杜仲雌雄株细胞学,顶芽及叶含胶量的比较

杜仲（ＥｕｃｏｍｍｉａｕｌｍｏｉｄｅｓＯｌｉｖ．）为严格的雌雄异株植物，其雌雄株的比例近似于１：１，说明其性别可能由性染色体决定。但在形态上看不到特异的性染色体，雄株花粉母细胞整个减数分裂过程中，同源染色体的配对和分离是正常的。偶尔可发现个别细胞有染色体桥和环状或链状四价体。从１９９３年和１９９４年的１２月到翌年４月芽完全展开前对顶芽的测量说明，雄株顶芽的长度和最大直径都明显大于雌株的（Ｐ＜０．０１），而整个生长季节中雌株叶子的杜仲胶含量却明显高于雄株的（Ｐ＜０．０１）。不管雄株还是雌株，其叶的含胶量都随季节变化和叶子的长大而降低。实践证明可用芽的大小鉴别杜仲幼株的性别。

Comparison of Cytology, Apical Buds and Gutta Content Between Staminate and Pistillate of Eucommia ulmoides Trees

Eucommia ulmoides Oliv. is a typical dioecious species, a plant with an approximately equal pro-portion of the staminate and pistillate trees, suggesting that the gene responsible for sex determination could belocated on the sex chromosomes. Nevertheless heteromorphous sex chromosomes were not found in their ovaryand anther cells. Homologus chroosome pairing and division regularly occurred during meiosis of the pollenmother cells and occasionally chromosome bridges, chain and ring tetravalents were observed in a few cells.However, the length and maximum diameter of the apical buds in the staminate trees were significantly morethan those in the pistillate trees throughout the budding process from mid-December to mid-April (P < 0 .01 ).In contrast, the gutta content of the leaves in the pistillate trees was significantly much more than that in thestaminate trees (P < 0.01 ). And in both staminate and pistillate trees, however, the gutta content graduallydecreased, in the same proportion between the staminate and pistillate trees, from April to October with theseasonal change and the growth of leaves. These indicated that the size of the buds and the amount of the leafgutta content in E. ulmoides were sex dependant. Since both of the gutta content and bud-size were quantitative characters which were usually controlled by multiple genes unlikely being all located on the sex chromosomes, it might be possible that some of the important genes controlling these two charactere could be linkedwith the genes responsible for sex determination.