We have studied the influence of pretreatment of wheat seedlings (Triticum aestivum L.) with 50 M
salicylic acid (SA) on plant resistance to subsequent action of 1 mM cadmium acetate. SA pretreatment
decreased the extent of detrimental effect of cadmium on wheat plants, as judged by the decline in
the level of stress-induced accumulation of MDA and electrolyte leakage. Furthermore, SA-pretreatment
contributed to maintenance of growth characteristics of wheat seedlings at the level close to the control
under stress conditions and to acceleration of growth recovery during post-stress period. Detected
defense effect of SA may be due to a decline in the amplitude of cadmium-induced accumulation of
abscisic acid (ABA) and to reduced fall of indoleacetic acid (IAA) and cytokinins (CK) in stressed plants.
In the course of one day treatment, SA activated phenylalanine ammonia-lyase (PAL), the key enzyme of
lignin biosynthesis, in roots of seedlings under normal growth conditions contributing to the strengthening
of carrier functions of cell walls. This assumption is supported by the data showing significant decline
in cadmium accumulation in SA-pretreated plants, especially in the shoots. Cd-treatment was shown
to result in accumulation of dehydrins with molecular mass 22, 28, 55 and 69 kDa in wheat seedlings,
although low molecular weight dehydrins (22 and 28 kDa) showed greater stress sensitivity. It is noteworthy
that SA-pretreatment by itself led to 1.5-fold increase in the content of low molecular weight
dehydrins. Nevertheless, SA-pretreated seedlings were characterized by significantly lower Cd-induced
accumulation of all of the four dehydrins, apparently due to inhibition of cadmium flow into the plants.
The obtained data suggest involvement of dehydrins in the range of defense reactions induced by SAtreatment
contributing significantly to development of plant resistance to subsequent action of stress.
The use of fluridone allowed us to demonstrate the key role of endogenous ABA in SA-induced changes
in the level of dehydrins as well as in the protective effect of SA on wheat plants under cadmium stress
resulting from development of defense responses in the course of SA-treatment.