Effect of Endogenous Hormone Concentrations on Wizened Bud in Pear

Abstract

To investigate the relationships between changes in endogenous hormone concentrations and occurrence of wizened bud in pear, we sampled buds of ‘Yuluxiang’ pear from a pear orchard with occurrence of wizened bud (abnormal) and orchards with normal bud development in Weixian, Hebei, China, and in Taigu, Shanxi, China. Vegetative shoots on trees in the abnormal orchard grew later in the season and were longer than shoots on trees in the normal orchards. Wizened buds became obvious during the sepal differentiation phase in early to mid-July. We used ELISA to analyze changes in bud endogenous hormone concentrations at the flower bud differentiation stage. The indole acetic acid (IAA) concentration in abnormal buds was higher than that in normal buds, at the occurrence of wizened bud stage. The abscisic acid (ABA) concentration in normal pear buds was significantly higher than that in abnormal buds from mid-June to early Aug., whereas the gibberellic acid (GA ₃) concentration in normal pear buds was lower than that in abnormal buds. Concentrations of zeatin riboside (ZR) in normal buds were lower than those in abnormal buds from early June to mid-June (initial stage of flower bud differentiation). Ratios of ZR/GA ₃, ABA/GA ₃, ABA/IAA, ABA/ZR, ABA/(ZR+GA ₃), ABA/(IAA+GA ₃), and ABA/(ZR+GA ₃+IAA) in normal buds were significantly higher than those in abnormal buds in Weixian. We hypothesize that orchard practices that suppress vegetative growth, regulate plant hormone metabolism, and create balance between vegetative growth and reproductive growth, may decrease the incidence of wizened bud.