Anatomical study on seed abortion of Syringa villosa under cultivated conditions

To better understand the aborted seed of cultivated Syringa villosa in Beijing, morphological and anatomical characteristics on both anther and embryo development during the sexual reproductive stage had been observed. The fruit set from artificial self-pollination and controlled emasculation was 0 while artificial cross pollination and open pollination were 31.86% and 8.32% respectively. S. villosa was a selfsterile plant under cultivated conditions and no viable seed was harvested. Anatomical observations indicated that the anther wall conformed to the basic type and glandular tapetum. The cytokinesis of the microspore mother cells in meiosis was the simultaneous type. The mature pollen grains were of 2-celled type. The ovule was anatropous, unitegmic and tenuinucellate. The development of embryo sac was the polygonum type. The endosperm developed to be the nuclear type and the embryo the asterad type. The globular embryo, heartshaped embryo, torpedo embryo and cotyledonal embryo were formed sequentially. But the development of cotyledonal embryo stopped and all cells degraded gradually at later stages, then the endosperm cells were deteriorated. The results indicated that microspore and megaspore, male and female gametophytes, pollination fertilization and early embryo development were normal, but the later embryo and endosperm growth stopped. Further studies should address these issues.