Hydrogen Sulfide and Silicon Together Alleviate Chromium (VI) Toxicity by Modulating Morpho-Physiological and Key Antioxidant Defense Systems in Chickpea (Cicer arietinum L.) Varieties

Extensive use of chromium (Cr) in anthropogenic activities leads to Cr toxicity in plants causing serious threat to the environment. Cr toxicity impairs plant growth, development, and metabolism. In the present study, we explored the effect of NaHS [a hydrogen sulfide; (H2S), donor] and silicon (Si), alone or in combination, on two chickpea (Cicer arietinum) varieties (Pusa 2085 and Pusa Green 112), in pot conditions under Cr stress. Cr stress increased accumulation of Cr reduction of the plasma membrane (PM) H+-ATPase activity and decreased in photosynthetic pigments, essential minerals, relative water contents (RWC), and enzymatic and non-enzymatic antioxidants in both the varieties. Exogenous application of NaHS and Si on plants exposed to Cr stress mitigated the effect of Cr and enhanced the physiological and biochemical parameters by reducing Cr accumulation and oxidative stress in roots and leaves. The interactive effects of NaHS and Si showed a highly significant and positive correlation with PM H+-ATPase activity, photosynthetic pigments, essential minerals, RWC, proline content, and enzymatic antioxidant activities (catalase, peroxidase, ascorbate peroxidase, dehydroascorbate reductase, superoxide dismutase, and monodehydroascorbate reductase). A similar trend was observed for non-enzymatic antioxidant activities (ascorbic acid, glutathione, oxidized glutathione, and dehydroascorbic acid level) in leaves while oxidative damage in roots and leaves showed a negative correlation. Exogenous application of NaHS + Si could enhance Cr stress tolerance in chickpea and field studies are warranted for assessing crop yield under Cr-affected area

Zinc Absorption through Leaves and Subsequent Translocation to the Grains of Bread Wheat after Foliar Spray

Agronomic biofortification could possibly be a promising strategy to overcome zinc (Zn) deficiency in wheat; however, the cultivar’s response to foliar applications is enigmatic when it comes to the relative efficiency of Zn absorption and accumulation. To decipher that enigmatic response, this study was designed with the objectives (i) to track the amount of Zn absorbed through leaves after foliar application, (ii) to calculate the amount of the absorbed Zn actually translocated and stored in the grains, and (iii) to calculate the relative efficiency of the high yielding cultivars in terms of their Zn absorption and translocation. The results reveal that 0.90% of the zinc sprayed was absorbed through leaves, and 43% of the absorbed Zn was translocated to the grains. The cultivars significantly varied for their Zn absorption (0.71–1.07%) and subsequent translocation of the absorbed Zn (23–66%). Foliar zinc treatment also improved growth attributes such as leaf area, height, spikelet per spike, number of grains per spike, grain yield, leaf and grain Zn content, and grain protein content. These findings suggest a need for cautious parent selection in devising the breeding strategies intended for biofortification

Effect of Calcium and Potassium on Antioxidant System of <em>Vicia faba</em> L. Under Cadmium Stress

Cadmium (Cd) in soil poses a major threat to plant growth and productivity. In the present experiment, we studied the effect of calcium (Ca<sup>2+</sup>) and/or potassium (K<sup>+</sup>) on the antioxidant system, accumulation of proline (Pro), malondialdehyde (MDA), and content of photosynthetic pigments, cadmium (Cd) and nutrients, <em>i.e.</em>, Ca<sup>2+</sup> and K<sup>+</sup> in leaf of <em>Vicia faba </em>L. (cv. TARA) under Cd stress. Plants grown in the presence of Cd exhibited reduced growth traits [root length (RL) plant<sup>−1</sup>, shoot length (SL) plant<sup>−1</sup>, root fresh weight (RFW) plant<sup>−1</sup>, shoot fresh weight (SFW) plant<sup>−1</sup>, root dry weight (RDW) plant<sup>−1</sup> and shoot dry weight (SDW) plant<sup>−1</sup>] and concentration of Ca<sup>2+</sup>, K<sup>+</sup>, Chlorophyll (Chl) <em>a</em> and Chl <em>b </em>content, except content of MDA, Cd and (Pro). The antioxidant enzymes [peroxidase (POD) and superoxide dismutase (SOD)] slightly increased as compared to control under Cd stress. However, a significant improvement was observed in all growth traits and content of Ca<sup>2+</sup>, K<sup>+</sup>, Chl <em>a</em>, Chl <em>b </em>,Pro and activity of antioxidant enzymes catalase (CAT), POD and SOD in plants subjected to Ca<sup>2+</sup> and/or K<sup>+</sup>. The maximum alleviating effect was recorded in the plants grown in medium containing Ca<sup>2+</sup> and K<sup>+</sup> together. This study indicates that the application of Ca<sup>2+</sup> and/or K<sup>+</sup> had a significant and synergistic effect on plant growth. Also, application of Ca<sup>2+</sup> and/or K<sup>+</sup> was highly effective against the toxicity of Cd by improving activity of antioxidant enzymes and solute that led to the enhanced plant growth of faba bean plants. <strong> </strong> <strong> </strong&gt

Potassium and Humic Acid Synergistically Increase Salt Tolerance and Nutrient Uptake in Contrasting Wheat Genotypes through Ionic Homeostasis and Activation of Antioxidant Enzymes

Salinity limits the growth and nutrient uptake in crop species. Studies show that both potassium (K) and humic acid (HA) improved plant tolerance to salinity. However, the interactive effect of K and HA on plant tolerance to salinity stress remains unknown. This pot study examined the effect of application of K (0, 5 or 10 mM) and HA (0 or 2 g kg−1), alone or in combination, on the growth and physiology under salinity (100 mM NaCl) in two wheat genotypes (SARC 1, salt tolerant; and SARC 5, salt sensitive). The results revealed that salt stress reduced shoot biomass by 35% and 49% in SARC 1 and SARC 5, respectively. Salinity induced overproduction of H2O2 and lipid peroxidation in both genotypes, but the decline in pigments and stomatal conductance was more profound in SARC 5 than in SARC 1. Combined application of 10 mM K and HA was most effective in alleviating salt stress with improved plant biomass by 47% and 43% in SARC 1 and SARC 5, respectively. Combined application of 10 mM K and HA mitigated salt and induced oxidative stress with the activities of APX, CAT, POD and SOD increased by up to 2.8 folds in SARC 1, and by upto 2.5 folds in SARC 5, respectively. Root and shoot Na contents were increased, while K, Fe and Zn contents were decreased under saline conditions. HA combined with K decreased Na and increased K, Fe and Zn contents in both genotypes. Combined application of 10 mM K and HA was more promising for increasing wheat salt tolerance and nutrient uptake and genotype SARC 1 performed better than SARC 5 for cultivation on saline soils

Inoculation with Arbuscular Mycorrhizal Fungi Alleviates the Adverse Effects of High Temperature in Soybean

High temperature is foremost abiotic stress and there are inadequate studies explicating its impact on soybean. In this study, a pot experiment was done in a greenhouse maintained at a day/night temperature of 42/28 °C with a mean temperature of 35 °C to examine the effects of high temperature in soybean plants inoculated with and without arbuscular mycorrhizal fungi (AMF).Various parameters were taken in soybean plants treated with AMF (+) and AMF (−) such as growth analysis, chlorophyll content, canopy temperature, number of stomata, gas exchange, chlorophyll fluorescence, seed yield, and its attributes. It was observed that growth parameters like leaf area, stem height, root length, shoot and root dry biomass were increased in AMF (+) as compared to AMF (−) plants. Chlorophyll content, the number of stomata, photosynthesis rate, stomatal conductance, transpiration rate, and water use efficiency increased in AMF (+) as compared to AMF (−) plants. Chlorophyll fluorescence parameters such as Fv/Fm, Fv/Fo, PhiPSII, fluorescence area, performance index, photochemical quenching, linear electron transport rate, and active reaction centres density of PSII were also found to be enhanced in AMF (+) plants. However, canopy temperature, intercellular CO2, Fo/Fm, and non-photochemical quenching were higher in AMF (−) as compared to inoculated plants. An increase in growth and photosynthesis ultimately enhanced the seed yield and its attributes in AMF (+) as compared to AMF (−). Thus, AMF (+) plants have shown much better plant growth, photosynthesis parameters, and seed yield as compared to AMF (−) plants under high temperature. Thus, it is concluded that heat stress-induced damage to the structure and function of the photosynthetic apparatus was alleviated by AMF inoculum. Therefore, AMF can be used as a biofertilizer in alleviating the adverse effects of heat stress in soybean

Combined Effect of Salicylic Acid and Proline Mitigates Drought Stress in Rice (Oryza sativa L.) through the Modulation of Physiological Attributes and Antioxidant Enzymes

Salicylic acid (SA) and proline exhibit protective effects against a wide range of stresses. However, the combined impact of SA and proline on rice under drought stress is still unknown. Therefore, we investigated the protective roles of SA and/or proline in conferring drought tolerance in rice. There were eight treatments comprising the control (T1; 95-100% FC), 1.5 mM SA (T2), 2 mM proline (T3), 0.75 mM SA + 1 mM proline (T4), 45-50% FC (T5, drought stress), T5 + 1.5 mM SA (T6), T5 + 2 mM proline (T7), and T5 + 0.75 mM SA + 1 mM proline (T8), and two rice varieties: BRRI dhan66 and BRRI dhan75. Drought stress significantly decreased the plant growth, biomass, yield attributes, photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), photosynthetic pigments (chlorophyll and carotenoids content), relative water content (RWC), membrane stability index (MSI), soluble sugar and starch content, and uptake of N, P and K+ in roots and shoots. Drought-induced oxidative stress in the form of increased hydrogen peroxide (H2O2) production and lipid peroxidation (MDA) was observed. The combined application of SA (0.75 mM) + proline (1 mM) was found to be more effective than the single application of either for drought stress mitigation in rice. A combined dose of SA + proline alleviated oxidative stress through boosting antioxidant enzymatic activity in contrast to their separate application. The application of SA + proline also enhanced proline, soluble sugar and starch content, which resulted in the amelioration of osmotic stress. Consequently, the combined application of SA and proline significantly increased the gas exchange characteristics, photosynthetic pigments, RWC, MSI, nutrient uptake, plant growth, biomass and yield of rice. Therefore, the combined application of SA and proline alleviated the detrimental impacts of drought stress more pronouncedly than their separate application did by increasing osmoprotectants, improving nutrient transport, up-regulating antioxidant enzyme activity and inhibiting oxidative stress

Mitigation of chromium-induced phytotoxicity in 28-homobrassinolide treated Trigonella corniculata L. by modulation of oxidative biomarkers and antioxidant system

Chromium (Cr) is one of the toxic heavy metals that disturbs growth and physiological properties of plants. During the current study, Trigonella corniculata L. (Fenugreek) was exposed to different levels of Cr in potted soil. Chromium toxicity reduced fiber, ash, moisture, carbohydrate, protein, fats, and flavonoid content of T. corniculata. Considering the stress relieving effect of 28-homobrassinolide (28-HBR), seeds of T. corniculata were primed with different concentration of 28-HBR i.e., 0, 5, 10, and 20 µmol L−1. Application of 28-HBR reversed the toxic effect of Cr through improvement in activity of antioxidant enzymes like superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT). Conclusively, 10 µmol L−1 28-HBR increased Cr tolerance in T. corniculata seedlings due to reduction in oxidative stress markers. It is further proposed that 28-HBR is an effective stress ameliorant to relive plants from various abiotic stresse