Studies On Differentiation Process Of Flower Buds Of Rhododendron Moulmainense Hook. And Some Physiological Charactors

Rhododendron moulmainense Hook., an evergreen shrub or small arbor of Rhododendron genus in the Ericaceae family, is a scarcity kind of Alpine Rhododendron with great ornamental value. Its florescence comes in March or April, with big yet few flower buds, and big and colorful flowers. There are more than 4000 Rhododendron moulmainense Hook. in the Wu Tong Mountain Forest Park (a mountain type park rarely found near the urban) in Shenzhen, but the flowering rate is extremely low(<5%). In order to improve the flowering rate, it is of value to study the differentiation process of flower buds of Rhododendron moulmainense Hook. and the major influencing physiological characters to find some reasonable regulating measures.Based on the observation of the morphological characteristics of Rhododendron moulmainense Hook. flower parts, and the differentiation process of flower buds and leaf buds, the following items of leaves under flower buds and leaf buds at each differentiation stages are respectively measured: the contents of endogenous hormones like gibberellin ( GA3 ) , indolylacetic acid ( IAA), abscisic acid (ABA) and zeatin riboside (ZR), the contents of total sugar, total nitrogen, soluble protein, phosphorus, starch content, soluble sugar content,(α+β)-amylase activity,α-amylase activity andβ-amylase activity.The study, in the view of comparison theory, explores the relationship between flower buds differentiation and these physiological characters. The analysis indicates that:1. During the flower buds differentiation process, the contents of ABA,ZR, the ratios of ABA/GA3,ABA/IAA,ZR/GA3 and ZR/IAA in the leaves under flower buds were obviously higher than those in the leaves under leaf buds and showing a rising tendency while the contents of GA3 and IAA showing an opposite result and tendency. The contents of the above-mentioned four endogenous hormones and their ratio showed obvious maximum and minimum at the key stages of flower buds differentiation process. It is the evidence that the contents of these four hormones and their ratios play an important role in the differentiation process of Rhododendron moulmainense Hook. Higher content of ABA and ZR,or lower content of GA3 and IAA were benefical to its flower buds differentiation .2. During the flower buds differentiation process, the contents of total sugar, phosphorus and the ratios of C/N and P/N in leaves under flower buds was obviously higher than those in the leaves under leaf buds and showing a rising tendency while the contents of total nitrogen showing an opposite result. The contents of soluble protein in leaves under flower buds was higher than those in the leaves under leaf buds and showing a similar changing tendency and obvious maximum and minimum could be observed at the key differentiation stages. It is the evidence that the contents of these nutrients and their ratios play an important basic role in the flower buds differentiation of Rhododendron moulmainense Hook.Higher content of total sugar and phosphorus,or lower content of total nitrogen were benefical to its flower buds differentiation.3. During the flower buds differentiation process, the content of starch and soluble sugar in leaves under flower buds was higher than those in the leaves under leaf buds, and it had increasing tendency. However,(α+β)-amylase activity,α-amylase activity andβ-amylase activity got an opposite result. The content of all these carbohydrate and amylase showed obvious maximum and minimum at the key stages. Also, during the flower buds differentiation process, the ratio of starch content /soluble sugar content in leaves under flower bud was obviously higher than those in the leaves under leaf buds. These suggested that higher content of starch and soluble sugar were benefitcal to Rhododendron moulmai- nense Hook. flower bud differentiation,and starch played a more important role.