Showing papers on "Plant physiology published in 2022"

Selenium Supplementation and Crop Plant Tolerance to Metal/Metalloid Toxicity

Abstract: Selenium (Se) supplementation can restrict metal uptake by roots and translocation to shoots, which is one of the vital stress tolerance mechanisms. Selenium can also enhance cellular functions like membrane stability, mineral nutrition homeostasis, antioxidant response, photosynthesis, and thus improve plant growth and development under metal/metalloid stress. Metal/metalloid toxicity decreases crop productivity and uptake of metal/metalloid through food chain causes health hazards. Selenium has been recognized as an element essential for the functioning of the human physiology and is a beneficial element for plants. Low concentrations of Se can mitigate metal/metalloid toxicity in plants and improve tolerance in various ways. Selenium stimulates the biosynthesis of hormones for remodeling the root architecture that decreases metal uptake. Growth enhancing function of Se has been reported in a number of studies, which is the outcome of improvement of various physiological features. Photosynthesis has been improved by Se supplementation under metal/metalloid stress due to the prevention of pigment destruction, sustained enzymatic activity, improved stomatal function, and photosystem activity. By modulating the antioxidant defense system Se mitigates oxidative stress. Selenium improves the yield and quality of plants. However, excessive concentration of Se exerts toxic effects on plants. This review presents the role of Se for improving plant tolerance to metal/metalloid stress.

Effect of silicon on morpho-physiological attributes, yield and cadmium accumulation in two maize genotypes with contrasting root system size and health risk assessment

Abstract: Abstract Background and aims Cadmium (Cd) contamination is a serious threat to plants and humans. Silicon (Si) was reported to have some alleviative effects on Cd stress in plants. However, whether Si alleviates Cd toxicity in maize genotypes with contrasting root system size are unknown. Methods Effects of Si application (200 mg kg −1 soil) on shoot and root growth, Cd uptake and transportation under Cd stress (20 mg kg −1 soil) were assessed at the silking and maturity stages of maize genotypes Zhongke11 (deep-rooted) and Shengrui999 (shallow-rooted) in a pot experiment. Results Application of Si significantly increased root dry weight, plant height and root length. Root volume and average root diameter were significantly positively correlated with root Cd concentration, bioaccumulation and translocation factor, respectively, of two maize genotypes at the silking stage. Addition of Si significantly increased Cd concentration, content, bioconcentration and translocation factor in roots of Zhongke11, but reduced the values of these parameters in Shengrui9999 at both growth stages. Grain Cd concentration in the combined Cd and Si treatment was decreased by 14.4% (Zhongke11) and 21.4% (Shengrui999) than that in Cd treatment. Grain yield was significantly negatively correlated with root Cd accumulation. Moreover, addition of Si significantly reduced Cd daily intake and health risk index in maize. Conclusions This study demonstrated that addition of Si reduced health risk by eliminating Cd accumulation in maize shoot and grain, and alleviated Cd stress with more profound effects in the shallow-rooted genotype Shengrui999.

Biochar and Selenium Nanoparticles Induce Water Transporter Genes for Sustaining Carbon Assimilation and Grain Production in Salt-Stressed Wheat

Abstract: Abstract In a controlled environment experiment, we studied how physiological changes in leaves during the vegetative phase regulate final grain yield of wheat crops in salt-affected soils. We also hypothesized that amendments such as biochar (SB) and selenium-chitosan nanoparticles (Se-NPs) can protect wheat plants from salt injury. 20-day-old wheat plants were submitted to 4-week salt stress (3000 ppm NaCl). Soybean straw biochar was mixed with soil media at planting and Se-NPs (30 ppm) was sprayed 5 days after the first salt stress treatment. At the end of 4-week Se-NPs treatment, one set of plants was harvested for studying leaf level physiological changes. The salt-stressed plants accumulated significantly high leaf Na + (~ 13-fold increase), which trigged oxidative and osmotic damage. This salt-induced cellular injury was evident from significantly high levels of lipid membrane peroxidation and inhibited photosynthesis. Our study suggested that leaf physiological impairment in wheat plants was translated into poor biomass production and grain yield loss at crop maturity. Compared with control, salt-stressed plants produced 43% lesser biomass during vegetative phase, and 62% lesser grain yield at maturity. Amendments such as SB and Se-NPs protected the plants from salt-induced cellular injury by restricting Na + transport toward leaf tissues. Plants treated with NaCl + SB + Se-NPs accumulated 50% less Na + concentrations in leaves compared with NaCl-treated plants. Our study also suggested that SB and Se-NPs can restore ionic homeostasis and carbon assimilation in salt-stressed wheat by upregulating key transporter genes in leaves.

Salicylic acid alleviates selenium stress and promotes selenium uptake of grapevine

Abstract: To determine suitable cultivation measures to enrich selenium (Se) and alleviate the Se stress in fruit trees, the effects of different exogenous salicylic acid (SA) concentrations (0, 50, 100, 150 and 200 mg/L) on the growth and Se uptake of grapevine under Se stress were studied. Under Se stress, SA increased the biomass of grapevine to some extent and had a linear relationship with both root and shoot biomass. The chlorophyll content, net photosynthetic rate, transpiration rate, stomatal conductance, and intercellular CO2 concentration of grapevine tended to increase when the concentration of SA was < 150 mg/L and decrease when the concentration of SA was > 150 mg/L. Different concentrations of SA enhanced the activity of superoxide dismutase, while reducing that of peroxidase. It had no significant effect on the catalase activity of grapevine. SA decreased the content of osmotically active substances in grapevine to some extent. SA also increased the contents of total Se, inorganic Se and organic Se in grapevine to some extent, and had a linear or quadratic polynomial relationship with the total Se contents in both roots and shoots. When the SA concentration was 250 mg/L, the total Se contents in the roots and shoots were the highest and increased by 10.41% and 58.46%, respectively, compared with the control. Therefore, exogenous SA could promote the growth and Se uptake of grapevine under Se stress, with 250 mg/L serving as the most effective concentration.

Effects of exogenous melatonin on plant growth, root hormones and photosynthetic characteristics of trifoliate orange subjected to salt stress

Abstract: Soil salinity has negative effects on crop growth and production, and melatonin (MT) plays an important role in regulating plant salt stress. However, it is not clear whether exogenous melatonin mitigates the negative effect on citrus plants subjected to salt stress. This study aimed to explore the response of exogenous melatonin (0, 50, 100, 150 µmol/L) on plant growth, root hormone levels and the photosynthetic system of trifoliate orange (Citrus (Poncirus) trifoliata L.) seedlings exposed to 0 or 150 mmol/L NaCl for 4 weeks. The 150 mmol/L NaCl treatment significantly increased root zeatin riboside, gibberellin and brassinolide levels, while dramatically reducing plant growth, root auxin levels, leaf photosynthesis and fluorescence indexes of seedlings. However, melatonin treatment partially ameliorated reductions in plant height and dry matter accumulation caused by salt stress. Melatonin (100 µmol/L) appears to interact with IAA but not the other hormones studied. Furthermore, the effects of NaCl stress on the net photosynthetic rate, stomatal conductance, maximum photochemical efficiency, PSII effective photon yield, photochemical quenching and other indicators of seedlings leaves were also partially alleviated and the damage of NaCl stress was also reduced when seedlings were treated with melatonin. This suggests that 100 µmol/L melatonin may be an effective treatment.

Identification and Characterization of Bacillus subtilis B9: A Diazotrophic Plant Growth-Promoting Endophytic Bacterium Isolated from Sugarcane Root

Abstract: Abstract Plant endophytic microorganisms, which can enhance plant growth and resistance to biotic and abiotic stresses, are untapped resources with large potential applications for crop production. However, the endophytic community is influenced by multiple factors, such as host genetics, the environment, and other microbes. Thus, it is important to characterize well-adapted endophytes from native crops. We isolated 43 endophytic bacteria from sugarcane cultivar Yunzhe-99-91. All these 43 isolates were examined in vitro for nitrogenase activity and the ability to dissolve phosphorus and produce siderophore. One of these strains, B9, identified as Bacillus subtilis and showed maximum plant growth promotion, was selected for detailed studies. B9 promoted the production of organic acids such as propionic acid, acetic acid, malic acid and citric acid, and the production of phytohormones, including indole-3-acetic acid, cytokinin, 6-benzyladenine, and zeatin. Moreover, B9 significantly promoted the growth of sugarcane plantlets and increased the content of nitrogen, phosphorus, and potassium in the seedlings by 29.26%, 50.78%, and 15.49%, respectively. The photosynthetic rate, root development, and chlorophyll content were also improved with varying degrees compared to the non-inoculated control. The cotyledon and hypocotyl of sugarcane gems germinated faster when co-cultured with the B9 strain compared with control group. Colonization assay showed that B9 was mainly colonized in the roots, followed by the stems and leaves. In conclusion, the positive interaction between endophytic strain B9 and sugarcane may provide long-lasting benefits and a direction for developing and utilizing B9 as a biofertilizer for sugarcane cultivation to decrease fertilizer application.

Microbe-Mediated Thermotolerance in Plants and Pertinent Mechanisms- A Meta-Analysis and Review

Abstract: Microbial symbionts can mediate plant stress responses by enhancing thermal tolerance, but less attention has been paid to measuring these effects across plant-microbe studies. We performed a meta-analysis of published studies as well as discussed with relevant literature to determine how the symbionts influence plant responses under non-stressed versus thermal-stressed conditions. As compared to non-inoculated plants, inoculated plants had significantly higher biomass and photosynthesis under heat stress conditions. A significantly decreased accumulation of malondialdehyde (MDA) and hydrogen peroxide (H2O2) indicated a lower oxidation level in the colonized plants, which was also correlated with the higher activity of catalase, peroxidase, glutathione reductase enzymes due to microbial colonization under heat stress. However, the activity of superoxide dismutase, ascorbate oxidase, ascorbate peroxidase, and proline were variable. Our meta-analysis revealed that microbial colonization influenced plant growth and physiology, but their effects were more noticeable when their host plants were exposed to high-temperature stress than when they grew under ambient temperature conditions. We discussed the mechanisms of microbial conferred plant thermotolerance, including at the molecular level based on the available literature. Further, we highlighted and proposed future directions toward exploring the effects of symbionts on the heat tolerances of plants for their implications in sustainable agricultural production.

Role of nanosilicab to boost the activities of metabolites in Triticum aestivum facing drought stress

Abstract: This study was designed to assess the effect of nanosilicab fertilizer on Triticum aestivum under drought stress. The plants were grown in pots having the soil incubated with SiO2 NPs, biofertilizer and nanosilicab. The experimental design was completely randomized design and drought stress was applied at stem elongation stage. Plants were maintained in the pots till the collection of yield. Nanosilicab enhanced the germination percentage, germination index, and germination vigor index by 23.07%, 14.49%, and 93.10% under control and 14.42%, 10.52%, and 46.15% under drought stress. In the pot experiment, the soil was treated with 150 mg/kg silicon dioxide nanoparticles (SiO2), 1% biofertilizer and, 1% nanosilicab before sowing. Nanosilicab increased shoot length and root length by 34.77%, and 16.88% under control and 30.58%, and 21.56% under stress conditions, respectively. It also increased photosynthetic pigments, osmolytes content, relative water content, membrane stability index, phenol, and flavonoid content. The increase in antioxidant activity was significant by the application of nanosilicab i.e. the augmentation in catalase, peroxidase, and superoxide dismutase was 68.65%, 83.69%, and 85.99%, respectively. It also increased indole acetic acid and cytokinin by 22.28% and 14.79% in comparison to control. The improvement in hundred-grain weight and grains per spike by the use of nanosilicab was 36.25%, and 38.76% under control, and 27.47%, and 22.59% under stress conditions. The positive effect of nanosilicab on the roots of the plants improved the growth of plants significantly and this fertilizer showed potential for application on crops.