BIOL120 Lecture Notes - Lecture 10: Sporophyte, Gametophyte, Embryogenesis
16 Oct 2014
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Postulated to enhance adaptability to changing environments and facilitates colonization of new environments: all plants have two multicellular forms (gametophyte 1n, and sporophyte 2n, bryophytes are gametophyte dominant, seedless vascular plants are sporophyte dominant but they are independent of each other, seed plants are sporophyte dominant and the gametophyte is significantly reduced. Body cell eventually produces two sperm cells: one tube: produces pollen tube, pollen lands on drops of fluid produced by megasporangium on each ovulate scale, evaporation brings pollen through micropyle into contact with megasporangium where it germinates, germination of pollen stimulates the development of megasporocyte. Angiosperm reproduction: microsporogenesis: anther produces microsporocytes, each microsporocyte undergoes meiosis giving rise to four haploid microspores, microspore grows into pollen grain (microgametophyte, mature pollen grain is reduced to two or three cells (four in gymnosperms, tube cell produces pollen tube, generative cell gives rise to two sperm.
