Plant Reproduction by yurtgc548

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									Plant Reproduction
Alternation of Generations
Mosses - gametophyte is the
 dominant form of the plant

Ferns, gymnosperms and
 angiosperms - sporophyte is the
 dominant form of the plant
   Sexual reproduction in
       angiosperms
Flower parts
  sepals - outer whorl or ring
           protect the other parts of the
                developing flower
  petals - next whorl
           animal pollinated plants have
           brightly colored petals
           wind pollinated plants usually
           have small or absent
           sepals/petals
Stamens - next whorl; male
 reproductive structures
    consist of:
    -anther (produce microspores
    that develop into pollen grains)
    -filament (supports the anther)
Carpels - innermost whorl; female
 reproductive structures
    pistil (one or more fused carpels)
    -ovary - enlarged base of pistil
    -style - stalklike
    -stigma -top, sticky or with hairs to
               trap pollen grains
   Gametophytes develop
   within the reproductive
           structures sacs) form
-female gametophyte (embryo
 within the ovary of the pistil
Megasporangium surrounded by two
 integuments, each with a micropyle
 -contains a megaspore mother cell,
 which undergoes mitosis to produce
 four haploid megaspores
 -one megaspore undergoes three
 mitotic divisions, which produces a cell
 with eight haploid nuclei
-one nuclei from each end (pole)
migrate to center and become polar
nuclei
-one cell nearest to micropyle enlarges
and become the egg
-two cells on either side of egg help
attract pollen tube toward the egg
-the integuments and embryo sac are
now a mature ovule, which may
develop into a seed
-male gametophyte (pollen grains) form
  within the anthers of the stamens
An anther contains four microsporangia
  (pollen sacs)
  -microspore mother cells each produce
  four haploid microspores
  -each microspore undergoes mitosis to
  produce two haploid cells that do not
  separate (pollen grain)
  -the larger of the two cells is the tube
  cell (forms pollen tube)
  - the smaller of the two cells is the
  generative cell, which will divide by
  mitosis to form two sperm
             Pollination
-occurs when pollen grains are
  transferred from an anther to a stigma
  -self-pollination - involves one flower,
  flowers on the same plant, or flowers
  from two genetically identical plants
  -cross-pollination - involves two
  genetically different plants
-self-pollinated due to structure of flower
-pollen dispersed by water
-pollen dispersed by air (wind)
  *depends on:
      release of large amounts of pollen
      ample air circulation
      proximity of plants to which pollen is
            transferred
      dry weather
-pollinated by animals
  -have bright flowers, distinctive
  odors, nectar (sugar solution)
  -pollinators include bats, bees,
  beetles, moths, butterflies,
  mosquitoes, monkeys, and
  hummingbirds
           Fertilization
-union of haploid gametes resulting in
  diploid zygote
-a pollen grain must land on a stigma,
  absorb moisture, and germinate (form a
  pollen tube)
-pollen tube grow through stigma and
  style toward the ovary
-enter ovule in ovary through micropyle
-two sperm travel through pollen tube
  and reach the egg
-double fertilization is unique to
  angiosperms
  *one sperm fuses with the egg to form
  diploid zygote
  *one sperm fuses with two polar nuclei,
  and then eventually develops into
  endosperm (provides nourishment for
  the embryo)
   Dispersal of fruits and
           seeds
Fruits and seeds are dispersed by:
  -animals (carried or eaten)
  -wind (tiny or with “parachutes”)
  -water (contain air chamber)
  -forcible discharge (pod dries and
          breaks open)
  -gravity
             Fruit types
A fruit is a mature ovary.
Fruits protect seeds, aid in their dispersal,
  and delay sprouting of seeds.
Classified based on:
  -how many pistils or flowers form the
  fruit
  -whether the fruit is dry or fleshy

p. 619 Table 30-1
      Structure of seeds
A seed is a plant embryo surrounded by a
  protective coat called the seed coat.
Seed structure differs between monocots,
  dicots, and gymnosperms.
  -dicot - two cotyledons which store
  nutrients (no endosperm)
     *plumule - shoot tip with embryonic
           leaves
     *epicotyl - between plumule and
           cotyledons
     *hypocotyl - cotyledons to radicle
     *radicle - embryonic root
-monocot - one cotyledon and endosperm
      *absorbs nutrients from endosperm
-gymnosperm - sporophyte embryo with
  needle-like cotyledons, surrounded by
  the tissue of the female gametophyte
  which functions as a source of nutrients
  for the embryo
     Seed germination
A seed will not germinate (sprout)
 until it is exposed to certain
 environmental conditions.
Many seeds experience dormancy (a
 state of reduced metabolism;
 growth and development do not
 occur).
Conditions needed for germination:
 -water - softens seed coat, activates
 enzymes that convert starch in
 cotyledons into simple sugars
 -oxygen - needed for cellular respiration
 -light - some seeds need light
 -temperature - within a certain range
 -extreme conditions - pass through
 digestive system of animal
       Corn (monocot)
1. Appearance of radicle
2. Shoot begins to grow
  -cotyledon remains underground
          Bean (dicot)
1. Appearance of radicle
2. Hypocotyl curves and becomes
   hook-shaped
3. Hypocotyl straightens after it
   breaks through the soil
4. Embryonic leaves unfold
   (cotyledons shrink and fall off)
   Asexual Reproduction
Production of individual without
  union of gametes
  -clones
  -vegetative reproduction (leaves,
  stems, roots) - table 30-2 p. 623
  Propagation by humans
Cuttings
  -roots form from a piece of stem, or
  shoots form on a piece of root
  (houseplants, ornamental trees and
  shrubs, some fruit crops)
Layering
  -roots form on stems where they make
  contact with the soil (raspberries)
Grafting
 -joining of two or more plant parts to
 form a single plant
 -bud or small stem of one plant is
 attached to the roots or stem of a
 second plant (vascular cambiums must
 be aligned)
 -commercial fruit and nut trees, many
 ornamental trees and shrubs
Tissue culture
  -production of new plants from
  pieces of tissue placed on a sterile
  nutrient medium
  -commercial production of orchids,
  houseplants, cut flowers, fruit
  plants, and ornamental trees,
  shrubs, and nonwoody plants

								
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