first leaves of plants
I don't know if it occurs in any other family, but orchids don't have any
cotyledons at all. The seeds are extremely tiny, and were evolved to be wind dispersed. There may be 3 million seeds in one orchid capsule. Orchid seeds don't have any endosperm. The only food they contain may be a couple of fat cells. When an orchid seed finds the right location & starts to germinate, it is invaded by a mycorrhiza, usually Rhizoctonia. The fungus provides the sugar needed by the baby seedling, & in the wild, the orchid plant has the mycorrhiza for the rest of its life. In cultivation, orchid seeds are germinated in sterile laboratory flasks on nutrient rich agar. Iris, Central NY, Zone 5a, Sunset Zone 40 "If we see light at the end of the tunnel, It's the light of the oncoming train." Robert Lowell (1917-1977) |
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