Effects of Salt Stress on Physiological and Agronomic Traits of Rice Genotypes with Contrasting Salt Tolerance.

Salinity is one of the major constraints to crop production. Rice is a main staple food and is highly sensitive to salinity. This study aimed to elucidate the effects of salt stress on physiological and agronomic traits of rice genotypes with contrasting salt tolerance. Six contrasting rice genotypes (DJWJ, JFX, NSIC, HKN, XD2H and HHZ), including three salt-tolerant and three salt-sensitive rice genotypes, were grown under two different salt concentrations (0 and 100 mmol L-1 NaCl solution). The results showed that growth, physiological and yield-related traits of both salt-sensitive and salt-tolerant rice were significantly affected by salt stress. In general, plant height, tiller number, dry weight and relative growth rate showed 15.7%, 11.2%, 25.2% and 24.6% more reduction in salt-sensitive rice than in salt-tolerant rice, respectively. On the contrary, antioxidant enzyme activity (superoxide dismutase, peroxidase, catalase), osmotic adjustment substances (proline, soluble protein, malondialdehyde (MDA)) and Na+ content were significantly increased under salt stress, and the increase was far higher in salt-tolerant rice except for MDA. Furthermore, grain yield and yield components significantly decreased under salt stress. Overall, the salt-sensitive rice genotypes showed a 15.3% greater reduction in grain yield, 5.1% reduction in spikelets per panicle, 7.4% reduction in grain-filling percentage and 6.1% reduction in grain weight compared to salt-tolerant genotypes under salt stress. However, a modest gap showed a decline in panicles (22.2% vs. 22.8%) and total spikelets (45.4% vs. 42.1%) between salt-sensitive and salt-tolerant rice under salinity conditions. This study revealed that the yield advantage of salt-tolerant rice was partially caused by more biomass accumulation, growth rate, strong antioxidant capacity and osmotic adjustment ability under salt stress, which contributed to more spikelets per panicle, high grain-filling percentage and grain weight. The results of this study could be helpful in understanding the physiological mechanism of contrasting rice genotypes' responses to salt stress and to the breeding of salt-tolerant rice.

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.

Improving productivity of Sesbania pea in saline soils by enhancing antioxidant capacity with optimum application of nitrogen and phosphate combination.

Salinity stress is one of the major constraints to plant growth and crop production. Optimum fertilizer management is essential for promoting crop growth and productivity in saline soils. A field experiment was conducted to study the effects of nitrogen and phosphate combination on sesbania pea (Sesbania cannabina (Retz.) Poir.) growth and associated physiology in saline soils. Three N rates (N1: 240 kg·ha-1, N2: 360 kg·ha-1, N3: 480 kg·ha-1) and two P rates (P1: 120 kg·ha-1, P2:180 kg·ha-1) were arranged in this study using a RCBD with 3 replicates. The application of N and P fertilizers significantly improved plant growth and associated physiological traits of sesbania pea. Plant height (P=0.0001), fresh biomass weight (P=0.0006), dry biomass weight (P=0.0006), relative growth rate (RGR) (P=0.005), chlorophyll (P=0.002), peroxidase (POD) (P=0.0003), catalase (CAT) (P=0.0001), superoxide dismutase (SOD) (P=0.0001) and soluble protein (P=0.0053) were significantly increased, and the maximum values were consistently produced under N2P2 combination at each growth stage. On the contrary, malondialdehyde (MDA) was prominently decreased by N and P fertilizer application (P=0.0029), and the lowest values were all produced under N2P2 combination. The highest values of plant height, fresh biomass weight and dry biomass weight were recorded on the 163rd day after seeding (DAS). The highest RGR and MDA content were determined on the 141st DAS. The highest chlorophyll content, CAT and SOD activity, and soluble protein content were recorded on the 110th DAS, and the highest POD activity was at 47 DAS. This study suggested that the optimum N and P fertilizer combination was N2P2 (360 kg·hm-2 N + 180 kg·hm-2 P), which was superior in promoting growth and biomass yield with enhanced antioxidant capacity of sesbania pea in saline soils.

Gibberellic acid and nitrogen efficiently protect early seedlings growth stage from salt stress damage in Sorghum.

Salinity one of environmental factor that limits the growth and productivity of crops. This research was done to investigate whether GA3 (0, 144.3, 288.7 and 577.5 µM) and nitrogen fertilizer (0, 90 and 135 kg N ha-1) could mitigate the negative impacts of NaCl (0, 100, and 200 mM NaCl) on emergence percentage, seedling growth and some biochemical parameters. The results showed that high salinity level decreased emergence percentage, seedling growth, relative water content, chlorophyll content (SPAD reading), catalase (CAT) and peroxide (POD), but increased soluble protein content, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content. The SOD activity was decreased by nitrogen. However, the other measurements were increased by nitrogen. The interactive impact between nitrogen and salinity was significant in most parameters except EP, CAT and POD. The seedling length, dry weight, fresh weight, emergence percentage, POD, soluble protein and chlorophyll content were significantly affected by the interaction between GA3 and salinity. The GA3 and nitrogen application was successful mitigating the adverse effects of salinity. The level of 144.3 and 288.7 µm GA3 and the rate of 90 and 135 kg N ha-1 were most effective on many of the attributes studied. Our study suggested that GA3 and nitrogen could efficiently protect early seedlings growth from salinity damage.