PROLINE ACCUMULATION IN LEAVES OF 4 CULTIVARS OF PHASEOLUS-VULGARIS LWITH DIFFERENT DROUGHT RESISTANCE

Water potential, osmotic potential, relative water content and proline content were measured during water stress in leaves of four bean (Pha seolus vulgaris L.) cultivars, which differ in their drought tolerance . With the development of water deficits, water potential and osmotic potential decreased in all the cultivars. Estimated pressure potential did not significantly change in the drought-resistant cultivars Negro 150 and Michoacan 12A3, and the relative water content remained const ant in Negro 150. Free proline accumulated in the leaves of all four c ultivars. The greatest increases in proline occurred in the drought-su sceptible cultivars Flor de Mayo and Cacahuate 72. Proline accumulatio n accounted for a decreased of 0.48 MPa in the osmotic potential in th e cultivar Negro 150. The other cultivars did not show the expected de creases in osmotic potential despite the great increases in leaf proli ne content. The results suggest that proline accumulation may he a sym ptom of stress in the suceptible cultivars and may play an important r ole in the maintenance of turgor in the cultivars that are drought-res istant.