mediated by soil fungi, such as soil C sequestration, nutrient cycling, and

  4. Tomato root growth, gravitropism, and lateral development: correlation with auxin transport

    NASA Technical Reports Server (NTRS)

    Muday, G. K.; Haworth, P.

    1994-01-01

    Tomato (Lycopersicon esculentum, Mill.) roots were analyzed during growth on agar plates. Growth of these roots was inhibited by the auxin transport inhibitors naphthylphthalamic acid (NPA) and semicarbazone derivative I (SCB-1). The effect of auxin transport inhibitors on root gravitropism was analyzed by measurement of the angle of gravitropic curvature after the roots were reoriented 90 degrees from the vertical. NPA and SCB-1 abolished both the response of these roots to gravity and the formation of lateral roots, with SCB-1 being the more effective at inhibition. Auxins also inhibited root growth. Both auxins tested has a slight effect on the gravity response, but this effect is probably indirect, since auxins reduced the growth rate. Auxins also stimulated lateral root growth at concentration where primary root growth was inhibited. When roots were treated with both IAA and NPA simultaneously, a cumulative inhibition of root growth was found. When both compounds were applied together, analysis of gravitropism and lateral root formation indicated that the dominant effect was exerted by auxin transport inhibitors. Together, these data suggest a model for the role of auxin transport in controlling both primary and lateral root growth.

  5. Water deficit during root development: effects on the growth of roots and osmotic water permeability of isolated root protoplasts.

    PubMed

    Morillon, Raphaël; Lassalles, Jean-Paul

    2002-01-01

    The effect of low water potentials on root growth of flax (Linum usitatissimum L. cv. Ariane), rape (Brassica napus L. de Candolle, cv. Bristol), hard wheat (Triticum turgidum L. cv. Cham1) and soft wheat (Triticum aestivum L. cv. Ritmo) was studied by measuring the osmotic water permeability (Pos) of root protoplasts and the protein abundance of PIP1 and PIP2 aquaporins. These different species require more or less water, the most sensitive to water deficit being flax and rape. Ritmo, is a cultivar of wheat adapted to temperate zones, while the other cultivar Cham1 is adapted to low-rainfall areas. The seedlings were germinated and grown in water, salt or sugar solutions at different water potentials. The values of Pos for flax, rape and Chaml wheat were normally distributed and could be characterized by mean +/- SD. Root protoplasts from water-grown seedlings had Pos values of 485+/-159 microm s(-1) (flax), 582+/-100 microm s(-1) (rape), and 6.3+/-3.5 microm s(-1) (Cham1). At the same age, the protoplasts from Ritmo exhibited a much wider range of values than the protoplasts of Cham1. When seedlings were grown under conditions of osmotic or salt stress, the mass of the roots was reduced for all species. With 0.25 mol kg(-1) sorbitol or 0.125 M NaCl, the Pos for flax, rape and Cham1 remained constant or slightly increased, while for Ritmo the reduction in the mass of the roots was paralleled by a reduction in Pos. Only Cham1 and Ritmo were able to germinate at a lower potential (0.5 mol kg(-1) sorbitol). For Ritmo the reduction in the mass of the roots was paralleled by a reduction in Pos when grown in this stress condition and both wheats exhibited low Pos values. The expression of the PIP1 and PIP2 aquaporins families was also studied by immunoblotting. We did not observe any difference in protein expression for any of the species, whatever the growing conditions. We suggest that the high Pos values for flax and rape could play a role in the sensitivity of these

  6. Suppression of Photosynthetic Gene Expression in Roots Is Required for Sustained Root Growth under Phosphate Deficiency1[W][OPEN

    PubMed Central

    Kang, Jun; Yu, Haopeng; Tian, Caihuan; Zhou, Wenkun; Li, Chuanyou; Jiao, Yuling; Liu, Dong

    2014-01-01

    Plants cope with inorganic phosphate (Pi) deficiencies in their environment by adjusting their developmental programs and metabolic activities. For Arabidopsis (Arabidopsis thaliana), the developmental responses include the inhibition of primary root growth and the enhanced formation of lateral roots and root hairs. Pi deficiency also inhibits photosynthesis by suppressing the expression of photosynthetic genes. Early studies showed that photosynthetic gene expression was also suppressed in Pi-deficient roots, a nonphotosynthetic organ; however, the biological relevance of this phenomenon remains unknown. In this work, we characterized an Arabidopsis mutant, hypersensitive to Pi starvation7 (hps7), that is hypersensitive to Pi deficiency; the hypersensitivity includes an increased inhibition of root growth. HPS7 encodes a tyrosylprotein sulfotransferase. Accumulation of HPS7 proteins in root tips is enhanced by Pi deficiency. Comparative RNA sequencing analyses indicated that the expression of many photosynthetic genes is activated in roots of hps7. Under Pi deficiency, the expression of photosynthetic genes in hps7 is further increased, which leads to enhanced accumulation of chlorophyll, starch, and sucrose. Pi-deficient hps7 roots also produce a high level of reactive oxygen species. Previous research showed that the overexpression of GOLDEN-like (GLK) transcription factors in transgenic Arabidopsis activates photosynthesis in roots. The GLK overexpressing (GLK OX) lines also exhibit increased inhibition of root growth under Pi deficiency. The increased inhibition of root growth in hps7 and GLK OX lines by Pi deficiency was completely reversed by growing the plants in the dark. Based on these results, we propose that suppression of photosynthetic gene expression is required for sustained root growth under Pi deficiency. PMID:24868033

  7. Identification of SHRUBBY, a SHORT-ROOT and SCARECROW interacting protein that controls root growth and radial patterning.

    PubMed

    Koizumi, Koji; Gallagher, Kimberly L

    2013-03-01

    The timing and extent of cell division is particularly important for the growth and development of multicellular organisms. Roots of the model organism Arabidopsis thaliana have been widely studied as a paradigm for organ development in plants. In the Arabidopsis root, the plant-specific GRAS family transcription factors SHORT-ROOT (SHR) and SCARECROW (SCR) are key regulators of root growth and of the asymmetric cell divisions that separate the ground tissue into two separate layers: the endodermis and cortex. To elucidate the role of SHR in root development, we identified 17 SHR-interacting proteins. Among those isolated was At5g24740, which we named SHRUBBY (SHBY). SHBY is a vacuolar sorting protein with similarity to the gene responsible for Cohen syndrome in humans. Hypomorphic alleles of shby caused poor root growth, decreased meristematic activity and defects in radial patterning that are characterized by an increase in the number of cell divisions in the ground tissue that lead to extra cells in the cortex and endodermis, as well as additional cell layers. Analysis of genetic and molecular markers indicates that SHBY acts in a pathway that partially overlaps with SHR, SCR, PLETHORA1 and PLETHORA2 (PLT1 and PLT2). The shby-1 root phenotype was partially phenocopied by treatment of wild-type roots with the proteosome inhibitor MG132 or the gibberellic acid (GA) synthesis inhibitor paclobutrazol (PAC). Our results indicate that SHBY controls root growth downstream of GA in part through the regulation of SHR and SCR.

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

    PubMed

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

    2015-12-01

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

  9. 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.

  10. 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.

  11. 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

  12. Analysis of Arabidopsis thaliana root growth kinetics with high temporal and spatial resolution

    PubMed Central

    Yazdanbakhsh, Nima; Fisahn, Joachim

    2010-01-01

    Background Methods exist to quantify the distribution of growth rate over the root axis. However, non-destructive, high-throughput evaluations of total root elongation in controlled environments and the field are lacking in growth studies. A new imaging approach to analyse total root elongation is described. Scope High pixel resolution of the images enables the study of growth in short time intervals and provides high temporal resolution. Using the method described, total root elongation rates are calculated from the displacement of the root tip. Although the absolute root elongation rate changes in response to growth conditions, this set-up enables root growth of Arabidopsis wild-type seedlings to be followed for more than 1 month after germination. The method provides an easy approach to decipher root extension rate and much simpler calculations compared with other methods that use segmental growth to address this question. Conclusions The high temporal resolution allows small modifications of total root elongation growth to be revealed. Furthermore, with the options to investigate growth of various mutants in diverse growth conditions the present tool allows modulations in root growth kinetics due to different biotic and abiotic stimuli to be unravelled. Measurements performed on Arabidopsis thaliana wild-type (Col0) plants revealed rhythms superimposed on root elongation. Results obtained from the starchless mutant pgm, however, present a clearly modified pattern. As expected, deviation is strongest during the dark period. PMID:20421235

  13. Root growth, mycorrhization and physiological effects of plants growing on oil tailing sands

    NASA Astrophysics Data System (ADS)

    Boldt-Burisch, Katja M.; Naeth, Anne M.; Schneider, Bernd Uwe; Hüttl, Reinhard F.

    2015-04-01

    Surface mining creates large, intense disturbances of soils and produces large volumes of by-products and waste materials. After mining processes these materials often provide the basis for land reclamation and ecosystem restoration. In the present study, tailing sands (TS) and processed mature fine tailings (pMFT) from Fort McMurray (Alberta, Canada) were used. They represent challenging material for ecosystem rebuilding because of very low nutrient contents of TS and oil residuals, high density of MFT material. In this context, little is known about the interactions of pure TS, respectively mixtures of TS and MFT and root growth, mycorrhization and plant physiological effects. Four herbaceous plant species (Elymus trachycaulus, Koeleria macrantha, Deschampsia cespitosa, Lotus corniculatus) were chosen to investigate root development, chlorophyll fluorescence and mycorrhization intensity with and without application of Glomus mosseae (arbuscular mycorrhizae) on mainly tailing sands. Surprisingly both, plants growing on pure TS and plants growing on TS with additional AM-application showed mycorrhization of roots. In general, the mycorrhization intensity was lower for plants growing on pure tailings sands, but it is an interesting fact that there is a potential for mycorrhization available in tailing sands. The mycorrhizal intensity strongly increased with application of G. mosseae for K. macrantha and L. corniculatus and even more for E. trachycaulus. For D. cespitosa similar high mycorrhiza infection frequency was found for both variants, with and without AM-application. By the application of G. mosseae, root growth of E. trachycaulus and K. macrantha was significantly positively influenced. Analysis of leaf chlorophyll fluorescence showed no significant differences for E. trachycaulus but significant positive influence of mycorrhizal application on the physiological status of L. corniculatus. However, this effect could not be detected when TS was mixed with MFT

  14. Mechanical failure of fine root cortical cells initiates plant hydraulic decline during drought

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  15. Improving root-zone soil moisture estimations using dynamic root growth and crop phenology

    NASA Astrophysics Data System (ADS)

    Hashemian, Minoo; Ryu, Dongryeol; Crow, Wade T.; Kustas, William P.

    2015-12-01

    Water Energy Balance (WEB) Soil Vegetation Atmosphere Transfer (SVAT) modelling can be used to estimate soil moisture by forcing the model with observed data such as precipitation and solar radiation. Recently, an innovative approach that assimilates remotely sensed thermal infrared (TIR) observations into WEB-SVAT to improve the results has been proposed. However, the efficacy of the model-observation integration relies on the model's realistic representation of soil water processes. Here, we explore methods to improve the soil water processes of a simple WEB-SVAT model by adopting and incorporating an exponential root water uptake model with water stress compensation and establishing a more appropriate soil-biophysical linkage between root-zone moisture content, above-ground states and biophysical indices. The existing WEB-SVAT model is extended to a new Multi-layer WEB-SVAT with Dynamic Root distribution (MWSDR) that has five soil layers. Impacts of plant root depth variations, growth stages and phenological cycle of the vegetation on transpiration are considered in developing stages. Hydrometeorological and biogeophysical measurements collected from two experimental sites, one in Dookie, Victoria, Australia and the other in Ponca, Oklahoma, USA, are used to validate the new model. Results demonstrate that MWSDR provides improved soil moisture, transpiration and evaporation predictions which, in turn, can provide an improved physical basis for assimilating remotely sensed data into the model. Results also show the importance of having an adequate representation of vegetation-related transpiration process for an appropriate simulation of water transfer in a complicated system of soil, plants and atmosphere.

  16. Increased soil phosphorus availability induced by faba bean root exudation stimulates root growth and phosphorus uptake in neighbouring maize.

    PubMed

    Zhang, Deshan; Zhang, Chaochun; Tang, Xiaoyan; Li, Haigang; Zhang, Fusuo; Rengel, Zed; Whalley, William R; Davies, William J; Shen, Jianbo

    2016-01-01

    Root growth is influenced by soil nutrients and neighbouring plants, but how these two drivers affect root interactions and regulate plant growth dynamics is poorly understood. Here, interactions between the roots of maize (Zea mays) and faba bean (Vicia faba) are characterized. Maize was grown alone (maize) or with maize (maize/maize) or faba bean (maize/faba bean) as competitors under five levels of phosphorus (P) supply, and with homogeneous or heterogeneous P distribution. Maize had longer root length and greater shoot biomass and P content when grown with faba bean than with maize. At each P supply rate, faba bean had a smaller root system than maize but greater exudation of citrate and acid phosphatase, suggesting a greater capacity to mobilize P in the rhizosphere. Heterogeneous P availability enhanced the root-length density of maize but not faba bean. Maize root proliferation in the P-rich patches was associated with increased shoot P uptake. Increased P availability by localized P application or by the presence of faba bean exudation stimulated root morphological plasticity and increased shoot growth in maize in the maize/faba bean mixture, suggesting that root interactions of neighbouring plants can be modified by increased P availability.

  17. How grow-and-switch gravitropism generates root coiling and root waving growth responses in Medicago truncatula

    PubMed Central

    Tan, Tzer Han; Silverberg, Jesse L.; Floss, Daniela S.; Harrison, Maria J.; Henley, Christopher L.; Cohen, Itai

    2015-01-01

    Experimental studies show that plant root morphologies can vary widely from straight gravity-aligned primary roots to fractal-like root architectures. However, the opaqueness of soil makes it difficult to observe how environmental factors modulate these patterns. Here, we combine a transparent hydrogel growth medium with a custom built 3D laser scanner to directly image the morphology of Medicago truncatula primary roots. In our experiments, root growth is obstructed by an inclined plane in the growth medium. As the tilt of this rigid barrier is varied, we find Medicago transitions between randomly directed root coiling, sinusoidal root waving, and normal gravity-aligned morphologies. Although these root phenotypes appear morphologically distinct, our analysis demonstrates the divisions are less well defined, and instead, can be viewed as a 2D biased random walk that seeks the path of steepest decent along the inclined plane. Features of this growth response are remarkably similar to the widely known run-and-tumble chemotactic behavior of Escherichia coli bacteria, where biased random walks are used as optimal strategies for nutrient uptake. PMID:26432881

  18. How grow-and-switch gravitropism generates root coiling and root waving growth responses in Medicago truncatula.

    PubMed

    Tan, Tzer Han; Silverberg, Jesse L; Floss, Daniela S; Harrison, Maria J; Henley, Christopher L; Cohen, Itai

    2015-10-20

    Experimental studies show that plant root morphologies can vary widely from straight gravity-aligned primary roots to fractal-like root architectures. However, the opaqueness of soil makes it difficult to observe how environmental factors modulate these patterns. Here, we combine a transparent hydrogel growth medium with a custom built 3D laser scanner to directly image the morphology of Medicago truncatula primary roots. In our experiments, root growth is obstructed by an inclined plane in the growth medium. As the tilt of this rigid barrier is varied, we find Medicago transitions between randomly directed root coiling, sinusoidal root waving, and normal gravity-aligned morphologies. Although these root phenotypes appear morphologically distinct, our analysis demonstrates the divisions are less well defined, and instead, can be viewed as a 2D biased random walk that seeks the path of steepest decent along the inclined plane. Features of this growth response are remarkably similar to the widely known run-and-tumble chemotactic behavior of Escherichia coli bacteria, where biased random walks are used as optimal strategies for nutrient uptake.

  19. How grow-and-switch gravitropism generates root coiling and root waving growth responses in Medicago truncatula.

    PubMed

    Tan, Tzer Han; Silverberg, Jesse L; Floss, Daniela S; Harrison, Maria J; Henley, Christopher L; Cohen, Itai

    2015-10-20

    Experimental studies show that plant root morphologies can vary widely from straight gravity-aligned primary roots to fractal-like root architectures. However, the opaqueness of soil makes it difficult to observe how environmental factors modulate these patterns. Here, we combine a transparent hydrogel growth medium with a custom built 3D laser scanner to directly image the morphology of Medicago truncatula primary roots. In our experiments, root growth is obstructed by an inclined plane in the growth medium. As the tilt of this rigid barrier is varied, we find Medicago transitions between randomly directed root coiling, sinusoidal root waving, and normal gravity-aligned morphologies. Although these root phenotypes appear morphologically distinct, our analysis demonstrates the divisions are less well defined, and instead, can be viewed as a 2D biased random walk that seeks the path of steepest decent along the inclined plane. Features of this growth response are remarkably similar to the widely known run-and-tumble chemotactic behavior of Escherichia coli bacteria, where biased random walks are used as optimal strategies for nutrient uptake. PMID:26432881

  20. PATTERNS OF ROOT GROWTH, TURNOVER, AND DISTRIBUTION IN DIFFERENT AGED PONDEROSA PINE STANDS

    EPA Science Inventory

    The objectives of this study are to examine the spatial distribution of roots in relation to canopy size and tree distribution, and to determine if rates of fine root production and turnover are similar in the different aged stands. During the fall of 1998, 54 clear plexiglass t...

  1. Epidermal growth factor receptor in adult human dorsal root ganglia.

    PubMed

    Huerta, J J; Diaz-Trelles, R; Naves, F J; Llamosas, M M; Del Valle, M E; Vega, J A

    1996-09-01

    Transforming growth factor-alpha (TGFalpha) enhances neuronal survival and neurite outgrowth in cultured dorsal root ganglia (DRG) sensory neurons. It binds a membrane protein, denominated epidermal growth factor receptor (EGFr). EGFr has been localized in developing and adult human DRG. However, it remains to be elucidated whether all DRG neurons express EGFr or whether differences exist among neuronal subtypes. This study was undertaken to investigate these topics in adult human DRG using immunoblotting, and combined immunohistochemistry and image analysis techniques. A mouse monoclonal antibody (clone F4) mapping within the intracytoplasmic domain of EGFr was used. Immunoblotting revealed two main proteins with estimated molecular masses of approximately/equal to 65 kDa and 170 kDa, and thus consistent with the full-length EGFr. Additional protein bands were also encountered. Light immunohistochemistry revealed specific immunoreactivity (IR) for EGFr-like proteins in most (86%) primary sensory neurons, the intensity of immunostaining being stronger in the small- and intermediate-sized ones. Furthermore, EGFr-like IR was also observed in the satellite glial cells of the ganglia as well as in the intraganglionic and dorsal root Schwann cells. Taken together, our findings demonstrate that EGFr, and other related proteins containing the epitope labeled with the antibody F4, are responsible for the EGFr IR reported in DRG. Furthermore, we demonstrated heterogeneity in the expression of EGFr-like IR in adult human primary sensory neurons, which suggests different responsiveness to their ligands.

  2. Root growth dynamics linked to aboveground growth in walnuts (Juglans regia L.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Background and Aims: Examination of belowground plant responses to canopy and soil moisture manipulation is scant compared to that aboveground but needed to understand whole plant responses to environmental factors. Plasticity in the seasonal timing and vertical distribution of root growth in respon...

  3. Naphthenic acids inhibit root water transport, gas exchange and leaf growth in aspen (Populus tremuloides) seedlings.

    PubMed

    Kamaluddin, M; Zwiazek, Janusz J

    2002-12-01

    Effects of sodium naphthenates (NAs) on root hydraulic conductivity (Lp) and gas exchange processes were examined in aspen (Populus tremuloides Michx.) seedlings grown in solution culture. Exposure of roots to NAs for 3-5 weeks significantly decreased Lp and stomatal conductance. Root-absorbed NAs also decreased leaf chlorophyll concentration, net photosynthesis and leaf growth. Short-term (< or = 2 h) exposure of excised roots to NAs significantly decreased root water flow (Qv) with a concomitant decline in root respiration. We conclude that NAs metabolically inhibited Lp, likely by affecting water channel activity, and that this inhibition could be responsible for the observed reductions in gas exchange and leaf growth.

  4. Flavonols Mediate Root Phototropism and Growth through Regulation of Proliferation-to-Differentiation Transition.

    PubMed

    Silva-Navas, Javier; Moreno-Risueno, Miguel A; Manzano, Concepción; Téllez-Robledo, Bárbara; Navarro-Neila, Sara; Carrasco, Víctor; Pollmann, Stephan; Gallego, F Javier; Del Pozo, Juan C

    2016-06-01

    Roots normally grow in darkness, but they may be exposed to light. After perceiving light, roots bend to escape from light (root light avoidance) and reduce their growth. How root light avoidance responses are regulated is not well understood. Here, we show that illumination induces the accumulation of flavonols in Arabidopsis thaliana roots. During root illumination, flavonols rapidly accumulate at the side closer to light in the transition zone. This accumulation promotes asymmetrical cell elongation and causes differential growth between the two sides, leading to root bending. Furthermore, roots illuminated for a long period of time accumulate high levels of flavonols. This high flavonol content decreases both auxin signaling and PLETHORA gradient as well as superoxide radical content, resulting in reduction of cell proliferation. In addition, cytokinin and hydrogen peroxide, which promote root differentiation, induce flavonol accumulation in the root transition zone. As an outcome of prolonged light exposure and flavonol accumulation, root growth is reduced and a different root developmental zonation is established. Finally, we observed that these differentiation-related pathways are required for root light avoidance. We propose that flavonols function as positional signals, integrating hormonal and reactive oxygen species pathways to regulate root growth direction and rate in response to light.

  5. Flavonols Mediate Root Phototropism and Growth through Regulation of Proliferation-to-Differentiation Transition.

    PubMed

    Silva-Navas, Javier; Moreno-Risueno, Miguel A; Manzano, Concepción; Téllez-Robledo, Bárbara; Navarro-Neila, Sara; Carrasco, Víctor; Pollmann, Stephan; Gallego, F Javier; Del Pozo, Juan C

    2016-06-01

    Roots normally grow in darkness, but they may be exposed to light. After perceiving light, roots bend to escape from light (root light avoidance) and reduce their growth. How root light avoidance responses are regulated is not well understood. Here, we show that illumination induces the accumulation of flavonols in Arabidopsis thaliana roots. During root illumination, flavonols rapidly accumulate at the side closer to light in the transition zone. This accumulation promotes asymmetrical cell elongation and causes differential growth between the two sides, leading to root bending. Furthermore, roots illuminated for a long period of time accumulate high levels of flavonols. This high flavonol content decreases both auxin signaling and PLETHORA gradient as well as superoxide radical content, resulting in reduction of cell proliferation. In addition, cytokinin and hydrogen peroxide, which promote root differentiation, induce flavonol accumulation in the root transition zone. As an outcome of prolonged light exposure and flavonol accumulation, root growth is reduced and a different root developmental zonation is established. Finally, we observed that these differentiation-related pathways are required for root light avoidance. We propose that flavonols function as positional signals, integrating hormonal and reactive oxygen species pathways to regulate root growth direction and rate in response to light. PMID:26628743

  6. [Impacts of root-zone hypoxia stress on muskmelon growth, its root respiratory metabolism, and antioxidative enzyme activities].

    PubMed

    Liu, Yi-Ling; Li, Tian-Lai; Sun, Zhou-Ping; Chen, Ya-Dong

    2010-06-01

    By using aeroponics culture system, this paper studied the impacts of root-zone hypoxia (10% O2 and 5% O2) stress on the plant growth, root respiratory metabolism, and antioxidative enzyme activities of muskmelon at its fruit development stage. Root-zone hypoxia stress inhibited the plant growth of muskmelon, resulting in the decrease of plant height, root length, and fresh and dry biomass. Comparing with the control (21% O2), hypoxia stress reduced the root respiration rate and malate dehydrogenase (MDH) activity significantly, and the impact of 5% O2 stress was more serious than that of 10% O2 stress. Under hypoxic conditions, the lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH), pyruvate decarboxylase (PDC), superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities and the malondialdehyde (MDA) content were significantly higher than the control. The increment of antioxidative enzyme activities under 10% O2 stress was significantly higher than that under 5% O2 stress, while the MDA content was higher under 5% O2 stress than under 10% O2 stress, suggesting that when the root-zone oxygen concentration was below 10%, the aerobic respiration of muskmelon at its fruit development stage was obviously inhibited while the anaerobic respiration was accelerated, and the root antioxidative enzymes induced defense reaction. With the increasing duration of hypoxic stress, the lipid peroxidation would be aggravated, resulting in the damages on muskmelon roots, inhibition of plant growth, and decrease of fruit yield and quality. PMID:20873618

  7. [Impacts of root-zone hypoxia stress on muskmelon growth, its root respiratory metabolism, and antioxidative enzyme activities].

    PubMed

    Liu, Yi-Ling; Li, Tian-Lai; Sun, Zhou-Ping; Chen, Ya-Dong

    2010-06-01

    By using aeroponics culture system, this paper studied the impacts of root-zone hypoxia (10% O2 and 5% O2) stress on the plant growth, root respiratory metabolism, and antioxidative enzyme activities of muskmelon at its fruit development stage. Root-zone hypoxia stress inhibited the plant growth of muskmelon, resulting in the decrease of plant height, root length, and fresh and dry biomass. Comparing with the control (21% O2), hypoxia stress reduced the root respiration rate and malate dehydrogenase (MDH) activity significantly, and the impact of 5% O2 stress was more serious than that of 10% O2 stress. Under hypoxic conditions, the lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH), pyruvate decarboxylase (PDC), superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities and the malondialdehyde (MDA) content were significantly higher than the control. The increment of antioxidative enzyme activities under 10% O2 stress was significantly higher than that under 5% O2 stress, while the MDA content was higher under 5% O2 stress than under 10% O2 stress, suggesting that when the root-zone oxygen concentration was below 10%, the aerobic respiration of muskmelon at its fruit development stage was obviously inhibited while the anaerobic respiration was accelerated, and the root antioxidative enzymes induced defense reaction. With the increasing duration of hypoxic stress, the lipid peroxidation would be aggravated, resulting in the damages on muskmelon roots, inhibition of plant growth, and decrease of fruit yield and quality.

  8. Assessment of improved root growth representation in a 1-D, field scale crop model

    NASA Astrophysics Data System (ADS)

    Miltin Mboh, Cho; Gaiser, Thomas; Ewert, Frank

    2015-04-01

    Many 1-D, field scale crop models over-simplify root growth. The over-simplification of this "hidden half" of the crop may have significant consequences on simulated root water and nutrient uptake with a corresponding reflection on the simulated crop yields. Poor representation of root growth in crop models may therefore constitute a major source of uncertainty propagation. In this study we assess the effect of an improved representation of root growth in a model solution of the model framework SIMPLACE (Scientific Impact assessment and Modeling PLatform for Advanced Crop and Ecosystem management) compared to conventional 1-D approaches. The LINTUL5 crop growth model is coupled to the Hillflow soil water balance model within the SIMPLACE modeling framework (Gaiser et al, 2013). Root water uptake scenarios in the soil hydrological simulator Hillflow (Bronstert, 1995) together with an improved representation of root growth is compared to scenarios for which root growth is simplified. The improvement of root growth is achieved by integrating root growth solutions from R-SWMS (Javaux et al., 2008) into the SIMPLACE model solution. R-SWMS is a three dimensional model for simultaneous modeling of root growth, soil water fluxes and solute transport and uptake. These scenarios are tested by comparing how well the simulated water contents match with the observed soil water dynamics. The impacts of the scenarios on above ground biomass and wheat grain are assessed

  9. [Effects of drought stress on the root growth and development and physiological characteristics of peanut].

    PubMed

    Ding, Hong; Zhang, Zhi-Meng; Dai, Liang-Xiang; Kang, Tao; Ci, Dun-Wei; Song, Wen-Wu

    2013-06-01

    Taking two peanut varieties Huayu 17 and Tangke 8 as test objects, a soil column culture experiment was conducted in a rainproof tank to study the peanut root morphological development and physiological characteristics at late growth stages under moderate drought and well-watered conditions. Tanke 8 had more developed root system and higher yield and drought coefficient, while Huayu 17 had poorer root adaptability to drought stress. For the two varieties, their root length density and root biomass were mainly distributed in 0-40 cm soil layer, whereas their root traits differed in the same soil layer. The total root length, total root surface area, and total root volume of Huayu 17 at each growth stage were smaller under drought stress than under well-balanced water treatment, while these root characteristics of Tangke 8 under drought stress only decreased at flowering-pegging stage. Drought stress increased the root biomass, surface area, and volume of the two varieties in 20-40 cm soil layer, but decreased these root traits in the soil layers below 40 cm. Under drought stress, the root activity of the two varieties in the soil layers below 40 cm at pod filling stage decreased, and the decrement was larger for Huayu 17. The differences in the root system development and physiological characteristics of the two varieties at late growth stages under drought stress suggested that the root system of the two varieties had different water absorption and utilization under drought stress.

  10. 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.

  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. Growth of AM fungi on in vitro root organ culture of Sorghum vulgare and Saccharum officinarum.

    PubMed

    Raman, N; Sahadevan, C; Srinivasan, V

    2001-12-01

    Spores of Gl mosseae and Gig gigantea germinated on minimal medium produced extraradical mycelium. Gl. mosseae infected roots of S. officinarum in in vitro condition were inoculated in M medium with in vitro cultured roots of Sorghum vulgare (test roots). From the infected root of S. officinarum, the mycelium developed and it infected the test roots. The roots developed new mycelia and further the mycelia produced a few hyaline spores. In MS medium combined with soil extract, root exudate, thiamine HCl and inositol combination, spore germination and germ tube growth were higher when compared with other media. PMID:12018527

  13. AtOPR3 specifically inhibits primary root growth in Arabidopsis under phosphate deficiency.

    PubMed

    Zheng, Hongyan; Pan, Xiaoying; Deng, Yuxia; Wu, Huamao; Liu, Pei; Li, Xuexian

    2016-01-01

    The primary root plays essential roles in root development, nutrient absorption, and root architectural establishment. Primary root growth is generally suppressed by phosphate (P) deficiency in A. thaliana; however, the underlying molecular mechanisms are largely elusive to date. We found that AtOPR3 specifically inhibited primary root growth under P deficiency via suppressing root tip growth at the transcriptional level, revealing an important novel function of AtOPR3 in regulating primary root response to the nutrient stress. Importantly, AtOPR3 functioned to down-regulate primary root growth under P limitation mostly by its own, rather than depending on the Jasmonic acid signaling pathway. Further, AtOPR3 interacted with ethylene and gibberellin signaling pathways to regulate primary root growth upon P deficiency. In addition, the AtOPR3's function in inhibiting primary root growth upon P limitation was also partially dependent on auxin polar transport. Together, our studies provide new insights into how AtOPR3, together with hormone signaling interactions, modulates primary root growth in coping with the environmental stress in Arabidopsis.

  14. AtOPR3 specifically inhibits primary root growth in Arabidopsis under phosphate deficiency

    PubMed Central

    Zheng, Hongyan; Pan, Xiaoying; Deng, Yuxia; Wu, Huamao; Liu, Pei; Li, Xuexian

    2016-01-01

    The primary root plays essential roles in root development, nutrient absorption, and root architectural establishment. Primary root growth is generally suppressed by phosphate (P) deficiency in A. thaliana; however, the underlying molecular mechanisms are largely elusive to date. We found that AtOPR3 specifically inhibited primary root growth under P deficiency via suppressing root tip growth at the transcriptional level, revealing an important novel function of AtOPR3 in regulating primary root response to the nutrient stress. Importantly, AtOPR3 functioned to down-regulate primary root growth under P limitation mostly by its own, rather than depending on the Jasmonic acid signaling pathway. Further, AtOPR3 interacted with ethylene and gibberellin signaling pathways to regulate primary root growth upon P deficiency. In addition, the AtOPR3’s function in inhibiting primary root growth upon P limitation was also partially dependent on auxin polar transport. Together, our studies provide new insights into how AtOPR3, together with hormone signaling interactions, modulates primary root growth in coping with the environmental stress in Arabidopsis. PMID:27101793

  15. Asymmetric growth of root epidermal cells is related to the differentiation of root hair cells in Hordeum vulgare (L.)

    PubMed Central

    Marzec, Marek

    2013-01-01

    The root epidermis of most vascular plants harbours two cell types, namely trichoblasts (capable of producing a root hair) and atrichoblasts. Here, in vivo analysis, confocal laser-scanning microscopy, transmission electron microscopy, histological analysis, and three-dimensional reconstruction were used to characterize the cell types present in the barley root epidermis and their distribution in the tissue. Both trichoblasts and atrichoblasts were present in the wild-type cultivars and could be distinguished from one another at an early stage. Trichoblast/atrichoblast differentiation depended on asymmetric cell expansion after a period of symmetrical cell division. After asymmetric growth, only the shorter epidermal cells could produce root hairs, whereas the longer cells became atrichoblasts. Moreover, the root epidermis did not develop root hairs at all if the epidermal cells did not differentiate into two asymmetric cell types. The root hairless phenotype of bald root barley (brb) and root hairless 1.b (rhl1.b) mutants was caused by a mutation in a gene related to the asymmetric expansion of the root epidermal cells. Additionally, the results showed that the mechanism of trichoblast/atrichoblast differentiation is not evolutionally conserved across the subfamilies of the Poaceae; in the Pooideae subfamily, both asymmetric division and asymmetric cell expansion have been observed. PMID:24043851

  16. Larval growth of Diaprepes abbreviatus (Coleoptera: Curculionidae) and resulting root injury to three citrus varieties in two soil types.

    PubMed

    Rogers, S; Mccoy, C W; Graham, J H

    2000-04-01

    Larval growth and intraspecific competition of Diaprepes abbreviatus (L.) larvae and consequent root injury in container-grown citrus in the greenhouse were evaluated. Roots of Carrizo citrange, Citrus sinesis L. Osbeck x Poncirus trifoliata (L.) Raf.; Cleopatra mandarin, C. reticulata Blanco, and Swingle citrumelo, C. paradisi Macf. x P. trifoliata (L.) Raf. rootstock seedlings grown in Candler fine sand and potting soil were colonized with different populations of D. abbreviatus larvae. Larvae were exposed to the seedlings for 79 d. Larval growth and development increased steadily for approximately 70 d on all rootstock-soil combinations, at which time most larvae were instars 6-8. Most feeding injury occurred to roots when larvae were between instars 3 and 6. Larval weight reached a plateau at approximately 70 d, but often declined between 70 and 79 d. When larvae were small, injury to seedlings developed slowly, primarily on fibrous roots, then feeding increased rapidly, often resulting in total consumption of both fibrous root and bark tissue. Although not statistically significant, root injury developed slightly slower on Swingle citrumelo compared with Carrizo and Cleopatra rootstocks, but damage was comparable by 79 d. Little or no difference in consumptive benefit to the larvae was found between the rootstocks. Based on larval weight days, little feeding injury occurred during the first 21 d, but increased rapidly between 21 and 60 d. Soil type affected the rate of larval growth and development, with potting soil contributing to greater growth rates. Detritus in potting soil provided little or no nutritional resource, suggesting that the effect of potting soil on larval development was primarily physical. In addition, fewer inoculated larvae per seedling exhibited greater weight gains than higher infestation densities, suggesting that intraspecific competition for nutritional resources influenced larval development.

  17. Does a tradeoff exist between morphological and physiological root plasticity? A comparison of grass growth forms

    NASA Astrophysics Data System (ADS)

    Derner, Justin D.; Briske, David D.

    1999-09-01

    A series of experiments were conducted to evaluate the potential tradeoff between morphological and physiological root plasticity in caespitose and rhizomatous grass growth forms in semi-arid and mesic communities. Morphological and physiological root plasticity were evaluated with in-growth cores and excised root assays, respectively. The rhizomatous grass in the semi-arid community was the only species to display significant physiological root plasticity, but all species possessed the capacity to proportionally increase 15N uptake with increasing concentrations of ( 15NH 4) 2SO 4 solution. Neither the caespitose nor the rhizomatous grass displayed morphological root plasticity in response to nitrogen addition in the mesic community. In contrast, significant morphological root plasticity occurred in species of both growth forms in the semi-arid community. These data suggest that the compact architecture and the ability to accumulate nutrients in soils directly beneath caespitose grasses did not increase selection pressure for physiological root plasticity at the expense of morphological root plasticity and that the coarse grained foraging strategy and low density of large diameter roots did not increase morphological root plasticity at the expense of physiological root plasticity in rhizomatous grasses. These preliminary data suggest that 1) a high maximum uptake rate for nitrogen in these perennial grasses may minimize the expression of physiological root plasticity, 2) morphological and physiological root plasticity may represent complimentary, rather than alternative, foraging strategies, and 3) the expression of root plasticity may be strongly influenced by abiotic variables within specific habitats.

  18. Effect of calmodulin antagonists on the growth and graviresponsiveness of primary roots of maize.

    PubMed

    Stinemetz, C L; Hasenstein, K H; Young, L M; Evans, M L

    1992-11-01

    We examined the effect of calmodulin (CaM) antagonists applied at the root tip on root growth, gravity-induced root curvature, and the movement of calcium across the root tip and auxin (IAA) across the elongation zone of gravistimulated roots. All of the CaM antagonists used in these studies delayed gravity-induced curvature at a concentration (1 micromole) that did not affect root growth. Calmodulin antagonists (> or = 1 micromole) inhibited downward transport of label from 45Ca2+ across the caps of gravistimulated roots relative to the downward transport of 45Ca2+ in gravistimulated roots which were not treated with CaM antagonists. Application of CaM antagonists at the root tip (> or = 1 micromole) also decreased the relative downward movement of label from 3H-IAA applied to the upper side of the elongation zone of gravistimulated roots. In general, tip application of antagonists inhibited neither the upward transport of 45Ca2+ in the root tip nor the upward movement of label from 3H-IAA in the elongation zone of gravistimulated roots. Thus, roots treated with CaM antagonists > or = 1 micromole become less graviresponsive and exhibit reduced or even a reversal of downward polarity of calcium transport across the root tip and IAA transport across the elongation zone. The results indicate that calmodulin-regulated events play a role in root gravitropism. PMID:11537498

  19. Effect of calmodulin antagonists on the growth and graviresponsiveness of primary roots of maize

    NASA Technical Reports Server (NTRS)

    Stinemetz, C. L.; Hasenstein, K. H.; Young, L. M.; Evans, M. L.

    1992-01-01

    We examined the effect of calmodulin (CaM) antagonists applied at the root tip on root growth, gravity-induced root curvature, and the movement of calcium across the root tip and auxin (IAA) across the elongation zone of gravistimulated roots. All of the CaM antagonists used in these studies delayed gravity-induced curvature at a concentration (1 micromole) that did not affect root growth. Calmodulin antagonists (> or = 1 micromole) inhibited downward transport of label from 45Ca2+ across the caps of gravistimulated roots relative to the downward transport of 45Ca2+ in gravistimulated roots which were not treated with CaM antagonists. Application of CaM antagonists at the root tip (> or = 1 micromole) also decreased the relative downward movement of label from 3H-IAA applied to the upper side of the elongation zone of gravistimulated roots. In general, tip application of antagonists inhibited neither the upward transport of 45Ca2+ in the root tip nor the upward movement of label from 3H-IAA in the elongation zone of gravistimulated roots. Thus, roots treated with CaM antagonists > or = 1 micromole become less graviresponsive and exhibit reduced or even a reversal of downward polarity of calcium transport across the root tip and IAA transport across the elongation zone. The results indicate that calmodulin-regulated events play a role in root gravitropism.

  20. Disentangling the intertwined genetic bases of root and shoot growth in Arabidopsis.

    PubMed

    Bouteillé, Marie; Rolland, Gaëlle; Balsera, Crispulo; Loudet, Olivier; Muller, Bertrand

    2012-01-01

    Root growth and architecture are major components of plant nutrient and water use efficiencies and these traits are the matter of extensive genetic analysis in several crop species. Because root growth relies on exported assimilate from the shoot, and changes in assimilate supply are known to alter root architecture, we hypothesized (i) that the genetic bases of root growth could be intertwined with the genetic bases of shoot growth and (ii) that the link could be either positive, with alleles favouring shoot growth also favouring root growth, or negative, because of competition for assimilates. We tested these hypotheses using a quantitative genetics approach in the model species Arabidopsis thaliana and the Bay-0 × Shahdara recombinant inbred lines population. In accordance with our hypothesis, root and shoot growth traits were strongly correlated and most root growth quantitative trait loci (QTLs) colocalized with shoot growth QTLs with positive alleles originating from either the same or the opposite parent. In order to identify regions that could be responsible for root growth independently of the shoot, we generated new variables either based on root to shoot ratios, residuals of root to shoot correlations or coordinates of principal component analysis. These variables showed high heritability allowing genetic analysis. They essentially all yielded similar results pointing towards two regions involved in the root--shoot balance. Using Heterogeneous Inbred Families (a kind of near-isogenic lines), we validated part of the QTLs present in these two regions for different traits. Our study thus highlights the difficulty of disentangling intertwined genetic bases of root and shoot growth and shows that this difficulty can be overcome by using simple statistical tools.

  1. 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.

  2. 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. PMID:26996006

  3. The bHLH transcription factor SPATULA regulates root growth by controlling the size of the root meristem

    PubMed Central

    2013-01-01

    Background The Arabidopsis thaliana gene SPATULA (SPT), encoding a bHLH transcription factor, was originally identified for its role in pistil development. SPT is necessary for the growth and development of all carpel margin tissues including the style, stigma, septum and transmitting tract. Since then, it has been shown to have pleiotropic roles during development, including restricting the meristematic region of the leaf primordia and cotyledon expansion. Although SPT is expressed in roots, its role in this organ has not been investigated. Results An analysis of embryo and root development showed that loss of SPT function causes an increase in quiescent center size in both the embryonic and postembryonic stem cell niches. In addition, root meristem size is larger due to increased division, which leads to a longer primary root. spt mutants exhibit other pleiotropic developmental phenotypes, including more flowers, shorter internodes and an extended flowering period. Genetic and molecular analysis suggests that SPT regulates cell proliferation in parallel to gibberellic acid as well as affecting auxin accumulation or transport. Conclusions Our data suggest that SPT functions in growth control throughout sporophytic growth of Arabidopsis, but is not necessary for cell fate decisions except during carpel development. SPT functions independently of gibberellic acid during root development, but may play a role in regulating auxin transport or accumulation. Our data suggests that SPT plays a role in control of root growth, similar to its roles in above ground tissues. PMID:23280064

  4. Root growth of interspecific sunflower seedlings derived from wild perennial sunflower species

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Roots play a major role in maintaining an adequate water supply for plant growth and development. Since sunflower is a tap root plant and because the major limitation to yield in semiarid and arid regions is the availability of water, differences in the characteristics of the lateral root system aff...

  5. Near-Threshold Fatigue Crack Growth Behavior of Fine-Grain Nickel-Based Alloys

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Piascik, Robert S.

    2003-01-01

    Constant-Kmax fatigue crack growth tests were performed on two finegrain nickel-base alloys Inconel 718 (DA) and Ren 95 to determine if these alloys exhibit near-threshold time-dependent crack growth behavior observed for fine-grain aluminum alloys in room-temperature laboratory air. Test results showed that increases in K(sub max) values resulted in increased crack growth rates, but no evidence of time-dependent crack growth was observed for either nickel-base alloy at room temperature.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  7. Light regulation of the growth response in corn root gravitropism.

    PubMed

    Kelly, M O; Leopold, A C

    1992-01-01

    Roots of Merit variety corn (Zea mays L.) require red light for orthogravitropic curvature. Experiments were undertaken to identify the step in the pathway from gravity perception to asymmetric growth on which light may act. Red light was effective in inducing gravitropism whether it was supplied concomitant with or as long as 30 minutes after the gravity stimulus (GS). The presentation time was the same whether the GS was supplied in red light or in darkness. Red light given before the GS slightly enhanced the rate of curvature but had little effect on the lag time or on the final curvature. This enhancement was expanded by a delay between the red light pulse and the GS. These results indicate that gravity perception and at least the initial transduction steps proceed in the dark. Light may regulate the final growth (motor) phase of gravitropism. The time required for full expression of the light enhancement of curvature is consistent with its involvement in some light-stimulated biosynthetic event. PMID:11537882

  8. Light regulation of the growth response in corn root gravitropism

    NASA Technical Reports Server (NTRS)

    Kelly, M. O.; Leopold, A. C.

    1992-01-01

    Roots of Merit variety corn (Zea mays L.) require red light for orthogravitropic curvature. Experiments were undertaken to identify the step in the pathway from gravity perception to asymmetric growth on which light may act. Red light was effective in inducing gravitropism whether it was supplied concomitant with or as long as 30 minutes after the gravity stimulus (GS). The presentation time was the same whether the GS was supplied in red light or in darkness. Red light given before the GS slightly enhanced the rate of curvature but had little effect on the lag time or on the final curvature. This enhancement was expanded by a delay between the red light pulse and the GS. These results indicate that gravity perception and at least the initial transduction steps proceed in the dark. Light may regulate the final growth (motor) phase of gravitropism. The time required for full expression of the light enhancement of curvature is consistent with its involvement in some light-stimulated biosynthetic event.

  9. Spatial Heterogeneity of Fine Root Biomass and Soil Carbon in a California Oak Savanna Illuminates Plant Functional Strategy Across Periods of High and Low Resource Supply

    NASA Astrophysics Data System (ADS)

    Koteen, L. E.; Raz Yaseef, N.; Baldocchi, D. D.

    2014-12-01

    We sampled isolated trees and tree clusters from a blue oak, Quercus douglasii, savanna in California USA to determine the spatial heterogeneity of fine root biomass and soil carbon across the landscape as a function of tree size, age and configuration. Our goal was to understand how fine root structure enables sustained ecosystem metabolism through a summer of very limited moisture availability and high heat, and facilitates resource acquisition during the short spring period of high resource supply. An additional goal was to provide a basis for upscaling root biomass and soil carbon to the landscape scale. We sampled trees of different size and tree clusters via a stratified sampling scheme that accounted for spatial heterogeneity in root biomass and soil carbon with lateral distance from the tree bole, or cluster center, and soil depth. We upscaled these estimates using site-specific information from a lidar survey conducted in the same region over a 36 ha area in 2009. We found that fine roots and soil carbon are spatially heterogeneous in their landscape distribution in oak savanna habitat, and that they greatly increase with tree size and age. We also found that Q. douglasii possesses a dimorphic fine root architecture, uniquely suited to the region's climatic constraints, and exhibits morphological plasticity among trees of different size, age, and physical setting.

  10. Arabidopsis thaliana sku mutant seedlings show exaggerated surface-dependent alteration in root growth vector.

    PubMed

    Rutherford, R; Masson, P H

    1996-08-01

    Roots of wild-type Arabidopsis thaliana seedlings in the Wassilewskija (WS) and Landsberg erecta (Ler) ecotypes often grow aslant on vertical agar surfaces. Slanted root growth always occurs to the right of the gravity vector when the root is viewed through the agar surface, and is not observed in the Columbia ecotype. Right-slanted root growth is surface-dependent and does not result directly from directional environmental stimuli or gradients in the plane of skewing. We have isolated two partially dominant mutations in WS (sku1 and sku2) that show an exaggerated right-slanting root-growth phenotype on agar surfaces. The right-slanting root-growth phenotype of wild-type and mutant roots is not the result of diagravitropism or of an alteration in root gravitropism. It is accompanied by a left-handed rotation of the root about its axis within the elongation zone, the rate of which positively correlates with the degree of right-slanted curvature. Our data suggest that the right-slanting root growth phenotype results from an endogenous structural asymmetry that expresses itself by a directional root-tip rotation.

  11. Arabidopsis thaliana sku mutant seedlings show exaggerated surface-dependent alteration in root growth vector

    NASA Technical Reports Server (NTRS)

    Rutherford, R.; Masson, P. H.

    1996-01-01

    Roots of wild-type Arabidopsis thaliana seedlings in the Wassilewskija (WS) and Landsberg erecta (Ler) ecotypes often grow aslant on vertical agar surfaces. Slanted root growth always occurs to the right of the gravity vector when the root is viewed through the agar surface, and is not observed in the Columbia ecotype. Right-slanted root growth is surface-dependent and does not result directly from directional environmental stimuli or gradients in the plane of skewing. We have isolated two partially dominant mutations in WS (sku1 and sku2) that show an exaggerated right-slanting root-growth phenotype on agar surfaces. The right-slanting root-growth phenotype of wild-type and mutant roots is not the result of diagravitropism or of an alteration in root gravitropism. It is accompanied by a left-handed rotation of the root about its axis within the elongation zone, the rate of which positively correlates with the degree of right-slanted curvature. Our data suggest that the right-slanting root growth phenotype results from an endogenous structural asymmetry that expresses itself by a directional root-tip rotation.

  12. Growth inhibition and root ultrastructure of cucumber seedlings exposed to allelochemicals from rye (Secale cereale).

    PubMed

    Burgos, N R; Talbert, R E; Kim, K S; Kuk, Y I

    2004-03-01

    Inhibition of "Calypso" cucumber seedling growth by rye allelochemicals, 2(3H)-benzoxazolinone BOA and 2,4-dihydroxy-1,4(2H)-benzoxazin-3-one DIBOA, was studied by analyzing the growth of seedling tissues and organs. Light and electron microscopy of seedling root cells were also carried out to investigate the mechanism(s) of root growth inhibition and mode of action of these compounds. BOA inhibited root elongation and reduced the number of cucumber lateral roots by 77 and 100% at 0.1 and 0.43 mg BOA/ml deionized (DI) water, respectively. DIBOA also inhibited root growth, but did not affect the number of lateral roots. BOA increased size of cucumber cortical root cells fivefold, but DIBOA had no effect. Both compounds reduced the regeneration of root cap cells and increased the width of cortical cells resulting in increased root diameter. BOA and DIBOA caused increased cytoplasmic vacuolation, reduced ribosome density and dictyosomes, reduced number of mitochondria, and reduced lipid catabolism. Starch granules in amyloplasts of seedling roots treated with BOA and DIBOA were also greatly reduced compared to the control. Changes in cellular ultrastructure indicated that BOA and DIBOA reduced root growth by disrupting lipid metabolism, reducing protein synthesis, and reducing transport or secretory capabilities.

  13. Tree growth and management in Ugandan agroforestry systems: effects of root pruning on tree growth and crop yield.

    PubMed

    Wajja-Musukwe, Tellie-Nelson; Wilson, Julia; Sprent, Janet I; Ong, Chin K; Deans, J Douglas; Okorio, John

    2008-02-01

    Tree root pruning is a potential tool for managing belowground competition when trees and crops are grown together in agroforestry systems. We investigated the effects of tree root pruning on shoot growth and root distribution of Alnus acuminata (H.B. & K.), Casuarina equisetifolia L., Grevillea robusta A. Cunn. ex R. Br., Maesopsis eminii Engl. and Markhamia lutea (Benth.) K. Schum. and on yield of adjacent crops in sub-humid Uganda. The trees were 3 years old at the commencement of the study, and most species were competing strongly with crops. Tree roots were pruned 41 months after planting by cutting and back-filling a trench to a depth of 0.3 m, at a distance of 0.3 m from the trees, on one side of the tree row. The trench was reopened and roots recut at 50 and 62 months after planting. We assessed the effects on tree growth and root distribution over a 3 year period, and crop yield after the third root pruning at 62 months. Overall, root pruning had only a slight effect on aboveground tree growth: height growth was unaffected and diameter growth was reduced by only 4%. A substantial amount of root regrowth was observed by 11 months after pruning. Tree species varied in the number and distribution of roots, and C. equisetifolia and M. lutea had considerably more roots per unit of trunk volume than the other species, especially in the surface soil layers. Casuarina equisetifolia and M. eminii were the tree species most competitive with crops and G. robusta and M. lutea the least competitive. Crop yield data provided strong evidence of the redistribution of root activity following root pruning, with competition increasing on the unpruned side of tree rows. Thus, one-sided root pruning will be useful in only a few circumstances.

  14. Adaptive growth of tree root systems in response to wind action and site conditions.

    PubMed

    Nicoll, Bruce C.; Ray, Duncan

    1996-01-01

    Soil-root plate dimensions and structural root architecture were examined on 46-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) trees that had been mechanically uprooted. Rooting depth was restricted by a water table, and root system morphology had adapted to resist the wind movement associated with shallow rooting. The spread of the root system and the ratio of root mass to shoot mass (root/shoot ratio) were both negatively related to soil-root plate depth. Root systems had more structural root mass on the leeward side than the windward side of the tree relative to the prevailing wind direction. Cross sections of structural roots were obtained at distances of 0.5, 0.75, 1.0, and 1.25 m from the tree center. Buttressed parts of roots had greater lateral and vertical secondary thickening above rather than below the biological center. This uneven growth, which produced a shape similar in cross section to a T-beam, was greater on the leeward side of the tree, and was greatest at 0.5 m from the tree center of shallow rooted trees. Further from the tree, particularly on the windward side, many roots developed eccentric cross-sectional shapes comparable to I-beams, which would efficiently resist vertical flexing. Roots became more ovoid in shape with increasing distance from the tree, especially on deep rooted trees where lateral roots tapered rapidly to a small diameter. We conclude that these forms of adaptive growth in response to wind movement improve the rigidity of the soil-root plate and counteract the increasing vulnerability to windthrow as the tree grows.

  15. Touch and gravitropic set-point angle interact to modulate gravitropic growth in roots.

    PubMed

    Massa, G D; Gilroy, S

    2003-01-01

    Plant roots must sense and respond to a variety of environmental stimuli as they grow through the soil. Touch and gravity represent two of the mechanical signals that roots must integrate to elicit the appropriate root growth patterns and root system architecture. Obstacles such as rocks will impede the general downwardly directed gravitropic growth of the root system and so these soil features must be sensed and this information processed for an appropriate alteration in gravitropic growth to allow the root to avoid the obstruction. We show that primary and lateral roots of Arabidopsis do appear to sense and respond to mechanical barriers placed in their path of growth in a qualitatively similar fashion. Both types of roots exhibited a differential growth response upon contacting the obstacle that directed the main axis of elongation parallel to the barrier. This growth habit was maintained until the obstacle was circumvented, at which point normal gravitropic growth was resumed. Thus, the gravitational set-point angle of the primary and lateral roots prior to encountering the barrier were 95 degrees and 136 degrees respectively and after growing off the end of the obstacle identical set-point angles were reinstated. However, whilst tracking across the barrier, quantitative differences in response were observed between these two classes of roots. The root tip of the primary root maintained an angle of 136 degrees to the horizontal as it traversed the barrier whereas the lateral roots adopted an angle of 154 degrees. Thus, this root tip angle appeared dependent on the gravitropic set-point angle of the root type with the difference in tracking angle quantitatively reflecting differences in initial set-point angle. Concave and convex barriers were also used to analyze the response of the root to tracking along a continuously varying surface. The roots maintained the a fairly fixed angle to gravity on the curved surface implying a constant resetting of this tip angle

  16. Touch and gravitropic set-point angle interact to modulate gravitropic growth in roots

    NASA Technical Reports Server (NTRS)

    Massa, G. D.; Gilroy, S.

    2003-01-01

    Plant roots must sense and respond to a variety of environmental stimuli as they grow through the soil. Touch and gravity represent two of the mechanical signals that roots must integrate to elicit the appropriate root growth patterns and root system architecture. Obstacles such as rocks will impede the general downwardly directed gravitropic growth of the root system and so these soil features must be sensed and this information processed for an appropriate alteration in gravitropic growth to allow the root to avoid the obstruction. We show that primary and lateral roots of Arabidopsis do appear to sense and respond to mechanical barriers placed in their path of growth in a qualitatively similar fashion. Both types of roots exhibited a differential growth response upon contacting the obstacle that directed the main axis of elongation parallel to the barrier. This growth habit was maintained until the obstacle was circumvented, at which point normal gravitropic growth was resumed. Thus, the gravitational set-point angle of the primary and lateral roots prior to encountering the barrier were 95 degrees and 136 degrees respectively and after growing off the end of the obstacle identical set-point angles were reinstated. However, whilst tracking across the barrier, quantitative differences in response were observed between these two classes of roots. The root tip of the primary root maintained an angle of 136 degrees to the horizontal as it traversed the barrier whereas the lateral roots adopted an angle of 154 degrees. Thus, this root tip angle appeared dependent on the gravitropic set-point angle of the root type with the difference in tracking angle quantitatively reflecting differences in initial set-point angle. Concave and convex barriers were also used to analyze the response of the root to tracking along a continuously varying surface. The roots maintained the a fairly fixed angle to gravity on the curved surface implying a constant resetting of this tip angle

  17. Molecular identification of fine roots of trees from the Alps: reliable and fast DNA extraction and PCR-RFLP analyses of plastid DNA.

    PubMed

    Brunner, I; Brodbeck, S; Büchler, U; Sperisen, C

    2001-08-01

    Fine roots of trees are intensively used as indicators to assess soil alterations, e.g. those owing to atmospheric inputs of acidifying substances, but their identification to species with morphological criteria is difficult. In this study, we established molecular techniques in order to identify fine roots of the 30 most common tree species of the Alps. We developed a protocol for efficient isolation of DNA from fine roots with extraction of DNA in the presence of polyvinylpyrrolidone (PVP) and polyvinylpolypyrrolidone (PVPP). The trnL (UAA) intron of plastid DNA was used as a marker for fine root identification. We amplified and sequenced this intron with plant universal primers. The size of the sequences ranged from 444 to 672 bp. A synoptic key for species identification was designed on the basis of restriction fragment patterns predicted from sequence data. Using the restriction enzyme TaqI as key enzyme, and where necessary HinfI, RsaI and CfoI, 16 taxa, including Picea abies, Larix decidua, Abies alba, and Fagus sylvatica, the dominant tree species of the Alpine region could be identified by agarose gel electrophoresis of restriction fragments. Fourteen taxa could be identified to the genus level, among them Quercus, Salix and Populus species. In a field study, conducted in a 20 x 30 m plot of a mixed forest with five tree species, fine roots of 43 out of 46 samples were identified and their distributions were mapped. These results demonstrate the utility of our DNA extraction method and of the trnL intron for the identification of fine tree roots.

  18. Effects of elevated atmospheric CO[sub 2] on soybean and sorghum root growth

    SciTech Connect

    Rogers, H.H.; Prior, S.A.; Runion, G.B. )

    1993-05-01

    Aboveground plant responses to elevated CO[sub 2] concentration are well documented. However, very little is known about crop root responses to CO[sub 2] enrichment, especially under field environments. This study evaluates the effects of increased serial CO[sub 2] concentration on root systems of a C[sub 3] [soybean (Glycine max (L>) Merr.)] and C[sub 4] [sorghum (Sorghum bicolor (L.) Moench.)] crop. Plants were grown in open top field chambers under two levels of CO[sub 2]. Root systems were sampled at physiological maturity by uprooting the plant from the soil while concurrently measuring vertical pull resistance. Root variables (length, dry weight, and tissue density), except for number of roots, were significantly increased under elevated CO[sub 2]. The positive effects of extra CO[sub 2] on soybean roots partitioned into taproot and lateral roots were similar to patterns previously described. The number of soybean nodules increased under CO[sub 2]-enriched conditions, but no effect on nodule dry weight was seen. Elevated CO[sub 2] increased root dry weight more so than root length. The larger root systems observed under CO[sub 2] enrichment was reflected in an overall increase in vertical pull resistance. Several root variables exhibited significant CO[sub 2] X species interactions (except root number) with differences between CO[sub 2] levels seen with sorghum. Fine root data obtained from soil cores (30 cm) also showed that extra CO[sub 2] influenced root dry weight density more so than root length density. Under elevated CO[sub 2] conditions, root dry weight density more so than root tissue density values tended to be greater in the top 15 cm of the soil profile, but not lower in the profile (i.e., 15-30 cm). The fine root data exhibited few CO[sub 2] X species interactions. Results from this study indicate that additional atmospheric C[sub 2] will affect crop root systems.

  19. Fine Structure of Bacteroids in Root Nodules of Vigna sinensis, Acacia longifolia, Viminaria juncea, and Lupinus angustifolius

    PubMed Central

    Dart, P. J.; Mercer, F. V.

    1966-01-01

    Dart, P. J. (University of Sydney, Sydney, Australia), and F. V. Mercer. Fine structure of bacteroids in root nodules of Vigna sinensis, Acacia longifolia, Viminaria juncea, and Lupinus angustifolius. J. Bacteriol. 91:1314–1319.—In nodules of Vigna sinensis, Acacia longifolia, and Viminaria juncea, membrane envelopes enclose groups of bacteroids. The bacteroids often contain inclusion granules and electron-dense bodies, expand little during development, and retain their rod form with a compact, central nucleoid area. The membrane envelope may persist around bacteroids after host cytoplasm breakdown. In nodules of Lupinus angustifolius, the membrane envelopes enclose only one or two bacteroids, which expand noticeably during development and change from their initial rod structure. Images PMID:5929757

  20. Growth and changes of endogenous hormones of mulberry roots in a simulated rocky desertification area.

    PubMed

    Feng, Dalan; Huang, Xiaohui; Liu, Yun; Willison, J H Martin

    2016-06-01

    We studied the growth of roots of white mulberry (Morus alba) trees in response to different water and nutrient conditions in sets of three or five containers connected via small pipes and arranged so as to simulate the heterogeneous soil conditions associated with rocky desertification. The experiment was conducted to improve understanding of the adaptation of M. alba to this stressful environment. The trees were grown for a year under constant water and nutrient conditions in the soils within each container of any set of containers. Differences in root activity and endogenous hormones within root tips were measured at the end of the experiment. We compared four treatment groups: H (variable moisture among containers), F (variable nutrients among containers), HF (both moisture and nutrients varied among containers), and CK (non-varied control). Results showed the following: (1) Mulberry roots showed obvious hydrotropic and chemotropic growth patterns, but chemotropism did not occur in the condition of water shortage. (2) Measurement of growth indices (root surface area, total root length, number of root tips, root biomass) showed that growth status was best in group HF once the roots were able to access containers with sufficient water and nutrients, followed by group H. The indices were significantly poorer in groups F and CK. (3) The content of auxin, cytokinin, and gibberellins in roots under soil drought conditions were lower than under wetter soil conditions. In contrast, abscisic acid content and root activity were higher under soil drought conditions than under wetter soil conditions. The results indicated that water is the key factor restricting growth of white mulberry trees in areas of rocky desertification but that the trees adjust endogenous hormones in their roots to promote tropic growth and obtain sufficient moisture and nutrients over the long term. Moreover, under long-term drought stress conditions, mulberry trees retained high root activity

  1. Root pressurization affects growth-induced water potentials and growth in dehydrated maize leaves.

    PubMed

    Tang, An-Ching; Boyer, John S

    2003-11-01

    Profiles of water potential (Psi w) were measured from the soil to the tips of growing leaves of maize (Zea mays L.) when pressure (P) was applied to the soil/root system. At moderately low soil Psi w, leaf elongation was somewhat inhibited, large tensions existed in the xylem, and Psi w were slightly lower in the elongating leaf tissues than in the xylem, i.e. a growth-induced Psi w was present but small. With P, the tension was relieved, enlarging the difference in Psi w between the xylem and the elongating tissues, i.e. enlarging the growth-induced Psi w, which is critical for growth. Guttation occurred, confirming the high Psi w of the xylem, and the mature leaf tissue rehydrated. Water uptake increased and met the requirements of transpiration. Leaf elongation recovered to control rates. Under more severe conditions at lower soil Psi w, P induced only a brief elongation and the growth-induced Psi w responded only slightly. Guttation did not occur, water flow did not meet the requirements of transpiration, and the mature leaf tissues did not rehydrate. A rewatering experiment indicated that a low conductance existed in the severely dehydrated soil, which limited water delivery to the root and shoot. Therefore, the initial growth inhibition appeared to be hydraulic because the enlargement of the growth-induced Psi w by P together with rehydration of the mature leaf tissue were essential for growth recovery. In more severe conditions, P was ineffective because the soil could not supply water at the required rate, and metabolic factors began to contribute to the inhibition. PMID:14512379

  2. Modeling the hydraulics of root growth in three dimensions with phloem water sources.

    PubMed

    Wiegers, Brandy S; Cheer, Angela Y; Silk, Wendy K

    2009-08-01

    Primary growth is characterized by cell expansion facilitated by water uptake generating hydrostatic (turgor) pressure to inflate the cell, stretching the rigid cell walls. The multiple source theory of root growth hypothesizes that root growth involves transport of water both from the soil surrounding the growth zone and from the mature tissue higher in the root via phloem and protophloem. Here, protophloem water sources are used as boundary conditions in a classical, three-dimensional model of growth-sustaining water potentials in primary roots. The model predicts small radial gradients in water potential, with a significant longitudinal gradient. The results improve the agreement of theory with empirical studies for water potential in the primary growth zone of roots of maize (Zea mays). A sensitivity analysis quantifies the functional importance of apical phloem differentiation in permitting growth and reveals that the presence of phloem water sources makes the growth-sustaining water relations of the root relatively insensitive to changes in root radius and hydraulic conductivity. Adaptation to drought and other environmental stresses is predicted to involve more apical differentiation of phloem and/or higher phloem delivery rates to the growth zone. PMID:19542299

  3. Vigorous Root Growth Is a Better Indicator of Early Nutrient Uptake than Root Hair Traits in Spring Wheat Grown under Low Fertility

    PubMed Central

    Wang, Yaosheng; Thorup-Kristensen, Kristian; Jensen, Lars Stoumann; Magid, Jakob

    2016-01-01

    A number of root and root hair traits have been proposed as important for nutrient acquisition. However, there is still a need for knowledge on which traits are most important in determining macro- and micronutrient uptake at low soil fertility. This study investigated the variations in root growth vigor and root hair length (RHL) and density (RHD) among spring wheat genotypes and their relationship to nutrient concentrations and uptake during early growth. Six spring wheat genotypes were grown in a soil with low nutrient availability. The root and root hair traits as well as the concentration and content of macro- and micronutrients were identified. A significant genetic variability in root and root hair traits as well as nutrient uptake was found. Fast and early root proliferation and long and dense root hairs enhanced uptake of macro- and micronutrients under low soil nutrient availability. Vigorous root growth, however, was a better indicator of early nutrient acquisition than RHL and RHD. Vigorous root growth and long and dense root hairs ensured efficient acquisition of macro- and micronutrients during early growth and a high root length to shoot dry matter ratio favored high macronutrient concentrations in the shoots, which is assumed to be important for later plant development. PMID:27379145

  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. Effects of bisphenol A on growth and nitrogen nutrition of roots of soybean seedlings.

    PubMed

    Sun, Hai; Wang, Lihong; Zhou, Qing

    2013-01-01

    Bisphenol A (BPA) is an environmental endocrine disruptor that seriously threatens ecological systems. Plants are the primary producers in ecological systems, but little information is available concerning the toxic effect of BPA on plants. In the present study, the effects of BPA on the growth and nitrogen nutrition of roots of soybean seedlings were investigated by using a root automatic scan apparatus and biochemical methods. It was found that when soybean seedlings were treated with 1.5 mg/L BPA, the growth of roots was improved, the content of nitrate in roots was increased, the content of ammonium in roots was decreased, and the activities of nitrate reductase and nitrite reductase in roots were not changed. The opposite effects were observed in roots treated with 17.2 mg/L and 50.0 mg/L BPA, except for an increase in the content of nitrate in roots treated with 17.2 mg/L BPA and a decrease in the activities of nitrate reductase and nitrite reductase in roots of soybeans seedlings. Statistical analysis indicated that the change in the nitrogen nutrition of roots of soybean seedlings treated with BPA was one reason why the growth of roots was changed. The authors suggest that the potential environmental and ecological risk of BPA to plants should receive more consideration.

  6. Is there an association between root architecture and mycorrhizal growth response?

    PubMed

    Maherali, Hafiz

    2014-10-01

    The symbiosis between arbuscular mycorrhizal (AM) fungi and plants is evolutionarily widespread. The response of plant growth to inoculation by these fungi (mycorrhizal growth response; MGR) is highly variable, ranging from positive to negative. Some of this variation is hypothesized to be associated with root structure and function. Specifically, species with a coarse root architecture, and thus a limited intrinsic capacity to absorb soil nutrients, are expected to derive the greatest growth benefit from inoculation with AM fungi. To test this hypothesis, previously published literature and phylogenetic information were combined in a meta-analysis to examine the magnitude and direction of relationships among several root architectural traits and MGR. Published studies differed in the magnitude and direction of relationships between root architecture and MGR. However, when combined, the overall relationship between MGR and allocation to roots, root diameter, root hair length and root hair density did not differ significantly from zero. These findings indicate that possessing coarse roots is not necessarily a predictor of plant growth response to AM fungal colonization. Root architecture is therefore unlikely to limit the evolution of variation in MGR. PMID:25041241

  7. The influence of calcium and pH on growth in primary roots of Zea mays

    NASA Technical Reports Server (NTRS)

    Hasenstein, K. H.; Evans, M. L.

    1988-01-01

    We investigated the interaction of Ca2+ and pH on root elongation in Zea mays L. cv. B73 x Missouri 17 and cv. Merit. Seedlings were raised to contain high levels of Ca2+ (HC, imbibed and raised in 10 mM CaCl2) or low levels of Ca2+ (LC, imbibed and raised in distilled water). In HC roots, lowering the pH (5 mM MES/Tris) from 6.5 to 4.5 resulted in strong, long-lasting growth promotion. Surprisingly, increasing the pH from 6.5 to 8.5 also resulted in strong growth promotion. In LC roots acidification of the medium (pH 6.5 to 4.5) resulted in transient growth stimulation followed by a gradual decline in the growth rate toward zero. Exposure of LC roots to high pH (pH shift from 6.5 to 8.5) also promoted growth. Addition of EGTA resulted in strong growth promotion in both LC and HC roots. The ability of EGTA to stimulate growth appeared not to be related to H+ release from EGTA upon Ca2+ chelation since, 1) LC roots showed a strong and prolonged response to EGTA, but only a transient response to acid pH, and 2) promotion of growth by EGTA was observed in strongly buffered solutions. We also examined the pH dependence of the release of 45Ca2+ from roots of 3-day-old seedlings grown from grains imbibed in 45Ca2+. Release of 45Ca2+ from the root into agar blocks placed on the root surface was greater the more acidic the pH of the blocks. The results indicate that Ca2+ may be necessary for the acid growth response in roots.

  8. Touch modulates gravity sensing to regulate the growth of primary roots of Arabidopsis thaliana

    NASA Technical Reports Server (NTRS)

    Massa, Gioia D.; Gilroy, Simon

    2003-01-01

    Plants must sense and respond to diverse stimuli to optimize the architecture of their root system for water and nutrient scavenging and anchorage. We have therefore analyzed how information from two of these stimuli, touch and gravity, are integrated to direct root growth. In Arabidopsis thaliana, touch stimulation provided by a glass barrier placed across the direction of growth caused the root to form a step-like growth habit with bends forming in the central and later the distal elongation zones. This response led to the main root axis growing parallel to, but not touching the obstacle, whilst the root cap maintained contact with the barrier. Removal of the graviperceptive columella cells of the root cap using laser ablation reduced the bending response of the distal elongation zone. Similarly, although the roots of the gravisensing impaired pgm1-1 mutant grew along the barrier at the same average angle as wild-type, this angle became more variable with time. These observations imply a constant gravitropic re-setting of the root tip response to touch stimulation from the barrier. In wild-type plants, transient touch stimulation of root cap cells, but not other regions of the root, inhibited both subsequent gravitropic growth and amyloplast sedimentation in the columella. Taken together, these results suggest that the cells of the root cap sense touch stimuli and their subsequent signaling acts on the columella cells to modulate their graviresponse. This interaction of touch and gravity signaling would then direct root growth to avoid obstacles in the soil while generally maintaining downward growth.

  9. Tracking soil structural changes during root growth with sequential X-Ray CT scanning

    NASA Astrophysics Data System (ADS)

    Schmidt, Sonja; Bengough, Glyn; Hallett, Paul

    2014-05-01

    Crop productivity is highly dependent on a good supply of water and nutrients. With increasing demand for food and variable water regimes due to climate change, it is important to get a better understanding on the processes involved in water and nutrient uptake by roots. Changes in soil structure affect water and nutrient availabilities for plants. It is known that roots change their environment during growth but little is known on how soil structural properties change as roots penetrate soils. More detailed information on root growth induced changes in the rhizosphere will help us to model water and nutrient uptake by plants. The objective of this study was to measure directly how soil structure changes in close proximity to the root as a seedling root penetrates through the soil. 3D volumetric images of maize root growth during six hours were obtained using X-ray microtomography at a resolution of 21 μm. Roots were grown in soils of two different compaction levels (50 kPa and 200 kPa uniaxial load) and matric potentials (10 kPa and 100 kPa). Changes in porosity, pore connectivity and root-soil contact were determined from 2D cross sections for each time step. The 2D cross sections were chosen at 4 different positions in the sample, and each section was divided into sections of 64 voxels (1.3 mm2) to determine changes in porosity and connectivity with distance from the root. Soil movement caused by root growth was quantified from 2D cross sections at different positions along the sample using Particle image velocimetry (PIV). Changes in soil structure during root growth were observed. Porosity in close proximity to the root decreased whereas root-soil contact increased with time. The PIV showed a radial deformation of the soil. Greatest deformation was found close to the root. Some aggregates fractured during root growth whereas others were pushed into the pore space. These data on the changes in soil structure will help us to predict water and nutrient

  10. Nitrogen source interacts with ROP signalling in root hair tip-growth.

    PubMed

    Bloch, Daria; Monshausen, Gabriele; Singer, Meromit; Gilroy, Simon; Yalovsky, Shaul

    2011-01-01

    Root hairs elongate in a highly polarized manner known as tip growth. Overexpression of constitutively active Rho of Plant (ROP)/RAC GTPases mutants induces swelling of root hairs. Here, we demonstrate that Atrop11(CA)-induced swelling of root hairs depends on the composition of the growth medium. Depletion of ammonium allowed normal root hair elongation in Atrop11(CA) plants, induced the development of longer root hairs in wild-type plants and suppressed the effect of Atrop11(CA) expression on actin organization and reactive oxygen species distribution, whereas membrane localization of the protein was not affected. Ammonium at concentrations higher than 1 mM and the presence of nitrate were required for induction of swelling. Oscillations in wall and cytoplasmic pH are known to accompany tip growth in root hairs, and buffering of the growth medium decreased Atrop11(CA)-induced swelling. Fluorescence ratio imaging experiments revealed that in wild-type root hairs, the addition of NH₄NO₃ to the growth medium induced an increase in the amplitude of extracellular and intracellular pH oscillations and an overall decrease in cytoplasmic pH at the cell apex. Based on these results, we suggest a model in which ROP GTPases and nitrogen-dependent pH oscillations function in parallel pathways, creating a positive feedback loop during root hair growth.

  11. Cytokinin-dependent secondary growth determines root biomass in radish (Raphanus sativus L.).

    PubMed

    Jang, Geupil; Lee, Jung-Hun; Rastogi, Khushboo; Park, Suhyoung; Oh, Sang-Hun; Lee, Ji-Young

    2015-08-01

    The root serves as an essential organ in plant growth by taking up nutrients and water from the soil and supporting the rest of the plant body. Some plant species utilize roots as storage organs. Sweet potatoes (Ipomoea batatas), cassava (Manihot esculenta), and radish (Raphanus sativus), for example, are important root crops. However, how their root growth is regulated remains unknown. In this study, we characterized the relationship between cambium and radial root growth in radish. Through a comparative analysis with Arabidopsis root expression data, we identified putative cambium-enriched transcription factors in radish and analysed their expression in representative inbred lines featuring distinctive radial growth. We found that cell proliferation activities in the cambium positively correlated with radial growth and final yields of radish roots. Expression analysis of candidate transcription factor genes revealed that some genes are differentially expressed between inbred lines and that the difference is due to the distinct cytokinin response. Taken together, we have demonstrated for the first time, to the best of our knowledge, that cytokinin-dependent radial growth plays a key role in the yields of root crops. PMID:25979997

  12. Cytokinin-dependent secondary growth determines root biomass in radish (Raphanus sativus L.).

    PubMed

    Jang, Geupil; Lee, Jung-Hun; Rastogi, Khushboo; Park, Suhyoung; Oh, Sang-Hun; Lee, Ji-Young

    2015-08-01

    The root serves as an essential organ in plant growth by taking up nutrients and water from the soil and supporting the rest of the plant body. Some plant species utilize roots as storage organs. Sweet potatoes (Ipomoea batatas), cassava (Manihot esculenta), and radish (Raphanus sativus), for example, are important root crops. However, how their root growth is regulated remains unknown. In this study, we characterized the relationship between cambium and radial root growth in radish. Through a comparative analysis with Arabidopsis root expression data, we identified putative cambium-enriched transcription factors in radish and analysed their expression in representative inbred lines featuring distinctive radial growth. We found that cell proliferation activities in the cambium positively correlated with radial growth and final yields of radish roots. Expression analysis of candidate transcription factor genes revealed that some genes are differentially expressed between inbred lines and that the difference is due to the distinct cytokinin response. Taken together, we have demonstrated for the first time, to the best of our knowledge, that cytokinin-dependent radial growth plays a key role in the yields of root crops.

  13. Field and laboratory root growth and development of Lesquerella germplasm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lesquerella roots have not been fully characterized as compared to other crop species. There is initial information gathered on root trait variation in young seedling grown in laboratory settings but studies to determine if the results can be extrapolated in field grown plants are lacking. We report...

  14. Growth Dynamics of Mechanically Impeded Lupin Roots: does Altered Morphology Induce Hypoxia?

    PubMed Central

    HANBURY, COLIN D.; ATWELL, BRIAN J.

    2005-01-01

    • Background and Aims Root axes elongate slowly and swell radially under mechanical impedance. However, temporal and spatial changes to impeded root apices have only been described qualitatively. This paper aims (a) to quantify morphological changes to root apices and (b) assess whether these changes pre-dispose young root tissues to hypoxia. • Methods Lupin (Lupinus angustifolius) seedlings were grown into coarse sand that was pressurized through a diaphragm to generate mechanical impedance on growing root axes. In situ observations yielded growth rates and root response to hypoxia. Roots were then removed to assess morphology, cell lengths and local growth velocities. Oxygen uptake into excised segments was measured. • Key Results An applied pressure of 15 kPa slowed root extension by 75 % after 10–20 h while the same axes thickened by about 50 %. The most terminal 2–3 mm of axes did not respond morphologically to impedance, in spite of the slower flux of cells out of this region. The basal boundary of root extension encroached to within 4 mm of the apex (cf. 10 mm in unimpeded roots), while radial swelling extended 10 mm behind the apex in impeded roots. Oxygen demand by segments of these short, thick, impeded roots was significantly different from segments of unimpeded roots when the zones of elongation in each treatment were compared. Specifically, impeded roots consumed O2 faster and O2 consumption was more likely to be O2-limited over a substantial proportion of the elongation zone, making these roots more susceptible to O2 deficit. Impeded roots used more O2 per unit growth (measured as either unit of elongation or unit of volumetric expansion) than unimpeded roots. Extension of impeded roots in situ was O2-limited at sub-atmospheric O2 levels (21 % O2), while unimpeded roots were only limited below 11 % O2. • Conclusions The shift in the zone of extension towards the apex in impeded roots coincided with greater vulnerability to

  15. Analysis of root growth from a phenotyping data set using a density-based model.

    PubMed

    Kalogiros, Dimitris I; Adu, Michael O; White, Philip J; Broadley, Martin R; Draye, Xavier; Ptashnyk, Mariya; Bengough, A Glyn; Dupuy, Lionel X

    2016-02-01

    Major research efforts are targeting the improved performance of root systems for more efficient use of water and nutrients by crops. However, characterizing root system architecture (RSA) is challenging, because roots are difficult objects to observe and analyse. A model-based analysis of RSA traits from phenotyping image data is presented. The model can successfully back-calculate growth parameters without the need to measure individual roots. The mathematical model uses partial differential equations to describe root system development. Methods based on kernel estimators were used to quantify root density distributions from experimental image data, and different optimization approaches to parameterize the model were tested. The model was tested on root images of a set of 89 Brassica rapa L. individuals of the same genotype grown for 14 d after sowing on blue filter paper. Optimized root growth parameters enabled the final (modelled) length of the main root axes to be matched within 1% of their mean values observed in experiments. Parameterized values for elongation rates were within ±4% of the values measured directly on images. Future work should investigate the time dependency of growth parameters using time-lapse image data. The approach is a potentially powerful quantitative technique for identifying crop genotypes with more efficient root systems, using (even incomplete) data from high-throughput phenotyping systems.

  16. Analysis of root growth from a phenotyping data set using a density-based model.

    PubMed

    Kalogiros, Dimitris I; Adu, Michael O; White, Philip J; Broadley, Martin R; Draye, Xavier; Ptashnyk, Mariya; Bengough, A Glyn; Dupuy, Lionel X

    2016-02-01

    Major research efforts are targeting the improved performance of root systems for more efficient use of water and nutrients by crops. However, characterizing root system architecture (RSA) is challenging, because roots are difficult objects to observe and analyse. A model-based analysis of RSA traits from phenotyping image data is presented. The model can successfully back-calculate growth parameters without the need to measure individual roots. The mathematical model uses partial differential equations to describe root system development. Methods based on kernel estimators were used to quantify root density distributions from experimental image data, and different optimization approaches to parameterize the model were tested. The model was tested on root images of a set of 89 Brassica rapa L. individuals of the same genotype grown for 14 d after sowing on blue filter paper. Optimized root growth parameters enabled the final (modelled) length of the main root axes to be matched within 1% of their mean values observed in experiments. Parameterized values for elongation rates were within ±4% of the values measured directly on images. Future work should investigate the time dependency of growth parameters using time-lapse image data. The approach is a potentially powerful quantitative technique for identifying crop genotypes with more efficient root systems, using (even incomplete) data from high-throughput phenotyping systems. PMID:26880747

  17. Vegetative growth and cluster development in Shiraz grapevines subjected to partial root-zone cooling.

    PubMed

    Rogiers, Suzy Y; Clarke, Simon J

    2013-01-01

    Heterogeneity in root-zone temperature both vertically and horizontally may contribute to the uneven vegetative and reproductive growth often observed across vineyards. An experiment was designed to assess whether the warmed half of a grapevine root zone could compensate for the cooled half in terms of vegetative growth and reproductive development. We divided the root system of potted Shiraz grapevines bilaterally and applied either a cool or a warm treatment to each half from budburst to fruit set. Shoot growth and inflorescence development were monitored over the season. Simultaneous cooling and warming of parts of the root system decreased shoot elongation, leaf emergence and leaf expansion below that of plants with a fully warmed root zone, but not to the same extent as those with a fully cooled root zone. Inflorescence rachis length, flower number and berry number after fertilization were smaller only in those vines exposed to fully cooled root zones. After terminating the treatments, berry enlargement and the onset of veraison were slowed in those vines that had been exposed to complete or partial root-zone cooling. Grapevines exposed to partial root-zone cooling were thus delayed in vegetative and reproductive development, but the inhibition was greater in those plants whose entire root system had been cooled.

  18. Rates of Root and Organism Growth, Soil Conditions, and Temporal and Spatial Development of the Rhizosphere

    PubMed Central

    WATT, MICHELLE; SILK, WENDY K.; PASSIOURA, JOHN B.

    2006-01-01

    • Background Roots growing in soil encounter physical, chemical and biological environments that influence their rhizospheres and affect plant growth. Exudates from roots can stimulate or inhibit soil organisms that may release nutrients, infect the root, or modify plant growth via signals. These rhizosphere processes are poorly understood in field conditions. • Scope and Aims We characterize roots and their rhizospheres and rates of growth in units of distance and time so that interactions with soil organisms can be better understood in field conditions. We review: (1) distances between components of the soil, including dead roots remnant from previous plants, and the distances between new roots, their rhizospheres and soil components; (2) characteristic times (distance2/diffusivity) for solutes to travel distances between roots and responsive soil organisms; (3) rates of movement and growth of soil organisms; (4) rates of extension of roots, and how these relate to the rates of anatomical and biochemical ageing of root tissues and the development of the rhizosphere within the soil profile; and (5) numbers of micro-organisms in the rhizosphere and the dependence on the site of attachment to the growing tip. We consider temporal and spatial variation within the rhizosphere to understand the distribution of bacteria and fungi on roots in hard, unploughed soil, and the activities of organisms in the overlapping rhizospheres of living and dead roots clustered in gaps in most field soils. • Conclusions Rhizosphere distances, characteristic times for solute diffusion, and rates of root and organism growth must be considered to understand rhizosphere development. Many values used in our analysis were estimates. The paucity of reliable data underlines the rudimentary state of our knowledge of root–organism interactions in the field. PMID:16551700

  19. [Effects of cinnamic acid and vanillin on grafted eggplant root growth and physiological characteristics].

    PubMed

    Chen, Shao-Li; Zhou, Bao-Li; Lin, Shan-Shan; Li, Xia; Ye, Xue-Ling

    2010-06-01

    Choosing Solanum torvum as rootstock and cultivated Xi'anlü eggplant as scion, a pot culture experiment was conducted to study the effects of autotoxic substances (cinnamic acid and vanillin) on the root growth, antioxidase activity, and osmoregulation substances content of grafted eggplant, own-rooted eggplant, and rootstock eggplant. Cinnamic acid and vanillin had allelopathic effects on the root system of test eggplants, with low concentration promoting and higher concentration inhibiting the root growth and physiological metabolism. For own-rooted eggplant, the critical concentration of cinnamic acid and vanillin for promotion or inhibition was 0.1 mmol x kg(-1) and 0.5 mmol x kg(-1), respectively; whereas for grafted and rootstock eggplants, it was 0.5 mmol x kg(-1) and 1 mmol x kg(-1), respectively. The root resistance to autotoxic substances was in the order of root-stock eggplant > grafted eggplant > own-rooted eggplant. Higher concentration cinamic acid (0.5-4 mmol x kg(-1)) and vanillin (1-4 mmol x kg(-1)) enhanced the SOD enzyme activity and the proline and soluble sugar contents of grafted eggplant root by 8.50%-24.50%; 9.39%-27.64%, and 12.77%-81.81%, respectively, compared with own-rooted eggplant. The soluble protein content, fresh mass, dry mass, and root activity of grafted eggplant roots were significantly higher than those of own-rooted eggplant, suggesting that grafted eggplant had a strong resistance of rootstocks to autotoxic substances, which alleviated the negative effect of autotoxic substances on root growth.

  20. Low temperature inhibits root growth by reducing auxin accumulation via ARR1/12.

    PubMed

    Zhu, Jiang; Zhang, Kun-Xiao; Wang, Wen-Shu; Gong, Wen; Liu, Wen-Cheng; Chen, Hong-Guo; Xu, Heng-Hao; Lu, Ying-Tang

    2015-04-01

    Plants exhibit reduced root growth when exposed to low temperature; however, how low temperature modulates root growth remains to be understood. Our study demonstrated that low temperature reduces both meristem size and cell number, repressing the division potential of meristematic cells by reducing auxin accumulation, possibly through the repressed expression of PIN1/3/7 and auxin biosynthesis-related genes, although the experiments with exogenous auxin application also suggest the involvement of other factor(s). In addition, we verified that ARABIDOPSIS RESPONSE REGULATOR 1 (ARR1) and ARR12 are involved in low temperature-mediated inhibition of root growth by showing that the roots of arr1-3 arr12-1 seedlings were less sensitive than wild-type roots to low temperature, in terms of changes in root length and meristem cell number. Furthermore, low temperature reduced the levels of PIN1/3 transcripts and the auxin level to a lesser extent in arr1-3 arr12-1 roots than in wild-type roots, suggesting that cytokinin signaling is involved in the low-temperature-mediated reduction of auxin accumulation. Taken together, our data suggest that low temperature inhibits root growth by reducing auxin accumulation via ARR1/12.

  1. Salt-stress regulation of root system growth and architecture in Arabidopsis seedlings.

    PubMed

    Duan, Lina; Sebastian, Jose; Dinneny, Jose R

    2015-01-01

    In order to acclimate to the soil environment, plants need to constantly optimize their root system architecture for efficient resource uptake. Roots are highly sensitive to changes in their surrounding environment and root system responses to a stress such as salinity and drought can be very dynamic and complex in nature. These responses can be manifested differentially at the cellular, tissue, or organ level and between the types of roots in a root system. Therefore, various approaches must be taken to quantify and characterize these responses. In this chapter, we review methods to study basic root growth traits, such as root length, cell cycle activity and meristem size, cell shape and size that form the basis for the emergent properties of the root system. Methods for the detailed analysis of lateral root initiation and postemergence growth are described. Finally, several live-imaging systems, which allow for dynamic imaging of the root, will be explored. Together these tools provide insight into the regulatory steps that sculpt the root system upon environmental change and can be used as the basis for the evaluation of genetic variation affecting these pathways. PMID:25408448

  2. Effect of soil frost on growing season nitrogen uptake by fine roots of mature trees in northern hardwood forests of the United States

    NASA Astrophysics Data System (ADS)

    Socci, A. M.; Templer, P. H.

    2010-12-01

    Forests of the northeastern United States are predicted to experience a decrease in the depth and duration of the winter snowpack over the next 100 years. Even when coupled with warmer winter air temperatures, the absence of snow as insulation can increase soil frost during the winter months. Past research has determined that there are species-level effects of soil frost on dominant forest trees. For example, in stands dominated by sugar maple (Acer saccharum), induced soil frost led to increased fine root mortality and soil nitrate leaching. Soil frost also increased fine root mortality in stands dominated by yellow birch (Betula allegheniensis), but there was no significant change in leaching of soil nitrate. We hypothesized that greater nitrogen (N) losses from stands dominated by sugar maple may be due to reduced N uptake by fine roots of this tree species. To determine the impact of increased soil freezing on fine root uptake of N, we established a snow manipulation experiment in mixed sugar maple/American beech (Fagus grandifolia) forests at the Hubbard Brook Experimental Forest in New Hampshire (n=4 paired snow-removal and reference plots; each 13m X 13m). Snow removal occurred during the first six weeks of winter over two years. During each growing season following snow removal, we used the N depletion technique to measure in situ rates of uptake of ammonium and nitrate by fine roots of sugar maple during the early, peak and late growing season. Among all sampling dates and plots, we observed significantly lower uptake of N as nitrate compared to ammonium. During the first growing season, at moderate ammonium availability (35 μM N) we observed significantly less uptake of ammonium by fine roots of sugar maple in the snow removal plots relative to the reference plots during the early growing season (April-May), with no significant differences in uptake of ammonium during the peak (July) and late (September) growing season. We observed no differences in

  3. The use of stored carbon reserves in growth of temperate tree roots and leaf buds: Analyses using radiocarbon measurements and modeling

    SciTech Connect

    Gaudinski, J.B.; Torn, M.S.; Riley, W.J.; Swanston, C.; Trumbore, S.E.; Joslin, J.D.; Majdi, H.; Dawson, T.E.; Hanson, P.J.

    2009-02-01

    Characterizing the use of carbon (C) reserves in trees is important for understanding regional and global C cycles, stress responses, asynchrony between photosynthetic activity and growth demand, and isotopic exchanges in studies of tree physiology and ecosystem C cycling. Using an inadvertent, whole-ecosystem radiocarbon ({sup 14}C) release in a temperate deciduous oak forest and numerical modeling, we estimated that the mean age of stored C used to grow both leaf buds and new roots is 0.7 years and about 55% of new-root growth annually comes from stored C. Therefore, the calculated mean age of C used to grow new-root tissue is {approx}0.4 years. In short, new roots contain a lot of stored C but it is young in age. Additionally, the type of structure used to model stored C input is important. Model structures that did not include storage, or that assumed stored and new C mixed well (within root or shoot tissues) before being used for root growth, did not fit the data nearly as well as when a distinct storage pool was used. Consistent with these whole-ecosystem labeling results, the mean age of C in new-root tissues determined using 'bomb-{sup 14}C' in three additional forest sites in North America and Europe (one deciduous, two coniferous) was less than 1-2 years. The effect of stored reserves on estimated ages of fine roots is unlikely to be large in most natural abundance isotope studies. However, models of root C dynamics should take stored reserves into account, particularly for pulse-labeling studies and fast-cycling roots (<1 years).

  4. Mycorrhizal populations and fine root development on Norway spruce exposed to controlled doses of gaseous pollutants and simulated acidic rain treatments.

    PubMed

    Blaschke, H

    1990-01-01

    Effects after long-term fumigation and simulated acidic rain (pH 4.0) treatment in open-top chambers (OTC) during 5 vegetation periods on ectomycorrhizal (EM) frequency, fine root structure and distribution of short roots were recorded for Norway spruce. Simultaneous application of ozone and SO(2) resulted in a significant decrease (P< or =0.01) in the proportion of EM root tips and an increase in the numbers of necrotic short roots. The observed differences were partly due to more than additive effects of ozone and SO(2). On the basis of EM and non-mycorrhizal (NM) short roots in the irrigated controls (OTC-V, pH 5.6, Ah-horizon: EM + NM/cm=0.05) the acid treatments resulted in drastic effects (P< or =0.05) on the branching density and the proportion of EM root tips and NM short roots. Relative numbers of short roots infected by indigenous EM fungi with trees in the fumigation treatments at pH 4.0 were similar: 1.5-1.9 EM tips/cm and differed noticeably from the control: 5.2 EM tips/cm. Again, increasing numbers of necrotic and NM short roots were noted. Parallel measurements by the ingrowth-core technique confirm the argument, that EM formation seems to be a reliable indicator of pollution-induced stress.

  5. Myosin XIK of Arabidopsis thaliana accumulates at the root hair tip and is required for fast root hair growth.

    PubMed

    Park, Eunsook; Nebenführ, Andreas

    2013-01-01

    Myosin motor proteins are thought to carry out important functions in the establishment and maintenance of cell polarity by moving cellular components such as organelles, vesicles, or protein complexes along the actin cytoskeleton. In Arabidopsis thaliana, disruption of the myosin XIK gene leads to reduced elongation of the highly polar root hairs, suggesting that the encoded motor protein is involved in this cell growth. Detailed live-cell observations in this study revealed that xik root hairs elongated more slowly and stopped growth sooner than those in wild type. Overall cellular organization including the actin cytoskeleton appeared normal, but actin filament dynamics were reduced in the mutant. Accumulation of RabA4b-containing vesicles, on the other hand, was not significantly different from wild type. A functional YFP-XIK fusion protein that could complement the mutant phenotype accumulated at the tip of growing root hairs in an actin-dependent manner. The distribution of YFP-XIK at the tip, however, did not match that of the ER or several tip-enriched markers including CFP-RabA4b. We conclude that the myosin XIK is required for normal actin dynamics and plays a role in the subapical region of growing root hairs to facilitate optimal growth.

  6. Corn-on-a-chip: Mini-channel Device for Corn Root Growth

    NASA Astrophysics Data System (ADS)

    Kreis, Kevin; Ryu, Sangjin

    2015-11-01

    Plant growth heavily relies on interactions between the root and the soil environment, but it is impossible to observe such interactions because of opaqueness of soil. Microfluidics has been successfully utilized to monitor the root growth behaviors of Arabidopsis. In this study we have chosen Maize as a model plant because of its economic significance, and aim to develop transparent mini-channel devices accommodating the root growth of corn seedlings in a controlled environment. To mimic aspects of the soil environment, we try to impose concentration gradients of key chemical ions to the growing root using the device, and to investigate how the root responds to the applied stimuli. We acknowledge support from NASA Nebraska Space Grant Fellowship.

  7. Auxin, the organizer of the hormonal/environmental signals for root hair growth.

    PubMed

    Lee, Richard D-W; Cho, Hyung-Taeg

    2013-01-01

    The root hair development is controlled by diverse factors such as fate-determining developmental cues, auxin-related environmental factors, and hormones. In particular, the soil environmental factors are important as they maximize their absorption by modulating root hair development. These environmental factors affect the root hair developmental process by making use of diverse hormones. These hormonal factors interact with each other to modulate root hair development in which auxin appears to form the most intensive networks with the pathways from environmental factors and hormones. Moreover, auxin action for root hair development is genetically located immediately upstream of the root hair-morphogenetic genes. These observations suggest that auxin plays as an organizing node for environmental/hormonal pathways to modulate root hair growth. PMID:24273547

  8. Auxin, the organizer of the hormonal/environmental signals for root hair growth

    PubMed Central

    Lee, Richard D.-W.; Cho, Hyung-Taeg

    2013-01-01

    The root hair development is controlled by diverse factors such as fate-determining developmental cues, auxin-related environmental factors, and hormones. In particular, the soil environmental factors are important as they maximize their absorption by modulating root hair development. These environmental factors affect the root hair developmental process by making use of diverse hormones. These hormonal factors interact with each other to modulate root hair development in which auxin appears to form the most intensive networks with the pathways from environmental factors and hormones. Moreover, auxin action for root hair development is genetically located immediately upstream of the root hair-morphogenetic genes. These observations suggest that auxin plays as an organizing node for environmental/hormonal pathways to modulate root hair growth. PMID:24273547

  9. Root responses to soil physical conditions; growth dynamics from field to cell.

    PubMed

    Bengough, A Glyn; Bransby, M Fraser; Hans, Joachim; McKenna, Stephen J; Roberts, Tim J; Valentine, Tracy A

    2006-01-01

    Root growth in the field is often slowed by a combination of soil physical stresses, including mechanical impedance, water stress, and oxygen deficiency. The stresses operating may vary continually, depending on the location of the root in the soil profile, the prevailing soil water conditions, and the degree to which the soil has been compacted. The dynamics of root growth responses are considered in this paper, together with the cellular responses that underlie them. Certain root responses facilitate elongation in hard soil, for example, increased sloughing of border cells and exudation from the root cap decreases friction; and thickening of the root relieves stress in front of the root apex and decreases buckling. Whole root systems may also grow preferentially in loose versus dense soil, but this response depends on genotype and the spatial arrangement of loose and compact soil with respect to the main root axes. Decreased root elongation is often accompanied by a decrease in both cell flux and axial cell extension, and recent computer-based models are increasing our understanding of these processes. In the case of mechanical impedance, large changes in cell shape occur, giving rise to shorter fatter cells. There is still uncertainty about many aspects of this response, including the changes in cell walls that control axial versus radial extension, and the degree to which the epidermis, cortex, and stele control root elongation. Optical flow techniques enable tracking of root surfaces with time to yield estimates of two-dimensional velocity fields. It is demonstrated that these techniques can be applied successfully to time-lapse sequences of confocal microscope images of living roots, in order to determine velocity fields and strain rates of groups of cells. In combination with new molecular approaches this provides a promising way of investigating and modelling the mechanisms controlling growth perturbations in response to environmental stresses.

  10. [Effects of microcystins on growth and antioxidant system of rice roots].

    PubMed

    Wang, Wei-Min; Deng, Yu; Zou, Hua; Liang, Chan-Juan

    2014-04-01

    The effect of different concentrations (1, 100, 1000 and 3 000 microg x L(-1)) of microcystins (MCs) on growth, absorb activity, antioxidant system and its accumulation in roots of rice seedlings were studied. The results show that MCs accumulation was positively correlated with MCs concentration. After the treatment with 1 microg x L(-1) MCs, the root growth and activity increased. Meanwhile, catalase (CAT) activity was increased to maintain H2O2 at normal levels. After the treatment with 100 microg x L(-1) MCs, the root growth and activity were inhibited whereas CAT had no obvious change. High concentrations (1000 microg x L(-1) and 3000 microg x L(-1)) of MCs not only inhibited root growth and activity, but decreased CAT activity, leading to excessive H2O2 accumulation and membrane peroxidation. After a 7-day recovery, MCs accumulations in roots in all treatment groups were all lower than those measured during the stress period. For the 100 microg x L(-1) MCs treated group, the inhibition on root growth and root activity, and membrane peroxidation were alleviated, better than those measured during the stress period. However, for 1000 microg x L(-1) and 3000 microg x L(-1) MCs treated groups, inhibition on root growth, root activity, and CAT activity were heavier than those during the stress period, and oxidation stress intensified further, indicating that the damage caused by high concentrations (1 000 microg x L(-1) and 3000 microg x L(-1)) of MCs on rice roots was irreversible. PMID:24946604

  11. Growth and Movement of Spot Inoculated Rhizobium meliloti on the Root Surface of Alfalfa 1

    PubMed Central

    Caetano-Anollés, Gustavo; Wrobel-Boerner, Elizabeth; Bauer, Wolfgang D.

    1992-01-01

    Inoculum droplets of approximately 10 nanoliter volume and containing about 10 Rhizobium meliloti cells were placed onto the root surface of alfalfa seedlings in plastic growth pouches at either the root tip, the position of the smallest emergent root hairs, or at a site midway between these points. The droplets were initially confined to an area of about 0.2 square millimeter at the point of application. By 48 and 96 hours after inoculation, the inoculum bacteria and their progeny were distributed over several centimeters of the root between the initial site of deposition and the growing root tip, reaching densities of 103 to 104 bacteria per centimeter near the site of initial deposition and decreasing exponentially from that point toward the root tip. Graphite particles deposited on the root surface close to the growing tip were similarly distributed along the root length by 48 and 96 hours, suggesting that passive displacement by root cell elongation was primarily responsible for the spread of bacteria. A nonmotile mutant of R. meliloti colonized alfalfa roots to the same extent as the wild type and was usually distributed in the same manner, indicating that bacterial motility contributed little under these conditions to long distance spread of the bacteria. However, when applied in low numbers, R. meliloti mutants defective in motility or chemotaxis were considerably less efficient in initiating nodules near the point of inoculation than the wild type. This implies that motility and/or chemotaxis contribute significantly to local exploration for suitable infection sites. Almost all nodules on the primary root formed within a few millimeters of the spot-inoculation site, indicating that, under our experimental conditions, movement and multiplication of R. meliloti on the root surface were not sufficient to maintain an adequate population in the infectible region of the root during root growth. PMID:16668744

  12. Combined effects of bisphenol A and cadmium on growth and nitrate assimilation of soybean seedling roots.

    PubMed

    Sun, Zhaoguo; Wang, Lihong; Wang, Qingqing; Zhou, Qing; Huang, Xiaohua

    2014-09-01

    Bisphenol A (BPA) and cadmium (Cd) pollution exist simultaneously in many regions. However, little information is available regarding the combined effects of BPA and Cd pollution on plants. Plant roots are in direct contact with the soil, which is an important compartment of BPA and Cd. In the present study, the effects of combined BPA and Cd pollution on soybean seedling roots were evaluated in pot experiments. Combined treatment with BPA and Cd at low concentrations (1.5 mg/kg BPA and 0.2 mg/kg Cd) improved soybean seedling root growth. However, other combined BPA and Cd treatments, including combined treatment with BPA (Cd) at the low concentration and Cd (BPA) at the high concentration as well as combined treatment with BPA and Cd at the high concentration, inhibited soybean seedling root growth. The improvement or inhibition of soybean seedling root growth was greater in the combined BPA and Cd treatments than in single treatments. The effects of the combined BPA and Cd treatments on root growth resulted from changes in nitrate assimilation. In addition, the combined effects of BPA and Cd on the nitrate and ammonium contents in roots are discussed. The present research provides a basic understanding of the combined effects of BPA and Cd pollution on plant roots.

  13. Modeling potato root and shoot growth under drought and nutrient stress

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Simulating root growth is critical to understand nutrient and water uptake dynamics of major crops, and to improve agricultural decision support tools for natural resource management. Plants invest more assimilated carbon into their root system when under stress in order to explore a greater soil vo...

  14. Growth and microtubule orientation of Zea mays roots subjected to osmotic stress

    NASA Technical Reports Server (NTRS)

    Blancaflor, E. B.; Hasenstein, K. H.

    1995-01-01

    Previous work has shown that microtubule (MT) reorientation follows the onset of growth inhibition on the lower side of graviresponding roots, indicating that growth reduction can occur independently of MT reorientation. To test this observation further, we examined whether the reduction in growth in response to osmotic stress is correlated with MT reorientation. The distribution and rate of growth in maize roots exposed to 350 mOsm sorbitol and KCl or 5 mM Mes/Tris buffer were measured with a digitizer. After various times roots were processed for indirect immunofluorescence microscopy. Application of sorbitol or KCl had no effect on the organization of MTs in the apical 2 mm of the root but resulted in striking and different effects in the basal region of the root. Sorbitol treatment caused rapid appearance of oval to circular holes in the microtubular array that persisted for at least 9 h. Between 30 min and 4 h of submersion in KCl, MTs in cortical cells 4 mm and farther from the quiescent center began to reorient oblique to the longitudinal axis. After 9 h, the alignment of MTs had shifted to parallel to the root axis but MTs of the epidermal cells remained transverse. In KCl-treated roots MT reorientation appeared to follow a pattern of development similar to that in controls but without elongation. Our data provide additional evidence that MT reorientation is not the cause but a consequence of growth inhibition.

  15. Root Growth Reacts Rapidly and More Pronounced Than Shoot Growth Towards Increasing Light Intensity in Tobacco Seedlings

    PubMed Central

    Nagel, Kerstin A

    2006-01-01

    Light intensity is crucial for plant growth and often fluctuates on a small time scale due to altering climate conditions or sunflecks. Recently, we performed a study that looked into the growth effect of a sudden elevation of light intensity on Nicotiana tabacum seedlings.1 It was shown that an increase in light intensity leads to a pronounced increase of root-shoot-ratio as root growth reacts strongly and rapidly to an increase of light intensity. In transition experiments from low (60 µmol m−2 s−1) to high (300 µmol m−2 s−1) light intensity, root growth increased by a factor of four within four days, reaching the steady-state level measured in plants that were cultivated in high-light conditions. During the first three hours after light increase, strong fluctuations of the velocity of the root tip were observed that were putatively caused by a superposition of hydraulic and photosynthetic acclimation to the altered conditions. Experiments with externally applied sucrose and with transgenic plants having reduced capacity for sucrose synthesis indicated clearly that increasing light intensity rapidly enhanced root growth by elevating sucrose export from shoot to root. PMID:19704663

  16. Phytotoxic cyanamide affects maize (Zea mays) root growth and root tip function: from structure to gene expression.

    PubMed

    Soltys, Dorota; Rudzińska-Langwald, Anna; Kurek, Wojciech; Szajko, Katarzyna; Sliwinska, Elwira; Bogatek, Renata; Gniazdowska, Agnieszka

    2014-05-01

    Cyanamide (CA) is a phytotoxic compound produced by four Fabaceae species: hairy vetch, bird vetch, purple vetch and black locust. Its toxicity is due to complex activity that involves the modification of both cellular structures and physiological processes. To date, CA has been investigated mainly in dicot plants. The goal of this study was to investigate the effects of CA in the restriction of the root growth of maize (Zea mays), representing the monocot species. CA (3mM) reduced the number of border cells in the root tips of maize seedlings and degraded their protoplasts. However, CA did not induce any significant changes in the organelle structure of other root cells, apart from increased vacuolization. CA toxicity was also demonstrated by its effect on cell cycle activity, endoreduplication intensity, and modifications of cyclins CycA2, CycD2, and histone HisH3 gene expression. In contrast, the arrangement of microtubules was not altered by CA. Treatment of maize seedlings with CA did not completely arrest mitotic activity, although the frequency of dividing cells was reduced. Furthermore, prolonged CA treatment increased the proportion of endopolyploid cells in the root tip. Cytological malformations were accompanied by an induction of oxidative stress in root cells, which manifested as enhanced accumulation of H2O2. Exposure of maize seedlings to CA resulted in an increased concentration of auxin and stimulated ethylene emission. Taken together, these findings suggested that the inhibition of root growth by CA may be a consequence of stress-induced morphogenic responses.

  17. Phytotoxic cyanamide affects maize (Zea mays) root growth and root tip function: from structure to gene expression.

    PubMed

    Soltys, Dorota; Rudzińska-Langwald, Anna; Kurek, Wojciech; Szajko, Katarzyna; Sliwinska, Elwira; Bogatek, Renata; Gniazdowska, Agnieszka

    2014-05-01

    Cyanamide (CA) is a phytotoxic compound produced by four Fabaceae species: hairy vetch, bird vetch, purple vetch and black locust. Its toxicity is due to complex activity that involves the modification of both cellular structures and physiological processes. To date, CA has been investigated mainly in dicot plants. The goal of this study was to investigate the effects of CA in the restriction of the root growth of maize (Zea mays), representing the monocot species. CA (3mM) reduced the number of border cells in the root tips of maize seedlings and degraded their protoplasts. However, CA did not induce any significant changes in the organelle structure of other root cells, apart from increased vacuolization. CA toxicity was also demonstrated by its effect on cell cycle activity, endoreduplication intensity, and modifications of cyclins CycA2, CycD2, and histone HisH3 gene expression. In contrast, the arrangement of microtubules was not altered by CA. Treatment of maize seedlings with CA did not completely arrest mitotic activity, although the frequency of dividing cells was reduced. Furthermore, prolonged CA treatment increased the proportion of endopolyploid cells in the root tip. Cytological malformations were accompanied by an induction of oxidative stress in root cells, which manifested as enhanced accumulation of H2O2. Exposure of maize seedlings to CA resulted in an increased concentration of auxin and stimulated ethylene emission. Taken together, these findings suggested that the inhibition of root growth by CA may be a consequence of stress-induced morphogenic responses. PMID:24709147

  18. Auxin, ethylene and the regulation of root growth under mechanical impedance

    NASA Astrophysics Data System (ADS)

    Sharma, Rameshwar; Santisree, Parankusam; Nongmaithem, Sapana; Sreelakshmi, Yellamaraju

    2012-07-01

    Among the multitude functions performed by plant roots, little information is available about the mechanisms that allow roots to overcome the soil resistance, in order to grow in the soil to obtain water and nutrient. Tomato (Solanum lycopersicum) seedlings grown on horizontally placed agar plates showed a progressive decline in the root length with the increasing impedance of agar media. The incubation with 1-methylcyclopropane (1-MCP), an inhibitor of ethylene perception, led to aerial growth of roots. In contrast, in absence of 1-MCP control roots grew horizontally anchored to the agar surface. Though 1-MCP-treated and control seedlings showed differential ability to penetrate in the agar, the inhibition of root elongation was nearly similar for both treatments. While increased mechanical impedance also progressively impaired hypocotyl elongation in 1-MCP treated seedlings, it did not affect the hypocotyl length of control seedlings. The decline in root elongation was also associated with increased expression of DR5::GUS activity in the root tip signifying accumulation of auxin at the root tip. The increased expression of DR5::GUS activity in the root tip was also observed in 1-MCP treated seedlings, indicating independence of this response from ethylene signaling. Our results indicate operation of a sensing mechanism in root that likely operates independently of ethylene but involves auxin to determine the degree of impedance of the substratum.

  19. Arctic fungal communities associated with roots of Bistorta vivipara do not respond to the same fine-scale edaphic gradients as the aboveground vegetation.

    PubMed

    Mundra, Sunil; Halvorsen, Rune; Kauserud, Håvard; Müller, Eike; Vik, Unni; Eidesen, Pernille B

    2015-03-01

    Soil conditions and microclimate are important determinants of the fine-scale distribution of plant species in the Arctic, creating locally heterogeneous vegetation. We hypothesize that root-associated fungal (RAF) communities respond to the same fine-scale environmental gradients as the aboveground vegetation, creating a coherent pattern between aboveground vegetation and RAF. We explored how RAF communities of the ectomycorrhizal (ECM) plant Bistorta vivipara and aboveground vegetation structure of arctic plants were affected by biotic and abiotic variables at 0.3-3.0-m scales. RAF communities were determined using pyrosequencing. Composition and spatial structure of RAF and aboveground vegetation in relation to collected biotic and abiotic variables were analysed by ordination and semi-variance analyses. The vegetation was spatially structured along soil C and N gradients, whereas RAF lacked significant spatial structure. A weak relationship between RAF community composition and the cover of two ECM plants, B. vivipara and S. polaris, was found, and RAF richness increased with host root length and root weight. Results suggest that the fine-scale spatial structure of RAF communities of B. vivipara and the aboveground vegetation are driven by different factors. At fine spatial scales, neighbouring ECM plants may affect RAF community composition, whereas soil nutrients gradients structure the vegetation. PMID:25483568

  20. Arctic fungal communities associated with roots of Bistorta vivipara do not respond to the same fine-scale edaphic gradients as the aboveground vegetation.

    PubMed

    Mundra, Sunil; Halvorsen, Rune; Kauserud, Håvard; Müller, Eike; Vik, Unni; Eidesen, Pernille B

    2015-03-01

    Soil conditions and microclimate are important determinants of the fine-scale distribution of plant species in the Arctic, creating locally heterogeneous vegetation. We hypothesize that root-associated fungal (RAF) communities respond to the same fine-scale environmental gradients as the aboveground vegetation, creating a coherent pattern between aboveground vegetation and RAF. We explored how RAF communities of the ectomycorrhizal (ECM) plant Bistorta vivipara and aboveground vegetation structure of arctic plants were affected by biotic and abiotic variables at 0.3-3.0-m scales. RAF communities were determined using pyrosequencing. Composition and spatial structure of RAF and aboveground vegetation in relation to collected biotic and abiotic variables were analysed by ordination and semi-variance analyses. The vegetation was spatially structured along soil C and N gradients, whereas RAF lacked significant spatial structure. A weak relationship between RAF community composition and the cover of two ECM plants, B. vivipara and S. polaris, was found, and RAF richness increased with host root length and root weight. Results suggest that the fine-scale spatial structure of RAF communities of B. vivipara and the aboveground vegetation are driven by different factors. At fine spatial scales, neighbouring ECM plants may affect RAF community composition, whereas soil nutrients gradients structure the vegetation.

  1. Root Growth Inhibition in Boron-Deficient or Aluminum-Stressed Squash May Be a Result of Impaired Ascorbate Metabolism.

    PubMed Central

    Lukaszewski, K. M.; Blevins, D. G.

    1996-01-01

    Although cessation of growth is the most apparent symptom of boron deficiency, the biochemical function of boron in growth processes is not well understood. We propose that the action of boron in root meristems is associated with ascorbate metabolism. Total inhibition of root growth in squash (Cucurbita pepo L.) plants transferred to boron-free medium coincided with a major decrease (up to 98%) in the ascorbate concentration of root apices. Under low-boron conditions, in which root growth was partially inhibited, ascorbate concentration declined in proportion to growth rate. The decline in ascorbate concentration in boron-deficient root tips was not related to ascorbate oxidation. Ascorbate added to the medium improved root growth in plants supplied with insufficient boron. Increasing concentrations of aluminum in the nutrient medium caused progressive inhibition of root growth and a parallel reduction in ascorbate concentration of root apices. Elevated boron levels improved root growth under toxic aluminum conditions and produced root apices with higher ascorbate concentrations. To our knowledge, this is the first report of a correlation between boron nutrition, ascorbate concentration in root apices, and growth. These findings show that root growth inhibition resulting from either boron deficiency or aluminum toxicity may be a consequence of disrupted ascorbate metabolism. PMID:12226437

  2. Parameterising root system growth models using 2D neutron radiography images

    NASA Astrophysics Data System (ADS)

    Schnepf, Andrea; Felderer, Bernd; Vontobel, Peter; Leitner, Daniel

    2013-04-01

    Root architecture is a key factor for plant acquisition of water and nutrients from soil. In particular in view of a second green revolution where the below ground parts of agricultural crops are important, it is essential to characterise and quantify root architecture and its effect on plant resource acquisition. Mathematical models can help to understand the processes occurring in the soil-plant system, they can be used to quantify the effect of root and rhizosphere traits on resource acquisition and the response to environmental conditions. In order to do so, root architectural models are coupled with a model of water and solute transport in soil. However, dynamic root architectural models are difficult to parameterise. Novel imaging techniques such as x-ray computed tomography, neutron radiography and magnetic resonance imaging enable the in situ visualisation of plant root systems. Therefore, these images facilitate the parameterisation of dynamic root architecture models. These imaging techniques are capable of producing 3D or 2D images. Moreover, 2D images are also available in the form of hand drawings or from images of standard cameras. While full 3D imaging tools are still limited in resolutions, 2D techniques are a more accurate and less expensive option for observing roots in their environment. However, analysis of 2D images has additional difficulties compared to the 3D case, because of overlapping roots. We present a novel algorithm for the parameterisation of root system growth models based on 2D images of root system. The algorithm analyses dynamic image data. These are a series of 2D images of the root system at different points in time. Image data has already been adjusted for missing links and artefacts and segmentation was performed by applying a matched filter response. From this time series of binary 2D images, we parameterise the dynamic root architecture model in the following way: First, a morphological skeleton is derived from the binary

  3. The Regulation of Growth in the Distal Elongation Zone of Maize Roots

    NASA Technical Reports Server (NTRS)

    Evans, Michael L.

    1998-01-01

    The major goals of the proposed research were 1. To develop specialized software for automated whole surface root expansion analysis and to develop technology for controlled placement of surface electrodes for analysis of relationships between root growth and root pH and electrophysiological properties. 2. To measure surface pH patterns and determine the possible role of proton flux in gravitropic sensing or response, and 3. To determine the role of auxin transport in establishment of patterns of proton flux and electrical gradients during the gravitropic response of roots with special emphasis on the role of the distal elongation zone in the early phases of the gravitropic response.

  4. Effects of the distribution, amount, and size of beech fine roots on the C-turnover in the topsoil and subsoil of a sandy podzolic Cambisol

    NASA Astrophysics Data System (ADS)

    Vormstein, Svendja; Kaiser, Michael; Ludwig, Bernard

    2015-04-01

    The function of soil to act as a sink for CO2 is affected by the decomposition intensity of plant roots entering the mineral soil at different depths. Little is known about the key factors governing the mineralization kinetics of beech fine roots in different soil depths. We aimed to analyze the effects of the distribution, amount, and size of beech fine roots on their decomposition in the top- and subsoil. Topsoil (2 - 10 cm) and subsoil (145 - 152 cm) samples were taken from 3 profiles of a sandy Cambisol under beech located near Hannover (Germany). Incubation experiments were carried out for 300 days at 10°C and water contents at 50% of the water-holding capacity and CO2 emission rates were determined using an automated microcosm system. Treatments included control soils (either homogenized and sieved <2 mm or as intact soil column) and application of dried beech fine roots of different sizes (<2 mm and 1-2 cm) at different application rates (2 g kg-1 and 8 g kg-1) either homogenously mixed with homogenized soil or added in form of hot spots to the columns. First order models were applied to the cumulative C mineralization data. Calibration of a one-pool model was carried out for the C mineralization of the control topsoil. A two-pool model was calibrated to C mineralization data of the treatment with root application to subsoil at the rate of 2 g kg-1. Models were validated in the treatments using topsoil and root application at the rate of 2 g kg-1 (using the three pools obtained in the calibration) and at the rate of 8 g kg-1 (using the three pools obtained in the calibration and multiplying the maximum mineralizable root amounts by 4). The C mineralization data for the samples containing roots <2 mm, homogenously distributed at a concentration of 2 g per kg topsoil and subsoil and at a concentration of 8 g per kg subsoil were well described (calibration) or estimated (validation) indicating that root composition and amount were highly important for the C

  5. Comparative effects of auxin and abscisic acid on growth, hydrogen ion efflux and gravitropism in primary roots of maize

    NASA Technical Reports Server (NTRS)

    Evans, M. L.; Mulkey, T. J.

    1984-01-01

    In order to test the idea that auxin action on root growth may be mediated by H(+) movement, the correlation of auxin action on growth and H(+) movement in roots was examined along with changes in H(+) efflux patterns associated with the asymmetric growth which occurs during gravitropism. The effects of indoleacetic acid (IAA) and abscisic acid (AbA) on growth, H(+) secretion, and gravitropism in roots were compared. Results show a close correlation existent between H(+) efflux and growth in maize roots. In intact roots there is strong H(+) efflux from the elongation zone. Growth-promoting concentrations of IAA stimulate H(+) efflux. During gravitropism the H(+) efflux from the elongation zone becomes asymmetric; the evidence indicates that auxin redistribution contributes to the development of acid efflux asymmetry. That AbA stimulates root growth is reflected in its ability to stimulate H(+) efflux from apical root segments.

  6. Effects of annual tillage on organic carbon in a fine-textured udalf: The importance of root dynamics to soil carbon storage

    SciTech Connect

    Richter, D.D. ); Babbar, L.I.; Jaeger, M. ); Huston, M.A. )

    1990-02-01

    Seven years of annual tillage of a fine-textured Hapludalf, cleared of forest about 160 yr ago and more recently cropped for hay, caused grasses to be replaced by annual herbs. Tillage decreased carbon (C) stored in the surface meter of soil, mainly by altering plant species composition. Carbon storage in the surface 15 cm of soil was reduced by 24%, i.e., by 679 g C/m{sup 2}, 76% of which was due to a reduction in root biomass. Relatively small changes were found in mineral soil organic C from annual tillage, i.e., about 1 mg C/g soil. Results illustrate a dual-component cycle of soil organic C that appears especially pronounced in these fine-textured soils: (1) a rapidly cycling, plant-dominated C pool, and (2) a much more slowly cycling resistant C pool at least partly bound to clay-mineral surfaces. The dynamics of root C can be a dominant factor to the C balance of tilled and cropped soils. In the present study, root C in untilled plots totaled only about one-quarter of the total C in the 0- to 15-cm depth of soil, yet reductions in root C accounted for three-quarters of the total loss of C below ground. To determine effects of land use on soil C, soil samplings must distinguish clearly between effects on plant roots from those on mineral-soil organic matter.

  7. Cell wall-bound cationic and anionic class III isoperoxidases of pea root: biochemical characterization and function in root growth.

    PubMed

    Kukavica, Biljana M; Veljovicc-Jovanovicc, Sonja D; Menckhoff, Ljiljana; Lüthje, Sabine

    2012-07-01

    Cell wall isolated from pea roots was used to separate and characterize two fractions possessing class III peroxidase activity: (i) ionically bound proteins and (ii) covalently bound proteins. Modified SDS-PAGE separated peroxidase isoforms by their apparent molecular weights: four bands of 56, 46, 44, and 41kDa were found in the ionically bound fraction (iPOD) and one band (70kDa) was resolved after treatment of the cell wall with cellulase and pectinase (cPOD). Isoelectric focusing (IEF) patterns for iPODs and cPODs were significantly different: five iPODs with highly cationic pI (9.5-9.2) were detected, whereas the nine cPODs were anionic with pI values between pH 3.7 and 5. iPODs and cPODs showed rather specific substrate affinity and different sensitivity to inhibitors, heat, and deglycosylation treatments. Peroxidase and oxidase activities and their IEF patterns for both fractions were determined in different zones along the root and in roots of different ages. New iPODs with pI 9.34 and 9.5 were induced with root growth, while the activity of cPODs was more related to the formation of the cell wall in non-elongating tissue. Treatment with auxin that inhibits root growth led to suppression of iPOD and induction of cPOD. A similar effect was obtained with the widely used elicitor, chitosan, which also induced cPODs with pI 5.3 and 5.7, which may be specifically related to pathogen defence. The differences reported here between biochemical properties of cPOD and iPOD and their differential induction during development and under specific treatments implicate that they are involved in specific and different physiological processes. PMID:22760472

  8. Cell wall-associated ROOT HAIR SPECIFIC 10, a proline-rich receptor-like kinase, is a negative modulator of Arabidopsis root hair growth.

    PubMed

    Hwang, Youra; Lee, Hyodong; Lee, Young-Sook; Cho, Hyung-Taeg

    2016-03-01

    Plant cell growth is restricted by the cell wall, and cell wall dynamics act as signals for the cytoplasmic and nuclear events of cell growth. Among various receptor kinases, ROOT HAIR SPECIFIC 10 (RHS10) belongs to a poorly known receptor kinase subfamily with a proline-rich extracellular domain. Here, we report that RHS10 defines the root hair length of Arabidopsis thaliana by negatively regulating hair growth. RHS10 modulates the duration of root hair growth rather than the growth rate. As poplar and rice RHS10 orthologs also showed a root hair-inhibitory function, this receptor kinase-mediated function appears to be conserved in angiosperms. RHS10 showed a strong association with the cell wall, most probably through its extracellular proline-rich domain (ECD). Deletion analysis of the ECD demonstrated that a minimal extracellular part, which includes a few proline residues, is required for RHS10-mediated root hair inhibition. RHS10 suppressed the accumulation of reactive oxygen species (ROS) in the root, which are necessary for root hair growth. A yeast two-hybrid screening identified an RNase (RNS2) as a putative downstream target of RHS10. Accordingly, RHS10 overexpression decreased and RHS10 loss increased RNA levels in the hair-growing root region. Our results suggest that RHS10 mediates cell wall-associated signals to maintain proper root hair length, at least in part by regulating RNA catabolism and ROS accumulation. PMID:26884603

  9. Cell wall-associated ROOT HAIR SPECIFIC 10, a proline-rich receptor-like kinase, is a negative modulator of Arabidopsis root hair growth

    PubMed Central

    Hwang, Youra; Lee, Hyodong; Lee, Young-Sook; Cho, Hyung-Taeg

    2016-01-01

    Plant cell growth is restricted by the cell wall, and cell wall dynamics act as signals for the cytoplasmic and nuclear events of cell growth. Among various receptor kinases, ROOT HAIR SPECIFIC 10 (RHS10) belongs to a poorly known receptor kinase subfamily with a proline-rich extracellular domain. Here, we report that RHS10 defines the root hair length of Arabidopsis thaliana by negatively regulating hair growth. RHS10 modulates the duration of root hair growth rather than the growth rate. As poplar and rice RHS10 orthologs also showed a root hair-inhibitory function, this receptor kinase-mediated function appears to be conserved in angiosperms. RHS10 showed a strong association with the cell wall, most probably through its extracellular proline-rich domain (ECD). Deletion analysis of the ECD demonstrated that a minimal extracellular part, which includes a few proline residues, is required for RHS10-mediated root hair inhibition. RHS10 suppressed the accumulation of reactive oxygen species (ROS) in the root, which are necessary for root hair growth. A yeast two-hybrid screening identified an RNase (RNS2) as a putative downstream target of RHS10. Accordingly, RHS10 overexpression decreased and RHS10 loss increased RNA levels in the hair-growing root region. Our results suggest that RHS10 mediates cell wall-associated signals to maintain proper root hair length, at least in part by regulating RNA catabolism and ROS accumulation. PMID:26884603

  10. Aggregated and complementary: symmetric proliferation, overyielding, and mass effects explain fine-root biomass in soil patches in a diverse temperate deciduous forest landscape.

    PubMed

    Valverde-Barrantes, Oscar J; Smemo, Kurt A; Feinstein, Larry M; Kershner, Mark W; Blackwood, Christopher B

    2015-01-01

    Few studies describe root distributions at the species level in diverse forests, although belowground species interactions and traits are often assumed to affect fine-root biomass (FRB). We used molecular barcoding to study how FRB of trees relates to soil characteristics, species identity, root diversity, and root traits, and how these relationships are affected by proximity to ecotones in a temperate forest landscape. We found that soil patch root biomass increased in response to soil resources across all species, and there was little belowground vertical or horizontal spatial segregation among species. Root traits and species relative abundance did not explain significant variation in FRB after correcting for soil fertility. A positive relationship between phylogenetic diversity and FRB indicated significant belowground overyielding attributable to local root diversity. Finally, variation in FRB explained by soil fertility and diversity was reduced near ecotones, but only because of a reduction in biomass in periodically anoxic areas. These results suggest that symmetric responses to soil properties are coupled with complementary species traits and interactions to explain variation in FRB among soil patches. In addition, landscape-level dispersal among habitats and across ecotones helps explain variation in the strength of these relationships in complex landscapes. PMID:25441303

  11. Aggregated and complementary: symmetric proliferation, overyielding, and mass effects explain fine-root biomass in soil patches in a diverse temperate deciduous forest landscape.

    PubMed

    Valverde-Barrantes, Oscar J; Smemo, Kurt A; Feinstein, Larry M; Kershner, Mark W; Blackwood, Christopher B

    2015-01-01

    Few studies describe root distributions at the species level in diverse forests, although belowground species interactions and traits are often assumed to affect fine-root biomass (FRB). We used molecular barcoding to study how FRB of trees relates to soil characteristics, species identity, root diversity, and root traits, and how these relationships are affected by proximity to ecotones in a temperate forest landscape. We found that soil patch root biomass increased in response to soil resources across all species, and there was little belowground vertical or horizontal spatial segregation among species. Root traits and species relative abundance did not explain significant variation in FRB after correcting for soil fertility. A positive relationship between phylogenetic diversity and FRB indicated significant belowground overyielding attributable to local root diversity. Finally, variation in FRB explained by soil fertility and diversity was reduced near ecotones, but only because of a reduction in biomass in periodically anoxic areas. These results suggest that symmetric responses to soil properties are coupled with complementary species traits and interactions to explain variation in FRB among soil patches. In addition, landscape-level dispersal among habitats and across ecotones helps explain variation in the strength of these relationships in complex landscapes.

  12. Soil microbial biomass and root growth in Bt and non-Bt cotton

    NASA Astrophysics Data System (ADS)

    Tan, D. K. Y.; Broughton, K.; Knox, O. G.; Hulugalle, N. R.

    2012-04-01

    The introduction of transgenic Bacillus thuringiensis (Bt) cotton (Gossypium hirsutum L.) has had a substantial impact on pest management in the cotton industry. While there has been substantial research done on the impact of Bt on the above-ground parts of the cotton plant, less is known about the effect of Bt genes on below ground growth of cotton and soil microbial biomass. The aim of this research was to test the hypothesis that Bt [Sicot 80 BRF (Bollgard II Roundup Ready Flex®)] and non-Bt [Sicot 80 RRF (Roundup Ready Flex®)] transgenic cotton varieties differ in root growth and root turnover, carbon indices and microbial biomass. A field experiment was conducted in Narrabri, north-western NSW. The experimental layout was a randomised block design and used minirhizotron and core break and root washing methods to measure cotton root growth and turnover during the 2008/09 season. Root growth in the surface 0-0.1 m of the soil was measured using the core break and root washing methods, and that in the 0.1 to 1 m depth was measured with a minirhizotron and an I-CAP image capture system. These measurements were used to calculate root length per unit area, root carbon added to the soil through intra-seasonal root death, carbon in roots remaining at the end of the season and root carbon potentially added to the soil. Microbial biomass was also measured using the ninhydrin reactive N method. Root length densities and length per unit area of non-Bt cotton were greater than Bt cotton. There were no differences in root turnover between Bt and non-Bt cotton at 0-1 m soil depth, indicating that soil organic carbon stocks may not be affected by cotton variety. Cotton variety did not have an effect on soil microbial biomass. The results indicate that while there are differences in root morphology between Bt and non-Bt cotton, these do not change the carbon turnover dynamics in the soil.

  13. Paleosols can promote root growth of the recent vegetation - a case study from the sandy soil-sediment sequence Rakt, the Netherlands

    NASA Astrophysics Data System (ADS)

    Gocke, M. I.; Kessler, F.; van Mourik, J. M.; Jansen, B.; Wiesenberg, G. L. B.

    2015-12-01

    Soil studies commonly comprise the uppermost meter for tracing e.g. soil development. However, the maximum rooting depth of various plants significantly exceeds this depth. We hypothesized that deeper parts of the soil, soil parent material and especially paleosols provide beneficial conditions in terms of e.g. nutrient contents, thus supporting their utilization and exploitation by deep roots. We aimed to decipher the different phases of soil formation in Dutch drift- and coversands. The study site is located at Bedafse Bergen (SE Netherlands) in a 200 year old oak stand. A recent Podzol developed on driftsand covering a Plaggic Anthrosol that established in a relict Podzol on Late Glacial eolian coversand. Root-free soil and sediment samples, collected in 10-15 cm depth increments, were subjected to a multi-proxy physical and geochemical approach. The Plaggic Anthrosol revealed low bulk density and high phosphorous and organic carbon contents, whereas the relict Podzol was characterized by high iron and aluminum contents. Frequencies of fine (≤ 2 mm) and medium roots (2-5 mm) were determined on horizontal levels and the profile wall for a detailed pseudo-three-dimensional insight. On horizontal levels, living roots maximized in the uppermost part of the relict Podzol with ca. 4450 and 220 m-2, significantly exceeding topsoil root abundances. Roots of oak trees thus benefited from the favorable growth conditions in the nutrient-rich Plaggic Anthrosol, whereas increased compactness and high aluminum contents of the relict Podzol caused a strong decrease of roots. The approach demonstrated the benefit of comprehensive root investigation to support and explain pedogenic investigations of soil profiles, as fine roots can be significantly underestimated when quantified at the profile wall. The possible rooting of soil parent material and paleosols long after their burial confirmed recent studies on the potential influence of rooting to overprint sediment

  14. Determination of zinc oxide nanoparticles toxicity in root growth in wheat (Triticum aestivum L.) seedlings.

    PubMed

    Prakash, Meppaloor G; Chung, Ill Min

    2016-09-01

    The effect of zinc oxide nanoparticles (ZnONPs) was studied in wheat (Triticum aestivum L.) seedlings under in vitro exposure conditions. To avoid precipitation of nanoparticles, the seedlings were grown in half strength semisolid Murashige and Skoog medium containing 0, 50, 100, 200, 400 and 500 mg L(-1) of ZnONPs. Analysis of zinc (Zn) content showed significant increase in roots. In vivo detection using fluorescent probe Zynpyr-1 indicated accumulation of Zn in primary and lateral root tips. All concentrations of ZnONPs significantly reduced root growth. However, significant decrease in shoot growth was observed only after exposure to 400 and 500 mg L(-1) of ZnONPs. The reactive oxygen species and lipid peroxidation levels significantly increased in roots. Significant increase in cell-wall bound peroxidase activity was observed after exposure to 500 mg L(-1) of ZnONPs. Histochemical staining with phloroglucinol-HCl showed lignification of root cells upon exposure to 500 mg L(-1) of ZnONPs. Treatment with propidium iodide indicated loss of cell viability in root tips of wheat seedlings. These results suggest that redox imbalances, lignification and cell death has resulted in reduction of root growth in wheat seedlings exposed to ZnONPs nanoparticles. PMID:27630051

  15. Overexpression of Arabidopsis Plasmodesmata Germin-Like Proteins Disrupts Root Growth and Development[C][W

    PubMed Central

    Ham, Byung-Kook; Li, Gang; Kang, Byung-Ho; Zeng, Fanchang; Lucas, William J.

    2012-01-01

    In plants, a population of non-cell-autonomous proteins (NCAPs), including numerous transcription factors, move cell to cell through plasmodesmata (PD). In many cases, the intercellular trafficking of these NCAPs is regulated by their interaction with specific PD components. To gain further insight into the functions of this NCAP pathway, coimmunoprecipitation experiments were performed on a tobacco (Nicotiana tabacum) plasmodesmal-enriched cell wall protein preparation using as bait the NCAP, pumpkin (Cucurbita maxima) PHLOEM PROTEIN16 (Cm-PP16). A Cm-PP16 interaction partner, Nt-PLASMODESMAL GERMIN-LIKE PROTEIN1 (Nt-PDGLP1) was identified and shown to be a PD-located component. Arabidopsis thaliana putative orthologs, PDGLP1 and PDGLP2, were identified; expression studies indicated that, postgermination, these proteins were preferentially expressed in the root system. The PDGLP1 signal peptide was shown to function in localization to the PD by a novel mechanism involving the endoplasmic reticulum-Golgi secretory pathway. Overexpression of various tagged versions altered root meristem function, leading to reduced primary root but enhanced lateral root growth. This effect on root growth was corrected with an inability of these chimeric proteins to form stable PD-localized complexes. PDGLP1 and PDGLP2 appear to be involved in regulating primary root growth by controlling phloem-mediated allocation of resources between the primary and lateral root meristems. PMID:22960910

  16. Elicitors from the endophytic fungus Trichoderma atroviride promote Salvia miltiorrhiza hairy root growth and tanshinone biosynthesis.

    PubMed

    Ming, Qianliang; Su, Chunyan; Zheng, Chengjian; Jia, Min; Zhang, Qiaoyan; Zhang, Hong; Rahman, Khalid; Han, Ting; Qin, Luping

    2013-12-01

    Biotic elicitors can be used to stimulate the production of secondary metabolites in plants. However, limited information is available on the effects of biotic elicitors from endophytic fungi on their host plant. Trichoderma atroviride D16 is an endophytic fungus isolated from the root of Salvia miltiorrhiza and previously reported to produce tanshinone I (T-I) and tanshinone IIA (T-IIA). Here, the effects of extract of mycelium (EM) and the polysaccharide fraction (PSF), produced by T. atroviride D16, on the growth and secondary metabolism of S. miltiorrhiza hairy roots are reported. The results indicated that both EM and PSF promoted hairy root growth and stimulated the biosynthesis of tanshinones in hairy roots. EM slightly suppressed the accumulation of phenolic acids, while PSF had no significant influence on the accumulation of these compounds. When comparing the effects of EM versus PSF, it was concluded that PSF is one of the main active constituents responsible for promoting hairy root growth, as well as stimulating biosynthesis of tanshinones in the hairy root cultures. Moreover, the transcriptional activity of genes involved in the tanshinone biosynthetic pathway increased significantly with PSF treatment. Thus, PSF from endophytic T. atroviride D16 affected the chemical composition of the host plant by influencing the expression of genes related to the secondary metabolite biosynthetic pathway. Furthermore, treatment with PSF can be effectively utilized for large-scale production of tanshinones in the S. miltiorrhiza hairy root culture system.

  17. Water supply and not nitrate concentration determines primary root growth in Arabidopsis.

    PubMed

    Chapman, Nick; Whalley, W Richard; Lindsey, Keith; Miller, Anthony J

    2011-10-01

    Understanding how root system architecture (RSA) adapts to changing nitrogen and water availability is important for improving acquisition. A sand rhizotron system was developed to study RSA in a porous substrate under tightly regulated nutrient supply. The RSA of Arabidopsis seedlings under differing nitrate (NO₃⁻) and water supplies in agar and sand was described. The hydraulic conductivity of the root environment was manipulated by using altered sand particle size and matric potentials. Ion-selective microelectrodes were used to quantify NO₃⁻ at the surface of growing primary roots in sands of different particle sizes. Differences in RSA were observed between seedlings grown on agar and sand, and the influence of NO₃⁻ (0.1-10.0 mm) and water on RSA was determined. Primary root length (PRL) was a function of water flux and independent of NO₃⁻. The percentage of roots with laterals correlated with water flux, whereas NO₃⁻ supply was important for basal root (BR) growth. In agar and sand, the NO₃⁻ activities at the root surface were higher than those supplied in the nutrient solution. The sand rhizotron system is a useful tool for the study of RSA, providing a porous growth environment that can be used to simulate the effects of hydraulic conductivity on growth.

  18. Overexpression of Arabidopsis plasmodesmata germin-like proteins disrupts root growth and development.

    PubMed

    Ham, Byung-Kook; Li, Gang; Kang, Byung-Ho; Zeng, Fanchang; Lucas, William J

    2012-09-01

    In plants, a population of non-cell-autonomous proteins (NCAPs), including numerous transcription factors, move cell to cell through plasmodesmata (PD). In many cases, the intercellular trafficking of these NCAPs is regulated by their interaction with specific PD components. To gain further insight into the functions of this NCAP pathway, coimmunoprecipitation experiments were performed on a tobacco (Nicotiana tabacum) plasmodesmal-enriched cell wall protein preparation using as bait the NCAP, pumpkin (Cucurbita maxima) PHLOEM PROTEIN16 (Cm-PP16). A Cm-PP16 interaction partner, Nt-PLASMODESMAL GERMIN-LIKE PROTEIN1 (Nt-PDGLP1) was identified and shown to be a PD-located component. Arabidopsis thaliana putative orthologs, PDGLP1 and PDGLP2, were identified; expression studies indicated that, postgermination, these proteins were preferentially expressed in the root system. The PDGLP1 signal peptide was shown to function in localization to the PD by a novel mechanism involving the endoplasmic reticulum-Golgi secretory pathway. Overexpression of various tagged versions altered root meristem function, leading to reduced primary root but enhanced lateral root growth. This effect on root growth was corrected with an inability of these chimeric proteins to form stable PD-localized complexes. PDGLP1 and PDGLP2 appear to be involved in regulating primary root growth by controlling phloem-mediated allocation of resources between the primary and lateral root meristems.

  19. 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

  20. Generation of fine hydromagmatic ash by growth and disintegration of glassy rinds

    USGS Publications Warehouse

    Mastin, L.G.

    2007-01-01

    The deposits of mafic hydromagmatic eruptions are more fine grained and variable in vesicularity than dry magmatic deposits. Blocky, equant shapes of many hydromagmatic clasts also contrast with droplet, thread, and bubble wall morphology of dry magmatic fragments. Small (growth and disintegration of glassy rinds on pyroclast surfaces as they deform within turbulent flows. This process, termed "turbulent shedding", may occur during the expansion phase of vapor explosions or during turbulent but nonexplosive mixing of magma with water, steam, or water sprays. The occurrence of turbulent shedding and the resulting fragment sizes depend on the timescale for rind growth and the timescale between disturbances that remove or disintegrate glassy rinds. Turbulent shedding is directly observable in some small littoral jets at Kilauea. Calculations suggest that, in the presence of liquid water or water sprays, glassy rinds having a thickness of microns to millimeters should form in milliseconds to seconds. This is similar to the timescale between turbulent velocity fluctuations that can shred lava globules and remove such rinds. The fraction of a deposit consisting of fine ash should increase with the duration of this process: Large-scale Surtseyan jets generate hundreds or thousands of shedding events; bubble bursts or tephra jets at Kilauea's coast may produce only a few.

  1. CARRY-OVER EFFECTS OF OZONE ON ROOT GROWTH AND CARBOHYDRATE CONCENTRATIONS OF PONDEROSA PINE SEEDLINGS

    EPA Science Inventory

    Ozone exposure decreases belowground carbon allocation and root growth of plants;however,the extent to which these effects persist and the cumulative impact of ozone stress on plant growth are poorly understood.To evaluate the potential for plant compensation,we followed the prog...

  2. Modeling potato root growth and water uptake under water stress conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Potato (Solanum tuberosum L.) growth and yield are sensitive to drought starting at mild stress levels. Accurate simulation of root growth is critical for estimating water and nutrient uptake dynamics of major crops and improving agricultural decision support tools for natural resource management. ...

  3. Toxic effects of Cu(2+) on growth, nutrition, root morphology, and distribution of Cu in roots of Sabi grass.

    PubMed

    Kopittke, P M; Asher, C J; Blamey, F P C; Menzies, N W

    2009-08-01

    Sabi grass (Urochloa mosambicensis (Hack.) Dandy) (a C4 species of Poaceae) is commonly used to revegetate disturbed sites in low-rainfall environments, but comparatively little is known regarding copper (Cu) toxicity in this species. A dilute nutrient solution culture experiment was conducted for 10 d to examine the effects of elevated Cu(2+) activities ({Cu(2+)}) on the growth of Sabi grass. Growth was inhibited by high Cu in solution, with a 50% reduction in the relative fresh mass occurring at 1.0 microM {Cu(2+)} for the roots and 1.2 microM {Cu(2+)} for the shoots. In solutions containing 1.2-1.9 microM {Cu(2+)}, many of the roots ruptured due to the tearing and separation of the rhizodermis and outer cortex from the underlying tissues. Transmission electron microscopy revealed that Cu-rich deposits were found to accumulate predominantly within vacuoles. Due to limited translocation of Cu from the roots to the shoots, phytotoxicity is likely to be more of a problem in remediation of Cu-toxic sites than is Cu toxicity of fauna consuming the above-ground biomass.

  4. The Small GTPase ROP10 of Medicago truncatula Is Required for Both Tip Growth of Root Hairs and Nod Factor-Induced Root Hair Deformation

    PubMed Central

    Lei, Ming-Juan; Wang, Qi; Li, Xiaolin; Chen, Aimin; Luo, Li; Xie, Yajun; Li, Guan; Luo, Da; Mysore, Kirankumar S.; Wen, Jiangqi; Xie, Zhi-Ping; Staehelin, Christian; Wang, Yan-Zhang

    2015-01-01

    Rhizobia preferentially enter legume root hairs via infection threads, after which root hairs undergo tip swelling, branching, and curling. However, the mechanisms underlying such root hair deformation are poorly understood. Here, we showed that a type II small GTPase, ROP10, of Medicago truncatula is localized at the plasma membrane (PM) of root hair tips to regulate root hair tip growth. Overexpression of ROP10 and a constitutively active mutant (ROP10CA) generated depolarized growth of root hairs, whereas a dominant negative mutant (ROP10DN) inhibited root hair elongation. Inoculated with Sinorhizobium meliloti, the depolarized swollen and ballooning root hairs exhibited extensive root hair deformation and aberrant infection symptoms. Upon treatment with rhizobia-secreted nodulation factors (NFs), ROP10 was transiently upregulated in root hairs, and ROP10 fused to green fluorescent protein was ectopically localized at the PM of NF-induced outgrowths and curls around rhizobia. ROP10 interacted with the kinase domain of the NF receptor NFP in a GTP-dependent manner. Moreover, NF-induced expression of the early nodulin gene ENOD11 was enhanced by the overexpression of ROP10 and ROP10CA. These data suggest that NFs spatiotemporally regulate ROP10 localization and activity at the PM of root hair tips and that interactions between ROP10 and NF receptors are required for root hair deformation and continuous curling during rhizobial infection. PMID:25794934

  5. Seedling root responses to soil moisture and the identification of a belowground trait spectrum across three growth forms.

    PubMed

    Larson, Julie E; Funk, Jennifer L

    2016-05-01

    Root trait variation and plasticity could be key factors differentiating plant performance under drought. However, water manipulation and root measurements are rarely coupled empirically across growth forms to identify whether belowground strategies are generalizable across species. We measured seedling root traits across three moisture levels in 18 Mediterranean forbs, grasses, and woody species. Drought increased the root mass fraction (RMF) and decreased the relative proportion of thin roots (indicated by increased root diameters and decreased specific root length (SRL)), rates of root elongation and growth, plant nitrogen uptake, and plant growth. Although responses varied across species, plasticity was not associated with growth form. Woody species differed from forbs and grasses in many traits, but herbaceous groups were similar. Across water treatments, trait correlations suggested a single spectrum of belowground trade-offs related to resource acquisition and plant growth. While effects of SRL and RMF on plant growth shifted with drought, root elongation rate consistently represented this spectrum. We demonstrate that general patterns of root morphology and plasticity are identifiable across diverse species. Root trait measurements should enhance our understanding of belowground strategy and performance across growth forms, but it will be critical to incorporate plasticity and additional aspects of root function into these efforts.

  6. [Effects of partial root excision on the growth, photosynthesis, and antioxidant enzyme activities of maize under salt stress].

    PubMed

    Zhang, Hong; Cui, Li-Na; Meng, Jia-Jia; Zhang, Hai-Yan; Shi, De-Yang; Dong, Shu-Ting; Zhang, Ji-Wang; Liu, Peng

    2012-12-01

    A pot experiment was conducted to study the effects of partial root excision on the growth of two maize cultivars (Zhengdan 958 and Denghai 9) throughout their growth period and the photosynthesis and leaf antioxidant enzyme activities at grain-filling stage under salt stress. Four treatments were installed, i. e., control (no salt), low salt (0.2% NaCl), moderate salt (0.4% NaCl), and high salt (0.6% NaCl). Under low salt stress, the grain yield of Zhengdan 958 and Denghai 9 with partial root excision was increased by 13.1% and 31.4%, respectively, as compared with that of the cultivars with no root excision. At jointing stage, the growth of the cultivars with partial root excision was restrained, the root- and shoot dry masses under the same salt stresses being lesser than those of the cultivars with no root excision, but the growth under the conditions of no salt and low salt recovered quickly. At milk-ripe stage and under no salt and low salt conditions, the root- and shoot dry masses, leaf area, total root length, total root surface area, root activity, leaf chlorophyll content, and ear leaf net photosynthetic rate, stomatal conductance, transpiration rate, and CAT and POD activities of the cultivars with partial root excision were significantly larger than those of the cultivars with no root excision, while the shoot diameter and ear leaf MDA content were in adverse. Moderate and high salt stresses had greater effects on the cultivars with partial root excision. The root- and shoot dry masses, root morphology, and photosynthesis indices of the cultivars with partial root excision were smaller than those of the cultivars with no root excision, so did the grain yields. Throughout the growth period of the cultivars, the growth of the cultivars with partial root excision depended on the salt concentration, i. e., was promoted under no and low salt, and inhibited under moderate and high salt conditions.

  7. Nitrate-Regulated Glutaredoxins Control Arabidopsis Primary Root Growth1[OPEN

    PubMed Central

    Walters, Laura A.; Cooper, Andrew M.; Olvera, Jocelyn G.; Rosas, Miguel A.; Rasmusson, Allan G.

    2016-01-01

    Nitrogen is an essential soil nutrient for plants, and lack of nitrogen commonly limits plant growth. Soil nitrogen is typically available to plants in two inorganic forms: nitrate and ammonium. To better understand how nitrate and ammonium differentially affect plant metabolism and development, we performed transcriptional profiling of the shoots of ammonium-supplied and nitrate-supplied Arabidopsis (Arabidopsis thaliana) plants. Seven genes encoding class III glutaredoxins were found to be strongly and specifically induced by nitrate. RNA silencing of four of these glutaredoxin genes (AtGRXS3/4/5/8) resulted in plants with increased primary root length (approximately 25% longer than the wild type) and decreased sensitivity to nitrate-mediated inhibition of primary root growth. Increased primary root growth is also a well-characterized phenotype of many cytokinin-deficient plant lines. We determined that nitrate induction of glutaredoxin gene expression was dependent upon cytokinin signaling and that cytokinins could activate glutaredoxin gene expression independent of plant nitrate status. In addition, crosses between “long-root” cytokinin-deficient plants and “long-root” glutaredoxin-silenced plants generated hybrids that displayed no further increase in primary root length (i.e. epistasis). Collectively, these findings suggest that AtGRXS3/4/5/8 operate downstream of cytokinins in a signal transduction pathway that negatively regulates plant primary root growth in response to nitrate. This pathway could allow Arabidopsis to actively discriminate between different nitrogen sources in the soil, with the preferred nitrogen source, nitrate, acting to suppress primary root growth (vertical dimension) in concert with its well-characterized stimulatory effect on lateral root growth (horizontal dimension). PMID:26662603

  8. Understanding the development of roots exposed to contaminants and the potential of plant-associated bacteria for optimization of growth

    PubMed Central

    Remans, Tony; Thijs, Sofie; Truyens, Sascha; Weyens, Nele; Schellingen, Kerim; Keunen, Els; Gielen, Heidi; Cuypers, Ann; Vangronsveld, Jaco

    2012-01-01

    Background and Scope Plant responses to the toxic effects of soil contaminants, such as excess metals or organic substances, have been studied mainly at physiological, biochemical and molecular levels, but the influence on root system architecture has received little attention. Nevertheless, the precise position, morphology and extent of roots can influence contaminant uptake. Here, data are discussed that aim to increase the molecular and ecological understanding of the influence of contaminants on root system architecture. Furthermore, the potential of plant-associated bacteria to influence root growth by their growth-promoting and stress-relieving capacities is explored. Methods Root growth parameters of Arabidopsis thaliana seedlings grown in vertical agar plates are quantified. Mutants are used in a reverse genetics approach to identify molecular components underlying quantitative changes in root architecture after exposure to excess cadmium, copper or zinc. Plant-associated bacteria are isolated from contaminated environments, genotypically and phenotypically characterized, and used to test plant root growth improvement in the presence of contaminants. Key Results The molecular determinants of primary root growth inhibition and effects on lateral root density by cadmium were identified. A vertical split-root system revealed local effects of cadmium and copper on root development. However, systemic effects of zinc exposure on root growth reduced both the avoidance of contaminated areas and colonization of non-contaminated areas. The potential for growth promotion and contaminant degradation of plant-associated bacteria was demonstrated by improved root growth of inoculated plants exposed to 2,4-di-nitro-toluene (DNT) or cadmium. Conclusions Knowledge concerning the specific influence of different contaminants on root system architecture and the molecular mechanisms by which this is achieved can be combined with the exploitation of plant-associated bacteria to

  9. Experimental observations of root growth in a controlled photoelastic granular material

    NASA Astrophysics Data System (ADS)

    Mora, Serge; Bares, Jonathan; Delenne, Jean-Yves; Fourcaud, Thierry

    The mechanism of root growth in soil is a key issue to understand both how to improve plant development and how to stabilize grounds. However, no experimental studies have been carried out to directly observe root development and surrounding stress while imposing specific grain configurations or mechanical loading. We present a novel set-up which permits to observe the development of chickpea root networks in a 2D granular material made of bidisperse photoelastic discs while imposing the position of the grains, the intergranular spacing and the nature of the system confinement: (i) open cell, (ii) confined cell (iii) sheared cell. In the experimental apparatus several root development cells are treated in parallel to increase the statistical meaning of the observations. Evolution of the root network is followed as well as position and pressure inside each disc by mean of a camera and classical photoelastic techniques. Preliminary results will be presented.

  10. Tooth root growth impairment after mantle radiation in long-term survivors of Hodgkin's disease

    SciTech Connect

    McGinnis, J.P. Jr.; Hopkins, K.P.; Thompson, E.I.; Hustu, H.O.

    1985-10-01

    The tooth root growth impairment that resulted from 35 to 37 Gy mantle port radiation in 47 long-term survivors of childhood Hodgkin's disease was quantified and related to specific age groups and categories of teeth. Root measurements of the mandibular permanent canines, first and second premolars, and first and second molars were made from sequential panoramic radiographs taken at the time of radiation therapy and after the closure of root apexes. The severity of root growth impairment was greatest in patients who received radiation during the early stages of odontogenesis. With later stages of odontogenesis, and as the age increased at the time of treatment, less impairment occurred. The potential difficulties of using repeated panoramic radiographs to assess tooth lengths in longitudinal studies also were discussed.

  11. Spatial Regulation of Root Growth: Placing the Plant TOR Pathway in a Developmental Perspective

    PubMed Central

    Barrada, Adam; Montané, Marie-Hélène; Robaglia, Christophe; Menand, Benoît

    2015-01-01

    Plant cells contain specialized structures, such as a cell wall and a large vacuole, which play a major role in cell growth. Roots follow an organized pattern of development, making them the organs of choice for studying the spatio-temporal regulation of cell proliferation and growth in plants. During root growth, cells originate from the initials surrounding the quiescent center, proliferate in the division zone of the meristem, and then increase in length in the elongation zone, reaching their final size and differentiation stage in the mature zone. Phytohormones, especially auxins and cytokinins, control the dynamic balance between cell division and differentiation and therefore organ size. Plant growth is also regulated by metabolites and nutrients, such as the sugars produced by photosynthesis or nitrate assimilated from the soil. Recent literature has shown that the conserved eukaryotic TOR (target of rapamycin) kinase pathway plays an important role in orchestrating plant growth. We will summarize how the regulation of cell proliferation and cell expansion by phytohormones are at the heart of root growth and then discuss recent data indicating that the TOR pathway integrates hormonal and nutritive signals to orchestrate root growth. PMID:26295391

  12. Spatial Regulation of Root Growth: Placing the Plant TOR Pathway in a Developmental Perspective.

    PubMed

    Barrada, Adam; Montané, Marie-Hélène; Robaglia, Christophe; Menand, Benoît

    2015-08-19

    Plant cells contain specialized structures, such as a cell wall and a large vacuole, which play a major role in cell growth. Roots follow an organized pattern of development, making them the organs of choice for studying the spatio-temporal regulation of cell proliferation and growth in plants. During root growth, cells originate from the initials surrounding the quiescent center, proliferate in the division zone of the meristem, and then increase in length in the elongation zone, reaching their final size and differentiation stage in the mature zone. Phytohormones, especially auxins and cytokinins, control the dynamic balance between cell division and differentiation and therefore organ size. Plant growth is also regulated by metabolites and nutrients, such as the sugars produced by photosynthesis or nitrate assimilated from the soil. Recent literature has shown that the conserved eukaryotic TOR (target of rapamycin) kinase pathway plays an important role in orchestrating plant growth. We will summarize how the regulation of cell proliferation and cell expansion by phytohormones are at the heart of root growth and then discuss recent data indicating that the TOR pathway integrates hormonal and nutritive signals to orchestrate root growth.

  13. Promotion of Growth and Hydrogen Ion Efflux by Auxin in Roots of Maize Pretreated with Ethylene Biosynthesis Inhibitors 1

    PubMed Central

    Mulkey, Timothy J.; Kuzmanoff, Konrad M.; Evans, Michael L.

    1982-01-01

    Low concentrations of auxin (e.g. 10−10m) do not promote the growth of intact seedling roots of maize (Zea mays L. Bear Hybrid WF 9 × 38). Higher concentrations are inhibitory. When the roots are pretreated with the ethylene biosynthesis inhibitors, cobalt and aminoethoxyvinylglycine, auxin (10−10 to 10−8m) strongly promotes their growth. The promotion of growth by auxin in pretreated roots is preceded by enhanced hydrogen ion secretion from the roots. The data indicate that hormone-enhanced hydrogen ion secretion may play a role in the rapid promotion of root growth by auxin. The ability of auxin to promote the growth of intact roots is discussed in relation to the Cholodny/Went hypothesis of hormonal control of root geotropism. PMID:16662442

  14. Influence of Microgravity Environment on Root Growth, Soluble Sugars, and Starch Concentration of Sweetpotato Stem Cuttings.

    PubMed

    Mortley, Desmond G; Bonsi, Conrad K; Hill, Walter A; Morris, Carlton E; Williams, Carol S; Davis, Ceyla F; Williams, John W; Levine, Lanfang H; Petersen, Barbara V; Wheeler, Raymond M

    2008-05-01

    Because sweetpotato [Ipomoea batatas (L.) Lam.] stem cuttings regenerate very easily and quickly, a study of their early growth and development in microgravity could be useful to an understanding of morphological changes that might occur under such conditions for crops that are propagated vegetatively. An experiment was conducted aboard a U.S. Space Shuttle to investigate the impact of microgravity on root growth, distribution of amyloplasts in the root cells, and on the concentration of soluble sugars and starch in the stems of sweetpotatoes. Twelve stem cuttings of 'Whatley/Loretan' sweetpotato (5 cm long) with three to four nodes were grown in each of two plant growth units filled with a nutrient agarose medium impregnated with a half-strength Hoagland solution. One plant growth unit was flown on Space Shuttle Colombia for 5 days, whereas the other remained on the ground as a control. The cuttings were received within 2 h postflight and, along with ground controls, processed in approximately 45 min. Adventitious roots were counted, measured, and fixed for electron microscopy and stems frozen for starch and sugar assays. Air samples were collected from the headspace of each plant growth unit for postflight determination of carbon dioxide, oxygen, and ethylene levels. All stem cuttings produced adventitious roots and growth was quite vigorous in both ground-based and flight samples and, except for a slight browning of some root tips in the flight samples, all stem cuttings appeared normal. The roots on the flight cuttings tended to grow in random directions. Also, stem cuttings grown in microgravity had more roots and greater total root length than ground-based controls. Amyloplasts in root cap cells of ground-based controls were evenly sedimented toward one end compared with a more random distribution in the flight samples. The concentration of soluble sugars, glucose, fructose, and sucrose and total starch concentration were all substantially greater in the

  15. Genome-wide association mapping in plants exemplified for root growth in Arabidopsis thaliana.

    PubMed

    Slovak, Radka; Göschl, Christian; Seren, Ümit; Busch, Wolfgang

    2015-01-01

    Genome-wide association (GWA) mapping is a powerful technique to address the molecular basis of genotype to phenotype relationships and to map regulators of biological processes. This chapter presents a protocol for genome-wide association mapping in Arabidopsis thaliana using the user-friendly internet application GWAPP, and provides a specific protocol for acquiring root trait data suitable for GWA studies using the semi-automated, high-throughput phenotyping pipeline BRAT for early root growth.

  16. 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.

  17. [Effects of Chinese onion' s root exudates on cucumber seedlings growth and rhizosphere soil microorganisms].

    PubMed

    Yang, Yang; Liu, Shou-wei; Pan, Kai; Wu, Feng-zhi

    2013-04-01

    Taking the Chinese onion cultivars with different allelopathy potentials as the donor and cucumber as the accepter, this paper studied the effects of Chinese onion' s root exudates on the seedlings growth of cucumber and the culturable microbial number and bacterial community structure in the seedlings rhizosphere soil. The root exudates of the Chinese onion cultivars could promote the growth of cucumber seedlings, and the stimulatory effect increased with the increasing concentration of the root exudates. However, at the same concentrations of root exudates, the stimulatory effect had no significant differences between the Chinese onion cultivars with strong and weak allelopathy potential. The root exudates of the Chinese onion cultivars increased the individual numbers of bacteria and actinomyces but decreased those of fungi and Fusarium in rhizosphere soil, being more significant for the Chinese onion cultivar with high allelopathy potential (L-06). The root exudates of the Chinese onion cultivars also increased the bacterial community diversity in rhizosphere soil. The cloning and sequencing results indicated that the differential bacteria bands were affiliated with Actinobacteria, Proteobacteria, and Anaerolineaceae, and Anaerolineaceae only occurred in the rhizosphere soil in the treatment of high allelopathy potential Chinese onion (L-06). It was suggested that high concentration (10 mL per plant) of root exudates from high allelopathy potential Chinese onion (L-06) could benefit the increase of bacterial community diversity in cucumber seedlings rhizosphere soil.

  18. Root growth and exudate production define the frequency of horizontal plasmid transfer in the Rhizosphere.

    PubMed

    Mølbak, Lars; Molin, Søren; Kroer, Niels

    2007-01-01

    To identify the main drivers of plasmid transfer in the rhizosphere, conjugal transfer was studied in the rhizospheres of pea and barley. The donor Pseudomonas putida KT2442, containing plasmid pKJK5::gfp, was coated onto the seeds, while the recipient P. putida LM24, having a chromosomal insertion of dsRed, was inoculated into the growth medium. Mean transconjugant-to-donor ratios in vermiculite were 4.0+/-0.8 x 10(-2) in the pea and 5.9+/-1.4 x 10(-3) in the barley rhizospheres. In soil, transfer ratios were about 10 times lower. As a result of a 2-times higher root exudation rate in pea, donor densities in pea (1 x 10(6)-2 x 10(9) CFU g(-1) root) were about 10 times higher than in barley. No difference in recipient densities was observed. In situ visualization of single cells on the rhizoplane and macroscopic visualization of the colonization pattern showed that donors and transconjugants were ubiquitously distributed in the pea rhizosphere, while they were only located on the upper parts of the barley roots. Because the barley root elongated about 10 times faster than the pea root, donors were probably outgrown by the elongating barley root. Thus by affecting the cell density and distribution, exudation and root growth appear to be key parameters controlling plasmid transfer in the rhizosphere. PMID:17069619

  19. [Effects of Chinese onion' s root exudates on cucumber seedlings growth and rhizosphere soil microorganisms].

    PubMed

    Yang, Yang; Liu, Shou-wei; Pan, Kai; Wu, Feng-zhi

    2013-04-01

    Taking the Chinese onion cultivars with different allelopathy potentials as the donor and cucumber as the accepter, this paper studied the effects of Chinese onion' s root exudates on the seedlings growth of cucumber and the culturable microbial number and bacterial community structure in the seedlings rhizosphere soil. The root exudates of the Chinese onion cultivars could promote the growth of cucumber seedlings, and the stimulatory effect increased with the increasing concentration of the root exudates. However, at the same concentrations of root exudates, the stimulatory effect had no significant differences between the Chinese onion cultivars with strong and weak allelopathy potential. The root exudates of the Chinese onion cultivars increased the individual numbers of bacteria and actinomyces but decreased those of fungi and Fusarium in rhizosphere soil, being more significant for the Chinese onion cultivar with high allelopathy potential (L-06). The root exudates of the Chinese onion cultivars also increased the bacterial community diversity in rhizosphere soil. The cloning and sequencing results indicated that the differential bacteria bands were affiliated with Actinobacteria, Proteobacteria, and Anaerolineaceae, and Anaerolineaceae only occurred in the rhizosphere soil in the treatment of high allelopathy potential Chinese onion (L-06). It was suggested that high concentration (10 mL per plant) of root exudates from high allelopathy potential Chinese onion (L-06) could benefit the increase of bacterial community diversity in cucumber seedlings rhizosphere soil. PMID:23898672

  20. Proteomics in deciphering the auxin commitment in the Arabidopsis thaliana root growth.

    PubMed

    Mattei, Benedetta; Sabatini, Sabrina; Schininà, M Eugenia

    2013-11-01

    The development of plant root systems is characterized by a high plasticity, made possible by the continual propagation of new meristems. Root architecture is fundamental for overall plant growth, abiotic stress resistance, nutrient uptake, and response to environmental changes. Understanding the function of genes and proteins that control root architecture and stress resistance will contribute to the development of more sustainable systems of intensified crop production. To meet these challenges, proteomics provide the genome-wide scale characterization of protein expression pattern, subcellular localization, post-translational modifications, activity regulation, and molecular interactions. In this review, we describe a variety of proteomic strategies that have been applied to study the proteome of the whole organ and of specific cell types during root development. Each has advantages and limitations, but collectively they are providing important insights into the mechanisms by which auxin structures and patterns the root system and into the interplay between signaling networks, auxin transport and growth. The acquisition of proteomic, transcriptomic, and metabolomic data sets of the root apex on the cell scale has revealed the high spatial complexity of regulatory networks and fosters the use of new powerful proteomic tools for a full understanding of the control of root developmental processes and environmental responses.

  1. [Growth and survival of Azospirillum in roots and maize rhizospheres with different levels of acidity].

    PubMed

    Eöry, V J; Momo, F R; Alvarez, M

    1995-01-01

    An experiment was carried out in order to evaluate the effect of pH on Azospirillum sp. growth and survival in maize rhizosphere. Sterilized maize seeds were sown in a perlite substratum with addition of a nutritive medium. The pots were buffered at two different pHs: 5.8 (group one) and 7.0 (group two). Each group was divided in two treatments: inoculated with Azospirillum sp. Az-39 and non-inoculated. Experimental pots were incubated at 20 degrees C with a 14 hour photoperiod. Growth of non-inoculated roots was negligible. Inoculated roots showed a better response at pH 5.8 than at 7.0. Several accompanying bacteria were found. Azospirillum grew in both groups with a low penetration into roots. A set of nutritive relationships among microorganisms and maize roots was observed; Xanthomonas is a maize pathogenic bacteria, and it is a NO3- consumer, and uses this anion as hydrogen acceptor. The Gram (-) Diplococcus is a nitrate producer . Cytophaga and Flavobacterium are related with roots decomposition. It is concluded that Azospirillum improves the root growth, mainly at pH 5.8. PMID:8552763

  2. Exaggerated root respiration accounts for growth retardation in a starchless mutant of Arabidopsis thaliana.

    PubMed

    Brauner, Katrin; Hörmiller, Imke; Nägele, Thomas; Heyer, Arnd G

    2014-07-01

    The knock-out mutation of plastidial phosphoglucomutase (pgm) causes a starchless phenotype in Arabidopsis thaliana, and results in a severe growth reduction of plants cultivated under diurnal conditions. It has been speculated that high soluble sugar levels accumulating during the light phase in leaf mesophyll might cause a reduction of photosynthetic activity or that shortage of reduced carbon during the night is the reason for the slow biomass gain of pgm. Separate simultaneous measurements of leaf net photosynthesis and root respiration demonstrate that photosynthetic activity per unit fresh weight is not reduced in pgm, whereas root respiration is strongly elevated. Comparison with a mutant defective in the dominating vacuolar invertase (AtβFruct4) revealed that high sucrose concentration in the cytosol, but not in the vacuole, of leaf cells is responsible for elevated assimilate transport to the root. Increased sugar supply to the root, as observed in pgm mutants, forces substantial respiratory losses. Because root respiration accounts for 80% of total plant respiration under long-day conditions, this gives rise to retarded biomass formation. In contrast, reduced vacuolar invertase activity leads to reduced net photosynthesis in the shoot and lowered root respiration, and affords an increased root/shoot ratio. The results demonstrate that roots have very limited capacity for carbon storage but exert rigid control of supply for their maintenance metabolism.

  3. Analysis of changes in relative elemental growth rate patterns in the elongation zone of Arabidopsis roots upon gravistimulation

    NASA Technical Reports Server (NTRS)

    Mullen, J. L.; Ishikawa, H.; Evans, M. L.

    1998-01-01

    Although Arabidopsis is an important system for studying root physiology, the localized growth patterns of its roots have not been well defined, particularly during tropic responses. In order to characterize growth rate profiles along the apex of primary roots of Arabidopsis thaliana (L.) Heynh (ecotype Columbia) we applied small charcoal particles to the root surface and analyzed their displacement during growth using an automated video digitizer system with custom software for tracking the markers. When growing vertically, the maximum elongation rate occurred 481 +/- 50 microns back from the extreme tip of the root (tip of root cap), and the elongation zone extended back to 912 +/- 137 microns. The distal elongation zone (DEZ) has previously been described as the apical region of the elongation zone in which the relative elemental growth rate (REGR) is < or = 30% of the peak rate in the central elongation zone. By this definition, our data indicate that the basal limit of the DEZ was located 248 +/- 30 microns from the root tip. However, after gravistimulation, the growth patterns of the root changed. Within the first hour of graviresponse, the basal limit of the DEZ and the position of peak REGR shifted apically on the upper flank of the root. This was due to a combination of increased growth in the DEZ and growth inhibition in the central elongation zone. On the lower flank, the basal limit of the DEZ shifted basipetally as the REGR decreased. These factors set up the gradient of growth rate across the root, which drives curvature.

  4. A molecular framework for the inhibition of Arabidopsis root growth in response to boron toxicity.

    PubMed

    Aquea, Felipe; Federici, Fernan; Moscoso, Cristian; Vega, Andrea; Jullian, Pastor; Haseloff, Jim; Arce-Johnson, Patricio

    2012-04-01

    Boron is an essential micronutrient for plants and is taken up in the form of boric acid (BA). Despite this, a high BA concentration is toxic for the plants, inhibiting root growth and is thus a significant problem in semi-arid areas in the world. In this work, we report the molecular basis for the inhibition of root growth caused by boron. We show that application of BA reduces the size of root meristems, correlating with the inhibition of root growth. The decrease in meristem size is caused by a reduction of cell division. Mitotic cell number significantly decreases and the expression level of key core cell cycle regulators is modulated. The modulation of the cell cycle does not appear to act through cytokinin and auxin signalling. A global expression analysis reveals that boron toxicity induces the expression of genes related with abscisic acid (ABA) signalling, ABA response and cell wall modifications, and represses genes that code for water transporters. These results suggest that boron toxicity produces a reduction of water and BA uptake, triggering a hydric stress response that produces root growth inhibition.

  5. Aluminum inhibits root growth and induces hydrogen peroxide accumulation in Plantago algarbiensis and P. almogravensis seedlings.

    PubMed

    Martins, Neusa; Gonçalves, Sandra; Romano, Anabela

    2013-12-01

    We have evaluated the impact of aluminum (Al) on germination, relative root growth, Al accumulation in roots tips, H2O2 levels, plasma membrane integrity, pigment levels, protein content, and the activities of superoxide dismutase (SOD) and catalase (CAT) in seedlings of the endangered Portuguese species Plantago algarbiensis and Plantago almogravensis. We found that up to 400 μM Al had no impact on the germination percentage in either species but inhibited root growth in a concentration-dependent manner (more severely in P. algarbiensis). Al accumulation in the root tips of both species was concentration dependent up to 200 μM but declined thereafter despite the absence of membrane damage. We observed a concentration-dependent induction of SOD activity but no change in CAT activity resulting in the accumulation of H2O2 (a known growth inhibitor), although its impact in P. almogravensis may be partially ameliorated by the accumulation of carotenoid pigments. Our data suggest an association between Al uptake, H2O2 production, and the inhibition of root growth during early seedling development in P. algarbiensis and P. almogravensis, although the latter is more tolerant towards higher concentrations of the metal. PMID:23702818

  6. Inhibitory Activity of Podophyllotoxin and Matairesinol-derivative Lignans on the Root Growth of Brassica campestris.

    PubMed

    Arimoto, M; Matsuura, S; Muro, C; Tsujibo, H; Matsumura, E; Yamaguchi, H; Inamori, Y

    1994-01-01

    All the lignans tested in a bioassay with Brassica campestris L. subsp. rapa Hook. fil. et Anders inhibited the root growth of this plant, except for deoxypicropodophyllin. The effects of functional groups in the molecule on the inhibitory activity of these compounds were studied. It is suggested that the methylenedioxyl group and the stereochemical configuration of the lactone junction of podophyllotoxin derivatives were closely related to the inhibitory activity. The O-methyl derivative of two hydroxyl groups of matairesinol greatly enhanced the inhibition of root growth in this plant.

  7. Root growth responses of Anagallis arvensis L., primulaceae to air pollution.

    PubMed

    Khan, F A; Ghouse, A K

    1988-01-01

    The root growth response to air pollution in populations of Anagallis arvensis growing about 0.5, 2, 6, 12 and 20 km leeward from a power plant complex varied with the level of pollution, age of the stand and meteorological conditions. The roots were more affected by the pollutants at a young stage and the loss in net primary productivity was proportional to the pollution level. The populations up to 2 km from the source of pollution completed their life cycle quickly. The coal consumption rate at the power plant, relative humidity, wind direction and other environmental factors were found to influence the degree of growth response to air pollution.

  8. Human life history evolution explains dissociation between the timing of tooth eruption and peak rates of root growth.

    PubMed

    Dean, M Christopher; Cole, Tim J

    2013-01-01

    We explored the relationship between growth in tooth root length and the modern human extended period of childhood. Tooth roots provide support to counter chewing forces and so it is advantageous to grow roots quickly to allow teeth to erupt into function as early as possible. Growth in tooth root length occurs with a characteristic spurt or peak in rate sometime between tooth crown completion and root apex closure. Here we show that in Pan troglodytes the peak in root growth rate coincides with the period of time teeth are erupting into function. However, the timing of peak root velocity in modern humans occurs earlier than expected and coincides better with estimates for tooth eruption times in Homo erectus. With more time to grow longer roots prior to eruption and smaller teeth that now require less support at the time they come into function, the root growth spurt no longer confers any advantage in modern humans. We suggest that a prolonged life history schedule eventually neutralised this adaptation some time after the appearance of Homo erectus. The root spurt persists in modern humans as an intrinsic marker event that shows selection operated, not primarily on tooth tissue growth, but on the process of tooth eruption. This demonstrates the overarching influence of life history evolution on several aspects of dental development. These new insights into tooth root growth now provide an additional line of enquiry that may contribute to future studies of more recent life history and dietary adaptations within the genus Homo. PMID:23342167

  9. Human life history evolution explains dissociation between the timing of tooth eruption and peak rates of root growth.

    PubMed

    Dean, M Christopher; Cole, Tim J

    2013-01-01

    We explored the relationship between growth in tooth root length and the modern human extended period of childhood. Tooth roots provide support to counter chewing forces and so it is advantageous to grow roots quickly to allow teeth to erupt into function as early as possible. Growth in tooth root length occurs with a characteristic spurt or peak in rate sometime between tooth crown completion and root apex closure. Here we show that in Pan troglodytes the peak in root growth rate coincides with the period of time teeth are erupting into function. However, the timing of peak root velocity in modern humans occurs earlier than expected and coincides better with estimates for tooth eruption times in Homo erectus. With more time to grow longer roots prior to eruption and smaller teeth that now require less support at the time they come into function, the root growth spurt no longer confers any advantage in modern humans. We suggest that a prolonged life history schedule eventually neutralised this adaptation some time after the appearance of Homo erectus. The root spurt persists in modern humans as an intrinsic marker event that shows selection operated, not primarily on tooth tissue growth, but on the process of tooth eruption. This demonstrates the overarching influence of life history evolution on several aspects of dental development. These new insights into tooth root growth now provide an additional line of enquiry that may contribute to future studies of more recent life history and dietary adaptations within the genus Homo.

  10. Growth response of Casuarina equisetifolia Forst. rooted stem cuttings to Frankia in nursery and field conditions.

    PubMed

    Karthikeyan, A; Chandrasekaran, K; Geetha, M; Kalaiselvi, R

    2013-11-01

    Casuarina equisetifolia Forst. is a tree crop that provides fuel wood, land reclamation, dune stabilization, and scaffolding for construction, shelter belts, and pulp and paper production. C. equisetifolia fixes atmospheric nitrogen through a symbiotic relationship with Frankia, a soil bacterium of the actinobacteria group. The roots of C. equisetifolia produce root nodules where the bacteria fix atmospheric nitrogen, which is an essential nutrient for all plant metabolic activities. However, rooted stem cuttings of elite clones of C. equisetifolia by vegetative propagation is being planted by the farmers of Pondicherry as costeffective method. As the vegetative propagation method uses inert material (vermiculite) for rooting there is no chance for Frankia association. Therefore after planting of these stocks the farmers are applying 150 kg of di-ammonium phosphate (DAP)/acre/year. To overcome this fertilizer usage, the Frankia-inoculated rooted stem cuttings were propagated under nursery conditions and transplanted in the nutrient-deficient soils of Karaikal, Pondicherry (India), in this study. Under nursery experiments the growth and biomass of C. equisetifolia rooted stem cuttings inoculated with Frankia showed 3 times higher growth and biomass than uninoculated control. These stocks were transplanted and monitored for their growth and survival for 1 year in the nutrient-deficient farm land. The results showed that the rooted stem cuttings of C. equisetifolia significantly improved growth in height (8.8 m), stem girth (9.6 cm) and tissue nitrogen content (3.3 mg g-1) than uninoculated controls. The soil nutrient status was also improved due to inoculation of Frankia. PMID:24287654

  11. Aluminum stress inhibits root growth and alters physiological and metabolic responses in chickpea (Cicer arietinum L.).

    PubMed

    Choudhury, Shuvasish; Sharma, Parul

    2014-12-01

    Chickpea (Cicer arietinum L.) roots were treated with aluminum (Al3+) in calcium chloride (CaCl2) solution (pH 4.7) and growth responses along with physiological and metabolic changes were investigated. Al3+ treatment for 7d resulted in a dose dependent decline of seed germination and inhibition of root growth. A significant (p ≤ 0.05) decline in fresh and dry biomass were observed after 7d of Al3+ stress.The root growth (length) was inhibited after 24 and 48 h of stress imposition. The hydrogen peroxide (H2O2) levels increased significantly (p ≤ 0.05) with respect to control in Al3+ treated roots. The hematoxylin and Evans blue assay indicated significant (p ≤ 0.05) accumulation of Al3+ in the roots and loss of plasma membrane integrity respectively. The time-course evaluation of lipid peroxidation showed increase in malondialdehyde (MDA) after 12, 24 and 48 h of stress imposition. Al3+ treatment did not alter the MDA levels after 2 or 4 h of stress, however, a minor increase was observed after 6 and 10 h of treatment. The proton (1H) nuclear magnetic resonance (NMR) spectrum of the perchloric acid extracts showed variation in the abundance of metabolites and suggested a major metabolic shift in chickpea root during Al3+ stress. The key differences that were observed include changes in energy metabolites. Accumulation of phenolic compounds suggested its possible role in Al3+ exclusion in roots during stress. The results suggested that Al3+ alters growth pattern in chickpea and induces reactive oxygen species (ROS) production that causes physiological and metabolic changes.

  12. AtrbohD and AtrbohF positively regulate abscisic acid-inhibited primary root growth by affecting Ca2+ signalling and auxin response of roots in Arabidopsis.

    PubMed

    Jiao, Yiheng; Sun, Lirong; Song, Yalin; Wang, Limin; Liu, Liping; Zhang, Liyue; Liu, Bo; Li, Ning; Miao, Chen; Hao, Fushun

    2013-11-01

    Reactive oxygen species (ROS) originating from the NADPH oxidases AtrbohD and AtrbohF play an important role in abscisic acid (ABA)-inhibited primary root growth in Arabidopsis. However, the mechanisms underlying this process remain elusive. In this study, the double mutant atrbohD1/F1 and atrbohD2/F2, in which both AtrbohD and AtrbohF were disrupted, were less sensitive to ABA suppression of root cell elongation than wild-type (WT) plants. Furthermore, the double mutants showed impaired ABA responses in roots, including ROS generation, cytosolic Ca(2+) increases, and activation of plasma membrane Ca(2+)-permeable channels compared with WT. Exogenous H2O2 can activate the Ca(2+) currents in roots of atrbohD1/F1. In addition, exogenous application of the auxin transport inhibitor naphthylphthalamic acid effectively promoted ABA inhibition of root growth of the mutants relative to that of WT. The ABA-induced decreases in auxin sensitivity of the root tips were more pronounced in WT than in atrbohD1/F1. These findings suggest that both AtrbohD and AtrbohF are essential for ABA-promoted ROS production in roots. ROS activate Ca(2+) signalling and reduce auxin sensitivity of roots, thus positively regulating ABA-inhibited primary root growth in Arabidopsis.

  13. Antisense expression of an Arabidopsis ran binding protein renders transgenic roots hypersensitive to auxin and alters auxin-induced root growth and development by arresting mitotic progress

    NASA Technical Reports Server (NTRS)

    Kim, S. H.; Arnold, D.; Lloyd, A.; Roux, S. J.

    2001-01-01

    We cloned a cDNA encoding an Arabidopsis Ran binding protein, AtRanBP1c, and generated transgenic Arabidopsis expressing the antisense strand of the AtRanBP1c gene to understand the in vivo functions of the Ran/RanBP signal pathway. The transgenic plants showed enhanced primary root growth but suppressed growth of lateral roots. Auxin significantly increased lateral root initiation and inhibited primary root growth in the transformants at 10 pM, several orders of magnitude lower than required to induce these responses in wild-type roots. This induction was followed by a blockage of mitosis in both newly emerged lateral roots and in the primary root, ultimately resulting in the selective death of cells in the tips of both lateral and primary roots. Given the established role of Ran binding proteins in the transport of proteins into the nucleus, these findings are consistent with a model in which AtRanBP1c plays a key role in the nuclear delivery of proteins that suppress auxin action and that regulate mitotic progress in root tips.

  14. Arabidopsis thaliana Rop GTPases are localized to tips of root hairs and control polar growth.

    PubMed

    Molendijk, A J; Bischoff, F; Rajendrakumar, C S; Friml, J; Braun, M; Gilroy, S; Palme, K

    2001-06-01

    Plants contain a novel unique subfamily of Rho GTPases, vital components of cellular signalling networks. Here we report a general role for some members of this family in polarized plant growth processes. We show that Arabidopsis AtRop4 and AtRop6 encode functional GTPases with similar intrinsic GTP hydrolysis rates. We localized AtRop proteins in root meristem cells to the cross-wall and cell plate membranes. Polar localization of AtRops in trichoblasts specifies the growth sites for emerging root hairs. These sites were visible before budding and elongation of the Arabidopsis root hair when AtRops accumulated at their tips. Expression of constitutively active AtRop4 and AtRop6 mutant proteins in root hairs of transgenic Arabidopsis plants abolished polarized growth and delocalized the tip-focused Ca2+ gradient. Polar localization of AtRops was inhibited by brefeldin A, but not by other drugs such as latrunculin B, cytochalasin D or caffeine. Our results demonstrate a general function of AtRop GTPases in tip growth and in polar diffuse growth.

  15. Seasonal Patterns of Fine Root Production and Turnover in a Mature Rubber Tree (Hevea brasiliensis Müll. Arg.) Stand- Differentiation with Soil Depth and Implications for Soil Carbon Stocks.

    PubMed

    Maeght, Jean-Luc; Gonkhamdee, Santimaitree; Clément, Corentin; Isarangkool Na Ayutthaya, Supat; Stokes, Alexia; Pierret, Alain

    2015-01-01

    Fine root dynamics is a main driver of soil carbon stocks, particularly in tropical forests, yet major uncertainties still surround estimates of fine root production and turnover. This lack of knowledge is largely due to the fact that studying root dynamics in situ, particularly deep in the soil, remains highly challenging. We explored the interactions between fine root dynamics, soil depth, and rainfall in mature rubber trees (Hevea brasiliensis Müll. Arg.) exposed to sub-optimal edaphic and climatic conditions. A root observation access well was installed in northern Thailand to monitor root dynamics along a 4.5 m deep soil profile. Image-based measurements of root elongation and lifespan of individual roots were carried out at monthly intervals over 3 years. Soil depth was found to have a significant effect on root turnover. Surprisingly, root turnover increased with soil depth and root half-life was 16, 6-8, and only 4 months at 0.5, 1.0, 2.5, and 3.0 m deep, respectively (with the exception of roots at 4.5 m which had a half-life similar to that found between depths of 1.0 and 2.5 m). Within the first two meters of the soil profile, the highest rates of root emergence occurred about 3 months after the onset of the rainy season, while deeper in the soil, root emergence was not linked to the rainfall pattern. Root emergence was limited during leaf flushing (between March and May), particularly within the first two meters of the profile. Between soil depths of 0.5 and 2.0 m, root mortality appeared independent of variations in root emergence, but below 2.0 m, peaks in root emergence and death were synchronized. Shallow parts of the root system were more responsive to rainfall than their deeper counterparts. Increased root emergence in deep soil toward the onset of the dry season could correspond to a drought acclimation mechanism, with the relative importance of deep water capture increasing once rainfall ceased. The considerable soil depth regularly explored by

  16. Seasonal Patterns of Fine Root Production and Turnover in a Mature Rubber Tree (Hevea brasiliensis Müll. Arg.) Stand- Differentiation with Soil Depth and Implications for Soil Carbon Stocks.

    PubMed

    Maeght, Jean-Luc; Gonkhamdee, Santimaitree; Clément, Corentin; Isarangkool Na Ayutthaya, Supat; Stokes, Alexia; Pierret, Alain

    2015-01-01

    Fine root dynamics is a main driver of soil carbon stocks, particularly in tropical forests, yet major uncertainties still surround estimates of fine root production and turnover. This lack of knowledge is largely due to the fact that studying root dynamics in situ, particularly deep in the soil, remains highly challenging. We explored the interactions between fine root dynamics, soil depth, and rainfall in mature rubber trees (Hevea brasiliensis Müll. Arg.) exposed to sub-optimal edaphic and climatic conditions. A root observation access well was installed in northern Thailand to monitor root dynamics along a 4.5 m deep soil profile. Image-based measurements of root elongation and lifespan of individual roots were carried out at monthly intervals over 3 years. Soil depth was found to have a significant effect on root turnover. Surprisingly, root turnover increased with soil depth and root half-life was 16, 6-8, and only 4 months at 0.5, 1.0, 2.5, and 3.0 m deep, respectively (with the exception of roots at 4.5 m which had a half-life similar to that found between depths of 1.0 and 2.5 m). Within the first two meters of the soil profile, the highest rates of root emergence occurred about 3 months after the onset of the rainy season, while deeper in the soil, root emergence was not linked to the rainfall pattern. Root emergence was limited during leaf flushing (between March and May), particularly within the first two meters of the profile. Between soil depths of 0.5 and 2.0 m, root mortality appeared independent of variations in root emergence, but below 2.0 m, peaks in root emergence and death were synchronized. Shallow parts of the root system were more responsive to rainfall than their deeper counterparts. Increased root emergence in deep soil toward the onset of the dry season could correspond to a drought acclimation mechanism, with the relative importance of deep water capture increasing once rainfall ceased. The considerable soil depth regularly explored by

  17. Seasonal Patterns of Fine Root Production and Turnover in a Mature Rubber Tree (Hevea brasiliensis Müll. Arg.) Stand- Differentiation with Soil Depth and Implications for Soil Carbon Stocks

    PubMed Central

    Maeght, Jean-Luc; Gonkhamdee, Santimaitree; Clément, Corentin; Isarangkool Na Ayutthaya, Supat; Stokes, Alexia; Pierret, Alain

    2015-01-01

    Fine root dynamics is a main driver of soil carbon stocks, particularly in tropical forests, yet major uncertainties still surround estimates of fine root production and turnover. This lack of knowledge is largely due to the fact that studying root dynamics in situ, particularly deep in the soil, remains highly challenging. We explored the interactions between fine root dynamics, soil depth, and rainfall in mature rubber trees (Hevea brasiliensis Müll. Arg.) exposed to sub-optimal edaphic and climatic conditions. A root observation access well was installed in northern Thailand to monitor root dynamics along a 4.5 m deep soil profile. Image-based measurements of root elongation and lifespan of individual roots were carried out at monthly intervals over 3 years. Soil depth was found to have a significant effect on root turnover. Surprisingly, root turnover increased with soil depth and root half-life was 16, 6–8, and only 4 months at 0.5, 1.0, 2.5, and 3.0 m deep, respectively (with the exception of roots at 4.5 m which had a half-life similar to that found between depths of 1.0 and 2.5 m). Within the first two meters of the soil profile, the highest rates of root emergence occurred about 3 months after the onset of the rainy season, while deeper in the soil, root emergence was not linked to the rainfall pattern. Root emergence was limited during leaf flushing (between March and May), particularly within the first two meters of the profile. Between soil depths of 0.5 and 2.0 m, root mortality appeared independent of variations in root emergence, but below 2.0 m, peaks in root emergence and death were synchronized. Shallow parts of the root system were more responsive to rainfall than their deeper counterparts. Increased root emergence in deep soil toward the onset of the dry season could correspond to a drought acclimation mechanism, with the relative importance of deep water capture increasing once rainfall ceased. The considerable soil depth regularly explored

  18. The control of root growth by reactive oxygen species in Salix nigra Marsh. seedlings.

    PubMed

    Causin, Humberto F; Roqueiro, Gonzalo; Petrillo, Ezequiel; Láinez, Verónica; Pena, Liliana B; Marchetti, Cintia F; Gallego, Susana M; Maldonado, Sara I

    2012-02-01

    The production of reactive oxygen species (ROS) in specific regions of Salix seedlings roots seems essential for the normal growth of this organ. We examined the role of different ROS in the control of root development in Salix nigra seedlings, and explored possible mechanisms involved in the regulation of ROS generation and action. Root growth was not significantly affected by OH quenchers, while it was either partially or completely inhibited in the presence of H₂O₂ or O₂·⁻ scavengers, respectively. O₂·⁻ production was elevated in the root apex, particularly in the subapical meristem and protodermal zones. Apical O₂·⁻ generation activity was correlated to a high level of either Cu/Zn superoxide dismutase protein as well as carbonylated proteins. While NADPH-oxidase (NOX) was probably the main source of O₂·⁻ generation, the existence of other sources should not be discarded. O₂·⁻ production was also high in root hairs during budding, but it markedly decreased when the hair began to actively elongate. Root hair formation increased in the presence of H₂O₂ scavengers, and was suppressed when H₂O₂ or peroxidase inhibitors were supplied. The negative effect of H₂O₂ was partially counteracted by a MAPKK inhibitor. Possible mechanisms of action of the different ROS in comparison with other plant model systems are discussed.

  19. Microbial growth and carbon use efficiency in the rhizosphere and root-free soil.

    PubMed

    Blagodatskaya, Evgenia; Blagodatsky, Sergey; Anderson, Traute-Heidi; Kuzyakov, Yakov

    2014-01-01

    Plant-microbial interactions alter C and N balance in the rhizosphere and affect the microbial carbon use efficiency (CUE)-the fundamental characteristic of microbial metabolism. Estimation of CUE in microbial hotspots with high dynamics of activity and changes of microbial physiological state from dormancy to activity is a challenge in soil microbiology. We analyzed respiratory activity, microbial DNA content and CUE by manipulation the C and nutrients availability in the soil under Beta vulgaris. All measurements were done in root-free and rhizosphere soil under steady-state conditions and during microbial growth induced by addition of glucose. Microorganisms in the rhizosphere and root-free soil differed in their CUE dynamics due to varying time delays between respiration burst and DNA increase. Constant CUE in an exponentially-growing microbial community in rhizosphere demonstrated the balanced growth. In contrast, the CUE in the root-free soil increased more than three times at the end of exponential growth and was 1.5 times higher than in the rhizosphere. Plants alter the dynamics of microbial CUE by balancing the catabolic and anabolic processes, which were decoupled in the root-free soil. The effects of N and C availability on CUE in rhizosphere and root-free soil are discussed. PMID:24722409

  20. Calcium alleviates cadmium-induced inhibition on root growth by maintaining auxin homeostasis in Arabidopsis seedlings.

    PubMed

    Li, Ping; Zhao, Chengzhou; Zhang, Yongqiang; Wang, Xiaomin; Wang, Xiaoyu; Wang, Jianfeng; Wang, Feng; Bi, Yurong

    2016-01-01

    Cadmium (Cd) toxicity has been widely studied in different plant species. However, the mechanism involved in its toxicity and the cell response to Cd has not been well established. In the present study, we investigated the possible mechanism of calcium (Ca) in protecting Arabidopsis from Cd toxicity. The results showed that 50 μM Cd significantly inhibited the seedling growth and decreased the chlorophyll content in Arabidopsis. Specifically, the primary root (PR) length was decreased but the lateral root (LR) number was increased under Cd stress. Furthermore, Cd enhanced the hydrogen peroxide (H2O2) content and lipid peroxidation as indicated by malondialdehyde (MDA) accumulation. Cd also altered the level and the distribution of auxin in PR tips (as evidenced by DR5::GUS and PIN:GFP reporter expression) and the expression of several putative auxin biosynthetic, catabolic, and transport pathway-related genes. Application of 3 mM Ca alleviated the inhibition of Cd on the root growth. Ca application not only led to reducing oxidative injuries but also restoring the normal auxin transport and distribution in Arabidopsis root under Cd stress. Taken together, these results suggest that Ca alleviates the root growth inhibition caused by Cd through maintaining auxin homeostasis in Arabidopsis seedlings.

  1. Temporal variations in cold sensitivity of root growth in cold-stored white spruce seedlings.

    PubMed

    Camm, E L; Harper, G J

    1991-10-01

    We examined effects of soil temperature on the number of roots produced by white spruce (Picea glauca (Moench.) Voss) seedlings during the first month of growth following 0-30 weeks of storage in darkness at -2 degrees C. After storage, seedlings were planted in pots and placed in a controlled-environment chamber with a constant air temperature of 11 degrees C and a 16-h photoperiod. Water baths were used to keep soil temperature at 3, 7 or 11 degrees C. The number of long roots (> 10 mm) produced was strongly dependent on soil temperature. At soil temperatures of 3 or 7 degrees C, the number of long roots produced was only 11 to 30% that at 11 degrees C. Seedlings that had been stored for 14 weeks and then planted in soil at 11 degrees C produced the greatest number of long roots. For seedlings planted in soil at 11 degrees C, the number of long roots increased with time of storage up to 14-18 weeks and then declined progressively with length of storage. No increase in number of long roots with length of storage up to 18 weeks was evident in seedlings planted in soil at 3 or 7 degrees C. The maximum number of short roots (5-10 mm) was observed in seedlings that had been stored for 17 weeks and then planted in soil at 7 or 11 degrees C. PMID:14972852

  2. Spatial separation of light perception and growth response in maize root phototropism.

    PubMed

    Mullen, J L; Wolverton, C; Ishikawa, H; Hangarter, R P; Evans, M L

    2002-09-01

    Although the effects of gravity on root growth are well known and interactions between light and gravity have been reported, details of root phototropic responses are less documented. We used high-resolution image analysis to study phototropism in primary roots of Zea mays L. Similar to the location of perception in gravitropism, the perception of light was localized in the root cap. Phototropic curvature away from the light, on the other hand, developed in the central elongation zone, more basal than the site of initiation of gravitropic curvature. The phototropic curvature saturated at approximately 10 micromoles m-2 s-1 blue light with a peak curvature of 29 +/- 4 degrees, in part due to induction of positive gravitropism following displacement of the root tip from vertical during negative phototropism. However, at higher fluence rates, development of phototropic curvature is arrested even if gravitropism is avoided by maintaining the root cap vertically using a rotating feedback system. Thus continuous illumination can cause adaptation in the signalling pathway of the phototropic response in roots. PMID:12361060

  3. Spatial separation of light perception and growth response in maize root phototropism.

    PubMed

    Mullen, J L; Wolverton, C; Ishikawa, H; Hangarter, R P; Evans, M L

    2002-09-01

    Although the effects of gravity on root growth are well known and interactions between light and gravity have been reported, details of root phototropic responses are less documented. We used high-resolution image analysis to study phototropism in primary roots of Zea mays L. Similar to the location of perception in gravitropism, the perception of light was localized in the root cap. Phototropic curvature away from the light, on the other hand, developed in the central elongation zone, more basal than the site of initiation of gravitropic curvature. The phototropic curvature saturated at approximately 10 micromoles m-2 s-1 blue light with a peak curvature of 29 +/- 4 degrees, in part due to induction of positive gravitropism following displacement of the root tip from vertical during negative phototropism. However, at higher fluence rates, development of phototropic curvature is arrested even if gravitropism is avoided by maintaining the root cap vertically using a rotating feedback system. Thus continuous illumination can cause adaptation in the signalling pathway of the phototropic response in roots.

  4. Spatial separation of light perception and growth response in maize root phototropism

    NASA Technical Reports Server (NTRS)

    Mullen, J. L.; Wolverton, C.; Ishikawa, H.; Hangarter, R. P.; Evans, M. L.

    2002-01-01

    Although the effects of gravity on root growth are well known and interactions between light and gravity have been reported, details of root phototropic responses are less documented. We used high-resolution image analysis to study phototropism in primary roots of Zea mays L. Similar to the location of perception in gravitropism, the perception of light was localized in the root cap. Phototropic curvature away from the light, on the other hand, developed in the central elongation zone, more basal than the site of initiation of gravitropic curvature. The phototropic curvature saturated at approximately 10 micromoles m-2 s-1 blue light with a peak curvature of 29 +/- 4 degrees, in part due to induction of positive gravitropism following displacement of the root tip from vertical during negative phototropism. However, at higher fluence rates, development of phototropic curvature is arrested even if gravitropism is avoided by maintaining the root cap vertically using a rotating feedback system. Thus continuous illumination can cause adaptation in the signalling pathway of the phototropic response in roots.

  5. Root growth of Lotus corniculatus interacts with P distribution in young sandy soil

    NASA Astrophysics Data System (ADS)

    Felderer, B.; Boldt-Burisch, K. M.; Schneider, B. U.; Hüttl, R. F. J.; Schulin, R.

    2013-03-01

    Large areas of land are restored with unweathered soil substrates following mining activities in eastern Germany and elsewhere. In the initial stages of colonization of such land by vegetation, plant roots may become key agents in generating soil formation patterns by introducing gradients in chemical and physical soil properties. On the other hand, such patterns may be influenced by root growth responses to pre-existing substrate heterogeneities. In particular, the roots of many plants were found to preferentially proliferate into nutrient-rich patches. Phosphorus (P) is of primary interest in this respect because its availability is often low in unweathered soils, limiting especially the growth of leguminous plants. However, leguminous plants occur frequently among the pioneer plant species on such soils, as they only depend on atmospheric nitrogen (N) fixation as N source. In this study we investigated the relationship between root growth allocation of the legume Lotus corniculatus and soil P distribution on recently restored land. As test sites, the experimental Chicken Creek Catchment (CCC) in eastern Germany and a nearby experimental site (ES) with the same soil substrate were used. We established two experiments with constructed heterogeneity, one in the field on the experimental site and the other in a climate chamber. In addition, we conducted high-density samplings on undisturbed soil plots colonized by L. corniculatus on the ES and on the CCC. In the field experiment, we installed cylindrical ingrowth soil cores (4.5 × 10 cm) with and without P fertilization around single two-month-old L. corniculatus plants. Roots showed preferential growth into the P-fertilized ingrowth-cores. Preferential root allocation was also found in the climate chamber experiment, where single L. corniculatus plants were grown in containers filled with ES soil and where a lateral portion of the containers was additionally supplied with a range of different P concentrations. In

  6. Root growth of Lotus corniculatus interacts with P distribution in young sandy soil

    NASA Astrophysics Data System (ADS)

    Felderer, B.; Boldt-Burisch, K. M.; Schneider, B. U.; Hüttl, R. F. J.; Schulin, R.

    2012-07-01

    Large areas of land are restored with un-weathered soil substrates following mining activities in eastern Germany and elsewhere. In the initial stages of colonization of such land by vegetation, plant roots may become key agents in generating soil formation patterns by introducing gradients in chemical and physical soil properties. On the other hand, such patterns may be influenced by root growth responses to pre-existing substrate heterogeneities. In particular, the roots of many plants were found to preferentially proliferate into nutrient-rich patches. Phosphorus (P) is of primary interest in this respect because its availability is often low in unweathered soils, limiting especially the growth of leguminous plants. However, leguminous plants occur frequently among the pioneer plant species on such soils as they only depend on atmospheric nitrogen (N) fixation as N source. In this study we investigated the relationship between root growth allocation of the legume Lotus corniculatus and soil P distribution on recently restored land. As test sites the experimental Chicken Creek Catchment (CCC) in eastern Germany and a nearby experimental site (ES) with the same soil substrate were used. We established two experiments with constructed heterogeneity, one in the field on the experimental site and the other in a climate chamber. In addition we conducted high-density samplings on undisturbed soil plots colonized by L. corniculatus on the ES and on the CCC. In the field experiment, we installed cylindrical ingrowth soil cores (4.5×10 cm) with and without P fertilization around single two-month-old L. corniculatus plants. Roots showed preferential growth into the P-fertilized ingrowth-cores. Preferential root allocation was also found in the climate chamber experiment, where single L. corniculatus plants were grown in containers filled with ES soil and where a lateral portion of the containers was additionally supplied with a range of different P concentrations. In the

  7. Modeling hairy root tissue growth in in vitro environments using an agent-based, structured growth model.

    PubMed

    Lenk, Felix; Sürmann, Almuth; Oberthür, Patrick; Schneider, Mandy; Steingroewer, Juliane; Bley, Thomas

    2014-06-01

    An agent-based model for simulating the in vitro growth of Beta vulgaris hairy root cultures is described. The model fitting is based on experimental results and can be used as a virtual experimentator for root networks. It is implemented in the JAVA language and is designed to be easily modified to describe the growth of diverse biological root networks. The basic principles of the model are outlined, with descriptions of all of the relevant algorithms using the ODD protocol, and a case study is presented in which it is used to simulate the development of hairy root cultures of beetroot (Beta vulgaris) in a Petri dish. The model can predict various properties of the developing network, including the total root length, branching point distribution, segment distribution and secondary metabolite accumulation. It thus provides valuable information that can be used when optimizing cultivation parameters (e.g., medium composition) and the cultivation environment (e.g., the cultivation temperature) as well as how constructional parameters change the morphology of the root network. An image recognition solution was used to acquire experimental data that were used when fitting the model and to evaluate the agreement between the simulated results and practical experiments. Overall, the case study simulation closely reproduced experimental results for the cultures grown under equivalent conditions to those assumed in the simulation. A 3D-visualization solution was created to display the simulated results relating to the state of the root network and its environment (e.g., oxygen and nutrient levels). PMID:24218303

  8. The effect of ethylene on root growth of Zea mays seedlings

    NASA Technical Reports Server (NTRS)

    Whalen, M. C.; Feldman, L. J.

    1988-01-01

    The control of primary root growth in Zea mays cv. Merit by ethylene was examined. At applied concentrations of ethylene equal to or greater than 0.1 microliter L-1, root elongation during 24 h was inhibited. The half-maximal response occurred at 0.6 microliter L-1 and the response saturated at 6 microliters L-1. Inhibition of elongation took place within 20 min. However, after ethylene was removed, elongation recovered to control values within 15 min. Root elongation was also inhibited by green light. The inhibition caused by a 24-h exposure to ethylene was restricted to the elongating region just behind the apex, with inhibition of cortical cell elongation being the primary contributor to the effect. Based on use of 2,5-norbornadiene, a gaseous competitive inhibitor of ethylene, it was concluded that endogenous ethylene normally inhibits root elongation.

  9. [Effects of water storage in deeper soil layers on the root growth, root distribution and economic yield of cotton in arid area with drip irrigation under mulch].

    PubMed

    Luo, Hong-Hai; Zhang, Hong-Zhi; Zhang, Ya-Li; Zhang, Wang-Feng

    2012-02-01

    Taking cotton cultivar Xinluzao 13 as test material, a soil column culture expenment was conducted to study the effects of water storage in deeper (> 60 cm) soil layer on the root growth and its relations with the aboveground growth of the cultivar in arid area with drip irrigation under mulch. Two levels of water storage in 60-120 cm soil layer were installed, i. e., well-watered and no watering, and for each, the moisture content in 0-40 cm soil layer during growth period was controlled at two levels, i.e., 70% and 55% of field capacity. It was observed that the total root mass density of the cultivar and its root length density and root activity in 40-120 cm soil layer had significant positive correlations with the aboveground dry mass. When the moisture content in 0-40 cm soil layer during growth season was controlled at 70% of field capacity, the total root mass density under well-watered and no watering had less difference, but the root length density and root activity in 40-120 cm soil layer under well-watered condition increased, which enhanced the water consumption in deeper soil layer, increased the aboveground dry mass, and finally, led to an increased economic yield and higher water use efficiency. When the moisture content in 0-40 cm soil layer during growth season was controlled at 55% of field capacity and the deeper soil layer was well-watered, the root/shoot ratio and root length density in 40-120 cm soil layer and the root activity in 80-120 cm soil layer were higher, the water consumption in deeper soil layer increased, but it was still failed to adequately compensate for the negative effects of water deficit during growth season on the impaired growth of roots and aboveground parts, leading to a significant decrease in the economic yield, as compared with that at 70% of field capacity. Overall, sufficient water storage in deeper soil layer and a sustained soil moisture level of 65% -75% of field capacity during growth period could promote the

  10. A Galacturonic Acid–Containing Xyloglucan Is Involved in Arabidopsis Root Hair Tip Growth[W

    PubMed Central

    Peña, Maria J.; Kong, Yingzhen; York, William S.; O’Neill, Malcolm A.

    2012-01-01

    Root hairs provide a model system to study plant cell growth, yet little is known about the polysaccharide compositions of their walls or the role of these polysaccharides in wall expansion. We report that Arabidopsis thaliana root hair walls contain a previously unidentified xyloglucan that is composed of both neutral and galacturonic acid–containing subunits, the latter containing the β-d-galactosyluronic acid-(1→2)-α-d-xylosyl-(1→ and/or α-l-fucosyl-(1→2)-β-d-galactosyluronic acid-(1→2)-α-d-xylosyl-(1→) side chains. Arabidopsis mutants lacking root hairs have no acidic xyloglucan. A loss-of-function mutation in At1g63450, a root hair–specific gene encoding a family GT47 glycosyltransferase, results in the synthesis of xyloglucan that lacks galacturonic acid. The root hairs of this mutant are shorter than those of the wild type. This mutant phenotype and the absence of galacturonic acid in the root xyloglucan are complemented by At1g63450. The leaf and stem cell walls of wild-type Arabidopsis contain no acidic xyloglucan. However, overexpression of At1g63450 led to the synthesis of galacturonic acid–containing xyloglucan in these tissues. We propose that At1g63450 encodes XYLOGLUCAN-SPECIFIC GALACTURONOSYLTRANSFERASE1, which catalyzes the formation of the galactosyluronic acid-(1→2)-α-d-xylopyranosyl linkage and that the acidic xyloglucan is present only in root hair cell walls. The role of the acidic xyloglucan in root hair tip growth is discussed. PMID:23175743

  11. Multiscale Systems Analysis of Root Growth and Development: Modeling Beyond the Network and Cellular Scales

    PubMed Central

    Band, Leah R.; Fozard, John A.; Godin, Christophe; Jensen, Oliver E.; Pridmore, Tony; Bennett, Malcolm J.; King, John R.

    2012-01-01

    Over recent decades, we have gained detailed knowledge of many processes involved in root growth and development. However, with this knowledge come increasing complexity and an increasing need for mechanistic modeling to understand how those individual processes interact. One major challenge is in relating genotypes to phenotypes, requiring us to move beyond the network and cellular scales, to use multiscale modeling to predict emergent dynamics at the tissue and organ levels. In this review, we highlight recent developments in multiscale modeling, illustrating how these are generating new mechanistic insights into the regulation of root growth and development. We consider how these models are motivating new biological data analysis and explore directions for future research. This modeling progress will be crucial as we move from a qualitative to an increasingly quantitative understanding of root biology, generating predictive tools that accelerate the development of improved crop varieties. PMID:23110897

  12. 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. PMID:26654319

  13. Multiscale systems analysis of root growth and development: modeling beyond the network and cellular scales.

    PubMed

    Band, Leah R; Fozard, John A; Godin, Christophe; Jensen, Oliver E; Pridmore, Tony; Bennett, Malcolm J; King, John R

    2012-10-01

    Over recent decades, we have gained detailed knowledge of many processes involved in root growth and development. However, with this knowledge come increasing complexity and an increasing need for mechanistic modeling to understand how those individual processes interact. One major challenge is in relating genotypes to phenotypes, requiring us to move beyond the network and cellular scales, to use multiscale modeling to predict emergent dynamics at the tissue and organ levels. In this review, we highlight recent developments in multiscale modeling, illustrating how these are generating new mechanistic insights into the regulation of root growth and development. We consider how these models are motivating new biological data analysis and explore directions for future research. This modeling progress will be crucial as we move from a qualitative to an increasingly quantitative understanding of root biology, generating predictive tools that accelerate the development of improved crop varieties.

  14. Plant growth in elevated CO2 alters mitochondrial number and chloroplast fine structure

    PubMed Central

    Griffin, Kevin L.; Anderson, O. Roger; Gastrich, Mary D.; Lewis, James D.; Lin, Guanghui; Schuster, William; Seemann, Jeffrey R.; Tissue, David T.; Turnbull, Matthew H.; Whitehead, David

    2001-01-01

    With increasing interest in the effects of elevated atmospheric CO2 on plant growth and the global carbon balance, there is a need for greater understanding of how plants respond to variations in atmospheric partial pressure of CO2. Our research shows that elevated CO2 produces significant fine structural changes in major cellular organelles that appear to be an important component of the metabolic responses of plants to this global change. Nine species (representing seven plant families) in several experimental facilities with different CO2-dosing technologies were examined. Growth in elevated CO2 increased numbers of mitochondria per unit cell area by 1.3–2.4 times the number in control plants grown in lower CO2 and produced a statistically significant increase in the amount of chloroplast stroma (nonappressed) thylakoid membranes compared with those in lower CO2 treatments. There was no observable change in size of the mitochondria. However, in contrast to the CO2 effect on mitochondrial number, elevated CO2 promoted a decrease in the rate of mass-based dark respiration. These changes may reflect a major shift in plant metabolism and energy balance that may help to explain enhanced plant productivity in response to elevated atmospheric CO2 concentrations. PMID:11226263

  15. Scanning electron microscopic investigations of root structural modifications arising from growth in crude oil-contaminated sand.

    PubMed

    Balasubramaniyam, Anuluxshy; Harvey, Patricia J

    2014-11-01

    The choice of plant for phytoremediation success requires knowledge of how plants respond to contaminant exposure, especially their roots which are instrumental in supporting rhizosphere activity. In this study, we investigated the responses of plants with different architectures represented by beetroot (Beta vulgaris), a eudicot with a central taproot and many narrower lateral roots, and tall fescue (Festuca arundinacea), a monocot possessing a mass of threadlike fibrous roots to grow in crude oil-treated sand. In this paper, scanning electron microscopy was used to investigate modifications to plant root structure caused by growth in crude oil-contaminated sand. Root structural disorders were evident and included enhanced thickening in the endodermis, increased width of the root cortical zone and smaller diameter of xylem vessels. Inhibition in the rate of root elongation correlated with the increase in cell wall thickening and was dramatically pronounced in beetroot compared to the roots of treated fescue. The latter possessed significantly fewer (p < 0.001) and significantly shorter (p < 0.001) root hairs compared to control plants. Possibly, root hairs that absorb the hydrophobic contaminants may prevent contaminant absorption into the main root and concomitant axile root thickening by being sloughed off from roots. Tall fescue exhibited greater root morphological adaptability to growth in crude oil-treated sand than beetroot and, thus, a potential for long-term phytoremediation. PMID:24958531

  16. Clinorotation influence on the growth of root hairs in Beta Vulgaris L. seedlings

    NASA Astrophysics Data System (ADS)

    Shevchenko, G. V.; Kordyum, E. L.

    It is shown that clinorotation affects the angle of Beta Vulgaris L. root hair growth and changes it from 85-95° to 40-60° at the stage of hair initiation. The investigation of actin cytoskeleton arrangement and tip-based gradient of calcium ions proved the involvement of above components in the maintenance of the directed growth in simulated microgravity (clinorotation).

  17. Mathematical Modeling of the Dynamics of Shoot-Root Interactions and Resource Partitioning in Plant Growth.

    PubMed

    Feller, Chrystel; Favre, Patrick; Janka, Ales; Zeeman, Samuel C; Gabriel, Jean-Pierre; Reinhardt, Didier

    2015-01-01

    Plants are highly plastic in their potential to adapt to changing environmental conditions. For example, they can selectively promote the relative growth of the root and the shoot in response to limiting supply of mineral nutrients and light, respectively, a phenomenon that is referred to as balanced growth or functional equilibrium. To gain insight into the regulatory network that controls this phenomenon, we took a systems biology approach that combines experimental work with mathematical modeling. We developed a mathematical model representing the activities of the root (nutrient and water uptake) and the shoot (photosynthesis), and their interactions through the exchange of the substrates sugar and phosphate (Pi). The model has been calibrated and validated with two independent experimental data sets obtained with Petunia hybrida. It involves a realistic environment with a day-and-night cycle, which necessitated the introduction of a transitory carbohydrate storage pool and an endogenous clock for coordination of metabolism with the environment. Our main goal was to grasp the dynamic adaptation of shoot:root ratio as a result of changes in light and Pi supply. The results of our study are in agreement with balanced growth hypothesis, suggesting that plants maintain a functional equilibrium between shoot and root activity based on differential growth of these two compartments. Furthermore, our results indicate that resource partitioning can be understood as the emergent property of many local physiological processes in the shoot and the root without explicit partitioning functions. Based on its encouraging predictive power, the model will be further developed as a tool to analyze resource partitioning in shoot and root crops.

  18. Mathematical Modeling of the Dynamics of Shoot-Root Interactions and Resource Partitioning in Plant Growth.

    PubMed

    Feller, Chrystel; Favre, Patrick; Janka, Ales; Zeeman, Samuel C; Gabriel, Jean-Pierre; Reinhardt, Didier

    2015-01-01

    Plants are highly plastic in their potential to adapt to changing environmental conditions. For example, they can selectively promote the relative growth of the root and the shoot in response to limiting supply of mineral nutrients and light, respectively, a phenomenon that is referred to as balanced growth or functional equilibrium. To gain insight into the regulatory network that controls this phenomenon, we took a systems biology approach that combines experimental work with mathematical modeling. We developed a mathematical model representing the activities of the root (nutrient and water uptake) and the shoot (photosynthesis), and their interactions through the exchange of the substrates sugar and phosphate (Pi). The model has been calibrated and validated with two independent experimental data sets obtained with Petunia hybrida. It involves a realistic environment with a day-and-night cycle, which necessitated the introduction of a transitory carbohydrate storage pool and an endogenous clock for coordination of metabolism with the environment. Our main goal was to grasp the dynamic adaptation of shoot:root ratio as a result of changes in light and Pi supply. The results of our study are in agreement with balanced growth hypothesis, suggesting that plants maintain a functional equilibrium between shoot and root activity based on differential growth of these two compartments. Furthermore, our results indicate that resource partitioning can be understood as the emergent property of many local physiological processes in the shoot and the root without explicit partitioning functions. Based on its encouraging predictive power, the model will be further developed as a tool to analyze resource partitioning in shoot and root crops. PMID:26154262

  19. Mathematical Modeling of the Dynamics of Shoot-Root Interactions and Resource Partitioning in Plant Growth

    PubMed Central

    Feller, Chrystel; Favre, Patrick; Janka, Ales; Zeeman, Samuel C.; Gabriel, Jean-Pierre; Reinhardt, Didier

    2015-01-01

    Plants are highly plastic in their potential to adapt to changing environmental conditions. For example, they can selectively promote the relative growth of the root and the shoot in response to limiting supply of mineral nutrients and light, respectively, a phenomenon that is referred to as balanced growth or functional equilibrium. To gain insight into the regulatory network that controls this phenomenon, we took a systems biology approach that combines experimental work with mathematical modeling. We developed a mathematical model representing the activities of the root (nutrient and water uptake) and the shoot (photosynthesis), and their interactions through the exchange of the substrates sugar and phosphate (Pi). The model has been calibrated and validated with two independent experimental data sets obtained with Petunia hybrida. It involves a realistic environment with a day-and-night cycle, which necessitated the introduction of a transitory carbohydrate storage pool and an endogenous clock for coordination of metabolism with the environment. Our main goal was to grasp the dynamic adaptation of shoot:root ratio as a result of changes in light and Pi supply. The results of our study are in agreement with balanced growth hypothesis, suggesting that plants maintain a functional equilibrium between shoot and root activity based on differential growth of these two compartments. Furthermore, our results indicate that resource partitioning can be understood as the emergent property of many local physiological processes in the shoot and the root without explicit partitioning functions. Based on its encouraging predictive power, the model will be further developed as a tool to analyze resource partitioning in shoot and root crops. PMID:26154262

  20. Two distinct regions of response drive differential growth in Vigna root electrotropism

    NASA Technical Reports Server (NTRS)

    Wolverton, C.; Mullen, J. L.; Ishikawa, H.; Evans, M. L.

    2000-01-01

    Although exogenous electric fields have been reported to influence the orientation of plant root growth, reports of the ultimate direction of differential growth have been contradictory. Using a high-resolution image analysis approach, the kinetics of electrotropic curvature in Vigna mungo L. roots were investigated. It was found that curvature occurred in the same root toward both the anode and cathode. However, these two responses occurred in two different regions of the root, the central elongation zone (CEZ) and distal elongation zone (DEZ), respectively. These oppositely directed responses could be reproduced individually by a localized electric field application to the region of response. This indicates that both are true responses to the electric field, rather than one being a secondary response to an induced gravitropic stimulation. The individual responses differed in the type of differential growth giving rise to curvature. In the CEZ, curvature was driven by inhibition of elongation, whereas curvature in the DEZ was primarily due to stimulation of elongation. This stimulation of elongation is consistent with the growth response of the DEZ to other environmental stimuli.

  1. Soybean root growth in acid subsoils in relation to magnesium additions and soil solution ionic strength

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hydroponic studies with soybean [Glycine max (L.) Merr.] have shown that µM additions of Mg2+ were as effective in ameliorating Al rhizotoxicity as additions of Ca2+ in the mM concentration range. The objectives of this study were to assess ameliorative effects of Mg on soybean root growth in acidic...

  2. TAA1-regulated local auxin biosynthesis in the root-apex transition zone mediates the aluminum-induced inhibition of root growth in Arabidopsis.

    PubMed

    Yang, Zhong-Bao; Geng, Xiaoyu; He, Chunmei; Zhang, Feng; Wang, Rong; Horst, Walter J; Ding, Zhaojun

    2014-07-01

    The transition zone (TZ) of the root apex is the perception site of Al toxicity. Here, we show that exposure of Arabidopsis thaliana roots to Al induces a localized enhancement of auxin signaling in the root-apex TZ that is dependent on TAA1, which encodes a Trp aminotransferase and regulates auxin biosynthesis. TAA1 is specifically upregulated in the root-apex TZ in response to Al treatment, thus mediating local auxin biosynthesis and inhibition of root growth. The TAA1-regulated local auxin biosynthesis in the root-apex TZ in response to Al stress is dependent on ethylene, as revealed by manipulating ethylene homeostasis via the precursor of ethylene biosynthesis 1-aminocyclopropane-1-carboxylic acid, the inhibitor of ethylene biosynthesis aminoethoxyvinylglycine, or mutant analysis. In response to Al stress, ethylene signaling locally upregulates TAA1 expression and thus auxin responses in the TZ and results in auxin-regulated root growth inhibition through a number of auxin response factors (ARFs). In particular, ARF10 and ARF16 are important in the regulation of cell wall modification-related genes. Our study suggests a mechanism underlying how environmental cues affect root growth plasticity through influencing local auxin biosynthesis and signaling.

  3. Effect of growth regulators and role of roots in sex expression in spinach.

    PubMed

    Chailakhyan, M K; Khryanin, V N

    1978-01-01

    When 7-d-old plantlets of spinach (Spinacia oleracea L.) were immersed with their roots for 24