POLYAMINES AND RELATED ENZYMES IN RICE SEEDS DIFFERING IN GERMINATIONPOTENTIAL

In ungerminated rice seeds, (Japonica rice variety, CV Tapei 309), the content of free amines (putrescine, spermidine, spermine, tyramine) w as higher in seed lots having a low germination frequency compared to those with high germination potential. Conversely, amine conjugates (d i-feruloylputrescine, di-feruloylspermidine, di-feruloyldiaminopropane and feruloyltyramine) decreased with loss of viability. Thus, these c ompounds appeared to constitute biochemical markers of seed viability. In seeds with high germination potential, conjugates decreased drasti cally during germination, with an early and rapid increase in free ami nes (putrescine, spermidine, tyramine). Arginine decarboxylase (ADC) a ctivity was highest during the germination of high germination potenti al seeds, its activity gradually declining with loss of viability and being closely correlated with agmatine content. The polyamine biosynth etic inhibitors (alpha-DL-difluoromethylarginine, DFMA, a specific and irreversible inhibitor of ADC; alpha-DL-difluoromethylomithine, DFMO, a specific irreversible inhibitor of ornithine decarboxylase (ODC); c yclohexylammonium sulfate, CHA, inhibitor of spermidine synthase) neit her depleted putrescine and spermidine levels nor inhibited germinatio n in high germination potential seeds. In low germination potential se eds, the germination process was inhibited by DFMA or CHA. Application of agmatine resulted in a reversal of inhibition, DFMA inhibited ADC activity in both categories of seeds. In low germination potential see ds treated with CHA no ADC activity was found. These results suggest t hat amines are involved in the germination process of rice seeds. It a ppears that amine conjugates may serve as a storage form of amines whi ch, upon enzymatic hydrolysis, could supply the cell with an additiona l amine reserve and influence cell division and/or cell elongation.