PHENOLIC COMPOUND VANILLIC ACID MODULATES GROWTH AND DEFENSE SYSTEM OF CABBAGE (BRASSICA OLERACEA VAR. CAPITATA L.) UNDER DROUGHT STRESS

The primary purpose of this investigation was to evaluate the influence of externally applied vanillic acid (VA) on growth, osmoprotectants accumulation, and the oxidative defense system of two cabbage cultivars (Cbs-174F1 and Hcb-1040-B) under water stress. The imposition of scarcity of water at the rate of 60% field capacity led to a notable decrease in cabbage plant biomass along with their lengths. Furthermore, a remarkable reduction was observed in total chlorophyll and chlorophyll a and b pigments in both leaves and heads of the cabbage under water scarcity. Concurrently, there was an increase in leaf free proline, total phenolics, total soluble proteins, hydrogen peroxide (H2O2) and the activities of peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) under drought stress. Foliar-applied vanillic acid (2.0 and 4.0 mM) resulted in significant enhancement in all the observed growth attributes. Moreover, there was an improvement in chlorophyll and ascorbic acid contents, along with the activities of POD, CAT and SOD enzymes in both leaves and heads of cabbage, particularly in limited supply of water. Foliar spray of VA also led to an increased accumulation of proline, total phenolics, and total soluble proteins in both leaves and heads of both cabbage cultivars. VA application also resulted in reducing the accumulation of hydrogen peroxide and relative membrane permeability. In a comprehensive view, the positive influence of externally applied VA on cabbage plant growth had been due to enhanced osmoprotectants accumulation and antioxidant defense system especially by lowering H2O2 and MDA contents under water deficit conditions.