POLYAMINES AS SHORT-TERM SALT TOLERANCE TRAITS IN TOMATO

In leaves of a salt-sensitive tomato species (Lycopersicon esculentum Mill.) and its wild salt-tolerant relative species Lycopersicon pennel lii (Correll) D'Arcy, changes induced by NaCl stress in carbon compoun ds (sugars and organic acids), amino acids related to synthesis of pol yamines (glutamate, arginine and proline) and polyamines (putrescine, spermidine and spermine) were compared in light and dark after short-t erm exposure (24 h). The levels of sugars increased more in the salt-s ensitive cultivar upon salt stress, especially under light. The change s in the carbon compounds and amino acids were different under light a nd dark conditions. Thus, in the 200 mM NaCl treated leaves of L. escu lentum, the high sugar accumulation found in light was parallel to the no accumulation of both organic acids and amino acids (glutamate and arginine). The opposite response was observed in the treated leaves of L. pennellii with the same stress level in dark. Putrescine increases with salinity were greater in L. pennellii than in L. esculentum eith er in dark or in light. The higher total polyamine levels in light as opposed to the dark found in both species were rather more due to sper midine and spermine than to putrescine. With regard to the ratio betwe en the diamine putrescine and polyamines, spermidine and spermine, thi s was always higher in L. pennellii than in L. esculentum. Moreover, t he different response between species was clearly observed from the 10 0 mM NaCl treatment. A higher deviation of glutamate compared to proli ne seems to be also related to the salt tolerance during the night, as the proline/polyamine ratio increases were higher in the salt-toleran t species. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.