Effects of NaCl and Proline on Polyphenol Oxidase Activity in Bean Seedlings

In this work, the effects of NaCl (0, 50, 100, and 150 mM), proline (0, 5 and 10 mM) and NaCl + proline in combinations on activity of polyphenol oxidase (PPO; E.C. 1.10.3.1) and soluble protein content have been investigated in the root, stem and leaf tissues of bean (Phaseolus vulgaris L.) seedlings grown in embryo culture. PPO activities were higher in all the tissues treated with NaCl, proline and NaCl + proline combinations those that of the control tissues. The protein content was very high in tissues exposed to proline and NaCl + proline combination, but NaCl alone decreased protein contents in root and leaf tissues. The results suggest that proline may play a role as an enzyme-stabilizing agent in salt stress.