SEED PRIMINGENHANCES DROUGHT STRESS TOLERANCE IN WHEAT SEEDLINGS BY MODULATING ANTIOXIDANT DEFENSE AND GLYOXALASE SYSTEMS

Abstract

An experiment was conducted at the Laboratory of Plant Stress Responses, Faculty of Agriculture, Kagawa University, Japanto investigate the protective effect of priming with some phytopotectants [50 µM salicylic acid (SA), 4 mM, ascorbic acid (AsA) and 2.5 mM NaCl]under drought stress condition [induced by 15 % (m/v) polyethylene glycol, PEG-6000] in wheat. Drought stress caused higher proline (Pro) accumulation, lower relative water content (RWC), chlorosis and growth inhibition. Enhanced levels of the malondialdelyde (MDA) and hydrogen peroxide (H ) were evident with the overproduction of reactive oxygen species (ROS) by disrupting the antioxidant defense system under drought stress condition.The activities of antioxidant enzymes viz. catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR), glutathione reductase (GR), and glutathione peroxidase (GPX) declined under 15% PEG induced drought stress condition. Compared to control seedlings, drought also increased methylglyoxal (MG) formation which also induced oxidative damage by facilitating ROS production. However, priming of wheat seeds with SA, AsA and NaCl decreased the ROS production by decreasing AsA and increasing glutathione content and upregulating antioxidant defense system. Additionally, increased activities of glyoxalase I and glyoxalase II reduced the levels of MG in drought stressed-wheat seedlings. Seed priming helps to recover the seedlings from chlorosis and growth inhibition whereas decreased the MDA and Pro content and increased the activity of antioxidant enzymes. Therefore it can be concluded that seed priming with SA, AsA and NaCl confers drought stress tolerance by upregulating antioxidant defense and glyoxalase system and helps to better seedling establishment. 2 O 2