植物体的根和茎是相互连接的结构,共同组成植物体的体轴,但种子萌发时,胚根端发育为主根,胚芽端发育为主茎,二者之间通过胚轴相连。然而,根维管组织的初生结构的特点与茎维管组织的初生结构明显不同(根的初生维管组织为间隔排列,木质部为外始式;茎的初生维管组织为内外排列,木质部 Plant roots and stems are interconnected structure, together constitute the body axis of the plant body, but when the seeds germinate, the radicle root develops into the main root, embryo development of the main stem, the two connected by the hypocotyl. However, the primary structure of the root canal tissue is significantly different from that of the primary tissue of the stem and vasculature (the primary vascular tissue is arranged at intervals and the xylem is extrinsic; the primary vascular tissue of the stem is arranged both inside and outside, and the xylem