Polyamines and Anaerobic Elongation of Rice Coleoptile

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Abstract
The role of polyamines in the anaerobic elongation of rice (Oryza sativa L.) coleoptiles was studied. The reduced growth of rice coleoptiles under anoxic conditions was accompanied by a massive accumulation of free putrescine. Putrescine was synthesized from arginine in a reaction catalyzed by arginine decarboxylase (ADC). The anoxic titer of putrescine was closely correlated with elongation of coleoptiles. In experiments in which putrescine and inhibitors [α-difluoromethylarginine (DFMA) and α-difluoromethylornithine (DFMO)] of the synthesis of polyamines were exogenously supplied, we demonstrated an absolute requirement for putrescine, synthesized by ADC, for anaerobic elongation of coleoptiles. The presence of exogenous putrescine (alone or in combination with DFMA) increased the rate of anaerobic elongation of coleoptile by 30–40%.