JASMONATES - HORMONAL REGULATORS OR STRESS FACTORS IN LEAF SENESCENCE

Specific cyclopentanone compounds such as (-)-jasmonic acid (JA) and its methyl ester (JA-Me) or (+)-7-iso-jasmonic acid are considered putative plant growth regulators for a number of reasons, including their ubiquitous occurrence in the plant kingdom, structural specificity in physiological responses, and interaction with other phytohormones in the biological activities of jasmonates. In this respect leaf senescence promotion is of particular preponderance. Recent progress in the mode of jasmonate actions in the barley leaf segment senescence model system demonstrates two effects at the level of gene expression: the induction by exogenously applied jasmonates of abundant specific proteins and their mRNAs (transcription control), and the cessation of synthesis of normal leaf proteins but not their respective mRNAs (translation control). These effects resemble cellular responses to well-known stress factors. The arguments for and against hormonal or stressor-like actions of jasmonates in leaf senescence are discussed in this review. © 1990 Springer-Verlag New York Inc.