银杏花粉萌发生长与分枝式花粉管形成的观察

本研究采用半薄切片法和扫描电镜等技术对银杏（Ginkgo bilobaL.）花粉管的体内萌发与生长以及花粉的离体培养进行了观察,结果表明：（1）银杏花粉粒通过传粉滴收缩后到达胚珠珠孔处,并经珠孔道进入贮粉室内停留,约7 d后花粉粒开始萌发;（2）贮粉室内的花粉最初萌发出的花粉管与花粉粒的四细胞轴几乎垂直,表现出明显的侧向萌发特征。初始花粉管在贮粉室内的生长方向无规律,有的通过一定的贮粉室空间向较远的珠心组织细胞间隙生长,有的直接进到较近的珠心组织细胞间隙,花粉管的生长不损伤珠心组织细胞;（3）花粉离体培养过程中会迅速发生水合作用,花粉粒由船形变为圆球形。48 h后花粉外壁脱落,管细胞膨大,花粉管自管细胞膨大处萌发。随着花粉管的生长,管细胞核移动进入花粉管内,而生殖细胞仍留在花粉粒内。伸长的花粉管可分为淀粉粒区和透明区,花粉管末端易形成多种类型的分枝。花粉管内原生质呈喷泉状流动。

Observation of pollen germination and pollen tube growth of Ginkgo biloba L.

While the pollen germination and pollen tube growth of flowering plants have been well studied, the knowledge of early gymnosperm Ginkgo biloba is little understood. Here, we describe the process of pollen germination and pollen tube growth of Ginkgo biloba in vivo and in vitro by using semi-thin section techniques and scanning election microscope(SEM) . The results show the following.(1) Pollen grains moved into pollen chamber passing through micropylar and micropylar canal with the contraction of pollination drop. About 7 days later, pollen began to germinate after a series of changes of development in the pollen chamber. (2) The initial pollen tube was vertical to the axial row of four cells indicating that the pollen germination in the pollen chamber was lateral germination. Then pollen tubes grow in irregular directions within the pollen chamber by penetrating into intercellular space near or away from the nucellus, and no severe displacement of nucellar cells by the growth of pollen tube. In a small quantity of pollen grains, soon after the tube cells swelled, the pollen tubes began to produce branch at the apex. (3) In vitro culture, the fusiform shape of the pollens changed into round shape rapidly by hydration. At about 48 h after culture, pollen germination occurred in the enlargement of tube cell after the shedding of pollen exine. During tube growth, the tube cell nucleus moved into the elongating tube, and the generative cells remained within the pollen grain. There are two distinct areas in elongating pollen tubes. One is at the proximal pollen, containing abounding starch grains. The other is the transparent area at the distal part, lacking of starch grains. The tips of elongating pollen tubes form various types of branches. The cytoplasmic streaming type in the tube cell is a regular fountain like pattern, with cytoplasm moving towards the tip in the center of the tube and return from the tip along the tube wall.