THE EFFECT OF PRETREATMENT WITH PROLINE ON THE RESPONSES OF PISUM-SATIVUM TO SALT STRESS

10-d-old pea plants (Pisum sativum L. cv. Ran 1) were treated for 24 h with proline (10(-6) M or 10(-5) M) before salinization with 50 mM NaCl for 2 d. Salt stress resulted in an increase of endogenous free proline content, CO2 compensation concentration, photorespiration and glycollate oxidase activity; net photosynthetic rate (P(N)) was inhibited, but dark respiration rate (R(D)) was not affected. (CO2)-C-14 fixation by protoplasts isolated from salt stressed plants was inhibited by 60 %, however, the (CO2)-C-14 fixation by protoplasts, isolated from plants treated with proline before salinization, was only slightly reduced by NaCl. Proline alleviated the inhibitory effect of NaCl in a concentration-depending manner. Pre-treatment with proline decreased Na+ and Cl- accumulation in the shoot; the root content of these ions was increased.