Turgor maintenance, osmotic adjustment and soluble sugar and proline accumulation in 49 pea cultivars in response to water stress

The response of 49 pea cultivars with different drought tolerance was studi ed. The tolerance to stress was determined according to the grain yield or the harvest index in rainfed fanning. In these conditions variability among the genotypes in turgor maintenance, measured as the slope of the turgor p otential (psi(p)) function against water potential (psi(w)), was observed. The cultivars, which best maintained turgor, were those which were more dro ught-tolerant. Turgor maintenance was significantly related to osmotic adju stment (OA). However, OA does not explain all the variability observed in d psi(p)/d psi(w). Therefore, other factors such as tissue elasticity may al so be influential. Soluble carbohydrate concentration increased (from 1.5 t o 7 times) when the studied cultivars were subjected to water stress. The l ines with a conventional leaf-type, showed a greater sugar content than sem ileafless lines when watered as well as when subjected to desiccation. The stimulation of sugar levels induced by drought was proportional to OA. Duri ng stress, the average soluble sugar content of all cultivars would be equi valent to 17.3% or 8.6% of psi(s100), if all carbohydrates were present in the tissue as monosaccharides or disaccharides, respectively. This suggests that sugars play an important role in OA in peas. The free proline level a lso increased (from 4 to 40 times) in response to water stress. However, th e contribution of this amino acid to psi(s100) was small (approximately 1%) and no significant relationship was observed between proline content and O k The cultivars which accumulated more proline had lower water contents upo n turgor loss. This seems to indicate that proline may play a role in minim izing the damage caused by dehydration. (C) 1998 Elsevier Science B.V. All rights reserved.