Biol 240w 1st Edition Lecture 11Outline of Last Lecture General Characteristics of TransportOsmosisWater PotentialLong Distance Transport - Bulk FlowTransport Through PhloemOutline of Current Lecture Alternation of GenerationsFlower Structure and FunctionDevelopment of GametophytesDevelopment of Embryo SacsDevelopment of Pollen GrainsPollinationCurrent LectureAlternation of GenerationsDescribes plant life cycleSporophyte generationWhat is generally seen when observing a plantDiploid plantProduces haploid spores by meiosis when a signal is received to start reproductionGametophyte generationHaploid spores divide by mitosis to form male and female gametesFertilization results in diploid zygotes, which form new sporophytes by dividing by mitosisGametophyte development ( Pollination ( Double fertilization ( Seed developmentFlower Structure and FunctionFlowers are the reproductive shoots of angiosperm sporophyteAttached to stem by receptacleFour Floral organs are:CarpelsConsist of stigma, style, and ovaryFemale reproductive organsGroup of carpels is called a pistilStamensConsist of anther and filament Male reproductive organsPetals (sterile)Sepals (sterile)Development of Female Gametophytes (Embryo sacs)Embryo sac develops within an ovuleTwo integuments in an ovule surround a megasporangiumOne cell in the megasporangium undergoes meiosisDivides without cytokinesis, producing one large cell with eight haploid nucleiLarge cell partitioned into multicellular female gametophyte (embryo sac)Meiosis produces four haploid cells (in this case, megaspores)Only one megaspore survivesMembranes of cell are partitioned into 1 egg cell, 2 polar nuclei, 2 synergids, and 3 antipodal cellsDevelopment of Male Gametophytes (Pollen Grains)Microsporangia (also called pollen sacs) contain diploid microsporocytesThese cells divide by meiosis to form four haploid microsporesEach microspore then undergoes mitosis to produce a generative cell and tube cellPollen grain- two-celled male gametophyte and spore wallPollinationOccurs by wind dispersal (20%). A lot of pollen is produced by wind pollinated speciesAnimal pollination occurs in 80% of cases. Insects, birds, and mammals underwent coevolution with plants so anatomy between plant and pollinators correspond with eachother Transfer of male gametophyte to female stigma (anther ( stigma)Pollen grains produce a pollen tube that grows down into ovary once landed on the stigmaTwo sperm cells are discharged near the embryo sac. Double Fertilization occursOne sperm fertilizes eggOther combines with the two polar nuclei giving rise to a triploid endosperm, which is responsible for storing foodEach ovule develops into a seedOvary develops into fruit enclosing the seedSeed germinates, and the embryo develops into a new
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