杉木小孢子叶球发育过程中形态结构变化

以扬州地区生长的成年杉木为实验材料，通过采用数码相机拍摄、体视镜、扫描电镜以及半薄切片等方法，对杉木小孢子叶球发育、小孢子囊发育及其散粉规律进行详细观察。结果发现，10月中旬，杉木小孢子叶球形成并着生于新枝顶端。翌年3月中下旬，小孢子叶球成熟，进入散粉期，散粉首先从小孢子叶球基部开始依次向上部扩散。小孢子叶在孢子叶球主轴上螺旋排列，单个小孢子叶通常由3个小孢子囊组成，构成三角形。小孢子囊壁由1层表皮细胞、1~2层中间层细胞和1层绒毡层细胞组成，表皮细胞首先形成，并向内分化出2~3层细胞，分别分化形成中层和绒毡层，最后中层和绒毡层消失。杉木的小孢子囊通过开裂口控制其开裂，20℃室温下整个小孢子叶球散粉时间持续约18 h，单个小孢子叶的散粉时间为8~10 h。以上结果显示，杉木小孢子叶球的发育过程经历了体积增大、鳞片开张及散粉等阶段，这些形态和结构上的变化利于提高散粉效率，这说明杉木在长期的演化过程中，形成了许多有利于风媒传粉的结构特征。

Morphological and Structural Changes during Male Cones Development in Cunninghamia lanceolata

We selected the Chinese fir from Yangzhou as experimental materials, and studied the development of male cones, microsporangium development and the rule of pollens release in detail using digital camera, stereoscope, scanning electron microscopy(SEM), and semi-thin section. The male cones were formed in mid-October, and matured in the following late March. During the pollination period, pollens began to release in the middle of the slit dehisced from the base of the male cones to the upper part. The male cones were borne at the top of the shoots. The cones enlarged with the scales opened when they were maturing. Microsporophylls were arranged spirally along the main axis, and each microsporophyll consists of three microsporangia forming a triangle. The microsporangia wall was composed of epidermis, endothecium and tapetum. Epidermis cells occurred first and differentiated into 2-3 layers of cells which formed the endothecium and the tapetum. Finally, the endothecium and tapetum disappeared. At room temperature, the duration of pollen release for one male cone was about 18 h and about 8-10 h for one microsporangium. The results indicated that the development process of the microspore leaves of Chinese fir had experienced the increase of volume, scale opening and pollen release. These morphological and structural changes were beneficial to improve the efficiency of pollen release, which indicated that the Chinese fir formed many structural characteristics conducive to the wind pollination.