Abstract:Effects of different photoperiods (16 h/8 h;12 h/12 h;8 h/16 h) on floral buds differentiation and contents of endogenous putrescine (Put),spermidine (Spd) and spermine (Spm) in the leaves and buds of Dendranthema grandiflora ‘Shenma‘ during floral buds d