CONTRIBUTION OF ARGININE TO PROLINE ACCUMULATION IN WATER-STRESSED BARLEY LEAVES

Barley (Hordeum vulgare cv ''Prior'') leaves converted L-U-14C-arginine to labeled proline. Accumulation of radioactivity in proline was greater in wilted leaves, but only after 9 h of incubation. As the increase in free proline was detectable after only 3-6 h, it is likely that the observed stimulation of proline labeling represents a result rather than a cause of proline accumulation. The loss of total arginine during water stress was only 10-15% of the increase in proline. We conclude that arginine probably contributes less than 1% of the C in the expanding proline pool of wilted barley leaves.