實(shí)驗(yàn)花的構(gòu)造ppt課件(參考版)
2025-05-06 22:07本頁(yè)面
【正文】 the larger tube cell, which contains the gen erative cell, will form the pollen tube. The round structure above the generative cell is the tube cell nucleus, with its redstained nucleolus. Mature pollen grainsthreecelled male gametophytes of the telegraph plallt, Silphium (family Asteraceae). Prior to pollination, each pollen grain contains two filamentous sperm cells, which are suspended in the cytoplasm of the larger tube cell. In other words, the pollen of Silphium is shed at the threecelled stage, whereas that of Lilium, shown in the preceding figure, is shed at the twocelled stage. 側(cè)膜胎座 中軸胎座 特立中央胎座 Lilium. Some stages in development of all ovule and embryo sac. (a) Two young ovules, each with a single, large mega sporocyte. Integuments have not begun to develop. (b) Ovule now has integu ments. The megasporocyte is in the first prophase of meiosis. (c) Ovule with eightnucleate embryo sac (only six of tile nuclei can be seen here, two at the chalazal end and four at the micropylar end). The polar nuclei have not yet migrated to the center of the sac. 五、種子 Seed 種皮 Seed coat 胚 embryo 胚乳 endosperm
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