| The cells of root cap are separated into inner layers cells, outmost layers cells,detaching cells and detached cells in Zea mays. The results showed that the ultrastructure of detaching cells in root cap involved in programmed cell death (PCD). The outmost layers cells and detaching cells displayed typical characteristics in programmed cell death of cells: The change of chromatin was the regularly well-distributed state during detaching stage and then agglomerated and inclined to borderline,Mitochondrion were disorganized, Endoplasmic reticulum (ER) degenerated also, then became sections. The ultrastructure and substance transport function of Ectodesmata-like (ED-like) of the root cap cells, during the detaching stage, are reported by using fluorescence and electron microscopy. It was described the process that plasmodesmata (PD) were grudally stretched and broke into the ED-like. It was discoveredthat the diameter of appressed endoplasmic reticulum (AER) in PD became thinnerwhile the ED-like still remained some structures of PD. By using fluorescence probe incubating, 457Da Lucifer Yellow (LYCH) which was impermeable to the membrane, could enter the root cap cell through the ED-like. The results proved that theED-like still retained physiological activity and kept the symplastic transport function during a period time. When the root tissues were pretreated by cytochalasin D(CD), Phalloidin and 2,3-butanedione,2-monoxime (BDM) and then combined with fluorescence probe detecting, the results showed that actin and myosin may took part in the regulation of the symplastic translocation of the ED-like. Then treated withTRITC-phalloidin, the tests indicated that F-actin regulation of the permeability ofthe ED-like. Labeled with immuno-gold, we found that actin and myosin localized in the ED-like. And labeled of callose antibody, the gold granules accumulated gradually in the ED-like also, they were blocked finally by callose.
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