Alterations in Proline Metabolism in Groundnut (Arachis Hypogaea L.) Under Soil Water Deficits

The effect of water stress was studied on free proline accumulation, activities of pyrroline-5-carboxylate re- ductase (P5C reductase), proline oxidase and proline dehydrogenase along with dry matter and relative water content (RWC) in the leaves of a high yielding groundnut cultivar K-134, in relation to different water stress regimes for a duration of twelve days. Water stress resulted in a significant accumulation of free proline content in leaves of stressed plants over control plants at all stress regimes and the magnitude of accumulation was dependent on the intensity of stress. The activity of P5C reductase was enhanced with stress treatments and positively correlated with the proline accumulation. In contrast, proline oxidase and proline dehydrogenase activity were inhibited during the progression of stress. The patterns of leaf dry matter and RWC ran in parallel and showed decrease in relation to the degree of water stress. These results indicate that during water stress, proline metabolism has been altered in groundnut. The physiological significance of these enzymes to water stress is discussed.