Larger Root System Research Articles

Root-Zone Heat Priming Effects on Maximum Quantum Efficiency of PSII, Productivity, Root Morphology and Nutritional Quality of Two Aeroponically Grown Leafy Greens in a Tropical Greenhouse.

This study investigated the effects of root zone (RZ) heat priming on Eruca sativa (cv. Arugula) and Lactuca sativa (cv. Canasta) in a tropical greenhouse by exposing them to three different RZ temperatures (RZTs). For the first group, plants were grown at 25 °C-RZT for 36 days. The second group of plants was grown at 25 °C-RZT for 10 days before transferring to 38 °C-RZT for 10 days and then to 42 °C-RZT for another 16 days (primed). For the third group, plants were grown at 25 °C-RZT for 20 days and for the last 16 days were transferred to 42 °C-RZT (non-primed). RZ heat priming did not affect the leaf expansion of Arugula while the leaf expansion was slower in RZ heat primed Canasta compared to 25 °C-RZT plants. After transferring to 42 °C-RZT in the later stage, RZ heat primed Arugula had similar productivity but a larger root system with higher nutritional quality at harvest and during postharvest storage compared to those of 25 °C-RZT plants. After subjection to 42 °C-RZT, although RZ heat priming enhanced its nutritional quality, the productivity of Canasta was compromised. The results of this study suggest that it is feasible to enhance productivity and nutritional quality of leafy greens at lower production cost through RZT management.

Characterizing Root Morphological Traits in 65 Genotypes of Foxtail Millet (Setaria italica L.) from Four Different Ecological Regions in China

As an indispensable grain crop, foxtail millet (Setaria italica L.) is becoming a functional food in China because of its abundant nutrients. However, low rainfall and uneven precipitation limit its growth and production, especially in northwest China. Understanding the root phenotypic characteristics of foxtail millet is critical for utilizing its root characteristics to breed new millet varieties with improved resource-use efficiency and better adaptation to harsh environments. The present study characterized the variability of the root morphological traits at the seedling stage of 65 millet genotypes selected from four ecological regions across seven provinces in China. The plants were assessed after 21 days of growth in the germination pouches, and 48 root and shoot traits were measured. The results showed a large variation among the genotypes in the growth and functional traits. Among the measured traits, root dry mass, maximal root length, root surface area, and root tissue density contributed the most to the principal components. Root surface area ratio and root volume ratio were significantly correlated with root length ratio, respectively, while root length density and root weight density were negatively correlated with root diameter (p < 0.01). Shoot dry mass, root number, root length, root dry mass, and total dry mass were closely correlated with each other. Root length and root surface area in each 5-cm sections decreased from the top to the bottom along the root system. Among the four ecological regions, genotypes from the early maturing area of northwest China had the greatest root length, shoot dry mass, root dry mass, and root density, while those from the early maturing area of northwest China generally had the largest root system, with about 2.2 times more root length and dry weight than those from the early maturing area of northeast China (the shortest root system). The genotypic variability in root traits and correlations among shoot and root traits form a basis for breeding new millet cultivars.

Functional Links between Biomass Production and Decomposition of Vetiver (Chrysopogon zizanioides) Grass in Three Australian Soils.

Plant roots are primary factors to contribute to surface and deep soil carbon sequestration (SCS). Perennial grasses like vetiver produce large and deep root system and are likely to contribute significantly to soil carbon. However, we have limited knowledge on how root and shoot decomposition differ and their contribution to SCS. This study examined biomass production and relative decomposition of vetiver which was grown under glasshouse conditions. Subsequently the biomass incubated for 206 days, and the gas analysed using ANCA-GSL. The results confirmed large shoot and root production potential of 161 and 107 Mg ha−1 (fresh) and 67.7 and 52.5 Mg ha−1 (dry) biomass, respectively with 1:1.43 (fresh) and 1:1.25 (dry) production ratio. Vetiver roots decomposed more rapidly in the clay soil (p < 0.001) compared with the shoots, which could be attributed to the lower C:N ratio of roots than the shoots. The large root biomass produced does indeed contribute more to the soil carbon accumulation and the faster root decomposition is crucial in releasing the carbon in the root exudates and would also speed up its contribution to stable SOM. Hence, planting vetiver and similar tropical perennial grasses on degraded and less fertile soils could be a good strategy to rehabilitate degraded soils and for SCS.

Effects of Solar Radiation on Dry Matter Distribution and Root Morphology of High Yielding Maize Cultivars

The root system connects the plant with the soil, which is a key factor in determining the utilization of soil resources and plant growth potential. Solar radiation can change maize shoot and root growth and affect grain formation. In this study, the effects of different solar radiation conditions on root morphology of three maize cultivars XY335, ZD958 and DH618 and their quantitative relationships were studied by conducting shading experiments. This study was conducted in maize high yield region of Qitai and Yinchuan, China, in 2018 and 2019. The planting densities were 7.5 × 104 (D1) and 12 × 104 (D2) plants ha−1. The shading levels were natural light (CK), shading 15% (S1), 30% (S2) and 50% (S3). The results showed that maize responded to the decreased solar radiation through the increase in ratio of shoot dry weight (SWR) to whole plant dry weight and the decrease in ratio of root dry weight (RWR) to whole plant dry weight. As the solar radiation decreased, the root length density (RLD), root surface area (RSA), average root diameter (ARD) and root length ratio (RLR) decreased, while the specific root length (SRL) increased. With 100 MJ m−2 decrease in solar radiation, the RWR, RLD, RSA and RLR each decreased by 1.47%, 0.5 mm cm−3,0.4 m m−2 and 0. 19 m g−1, respectively. Among the cultivars, the changes of DH618 were the fastest followed by XY335 and ZD958 but DH618 maintained the largest root system under any solar radiation condition. After the decrease of solar radiation, RWR, RLD and RLR were significantly positively correlated with the yield. This indicated that large root systems were conducive to the rapid response to decreased solar radiation and important for achieving stable and high yield. Maize cultivars with these type of root systems should be recommended to better adapt low solar radiation induced by regional variation or climate change.

N‐efficient cotton genotype grown under low nitrogen shows relatively large root system, high biomass accumulation and nitrogen metabolism

AbstractA larger root system enhanced biomass accumulation, and high nitrogen (N) metabolism is an effective mechanism of plants in response to low N stress. How cotton plants balance N metabolism and enhanced biomass accumulation to support larger root systems under low N stress remains to be elucidated. This study deals with the changes in root development due to biomass accumulation and N metabolism in contrasting N‐efficient cotton genotypes (CCRI‐69, N‐efficient, and XLZ‐30, N‐inefficient) under low (0.2 mM) and normal (2 mM) N concentrations. The results showed that genotype CCRI‐69 produced a larger root system, high biomass accumulation, and N metabolism than XLZ‐30. The flourishing root system of CCRI‐69 was due to more allocation of sugars from shoot to root, especially under low N concentrations, to support efficient N uptake followed by high N metabolism and N use efficiency (NUE). In addition, CCRI‐69 produced more dry biomass, high photosynthetic activity, N‐related enzymatic activities, N uptake, and utilization under normal N concentration compared with XLZ‐30. Based on multivariate analysis, root morphological traits, sugar contents, and N‐assimilating enzymatic activities might be considered the key traits contributing to NUE and can also be used as potential indicators for genotypic evaluation. In the future, high N metabolism and allocation of more sugars under low N concentration could be studied at a molecular level to better understand the underlying molecular mechanism of NUE in cotton.

Caviano: black bean cultivar with large root system and wide adaptability

‘Caviano’ is a black bean cultivar recommended for Santa Catarina, for being highly adaptable to the main grain-producing regions of the state (mean grain yield 2315 kg ha-1). Compared to previously released cultivars, Caviano has a larger root system and desirable characteristics for mechanical harvesting.

A method for phenotyping roots of large plants

AbstractLinking root traits to plant functions can enable crop improvement for yield and ecosystem functions. However, plant breeding efforts targeting belowground traits are limited by appropriate phenotyping methods for large root systems. While advances have been made allowing for imaging large in situ root systems, many of these methods are inaccessible due to expensive technology requirements. The aim of this work was to develop a plant phenotyping platform and analysis method suitable for assessing root traits of large, intact root systems. With the use of a purpose‐built imaging table and automated photo capture system, machine learning‐based image segmentation, and off‐the‐shelf trait analysis software, the developed method yielded results of comparable accuracy to commercial root scanning platforms without requiring access to prohibitively expensive equipment. This methodology enables root studies to move beyond the size limitations of scanner‐based methods, integrate whole‐system traits like root depth distribution, and save time on root image capture.

Genotypic variability in root length in pea (Pisum sativum L.) and lentil (Lens culinaris Medik.) cultivars in a semi‐arid environment based on mini‐rhizotron image capture

AbstractPhysiological breeding is an approach that complements conventional breeding by providing characterizations of traits present in breeding populations. This allows breeders the ability to choose crosses based on desirable and adaptive traits, an approach that may be more reliable than selection on yield alone. In this study, we determined how much genotypic variability was present in selected lines of modern field pea (Pisum sativum L.) and lentil (Lens culinaris Medik.) cultivars from Montana, North Dakota, Washington, and Saskatchewan, Canada, and if root growth, particularly at depth, improves the fitness of lines to semi‐arid environments. We conducted experiments at the Northern Agricultural Research Center of Montana State University from 2017 to 2019 inclusively to investigate root growth with mini‐rhizotrons in 29 field pea lines and 25 lentil lines. Results suggest there is large genotypic variability in root length across the soil profile and the proportion of root length found below 30 cm in both crops, and these root traits appear independent of each other. In field pea, the highest yielding cultivars were intermediary in both total root length and the proportion of root length below 30 cm, suggesting large root systems and/or deeper root profiles are not necessarily beneficial in this environment. By contrast, in lentil, total root length and root length found below 30 cm was well correlated with biomass and yield. For breeders interested in in improved adaptation to semi‐arid environments, it may be too early to optimize root systems, and above‐ground traits may still yield a better return on investment.

Nitrogen supply improved plant growth and Cd translocation in maize at the silking and physiological maturity under moderate Cd stress

Soil cadmium (Cd) contamination is a serious problem on agricultural land. Adequate nitrogen (N) may help ameliorate plant fitness under Cd stress. This study examined the role of N application in improving maize tolerance to Cd stress. Two maize genotypes, Zhongke11 (larger root system) and Shengrui999 (smaller root system), were grown in a loessal soil amended with Cd (Cd0, no added Cd; Cd1, 20 mg kg−1 soil as CdCl2·2.5 H2O) and N (N0, no added N; N1, 100 mg kg−1 soil as urea) under greenhouse, and plants were assessed at silking and maturity stages. Maize plants exhibited moderate Cd stress with significantly reduced grain yield, especially under low N (N1). Roots accumulated more Cd than above-ground parts. Grain Cd concentration was the least (0.05–0.06 μg g−1) among all organs which is below the safety threshold. Leaf Cd concentrations (0.24–1.18 mg kg−1) were also under the toxicity threshold. Nitrogen addition significantly improved plant growth, chlorophyll content, photosynthesis traits, and tissue Cd contents, and reduced Cd concentration in soil compared to N0 treatment. Nitrogen promoted Cd bioconcentration and translocation factors in stem and leaves. Cadmium stress reduced N fertilizer agronomic efficiency at maturity. At maturity, root Cd content was positively correlated with root N and calcium accumulation, and stem Cd content was positively correlated with stem N content (both P ≤ 0.05). Genotypes with different root system size differed in response to Cd toxicity and / or N deficit. The small-rooted genotype Shengrui999 was more tolerant to moderate Cd stress than the large-rooted Zhongke11. Addition of N ameliorated Cd stress in both maize genotypes by improving plant growth performance, and regulating Cd translocations among plant organs.

Screening of Soybean Genotypes Based on Root Morphology and Shoot Traits Using the Semi-Hydroponic Phenotyping Platform and Rhizobox Technique

Root-system architecture is vital for improving soybean (Glycine max L.) growth and nutrient uptake. We characterised root-system architecture and shoot traits of 30 soybean genotypes in a semi-hydroponic system 35 days after sowing (DAS) and validated eight genotypes with contrasting root-system architecture in 1.5 m-deep rhizoboxes at the flowering stage. Among them, two genotypes were selected for evaluation through to maturity. Abundant variation (coefficient of variation values ≥ 0.25) was observed in 11 of 13 measured roots and shoot traits during the early growth stage. After late growth stages, strong positive correlations were found between root traits and shoot traits, except for specific root length and diameter. Seed yield and yield traits at final harvest significantly differed between two contrasting soybean genotypes. The large-rooted genotype had a higher harvest index than the small-rooted genotype. Soybean genotypes with larger root systems had a long time to flowering than those with smaller root systems. Genotypes with large-root systems had 106% more leaf area, and 245% more shoot dry weight than those with small systems, presumably due to high canopy photosynthesis to supply the demand for carbon assimilates to roots. Total root length, and root: shoot ratio-traits data collected in the rhizobox study, strongly correlated with the same traits in the semi-hydroponic phenotyping system. We found genetic variation and phenotypic plasticity in other root and shoot traits such as taproot depth, root dry weight, specific root length, and average root diameter among the tested genotypes. Phenology, particularly time to flowering, was associated with root system size. Some root and shoot traits in the semi-hydroponic phenotyping system at the seedling stage produced similar rankings at the later phenological (flowering) stage when grown in the soil-filled rhizoboxes. The soybean genotypes characterised by vastly different root traits could be used for further glasshouse and field studies to improve adaptation to drought and other specific environments.

Bioenergy sorghum’s deep roots: A key to sustainable biomass production on annual cropland

AbstractBioenergy sorghum has high biomass yield potential, drought resilience, good nitrogen use efficiency, and a root system that contributes to the accumulation of soil organic carbon. In this study, field grown bioenergy sorghum root systems were analyzed during the growing season to characterize their depth, biomass, morphology, anatomy, and gene expression profiles. Bioenergy sorghum roots grew continuously during a 155‐day growing season producing ~175 nodal roots, accumulating ~7 Mg of dry biomass per hectare, and reaching &gt;2 m deep in the soil profile. Nodal roots within 20 cm of the stem were 1–5 mm in diameter, whereas roots deeper in soil profiles were enriched in lateral roots with small diameters (~30–500 µm) enabling growth through soil macropores. In older field‐grown plants, roots with intact endodermal, vascular and inner root tissues were surrounded by degraded or aerenchyma‐filled epidermal and cortical cell layers. Transcriptome analysis of nodal, surface, and deep roots identified &gt;2,500 differentially expressed genes involved in root growth, transport, adaptation, defense, and AMF–root interaction. Deep roots (180–240 cm) differentially expressed genes that regulate lateral root growth. Surface roots (0–20 cm) located mid‐row differentially expressed genes involved in nitrate transport, whereas ammonium transport genes were expressed in surface and deep roots and genes involved in phosphate transport were expressed in nodal, surface, and deep roots. Overall, bioenergy sorghum's long growing season enables root systems to grow deeper and accumulate more biomass than annual grain crops such as maize, attributes that could help restore annual cropland soil organic carbon levels and improve soil productivity. Deep roots active in nutrient transport are positioned to take‐up fertilizer leached deep into soil profiles mitigating potential nutrient run‐off. Bioenergy sorghum's large and deep root system is a key to sustainable production of biofuels, biopower, and bioproducts on annual cropland.

Arbuscular mycorrhizal symbioses alleviating salt stress in maize is associated with a decline in root-to-leaf gradient of Na+/K+ ratio

BackgroundInoculation of arbuscular mycorrhizal (AM) fungi has the potential to alleviate salt stress in host plants through the mitigation of ionic imbalance. However, inoculation effects vary, and the underlying mechanisms remain unclear. Two maize genotypes (JD52, salt-tolerant with large root system, and FSY1, salt-sensitive with small root system) inoculated with or without AM fungus Funneliformis mosseae were grown in pots containing soil amended with 0 or 100 mM NaCl (incrementally added 32 days after sowing, DAS) in a greenhouse. Plants were assessed 59 DAS for plant growth, tissue Na+ and K+ contents, the expression of plant transporter genes responsible for Na+ and/or K+ uptake, translocation or compartmentation, and chloroplast ultrastructure alterations.ResultsUnder 100 mM NaCl, AM plants of both genotypes grew better with denser root systems than non-AM plants. Relative to non-AM plants, the accumulation of Na+ and K+ was decreased in AM plant shoots but increased in AM roots with a decrease in the shoot: root Na+ ratio particularly in FSY1, accompanied by differential regulation of ion transporter genes (i.e., ZmSOS1, ZmHKT1, and ZmNHX). This induced a relatively higher Na+ efflux (recirculating) rate than K+ in AM shoots while the converse outcoming (higher Na+ influx rate than K+) in AM roots. The higher K+: Na+ ratio in AM shoots contributed to the maintenance of structural and functional integrity of chloroplasts in mesophyll cells.ConclusionAM symbiosis improved maize salt tolerance by accelerating Na+ shoot-to-root translocation rate and mediating Na+/K+ distribution between shoots and roots.

Lodging resistance in maize: A function of root–shoot interactions

The differences in root and stem structure between lodging resistant (LR) and susceptible (LS) genotypes have yet to be fully understood in maize (Zea mays L.). To clarify these differences, lodging rates and yield of LS genotype XunDan20 (XD20) and LR genotype FuMin985 (FM985) across five locations in China from 2014 to 2018 were investigated. Simultaneously, field experiments including genotypes XD20 and FM985 and two plant densities of 75,000 (D75000) and 105,000 plant ha−1 (D105000) were specifically performed at two locations in North China Plain in 2018. Stem and root lodging rates of XD20 were significantly higher than that of FM985 mainly because FM985 had a larger root system and a stronger basal stem. Compared to XD20, FM985 had significantly larger values in root crown width, root angle, length (+37.1 %), volume (+25.5 %), and length density (+29.9 %) in 0−10 cm soil. Although FM985 had longer and thinner basal stem internodes, the larger sclerenchyma and more compact distribution of epidermal cells in the rind resulted in greater rind penetration strength in FM985 than in XD20. Results from 13C and 15N isotope labelling revealed that the high stem strength and root anchorage strength of FM985 were related to the large assimilate allocations to roots and basal internodes. With increased plant density, XD20 had larger reductions in stem morphological parameters, leading to a smaller stem lodging resistance; FM985 showed larger reductions in root traits but still had a high root lodging resistance at high plant density due to the large root system. LR maize allocates more photosynthetic assimilates to roots and stems and maintains a higher capacity of nutrient absorption, reflecting a function of root–shoot interactions during formation and maintenance of lodging resistance.

Influence of Phosphite Supply in the MS Medium on Root Morphological Characteristics, Fresh Biomass and Enzymatic Behavior in Five Genotypes of Potato (Solanum tuberosum L.)

Crop production is threatened by low phosphorus (P) availability and weed interference. Obtaining plant genotypes that can utilize Phosphite (Phi) as fertilizer can supplement phosphates (Pi) while providing an environmentally friendly means of weed control. The study was conducted to determine the tolerance and enzymatic behavior of five potato genotypes to PO3. Explants were regenerated in vitro from two nodal cuttings and cultured on Murashige and Skoog (MS) medium under controlled conditions for 30 days. Matured plantlets were subcultured for 20 days in MS medium containing (0.25, 0.5 mM) Phi and Pi and No-P (-Phi + -Pi). The results showed significant genotypic variation in tolerance indices among the five genotypes. Atlantic showed greater tolerance to Phi, with highest total root length (50.84%), root projected area (75.09%), root surface area (68.94%), root volume (33.49%) and number of root forks (75.66%). Phi induced an increasing trend in the levels of hydrogen peroxide in the genotypes with the least effect in Atlantic. The comprehensive evaluation analysis confirmed the tolerance of Atlantic genotype with this ranking; Atlantic, Longshu3, Qingshu9, Longshu6 and Gannong2. Antioxidant enzyme activities and proline content also increased significantly under Phi and No-P treatments. The results suggested that potato genotypes with larger root systems may be more tolerant to Phi than genotypes with smaller root systems.

Grafting improves nitrogen-use efficiency by regulating the nitrogen uptake and metabolism under low-nitrate conditions in cucumber

Excessive application of nitrogen (N) fertilizer can inhibit plant growth, reduce the N-use efficiency (NUE), increase fertilizer waste, and leads to secondary salinization. Grafting provides a feasible method for improving N uptake and utilization of plants under abiotic stress, but the mechanism by which grafting regulates N uptake, assimilation, and metabolism under low-nitrate conditions is poorly known. To explore the mechanism of rootstock grafting promoting plant growth and N absorption and utilization, in this study, a commercial cucumber cultivar (‘Jinchun No. 4’, a relatively N-inefficient cultivar) was self-grafted and grafted onto two pumpkin rootstocks (‘Figleaf Gourd’, a relatively N-medium efficiency pumpkin cultivar, and ‘Ribenjingtiantaimu’, a relatively N-efficient pumpkin cultivar, respectively). The grafted plants were exposed to two levels of NO3−-N (7 and 4 mM) under substrate culture conditions. Root morphological traits; NH4+, NO3−, and total N contents; N-based enzymatic activities; and N metabolite contents of self-grafted plants (J/J) were all markedly inhibited by low-nitrate treatment, leading to lower N accumulation (NA), N-uptake efficiency (NUpE), N-utilizition efficiency (NUtE) and NUE than rootstock-grafted plants (J/F and J/R). In contrast, the inhibition caused by the low-nitrate treatment was effectively alleviated in J/R-grafted plants, as J/R-grafted plants had the largest root systems and the strongest potential for N absorption and metabolism. Variation in these parameters was determined by the rootstock genotype and contributed greatly to improvements in NUpE, NUtE and NUE. Overall, our findings demonstrate that grafting with N-efficient rootstock can permit plants to make better use of their roots and enhance N absorption and N metabolism potential, thereby promoting the growth and NUE of cucumber seedlings. Furthermore, our findings infer that grafting with N-efficient rootstock may permit high levels of productivity to be maintained under low N supplies during cucumber production.

Root engineering in maize by increasing cytokinin degradation causes enhanced root growth and leaf mineral enrichment

Key messageRoot-specific expression of a cytokinin-degrading CKX gene in maize roots causes formation of a larger root system leading to higher element content in shoot organs.The size and architecture of the root system is functionally relevant for the access to water and soil nutrients. A great number of mostly unknown genes are involved in regulating root architecture complicating targeted breeding of plants with a larger root system. Here, we have explored whether root-specific degradation of the hormone cytokinin, which is a negative regulator of root growth, can be used to genetically engineer maize (Zea mays L.) plants with a larger root system. Root-specific expression of a CYTOKININ OXIDASE/DEHYDROGENASE (CKX) gene of Arabidopsis caused the formation of up to 46% more root dry weight while shoot growth of these transgenic lines was similar as in non-transgenic control plants. The concentration of several elements, in particular of those with low soil mobility (K, P, Mo, Zn), was increased in leaves of transgenic lines. In kernels, the changes in concentration of most elements were less pronounced, but the concentrations of Cu, Mn and Zn were significantly increased in at least one of the three independent lines. Our data illustrate the potential of an increased root system as part of efforts towards achieving biofortification. Taken together, this work has shown that root-specific expression of a CKX gene can be used to engineer the root system of maize and alter shoot element composition.

Morphological and mechanical variables associated with lodging in maize (Zea mays L.)

Lodging is a function of many factors, but their relative importance is unclear in maize. To clarify this, a two year field experiment that involved six maize genotypes and two plant densities was conducted in 2018 and 2019. Genotypes with a similar growth cycle length but different lodging resistance were selected and sown in April 2018 and May 2019, respectively. As using single indicator aboveground or belowground to assess lodging resistance is inaccurate, both root (R) and shoot (S) traits were considered in the present study. Based on the ratio of root angle and fresh weight of shoot, lodging resistant (LR) genotypes were classified into LRR>S and LRR≈S, and lodging susceptible (LS) genotypes into LSR<S and LSR<<S. LRR>S displayed the largest stem and root safety factor values (SFs and SFr, representing lodging resistance) due to higher dry weight per unit length (DWUL) of the 3rd stem internode aboveground, larger root system, and stiffer upper roots compared to other genotype groups. Both LSR<S and LSR<<S were sensitive to lodging due to large values in fresh weight (FW) of aboveground plant, plant height (PH), and height at center of gravity (GH). At high plant density, LR genotypes had higher SFr and SFs due to reduced FW and self-weight moments of stem (Ms) and root (Mr) compared to LS genotypes. Both SFs and SFr were higher at harvest than at 30 d after silking because of reduced FW and GH and increased DWUL. SFr and SFs were significantly correlated at 30 d after silking and harvest. No lodging occurred at root dry weight> 17.79 g, and SFs had the largest value at DWUL > 0.556 g cm−1. LR genotypes on average yielded better than LS genotypes. There appears to be trade-offs between lodging resistance and high-yielding in maize. Optimizing assimilates partitioning among ear, basal stem, and upper roots should be considered when increasing lodging resistance and yield in maize.

Evaluation of arsenic remediation, morphological and biochemical response by Vetiveria zizanoides L. plants grown on artificially arsenic contaminated soil: A field study

The present study evaluated arsenic (As) remediation capacity of Vetiveria. zizanoides plants from artificially contaminated soil (0, 50, 100, 250, 500, 1000 mg kg−1) after various durations ie. 30, 60 and 90 d. Plants were found effective, maximum As removal being 71% after 90 d when grown in 50 mg kg−1 As. Plant growth was not affected at lower As levels (up to 250 mg kg−1) and V. zizanoides plants grown at 50 mg kg−1 have shown increase in number of tillers (43%), biomass (30%) and plant height (26%) compared to control after 90 days. Thiobarbituric acid reactive metabolites (TBARM) content has not shown any change in As exposed plants up to 30 d, maximum increase in TBARM content was found in roots and shoots of the V. zizanoides plants as 84% and 79% after 90 d when grown at 1000 mg kg−1 As contaminated plot. The activities of antioxidant enzymes, superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase and catalase were found to increase in response to As stress in a coordinated manner. Besides, various non- enzymatic antioxidants also provided defense to plants against As stress. High As accumulation and tolerance potential of V. zizanoides from artificially contaminated soil coupled with large biomass and root system, suggests its feasibility for the revegatation/remediation of As contaminated soils of West Bengal (India).

Comparison of numerical methods for radial solute transport to simulate uptake by plant roots

The 1D radial solute transport model with non-linear inner boundary condition is widely used for simulating nutrient uptake by plant roots. When included into an architectural root model, this local model has to be solved for a high number of root segments, e. g. 105 – 106 segments for large root systems. Each root segment comes with its own local parameter set in heterogeneous root architectural models. Depending on the soil and solute, the effective diffusion coefficient spans over more than six orders (e. g. for N, K, and P). Thus a numerical implementation of this rhizosphere transport model is required to be fast, accurate and stable for a large parameter space. We apply 13 methods to this rhizosphere model with root hairs and compare their accuracy, computational speed, and applicability. In particular, the Crank-Nicolson method is compared to higher-order explicit adaptive methods and some stiff solvers. The Crank-Nicolson method sometimes oscillated and was up to a hundred times slower than an explicit adaptive scheme with similar accuracy. For a given spatial resolution, Crank-Nicolson had about one order lower accuracy as other tested methods. The maximum spatial time step can be estimated from root radius, solute diffusion, advection, and soil buffer power. Although Crank-Nicolson is a viable method and often used as de-facto standard method for rhizosphere models, it was not the best performer in our comparison. While the best method remains problem specific, for general use in root architectural models we recommend adaptive Runge-Kutta with cubic or quadratic upwind for advection.

JASMONATE RESISTANT 1 negatively regulates root growth under boron deficiency in Arabidopsis.

Boron (B) is an essential micronutrient for plant growth and development. Jasmonic acid (JA) plays pivotal roles in plant growth, but the underlying molecular mechanism of JA involvement in B-deficiency-induced root growth inhibition is yet to be explored. In this study, we investigated the response of JA to B deficiency and the mechanism of JAR1-dependent JA signaling in root growth inhibition under B deficiency in Arabidopsis. B deficiency enhanced JA signaling in roots, and root growth inhibition was partially restored by JA biosynthesis inhibition. The jar1-1 (jasmonate-resistant 1, JAR1) mutant, and mutants of coronatine-insensitive 1 (coi1-2) and myc2 defective in JA signaling showed insensitivity to B deficiency. The ethylene-overproduction mutant eto1 and ethylene-insensitive mutant etr1 showed sensitivity and insensitivity to B deficiency, respectively, suggesting that ethylene is involved in the inhibition of primary root growth under B deficiency. Furthermore, after a decline in levels of EIN3, which may contribute to root growth, ethylene signaling was weakened in the jar1-1 mutant root under B deficiency. Under B deficiency, B concentrations were increased in the roots and shoots of the jar1-1 mutant, owing to the large root system and its activity. Therefore, our findings revealed that JA, which is involved in the inhibition of root growth under B deficiency, is regulated by JAR1-activated JA and ethylene signaling pathways.