[Combined effect of zeatin and hydrogen peroxide on growth of rape and tomato germs as applied to the conditions of biological life support systems].

Cytokine-regulated growth of germs' roots and hypocotyls was investigated on a background of modeled oxidative outbreak caused by the stress from exogenous hydrogen peroxide. Germs of rape (1-d old) and tomato (56-d old) in Petri dishes with solutions containing substances under study were subjected to 24-48 hour incubation in the dark. Exogenous zeatin inhibited growth; in different tests treatment with H2O2 brought about both acceleration and inhibition of root and hypocotyl growth. The combined use of two substances deformed concentration curves. Hydrogen peroxide concentration of 100 microM without cytokines inhibited growth of tomato root significantly, whereas application of 0.003-0.01 and 0.9 microM of zeatin intensified root growth. The series of zeatin concentration-effect curves obtained for rape roots and hypocotyls with gradually increasing H2O2 concentration included the inhibition curve (w/o H2O2), curve with predominant growth stimulation and reliable maximum (1 microM of H2O2), intermediate shape curves (0.3 and 3.3-10 microM). Hence, biological life support systems should be designed with consideration for variability of effects of physiologically active substances under conditions of stress.