Exam 4 Notes

Exam 4 Notes - Ch. 38 flowering plant reproduction...

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Ch. 38 flowering plant reproduction Angiosperms – alternation of generations, meiosis occurs in sporangia of sporophytes, spores divide by mitosis and develop into mature gametophytes, specialized gametophyte cells divide by mitosis to form gametes, gametes fuse during fertilization to produce a zygote, a sporophytes’ male reproductive structures: stamen: anther, filament, each anther contains multiple pollen sacs, microsporangia, each pollen sac contains multiple diploid microsporocytes, microspore mother cells, each microsporocyte divides by meiosis to produce 4 haploid microspores, each microspore divides once by mitosis to form an immature male gametophyte( pollen grain) a single tube cell encloses a single generative cell, the pollen grain matures into a adult male gametophyte when its generative cell divides by mitosis to produce two sperm, the adult male gametophyte is a fully mature, independent plant with only 3 cells, A sporophytes’ female reproductive structures: carpel, stigma, style, ovary, ovule, receptacle, each ovule contains a megasporangium, each megasporangium contains a megasporocyte, megaspore mother cell, a megasporocyte divides by meiosis to form 4 cells, only 1 of the 4 cells survives: the megaspore, the megaspore’s nucleus divides 3 times: giving 1 2 4 8 nuclei, membranes then partition the 8 nucleate immature gametophyte cell into 7 smaller cells, one with 2 nuclei, 1 is an egg, 1 cell with 2 polar nuclei, the other 5 cells degenerate, the 7 cells comprise the mature, double fertilization of angiosperms and independently derived in a few gymnosperms, a pollen grain disperses to a stigma, the tube cell grows into a pollen tube, the 2 sperm cells travel down the pollen tube to the embryo sac, 1 sperm fuses with the egg, 1 sperm fuses with the polar nuclei to form the first cell of the endosperm (triploid), Mechanisms used by plants to avoid self-fertilization; bi-sexual flowers also use: flowers with functional stamens and carpels that mature at different times, dioecious plants that produce plants that are male or female, structural barriers to pollination, e.g. pin vs. thrum flowers, genetic self- incompatibility, gauged by s-genes, (50-60 alleles, diploid plant gets 2 alleles), the first mitotic division of the zygote is asymmetric, the asymmetry provides the first environmental difference experienced by the differentiating cells and establishes the root-shoot axis, the sporophytes embryo develops from the zygote, the endosperm develops from the triploid endosperm nucleus, the ovule integuments become the seed coat, tissues of the ovary and sometimes the receptacle become the fruit, fruits aid in seed dispersal, the ovary wall becomes the fleshy part of the fruit, many dry fruits are wind dispersed, some dry fruits are animal dispersed, many fleshy fruits are animal dispersed, fruits aid in dispersal unless the animal becomes extinct, Development of the seed and fruit – eudicot embryos develop two cotyledons, monocot embryos
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This note was uploaded on 02/05/2011 for the course BIOL 1202 taught by Professor Gregg during the Spring '08 term at LSU.

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Exam 4 Notes - Ch. 38 flowering plant reproduction...

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