怀地黄块根的形态发生和结构发育

观察了怀地黄(Rehmannia glutinosa cv．Hueichingensis Hsiao．)块根的形态发生和生长发育过程中的形态结构变化。采用怀地黄的传统栽培方法，即用上一年的块根作母根进行繁殖，分别从母根和不定芽的茎基部发生不定根。怀地黄不定根的初生结构和维管形成层的发生与一般双子叶植物相同，但其次生生长却有两种方式，即正常次生生长和异常次生生长。一类不定根的形成层产生的次生结构与一般双子叶植物相同，即次生木质部中主要是导管，而薄壁细胞较少。这类不定根其次生生长为正常次生生长(normal secondary growth)，是担负吸收和固着作用的正常根。另一种类型的不定根，其形成层产生的次生木质部含有大量的薄壁细胞，少量的导管分散在薄壁细胞之间。这种次生生长为异常次生生长(anomalous secondary growth)，从而使不定根膨大，形成块根。因此，怀地黄的药用部分在起源和结构上都属于根的性质，其药用部分应称为块根。

Morphogenesis and structural development of the root tuber of Rehmannia glutinosa cv. Hueichingensis

The change of morpho and developmental process of the root tuber in Rehmannia glutinosa cv. Hueichingensis Hsiao were observed in this paper. The structural development of it was also studied with paraffin section. With the normal planting of Rehmannia glutinosa cv. Hueichingensis , adventitious roots generated from mother root tuber and the stem base of adventitious bud. The primary structure and the genesis of vascular cambium of the root tuber of Rehmannia glutinosa cv. Hueichingensis Hsiao were similar to those of normal dicotyledons. But there were two types of secondary growth, normal secondary growth and anomalous secondary growth. The former was similar to those of normal dicotyledons.The main components of its xylem were vessels.In this way the normal root was formed .The latter was anomalous. Main components of its xylem were parenchyma cells,few vessels scattered among them.This anomalous secondary growth formed the medicinal part of Rehmannia glutinosa cv. Hueichingensis ,which should be called as root tuber whether in the view of its generation or structure.