BIOL 420 1st Edition Lecture 14The Angiosperm Life CycleText Reference: Chapter 19, pages 465-474- Floral Structure (Review)Sepals (calyx)Petals (corolla)Stamens (anther + filament)Carpels (pistil) stigma+ style + ovary- Pollen FormationMicrosporogenesis: formation of microspores (single-celled precurosrs of pollen grains)Microgametogenesis: later development of the microgametophyte to the three-celled stage. When the microspore divides mitotically, forming 2 asymmetrical cells within the original microspore wall. The division forms a large vegetative cell and a small generative cell.Microsporocyte (microspore mother cell)MicrosporePollenTube (vegetative) cellGenerative cell- Pollen grains (examples) – most flowering plants can be identified from pollen grainsAesculus (Horse chestnut) – each grqain has 3 lobes saperated by deep furrows, when the pollen grain germinated the pollen tube will emerge from a pore in one of the furrowsGrass (Phleum pretense) – single porelike apertureThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Pumpkin (Cucurbita pepo) – spiny pollen grain that has multiple poresLavender (Lavandula dentate) – member of mint family, nests in petal cells - Egg and Polar Nuclei FormationMegasporogenesis: involves with the meiosis and results in the formation of megaspores within the ovule in the nucellusMegagametogenesis: is the development of the megaspore into the embryo sacMegasporocyte (megaspore mother cell): undergoes meiosis, giving rise to a linear series of 4 megasporesOvule: Funiculus: bearing a nucellus enclosed by one or 2 integuments; the stalk of an ovulePlacentaInteguments- Embryo sac - megagametophtyeMicropyle: In the ovules of seed plants, the opening in the integuments through which the pollentube usually enters.Chalaza: The region of an ovule or seed where the funiculus unites with the integuments and thenucellus. Opposite end of the micropylar and combines in the middle to form polar nuclei. Antipodals (3): Three (sometimes more) cells of the mature embryo sac, located at the end opposite the micropyle near more the chalaza end. The three left at the chalaza end forms antipodalsPolar nuclei (2): Two nuclei (usually), one derived from each end (pole) of the embryo sac, which become centrally located; they fuse with a male nucleus to form the primary (typically 3n)endosperm nucleus.Egg Apparatus: the remaining 3 nuclei at the micropylar end become organized as this consisting of an egg cell and two short lived synergidsSynergids (2): In flowering plants, two short-lived cells lying close to the egg in the mature embryo sac of the ovule. Amborella is an exception, with three synergids.- Pollination and double fertilizationDehiscence: split open; the opening of an anther, fruit, or other structure, which permits the escape of reproductive bodies contained within.Indehiscent: Remaining closed at maturity, as are many fruits (samaras, for example).Pollination: when the pollen grains are transferred to the stigmas  after hydration, the pollen grain germinates, forming a pollen tube  the generative cell divides forming two spermsFertilization- Double fertilization: leads to the formation of an embryo and endospermTube nucleusGenerative nucleus – sperm cellsTriple fusion: the fusion of one of the sperm nuclei with 2 polar nuclei results in a triploid (3n)Endosperm: primary endosperm nucleus divides to form thisZygote: developes into a embryo  the integuments develop a seed coat  the ovary wall and related structures develop into a fruitOvule – seedOvary – fruit- Life cycle of soybean illustrationFlowersNectaryOvaryOvules: a single megasporocyte developes and eventually divides meiotically giving rise to 4 megaspores, 3 disintegrate  the 4th develops into the female gametophyteAnther – with microsporocytes mother cells develop these divide giving rise to 4 haploid microsporesOvule – with megasporocytesMicrosporesMegasporesPollen grain: germinates on the stigma, producing a pollen tube which grows own the style into the ovary entering the ovule through the micropyle. One sperm nucleus from the pollen tube fuses with the peg, producing the zygote. The 2nd sperm nucleus fuses with the 2 polar nuclei of the embryo sac, producing endosperm nucleus.Tube (vegetative) cell Generative cellMicropyle- Embryo sacMicropyleChalazalAntipodals (3)Polar nuclei (2)EggSynergids (2)EndospermZygoteHypocotylCotyledonSeedSeed coatAnimals as Agents of Floral EvolutionText Reference: Chapter 20, pages 487-492- Plant reproduction – the challenges of the terrestrial habitatSelf-pollination (self-fertilization)Cross-pollination (cross-fertilization): By attracting insects and other animals with their flowers, and by directing the behavior of these animalsWind pollinationCoevolution of flowering plants and insects- Protection of ovule from insects and animalsNaked ovule to closed carpal: attraction of insects to this results in the loss of ovules to the insectsInferior ovary: changes in the shape for additional protection of the ovules from being eaten by insects and other animals, providing reproductive advantageEvolution of perfect (bisexual) flowers: the presence of both carpels and stamens in a single flower- If a given plant species is pollinated by one or just a few types of pollinators, specialization in floral structure occurred- Pollinators and their flowers Beetles & Flies: both depend on floral odors that are fruity or resemble dung or carrion and in beetle pollinated flowers, essential floral parts are often covered and thus protected from their gnawing visitorsBees: most important pollinators. Bee flowers have showy, brightly colored petals that are usually blue or yellow. Can see UV light but can not see red Butterflies and moths: often have ‘landing platforms’ built into the structure of the follower. Moths – attract more white or pale colors that have a sweet, penetrating scent. Both is often located at the base of a long, slender corolla tube or spur and is accessible only to the long, sucking mouthparts of these insectsBirds: pollinated flowers generally have a copious, thin nectar but usually have little odor because the smell is poorly developed in birds. They have a keen sense of color and the flowers they visit regularly are colorful, with red and yellow ones being most commonBats: obtain most of their food from