Senescence of rice leaves XXIX. Ethylene production, polyamine level and polyamine biosynthetic enzyme activity during senescence

Abstract

Changes of ethylene production, polyamine level and activities of enzymes related of polyamine biosynthesis during senescence of intact leaves of rice ( Oryza sativa L.) seedlings were investigated. Ethylene production decreased markedly at the early stage of senescence, but increased slightly at the later stage. Putrescine, spermidine and spermine, but not cadaverine and diaminopropane, were present in rice leaves throughout senescence. The spermine level decreased progressively with increasing age. The putrescine and spermidine levels as well as arginine decarboxylase activity decreased at the early stage of senescence and increased at the later stage. The increase of ornithine decarboxylase and S-adenosylmethionine decarboxylase activities occurred at the time when leaves were fully expanded and at an advanced stage of senescence. These data seem to support the view that polyamines play an important role in the regulation of rice senescence. Results also suggest that endogenous polyamine levels and ethylene production may not be interrelated during senescence of rice leaves.