Root Surface Area Research Articles

Biochar amendment combined with partial root-zone drying irrigation alleviates salinity stress and improves root morphology and water use efficiency in cotton plant

An adsorption experiment and a pot experiment were executed in order to explore the mechanisms by which biochar amendment in combination with reduced irrigation affects sodium and potassium uptake, root morphology, water use efficiency, and salinity tolerance of cotton plants. In the adsorption experiment, ten NaCl concentration gradients (0, 50, 100, 150, 200, 250, 300, 350, 400, and 500 mM) were set for testing isotherm adsorption of Na+ by biochar. It was found that the isotherms of Na+ adsorption by wheat straw biochar (WSP) and softwood biochar (SWP) were in accordance with the Langmuir isotherm model, and the Na+ adsorption ability of WSP (55.20 mg g−1) was superior to that of SWP (47.38 mg g−1). The pot experiment consisted three factors, viz., three biochar amendments (no biochar, WSP, and SWP), three irrigation strategies (deficit irrigation, partial root-zone drying irrigation – PRD, full irrigation), and two NaCl concentrations gradients (0 mM and 200 mM). The findings indicated that salinity stress lowered K+ concentration, root length, root surface area, and root volume (RV), but increased Na+ concentration, root average diameter, and root tissue density. However, biochar amendment decreased Na+ concentration, increased K+ concentration, and improved root morphology. In particular, the combination of WSP and PRD increased K+/Na+ ratio, RV, root weight density, root surface area density, water use efficiency, and partial factor productivity under salt stress, which can be a promising strategy to cope with drought and salinity stress in cotton production.

The selection of intra-inter specific Cucurbita rootstocks for grafted melon seedlings

This study was conducted to select promising Turkish local Cucurbita rootstocks among intraspecific and interspecific hybrids for grafted melon seedling based on hybrid success rate, hypocotyl traits and graft compatibility. Rooting potentials, root system architecture and plant growth parameters of the rootstocks grafted with melon were also evaluated. Two lines of C. maxima (male parent) and eleven lines of C. moschata (female parent) at S5 generation were used. In addition, six winter squash lines were used as male parent and six pumpkin lines were used as female parent in intraspecific hybridization program. Intraspecific hybrid combinations had quite high number of seeds per fruit as compared to interspecific hybrid combinations. The highest number of seeds per fruit was obtained from HMO2 × OMO2 (359) and OMO5 × HMO8 (314) hybrid combinations. Hypocotyl lengths of all hybrid cucurbit rootstock combinations ranged from 32.96 mm (RS17) to 73.35 mm (RS8) and hypocotyl thicknesses ranged from 2.71 mm (RS2) to 3.55 mm (RS8). Graft success rates varied between 96.6 – 100% in winter squash and pumpkin intraspecific hybrids and between 87.1 – 100% in interspecific hybrids. Significant differences were seen in root architecture parameters (root length, root volume, mean root diameter, root surface area and root dry matter weight) of intraspecific and interspecies hybrid Cucurbita lines. The findings of the study indicated that the intraspecific and interspecific local cucurbit rootstock candidates developed within the rootstock breeding program showed promise as viable options for commercial use as rootstocks for grafted melon seedlings. Research about the effects of selected intraspecific and interspecific hybrid Cucurbita rootstock candidates on earliness, fruit quality and yield parameters of grafted melon will continue.
 Keywords: Cucurbita maxima; Cucurbita moschata; Rootstock breeding; Root system architecture; Melon

Phenotypic Variations in Banana Cultivars in the Utilization and Tolerance to Different Magnesium Levels

Magnesium (Mg) is the most commonly deficient nutrient in tropical banana-growing areas. The effects of different concentrations of Mg on morpho-physiological and biochemical responses on three commercial cultivars (Baxi, Haigong, and Guangfen No.1) of bananas were accessed for 12 weeks. Results showed genotypic variation in the utilization and tolerance to different Mg levels. The optimum Mg level was 1 mM for Baxi and Guangfen No.1 and 3 mM for Haigong. Both the deficiency and excess of Mg caused a severe reduction in plant height, dry weight, total root length, and root surface area of Haigong and Baxi. Mg stress reduced root growth by impairing photosynthate translocation and increased carbohydrate contents in the source leaf. Under Mg stress, more reduction in photosynthetic pigment and photosynthesis rate, higher accumulation of carbohydrates and malondialdehyde contents, and higher activities of antioxidative enzymes were observed in Haigong as compared to other genotypes. Based on the above results, it is concluded that Haigong is most sensitive to Mg stress while Guangfen No. 1 was least affected and tolerant to changes in the Mg levels.

The Physiological Mechanism of Melatonin Enhancing the Tolerance of Oat Seedlings under Saline–Alkali Stress

Exogenous melatonin (MT) regulates plant growth and mitigates stress in response to stress. To analyze the machinery of exogenous melatonin, which improves salt and alkaline tolerance in oats, MT’s function was identified in the oat seed germination stage in our previous study. In this study, morphogenesis, photosynthetic physiology, hormone levels, and ion homeostasis were evaluated using the same MT treatment concentration. The results revealed that compared to the S45 treatment, the 100 μmol·L−1 MT treatment efficiently increased the seedling height and main root length of oat seedlings; promoted secondary root development; enhanced the root volume and root surface area; maintained a higher photosynthetic pigment content (carotenoids; chlorophyll a; chlorophyll b); raised the leaf photosynthetic rate (Pn), intercellular CO2 concentration (Ci), conductance to H2O (Gs), and transpiration rate (Tr); enhanced the light energy absorption and conversion of leaves; increased the leaf GA3, Tryptamine (TAM), and IAA contents; and decreased ABA levels. Hierarchical cluster analysis revealed that MT treatment also increased the contents of P, K, Ca, Mn, Cu, Mg, Fe, Zn, Mo, Cd, Al, Se, Ni, Co, and Ti; decreased the Na/K ratio; and maintained cellular ionic homeostasis in oat seedlings under saline–alkali stress, as compared with the untreated group. These findings showed that MT treatment enhanced the adaptation of oat to saline–alkali stress through regulating the physiological process of seedling growth. This suggests that MT plays a different role in improving saline–alkali tolerance in the germination and seedling stages of oat.

Revealing the Mechanistic Basis of Regulation of Phosphorus Uptake in Soybean (Glycine max) Roots by Molybdenum: An Integrated Omics Approach.

While molybdenum (Mo) application can improve phosphorus (P) availability to plants by changing P speciation in the rhizosphere, the mechanistic basis of this process remains unclear. This work investigated the impact of various combinations of Mo and P treatments on root morphology, P and Mo uptake, and root transcriptome and metabolome. Mo application significantly increased soybean biomass and the number of lateral roots at both low (5 μmol) or normal (500 μmol) P levels and significantly improved P concentration and accumulation in Normal P treatment. Compared with the Normal P treatment, Low P significantly increased the number of roots, root surface area, and root acid phosphatase secretion. A total of 6811 Mo-responsive differentially expressed genes and 135 differential metabolites were identified at two P levels. At Low P, transcriptional changes significantly increased root synthesis and secretion of succinic acid, methylmalonic acid, and other organic acids as well as acid phosphatase, thereby increasing the conversion of soil aluminum-bound P and organic P into available P. At Normal P, Mo application increased P uptake mainly by increasing the number of lateral roots. Thus, Mo helps crops adapt to different P levels by regulating root anatomy and transcriptional and metabolic profiles of their roots.

An arbuscular mycorrhizal fungus differentially regulates root traits and cadmium uptake in two maize varieties

Arbuscular mycorrhizal fungi (AMF) are symbiotic fungi that colonize plant roots, and they are more common in Cd-polluted habitats. However, there is limited understanding of the response of root traits and cadmium (Cd) uptake to AMF in different crop varieties. Two maize varieties, Panyu 3 and Ludan 8, with high and low Cd uptake capacities, respectively, were cultivated as host plants in a pot experiment with Cd-polluted soil (17.1 mg/kg Cd). The effects of AMF on the growth, mineral nutrient concentration, root traits, phytohormone concentrations and Cd uptake of the two maize varieties and their comprehensive response to AMF fungal inoculation were investigated. AMF improved growth, mineral nutrient levels and root morphology and increased lignin and phytohormone concentrations in roots and Cd uptake in the two maize varieties. However, the two maize varieties, Panyu 3 and Ludan 8, had different responses to AMF, and their comprehensive response indices were 753.6% and 389.4%, respectively. The root biomass, branch number, abscisic acid concentrations, lignin concentrations and Cd uptake of maize Panyu 3 increased by 151.1%, 28.6%, 139.7%, 99.5% and 84.7%, respectively. The root biomass, average diameter, auxin concentration, lignin concentration and Cd uptake of maize Ludan 8 increased by 168.7%, 31.8%, 31.4%, 41.7% and 136.7%, respectively. Moreover, Cd uptake in roots presented very significant positive correlations with the average root diameter and abscisic acid concentration. A structural equation model indicated that the root abscisic acid concentration and root surface area had positive effects on Cd uptake by the Panyu 3 maize roots; the root abscisic acid concentration and root tip number had positive effects on Cd uptake by the Ludan 8 maize roots. Thus, AMF differentially regulated Cd uptake in the two maize varieties, and the regulatory effect was closely related to root traits and phytohormone concentrations.

The Relationships between Root Traits and the Soil Erodibility of Farmland Shelterbelts in the Bashang Region of China

Soil erodibility by wind is not only affected by the basic physical and chemical properties of the soil but also the functional traits of plant roots. However, the roles played by the morphological and architectural traits of plant roots on wind-based soil erodibility in the Bashang region of China are still unclear. Therefore, two typical tree shelterbelts and two shrub shelterbelts in the Bashang region were selected to assess and determine how the root traits affected soil erodibility, especially characteristics such as dry aggregate, soil organic matter, and shearing resistance. The results showed that the soil dry aggregates of the two shrubs (Lycium barbarum and Caragana korshinskii) had higher geometric mean diameters (0.40 ± 0.03 mm) and mean weight diameters (0.82 ± 0.08 mm) but a lower erodible fraction (81.81% ± 1.62%) compared to the two trees (Populus simonii and Ulmus pumila). The mean weight diameter (MWDd) and geometric mean diameter (GMDd) of dry soil aggregates were negatively correlated with the soil erodible fraction (EFd), but these parameters were positively correlated with shearing resistances. The specific root length (SRL) and surface area (SSA) of plant roots were positively correlated with the GMDd of the soils, though these two parameters negatively correlated with the soil erodible fraction. The root branching intensity (BI) was negatively correlated with the MWDd and GMDd of dry soil aggregates. The total carbon or nitrogen of the soil displayed significantly positive and negative correlations to the geometric mean diameters and erodible fractions of the soils, respectively. The findings showed that plant roots with higher SRLs, as well as lower root diameters and BIs, played positive key roles in soil stability. The same applied to soils with higher nitrogen, carbon, and water content. The results from this study suggest that L. barbarum is superior to the other three species based on root traits and wind erosion resistance. These findings provide critical information for selecting plants for the sustainable management of windbreak and sand fixation.

Comparison of Root Coverage by the Subepithelial Connective Tissue Graft With and Without Root Biomodification: A Comprehensive Clinical Study.

Being an autologous graft, a subepithelial connective tissue (SECT) graft shows more predictable root coverage better than other techniques. Hence, it is most likely to be widely used for recession treatment. During root planing, a smear layer forms on the root surface that cannot be removed by water or saline rinsing. To remove this smear layer, root biomodification agents are widely used.The present study was conducted to assess the efficacy of an SECT graft for root coverage with and without root biomodification. This study included 20 patients with no gender predilection, with an age range of 24-36 years and a mean age of 27.6 ± 4.24 years. The chosen range facilitatedthe acquisition of data in a relatively homogeneous population, minimizing the confounding effects of factors such as aging-related tissue changes or early-onset periodontal issues.All 40 sites were treated with the SECT and coronally advanced flap. Root conditioning in controls was done with distilled saline and tested using 24% ethylenediaminetetraacetic acid (EDTA) gel (Maquira; STM Meditech, Kerala). At baseline and at one, three, and six months postoperatively, pocket depth (PD) and clinical attachment levels (CALs) were assessed at four sites using a UNC-15 probe, and from the gingival margin to the cementoenamel junction (CEJ), the vertical recession was assessed. For the buccal surface, CALs were reduced significantly (p < 0.001). Following root conditioning with 24% EDTA, no difference was seen in the CAL in the control and test group either buccally or interproximally with a p-value of greater than 0.05. For PD, following a SECT graft or root conditioning, no significant change was observed in the buccal or interproximal region (p > 0.05). The vertical recession was significantly reduced with a p-value of less than 0.001 and depth coverage of 97.5%. The difference between the two groups was statistically non-significant (p > 0.05). The root surface coverage decreased significantly from 16.6 ± 2.8 to 0.45 ± 0.4 from baseline to six months, which was statistically significant (p < 0.001). This intergroup difference was non-statistical (p > 0.05). The present study concludes that the use of an SECT graft in root coverage can significantly improve the CAL, root surface area, and vertical recession both with and without root biomodification. We conclude that there is a significant decrease in the probing depth following SECT grafting and with root biomodification.

Impact of paclobutrazol on storage root number and yield of sweet potato (Ipomoea batatas L.)

Increasing storage root number is an important way to improve the yield of sweet potato. Here, two-year field experiments were conducted to study the effect of 0 (CK), 10, 20 and 30 mg kg−1 paclobutrazol (PBZ) on the phytohormones and lignin biosynthesis, and root growth and yield of sweet potato. The current study found that PBZ10 decreased the concentration of phytohormones gibberellin 3 (GA3), indole acetic acid (IAA) and abscisic acid (ABA) in the subterranean stem, whereas increased the concentration of zeatin riboside (ZR) and methyl jasmonate (MeJA), resulting in lower root length, volume and tip number at 3 and 5 days after planting (DAP). At 5 DAP, PBZ10 decreased GA3, MeJA and ABA concentration in adventitious root, and increased IAA and ZR concentrations, resulting in increased root length, volume, tip number and surface area at 10 DAP. By 5–30 DAP, PBZ10 decreased the concentration of GA3 and ABA in potential storage roots and increased the concentration of IAA, ZR and MeJA, thus increasing root number. At 10–20 DAP, PBZ10 decreased the lignin concentration in the potential storage root along with the expression of IbEXP1 and the enzymatic activities of phenylalanine ammonialyase, 4-coumaric acid CoA ligase and peroxidase, which are involved in the regulation of lignin biosynthesis, resulting in increased potential storage root diameter; interestingly, the opposite pattern was observed by 25–30 DAP. Then, PBZ10 increased the SR number at 40 DAP, and the yield of sweet potato at harvest time, and no PBZ was detected in SRs of PBZ10. But excessive concentration of PBZ is unfavorable to root development and led to a decrease of yield. These results indicated that a moderate PBZ (10 mg kg−1) application could reasonably regulate phytohormones and lignin biosynthesis, then increase storage root number and yield of sweet potato.

Genotypic differences in root architecture and physiological characteristics in mango (Mangifera indica) under drought

An experiment was conducted at the research farm of ICAR-Indian Agricultural Research Institute, New Delhi during 2020 and 2021 to study the genotypic differences in root architecture and physiological characteristics in mango (Mangifera indica L.) under drought. One-year-old polyembryonic 7 mango rootstock genotypes were exposed to normal irrigation and drought conditions for 24 days. The drought-induced increased total plant weight and dry weight in Kurukkan. The shoot dry weight decreased in all genotypes ranging from 5.13% in OLP-Z-6/1 to 81.82% in Kurukkan. There was a lesser reduction in membrane stability index in Kurukkan and K-5, stomata count in Kurukkan, Olour and OPK-3-7/12 at the end of the drought period. Root surface area increased under drought in Kurukkan, while it decreased more in K-5. Correlation studies confirmed a strong positive relationship between relative water content (RWC) and membrane stability index (MSI), number of stomata (SC), number of leaves (NL), root tips (RT) and root forks (NRF); MSI and number of root tips (NRT); dry weight of the whole plant and root surface area (RSA); the dry weight of roots and root volume (RV), RSA, and plant height (Ph); root length (RL) and RSA, RT, and NRF. Kurukkan was identified as drought-tolerant based on a higher SC, RWC, RV, RSA, dry mass, NRT and NRF. Results indicated that the root indices offer a promising strategy for the screening of drought-tolerant mango genotypes.

Enhancing maize yield through understanding the novel shoot-root interaction in morphology among hybrids with dense planting

ContextUnderstanding the shoot-root characteristics and their interaction of maize is essential to break the constraints of the densification process and improve grain yield. ObjectiveThe objective of the work was to study the interaction between the above-ground canopy and below-ground root system in morphology and its relationship to grain yield in dense planting with different hybrids. MethodsThis study conducted a 2-yr field experiment with three modern hybrids (JNK728, ZD958 and XY335) at the Wuqiao Experimental Station in Northern China. ResultsAmong hybrids, XY335 attained the highest grain yield of 14,886.9 kg hm−2 in 2019 and 10,078.8 kg hm−2 in 2020 with a density of 7.5 × 104 plants hm−2. For the shoot at the silking stage (R1), the lowest leaf orientation value for both middle and upper leaves and ear-to-height ratio among three hybrids were found in XY335 with the compact plant phenotype. Meanwhile, the highest photosynthesis rate of ear leaves (33.0 umol m2˙s−1) at R1 was also observed in XY335. At physiological maturity (R6), the above-ground dry matter (AGDM) was 4.6%− 10.4% higher in XY335 than the other two hybrids. For the root system at both R1 and R6 with the density of 7.5 × 104 plants hm−2, the highest value for root system indicators in morphology such as root total length (RL), root surface area (RSA), root volume (RV) was observed in XY335. From R1 to R6, RL, RSA and RV in XY335 averaged 24,749.6 cm, 3486.8 cm2, 51.5 cm3, 1.3–14.6% higher than JNK728, and 10.2–23.9% higher than ZD958, respectively. Furthermore, the lower senescence of the root system was also observed in XY335, with a 22.0–32.1% lower decrease from R1 to R6 in RL, RSA, and RV compared with the other two hybrids. ConclusionsFor the shoot-root interaction, per unit decrease in morphology indicator in the root per plant with density increase of XY335 accompanied with more AGDM accumulation and thus higher grain yield. ImplicationsThe observations on shoot-root characteristics and their interaction from this study are essential to selecting a hybrid that allows a better adaptation to planting at high density, developing an effective management strategy, and breeding high-density tolerant hybrids.

Toxicity of chromium to wheat (Triticum aestivum L.) in two soils: influence of soil properties and chromium form.

The toxicity of Cr to plants depends on Cr form and soil properties. Currently, the phytotoxicity differences of Cr(VI) and Cr(III) in different soils are not clear. In this study, the toxicity of Cr(VI) and Cr(III) to root growth and root morphology of wheat (Triticum aestivum L.) were compared in Shandong fluvo-aquic soil (SD soil) and Jiangxi red soil (JX soil) that is differing in soil properties. The toxicity thresholds of Cr(VI) and Cr(III) on wheat root elongation were determined by fitting the dose-effect curves. Results showed that the 10% and 50% root length inhibitory concentrations (EC10 and EC50) of Cr(III) were 53.1 and 125 times of Cr(VI) in SD soil and 8.11 and 1.36 times of Cr(VI) in JX soil, indicating that Cr(VI) was more toxic to wheat roots than Cr(III) in both soils and the toxicity discrepancy of the two forms of Cr was more prominent in SD soil. Cr(VI) exhibited higher toxicity in SD soil (alkaline) than in JX soil (acidic), whereas Cr(III) showed the opposite pattern. In addition, the ethylene diamine tetraacetic acid extractable Cr (EDTA-Cr) concentrations in soils were correlated well with the relative wheat root elongation (R2=0.854, P<0.01), indicating that soil EDTA-Cr concentration can be used as a predictor of Cr phytotoxicity. Both Cr(VI) and Cr(III) showed significant biphasic dose effects on wheat root morphology (root length, root surface area, root volume, and root tip number) in JX soil. These findings are helpful for the risk evaluation of Cr contamination in agricultural soils.

Root Architecture of Forage Species Varies with Intercropping Combinations

Belowground root systems under pasture intercropping exhibit complex interactions, and the root interactions of different intercropping combinations are still poorly understood. Therefore, in this work, two perennial and annual herbages were intercropped in pairs and evaluated at a ratio of 1:1. The root morphology and topological structure differed significantly with intercropping combinations. (1) Compared with other cropping patterns, the mean root diameter (RD) of intercropped alfalfa (Medicago sativa L.) and common vetch (Vicia sativa L.) increased notably. The root surface area (RSA), root volume (RV), and mean RD increased significantly when oat (Avena sativa L.) was intercropped with alfalfa. Similarly, the RSA and RV increased in intercropped oat, intercropping relative to monocropping. (2) The forage topological index of the intercropping system was close to one, which was close to that of the herringbone branching. Additionally, the intercropping system had a lower intensity of underground root competition. The root system of the different forage intercropping combinations tended to transition to dichotomous branching. (3) The correlations between root parameters differed according to forage species. Therefore, different intercropping combinations had different belowground root levels of competitiveness and interactions, thereby changing the resource competition environment.

Enhancing Phosphorus and Nitrogen Uptake in Maize Crops with Food Industry Biosolids and Azotobacter nigricans.

The problem of phosphorus and nitrogen deficiency in agricultural soils has been solved by adding chemical fertilizers. However, their excessive use and their accumulation have only contributed to environmental contamination. Given the high content of nutrients in biosolids collected from a food industry waste treatment plant, their use as fertilizers was investigated in Zea mays plants grown in sandy loam soil collected from a semi-desert area. These biosolids contained insoluble phosphorus sources; therefore, given the ability of Azotobacter nigricans to solubilize phosphates, this strain was incorporated into the study. In vitro, the suitable conditions for the growth of Z. mays plants were determined by using biosolids as a fertilizer and A. nigricans as a plant-growth-promoting microorganism; in vitro, the ability of A. nigricans to solubilize phosphates, fix nitrogen, and produce indole acetic acid, a phytohormone that promotes root formation, was also evaluated. At the greenhouse stage, the Z. mays plants fertilized with biosolids at concentrations of 15 and 20% (v/w) and inoculated with A. nigricans favored the development of bending strength plants, which was observed on the increased stem diameter (>13.5% compared with the negative control and >7.4% compared with the positive control), as well as a better absorption of phosphorus and nitrogen, the concentration of which increased up to 62.8% when compared with that in the control treatments. The interactions between plants and A. nigricans were observed via scanning electron microscopy. The application of biosolids and A. nigricans in Z. mays plants grown in greenhouses presented better development than when Z. mays plants were treated with a chemical fertilizer. The enhanced plant growth was attributed to the increase in root surface area.

Morphological, physiological and metabolomic analysis to unravel the adaptive relationship between root growth of ephemeral plants and different soil habitats

To gain insights into the adaptive characteristics of ephemeral plants and enrich their potential for resource exploitation, the adaptive changes in two highly dominant species (Malcolmia scorpioides and Isatis violascens) to soil habitats (aeolian soil, AS; grey desert soil, GS) were investigated from the aspects of root morphology, physiology, and metabolism in this study. The results revealed that changes in root morphology and enzyme activity were affected by soil habitat. Total root length (TRL), root volume (RV) and root surface area (RSA) were higher in GS than in AS. The levels of proline (Pro), glutathione (GSH), soluble sugar (SS), and lysine (Lys) were higher in GS than in AS. Untargeted LC–MS metabolomics indicates that root metabolites of both species differed among the two soil habitats. Root responses to different soil habitats mainly affected some metabolic pathways. A total of 780 metabolites were identified, common differential metabolites (DMs) in both species included amino acids, fatty acids, organic acids, carbohydrates, benzene and derivatives, and flavonoids, which were mainly involved in carbohydrate metabolism, amino acid metabolism, flavonoid biosynthesis and fatty acid metabolism, and their abundance varied among different habitats and species. Some key DMs were significantly related to root morphology and enzyme activity, and indole, malonate, quercetin, uridine, tetrahydroharmine, and gluconolactone were important metabolites associated with root growth. Therefore, the response changes in root growth and metabolite of ephemeral plants in response to soil habitats reflect their ecological adaptation, and lay a foundation for the exploitation of plant resources in various habitats.

Unveiling the potential of nanobubbles in water: Impacts on tomato's early growth and soil properties

Nanobubbles (NBs) in water have been proven to improve plant growth and seed germination, potentially reducing both water and fertilizer consumption. To unravel the promotion mechanism of NBs on plant growth, this study investigated the characteristics of NBs in tap water and their impacts on tomato's early growth, soil chemical properties, enzymatic activity and electrochemical properties of plant roots. Oxygen NBs (ONBs) were found to increase the seed germination by 10 % and plant growth by 30 %–50 % (e.g., stem and diameter), whereas nitrogen NBs (NNBs) only had a significant promotion (7 %–34 %) on plant height. Additionally, compared to control group, irrigation with ONBs increased the peroxidase activities by 500 %–1000 % in tomato leaves, which may increase the expression of genes for peroxidase and promote cell proliferation and plant growth. Moreover, electrical impedance spectroscopy (EIS) revealed that the ONBs could reduce the interfacial impedance due to the increased active surface area and electrical conductivity of root.

Effects of Root Growth of Deep and Shallow Rooting Rice Cultivars in Compacted Paddy Soils on Subsequent Rice Growth

Rice is often grown as multiple seasons in one year, alternating between flooded and upland systems. A major constraint, introduced from the flooded system, is a plough pan that may decrease rooting depth and productivity of follow-on upland rice. Roots penetrating the plough pan under flooded rice system can leave a legacy of weaker root growth pathways. Deeper rooting rice cultivars could have a bigger impact, but no direct evidence is available. To explore whether a deep rather than a shallow rooting rice cultivar grown in a flooded cropping cycle benefited deeper root growth of follow-on rice in an upland, reduced tillage cropping cycle, a simulated flooded paddy in greenhouse was planted with deep (Black Gora) and shallow (IR64) rooting cultivars and a plant-free control. Artificial plough pans were made in between the topsoil and subsoil to form different treatments with no plough pan (0.35 MPa), soft plough pan (1.03 MPa) and hard plough pan (1.70 MPa). After harvest of this ‘first season’ rice, the soil was drained and undisturbed to simulate zero-tillage upland and planted rice cultivar BRRI Dhan 28. The overall root length density (RLD), root surface area, the numbers of root tips and branching of BRRI Dhan 28 did not vary between plough pan and no plough pan treatments. Compared with the shallow rooting rice genotype, the deep rooting rice genotype as ‘first season’ crop produced 19% greater RLD, 34% greater surface area and 29% more branching of BRRI Dhan 28 in the subsoil. In the topsoil, however, BRRI Dhan 28 had 28% greater RLD, 35% greater surface area and 43% more branching for the shallow rather than deep rooting genotype planted in the ‘first season’. The results suggested that rice cultivar selection for a paddy cycle affects root growth of a follow-on rice crop grown under no-till, with benefits to subsoil access from deep rooting cultivars and topsoil proliferation for shallow rooting cultivars.

The effect of exogenous melatonin on root growth and lifespan and seed cotton yield under drought stress

Drought stress is the major environmental factor that inhibits the growth and reduces the yield of cotton (Gossypium hirsutum L.). The exogenous application of melatonin has been shown to alleviate drought stress damage, but it is unclear whether melatonin mediates the alleviation by preventing the drought-induced inhibition of root growth. To address this gap, we subjected cotton plants grown in RhizoPotsto treatments of thorough watering, drought stress treatment, and drought stress supplemented with exogenous melatonin. Melatonin promoted the aboveground growth compared with the non-melatonin treatment under drought stress, and increased the plant height, stem diameter, leaf area, SPAD value, and net photosynthetic rate. The application of melatonin significantly prevented the drought-induced yield losses by increasing the boll weight. The drought stress+melatonin treatment significantly increased the root length, root surface area, root volume, and specific root length by 18.36%, 25.46%, 26.07%, and 18.53%, respectively, compared with the drought stress treatment. Under drought stress, melatonin increased the root length by increasing its maximum and average rates of accumulation and increased the taproot diameter by increasing its maximum and average rates of accumulation. The drought stress+melatonin treatment significantly increased the lifespan of lateral roots and root hairs compared with the drought stress treatment. In conclusion, this study indicated that exogenous melatonin could improve the drought resistance and yield of cotton by promoting root growth and delaying root senescence.

Tolerance of cultivars and clonal selections of peach rootstocks to excess aluminum

Forms of aluminum (Al) present in the solution of tropical and subtropical soils can cause toxicity in rootstocks and peach cultivars, impairing growth and productivity. This can be minimized by growing Al-tolerant rootstocks and cultivars. However, this is not sufficiently known, especially because plant breeding programs do not always consider tolerance as a selection variable for genetic materials. The study aimed to (a) select cultivars and clonal selections of Al-tolerant peach rootstocks, (b) identify variables that confer Al tolerance for use in genetic improvement programs, and (c) propose critical levels (NC) and ranges of toxicity (TF) of Al in relation to morphological variables of the root system. The experimental design was completely randomized, comprising a factorial of 13 (cultivars and clonal selections) x 2 (with and without Al) with three replications. Own-rooted ‘BRS Mandinho’ peach seedlings (without rootstock) and grafted seedlings of ‘BRS Mandinho’ on different cultivars and clonal rootstock selections were cultivated in a hydroponic system, composing two levels for the Al factor (absence and presence at 100 mg L−1). The morphological variables of the canopy and root system, Al accumulation in tissues, translocation factor, and the critical level (NC) and toxicity range (TF) of Al in the roots were evaluated. Rootstocks FB-SM-09-43, JB-ESM-09-13, SAS-SAU-09-71, SS-CHI-09-40, ‘Sharpe’ and VEH-GRA-09-55 were tolerant at high Al concentrations. The NC of Al in the roots in relation to the root surface area of peach rootstocks was 1400 mg Al kg−1, and the FT was between 1200 and 1500 mg Al kg−1.

Examining the role of AMF-Biochar in the regulation of spinach growth attributes, nutrients concentrations, and antioxidant enzymes in mitigating drought stress

Drought stress is one of the serious threats to crop production. It causes significant deterioration of crop growth and yield by inducing oxidative stress. The biochar and arbuscular mycorrhizae fungi (AMF) can be an effective technique to overcome drought stress. Activated carbon biochar (BC) has the potential to improve soil water holding capacity while AMF inoculation can increase root surface area for better uptake of water. However, their combined application as an amendment against drought still needs scientific justification. That's why the current study was conducted using a combination of AMF and BC on spinach under no drought stress and drought stress. The treatments included i.e., 0, 0.25%, and 0.50%AMF-BC. The experiment was replicated thre times using completely randomized design (CRD). Results showed that 0.5%AMF-BC increase spinach shoot fresh weight (20.34%), shoot dry weight (21.23%), shoot length (3.37%), root fresh weight (16.10%), root dry weight (14.51%), and root length (38.03%) over control under drought stress. The 0.50%AMF-BC increased chlorophyll a (15.33%), chlorophyll b (30.17%), total chlorophyll (18.85%), photosynthetic rate (35.59%), transpiration rate (26.53%), stomatal conductance (13.97%) and internal CO2 concentration (37.15%) compared to control under drought stress. The improvement in N, P, and K concentration in root and shoot verified the efficacious functioning of 0.50%AMF-BC compared to control under drought stress. In conclusion, 0.50%AMF-BC is recommended for the mitigation of drought stress in spinach.