Fig. 1

HYPERLINK "sps:id::fig1||locator::gr1||MediaObject::0"The ovule and seed development of Epidendrum ibaguense. A The archesporial cell enlarges and differentiates into the megasporocyte and is enveloped by a single layer of nucellar cells (arrowhead). At the same time, both the inner (*) and outer (arrow) integuments have developed. Scale bar = 20 μm. B A mature embryo sac (arrowhead) showing the egg apparatus. The inner integument (*) is well developed at the micropylar end, forming the micropyle. The outer integument has extended beyond the inner integument as the ovule matures. Scale bar = 50 μm. C After fertilization, the zygote (arrowhead) has a dense cytoplasm with a prominent nucleus and some starch deposits (small red dots). The inner integumentary cells (*) at the micropylar end become densely cytoplasmic; each cell has a distinct nucleus. The walls of the inner integumentary cell thicken, and wall ingrowths are present. Scale bar = 20 μm. D A lower magnification micrograph giving a general overview of the contrasting staining intensity between the inner and outer integuments. The fertilized ovule and the inner integument have a stronger staining intensity compared to the vacuolated outer integumentary cells. Scale bar = 150 μm. E A narrow funiculus connects the developing seed to the maternal placental tissue. Mitotic activity (arrowhead) can be discerned at the time of fertilization. Scale bar = 40 μm. F As the proembryo increases in size and the suspensor begins to protrude beyond the opening of the inner seed coat, the cells of the inner seed coat (arrowhead) gradually become compressed. Scale bar = 50 μm. G The embryo continues to increase in size. As a result, the inner seed coat is crushed, and only remnants (arrowhead) remain adhering to the embryo proper. Scale bar = 50 μm. H Light micrograph showing a portion of the suspensor (arrowhead) pressing against the walls of the seed coat cells. The inner layers of the seed coat stain purple with the TBO stain, indicating the absence of phenolic compounds in the walls. Scale bar = 10 μm. I Fewer mitotic divisions in the inner chalazal cells result in creating a cavity (*) during seed development. Scale bar = 60 μm. J Light micrograph showing a TBO-stained section of a mature seed coat (arrowhead). Judging from the staining reaction, there is a preferential deposition of lignin in the seed coat's inner periclinal and radial walls. Scale bar = 50 μm