罗汉果花芽分化过程中形态及其激素水平变化特征

采用石蜡切片和酶联免疫法(ELISA)对罗汉果雄性、雌性、两性花芽分化过程的形态和激素水平变化进行观测,为罗汉果开花调控和品种选育提供科学依据。结果表明:(1)罗汉果雄性、雌性、两性花的花芽分化过程均可分为花芽未分化期、花芽分化初期、花序分化期、萼片原基分化期、花瓣原基分化期、雄蕊原基分化期和雌蕊原基分化期7个阶段。雄蕊原基分化期前,3种花芽分化过程无明显差异,各时期形态特征均依次为:茎端呈圆锥状(花芽未分化期)→茎端经半球形变成扁平状(花芽分化初期)→距茎端5~7节位处分化出穗状花序(花序分化期)→小花原基周围形成5个萼片原基(萼片原基分化期)→萼片原基内侧形成5个花瓣原基(花瓣原基分化期)。雄蕊和雌蕊原基分化期,3种花芽分化过程存在明显差异,雄蕊原基内侧出现雌蕊原基后,雄花芽雄蕊原基继续发育成雄蕊,雌蕊原基停滞生长,退为一个小突起;雌花芽雌蕊原基继续发育成雌蕊,雄蕊原基生长缓慢,退化为小花丝;两性花芽雌蕊和雄蕊原基均继续发育,形成外观正常的雌蕊和雄蕊。(2)内源激素脱落酸(ABA)、赤霉素(GAs)和玉米素核苷(ZR)含量在3种花芽分化过程中变化规律相似,即ABA含量在花芽生理分化期降低,花芽形态分化期升高,而GAs和ZR含量则基本保持不变;吲哚乙酸(IAA)含量在3种花芽分化过程中变化存在明显差异,雌花芽IAA含量在花芽生理分化期升高,花芽形态分化期逐渐降低,而雄性和两性花芽的IAA含量则基本保持不变。ABA/GAs、ABA/IAA、ZR/IAA和ZR/GAs激素含量比值在3种花芽分化过程中变化规律相似,ABA/GAs在花芽生理分化期降低,花芽形态分化期升高,而BA/IAA、ZR/IAA和ZR/GAs则基本保持不变。研究认为,罗汉果花芽分化过程经历一个"两性期",高ABA含量和ABA/GAs比值有利于罗汉果花芽分化,IAA可能对罗汉果花性分化具有重要作用。

Morphological and Endogenous Hormones Characteristics of Flower Bud of Siraitia grosvenorii during Its Differentiation

Morphological changes were observed by the paraffin section method,and the content changes of endogenous hormones were determined by ELISA for male,female and bisexual flower buds of Siraitia grosvenorii.The results showed that:First,the whole process of their flower bud differentiation could be divided into seven phases,including flower bud undifferentiation phase,flower bud initial differentiation phase,inflorescence differentiation phase,sepal primordial differentiation phase,petal primordial differentiation phase,stamen primordial differentiation phase and pistil primordial differentiation phase.Morphological characters of three kinds of flower buds were same before the stamen primordial differentiation phase,that stem apical were conical in flower bud undifferentiation phase,stem apical changed into flat from hemispherical in flower bud initial differentiation phase,spikes were initiated at 5-7 bits away from the stem apical in inflorescence differentiation phase,five sepal primordial were initiated around the small flower primordial in sepal primordial differentiation phase.While in the phase of stamen and pistil primordial differentiation,there were significant differences in morphological characters of the three kinds of flowers bud differentiation.After the pistil appeared inside of the stamen primordial,stamen primordial continued to develop into stamens and female primordial stopped growth then reduced to a small projection in male flower buds.The pistil primordial continued to develop into pistils and the stamen primordial grew slowly then reduced to small filaments in female flower buds.But,both the stamen and pistil primordial continued to develop into the normal stamens and pistils in bisexual flower buds.Second,the variations of endogenous hormones ABA,GAs and ZR contents were similar in the course of the three flower bud differentiation.ABA content decreased in flower bud physiological differentiation period and increased in flower bud morphological differentiation period,while the contents of GAs and ZR were maintained.There were significant differences of the IAA content in the course of the three flower bud differentiation,increased in flower bud physiological differentiation period and decreased in flower bud morphological differentiation period of the female flower buds,while the content was maintained in male and bisexual flower buds.The endogenous hormone ratios of ABA/GAs,ABA/IAA,ZR/IAA and ZR/GAs had the similar variation in the three kinds of flower bud differentiation.ABA/GAs decreased in flower bud physiological differentiation period and increased in flower bud morphological differentiation,while the ratios of BA/IAA,ZR/IAA and ZR/GAs were maintained.The studies suggested that the flower bud differentiation processed through hermaphrodite primordium phase,and high ABA content and the ratio of ABA/GAs were beneficial to flower bud differentiation in Siraitia grosvenorii.IAA possibly made an important role during sex differentiation of Siraitia grosvenorii.