掌叶大黄胚珠的发育及胼胝质的变化

OVULE DEVELOPMENT AND CALLOSE DEPOSITION IN RHEUM PALMATUM

Using Ehrlich' s hematoxylin whole stain and resin thin sections, the development of ovule and embryo sac in rhubarb was studied, the main results were as follows: 1 . The tetrad of megaspore is T-or linear shaped and the chalazal megaspore develops into a Polygo num type embryo sac. In mature embryo sac, two polar nuclei fused shortly after moving to the centre. Three antipodal cells can be seen before and after fertilization. 2 . Styles are hollow type with narrow stylar canal. An obturator-like structure formed at the base of the stylar canal. At the mature embryo sac stage, some nucellar cells at the chalazal region differentiated into hypostase. 3. During meiosis, callose deposit on the micropylar end wall of the megasporocyte, but the cell was not enclosed by callose. On the cross-walls of dyda and tetrad, callose also deposit richly. On the contrary, callose can never be seen on the chalazal end, but on the walls of some chalazal nucellar cells.