大叶相思花部形态与开花生物学研究

Floral Morphology,Anthesis and Pistil Receptivity of Acacia auriculiformis A. Cunn. ex Benth.

对大叶相思（Acaciaaurieuliformis）栽培植株进行观察，用光学显微镜和扫描电子显微镜（SEM）对其花部形态和开花生物学特征进行研究。结果表明，大叶相思开花期为8—12月，穗状花序由114．9±11．9朵花组成，每朵花含124．1±16．5枚雄蕊，每雄蕊含有8粒16合花粉，单花花粉量为15885粒；雌蕊1枚，具14．4±1．8个胚珠，柱头凹陷，属于湿柱头类型。P／O值为1103．1；大叶相思花在夜间开放，开花可分为5个阶段。开花期间观察到雌蕊先于雄蕊伸出花冠和雄蕊先于雌蕊伸出花冠并存的现象，推测雌雄基本同熟。SEM观察花药在开花的第2阶段形成开裂线，第4阶段完全开裂并开始散粉。雄蕊于开花第1天的9：00～12：00大量散粉；雌蕊柱头在开花第1天上午出现分泌物，随后逐渐减少。开花后3～4d柱头开始凋零，柱头可授期约为3d，以开花第1天10：00之后的可授性最佳。

The floral biology of Acacia auriculiformis A. Curm. ex 13enth. was investigated in a seed orchard at Shadui Town, Jiangmen City, Guangdong Province with the flower morphology observed under light microscopy and scanning electron microscopy （SEM）. A. auriculiformis flowered from August to December. Its spike inflorescence consisted of 114.9 ± 11.9 flowers, bearing 124.1 ± 16.5 anthers in each flower. Within each anther existed eight pollen sacs, and eight polyads were produced with 16 pollen grains in each. It thus accounted of 15885 grains per flower. The pistil contained an average of 14.4 ± 1.8 ovules with a smooth, wet stigma and a solid style. Pollen to ovule ratio （P/O） was 1103.1. Anthesis normally began at night and the whole process of flowering could be divided into 5 stages. The phenomena that style emerged from flower bud before stamen and that stamen emerged firstly were all observed during anthesis at different trees, which was inferred that A. auriculiformis was homogamous. As observed under SEM, anther began to dehisce along dehiscent line at stage 2, and completely opened at stage 4. Abundant polyads were released between 9：00 and 12： 00. The stigma exudate emerged apparently during the first half-day after anthesis and then decreased gradually. Stigmas started to wilt at 3 -4 days after anthesis. The stigma receptivity lasted about 3 days and the peak of receptivity began after 10：00 at the first day.