巴西橡胶树初生乳管分化与苗生长的关系

Primary Laticifer Differentiation of Hevea brasiliensis in Relation to Shoot Growth

利用巴西橡胶树无性系热研７－３３－９７苗圃芽接幼树为材料，采用光学显微镜技术和电子显微镜技术研究了初生乳管分化与茎叶发育的关系。研究结果表明，苗端最初的乳管的分化和原形成束的分化相伴发生，这些乳管出现在原形成束附近，束的近轴一侧。但是当维管形成层形成时，束间形成层在初生乳管的近轴一侧产生，因而随着次生形成层的活动，初生乳管被定位于次生韧皮部远轴一侧。茎和叶中的初生乳管系统和初生维管系统一样连接成一个整体。最初形成的初生乳管是有节连接乳管，随后这些乳管侧壁向各个方向发生侵入生长，互相连接成为一个不规则的立体网状结构。在一个叶蓬生长过程中，茎和叶柄横切面上初生乳管的数目在芽萌动至叶古铜期期间迅速增加，到叶淡绿期增长基本停止。在差不多经历一个生长季的茎部，才产生次生乳管。当次生乳管出现时，初生乳管由于茎的次生加粗而被拉伸，同时这些乳管在茎组织中分布的密度减少。笔者假定，这种正在变老的初生乳管会产生导致次生乳管分化的信息。

Primary laticifer differentiation of rubber trees Clone RY 7 -33 -97 (Hevea brasiliensis Mull. Arg.) was studied by using optical and electron microscopy. The samples were collected from young budding plants in nursery. It was shown that the first laticifers in shoot tip were differentiated in company with the procambium strands and that the laticifers appeared near the strands and on the adaxial side of the strands. As the vascular cambium was initiated, the interfascicular cambium was formed on the adaxial side of secondary phloem produced by the cambium. like primary vascular system, the primary laticifer system between stem and leaves was connected as a whole. The laticifer anasta- mosing was articulated. Following intrusive growth at lateral wall of the laticifers in varied directions, they connected each other into a three-dimensional network. In a growth flush of shoot, the laticifer number in the transections of the stem and petiole increased rapidly during the period from bud germination to bronze--coloured leaf appearance, and stopped increasing when the leaves became light green. The secondary laticifers were formed in the stem that had grown almost for a growth season. At that time the primary laticifers were stretched and their density in the tissues became low in response to the increase in circumference of stem. It was supposed that the aging primary laticifers would produce signals to induce the differentiation of the secondary laticifers.