Plant Reproduction by yurtgc548


									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
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
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
-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
-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
      dry weather
-pollinated by animals
  -have bright flowers, distinctive
  odors, nectar (sugar solution)
  -pollinators include bats, bees,
  beetles, moths, butterflies,
  mosquitoes, monkeys, and
-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
  *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
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)
             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
  -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
     *epicotyl - between plumule and
     *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
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
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
  -vegetative reproduction (leaves,
  stems, roots) - table 30-2 p. 623
  Propagation by humans
  -roots form from a piece of stem, or
  shoots form on a piece of root
  (houseplants, ornamental trees and
  shrubs, some fruit crops)
  -roots form on stems where they make
  contact with the soil (raspberries)
 -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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