Activity of glycollate oxidase (GO) was inhibited by allantoin in spinách leaves after vacuum infiltration. The GO activity was inhibited by 60.1 % at 1.5 mM allantoin. The activity of catalase was inhibited by allantoin too, both in vitro and in vivo experiments, and accumulation of H2O2 inhibited the GO activity. Mercaptoethanol decreased the inhibitoiy effects induced by allantoin and protected the GO activity. As to the mechanism of the inhibitory elfect, it is possible tiiat allantoin inhibited GO indirectly through its inhibitory eťfect on catalase and subsequent H2O2 accumulation in spinách leaves. This, in tum, oxidized essential sulfhydryl group(s) on GO and inhibited its activity.
A brief pulse' of red (R) radiatíon increased actívity and protein content of phosphoenolpyruvate carboxylase (PEPC): diis increase was inhibited by cycloheximide. The efifect of R was far-red pulse (FR) reversible when R was followed inunediately (but not after 24 h) by FR. Thus phytochrome was involved in PEPC regulatíon in etiolated maize leaves. Both a lag phase and a saturation exist in the process of R induction of PEPC synthesis: the highest PEPC acitívity was obtained 24 h after R. Etiolated maize leaves of different age showed different sensitivity to R: the highest sensitivity was found in 5 d-old seedlings. 5 min of R was sufficient for inducing PEPC synthesis, and no additíonal increases were obtained in actívity and protein content of PEPC when the R tíme was prolonged.