Water stress induced physiological and biochemical changes in Piper betle L. and Ricinus communis L. plants and their effects on Spodoptera litura

Plant responds to stresses by developing adaptive changes, which some times are complex and can be synergistically or antagonistically adjusted by the plant defense mechanisms. We studied the abiotic stress induced changes in physiological, biochemical and oxidative level reactions caused by drought stress in Piper betle L. (Piperaceae) and Ricinus communis L. (Euphorbiaceae) plants and their influence on the feeding performance of herbivore, Spodoptera litura: Under drought stress, the leaf chlorophyll and relative water content (RWC) in both test plants were decreased than controls. In piper and castor plants, the quantitative analysis was carried out on leaf biochemicals (carbohydrates, proteins, amino acids, flavonoids and phenols) under drought conditions. The decrease in the individual phenolic acids in both plants due to stress caused by water deficit was determined using HPLC analysis. The reduced levels of primary metabolites were evident in both plants, while flavonoid content enhanced along with amino acid content in castor plants. These changes created a favorable environment for S. litura and increased the feeding rate in both drought affected castor and piper plants than their normal plants. Increased levels of antioxidative enzymes [superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT)] in leaves of P. betle and R. communis indicate their defensive and/or protective role against the ROS generated under drought conditions. It was concluded that drought conditions induced the defense responses in both P. betle and R. communis plants, which regulated the herbivore feeding performance.