Enhanced oxidative stress, damage and inadequate antioxidant defense contributes towards insufficient recovery in water deficit stress and heat stress combination compared to either stresses alone in (Bathua).

(common name Bathua) is a widely adapted weed plant facing wide array of temperatures (5-45 °C) during growth and development in North India. Antioxidant defense was studied in leaves under water deficit stress, heat stress, water deficit stress and heat stress combination and water deficit preconditioning followed by heat stress. plants subjected to water deficit stress and heat stress combination showed higher decline in water relations and lesser recovery compared to either stresses alone. Highest HO content, lipid peroxidation and protein damage were observed in plants experiencing water deficit stress and heat stress combination which was coupled with less induction in activities of SOD, CAT and all AsA-GSH cycles enzymes and decline in AsA and GSH pool compared to plants subjected to either stress alone. Water deficit preconditioned plants maintained higher activities of antioxidant defense enzymes and metabolites such as SOD, CAT, POX, DHAR, GSH content and AsA/DHA and GSH/GSSG ratios compared to non-preconditioned plants under heat stress. This is the first holistic report on effect of water deficit stress and heat stress combination and water deficit preconditioning followed by heat stress on ROS, damage and antioxidant defense including enzymes and metabolites in . Water deficit stress and heat stress combination was more detrimental in than either of the stresses alone as decline in water relations and increase in oxidative stress and damage was coupled with a decline in antioxidant defense both in enzymes i.e. SOD, CAT and AsA-GSH cycles enzymes and metabolites i.e. AsA and GSH content. Water deficit preconditioning followed by recovery resulted in induction of co-ordinated antioxidant defense in terms of both enzyme activities and metabolites during subsequent heat stress in . Enhanced CAT activity and higher redox pool played a major role in cross tolerance in water deficit preconditioned plants under heat stress.