J Integr Plant Biol. ›› 1993, Vol. 35 ›› Issue (4): -.

• Research Articles •    

Embryological Studies in Rheum palmatum L.

Chen Chao and Wang Yao-zhi   

Abstract: Embryology of Rheum palmatum L. has been studied. The main results are as follows. 1. The anther is four sporangiate with monoor multicellular archesporium. The development of anther walls conforms to the monocotyledonous type. The cells of the glandular tapetum become two nuclei in the later stage. The microsporocyte undergoes simultaneous meiotic division and produces tetrahedral tetrad. The pollen grains with three furrows are shed at the 3-celled stage. 2. The ovary is unilocular and contains only one ovule, bitegmic and crassinucellate. The micropyle is formed by the inner integument. The develoment of embryo sac conforms to the Polygonurn type. The single hypodermal cell in nucellus functions as archesporium. The megaspore mother cell undergoes meiosis to form a linear or T-shaped tetrad. Only the chalazal megaspore functions and forms the female gametophyte, whereas the other three degenerate. Two polar nuclei fuse before fertilization takes place. Three antipodal cells persist up to globular embryo stage. 3. The endosperm is of nuclear type. Endosperm nuclei form cells since the later stage of the globular embryo. However the chalazal endosperm nuclei do not form cells. They form a free nuclei endosperm haustorium. The phenomenon of free nuclei fusion has found in the haustorium and other part of the embryo sac. The development of embryo belongs to the Asterad type and the embryo has a small suspensor. 4. The hypostase appears at the stage of the mature embryo sac. It persists for a long time and only leaves a trace at the organized embryo stage.

Key words: Rheum palmatum L., Male gametophyte, Female gametophyte, Embryo, Endosperm, Hypostase

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