Protective effect of jasmonic acid and potassium against cadmium stress in peas (Pisum sativum L.).

A combination of mineral nutrients and plant growth regulators should be assessed to improve crop performance under various abiotic stresses. There is a need to include plant growth regulators in fertilization regime of various crops along with essential mineral nutrients, especially when they are irrigated with polluted water with higher levels of heavy metals. The performance of pea was evaluated under cadmium (Cd) stress coupled with potassium (K) and jasmonic acid (JA) supplementation. The Cd stress (50 µM) was applied to soil (sandy loam) grown pea plants as basal dose after a month of sowing. The control and stressed plants were then supplemented with K (5 M), JA (0.5 mM) and their collective application along with control as distilled water. Cd stress showed a marked reduction in growth pattern, however, the collective supplementation sufficiently improved the growth pattern of stressed peas plants as evidenced by improvement in shoot length (cm), root length (cm), number of leaves per plant, leaf area (cm2), plant fresh and dry weight (gm). Potassium application under Cd stress significantly enhanced internodal distance (cm) while the number of seeds per pod and relative water contents remained nonsignificant. The applied treatment (JA + K) under Cd stress prominently improved enzymatic activities, which were measured as nitrate reductase activity (NRA), nitrite reductase activity (NiRA), superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT). Cd stress impacted the biochemical profile by enhancing antioxidant capacity (AC), antioxidant activity (AA), total phenols (TP), while reducing total soluble protein (TSP), chlorophyll 'a', chlorophyll 'b' and carotenoids. The combined application of JA and K under Cd stress enhanced AC, AA, TP, Chl a and b, TSP and carotenoids. The results indicate that foliar application of JA and K efficiently negated the harmful effects of Cd stress on peas.

Foliar application of zinc improves morpho-physiological and antioxidant defense mechanisms, and agronomic grain biofortification of wheat (Triticum aestivum L.) under water stress.

Agronomic biofortification with zinc (Zn) may be engaged to improve the nutritious value of food crops along-with tolerance to water deficit conditions. The Zn may increase plant resistance to water stress by boosting physiological and enzymatic antioxidants defense mechanisms. Major objective of this study was to investigate the effect of foliar applied Zn on grain zin biofortification and drought tolerance in wheat. Treatments include application of Zinc at terminal growth phases (BBCH growth stage 49 and BBCH growth stage 65) with five levels: 0 (control-ck), water spray, 5, 10 and 15 mM under two levels of water regimes; well-watered (where 80% water holding capacity (WHC) was maintained in the soil) and water stress, (where 40% WHC was maintained in the soil). Results revealed that water stress significantly reduced relative water contents, gas exchange attributes, plant height, yield and yield related attributes of wheat. In contrast, hydrogen peroxide, free proline levels, activities of malondialdehyde, and concentration of soluble protein were markedly increased under water stress condition. Application of various levels of Zn significantly improved the CAT, SOD, POD and ASP activities at 40% WHC compared with control treatment. Foliarly applied 10 and 15 mM Zn predominantly reduced the damaging impact of water stress by improving the plant status in the form of plant height, RWC and gas exchange attributes. Likewise, wheat plant treated with 10 mM Zn under water stress condition increased the grain yield by improving number of grains per spike, 100 grain weight and biological yield compared with control. Moreover, increasing Zn levels also increased Zn concentration in grains and leaves. Overall, this study suggests that optimum level of Zn (10 mM) might be promising for alleviating the adverse impacts of water stress and enhance the grain biofortification in wheat.

Morpho-physiological and biochemical attributes of Chili (Capsicum annum L.) genotypes grown under varying salinity levels.

Climate change is causing soil salinization, resulting in huge crop losses throughout the world. Multiple physiological and biochemical pathways determine the ability of plants to tolerate salt stress. Chili (Capsicum annum L.) is a salt-susceptible crop; therefore, its growth and yield is negatively impacted by salinity. Irreversible damage at cell level and photo inhibition due to high production of reactive oxygen species (ROS) and less CO2 availability caused by water stress is directly linked with salinity. A pot experiment was conducted to determine the impact of five NaCl salinity levels, i.e., 0,1.5, 3.0, 5.0 and 7.0 dS m-1 on growth, biochemical attributes and yield of two chili genotypes ('Plahi' and 'A-120'). Salinity stress significantly reduced fresh and dry weight, relative water contents, water use efficiency, leaf osmotic potential, glycine betaine (GB) contents, photosynthetic rate (A), transpiration rate (E), stomatal conductance (Ci), and chlorophyll contents of tested genotypes. Salinity stress significantly enhanced malondialdehyde (MDA) contents and activities of the enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). In addition, increasing salinity levels significantly reduced the tissue phosphorus and potassium concentrations, while enhanced the tissue sodium and chloride concentrations. Genotype 'Plahi' had better growth and biochemical attributes compared to 'A-120'. Therefore, 'Plahi' is recommended for saline areas to improve chili production.

Combined application of zinc and silicon alleviates terminal drought stress in wheat by triggering morpho-physiological and antioxidants defense mechanisms.

Wheat is an important global staple food crop; however, its productivity is severely hampered by changing climate. Erratic rain patterns cause terminal drought stress, which affect reproductive development and crop yield. This study investigates the potential and zinc (Zn) and silicon (Si) to ameliorate terminal drought stress in wheat and associated mechanisms. Two different drought stress levels, i.e., control [80% water holding capacity (WHC) was maintained] and terminal drought stress (40% WHC maintained from BBCH growth stage 49 to 83) combined with five foliar-applied Zn-Si combinations (i.e., control, water spray, 4 mM Zn, 40 mM Si, 4 mM Zn + 40 mM Si applied 7 days after the initiation of drought stress). Results revealed that application of Zn and Si improved chlorophyll and relative water contents under well-watered conditions and terminal drought stress. Foliar application of Si and Zn had significant effect on antioxidant defense mechanism, proline and soluble protein, which showed that application of Si and Zn ameliorated the effects of terminal drought stress mainly by regulating antioxidant defense mechanism, and production of proline and soluble proteins. Combined application of Zn and Si resulted in the highest improvement in growth and antioxidant defense. The application of Zn and Si improved yield and related traits, both under well-watered conditions and terminal drought stress. The highest yield and related traits were recorded for combined application of Zn and Si. For grain and biological yield differences among sole and combined Zn-Si application were statistically non-significant (p>0.05). In conclusion, combined application of Zn-Si ameliorated the adverse effects of terminal drought stress by improving yield through regulating antioxidant mechanism and production of proline and soluble proteins. Results provide valuable insights for further cross talk between Zn-Si regulatory pathways to enhance grain biofortification.