EFFECTS OF CHEMICALLY DIFFERING CYTOKININS ON ZUCCHINI COTYLEDON GROWTH IN PRESENCE OF COPPER IN EXCESS

Cu(2+) began to inhibit zucchini cotyledon growth when CuSO(4) was applied at least at a concentration of 1000 mu M. The concentration-dependent suppression was observed both on cell growth and cell division. The growth inhibition of the light-cultivated cotyledons was much stronger. The phenylurea cytokinin (10(-5) M 4PU-30) definitely counteracted the heavy metal-caused inhibition of the growth, while the effects of the purine cytokinin (10(-5) M BA) were contradictory. In the marginal region of cotyledon plate meristem, BA even enhanced the inhibitory effect of Cu(2+), especially toward the division activity. The counteracting effects of cytokinins to Cu(2+) in excess were better expressed in the stress light conditions for the cotyledon growth - continuous light or complete darkness.