Chronological changes in plant hormone and sugar contents in cv. Ao-Shuang autumn flowering tree peony

Abstract

Successive secondary flowering is critical for tree peony industry. Varying the levels of hormones and sugars are reported to influence plant flowering. This study analyses quantitative changes in the levels of endogenous hormones [indole-3-acetic acid (IAA), abscisic acid (ABA) and gibberellic acid (GA₃)] and carbohydrates (sucrose, reducing sugar and starch) in the buds of cv. Ao-Shuang tree peony during autumn and spring flowering seasons. The study shows different levels of hormones (ABA, IAA and GA₃) and carbohydrates (sucrose, reducing sugar and starch) in spring (SFB) and autumn (AFB) flowering buds. Not only is there increase in IAA, GA₃, sucrose and reducing sugar, but also decrease in ABA and starch during AFB developmental stages. This probably contributes to induced flowering in AFB. Compared with SFB, IAA could be a vital AFB flowering hormone because it peaks at three critical bud developmental stages of bud swelling, shoot elongation and flower bud opening. Whereas sucrose and reducing sugar contents increase in AFB, that of starch decreases. SFB shows similar trends for sucrose, reducing sugar and starch. The findings suggest that cv. Ao-Shuang tree peony blooms in autumn probably due to lack of dormancy, a phenomenon induced by low ABA. Thus flowering of tree peonies in SFB and AFB could be regulated by different combinations of hormonal and sugar signals.