UNIT 4 Sexual ReproductionMeiosisproduces haploid cells from diploid cellsFertilizationrestores diploidy by the fusion of two hapcells (gametes) into a diploid cell.sporeshaploid cells produced by meiosisgametophytegametes eithereggs or spermsTwo kinds of spores:Microsporesanthers of flowersMegasporesfrom immature seeds (ovules)Ex. Lily→3 of 4 megaspores disintegrate leaving behind afunctional megaspore→nucleus divides by mitosis3x→8 free nucleiPollination:sexual reproduction in floweringplants; transfer of pollen grains from ananther to the receptive region of apistil.Stigma:receptive surface for pollen grainsStyle:conducts pollen tubes to the ovary andraises the stigma to a receptive positionOvaryformation of ovulesPollination andFertilizationPollen grain reaches thestigma→germinates→pollentubes (tube cell)Generative cell:divides and generates two spermcells→move through the tube to asmall opening in an ovuleDoublefertilizationfirst sperm fertilizes the egg andsecond sperm moves to the polar nucleiand fuses with themSelf PollinationInvolves only one flower,Pollen grains from the anther falldirectly onto the stigma of the sameflowerCrossPollinationMore complex, Involves transferof pollen from the anther of oneflowertothestigmaofadifferent flowerFloral shootdoes not have an apical meristem thatgrows continuouslyReceptacleregion of the flower shoot where theflower parts are attached.
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- Summer '17
- Pollination, Plant morphology, Pollen, corolla