Antioxidant enzyme and plant productivity changes in field-grown tomato under drought stress conditions using exogenous putrescine

Scarcity of water is a severe environmental constraint and the growth and development of tomato (Lycopersicon esculentum Mill.) seedlings are strongly inhibited under drought stress. Putrescine (PUT) is involved in drought stress tolerance. There is little information about the exogenous application of PUT on tomato seedlings under drought stress. This experiment was carried out to examine the application of putrescine on some physiological and biochemical characteristics of tomatoes under water stress. Plants were exposed to three water conditions: 100% (ET0) as the non-drought treatment (or control), 75 and 50% of ET0 as the water- stress treatments. Foliar application of PUT was done using 0.5 and 1 mgL^-1 concentrations, while control plants were sprayed with distilled water. Drought stress significantly affected plant growth and productivity, and reduced leaf area (LA), plant height and fruit yield at 50% ET0 compared to the control treatment. Also antioxidant enzymes such as SOD, PPO and CAT were increased by increasing the drought stress level. Moreover, the activity of PPO, CAT and SOD enzymes were elevated by the PUT foliar application. Results showed that appropriate PUT doses persuade biosynthesis of important metabolites, which may reduce the negative effects of drought stress on tomato plants.