Effects of Cytokinin and Light on Polyamines during the Greening Response of Cucumber Cotyledons

The cucumber cotyledon greening test was used as a model system to study possible relationships between cytokinins and polyamines during the greening process. When cytokinin was applied to dark-grown cotyledons, large increases in chlorophyll and putrescine levels were observed. However, inhibition of putrescine biosynthesis with D-arginine and difluoromethylarginine did not affect chlorophyll production, and applied polyamines proved inhibitory to greening. Addition of 50 mM K$ to the cytokinin treatments increased chlorophyll synthesis but caused a marked reduction in putrescine levels. These results indicate that the large increase in putrescine content that derives from cytokinin treatment of the cotyledons is not essential for the cytokinin-induced greening response.