PLB 300 Lecture Notes - Lecture 27: Conifer Cone, Pollen Tube, Gametophyte

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5 Jan 2017
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Gametophytes of heterosporous seedless plants, and seed plants, are dependent of the sporophyte for their nutrition. The male gametophytes develop as pollen grains. In gymnosperms, water is not required as medium for transporting the sperm to the eggs. Instead, the partly developed microgametophyte, the pollen grain, is transferred bodily to the vicinity of a gametophyte within an ovule. After pollination, the endosporic microgametophyte produces a tubular outgrowth, the pollen tube. The microgametophytes of gymnosperms and other seed plants do not form antheridia: diagram and label a generalized gymnosperm seed (indicate the ploidy of all parts): integument, nucellus, embryo, female gametophyte, micropyle, pollen chamber. Seed plants produce one megaspore per megasporangium. Female gametophyte develops within megaspore and megasporangium. Female gametophyte + megasporangium + integument = ovule. Ovule stays on sporophyte parent until fertilization, and sporophyte embryo forms. Integument the outermost layer or layers of tissue enveloping the nucleus of the ovule: develops into the seed coat after fertilization.

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