Abstract:

 Taking male，female and hermaphrodite flower of 3 kinds of watermelon（Citrullus lanatus）sexual type as material， we made these flower buds at different development stages into paraffin section for cytomorphological observation．The result showed that the floral primordial processes of these 3 kinds of sexual type from watermelon had no visible differences. At the end of hermaphroditic stage，the length of flower bud was about 0.8-1.0 mm and the differentiation development of male，female and hermaphrodite flower began. Stamen primordia volume of male and hermaphrodite flower augmented rapidly，and carpel primordia of female and hermaphrodite flower began to differentiate into stigma and ovary．In deformity female flower，the base of carpel primordia would stop the development after denting to a certain degree，while the stamen primordia would not stop elongation and continue to develop to form the mature stamen with small amount of mature pollen grains.

Key words: Watermelon, Sex differentiation, Cytomorphological observation

摘要：

以西瓜 3 种性型（雌雄异花同株系、全雌系和完全花雄花系）的雄花、雌花和完全花 3 种花芽为材料，制成石蜡切片，进行西瓜花芽不同发育时期的细胞形态学观察。结果表明：西瓜 3 种性型之间性别分化起始及同种性别之间花器官发育过程并没有明显的形态学差异。雄花、雌花和完全花 3 种花芽分化首先要经过一个两性期，即雄蕊原基和雌蕊原基同时存在时期，在两性期之前三者不存在明显的形态学差异；当花芽长度为0.8～1.0 mm时两性期结束，开始雄花、雌花和完全花的差异发育，此后雄花和完全花的雄蕊原基快速增大，雌花和完全花的雌蕊原基开始分化为柱头和子房。在 3 种花芽发育过程中，完全花的花芽在两性期后明显比同时期的雄花、雌花的花芽长度更长。全雌系中的“畸形雌花”出现在两性期后，雌蕊原基的凹陷发育过程受阻，而本该停止发育的雄蕊原基继续分化，最终发育成可产生少量成熟花粉粒的雄蕊。