Senescence in rose (<i>Rosa hybrida</i>L.): role of the endogenous anti-oxidant system

Abstract

SummaryThe role of oxidative stress during petal senescence in rose was investigated. Two cut-rose (Rosa hybrida L.) cultivars, ‘Grand Gala’ and ‘First Red’ were obtained from a commercial grower. Petals were harvested from seven different whorls, outermost-to-innermost in flowers of both cultivars. H2O2 production was determined throughout flower bud senescence, and the H2O2-scavenging enzyme system was studied. The activities of catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APOD) increased up to Stage-5 of flower bud development (petals completely unfolded) and declined thereafter. The highest level of glutathione reductase (GR) activity was observed at Stage-4 (sepals completely opened, petal starting to unfold), followed by a significant decrease at later stages, coincident with higher levels of ethylene production. This limits the role of APOD from Stage-4 onward and is responsible for the failure of free radical scavenging in rose petals. In this context, the role of POD becomes important in protecting the flower from free radicals. Thus, an increase in endogenous H2O2 levels and a decrease in anti-oxidant enzyme activities may be partly responsible for initiating senescence in rose petals.