Abstract:

Embryological investigation was carried out on apomixis in Eulaliopsis binata (Rotz) C. E. Hubb by using paraffin section method. The results indicated that the development pattern of the embryo sac was apospory. In the early stage of the ovule development, a few of the nucellar cells developed into aposporous initial cells, which differentiated later into two forms of mature embryo sac: (1) one form of the mature embryo sac contained one egg cell, one synergid and two polar nuclei; (2) another form possessed one egg cell, two synergids and one polar nucleus. The former occupied about 67.6% and the later only 32.4%. The development pattern of the aposporous embryo sac resembled the Panicum type. Multiple initial cells of apospory might undergo development simultaneously to form two- or multiple-embryo sacs. The ratio of multiple mature embryo sacs in one ovule was 17.7%. No sexual embryo sac was found in the observed ovules. The genesis of the embryo could be classified into two types according to their initial time: (1) the pre-genesis embryo (74%), which originated from unreduced egg cell before the division of the polar nucleus, was observed at one to two days earlier than anthesis. (2) the late-genesis embryo (26%) which was observed at one or two days after anthesis and formation of free endosperm nuclei. The endosperm was derived from the polar nucleus or secondary nucleus without fertilization. The process of the embryonic development followed the sequence of the sexual embryo. The frequency of polyembryony observed was 13%.

Key words: apomixis, embryology, apospory, Eulaliopsis binata