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Life Cycle of Flowering Plants Compare Fig. 41.2 Pg. 824 http://www.bakerlite.co.uk/pics/Wales/South%20Wales/Vale/Trees/Tree-8.jpg SYNGAMY zygote Sporophyte Gametophyte sporangium sporocyte spores gametangia gametes germination mitosis differentiation 1N 2N MEIOSIS The flowering plant is a multicellular diploid sporophyte. The sporophyte encloses the multicellular haploid gametophyte. The life history is thus diplohaplontic. The gametes are oogamous but the sperm lack flagellae. Gender expression has moved from gametophyte to sporophyte.

Flower Organization-building a flower from the bottom up! Compare Fig. 41.4a Pg. 826 Flower Organization-building a flower from the bottom up! A flower is a short shoot (stem with leaves) The stem is the receptacle with very short internodes The leaves appear in four whorls stigma carpel gynoecium flower perfect style locule ovary anther superior stamen ovule pollen filament androecium flower hypogynous petal corolla receptacle sepal complete perianth calyx pedicel

Microsporogenesis: Prophase I of Meiosis http://images.iasprr.org/lily/lpachy-m.jpg

Microsporogenesis: Late Prophase I of Meiosis Synapsis: homologs join Recombination: crossing over http://images.iasprr.org/lily/lepto.jpg

Microsporogenesis: Metaphase I of Meiosis http://images.iasprr.org/lily/meta-i.jpg

Microsporogenesis: Anaphase I of Meiosis Centromeres do not breakdown Homologs are separated: not sister chromatids http://images.iasprr.org/lily/anaph.jpg

Microsporogenesis: Telophase I of Meiosis Already haploid but sister chromatids still joined http://images.iasprr.org/lily/telo-i.jpg

Microsporogenesis: Metaphase II and Anaphase II of Meiosis http://images.iasprr.org/lily/meta-ii.jpg

Microsporogenesis: Telophase II of Meiosis http://images.iasprr.org/lily/telo-ii.jpg

Microsporogenesis: Meiosis complete (but prophase of mitosis) http://images.iasprr.org/lily/tetrad.jpg

Microsporogenesis: Completed, Separated Microspores (note prophase) http://images.iasprr.org/lily/microsp.jpg

Pollen Grain: Mitosis Makes Endosporic Microgametophyte Pollen Wall: Microspore Wall (allergenic?) Tube Cell Nucleus Cytoplasm Generative Cell Nucleus Cytoplasm The tube cell digests a path from the stigma to the egg. The generative cell follows the path to the egg, and divides to make two sperm cells. Both participate in syngamy. http://images.iasprr.org/lily/pollen2.jpg Pollination: vector-assisted movement of the pollen grain from the anther to the stigma. Compare Fig. 41.8 Pg. 829

The tube cell germinates through the pollen wall. Pollen Tube Growth The tube cell germinates through the pollen wall. The cell grows chemotropically toward the egg. The pollen tube must find the ovule’s micropyle. The generative cell slides along this tube. It divides by mitosis to form two sperm cells. http://bilbo.bio.purdue.edu/~cjslab/pollen-tubes.jpg

Life Cycle of Flowering Plants http://www.bakerlite.co.uk/pics/Wales/South%20Wales/Vale/Trees/Tree-8.jpg sperm cells SYNGAMY zygote Sporophyte Gametophyte sporangium sporocyte spores gametangia gametes germination mitosis differentiation 1N 2N MEIOSIS pollen grain tube cell generative cell anther microspore The large plant is a sporophyte. Its flower produces the sporangia; on the male side, the anther of the stamen The anther contains sporocytes that divide by meiosis to make spores The spore cell divides to make an endosporic microgametophyte… a pollen grain The tube cell digests a path to the egg The generative cell divides into two sperm cells that participate in syngamy

Compare Fig. 41.4a Pg. 826 Flower Organization Now we focus on what is happening on the female side… We will examine what is going on inside the ovule of the carpel. stigma carpel gynoecium androecium filament anther stamen flower perfect flower hypogynous pollen style locule ovary superior ovule petal corolla calyx sepal pedicel receptacle complete perianth

Alstroemeria: What is different two weeks later? Bisexual …but functionally unisexual …by being trans-sexual protandrous: first-male protogynous: first-female (antonym)

Megasporogenesis: taking place inside the ovule inside the ovary. megasporocyte 4 megaspores meiosis I meiosis II 3 disintegrate functional megaspore mitotic divisions without cytokinesis megagametophyte 3 antipodals central cell egg cytokinesis 2 synergids Compare Fig. 41.7 Pg. 828 and Fig. 41.11 Pg. 832

Life Cycle of Flowering Plants http://www.bakerlite.co.uk/pics/Wales/South%20Wales/Vale/Trees/Tree-8.jpg central cell egg SYNGAMY zygote Sporophyte Gametophyte sporangium sporocyte spores gametangia gametes germination mitosis differentiation 1N 2N MEIOSIS embryo sac ovule antipodals synergids megasporocyte The large plant is a sporophyte. Its flower produces the sporangia; on the female side, the ovule of the carpel The ovule contains a megasporocyte that divides by meiosis to make four megaspores Three megaspores disintegrate. The remaining megaspore cell divides by mitosis to make 8 nuclei. Cytokinesis divides the 8 nuclei into seven cells of the megagametophyte (embryo sac) The egg cell and the central cell are gametes that fuse with two sperm cells in syngamy The ovule, with zygotic embryo and triploid endosperm, becomes a seed.

karyogamy! In Flowering Plants, syngamy is a double event: syngamy#2: Compare Fig. 41.11 Pg. 832 In Flowering Plants, syngamy is a double event: syngamy#2: 2 x 1N polar nuclei + 1N sperm = 3N primary endosperm cell sperm nuclei no miracle-grow, no compost! 1N egg + 1N sperm = 2N zygote syngamy#1: synergids disintegrating In this slide, plasmogamy has already occurred…but what part of syngamy has not occurred yet? karyogamy! http://botit.botany.wisc.edu/courses/img/Botany_130/Diversity/Angiosperms/Fertilization.jpg