Development Process of Pistils and Stamens and Effect of Endogenous Hormone Content on Style Growth in Plumbago auriculata Lam. with Distyly

To research the development processes in Plumbago auriculata Lam., a typical plant with distyly, the lengths of pistils and stamens and endogenous hormone levels in styles were measured. The development process of pistils and stamens could be divided into five developmental stages:inchoate development stage (T1), turning stage (a) (T2), rapid development stage (T3), turning stage (b) (T4) and smooth development stage (T5). During the whole development process, the growth speed of pistils was always faster than that of the stamens in long-styled flowers. The growth speed of pistils in short-styled flowers was faster than that of the stamens at T1-T2 stages, but slower at T3-T5 stages, which explains why short-styled flowers had shorter pistils. The differentiation between long-and short-styled flowers appeared at the T3-T5 stages, and led to the most obvious feature in flowers of plants with distyly. The contents of IAA, IPA and GA in long-styles were higher than those in short-styles, and were all increased at the T1-T3 stages, but reduced in the T4-T5 stages. In contrast, ABA content was increased at the T4 stages. During style development in P. auriculata, IAA, IPA and GA appeared to have a positive influence on style development, but ABA had a negative influence.