EFFECTS OF OSMOTIC AND SALT STRESSES ON THE ACCUMULATION OF POLYAMINES IN LEAF SEGMENTS FROM WHEAT-VARIETIES DIFFERING IN SALT AND DROUGHT TOLERANCE

Polyamine accumulation under short-term non-ionic osmotic and salt stress was compared in leaf segments of 8 wheat varieties differing in drought and salt tolerance in order to test whether various stress conditions impair different steps of polyamine biosynthesis. The highest putrescine accumulation occurred in the known salt and drought tolerant varieties under non-ionic osmotic stress (400 mOSm L-1 sorbitol for 10 h), while in the presence of NaCl of the same osmolarity, only the known salt tolerant variety responded with increased putrescine level. Spermidine titer was slightly influenced by both stress conditions and spermine content increased only under salinity. The putrescine precursor agmatine accumulated under osmotic stress, while the end product 1,3-diaminopropane appeared only under salt stress. These results suggest that with respect to the onset of polyamine biosynthetic and degradative processes, osmotic and salt stresses are two distinct conditions.