Ethylene-induced Senescence and Physiological Disorders in Harvested Horticultural Crops

Abstract

Ethylene plays a major role in plant senescence via its direct and indirect effects on the regulation of metabolism. The known physiological and biochemical effects of C 2 H 4 on harvested horticultural crops include increased respiratory activity; increased activity of enzymes such as polygalacturonase, peroxidase, lipoxidase, alphaamylase, polyphenol oxidase, and phenylalanine ammonialyase (PAL); increased permeability and loss of cell compartmentalization; and alteration of auxin transport or metabolism (34). Nevertheless, the mechanism by which C 2 H 4 promotes senescence remains unknown. Lieberman (21) stated that the action of C 2 H 4 in accelerating senescence can be associated with interactions with auxins, gibberellins, cytokinins, and abscisic acid (ABA). The mechanisms involved in these interrelationships are not fully understood, but there is evidence to suggest that a general antagonism exists between the senescence promoters (C 2 H 4 and ABA) and the senescence inhibitors (auxins, gibberellins, and cytokinins).