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 Na
Cl for 2 d. Salt stress resulted in an increase of endogenous free pro
line content, CO2 compensation concentration, photorespiration and gly
collate oxidase activity; net photosynthetic rate (P(N)) was inhibited
, but dark respiration rate (R(D)) was not affected. (CO2)-C-14 fixati
on by protoplasts isolated from salt stressed plants was inhibited by
60 %, however, the (CO2)-C-14 fixation by protoplasts, isolated from p
lants treated with proline before salinization, was only slightly redu
ced by NaCl. Proline alleviated the inhibitory effect of NaCl in a con
centration-depending manner. Pre-treatment with proline decreased Naand Cl- accumulation in the shoot; the root content of these ions was
increased.