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Fig. 1 | Botanical Studies

Fig. 1

From: A perspective on orchid seed and protocorm development

Fig. 1

Shows the structural ontogeny of a shoot apical meristem in Epidendrum ibaguense. a At the time of seed germination, the embryo cells have abundant storage product deposits. b Within 96 h, storage products have been mobilized and cells are becoming vacuolated; judging from the cell profile of the apical layer, mitotic divisions have begun. c Approximately 7 days after germination, protocorms start to turn green, plastids become abundant with starch within protocorm cells. Protocorm cells at the future shoot pole, albeit smaller, have similar cytological features. d Soon after, future shoot meristem cells (arrowhead) can be identified as they are smaller in size and with a large nucleus to cytoplasm ratio. e The SAM initials (arrowhead) take on a square-shape and starch granules become less abundant. These features clearly mark the structural identity of SAM cells. f The SAM increases in size and starch granules remain less abundant when compare to the rest of the protocorm cells. In the peripheral region of the SAM, the cells (Asterisk) start to expand. g Continual expansion of peripheral meristem cells result in the formation of a protrusion; this results in the formation of a ‘dimple’ with the SAM cells (arrowhead) located at the depression. h The SAM continues to grow in size, surrounded by a developing leaf primordium. i The SAM in a mature plantlet takes on a slightly domed-shaped structure, forming leaf primordia at a regular interval. All scale bar = 50 µm

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