Figure 2

Early embryo development of Cyrtosia javanica . (A) The zygote has a dense cytoplasm and a prominent nucleus located at the chalazal end. (B) The first cell division of the zygote results in the formation of a terminal cell and a basal cell. In this species, the endosperm fails to develop, and one endosperm nucleus could be observed to stay beside the 2-celled embryo at the micropylar end in this light micrograph. (C) Light micrograph showing a further cell division (arrowhead) occurs at the basal cell of a proembryo. Two endosperm nuclei do not further develop and will soon degenerate. (D) Light micrograph showing a proembryo without a prominent suspensor differentiated. The antipodal cells are located at the chalazal end and densely stained. (E) An anticlinal division (arrowhead) occurs in the outmost cell layer, resulting in the formation of the globular-shape embryo. (F) Light micrograph showing an early globular embryo without a distinct suspensor structure. The chalazal accessory cells are distinguished from the adjacent cells of seed coat by their densely stained cytoplasm (arrowheads). Abbreviations: ant = antipodal cells; bc = basal cell; end = endosperm nuclei; IS = inner seed coat; OS = outer seed coat; syn = synergid; tc = terminal cell; zyg = zygote. Scale bar = 100 μm.