臭椿花器官分化的初步研究

利用扫描电镜(SEM)和光镜(LM)对臭椿花序及花器官的分化和发育进行了初步研究,表明:1)臭椿花器官分化于当年的4月初,为圆锥花序;2)分化顺序为花萼原基、花冠原基、雄蕊原基和雌蕊原基。5个萼片原基的发生不同步,并且呈螺旋状发生;5个花瓣原基几乎同步发生且其生长要比雄蕊原基缓慢;雄蕊10枚,两轮排列,每轮5个原基的分化基本是同步的;雌蕊5,其分化速度较快;3)在两性花植株中,5个心皮顶端粘合形成柱头和花柱,而在雄株中,5个心皮退化,只有雄蕊原基分化出花药和花丝。本研究着重观察了臭椿中雄花及两性花发育的过程中两性花向单性花的转变。结果表明,臭椿两性花及单性花的形成在花器官的各原基上是一致的(尽管时间上有差异),雌雄蕊原基同时出现在每一个花器官分化过程中,但是,可育性结构部分的形成取决于其原基是否分化成所应有的结构:雄蕊原基分化形成花药与花丝,雌蕊原基分化形成花柱、柱头和子房。臭椿单性花的形成是由于两性花中雌蕊原基的退化所造成,其机理有待于进一步研究。

Preliminary Study on Differentiation of Floral Organs of Ailanthus altissima (Simaroubaceae)

The investigation of the differentiation and development of inflorescences and flowers in Ailanthus altissima (Mill.) Swingle (Simaroubaceae) using light microscopy (LM) and scanning electron microscopy (SEM) suggests: 1) Flower bud differentiation of A.altissima occurs in early April on a panicle bearing many flowers; 2) The sequence of floral development proceeds from calyx primordia to corolla primordia to stamen primordia and finally to carpel primordia. Five sepal primordia are initiated spirally and asynchronously. Five petal primordia form nearly simultaneously and grow more slowly than the stamen primordia. The ten stamens are alternately arranged in two whorls; the two whorls develop simultaneously. The 5-carpellate gynoecium grows quickly. 3) In hermaphrodites, the five carpels adhere to each other to form the style and stigma; in staminate flowers, in late developmental stages, the five carpels are sterile and fertile stamens differentiate into anthers and filaments. In this paper, we focus on the morphological transition from bisexual to unisexual flower development in A.altissima. We observed that the primordia of staminate flowers are initiated in nearly the same way as in hermaphrodite flowers (although the time of initiation of each organ is different). The stamen and carpel primordia initiate simultaneously in both hermaphrodite and staminate flowers. The formation of reproductive structures is due to the differentiation in the course of development of the floral primordia that form the anthers and filaments and/or styles, stigmas, and ovaries. The formation of staminate flowers is due to suppression of the development of the gynoecium in A.altissima. The mechanism of transition from bisexual to unisexual flowers will only be clarified by further study.