ENDOGENOUS POLYAMINE LEVELS AND DARK-INDUCED LEAF SENESCENCE

Inhibition of arginine decarboxylase activity by ca 60-90% in leaves of intact oat seedlings and of Heliotropium indicum plants, treated with difluoromethylarginine alone or together with difluoromethylornithine for ca 13 days, had little effect on the contents of common free polyamines. In barley seedlings, such treatments almost completely inhibited arginine decarboxylase activity and decreased the levels of polyamines, including spermidine and spermine by 85-90%. However, in none of the three species did the inhibitors affect growth or chlorophyll content of the leaves; nor did they affect the rate of chlorophyll decline during dark-induced senescence in intact leaf laminae detached at the end of the treatment with inhibitors.