Pollination and Fertilization

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Pollination and Fertilization Powered By Docstoc
					Seed Plants cont.
 B. Angiosperms (seed container –
  seed formed in an ovary)
 Division Anthophyta (flowering plants)
 Class Monocotyledones (monocots);
  one seed leaf (stored food for
 Class Dicotyledones (dicots); two
  seed leaves.
  Monocots / Dicots
 Parallel leaf veins.       Branching leaf veins.
 One cotyledon.             Two cotyledons.
 Floral parts in            Floral parts in
  multiples of 3.             multiples of 4 or 5.
 Scattered vascular         Vascular bundles
  bundles.                    arranged in ring.
 Net-like fibrous roots.    Tap roots.
 No secondary               Secondary growth
  (woody) growth).            usually present.
  Flower Structure
 The flower is the sexual reproductive structure.
 Sepals – usually green covering over bud;
 Petals – may attract pollinators; corolla.
 Stamen – male structure; androecium.
 Carpel (pistil) – female structure; gynoecium.
 Flowers may be “perfect” with male and female
  parts, or “imperfect” with only one structure.
Stamen Parts / Pistil Parts
                       Stigma: sticky tip,
 Anther: pollen
                        collects pollen.
                       Style: stalk that
  structure.            supports/elevates the
 Filament: stalk       stigma.
  with                 Ovary: contains the
  supports/elevates     ovules (eggs).
  the anther.          Ovary develops into fruit;
                        Ovule develops into
  Sexual Reproduction in
  Flowering Plants
 Photoperiodicity: sensitivity to light and
  darkness cycles.
 Length of dark critical in inducing blooming;
  hormonal message from leaves.
 The mature plant is the sporophyte generation.
 In the ovule, the diploid megaspore mother cell
  undergoes meiosis, then mitosis to form 8
  haploid nuclei; called the female gametophyte.
 In anthers, diploid microspore mother cell
  divides by meiosis, then mitosis to form pollen
  grains each with two nuclei (male gametophyte)
  Pollination and
 Pollination – when pollen lands on the stigma.
 Pollen germinates as pollen tube grows down
  the style toward the ovary.
 Double fertilization -- one sperm nucleus
  fertilizes the egg (forms diploid zygote/new
  sporophyte); one sperm nucleus joins the 2
  endosperm nuclei (triploid, will form starch).
 Zygote/embryo and endosperm develop into a
  seed(s); ovary swells as fruit develops.

Monocot seed
 Radicle: embryonic root.
 Coleoptyle: embryonic stem.
 Plumule: first true leaves.
 Endosperm: starchy food for embryo
  (popcorn…mmm, endosperm).
Dicot seed

  Hypocotyl: embryonic stem/root;
   region below the cotyledon (seed
  Epicotyl: embryonic stem; region
   above the cotyledon.
  Plumule and a tough seed coat.
 3 Plant Tissues
 Embryonic protoderm  dermal tissue
  (epidermis and root hairs)
 Procambrium  vascular tissue (xylem,
  phloem, and cambium)
 Ground meristem  ground tissue
  (parenchyma, collenchyma,
Root Structure
 Epidermis
 Cortex/Pith: parenchyma.
 Endodermis: cells regulate movement of
  water in/out of vascular tissue.
 Pericycle: produces secondary roots.
 Vascular cylinder: xylem (tracheids and
  vessel elements) and phloem (sieve tubes
  and sieve cells).
Monocot Root
Dicot Root
Stem Structure
 Vascular bundles: xylem and phloem
  (and cambium in dicots).
 Sclerenchyma
 Cortex/Pith: collenchyma and
Monocot Stem
Dicot Stem
Regulation and Behavior
 Tropisms: plants parts grow toward or
  away from an external stimulus.
 Phototropism: “positive” in stems that
  grow toward the light.
 Gravitropism: “positive” in roots that
  grow down with gravity; “negative” in
 Thigmotropism: cells opposite from a
  touch will elongate; tendrils coil around
  Regulation and Behavior
 5 types of hormones:
 1. Auxins: indoleacetic acid (IAA) and similar
 Promotes cell division and elongation; produced
  by apical meristems.
 Inhibits axial meristem growth.
 Can produce fruits without fertilization.
 Most weed killers are synthetic auxins.
 Plant Hormones cont.
 2. Gibberellins: formed in young leaves and
 Cause cells to break down endosperm for
 3. Cytokinins: formed in roots.
 Cause branching growth in stems and roots;
  stimulates cell division.
 Synthetic gibberellins extend storage life of
  Plant Hormones cont.
 4. Ethylene: only hormone that is a gas.
 Initiates ripening of fruit; contributes to
  plant aging.
 5. Abscisic acid: regulates leaf loss
 Plant copes with dry seasons, pest
  attack, etc.

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