Involvement of glucose in the regulation of ethylene biosynthesis and sensitivity in cut Paeonia suffruticosa flowers

Abstract

Exogenous application of sugars has been known for decades to extend flower longevity effectively. The prevailing view is that sugars provide respirable substrates, structural constituents and osmolytes; however, interaction with plant hormone ethylene seems to be more important for several ethylene-sensitive flowers. To determine whether and how sugars interact with ethylene to regulate postharvest flower senescence in Paeonia suffruticosa, a traditional ornamental plant in China with most ethylene-sensitive cultivars, we investigated the effects of glucose on ethylene biosynthesis and sensitivity in relation to postharvest flower development. Cut P. suffruticosa flowers continuously treated with glucose, but not the osmolyte mannitol, showed delayed visible senescence and extended vase life. Glucose treatment delayed and inhibited the climacteric increase in ethylene production of cut flowers associated with the delay and inhibition of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS) activity, as well as the suppression of ACC oxidase (ACO) activity in petals, which is at least partially explained by the repression of PsACS1 mRNA accumulation. Exposure of cut flowers to ethylene shortened vase life and stimulated autocatalytic ethylene production. However, these effects of ethylene were markedly reduced in the flowers with prior glucose treatment rather than mannitol, suggesting that glucose directly decreases the sensitivity to ethylene. Additionally, glucose prevented the effect of ethylene in inducing PsACS1 mRNA accumulation but did not affect PsACO1 mRNA level. These results indicate that glucose extends the vase life of cut P. suffruticosa flowers, possibly through both a delay and inhibition of ethylene biosynthesis, and a decrease in sensitivity to ethylene.