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Chapter 12

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  1. Chapter 12 Flowers and Fruits

  2. Flowers • Sexual reproductive organs of flowering plants • angiosperms, most diverse plant group • produce new generations thru sexual reproduction – embryo develops into a seed

  3. Parts of a Flower • Receptacle – flower parts attach here at the swollen area near the penduncle – stalk of the flower • Sepal – outer whorl of floral parts – all the sepals are called a calyx • All the petals together make up the corolla which form the next whorl • both are sterile parts of the plant and function to attract pollinators

  4. Sexual Reproduction Parts • Male part is the stamen • produce pollen grains that produce sperm • made up of the anther and filament • Female part is the pistil • inside 1 to many ovules – in each ovule is a single egg • made of the stigma and the style • Egg and sperm fuse in the ovule and develops into the seed • Ovary of flower and sometimes associated parts – becomes fruit that protects seed(s) and help in dispersal

  5. Stamens • Produce the pollen grains • 4 pollen-containing chambers fused into an anther that make pollen grains that are released thru a slit or thru the top • Anther generally supported on a stalk called the filament • Collection of stamens is a androecium • variation in number and arrangement of stamens, attachment of anther to filament, way release pollen from anther

  6. Stamen Arrangements Magnolias have dozens of stamens Some have free stamens and others are fused at filaments

  7. Pistils • Contain at least one ovule in their ovary and may be 1 or more per flower, some have one ovary with several carpels fused at the edge • ovary is called the carpel • Enlarged lower end is the ovary and the stigma is usually on a stalk and receives the pollen • stalked is called the style • raise the stigma to enhance pollination

  8. Female Reproductive Parts • Carpels/pistil have no gender • Specialized structure called the embryo sac in the ovule that is female • All the carpels collectively called the gynoecium • Indicators for how many carpels • chamber for each carpel is a section in an orange • stigmas or style may also reflect the number of carpels • lilies have 3 seed chambers and 3 stigma but only one style – made from 3 styles that fused together from 3 carpels • 4 lobes on the stigma with 4 fused carpels

  9. Petals • Often colorful, fragrant parts of flower • Collective petals are called the corolla – usually the most noticeable and attractive part - #, size, color and odor distinguish between flowers • Petals can be free, fused in short tube with large lobes, fused into long tube that encompasses most of the corolla – honeysuckle • aids in pollination

  10. Flower Symmetry Radially symmetrical – petals develop equally Bilaterally symmetrical – petals do not develop equally

  11. Floral Part Arrangements • a – spiral – magnolia • b – whorls – lily • c – petal like sepals and radial symmetry – daffodils • d – bilateral symmetry – pansy • e – petals fused into a tube – cape primrose

  12. Sepals • Flowers usually have a specific number of petal that they corresponds to the number of stamens, carpel and sepal • magnolia – hard to separate petals from sepals • Leaf-like sepals protect immature flower • may resemble petals like in the lily – call them tepals • 4 o’clocks have a calyx (sepals) that look like a corolla (petals) but they have no petals • Sepals may fuse into a tube and calyx may be radially or bilaterally symmetrical • Number of sepals also can reflect the number of other flower parts • same number of sepals and petals – look down from above they alternate • Protect inner parts of flower – prevent drying out • often fall off at maturity or after pollination and fertilization

  13. Embryo and Endosperm • Plants have a sexual reproduction part to their life cycle • Creates the embryo in a seed that matures into a plant – requires the formation an egg and sperm for fertilization • Most cells have diploid numbers of chromosomes • 1 set from each parent • Gametes are haploid – these are the reproductive cells • have only ½ the number of chromosomes – meiosis • fertilization produces a zygote that is diploid

  14. Life Cycle • Sperm is made in the pollen grain in the anther • Egg made in embryo sac in the ovule • Pollen grain and egg are gametophytes of flowering plants • Zygote grows in ovule becomes first cell of new organism

  15. Double Fertilization • Fertilization requires that pollen grains from anther to receptive stigma of a pistil • Embryo sac forms with a stalk and 1 or 2 integuments that develop into seed coat • Pollen reaches stigma and germinates to make pollen tube down style into the ovary • pollen that forms the pollen tube is the tube cell • 2nd cell in pollen grain is the generative cell as it divides and makes 2 sperm – move to a small opening in ovule called micropyle

  16. Double Fertilization (cont) • The 2 sperm move into embryo sac thru synergids which are cells next to the egg • send out chemicals so that pollen can find the egg • Sperm #1 – fertilizes the egg to form zygote • Sperm #2 fuses with the polar nuclei which are haploid near the mid region of the ovule to make a triploid cell = 3 sets of chromosomes • usually forms the endosperm in the seed – food for the embryo • Ovule matures into the seed • Many insects visit but only pollen form same species sticks tightly to stigma while rest falls off easily • Flowers can be used identify plants

  17. Reproductive Morphology • Helps to explain diversity • Flowering plants way out number any other group of plants • Diversity in shape, size and forms • from the reproductive success in a wide variety of habitats = based on the development of the flower • seed, fruit, pollination and the methods by which these things are distributed

  18. Variation in Basic Parts • Some flowers lack sepals, petals, stamens or pistils • Grasses have 3 stamens, 1 functional carpel (may have 2 non-functioning ones), no petals or sepals • Others have either stamens or carpels but not both

  19. Flower Types • Complete flower – has all major parts – sepal, petals, stamens and pitils • Incomplete flower – lacks one or more of the above parts • Perfect flower – has and androecium (collection of carpels) and a gymnoecium (collection of stamens) even if petals and sepals are missing

  20. Position of the Ovary • Superior ovary – base of the ovary above the sepals, petals and stamen – St John’s wort • Inferior ovary – the sepals, petals and pistil rest on top of the ovary – daffodil • Incomplete ovary – ovary surrounded by the receptacle and the petals and stamens branch from the receptacle above the ovary - rose

  21. Monocot and Dicot Flowers • Identified by the number of their floral parts • Monocots – flower parts occur in 3 or multiples of 3 • 3 petals, 3 sepals, 6 stamens, 1 pistil with 3 chambers • mostly herbaceous plants – non-woody • Dicots – flower parts in 4 or 5 or multiples of 4 or 5 • 80% of all angiosperms – herbaceous and woody