Interactive Effect of Drought Stress and l-Methionine on the Growth and Physio-Biochemical Changes in Broccoli (Brassica oleracea L. var. italica): Leaf and Head

The present study was conducted to assess the effectiveness of exogenously applied l-Methionine (Met) in drought stress tolerance of two broccoli (Brassica oleracea L. var. italica) cultivars. Fifty-day-old seedlings of two broccoli cultivars were exposed to control [100% field capacity (F.C.)] and water deficit stress (60% F.C.). After 30 days of imposition of drought stress, broccoli plants were subjected to varying (15 and 30 mg/L) concentrations of Met along with a control as a foliar spray. Water deficit stress caused a significant reduction in plant growth and yield attributes of both broccoli cultivars. Drought stress also negatively affected the leaf and head characteristics of broccoli such as head weight and chlorophyll pigments of both cultivars, while the levels of ascorbic acid (AsA), glycinebetaine (GB), total phenolics, proline contents as well the activities of key enzymes including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were significantly enhanced in both leaf and head of broccoli. Foliar applied Met prominently improved the leaf and head chlorophyll pigments, GB, AsA, total phenolic contents and activities of SOD, POD, and CAT enzymes in both cultivars of broccoli under stress as well as non-stress conditions. Overall, the results revealed that foliar applied Met was effective in upregulating the growth, yield and leaf and head oxidative defense system of broccoli, and thus suggested the active involvement of Met in improving the growth and yield potential of both broccoli cultivars under stress and non-stress conditions.