WATER RELATIONS AND OSMOTIC ADJUSTMENT IN LYCOPERSICON-ESCULENTUM ANDL-PENNELLII DURING SHORT-TERM SALT EXPOSURE AND RECOVERY

Cultivated tomato Lycopersicon esculentum (L.) Mill. cv. P-73 and its wild salt-tolerant relative L. pennellii (Correll) D'Arcy accession PE -47 growing on silica sand in a growth chamber were exposed to 0, 70, 140 and 210 mM NaCl nutrient solutions 35 days after sowing. The salin e treatments were imposed for 4 days, after which the plants were rins ed with distilled water. Salinity in L. esculentum reduced leaf area a nd leaf and shoot dry weights. The reductions were more pronounced whe n sodium chloride was removed from the root medium. Reduction in leaf area and weight in L. pennellii was only observed after the recovery p eriod. In both genotypes salinity induced a progressive reduction in l eaf water potential and leaf conductance. During the recovery period l eaf water potential (psi(l)) and leaf conductance (g(I)) reached level s similar to those of control plants in wild and cultivated species, r espectively. Leaf osmotic potential at full turgor (psi(os)) decreased in the salt treated plants of both genotypes, whereas the bulk modulu s of elasticity was not affected by salinity. Leaf water potential at turgor loss point (psi(tlp)) and relative water content at turgor loss point (RWC(tlp)) appeared to be controlled by leaf osmotic potential at full turgor (psi(os)) and by bulk modulus of elasticity, respective ly. At lowest salinity, the wild species carried out the osmotic adjus tment based almost exclusively on Cl- and Na+, with a marked energy sa vings; Under highest salinity, this species accommodate the stress thr ough a higher expenditure of energy due to the contribution of organic solutes to the osmotic adjustment. The domesticated species carried o ut the osmotic adjustment based always on an important contribution of organic solutes.