Improvement in Physiobiochemical and Yield Characteristics of Pea Plants with Nano Silica and Melatonin under Salinity Stress Conditions

The effect of nano silica (50 mL L−1) and melatonin (75 µM) individually or in combination in foliar applications on the morphophysiological, biochemical and yield properties of pea plants under salinity stress conditions was evaluated. Salt stress caused a remarkable decrease in the growth and yield characteristics; for example, the plant dry weight, plant height, number of flowers plant−1, number of pods plant−1, weight of 100 green seeds and protein concentration in the pea plants during both seasons were decreased compared with the control. Similarly, their physiobiochemical characteristics were negatively affected; chlorophyll a, chlorophyll b and the relative water content (RWC) were significantly reduced in the stressed pea plants. However, malondialdehyde (MDA), hydrogen peroxide, the electrolyte leakage (EL%), super oxide and the antioxidant components (catalase (CAT), superoxide dismutase (SOD), peroxidase (POX) and total phenolic compounds) were significantly increased when the plants were under salt stress compared with the control plants. On the other hand, the foliar application of nano silica and melatonin individually or in combination enhanced the physiobiochemical characteristics, morphological characteristics and yield of the stressed pea plants. The best treatment was the combination treatment (nano silica + melatonin), which caused significant increases in the plant dry weight, plant height, number of flowers and pods plant−1, weight of 100 green seeds, protein concentration, chlorophyll concentrations and RWC in the stressed pea plants. Additionally, the combination treatment significantly decreased the EL%, MDA, O2⋅− and H2O2 and adjusted the upregulation of the antioxidant enzymes, proline and total phenolic compounds in the stressed plants compared with the stressed untreated pea plants. Generally, it can be suggested that the co-application of nano silica (50 mL L−1) + melatonin (75 µM) plays a positive role in alleviating the adverse impacts of salinity on pea plants by modifying the plant metabolism and regulating the antioxidant defense system as well as scavenging reactive oxygen species.