Structural characteristics of the mature embryo sac of Camellia oleifera

The ovule is the most important reproductive organ in the pistil of phanerogamae. Camellia oleifera (Theaceae) is an important woody plant producing edible oil in southern China, and its embryo sac structure has a positive effect on seed breeding. In this study, the microstructure, ultrastructure and three‐dimensional structure of the ovule and embryo sac of C. oleifera were observed and described based on a combination of advanced microscopy techniques (SEM, TEM, CLSM). The ovule comprises the inner and outer integument. Large quantities of secretions in the micropylar canal exit and may participate in the guidance of the entry of the pollen tube into the embryo sac. The synergids have a dense cytoplasm, abundant organelles, and strong polarity. Little cytoplasm is present in the egg cell, yet there are many vacuoles. The center of the cell is taken up by a large vacuole, and the cytoplasm is pushed towards the edges to form obvious cytoplasmic cords. The two polar nuclei are large and conspicuous. The antipodal cells degenerate to fulfill a nutritional function.