INCREASED LEVELS OF CYTOKININ INDUCE TOLERANCE TO NECROTIC DISEASES AND VARIOUS OXIDATIVE STRESS-CAUSING AGENTS IN PLANTS

External application of 20 mu g.ml(-1) kinetin or 20 mu g.ml(-1) benzy ladenine for 2 weeks increased the tolerance of tobacco plants to the oxidative stress caused by 8.6 x 10(-5) M paraquat or 0.1 % HgCl2 or 2 .5 x 10(-3) M fungal toxin fusaric acid. After kinetin treatment the m embrane stability increased, since phospholipid content increased and the free sterol content decreased in the treated plant tissues. Tomato plants regenerated from Agrobacterium tumefaciens tumors also showed an elevated tolerance to the superoxide-producing compound, paraquat a nd to fusaric acid. The above data suggest that by increasing juvenili ty of leaf tissues tolerance to some stressful conditions can be incre ased in plants.