Exogenous glutathione protected wheat seedling from high temperature and water deficit damages

High temperatures (HT) and drought are two major factors restricting wheat growth in the early growth stages. This study investigated the role of glutathione (GSH) amendment (0.0, 0.5, 1.0, and 2.0 mM) to soil in mitigating the adverse effect of HT (33 °C, with 25 °C as a control), water regimes (60% of field capacity and control), and their combinations. HT decreased the length, project area, surface area, volume, and forks of the root, while drought had the reverse effect. Shoot length, leaf area, leaf relative water content, and shoot and root dry matter were significantly decreased by HT and drought, and their combined impact was more noticeable. GSH significantly promoted the root system, shoot growth, and leaf relative water content. The combined treatment reduced chlorophyll a, chlorophyll b, and total chlorophyll. However, 0.5 mM GSH raised chlorophyll a, chlorophyll b, and total chlorophyll by 28.6%, 41.4%, and 32.5%, respectively, relative to 0.0 mM GSH. At combined treatment, 0.5 mM GSH decreased malondialdehyde (MDA) by 29.5% and increased soluble protein content by 24.1%. GSH meaningfully enhanced the activity of superoxide dismutase, catalase, and ascorbate peroxide in different treatments. This study suggested that GSH could protect wheat seedlings from the adverse effects of HT and/or drought stresses.

The role of melatonin in plant growth and metabolism, and its interplay with nitric oxide and auxin in plants under different types of abiotic stress

Melatonin is a pleiotropic signaling molecule that reduces the adverse effects of abiotic stresses, and enhances the growth and physiological function of many plant species. Several recent studies have demonstrated the pivotal role of melatonin in plant functions, specifically its regulation of crop growth and yield. However, a comprehensive understanding of melatonin, which regulates crop growth and yield under abiotic stress conditions, is not yet available. This review focuses on the progress of research on the biosynthesis, distribution, and metabolism of melatonin, and its multiple complex functions in plants and its role in the mechanisms of metabolism regulation in plants grown under abiotic stresses. In this review, we focused on the pivotal role of melatonin in the enhancement of plant growth and regulation of crop yield, and elucidated its interactions with nitric oxide (NO) and auxin (IAA, indole-3-acetic acid) when plants are grown under various abiotic stresses. The present review revealed that the endogenousapplication of melatonin to plants, and its interactions with NO and IAA, enhanced plant growth and yield under various abiotic stresses. The interaction of melatonin with NO regulated plant morphophysiological and biochemical activities, mediated by the G protein-coupled receptor and synthesis genes. The interaction of melatonin with IAA enhanced plant growth and physiological function by increasing the levels of IAA, synthesis, and polar transport. Our aim was to provide a comprehensive review of the performance of melatonin under various abiotic stresses, and, therefore, further explicate the mechanisms that plant hormones use to regulate plant growth and yield under abiotic stresses.

Effects of jasmonic acid in foliar spray and an humic acid amendment to saline soils on forage sorghum plants' growth and antioxidant defense system

Salinity is one of the primary abiotic stresses that cause negative physiological and biochemical changes due to the oxidative stress caused by the generation of reactive oxygen species (ROS). The effect of jasmonic acid (JA) as foliar spray and humic acid (HA) as soil amendment on the growth and biochemical attributes of forage sorghum plants exposed to salinity stress was investigated. Soil treated with NaCl at levels of 0, 2, and 4 g NaCl kg^-1 dry soil (designated as S0, S1, and S2) and soil amendment with humic acid at 0, 3, and 6 g HA kg^-1 dry soil (designated as HA0, HA1, and HA2). The plants were sprayed with three JA levels, including 0, 5, and 10 mM JA. Salinity stress increased carotenoid and soluble protein content, superoxide dismutase (SOD) activity, and malondialdehyde (MDA) content. In contrast, salinity stress reduced plant height, leaf area, relative growth rate, proline content, and the activity of peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX). At the S2 salinity level, HA2 rate increased plant high by 9.7%, relative growth rate by 70.8% and CAT by 45.5, while HA1 increased leaf area by 12.5%, chlorophyll content by 22.3%, carotenoid content by 38.1%, SOD activity by 20.9%, MDA content by 18.0%, POD activity by 24.6% and APX value by 21.7%. At the S2 salinity level, the highest plant height, chlorophyll content, soluble protein content and APX value were recorded at 5 mM JA, while the highest leaf area, the content of carotenoid, proline, and MDA, and the activity of POD and CAT were achieved at 10 mM JA. Generally, 10 mM JA and 3 g HA kg^-1 dry soil produced the best positive effects on forage sorghum plants physiological responses. Our study suggested that jasmonic acid and humic acid at appropriate rates can successfully mitigate the adverse effects of salinity stress on forage sorghum.