CHANGES IN FREE POLYAMINE LEVELS INDUCED BY SALT STRESS IN LEAVES OF CULTIVATED AND WILD TOMATO SPECIES

The effects of NaCl on endogenous free levels of the polyamines putres cine, spermidine and spermine, and the relationships between polyamine s, K+ levels and Na+ accumulation were determined in leaves of the cul tivated tomato (Lycopersicon esculentum Mill.) and its wild, salt-tole rant relative L. pennellii (Correll) D'Arcy at different exposure time s during a 32-day period. Both stress treatments (100 and 200 mM NaCl) decreased the levels of putrescine and spermidine. although to a diff erent degree for the cultivated and wild tomato species. The spermine levels did not decrease with salinity in L. pennellii over the saliniz ation period, whereas they decreased in L. esculentum, except at the f irst application of the 100 mM NaCl treatment. In both species, the ch anges induced by salinity in total polyamines and K+ were very similar , with the accumulation of Na+ in the leaf being concomitant with a de crease in both total polyamines and K+. This suggests that the main ro le of the polyamines in the salt-treated plants, at least in the long term, is to maintain a cation-anion balance in leaf tissues. In this s ense, a direct relationship between total polyamines and K+, and inver se relationships between polyamines and Na+ and between K+ and Na+ wer e found for both species. In the shea term (up to 4 days) a peculiar p hysiological behavior was found in L. pennellii, as the total polyamin e and K+ levels decreased at 100 mM but not at 200 mM NaCl, while afte r this time the latter plants had values lower than those of the 100 m M NaCl-treated plants at day 11.