Development Anatomy on the Root Tuber of Cultivated Pseudostellaria heterophylla

The developmental process of the spindle-shaped root tuber of Pseudostellaria heterophylla was studied by paraffin sectioning.It was shown that the root tuber of cultivated P.heterophylla was originated from adventitious root.The development of P.heterophylla adventitious root included four developmental stages,promeristem,primary meristem,primary structure and secondary structure stages,and was similar to that of other herbaceous dicotyledons.The cortex cells of primary structure were 3~4 layers,which volume was large.The endodermis had clear casparian strips.Primary xylem was triarch in most cases,and it was diarch,tetrarch and pentrarch in less cases.80% of secondary structure areas were formed by secondary xylem which composited by parenchyma cells mostly.The vessel scatteredly distributed among the parenchyma cells.It was shown that the different activities of vascular cambium from top to tail of the root led the different diameters of it,so that the root became the spindle-shaped root tuber.The area and cell layers of different parts from top to tail of roots were statistical analyzed.In the experiment of periodic acid-Schiff reaction,the starch grains were stored in the parenchyma cells of the secondary phloem and between the vascular rays of secondary xylem.The clustered crystal of calcium oxalate was also observed in the parenchyma cells in the secondary xylem.