Short-term salt tolerance mechanisms in differentially salt tolerant tomato species

The physiological changes induced by a daily increase of NaCl level, over a period of 4 d, were studied in leaves of the salt-sensitive cultivated tom ato species Lycopersicon esculentum and its wild salt-tolerant relative Lyc opersicon pennellii. A higher solute contribution to the osmotic adjustment was observed in NaCl-treated leaves of L. pennellii than in those of L. es culentum. This response together with the higher accumulation of inorganic solutes in the wild species and of organic solutes in the cultivated specie s verified the different salt tolerance mechanisms operating in the two spe cies in the short-term. With regard to the changes induced by salt stress o n the free polyamine levels, the putrescine and spermine levels increased w ith salinity, whereas the spermine levels decreased in both tomato species; nevertheless, the main difference between the two species lays in an earli er and greater accumulation of putrescine induced by salinity in L. pennell ii than in L. esculentum. The changes in putrescine levels were associated to changes in amino acids related to its synthesis, and the changes were di fferent in both species. In L. esculentum, the high concentrations of some intermediate compounds (glutamate and arginine) were related to the low acc umulation rate of both proline and putrescine. In contrast, in L. pennellii , important reductions in glutamate and arginine levels were found at the e nd of the salinization period. Moreover, in this last situation, a decline in the putrescine level ran parallel to a high proline accumulation, which suggests that the higher the stress level, the higher the deviation of glut amate to proline occurring in the salt tolerant species. It could be conclu ded that an early accumulation of the diamine putrescine seems to be associ ated with salt tolerance in the short-term. (C) Elsevier, Paris.