AUTECOLOGICAL STUDIES ON AUDOUINIA-CAPITATA (BRUNIACEAE) .6. NUTRITIONAL ASPECTS OF THE DEVELOPING OVULE

The present investigation provides a basis for studies about morpholog ical and nutritional aspects involved in late abortion of embryos and nutrient-linked, pre-emergent mortality of seedlings in this threatene d species. The nucellus is digested completely during megagametogenesi s and the integument likewise during embryogenesis, except for a dimin utive testa. Mass starch deposition is found in the mature embryo sac. Involvement of the persistent synergid in nutrition of the zygote and the 2-celled proembryo until the fifth week, is suggested. This funct ion is taken over by the suspensor which initially channels integument ary reserves to the developing proembryo. From the eighth week, spheri cal protein bodies are evident in the endosperm. At this stage, the em bryo proper is still surrounded by free nuclear endosperm, and the sus pensor of the linear proembryo mobilizes, in addition to integumentary reserves, also adjacent cellular endosperm as well as the micropylar layer of cellular endosperm. The embryo proper of the more advanced st ages mobilizes nutrients directly from the adjacent cellular endosperm . The seed enters dormancy at the heart-shape stage of embryo developm ent.