药用植物商陆(Phytolacca acinosa Roxb.)根中异常次生结构的发育解剖学研究

本文报道了药用植物商陆根中异常次生结构的发生和发育过程。商陆根的初生结构和早期的次生结构都是正常的。但是,后来在维管柱的外围以离心的顺序先后产生5-7轮异常形成层.第一轮异常形成层起源于次生韧皮薄壁细胞和射线细胞。后一轮异常形成层在前一轮异常形成层向外产生的薄壁结合组织中发生。各轮异常形成层都以正常的活动方式产生同心环状排列的异常维管束以及它们之间丰富的薄壁结合组织,从而使根变成肉质状。薄壁结合组织细胞以及异常维管束内的薄壁组织细胞中贮藏有淀粉粒。

ANOMALOUS SECONDARY THICKENING IN THE ROOT OF MEDICINAL SPECIES OF PHYTOLACCA ACINOSA ROXB

Developmental studies nave been made of anomalous secondary thickening in the root of medicinal species of Fhytclacca acincsa Rcxb. in order to bring about the initiation and formation of the anomalous secondary vascular cylinder. It has been found that both the primary and the early secondary structures resemble those of most of the dicotyledons. Subsequently, 5-7 rings of anomalous cambia, however, develop in the outside of the vascular cylinder centrifugally. The first ring initials from the parenchyma and ray cells of the secondary phloem, and the succeeding ones arise periodically by periclinal divisions in a layer of parenchyma cells two or three cells beyond the outmost intact phloem derived from the current cambium. Each cambium forms a few of parenchyma cells on both sides before it forms derivatives into lignified xylem elements or conductive elements of the phloem. The parenchyma thus formed toward the outside later becomes the site of the origin of the succeeding cambium. The cambium produces fasicular strands, showing centrifugal differentiation of xylem and centripetal differentiation of phloem on opposite sides of the cambial layer, and parenchyma conjuctive cells between the fascicular areas. In both xylem and phloem the younger elemerts are closer to the cambium than the older ones. All the parenchyma conjuctive cells and parenchyma cells in the fascicular strands are rich in starch grains.