Physiological changes after exposure to and recovery from polyethylene glycol-induced water deficit in callus cultures issued from durum wheat (Triticum durum Desf.) cultivars differing in drought resistance

Calli obtained from three durum wheat (Triticum durum Desf.) cultivars with different drought resistance levels were exposed for 30 days to a polyethy lene glycol-induced water deficit followed by 30 days of recovery. Relative growth rate, percent dry weight, osmotic potential and the changes in inor ganic and organic solutes were determined at the end of both the stress and the recovery periods. After the stress period, calli derived from the drou ght resistant cultivars, particularly Omrabi 5 and to some extent Haurani, showed a less reduced relative growth rate, lower osmotic potential and hig her proline and other amino acid accumulations as compared with the sensiti ve cultivar Kabir I. Drought resistance could also be associated with a bet ter protection of enzymes involved in nitrogen metabolism. At the end of th e recovery period, most of the quantified parameters, except osmotic potent ial, recovered completely, indicating the reversibility of the changes indu ced by water deficit at the plant cell level in durum wheat. Our data show that a correlation exists between performances of the cultiva rs under drought and the responses of callus cultures to PEG-induced water deficit; this suggests that: in durum wheat the degree of resistance to dro ught at the plant level depends, at least in part, on the existence of mech anisms operating at the cellular level.