Alleviating effects of salicylic acid spray on stage-based growth and antioxidative defense system in two drought-stressed rice (Oryza sativa L.) cultivars

Approximately 33% of the arable land around the world is vulnerable to drought, which is a very serious issue affecting the yield and productivity of cereal crops. Two contrasting rice (Oryza sativa L.) genotypes, HTT-138 (drought tolerant) and (HTT-39 drought -sensitive), under various levels of water treatments, i.e. control flooded (CF) as recommended for rice (control), control saturated (CS) 100% field capacity (FC), 80% FC, and 60% FC without or with foliar spray (100 mg L-1) of salicylic acid (SA) evaluated to enhance the yield for food security. The results showed that leaf gas exchange parameters, water use efficiency and water related parameters reduced under all levels of water deficient conditions. Drought stress increased oxidative stress (superoxide anions and hydrogen peroxide) and decreased after foliar spray of SA due to enhancement in antioxidant activity (catalase, ascorbate peroxidase, peroxidase, superoxide dismutase). Ascorbic acid, total soluble protein, total soluble sugar, total phenolics, proline, anthocyanin, salicylic acid, and amylase activity were reduced under drought stress and increased after foliar spray of SA. HTT-138 showed more tolerance to the drought stress than HTT-39 under the same levels of water deficient conditions. Although drought-stress was ameliorated by the foliar spray of SA which not only increased plant growth, dry weight, and metabolism or metabolic activities but also increased the nutritional status of the plant by decreasing the concentration of reactive oxygen species (ROS) in the membranous bounded organelles. In conclusion, the foliar spray of SA is useful to enhance plant growth and yield in cereal crops especially those grown in abiotic stress environments.