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Hypogeal germination (Greek: ὑπόγαιος/ὑπόγειος ''hypógaios/hypógeios'' = 'below ground', from ὑπό ''hypo'' = 'below', γῆ ''gè'' = 'earth/ground') is a botanical term indicating that the germination of a plant takes place below the ground. An example of a plant with hypogeal germination is the pea (''Pisum sativum''). The opposite of hypogeal is epigeal (above-ground germination). ==Germination== Hypogeal germination implies that the cotyledons stay below the ground. The epicotyl (part of the stem above the cotyledon) grows, while the hypocotyl (part of the stem below the cotyledon) stays the same length. In this way, the epicotyl pushes the plumule above the ground. Normally, the cotyledon is fleshy, and contains many nutrients that are used for germination. No photosynthesis takes place within the cotyledon.〔Parolin, P., Ferreira, L.V., Junk, W.J. (2003) ("Germination characteristics and establishment of trees from central Amazonian flood plains" ) ''Tropical Ecology'' 44(2): 157-169〕 The seeds are much bigger than those of plants with epigeal germination. Because the cotyledon stays below the ground, it is much less vulnerable to for example night-frost 〔Rigetti, S. (1998) ''(Weed control in direct-seeded pea and lentil )'' University of Saskatchewan〕 or grazing. The evolutionary strategy is that the plant produces a relatively low number of seeds, but each seed has a bigger chance of surviving. Plants that show hypogeal germination need relatively little in the way of external nutrients to grow, therefore they are more frequent on nutrient-poor soils. The plants also need less sunlight, so they can be found more often in the middle of forests, where there is much competition to reach the sunlight.〔 Plants that show hypogeal germination grow relatively slow, especially in the first phase. In areas that are regularly flooded, they need more time between floodings to develop. On the other hand, they are more resistant when a flooding takes place.〔 After the slower first phase, the plant develops faster than plants that show epigeal germination. It is possible that within the same genus one species shows hypogeal germination while another species shows epigeal germination. Some genera in which this happens are: *''Phaseolus'': the runner bean (''Phaseolus coccineus'') shows hypogeal germination, whereas the common bean (''Phaseolus vulgaris'') shows epigeal germination *''Lilium'': see Lily seed germination types *''Araucaria'': species in the section ''Araucaria'' show hypogeal germination, whereas species in the section ''Eutacta'' show epigeal germination 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「hypogeal germination」の詳細全文を読む スポンサード リンク
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