Abstract: To clarify the mechanism of flower opening and senescence in tree peony ( Paeon ia suffruticosa) ‘Luoyanghong’and‘Huhong’, we investigated sugarmetabolism in the petals of two tree peony cultivars. The results showed that total soluble sugar content increased rap idlywith the cell enlargement in the petals and during flower senescence. The contents of hexoses (glucose and fructose) markedly increased during flower opening and reached a highest level at full-opening, but the content of sucrose dropped gradually. The hexose content and sucrose degradation index ( SDI) were positively correlated with the fresh weight of flower. The activity for acid invertase (AI) increased during flower opening and decreased after the flowers opened. Based on regression analyses, the soluble sugarmetabolism was related to the actions of the 4 enzymes, viz1 acid invertase (AI) , neutral invertase (NI) , sucrose synthase (SS) and sucrose phosphate synthase ( SPS). Our results suggest that hexose accumulation in the petal might be important for flowering opening and senescence in tree peony.

Key words: Paeonia suffru ticosa, flower development, invertase, elongation growth, sugar, metabolism