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Aims: Our understanding of the rhizosphere is limited by the lack of techniques for in situ live microscopy. Current techniques are either destructive or unsuitable for observing chemical changes within the pore space. To address this limitation, we have developed artificial substrates, termed smart soils, that enable the acquisition and 3D reconstruction of chemical sensors attached to soil particles. Methods: The transparency of smart soils was achieved using polymer particles with refractive index matching that of water. The surface of the particles was modified both to retain water and act as a local sensor to report on pore space pH via fluorescence emissions. Multispectral signals were acquired from the particles using a light sheet microscope, and machine learning algorithms predicted the changes and spatial distribution in pH at the surface of the smart soil particles. Results: The technique was able to predict pH live and in situ within ± 0.5 units of the true pH value. pH distribution could be reconstructed across a volume of several cubic centimetres around plant roots at 10 μm resolution. Using smart soils of different composition, we revealed how root exudation and pore structure create variability in chemical properties. Conclusion: Smart soils captured the pH gradients forming around a growing plant root. Future developments of the technology could include the fine tuning of soil physicochemical properties, the addition of chemical sensors and improved data processing. Hence, this technology could play a critical role in advancing our understanding of complex rhizosphere processes. [ABSTRACT FROM AUTHOR]

Background and Aim: The deep placement (DP) of fertilizers is a key strategy to improve fertilizer-use efficiency in rice production. In this study, we assessed the effect of DP with nitrogen (N), phosphorus (P), and potassium (K) fertilizers on the spatial distribution of root system architecture (RSA) and evaluated the combined effect of DP fertilization and RSA on essential mineral uptake. Methods: A three-year field experiment was conducted using the Akitakomachi rice cultivar with three fertilization treatments: Mix (broadcast), DP1 (one-position-DP at 7 or 10 cm soil depth), and DP2 (two-position-DP at 7 and 15 cm depth). A root box experiment was conducted to quantify the responses of RSA. The root morphological traits were measured in the field and root box experiments. Results: The amount of mineral uptake of N, P, and K, applied as fertilizers, and other minerals such as calcium and magnesium during ripening period, was significantly increased by DP. DP resulted in changing the RSA with greater root surface area and thicker roots (with a diameter of 0.1–0.4 mm) accumulation in deep soil layers at the fertilizer position. Root box experiments also supported root accumulation at localized fertilizer position. Conclusion: DP helped maintain a continuous nutrient supply during ripening by promoting root accumulation at the fertilizer position. The ability of roots to accumulate toward fertilizer can be an effective strategy for creating an ideal RSA for better mineral uptake, which can reduce the fertilizer input required to achieve sustainable rice production. [ABSTRACT FROM AUTHOR]

Purpose: Alternate wetting and moderate soil drying irrigation (WMD) and nitrogen fertilizer at panicle initiation are widely used in rice production in China. This study investigated the effects of panicle fertilizer optimization on rice root growth, soil properties and grain yield under continuous flooding (CF) and WMD. Methods: A factorial combination of two irrigation regimes (CF and WMD) and two N fertilizer rates at panicle initiation (normal N rate [NN] and low N rate [LN]) was designed in both field and pot conditions in 2018–2019. Results: Grain yield declined in the order: WMD + NN > CF + NN = WMD + LN > CF + LN. WMD increased grain yield by notably increasing the spikelet number per panicle (SNPP) and could counteract the negative effect of LN. WMD enhanced root morphology and physiology, which was remarkably correlated with SNPP. The urease activity, oxygen content, and the abundance of ammonia-oxidizing archaea/bacteria in rhizosphere soil were significantly increased under WMD compared to CF but were decreased in LN relative to NN under the same irrigation regime. The rice root length, root dry weight, root diameter, root oxidation activity, and soil nitrification rates under WMD + LN were similar to those under CF + NN. Rice root morphology and activity promoted by the enhanced nitrification process and decreased NH4+/NO3– ratio under WMD facilitated a higher grain yield. Conclusion: Combining WMD with LN at panicle initiation could maintain the rice root growth, leading to comparable grain yields but higher nitrogen use efficiency than the farmers' practice. [ABSTRACT FROM AUTHOR]

Aims: The alkaloid hordenine is one of the major allelochemicals involved in the allelopathic ability of barley (Hordeum vulgare L.), whose biosynthesis and accumulation is preferentially located in roots. Hordenine appears to have been unintentionally favored during domestication in modern and cultivated barley cultivars at the expense of another alkaloid, gramine. In this study, we assessed the content of hordenine and its two precursors, N-methyltyramine (NMT) and tyramine, in roots and root exudates of the modern spring barley cv. Solist, and particularly how they are affected due to nutrient deficiencies. Methods: We monitored the three metabolites during the early phases of barley growth i.e., up to 8 days, applying HPLC time-course and both target and untargeted metabolomic approaches. Barley plants were grown either in full nutrient solutions or in specific nutrient shortage conditions (N, S, P and Fe). Results: Results confirmed a strong decrease of the allelochemical accumulation (hordenine and the two precursors) in roots and in root exudates during both 24 h and 8 days time-course experiments. Yet, the overall tyramine content was approximately tenfold lower compared to the other two compounds. In addition, plants subjected to nitrogen (-N), sulfur (-S), phosphorus (-P) and iron (-Fe) deprivation showed nutrient-dependent accumulation of hordenine, N-methyltyramine and tyramine, as well as of other secondary metabolites. Indeed, the synthesis of hordenine and N-methyltyramine was trigged under nutrient deficiencies. Conclusions: In conclusion, this study highlighted the impact of nutrient availability on the growth-dependent accumulation patterns of all the three compounds investigated in modern barley roots. [ABSTRACT FROM AUTHOR]

Aims: Phosphorus (P) is essential for Brassica napus L. (B. napus) growth and development, but most P in soil is unavailable. Evidence shows that BnaPHT1s react to a range of nutritional stresses and heavy metals. However, little is known about the mechanism of BnaPHT1s in B. napus. Therefore, the present study aimed to characterize the members of the BnaPHT1 in allotetraploid B. napus and to analyze their expression profile in response to environmental stresses. BnaPHT1;4 J is a member of the little-known mechanism in this regard. We used Xiaoyun (XY) to investigate the effect of BnaPHT1;4 J on phosphate (Pi) uptake.In this study, we identified a novel member of PHT1;4 subfamily in B. napus, which is highly expressed in root under low Pi stress, and named it BnaPHT1;4 J. We further characterized the role of BnaPHT1;4 J for Pi uptake in B. napus. Quantitative RT-PCR, onion subcellular localization, and GUS expression analysis reveal that BnaPHT1;4 J is a membrane protein that is mainly localized at roots under low Pi conditions.Phenotypic characterization showed that BnaPHT1;4 J overexpression under low Pi promoted root growth and main root elongation in Arabidopsis and B. napus, and other physiological indicators such as P content and biomass in B. napus were also positively regulated.BnaPHT1;4 J has a catalytic effect on seedlings and nutritional growth of B. napus and promotes Pi uptake and translocation.Methods: Phosphorus (P) is essential for Brassica napus L. (B. napus) growth and development, but most P in soil is unavailable. Evidence shows that BnaPHT1s react to a range of nutritional stresses and heavy metals. However, little is known about the mechanism of BnaPHT1s in B. napus. Therefore, the present study aimed to characterize the members of the BnaPHT1 in allotetraploid B. napus and to analyze their expression profile in response to environmental stresses. BnaPHT1;4 J is a member of the little-known mechanism in this regard. We used Xiaoyun (XY) to investigate the effect of BnaPHT1;4 J on phosphate (Pi) uptake.In this study, we identified a novel member of PHT1;4 subfamily in B. napus, which is highly expressed in root under low Pi stress, and named it BnaPHT1;4 J. We further characterized the role of BnaPHT1;4 J for Pi uptake in B. napus. Quantitative RT-PCR, onion subcellular localization, and GUS expression analysis reveal that BnaPHT1;4 J is a membrane protein that is mainly localized at roots under low Pi conditions.Phenotypic characterization showed that BnaPHT1;4 J overexpression under low Pi promoted root growth and main root elongation in Arabidopsis and B. napus, and other physiological indicators such as P content and biomass in B. napus were also positively regulated.BnaPHT1;4 J has a catalytic effect on seedlings and nutritional growth of B. napus and promotes Pi uptake and translocation.Results: Phosphorus (P) is essential for Brassica napus L. (B. napus) growth and development, but most P in soil is unavailable. Evidence shows that BnaPHT1s react to a range of nutritional stresses and heavy metals. However, little is known about the mechanism of BnaPHT1s in B. napus. Therefore, the present study aimed to characterize the members of the BnaPHT1 in allotetraploid B. napus and to analyze their expression profile in response to environmental stresses. BnaPHT1;4 J is a member of the little-known mechanism in this regard. We used Xiaoyun (XY) to investigate the effect of BnaPHT1;4 J on phosphate (Pi) uptake.In this study, we identified a novel member of PHT1;4 subfamily in B. napus, which is highly expressed in root under low Pi stress, and named it BnaPHT1;4 J. We further characterized the role of BnaPHT1;4 J for Pi uptake in B. napus. Quantitative RT-PCR, onion subcellular localization, and GUS expression analysis reveal that BnaPHT1;4 J is a membrane protein that is mainly localized at roots under low Pi conditions.Phenotypic characterization showed that BnaPHT1;4 J overexpression under low Pi promoted root growth and main root elongation in Arabidopsis and B. napus, and other physiological indicators such as P content and biomass in B. napus were also positively regulated.BnaPHT1;4 J has a catalytic effect on seedlings and nutritional growth of B. napus and promotes Pi uptake and translocation.Conclusions: Phosphorus (P) is essential for Brassica napus L. (B. napus) growth and development, but most P in soil is unavailable. Evidence shows that BnaPHT1s react to a range of nutritional stresses and heavy metals. However, little is known about the mechanism of BnaPHT1s in B. napus. Therefore, the present study aimed to characterize the members of the BnaPHT1 in allotetraploid B. napus and to analyze their expression profile in response to environmental stresses. BnaPHT1;4 J is a member of the little-known mechanism in this regard. We used Xiaoyun (XY) to investigate the effect of BnaPHT1;4 J on phosphate (Pi) uptake.In this study, we identified a novel member of PHT1;4 subfamily in B. napus, which is highly expressed in root under low Pi stress, and named it BnaPHT1;4 J. We further characterized the role of BnaPHT1;4 J for Pi uptake in B. napus. Quantitative RT-PCR, onion subcellular localization, and GUS expression analysis reveal that BnaPHT1;4 J is a membrane protein that is mainly localized at roots under low Pi conditions.Phenotypic characterization showed that BnaPHT1;4 J overexpression under low Pi promoted root growth and main root elongation in Arabidopsis and B. napus, and other physiological indicators such as P content and biomass in B. napus were also positively regulated.BnaPHT1;4 J has a catalytic effect on seedlings and nutritional growth of B. napus and promotes Pi uptake and translocation. [ABSTRACT FROM AUTHOR]

Aims: Laser micromanipulation such as dissection or optical trapping enables remote physical modification of the activity of tissues, cells and organelles. To date, applications of laser manipulation to plant roots grown in soil have been limited. Here, we show laser manipulation can be applied in situ when plant roots are grown in transparent soil. Methods: We have developed a Q-switched laser manipulation and imaging instrument to perform controlled dissection of roots and to study light-induced root growth responses. We performed a detailed characterisation of the properties of the cutting beams through the soil, studying dissection and optical ablation. Furthermore, we also studied the use of low light doses to control the root elongation rate of lettuce seedlings (Lactuca sativa) in air, agar, gel and transparent soil. Results: We show that whilst soil inhomogeneities affect the thickness and circularity of the beam, those distortions are not inherently limiting. The ability to induce changes in root elongation or complete dissection of microscopic regions of the root is robust to substrate heterogeneity and microscopy set up and is maintained following the limited distortions induced by the transparent soil environment. Conclusions: Our findings show that controlled in situ laser dissection of root tissues is possible with a simple and low-cost optical set-up. We also show that, in the absence of dissection, a reduced laser light power density can provide reversible control of root growth, achieving a precise "point and shoot" method for root manipulation. [ABSTRACT FROM AUTHOR]

Background: Suboptimal water and nutrient availability are primary constraints in global agriculture. Root anatomy plays key roles in soil resource acquisition. In this article we summarize evidence that root anatomical phenotypes present opportunities for crop breeding. Scope: Root anatomical phenotypes influence soil resource acquisition by regulating the metabolic cost of soil exploration, exploitation of the rhizosphere, the penetration of hard soil domains, the axial and radial transport of water, and interactions with soil biota including mycorrhizal fungi, pathogens, insects, and the rhizosphere microbiome. For each of these topics we provide examples of anatomical phenotypes which merit attention as selection targets for crop improvement. Several cross-cutting issues are addressed including the importance of phenotypic plasticity, integrated phenotypes, C sequestration, in silico modeling, and novel methods to phenotype root anatomy including image analysis tools. Conclusions: An array of anatomical phenes have substantial importance for the acquisition of water and nutrients. Substantial phenotypic variation exists in crop germplasm. New tools and methods are making it easier to phenotype root anatomy, determine its genetic control, and understand its utility for plant fitness. Root anatomical phenotypes are underutilized yet attractive breeding targets for the development of the efficient, resilient crops urgently needed in global agriculture. [ABSTRACT FROM AUTHOR]

Background and aims: Rice accumulates higher levels of cadmium (Cd) in grain than other cereals, and hybrid rice varieties cover around half of the total rice area in China. Therefore, understanding the phenotypic and genetic characteristics of Cd accumulation in rice hybrids is vital for food safety. Methods: An incomplete diallel cross design was used to analyse the heritability and combining ability of Cd accumulation in rice hybrids growing in soil contaminated with Cd. The quantitative real-time PCR was used to detect the gene expressions that related to Cd uptake and transport. The Cd contents in brown rice, nodes and roots were detected by ICPOES, and the Cd contents in xylem sap were detected by ICPMS. Results: Additive effects dominated the Cd accumulation in brown rice, upper nodes, and the Cd translocation efficiency from roots to nodes of hybrids. The Cd accumulation in brown rice was positively correlated with Cd accumulation in upper nodes and translocation efficiency from roots to nodes. Regarding the general combining ability, the restorer lines R2292 and R2265, and the male sterile lines KeBX58S, Ke20A, Ke76-1BS and Ke244-1BS were found to be potential elite parental lines for developing hybrid rice with low Cd accumulation. Conclusions: Hybrid rice with low Cd accumulation in brown rice can be derived from parental lines with low general combining ability for Cd content in brown rice. [ABSTRACT FROM AUTHOR]

Aims: The aims of this study were (1) to assess which intercropping system is feasible in enhancing soil moisture and promoting crop root growth and (2) to integrate crop root data to assess which intercropping system can reduce interspecific competition and thus increase system productivity. The optimal cropping system was determined by calculating the land equivalent ratio.In this study, we designed two intercropping systems (intercropped apple–soybean and intercropped apple–alfalfa) and three monocropping systems (monocropped apple, monocropped soybean and monocropped alfalfa) that analysed the effects of these intercropping systems on soil moisture, crop roots, interspecific relationships and yields to determine the most suitable cropping system for local promotion.Within 50–200 cm from the tree, the apple–soybean intercropping and apple–alfalfa intercropping systems increased soil moisture by 27.91% and 30.23%, respectively, compared to apple monocropping. The root system of intercropped apple was mainly distributed in 20–40 cm soil depth, while the root system of intercropped soybean and intercropped alfalfa moved to shallower soil layers, mainly in 0–20 cm soil depth. In addition, within the distance of 100–200 cm from the tree, soybeans were more competitive than apples and apples were more competitive than alfalfa, whereas apples were more competitive than soybeans and alfalfa at 20–60 cm soil depth. The land equivalent ratio for apple–soybean intercropping system was 1.34 and for the apple–alfalfa intercropping system was 1.18. On balance, apple–soybean intercropping system was more suitable for local promotion.These results showed that apple–soybean intercropping system has less interspecific competition than apple–alfalfa intercropping system and that the system is more productive and more suitable for local extension.Methods: The aims of this study were (1) to assess which intercropping system is feasible in enhancing soil moisture and promoting crop root growth and (2) to integrate crop root data to assess which intercropping system can reduce interspecific competition and thus increase system productivity. The optimal cropping system was determined by calculating the land equivalent ratio.In this study, we designed two intercropping systems (intercropped apple–soybean and intercropped apple–alfalfa) and three monocropping systems (monocropped apple, monocropped soybean and monocropped alfalfa) that analysed the effects of these intercropping systems on soil moisture, crop roots, interspecific relationships and yields to determine the most suitable cropping system for local promotion.Within 50–200 cm from the tree, the apple–soybean intercropping and apple–alfalfa intercropping systems increased soil moisture by 27.91% and 30.23%, respectively, compared to apple monocropping. The root system of intercropped apple was mainly distributed in 20–40 cm soil depth, while the root system of intercropped soybean and intercropped alfalfa moved to shallower soil layers, mainly in 0–20 cm soil depth. In addition, within the distance of 100–200 cm from the tree, soybeans were more competitive than apples and apples were more competitive than alfalfa, whereas apples were more competitive than soybeans and alfalfa at 20–60 cm soil depth. The land equivalent ratio for apple–soybean intercropping system was 1.34 and for the apple–alfalfa intercropping system was 1.18. On balance, apple–soybean intercropping system was more suitable for local promotion.These results showed that apple–soybean intercropping system has less interspecific competition than apple–alfalfa intercropping system and that the system is more productive and more suitable for local extension.Results: The aims of this study were (1) to assess which intercropping system is feasible in enhancing soil moisture and promoting crop root growth and (2) to integrate crop root data to assess which intercropping system can reduce interspecific competition and thus increase system productivity. The optimal cropping system was determined by calculating the land equivalent ratio.In this study, we designed two intercropping systems (intercropped apple–soybean and intercropped apple–alfalfa) and three monocropping systems (monocropped apple, monocropped soybean and monocropped alfalfa) that analysed the effects of these intercropping systems on soil moisture, crop roots, interspecific relationships and yields to determine the most suitable cropping system for local promotion.Within 50–200 cm from the tree, the apple–soybean intercropping and apple–alfalfa intercropping systems increased soil moisture by 27.91% and 30.23%, respectively, compared to apple monocropping. The root system of intercropped apple was mainly distributed in 20–40 cm soil depth, while the root system of intercropped soybean and intercropped alfalfa moved to shallower soil layers, mainly in 0–20 cm soil depth. In addition, within the distance of 100–200 cm from the tree, soybeans were more competitive than apples and apples were more competitive than alfalfa, whereas apples were more competitive than soybeans and alfalfa at 20–60 cm soil depth. The land equivalent ratio for apple–soybean intercropping system was 1.34 and for the apple–alfalfa intercropping system was 1.18. On balance, apple–soybean intercropping system was more suitable for local promotion.These results showed that apple–soybean intercropping system has less interspecific competition than apple–alfalfa intercropping system and that the system is more productive and more suitable for local extension.Conclusions: The aims of this study were (1) to assess which intercropping system is feasible in enhancing soil moisture and promoting crop root growth and (2) to integrate crop root data to assess which intercropping system can reduce interspecific competition and thus increase system productivity. The optimal cropping system was determined by calculating the land equivalent ratio.In this study, we designed two intercropping systems (intercropped apple–soybean and intercropped apple–alfalfa) and three monocropping systems (monocropped apple, monocropped soybean and monocropped alfalfa) that analysed the effects of these intercropping systems on soil moisture, crop roots, interspecific relationships and yields to determine the most suitable cropping system for local promotion.Within 50–200 cm from the tree, the apple–soybean intercropping and apple–alfalfa intercropping systems increased soil moisture by 27.91% and 30.23%, respectively, compared to apple monocropping. The root system of intercropped apple was mainly distributed in 20–40 cm soil depth, while the root system of intercropped soybean and intercropped alfalfa moved to shallower soil layers, mainly in 0–20 cm soil depth. In addition, within the distance of 100–200 cm from the tree, soybeans were more competitive than apples and apples were more competitive than alfalfa, whereas apples were more competitive than soybeans and alfalfa at 20–60 cm soil depth. The land equivalent ratio for apple–soybean intercropping system was 1.34 and for the apple–alfalfa intercropping system was 1.18. On balance, apple–soybean intercropping system was more suitable for local promotion.These results showed that apple–soybean intercropping system has less interspecific competition than apple–alfalfa intercropping system and that the system is more productive and more suitable for local extension. [ABSTRACT FROM AUTHOR]

Aims: The aim of this study was to provide a comprehensive understanding of the mechanisms underlying response of rice (Oryza sativa L.) to the endophytic N2-fixing bacterium Burkholderia vietnamiensis strain RS1 in growth and nitrogen (N) accumulation using transcriptome and hormonome analyses. Methods: The effects of B. vietnamiensis RS1 on rice growth and root architecture were examined in pot and field conditions. To identify candidate plant genes that affect the growth of plants inoculated with B. vietnamiensis RS1, transcriptome analysis was conducted. We also examined the hormonal changes by hormonome analysis in relation to the morphological changes in roots. The contribution of N2 fixation by B. vietnamiensis RS1 was estimated by the acetylene reduction activity (ARA). Results: The inoculation of B. vietnamiensis RS1 resulted in increased shoot and root growth of rice plants accompanied by an increased root N absorption rate, especially under high N conditions. The contribution from N2 fixation was minor because no effect of B. vietnamiensis RS1 on ARA was detected. Transcriptome analysis revealed an increase in the expression of genes related to the transportation and assimilation of N compounds, supporting the enhanced N absorption by roots. The expression of indole-3-acetic acid (IAA) signaling genes and concentrations of IAA increased, which may be related to the increased root development. Conclusions: B. vietnamiensis RS1 enhanced rice growth by promoting N accumulation through enhanced root morphological development and N absorption ability; this outcome was probably related to the increased activities of N transportation and assimilation in the presence of a rich N supply. [ABSTRACT FROM AUTHOR]

Aims: Microstructure plays an important role in biological systems. Microstructural features are critical in the interaction between two biological organisms, for example, a microorganism and the surface of a plant. However, isolating the structural effect of the interaction from all other parameters is challenging when working directly with the natural system. Replicating microstructure of leaves was recently shown to be a powerful research tool for studying leaf-environment interaction. However, no such tool exists for roots. Roots present a special challenge because of their delicacy (specifically of root hairs) and their 3D structure. We aim at developing such a tool for roots. Methods: Biomimetics use synthetic systems to mimic the structure of biological systems, enabling the isolation of structural function. Here we present a method which adapts tools from leaf microstructure replication to roots. We introduce new polymers for this replication. Results: We find that Polyurethane methacrylate (PUMA) with fast UV curing gives a reliable replication of the tomato root surface microstructure. We show that our system is compatible with the pathogenic soilborne bacterium Ralstonia solanacearum. Conclusions: This newly developed tool may be used to study the effect of microstructure, isolated from all other effects, on the interaction of roots with their environment. [ABSTRACT FROM AUTHOR]

Aims: Cover crops (CC) have been widely used to improve soil quality and sustain agricultural productivity. However, the turnover of carbon (C) and nitrogen (N) from different species and parts of CCs incorporated into the soil under Northern European conditions remains unclear. Methods: In this study, we examined mineralization of C and N from isolated shoots and roots of two leguminous and two non-leguminous CCs labeled with 15N tracers in a 100-day incubation experiment at 10 °C. Results: After 100 days incubation, the average net N mineralization was 33% from the leguminous CCs and 20% from the non-legumes. Net N mineralization from shoots was 1–15% (% of the N input) higher than that from the corresponding roots, and the net C mineralization accounted for 53–62% and 18–39% of the total C applied with CC shoots and roots, respectively. The C/N ratio of plant residues was a good predictor for net N mineralization, while the lignin concentration was a good predictor for C mineralization from both roots and shoots. Roots of both legume and non-legume CCs caused net immobilization of (unlabeled) soil N, whereas no significant soil N immobilization occurred from shoots with low C/N ratios. Conclusions: Our results indicate that different CC characteristics (C/N ratio and lignin) control the turnover of residue N and C, respectively, in the soil. Our results further showed very limited interactions with soil N turnover (no priming effects) when materials with low C/N ratios were applied to soil. [ABSTRACT FROM AUTHOR]

Background: Suboptimal nitrogen availability is a primary constraint for crop production in low-input agroecosystems, while nitrogen fertilization is a primary contributor to the energy, economic, and environmental costs of crop production in high-input agroecosystems. In this article we consider avenues to develop crops with improved nitrogen capture and reduced requirement for nitrogen fertilizer.Intraspecific variation for an array of root phenotypes has been associated with improved nitrogen capture in cereal crops, including architectural phenotypes that colocalize root foraging with nitrogen availability in the soil; anatomical phenotypes that reduce the metabolic costs of soil exploration, improve penetration of hard soil, and exploit the rhizosphere; subcellular phenotypes that reduce the nitrogen requirement of plant tissue; molecular phenotypes exhibiting optimized nitrate uptake kinetics; and rhizosphere phenotypes that optimize associations with the rhizosphere microbiome. For each of these topics we provide examples of root phenotypes which merit attention as potential selection targets for crop improvement. Several cross-cutting issues are addressed including the importance of soil hydrology and impedance, phenotypic plasticity, integrated phenotypes, in silico modeling, and breeding strategies using high throughput phenotyping for co-optimization of multiple phenes.Substantial phenotypic variation exists in crop germplasm for an array of root phenotypes that improve nitrogen capture. Although this topic merits greater research attention than it currently receives, we have adequate understanding and tools to develop crops with improved nitrogen capture. Root phenotypes are underutilized yet attractive breeding targets for the development of the nitrogen efficient crops urgently needed in global agriculture.Scope: Suboptimal nitrogen availability is a primary constraint for crop production in low-input agroecosystems, while nitrogen fertilization is a primary contributor to the energy, economic, and environmental costs of crop production in high-input agroecosystems. In this article we consider avenues to develop crops with improved nitrogen capture and reduced requirement for nitrogen fertilizer.Intraspecific variation for an array of root phenotypes has been associated with improved nitrogen capture in cereal crops, including architectural phenotypes that colocalize root foraging with nitrogen availability in the soil; anatomical phenotypes that reduce the metabolic costs of soil exploration, improve penetration of hard soil, and exploit the rhizosphere; subcellular phenotypes that reduce the nitrogen requirement of plant tissue; molecular phenotypes exhibiting optimized nitrate uptake kinetics; and rhizosphere phenotypes that optimize associations with the rhizosphere microbiome. For each of these topics we provide examples of root phenotypes which merit attention as potential selection targets for crop improvement. Several cross-cutting issues are addressed including the importance of soil hydrology and impedance, phenotypic plasticity, integrated phenotypes, in silico modeling, and breeding strategies using high throughput phenotyping for co-optimization of multiple phenes.Substantial phenotypic variation exists in crop germplasm for an array of root phenotypes that improve nitrogen capture. Although this topic merits greater research attention than it currently receives, we have adequate understanding and tools to develop crops with improved nitrogen capture. Root phenotypes are underutilized yet attractive breeding targets for the development of the nitrogen efficient crops urgently needed in global agriculture.Conclusions: Suboptimal nitrogen availability is a primary constraint for crop production in low-input agroecosystems, while nitrogen fertilization is a primary contributor to the energy, economic, and environmental costs of crop production in high-input agroecosystems. In this article we consider avenues to develop crops with improved nitrogen capture and reduced requirement for nitrogen fertilizer.Intraspecific variation for an array of root phenotypes has been associated with improved nitrogen capture in cereal crops, including architectural phenotypes that colocalize root foraging with nitrogen availability in the soil; anatomical phenotypes that reduce the metabolic costs of soil exploration, improve penetration of hard soil, and exploit the rhizosphere; subcellular phenotypes that reduce the nitrogen requirement of plant tissue; molecular phenotypes exhibiting optimized nitrate uptake kinetics; and rhizosphere phenotypes that optimize associations with the rhizosphere microbiome. For each of these topics we provide examples of root phenotypes which merit attention as potential selection targets for crop improvement. Several cross-cutting issues are addressed including the importance of soil hydrology and impedance, phenotypic plasticity, integrated phenotypes, in silico modeling, and breeding strategies using high throughput phenotyping for co-optimization of multiple phenes.Substantial phenotypic variation exists in crop germplasm for an array of root phenotypes that improve nitrogen capture. Although this topic merits greater research attention than it currently receives, we have adequate understanding and tools to develop crops with improved nitrogen capture. Root phenotypes are underutilized yet attractive breeding targets for the development of the nitrogen efficient crops urgently needed in global agriculture. [ABSTRACT FROM AUTHOR]

Aims: Roots are vital organs for plants, but the assessment of root traits is difficult, particularly in deep soil layers under natural field conditions. A popular technique to investigate root growth under field or semi-field conditions is the use of minirhizotrons. However, the subsequent manual quantification process is time-consuming and prone to error. Methods: We developed a multispectral minirhizotron imaging system and a subsequent image analysis strategy for automated root detection. Five wavelengths in the visible (VIS) and near-infrared (NIR) spectrum are used to enhance living roots by a multivariate grouping of pixels based on differences in reflectance; background noise is suppressed by a vesselness enhancement filter. The system was tested against manual analysis of grid intersections for both spring barley (Hordeum vulgare L.) and perennial ryegrass (Lolium perenne L.) cultivars at two time-points. The images of living roots were captured in wet subsoil conditions with dead roots present from a previous crop. Results: Under the soil conditions used in the study, NIR reflectance (940 nm), provided limited ability to separate between rhizosphere components, compared to reflectance in the violet and blue light spectrum (405 nm and 450 nm). Multivariate image analysis of the spectral data, combined with vesselness enhancement and thresholding allowed for automated detection of living roots. Automated image analysis largely replicated the root intensity found during manual grid intersect analysis of the same images. Although some misclassification occurred, caused by elongated structures of dew and chalkstone with similar reflectance pattern as living root, the system provided similar or in some cases improved detection of genotypic differences in the total root length within each tube. Conclusion: The multispectral imaging system allows for automated detection of living roots in minirhizotron studies. The system requires considerably less time than traditional manual recording using grid intersections. The flexible training strategy used for root segmentation offers hope for the transfer to other rhizosphere components and other soil types of interest. [ABSTRACT FROM AUTHOR]

Aims: The Yellow and Huai Valleys Winter Wheat Zone (YHVWWZ) is the predominant wheat-producing region in China. This study aimed to identify genetic gains in root characteristics and grain yield of winter wheat (Triticum aestivum L.) cultivars to assist future breeding strategies. Methods: Field trials were conducted in the wetter-than-average 2014–2015 and drier-than-average 2015–2016 growing seasons. Yield and related traits were measured in 17 wheat cultivars released for irrigated conditions in the YHVWWZ from 1948 to 2012. Results: Yields have increased in the 60 years of breeding and selection of cultivars in this region. No change in root biomass with year of release was evident in 2014–2015, but it increased significantly in 2015–2016. The density of shallow roots (0–1 m) increased significantly with year of release in both seasons, while the density of deeper roots (1–2 m) decreased significantly in 2014–2015 and increased significantly in 2015–2016. Aboveground biomass increased with year of release in 2014–2015 but did not change in 2015–2016, and total biomass (root plus shoot) increased with year of release in both seasons. Conclusions: Modern wheat cultivars are better adapted to different watering levels in irrigated areas than older cultivars, with more root biomass at shallow depth, higher plasticity of the root system with depth, and increased yields. [ABSTRACT FROM AUTHOR]

Background and aims: Boron (B) deficiency is one of the major abiotic stresses to citrus. Trifoliate orange, as the most important citrus rootstock in China, is sensitive to B deficiency. B deficiency has serious negative effects on metabolic processes in roots, but whether the hazardous effects can be alleviated to some degree with B resupply remains unclear. The purpose of this study was to investigate the effects of B resupply on metabolites and metabolic pathway in B-starved trifoliate orange [Poncirus trifoliate (L.) Raf.] roots.Methods: Gas chromatography-mass spectrometry (GC-MS) was used to analyze the metabolic profiles in roots under different treatments of B deprivation and B resupply.Results: B deficiency induced an obvious enlargement of root tips and significant alterations in metabolites. Changes were also observed in basic or neutral amino acids, several organic acids and carbohydrates of B-starved roots. However, one week of B resupply quickly reversed the changes in the roots with the initiation of new roots across the inflated root tips, and the restored some of metabolites to a normal level, such as proline (Pro), linoleic acid, 6-deoxy-D-glucose and myo-inositol, indicating that these metabolites are very sensitive to B availability.Conclusions: The data suggest that B resupply may contribute to the obvious, although not full, recovery of the root growth by reversing the central metabolite changes. This study provides a new insight into the relationship between root growth and the alteration on metabolites induced by B deficiency and B resupply, which can be expected to make an important contribution to the scientific application of B fertilizer. [ABSTRACT FROM AUTHOR]

Background and aims: Gene expression analysis under field conditions improves our understanding of crop responses to fluctuating environmental conditions. We evaluated RNA extraction methods and reference genes for a quantitative real-time PCR study of rice roots grown under field conditions.Methods: Roots were collected from paddy (Andosol) at different growth stages, from tillering to ripening. RNA was extracted by three methods using commercially available RNA-extraction kits, and RNA yield and quality were compared.Results: Our RNA extraction method enabled us to obtain adequate concentration and yield of RNA from the roots during a broad period of growth. Adequate RNA concentration was successfully extracted from the field-grown rice roots using large quantities of tissue samples and by purifying the samples prior to the extraction. Among the seven candidate reference genes, TATA-binding protein coding gene (TBP2) was observed to be highly stable across all the root samples and growth stages, in real-time PCR assays. Root gene expression analysis of water channel- and nitrogen uptake-related proteins clearly indicated dynamic changes (with respect to diurnal and growth stages) in their expression levels and their associations with meteorological factors. Some aquaporin genes such as OsPIP1;3, OsPIP2;4, and OsPIP2;5, showed clear diurnal changes. Among them, the expression pattern of OsPIP2;5 paralleled the potential evaporation (Ep) and leaf stomatal conductance on a sunny day. The gene expression analysis clearly showed diverse expression patterns; the gene expression levels of many aquaporins decreased after panicle formation stage, whereas the abundance of some genes such as OsNIP2;1 and OsAMT1;3 increased at the later growth stage.Conclusion: Our method will be useful for evaluating the variations of gene expression in the roots of field-grown rice under fluctuating environmental condition. [ABSTRACT FROM AUTHOR]

Aim: Potato cultivars vary in biomass production and Cd concentration. Differences in growth can lead to differences in tuber cadmium (Cd) concentration through growth dilution and/or limited uptake of Cd from the soil. The aims of this study were to investigate the relative importance of shoot (above ground plant parts) and root in dry weight (DW) accumulation, total Cd uptake and Cd distribution between organs and how this affects tuber Cd concentration.Materials and methods: Three experiments were carried out, two with reciprocal grafting between high and low tuber Cd accumulating cultivars under two soil Cd conditions, and the other was involving the evaluation of F1 genotypes, from a cross between these high and low tuber Cd accumulating cultivars. These experiments were carried out under controlled greenhouse conditions.Results: The results showed that the root system is important for total Cd uptake but less important for growth and Cd distribution between organs. On the other hand, the shoot system is important for regulating growth of shoot and roots, and for determining Cd distribution between organs.Conclusion: The data suggest that tuber Cd concentration was mainly regulated by shoot source and to a lesser extent by total uptake of Cd. [ABSTRACT FROM AUTHOR]

Background and aims: In temperate conifer forests, soil temperature is an important driver of fine root growth and winter root growth can occur during aerial dormancy. We hypothesize that in conifers, stocks of non-structural carbohydrates (NSC) in fine roots are high enough to provide energy for root growth and production throughout the year, even when photosynthesis is reduced.Methods: We measured monthly root production (i.e. the number of roots undergoing elongation) and their elongation rate (RER) in mature Picea abies for one year, along a soil temperature gradient (three altitudes of 1400, 1700 and 2000 m). Every two months we harvested needles, branches, stem, large, medium and fine roots, and quantified starch and soluble sugars in each organ using analytical methods and near infra-red spectroscopy (NIRS). Soil water potential was monitored continuously. We analysed RER data with regard to climate variables and NSC levels of the current and preceding month.Results: NIRS was a reliable method for measuring starch and soluble sugars. NSC was high in the crown and roots but very low in the trunk all year round. Soil temperature was positively correlated to RER (of the current month) between 0 and 8 °C, above which RER stabilised and was not explained by NSC levels or soil water potential. However, mean RER of fine roots in the month following the measurement of NSC was significantly and negatively correlated to soluble sugar and positively correlated with starch content. Very fine root starch content was also positively correlated with root production in the month following the starch measurement.Conclusion: Soil temperature was a major driver of fine root elongation, but at low temperatures only. At soil temperatures >8 °C, no particular driver was dominant. NSC levels were negligible in the stem and root-bases, suggesting that wood production is a major sink that depletes carbohydrates. A large pool of NSC, principally in the form of starch, existed in fine roots of P. abies, and acted as an energy supply for root production throughout the year, even when photosynthesis was limited. Soluble sugars were depleted in fine roots during the growing season, but no relationship was found between fine root production and soluble sugars. The physiological mechanism by which NSC accumulation actively or passively occurs in fine roots is not known but could be due to the symplastic pathway of phloem unloading in conifer root tips, which suggests a passive mechanism. [ABSTRACT FROM AUTHOR]

Aims: Arabidopsis thaliana is the model plant that is mainly used in studying cellulose and hemicellulose (CH) biosynthesis. Unfortunately, A. thaliana does not associate with mycorrhiza and as a result there are only rare reports on the role of arbuscular mycorrhiza (AM) fungi on CH biosynthesis. This study aims to investigate the effects of AM fungi on changing the CH content in mycorrhizal plant.Methods: Three AM fungi, Glomus aggregatum, Rhizophagus intraradices and Funneliformis mosseae, were inoculated to vetiver grass (Chrysopogon zizanioides) and grown for 12 months. Roots were harvested, and the proportions of CH, lignin, lipids and hydrosoluble content were analysed. The corresponding root tensile strength (positively correlated with the proportion of CH) was measured to counter check the CH content.Results: Plants inoculated with AM showed a higher proportion of CH (P < 0.05) compared with uninoculated ones. This increase was coupled to a 40-60% enhancement in tensile strength. Potential mechanisms for this phenomenon are discussed.Conclusions: This is the first study showing that the proportion of CH and tensile strength of plant root could be significantly affected by AM symbiosis. It is thus desirable that future research on CH biosynthesis uses mycorrhizal-associating plants, such as medic (Medicago truncatula) and rice (Oryza sativa). [ABSTRACT FROM AUTHOR]

Background: Root phenes play a primary role in plant adaptation to edaphic stress. Understanding the functional implications of root phenotypes will enable the development of crop varieties with improved soil resource acquisition. Root cortical senescence (RCS) is a type of programmed cell death in cortical cells of several Poaceae species. Until recently there has been very little attention to the functional implications of RCS for water and nutrient capture.Scope: We explore the functional implications of RCS as an adaptive trait for water and nutrient acquisition. The present review summarizes evidence from our own studies and other published work, and provides novel insights into the fitness landscape of RCS. Progress has recently been achieved in understanding the development and physiological implications of RCS. We propose that RCS is a useful trait for water and nutrient acquisition, particularly in edaphic stress conditions.Conclusions: Further research is needed to understand the utility and tradeoffs of RCS in the context of specific environments, management practices, and phenotypic backgrounds. The utility of RCS for improved plant performance under edaphic stress merits investigation in the field. RCS may be a useful breeding target for improved soil resource capture in several major crop species including wheat, barley, and triticale. [ABSTRACT FROM AUTHOR]

Aims: Fusarium oxysporum is a causal disease that threatens watermelon production, but little information on the molecular mechanisms involved in host defense is available. To understand the defense response, a proteome-level changes that occur in watermelon roots during F. oxysporum infection were investigated.Methods: We utilized two-dimensional gel electrophoresis (2-DE) to compare changes in the root proteome profiles and validated their expression using real-time PCR.Results: A total of 690 spots were detected, and 32 proteins had significant changes in abundance and were further identified by mass spectrometry. These proteins were mainly involved in metabolism, stress and defense and amino acid biosynthesis. RT-PCR analysis revealed that transcripts corresponding to the nine randomly selected proteins could be significantly induced, their expression patterns were consistent with the proteomic results except for Apx and Tdh. The involvement of these proteins in regulating watermelon response against F. oxysporum is discussed.Conclusions: The reprogrammed proteins were involved in several biological processes, which indicates that watermelon can directly alter the abundance of these proteins to establish a defense response. This work helps us understand the basic processes during the watermelon-F. oxysporum interaction and may contribute to improve resistance breeding toward this pathogen. [ABSTRACT FROM AUTHOR]

Background and Aims: Abiotic stress conditions cause extensive losses to agricultural production worldwide. Salinity and alkalinity affect plant growth, photosynthesis and availability of nutrients including Fe. Many studies have described the response mechanisms of plants to single abiotic stress conditions. However, in the field, crops and other plants are routinely subjected to a combination of different abiotic stresses. Salinity and alkalinity are wide-spread in Tunisia, where Medicago truncatula occurs as a native species. Methods: We established a growth system to study the combined effects of salinity and alkalinity conditions in laboratory conditions. We screened 11 Tunisian M. truncatula lines from the SARDI collection based on their phenotypic responses to the double stress. Results: Salinity and alkalinity affected germination rates, shoot and root dry weights, pigment contents and root morphology parameters. We were able to select among the 11 investigated lines four sensitive and tolerant lines with different abilities to respond to the double stress. Tolerant and sensitive genotypes (two lines each) differed in root flavin contents, root flavin staining patterns and concentrations of root flavins in the nutrient solution. Conclusions: Root architecture, flavin root localization in epidermal cells and flavin secretion are relevant tolerance mechanisms for salt and alkaline stress in M. truncatula. Pairs of contrasting lines from close origins were identified that will be useful tools to identify genes for the tolerance mechanisms. [ABSTRACT FROM AUTHOR]

Background and aims: Tetrastigma hemsleyanum is a rare medicinal plant in China. Because it requires very strict environmental conditions to grow, it usually takes 3-5 years to form calabash-shaped roots and is difficult to meet the demand of Chinese medical market. Although it is known that endophytes can enhance the growth of the host plants, the molecular mechanism of the interplay between endophytes and their host plants growth is not completely understood yet. The aim of this study was to determine if endophytes can reduce the growth cycle and promote the medicinal ingredients in Tetrastigma hemsleyanum, and elucidate its underlying molecular mechanism. Methods: Endophytic fungi were isolated and identified from the calabash-shaped root of Tetrastigma hemsleyanum. The fermentation broth of 6 endophyte strains (named as TH09, TH12, TH14, TH15, TH17 and TH26) were added to the MS medium to culture axenic plantlets. After 30 days of culture, the net growth, expansin gene expression and the flavonoid content were measured. Results: From the calabash-shaped roots, we isolated 31 endophytic fungi belonging to 10 genera: Fusarium, Rhizopycnis, Colletotrichum, Cylindrocarpon, Emericellopsi, Penicillium, Plectosphaerella, Aspergillus tubingensis, Alternaria and Sarocladium, of which Fusarium is the dominant genus. Addition of the fermentation broth from strains TH12, TH15 and TH26 significantly increased the plant growth. Strains TH15 and TH26's fermentation broth increased the expression of Th-exp (an expansin gene), while addition of the fermentation broth from TH14 increased Th-exp expression in leaves and stems, but decreased Th-exp expression in the root. Flavonoid content was increased in the presence of fermentation broth from strains TH09, TH14, TH17 and TH26. Particularly, the fermentation broth from TH26 can promote plant growth, enhance Th-exp expression and increase the flavonoid content in Tetrastigma hemsleyanum. Conclusions: The results demonstrated that endophytic fungi from the calabash-shaped root of Tetrastigma hemsleyanum can regulate plant growth, expression of expansin gene and flavonoid content. [ABSTRACT FROM AUTHOR]

Aims: Our aim was to examine how soil type and precipitation affect fine-root abundance in savanna ecosystems across Kruger National Park (KNP), South Africa. Methods: Fine-root distributions were measured in four sites that represent the natural factorial combination of soil types (basalt-derived clay or granite-derived sand) and precipitation regimes [wet (~750 mm mean annual precipitation) or dry (~500 mm mean annual precipitation)] that occur in KNP. Root area and biomass (at soil depths of 0-75 cm) were estimated from measurements of root number, length and width in images from minirhizotron tubes at each site. Measurements were made during one mid-season sampling during three subsequent years. Results: Fine-root area was more than twice as large in clay (2.3 ± 0.0 mm cm) than sand (0.8 ± 0.3 mm cm) sites but did not differ between wet and dry sites. Root number, length and width, used to derive area, showed similar patterns to fine-root area. Fine-root biomass estimated from these values was 5.5 ± 0.6 Mg ha in clay sites and 2.2 ± 0.9 Mg ha in sand sites. Conclusions: Across the four sites, a change from sand to clay soils had a greater effect on fine-root abundance and distributions than a 50% increase in precipitation from dry to wet sites. Results highlight the importance of soil properties on root dynamics and carbon pools in the region. [ABSTRACT FROM AUTHOR]

Background & aims: Some metabolites (e.g. amino acids) present in root exudates can be taken up by roots, but we do not know if this ability extends to the broader suite of metabolites found in exudates. The aim of this study was to examine the ability of wheat ( Triticum aestivum L.) to efflux and take up a broad suite of small metabolites. Methods: Four-week-old plants were placed into an uptake solution that contained a broad suite of C-labelled metabolites. Uptake was estimated from the decrease in concentration of the C isotopologue in the solution; and from the appearance of C isotopologues within roots. Efflux was estimated from appearance of C isotopologues in solution. Results: When wheat plants were placed in C-metabolite solutions the concentration of U-C isotopologues of 37 metabolites decreased - as would be expected if plants were taking up the U-C metabolites. After 4 h immersion in C metabolite solution, roots contained detectable amounts of U-C isotopologues of 55 metabolites. U-C isotopologues of organic acids were not detected within roots. Conclusions: These findings indicate that wheat can take up a broad suite of N-containing metabolites and some sugars, but there was no evidence for uptake of organic acids. [ABSTRACT FROM AUTHOR]

Background and aims To assess the impacts of soil microbes and plant genotype on the composition of maize associated bacterial communities. Methods Two genotypes of Brazilian maize were planted indoors on sterile sand, a deep underground subsoil, and a nutrient-rich topsoil from the Amazon jungle (terra preta). DNA was extracted from rhizospheres, phyllospheres, and surface sterilized roots for 16S rDNA fingerprinting and next generation sequencing. Results Neither plant genotype nor soil type appeared to influence bacterial diversity in phyllospheres or endospheres. Rhizospheres showed strikingly similar 16S rDNA ordination of both fingerprinting and sequencing data, with soil type driving grouping patterns and genotype having a significant impact only on sterile sand. Rhizospheres grown in non-sterile soils contained greater bacterial diversity than sterile-sand grown ones, however the dominant OTUs (species of Proteobacteria and Bacteroidetes) were found in all rhizospheres suggesting seeds as a common source of inoculum. Rhizospheres of the commercial hybrid appeared to contain less bacterial diversity than the landrace. Conclusions Maize rhizospheres receive diverse bacteria from soil, are influenced by the genotype or treatment of the seed, and are dominated by species of Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes. As many dominant 16S rDNA sequences were observed in rhizospheres grown in both sterile and non-sterile substrate, we conclude that the most common bacterial cells in juvenile maize rhizospheres are seed transmitted. [ABSTRACT FROM AUTHOR]

Background and aims: Pyrogenic biochar materials are being considered as a soil amendment in multiple contexts around the world. However, there is limited knowledge about the interaction of biochar with root and nodule development in legumes. Methods: A greenhouse study was conducted to evaluate the effect of biochars of differing sources on two Medicago truncatula (clover) genotypes ' wild' ( w) and ' sickle' ( skl) (an ethylene insensitive mutant). Biochars of two biomass feedstocks (corn stover and switchgrass) and two pyrolytic processes (slow and fast pyrolysis) were used to evaluate the two genotypes for plant growth, root nodulation, and root morphology. Results: Biochar treatments at a 1 % (10 g kg soil) application rate increased nodule formation and plant biomass across all genotypes. Corn stover fast pyrolysis biochar induced a higher degree of nodulation. Fast pyrolysis process biochars resulted in greater shoot dry weight for both genotypes compared to control. Shoot dry weight was less in plants treated with corn stover slow pyrolysis biochar compared to other biochars. Biochar stimulated nodule formation in both w and skl genotypes compared to controls. Biochar increased root length of higher and lower order lateral roots (0-1 mm and 1-2 mm diameter). There was a significant genotype x biochar treatment interaction for root length in the 1-2 mm diameter root class. Conclusions: Overall a positive effect of biochar was observed on plant growth, root nodulation, and root morphology of two Medicago truncatula genotypes. Biochars of different biomass feedstock and pyrolytic processes resulted in differences in root morphology and plant growth. The increase in nodule numbers resulting from biochar additions appears to be independent of the mechanism causing the increase in nodule numbers in the skl mutant. Differences in genotype response to biochar highlight the need to consider plant genetic composition as well as biochar type when evaluating potential for crop response to biochar soil amendments. [ABSTRACT FROM AUTHOR]

Background & aims: Small organic N compounds could contribute to N nutrition, but an alternative view is that root uptake may serve to recapture compounds that efflux out of roots. However, it is unclear if plants can recapture leaked organic N compounds because no studies have examined quantitative relationships between efflux and uptake at sub-micromolar concentrations. Methods: This study examines efflux and uptake of a broad suite of small organic N compounds by wheat ( Triticum aestivum L.). N-labeling and capillary electrophoresis-mass spectrometry were used to estimate efflux and uptake. Results: One hundred and ten organic N compounds were detected in exudates. Amino acids were abundant but accounted for less than half of organic N. Other abundant compound classes were amines and polyamines, quaternary ammonium compounds, nucleobases and nucleosides. Uptake occurred simultaneously with efflux for all 45 compounds for which rates of efflux could be reliably determined, even though concentrations were 0.01 to 0.5 μM. Conclusions: These findings indicate that wheat is highly proficient at recapturing much of the diverse array of organic N compounds in root exudates. The ability to salvage effluxed compounds present at very low concentrations means that wheat might also be able to take up organic N compounds from the soil solution. [ABSTRACT FROM AUTHOR]

Background and aims: Copper is one of the most important pollutants in mine-contaminated soils. This study tests the response in a sensitive population vs a tolerant one of the model species Silene paradoxa in order to understand the general mechanisms of tolerance at the micromorphological and ultrastructural level. Methods: Two populations of Silene paradoxa were grown in hydroponics and exposed to different CuSO treatments. The roots were investigated with light, fluorescence and transmission electron microscope. Callose and lignin were spectrophotometrically determined. Results: The tolerant population constitutively possessed a higher amount of mucilage and was able to reduce the length of the zone between the apex and the first lignified tracheids. Callose production decreased. It did not show remarkable copper-induced ultrastructural modifications, apart from the presence of precipitates in the tangential walls. The sensitive population showed huge nucleoli with a spongy periphery in the central cylinder together with the presence of electrondense granules in the mitochondria. Plastids were rarely observed and generally very electrondense and elongated. Conclusions: n the copper tolerant population of S. paradoxa some of the root traits concurring to generate metal-excluding roots were suggested to be mucilage and lignin production and the reduction of the subapical root zone. [ABSTRACT FROM AUTHOR]

Background and aims: Our objective was to relate chemical composition of roots of a wide range of annual crops to root decomposition, so as to assess roots potential contribution to soil carbon (C). Methods: Roots from 20 different crops and 4 botanical families, collected under field conditions were incubated in soil for 120 days at 25 °C. The initial chemical composition of roots was determined. The C mineralization was assessed by the continuous measurement of CO release and using single exponential model. PCA analysis was used to explore qualitative pattern in root quality and decomposition. Results: PCA analysis showed that chemical characteristics (traits) differentiated plant families. The mineralization of root C varied greatly in terms of kinetics and in the total amount of C mineralized (36 % to 59 % of added C). Mineralization constant ( k value) was negatively correlated with hemicelluloses and positively with N content. Poaceae roots that combined high hemicelluloses, low cellulose and low total N, showed low degradation rate and cumulative C mineralization. Conclusions: The chemical composition of roots, as for the above-ground parts of plants, can correctly predict their rate of decomposition in soils. The taxonomic affiliation enhances the understanding of the chemical determinants of quality of roots. [ABSTRACT FROM AUTHOR]

Aims: Potatoes are a globally important source of food whose production requires large inputs of fertiliser and water. Recent research has highlighted the importance of the root system in acquiring resources. Here measurements, previously generated by field phenotyping, tested the effect of root size on maintenance of yield under drought (drought tolerance). Methods: Twelve potato genotypes, including genotypes with extremes of root size, were grown to maturity in the field under a rain shelter and either irrigated or subjected to drought. Soil moisture, canopy growth, carbon isotope discrimination and final yields were measured. Destructively harvested field phenotype data were used as explanatory variables in a general linear model (GLM) to investigate yield under conditions of drought or irrigation. Results: Drought severely affected the small rooted genotype Pentland Dell but not the large rooted genotype Cara. More plantlets, longer and more numerous stolons and stolon roots were associated with drought tolerance. Previously measured carbon isotope discrimination did not correlate with the effect of drought. Conclusions: These data suggest that in-field phenotyping can be used to identify useful characteristics when known genotypes are subjected to an environmental stress. Stolon root traits were associated with drought tolerance in potato and could be used to select genotypes with resilience to drought. [ABSTRACT FROM AUTHOR]

Background and aims: Root elongation is essential in the determination of the root system architecture (RSA). Using experimental data, we show how it varies in the RSA and suggest a new and simple modeling approach to predict these variations. Methods: We analyzed variation in elongation on data from pot-grown plants belonging to two different species ( Helianthus annuus L. and Noccaea caerulescens (J.Presl & C.Presl) F.K.Mey). A stochastic model was designed with two successive steps to quantify and simulate these variations. The first step is the definition of a growth potential, reflected by the apical diameter, and depending on the size of the mother root. The second step, during elongation, describes the dynamic evolution of the meristem and its interaction with soil constraints. Results: The species exhibited differences in their structured variations and very large residual (pseudo-random) variability in elongation rate and final length. The two-step model allowed us to summarize these species characteristics, and to show the interest of considering the stochastic aspects of root growth to correctly simulate the RSA. Conclusions: Apart from being a more realistic way of simulating root development, this type of model raises new questions regarding the representation of root soil interactions during elongation. [ABSTRACT FROM AUTHOR]

Background and aims: The concept of root-sourced chemical signals that affect shoot growth in response to drought is widely reported; in particular the role of ABA in regulating stomatal conductance has received much attention. ABA, alone, does not fully explain all the effects of abiotic stresses in the root zone on shoot architecture. An increase in mechanical impedance, which can occur on even relatively modest soil drying, results in reduced root and shoot growth, processes that are potentially regulated by gibberellins (GAs ). Methods: In this study we explored the role of mechanical impedance and exogenous gibberellin (GA) on root and shoot architecture in wheat seedlings containing the Rht-B1a (tall), Rht-B1b (semi-dwarf) or Rht-B1c (dwarf) alleles in the April-Bearded or Mercia backgrounds. Our experiments were based on the use of the sand culture system which allows the mechanical impedance of the root growth environment to remain constant and independent of water and nutrient availability. We investigated the effects of the application of exogenous GA to the root system. Results: We found that impeding soil reduced leaf elongation in the tall and semi-dwarf lines, confirming the stunting effect of mechanical impedance which is widely reported. However, leaf elongation in the dwarf lines was not affected by root impedance. Application of GA to the roots restored leaf elongation in the tall and semi-dwarf lines growing in impeding soil, with some growth response even in the dwarf line, the longest leaves being obtained when GA was applied to impeded roots of a tall line. Both exogenous GA and root impedance reduced the number of tillers, but there was no interaction with the Rht genotype. The genetic background did not affect the results. Conclusion: We suggest that the GA signalling pathway has an unidentified role in the leaf elongation response to mechanical impedance to root growth. [ABSTRACT FROM AUTHOR]

Aims: Potatoes have an inadequate rooting system for efficient acquisition of water and minerals and use disproportionate amounts of irrigation and fertilizer. This research determines whether significant variation in rooting characteristics of potato exists, which characters correlate with final yield and whether a simple screen for rooting traits could be developed. Methods: Twenty-eight genotypes of Solanum tuberosum groups Tuberosum and Phureja were grown in the field; eight replicate blocks to final harvest, while entire root systems were excavated from four blocks. Root classes were categorised and measured. The same measurements were made on these genotypes in the glasshouse, 2 weeks post emergence. Results: In the field, total root length varied from 40 m to 112 m per plant. Final yield was correlated negatively with basal root specific root length and weakly but positively with total root weight. Solanum tuberosum group Phureja genotypes had more numerous roots and proportionally more basal than stolon roots compared with Solanum tuberosum, group Tuberosum genotypes. There were significant correlations between glasshouse and field measurements. Conclusions: Our data demonstrate that variability in rooting traits amongst commercially available potato genotypes exists and a robust glasshouse screen has been developed. By measuring potato roots as described in this study, it is now possible to assess rooting traits of large populations of potato genotypes. [ABSTRACT FROM AUTHOR]

Backgrounds and aims: Tea plants ( Camellia sinensis (L.) O. Kuntze) accumulate high fluoride in the leaves whereas the mechanism on its uptake is poorly understood. The measured F uptake was compared to calculated uptake from transpiration rates assumuing no discrimination between F and water to characterize the property of F absorption by tea plant roots. Methods: The F uptake was examined by depletion method under variable external F concentrations, pH, temperature, relative air humidity, anion channel blockers and metabolism inhibitors in solution experiments. Results: Measured F uptake rates were significantly larger than those calculated from transpiration rates regardless of external F concentrations, uptake durations, relative humidity, and solution pH. The measured and net F uptake (subtracting that calculated from transpiration rate from the measured uptake) were reduced by low temperature and inhibited by anion channel and metabolism inhibitors anthracene-9-carboxylic acid (A-9-C), niflumic acid (NFA), and carbonylcyanide m-chlorophenylhydrazone (CCCP) but not by dihydro-4, 4′ diisothiocyanostilbene-2, 2′-disulphonic acid (DIDS). The F uptake showed biphasic response patterns, following saturable Michaelis-Menten kinetics in the range of low external F (below 100 μmol L) while increased linearly with external supply in the range of high concentrations. Conclusion: The uptake of F by roots of accumulator tea plants was likely an active process and energy-dependent. This helps to explain why tea plants are able to accumulate considerably high F. [ABSTRACT FROM AUTHOR]

Background and aims: Interacting effects of atmospheric N deposition on the degree to which tree demand for other nutrients is met by soil supply has seldom been explored in Mediterranean-type ecosystems. We hypothesized that patterns for the relative availability of N and P in soils will be matched by variations in process rates related to soil organic P cycling and by shifts from N to P limitation of tree growth. Methods: We examined N/P relationships in Mediterranean-fir ( Abies pinsapo) forests from two nearby regions differing in N deposition levels. Results: N pools and transformation rates and the contribution of organic fractions to the labile P pool in soils showed increasing trends toward the pollution source. Phosphomonoesterase activity (PME) in bulk soils, root PME per unit biomass (but not per unit soil volume) and biomass accumulation in P-fertilized root-in-growth cores incubated in situ were also the highest at the sites receiving elevated N deposition, indicating P limitation. In contrast, forest stands in the region farther from the pollutant source were N-limited (preferential root growth in N-rich soil microsites) and showed lower PME activities and higher total fine root biomass. Conclusions: In the forests under elevated N deposition, higher values for an overall indicator of soil N status matched with indications of an accelerated soil organic P subcycle and P-limitation of tree growth. [ABSTRACT FROM AUTHOR]

Aims: A causal relationship between salinity and oxidative stress tolerance and a suitability of using root antioxidant activity as a biochemical marker for salinity tolerance in barley was investigated. Methods: Net ion fluxes were measured from the mature zone of excised roots of two barley varieties contrasting in their salinity tolerance using non-invasive MIFE technique in response to acute and prolonged salinity treatment. These changes were correlated with activity of major antioxidant enzymes; ascorbate peroxidase, catalase, and superoxide dismutase. Results: It was found that genotypic difference in salinity tolerance was largely independent of root integrity, and observed not only for short-term but also long-term NaCl exposures. Higher K retention ability (and, hence, salinity tolerance) positively correlated with oxidative stress tolerance. At the same time, antioxidant activities were constitutively higher in a sensitive but not tolerant variety, and no correlation was found between SOD activity and salinity tolerance index during large-scale screening. Conclusion: Although salinity tolerance in barley correlates with its oxidative stress tolerance, higher antioxidant activity at one particular time does not correlate with salinity tolerance and, as such, cannot be used as a biochemical marker in barley screening programs. [ABSTRACT FROM AUTHOR]

Background and aims: Climate warming has the potential to increase both the exposure and vulnerability of grass roots to frost in temperate regions by reducing snow cover and altering the timing of cold acclimation. Despite a strong research focus on the direct effects of freezing on grass mortality, the direct sub-lethal effects of freezing on grass performance have not been well-characterized. We examined sub-lethal responses of the grass Poa pratensis to variation in the timing, severity, rate and length of freezing. Methods: We assessed short term root functional responses (N uptake) and longer term plant growth responses to freezing administered both under controlled conditions in a refrigerated incubator, and in the field by manipulating snow and litter cover. Results: In fall and spring, N uptake declined in response to 1 day of freezing down to −10 °C or to 3 days of freezing at −5 °C, whereas in winter, N uptake was insensitive to freezing. Long term growth responses were similar, with reduced growth only occurring for grasses frozen for 3 days at −5 °C in spring, but not for grasses frozen in fall or winter. Snow and litter removal intensified soil freezing over winter, but did not significantly affect plant growth. Conclusions: Our results demonstrate that while P. pratensis is relatively tolerant to frost damage over winter, it may be vulnerable to sub-lethal frost effects in fall, and particularly in spring. These sub-lethal effects occur at temperatures approximately 15-20 °C warmer than the published LT values for this species. [ABSTRACT FROM AUTHOR]

Background and aims: RootScan is a program for semi-automated image analysis of anatomical traits in root cross-sections. Methods: RootScan uses pixel thresholds to separate the cross-section from its background and to divide it into tissue regions. Area measurements and object counts are performed within various regions of interest. A graphical user interface permits the user to see which regions are selected, to edit those selections, and to rate and comment on the data. The structure of the program allows for organized workflow and increased data collection efficiency. Results: The program collects data on more than 20 variables per image including areas of the cross-section, stele, cortex, aerenchyma lacunae, xylem vessels, and counts of cortical cells and cell files. An increased rate of data collection allows collection of four times more variables in less time than is possible with current methods. Correlation analysis shows that RootScan data is equal or greater in accuracy than data collected with Photoshop. Conclusions: Compared with currently available tools, this software offers considerable improvements in the amount and quality of data, ease of use, and time needed for data collection. RootScan permits phenotypic scoring of physiologically and agronomically important traits on a large number of genotypes. [ABSTRACT FROM AUTHOR]

Understanding soil chemical properties is necessary to characterize the basic properties of ecosystems. In mangrove ecosystems, soil iron, phosphorus, methane and nitrogen have been well studied under field conditions. However, it is difficult to understand fundamental relationships between mangrove root functions and soil chemical properties, because of the multiple factors present in field data. The aim of this study was to clarify what will happen to soil chemical properties after mangrove plant colonize. To examine the effect of mangrove roots on these soil properties, three representative mangrove species ( Avicennia marina, Rhizophora stylosa and Bruguiera gymnorrhiza) were cultivated in a greenhouse and selected soil chemical properties were monitored in comparison with those in unplanted soil. We detected oxidative effects in all three species, including deposition of iron oxide on root surfaces, lowered methane concentrations and increased oxidized inorganic nitrogen concentrations in the soil pore-water, suggesting that radial oxygen loss from mangrove roots had affected these soil chemical properties. Besides the oxidative effects, enhanced Fe concentrations in the soil pore-water were present in A. marina, and enhanced phosphorus concentrations in the soil pore-water were present in all three species, suggesting that mangrove roots provide Fe- and phosphate-solubilizing substrates. The most remarkable change was in soil nitrogen enrichment. During the experimental period, amounts of nitrogen in the mangrove soils increased four times more than in uncolonized soil. Six months from the start of cultivation, bacterial nitrogen fixation (nitrogenase activity) was significantly higher in soil colonized by mangrove plants than in uncolonized soil, suggesting that mangrove roots stimulated bacterial nitrogen fixation. Among these properties, Phosphate mobilization and soil nitrogen enrichment are likely to be particularly important for the growth of mangrove plants, because phosphate and nitrogen are generally limited in mangrove ecosystems. This self-supporting ability of mangroves observed in this study could be one key to the high productivity of mangrove ecosystems. [ABSTRACT FROM AUTHOR]

When roots abstract water thus drying the soil, crop growth may be reduced by increasing strength of soil as well as the lack of water. Strong soil impedes root growth, restricting access to deeper water. As a result, there is a need to estimate soil strength in order to model crop response to dry soil correctly. The strength of soil can be routinely assessed with a penetrometer but measurements are time consuming and hard work to acquire at the frequency required to understand soil-water-plant relations. To make progress, a published relationship that derives penetrometer pressure from both water relations in soil and density was improved to take account of the effects of depth including the friction that results from the increasing hydrostatic pressure. These relationships were then incorporated into an agroecosystem model so that the dynamics of strong soil and its effect on wheat could be simulated. The combined model requires the moisture release curve (but this can be derived from other commonly-measured soil properties), daily rainfall, temperature, and potential evaporation and the agronomy of the crop. Modelled values of penetrometer pressure were simulated well compared with measured values in artificially strengthened (compacted) and weakened (irrigated) soils. Simulations of the strength of soil and the matric potential before anthesis are compared with measured total dry-matter yields of winter wheat in experimental fields. The results lend weight to the hypothesis that wheat yield is limited by the strength of soil in the field and that soil strength, rather than soil matric potential, better explains differences between soils. [ABSTRACT FROM AUTHOR]

Root radius frequency distributions have been measured to quantify the effect of plant type, environment and methodology on root systems, however, to date the results of such studies have not been synthesised. We propose that cumulative frequency distribution functions can be used as a metric to describe root systems because (1) statistical properties of the frequency distribution can be determined, (2) the parameters for these can be used as a means of comparison, and (3) the analytical expressions can be easily incorporated into models that are dependent upon root geometry. We collated a database of 96 root radii frequency distributions and botanical and methodology traits for each distribution. To determine if there was a frequency distribution function that was best suited to root radii measurements we fitted the exponential, Rayleigh, normal, log-normal, logistic and Weibull cumulative distribution functions to each distribution in our database. We found that the log-normal function provided the best fit to these distributions and that none of the distribution functions was better or worse suited to particular shapes. We derived analytical expressions for root surface and volume and found that they are a valid, and simpler method for incorporating root architectural traits into analytical models. We also found that growth habit and growth media had a significant effect on mean root radius. [ABSTRACT FROM AUTHOR]

Root respiration consumes an important part of the daily assimilated carbon but the magnitude of this component of forest net ecosystem exchange and its partitioning among the different energy demanding processes in roots are still poorly documented. 5-month old Eucalyptus cuttings were grown in a greenhouse in pot filled with coarse sand. They were fertilized with three different amounts of a slow-release fertilizer with the doses of 8, 24 and 48 g of nitrogen per plant. Root respiration was measured using an infrared gas analyser by perfusing air through the pot on 9 plants per treatment on three dates 14 days apart. Measure of root respiration of the three treatments over time was made in order to obtain a large range of growth and nutrient uptake. Root respiration normalized at 22°C ranged from 0.09 to 0.23 gC d−1 for the three treatments during all the experiment. It was well predicted with a model that includes root growth rate and root nitrogen content.The nitrogen related maintenance coefficient was negatively correlated to the root nitrogen concentration suggesting a decrease in protein turnover with increasing fertility. Growth rate of fine root in a virtual stand was simulated using age-related allometric equations and further used to estimate root respiration in the field. Simulated root respiration increased over time from 0.39 to 3.14 gC m−2 d−1 between 6 and 126 months assuming a turnover of 2 yr−1 for fine roots. The major fraction of simulated root respiration in the field (78–92%) was used for the maintenance of the existing biomass. [ABSTRACT FROM AUTHOR]

Study of roots and associated organisms in soil particularly in mixed plant populations, such as pastures, is limited by difficulties in quantification of root growth and function. The research evaluated the potential of DNA quantification by real-time PCR to improve our capacity to study and understand roots in such contexts. Probes and primers were developed for two common pasture species, Trifolium subterraneum and Lolium perenne (and closely related Lolium spp.), and evaluated for specificity and sensitivity in TaqMan assays on DNA extracted from soil. Further experiments examined the ability to detect DNA in dead roots, the changes in root DNA levels of plants defoliated or treated with herbicide and the relationship between DNA and root dry weight for single and mixed plant species grown in pots. T. subterraneum DNA/PCR 200 fg/µl was detected at 17.5 cycles and L. perenne at 19.5 cycles. The assay for T. subterraneum was species specific but the L. perenne assay, as anticipated from the choice of probe, also detected some closely related species. The assays were sensitive and capable of detecting equivalent to <2 mg roots/kg of dry soil and able to quantify targets in mixed populations. DNA concentration varied with plant age and genotype and DNA in dead roots found to decay rapidly over a few days. DNA concentrations in roots were found to respond more rapidly to defoliation and herbicide treatments than root mass. This approach appears to offer a new way to study roots in soil and indicates that quantifying root DNA could provide insights into root function and responses not readily provided by other methods. [ABSTRACT FROM AUTHOR]

Inoculation of wheat ( Triticum aestivum L. cv. Huamai 8) leaves with wheat powderly mildew fungus ( Blumeria graminis f. sp. tritici) induced cell death in wheat adventitious roots, where no fungal structures were observed. The cytological and molecular characterization of this cell death was shown as following: cell nuclei were TUNEL positive labeled; genomic DNA was fragmented and showed DNA laddering; chromatin condensed and formed peripheral conglomeration in nuclei; and perinuclear spaces partly dilated. These results suggested that, without pathogen spread, the infection could induce systemic PCD in adventitious roots. Comparison with a leaf-cutting experiment (LC)enabled us to speculate that lack of assimilates was not the only reason for the systemic PCD in wheat roots in powdery mildew experiment and that such systemic PCD might be mediated by long-distance signals. In addition, reactive oxygen species (ROS) and Ca2+ were related to the systemic PCD. [ABSTRACT FROM AUTHOR]

Although mycorrhiza has been identified to be of major importance for plant nutrition and ecosystem stability, existing C- and N- simulation models on the ecosystem scale do not explicitly consider the feedbacks between ectomycorrhizal fungi and plants. We present a simple dynamic feedback model which allows estimating the main C- and N- flows between ectomycorrhizal fungi and tree roots in order to test the sensitivity of the system fungus-tree to environmental parameters and to assess the fungal contribution to plant N nutrition. Sensitivity tests carried out showed that the model responses to variations of model parameters, particularly with regard to N availability, are in agreement with published results from field and laboratory studies. However, there are still some processes and parameters which are not well constrained. Fungal N uptake rates and the ratio between mycelium, hartig net, and mantle biomass are parameters which significantly affect model results but for which published data are scarce or missing. Nevertheless, the model is already providing a platform to test our understanding of the importance of mycorrhiza for forest stand nutrition. Future coupling to a mechanistic ecosystem model will allow simulating the importance of mycorrhization for e.g. stand growth and C and N retention. [ABSTRACT FROM AUTHOR]

Glyphosate [(N-(phosphonomethyl)glycine)] is a widely used herbicide and it is known to compete for the same sorption sites in soil as phosphorus. Persistence and losses of glyphosate were monitored in a field with low phosphorus status and possible correlation between glyphosate and phosphorus leaching losses was studied. Glyphosate and its metabolite AMPA (aminomethyl phosphonic acid) residues in soil samples were analysed after a single application in autumn. Twenty months after the application the residues of glyphosate and AMPA in the topsoil (0–25 cm) corresponded to 19% and 48%, respectively, of the applied amount of glyphosate, and traces of glyphosate and AMPA residues were detected in deeper soil layers (below 35 cm). These results indicate rather long persistence for glyphosate in boreal soils. Surface runoff and subsurface drainflow were collected continuously all year round for 20 months and analysed for glyphosate, AMPA, dissolved phosphate, total phosphorus and total suspended solids. The glyphosate concentrations in the surface runoff water were highest, with 99% of the total leaching losses obtained, during the periods of snow melting and soil thawing in the first winter following the autumn application. The total leaching of glyphosate was 5.12 g ha−1 and that of AMPA 0.48 g ha−1, corresponding to about 0.51% and 0.07%, respectively, of the applied amount of glyphosate. No residues of glyphosate and AMPA were detected in the subsurface drainflow. The correlations between concentrations of glyphosate and dissolved orthophosphate as well as glyphosate and total phosphorus in surface runoff were significant ( p < 0.01). [ABSTRACT FROM AUTHOR]

The article presents a discussion on specialized root adaptations that display cell-specific development and physiological diversity. Shovel roots, that are an example of a sprcelised root adaptation for alkaline soils is discussed, along with several researches related to it. These types of roots are found in a type of legume known as sulla, that grows extremely basic soils in the Mediterranean basin. Other types of roots discussed include the proteoid and dauciform.

Architectural descriptors were used to understand root system structure and development in white yam (Dioscorea rotundata Poir., Dioscoreaceae), a tuber monocot. Observations were made on seedlings and plant derived from tuber fragments, cultivated in greenhouses over a developmental cycle. This study demonstrated that both seedlings and plants derived from tubers have two distinct root systems that are highly organized. The first (seminal or tubercular) has been called the temporary root system which is small and short lived. The architectural unit here is made up of two root axis categories. The second (adventitious in both cases) has been called the definitive root system. It is larger and has a far longer lifespan than temporary root systems. The architectural unit here is made up of three root axis categories. Adventitious root systems are formed by structural repetitions of their own architectural unit. The temporary and definitive root systems possess the same structural and functional properties and become established and succeed one another in time following an identical developmental sequence. Neo tuber development is coupled with the root system development. Our results highlight to what extent it is important to study simultaneously the different parts of a root system in order to understand its development. This study confirms how architectural tools can be used to understand root system structure and development and prove accurate informations on root system development for use in agricultural management. [ABSTRACT FROM AUTHOR]