Figure 3

Late embryo development of Cyrtosia javanica . (A) Light micrograph showing a longitudinal section through an early globular embryo with a differentiating protoderm layer (arrowhead). Several starch grains could be observed throughout the embryo cells after the periodic acid-Schiff’s (PAS) reaction. The chalazal accessory cells are distinguished from the adjacent cells of seed coat by their densely stained cytoplasm (arrowheads). (B) Light micrograph showing a further elongation of a globular embryo by the increase of cell number and the vacuolation. The chalazal accessory cells are distinguished from the adjacent cells of seed coat by their densely stained cytoplasm (arrowheads). (C) Light micrograph showing a maturing embryo. At this stage, there are a few starch grains persisted and they tend to congregate around the nucleus; numerous tiny protein bodies have accumulated within the embryo proper. (D) Light micrograph showing a longitudinal section through a mature seed. Many tiny protein bodies can be found within the embryo proper cells after the protein staining with amido black 10B. In this preparation, the lipid bodies are not preserved, the spaces (arrowhead) between the protein bodies are occupied by storage lipid bodies. (E) Nile red staining fluorescence micrograph of an orchid seed at the stage similar to Figure 3A. At the globular stage, the fluorescence outline is first detected in the surface of the embryo proper (arrow) and the outermost wall of the outmost layer of the inner seed coat (arrowhead). (F) Nile red staining fluorescence micrograph of a mature seed at the stage similar to Figure 3D. At maturity, the inner seed coat has compressed into a thin layer and attached the embryo tightly, and the surface of the embryo proper fluoresces brightly (arrow). Abbreviations: ant = antipodal cells; pb = protein body; sg = starch grain. Scale bar = 100 μm.