美洲黑杨次生维管组织发育的内在节律性与细胞内含物的动态变化

美洲黑杨（Populus deltoids）是一种重要的商业用材树种，在我国多用作胶合板和纸浆原料，其速生性的特点也很早为人们所认识。众所周知，树木次生维管组织的发育具有内在的节律性，与此同时维管组织的细胞内含物也会发生动态变化。利用电镜技术及细胞化学方法，研究了美洲黑杨次生维管组织的发育以及细胞内含物分布的变化，发现次生维管组织的发育具有内在节律性，在年周期中表现为分化期和休眠期交替出现，次生韧皮部与次生木质部交替分化形成。在维管组织发育过程中，早期蛋白质和脂类物质首先减少，然后淀粉粒解体消失，发育期内维管组织的蛋白质、脂类和淀粉的积累最少，休眠期内维管组织细胞内最早出现淀粉的积累，然后蛋白质和脂类物质积累大大增加。杨树维管组织发育过程的内在节律性与细胞内含物的动态变化密切相关。

Developmental Inherent Rhythm and Dynamic Changes in Cell Ergastic Substances of Secondary Vascular Tissues in Populus deltoids

The eastern cottonwood Populus deltoids is an important commercial timber species used for saw-timber, veneer and pulpwood in China. The fast-growing character of P. deltoids has been remarkable for a long time. It is well known that the developmental inherent rhythm occurs during the development of secondary vascular tissue. Synchronously, the cell ergastic substance shows dynamic changes. Using electronic microscopy and cytochemical methods, we studied the distribution changes of the cell ergastic substance and development of secondary vascular tissues. Development of secondary vascular tissue took on an inherent rhythm, showing alternation of dormant and differentiated stages in periodicity of one year, and the formation of secondary phloem and xylem was alternate. In earlier stages, the protein and lipid decreased first. Then the starch grain disaggregated. The accumulation of starch grain, protein and lipid was the least during the development stage of vascular tissue. In the dormant stage, starch grain appeared at the beginning; later on, the accumulation of protein and lipid increased enormously. The distribution of cell ergastic substance was closely related to the developmental inherent rhythm of secondary vascular tissue.