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Flowers, Seeds, and Technology. Plant structure and function. Flower Types. Complete flowers have all organs. Incomplete flowers don’t Depends on what pollinators they are trying to attract. Pollen. In anthers:
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Flowers, Seeds, and Technology Plant structure and function
Flower Types • Complete flowers have all organs. • Incomplete flowers don’t • Depends on what pollinators they are trying to attract.
Pollen • In anthers: • Microsporocytes undergo meiosis to make 4 microspores. Each becomes a pollen grain. • Pollen grain- gametophyte with a spore wall, generative cell (divides into 2 sperm), and tube cell (grows into pollen tube).
Embryo Sacs • In ovules : • Megasporocytes undergo meiosis to form 4 megaspores. One survives • Embryo sac – gametophyte with an integument, egg cell, and two polar nuclei in a central cell
Pollination • Transfer of pollen to the stigma • Pollen germinates and extends a pollen tube • Pollen tube sends two sperm to the embryo sac (double fertilization) • One sperm fertilizes the egg forming a zygote • One sperm fertilizes the polar cell and in becomes triploid nutritive tissue called endosperm.
Pollination Strategies • Colors of flowers- bright, white (night moths), UV • Scents- sweet (bees), stinky (flies) • Nectar- bats, birds, bees • Mimicry- fake mates (wasps)
Oops...Preventing Self Pollination • Dioecious plants have either male or female flowers • Staminate flowers only contain stamen • Carpellate flowers only contain carpels • Some plants plants stagger their organs • Thrums- flowers with long stamens and short styles • Pin- have short stamens and long styles • Self incompatibility -most plants reject its own pollen
Fruit Development • Ovaries become fruit to protect and disperse seeds • Ovary wall becomes the thickened wall of the fruit called the pericarp. Other organs fall off (depends on fruit)
Fruit Types • Simple- from one carpel or carpels fused into one (pea pod) • Aggregate – from multiple carpels on one flower (strawberry, blackberry) • Multiple- carpels from many flowers come together (pineapple, figs) • Accessory- made from tissues besides the ovary usually the fleshy tissue in the ovary called the receptacle. (apple) • Usually ripen when seeds are fully developed
Seed Development • Seed coat- covering from integument • Cotyledon- seed leafs, used for nutrient • Epicotyl- just below the cotyledons, holds mini leafs and apical meristem • Hypocotyl- just below the epicotyl attached to the radicle • Radicle – embryonic root.
Dispersing Seeds Seed Dispersal • Eaten by animals & passed thru digestive tract • Carried by wind • Float in water • Some have hooks to catch fur or feathers
Germination • Imbibition- uptake of water by seed • Radicle breaks through first • The hypocotyle then straightens out raising the cotyledons and epicotyl • The epicotyl spreads the mini leaves
Asexual Reproduction • Plants can grow through fragmentation a callus (group of undifferentiated dividing cells) will grow where a plant is clipped. • Apomixis- asexual seed production
Grafting • Two related plants can be combined or grafted. Usually a shoot is placed on a root. The root is the stock and the shoot is the scion. Ex. Wine grapes American stock French shoots.
GMO’s • Transgenic- plants having genes inserted to promote new phenotypes. Ex. bacterium DNA that makes a chemical toxic to insects but theoretically harmless to people, or inserting Daffodil genes into rice to increase beta carotene.
Bio Fuels • Plant biomass could by broken down into sugar polymers and fermented to create alcohol to use as bio fuel. (switch grass species, poplar, corn)
