POTASSIUM-INDUCED ANTIOXIDANT DEFENSE AND REGULATION OF PHYSIOLOGICAL PROCESSES TOWARDS DROUGHT STRESS TOLERANCE IN WHEAT

Abstract

Drought imparts injuries in plant through elevated production of reactive oxygen species viz. (O 2 • , OH • , H 2 O 2 and 1 O 2 ). Potassium (K) triggers numerous ameliorative functions against oxidative damages caused by drought. To investigate K attenuating oxidative damage and promotion of antioxidant defense in wheat (Triticum aestivum L. cv. BARI Wheat-21), an experiment was carried out at the Laboratory of Plant Stress Responses, Faculty of Agriculture, Kagawa University, Japan, under controlled environment of green house during June, 2017 to December, 2017. A total number of nine treatments were combined considering three K doses viz. 0 mM (-K), 6 mM (+K) & 12 mM (+2K) in Hoagland nutrient solution exposed to 3 distinct water regimes viz. 100% FC, 50% FC, and 20% FC for 9 days. The experiment was designed in CRD model. Imposed drought stress notably reduced Plant height, fresh weight (FW), dry weight (DW), leaf relative water content (RWC %) along with chlorophyll content in dose dependent manner. Increased drought stress elevated the amount of oxidative markers viz. malondialdelyde (MDA), hydrogen peroxide (H 2 iii O 2 ), methyl glyoxal (MG) and proline (Pro). Wheat seedlings treated with drought stress resulted in notable decrease of ascorbate (AsA), reduced glutathione (GSH) and increase of glutathione disulphide (GSSG). Enzymatic activities of AsA-GSH cycle enzymes were declined except the ascorbate peroxidase (APX), which was increased under drought stress combination. On the contrary, potassium (K) supply resulted in improved Chlorophyll contents, and water status along with increased GSH content and reduced the GSSG content which ultimately improved GSH/GSSG ratio. However, K reduced MDA, H 2 O 2 , Proline contents and up regulated the antioxidant enzymes activities. Exogenous K reduced the ROS production through increasing AsA. Additionally, In K treated plant activities of glyoxalase I and glyoxalase II enzymes reduced the levels of MG and overall increased the activity of glyoxalase system. However, plant showed better physiological performances under 50% drought stress with 12 mM K was observed in the overall study. Therefore it can be concluded that K confers drought stress tolerance in wheat seedlings through up regulating antioxidant defense and glyoxalase system which helped in better seedling establishment.