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Plant Reproduction

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					Angiosperm Reproduction
What you need to know:
 The process of double fertilization, a
  unique feature of angiosperms.
 The relationship between seed and fruit.
 The structure and function of all parts of
  the flower.
Angiosperms have 3 unique Features:

1.   Flowers
2.   Fruits
3.   double Fertilization
Alternation of Generations
1.   Sporophyte (mature plant) produces
     spores
2.   Spores develop into male (♂)
     gametophyte (pollen) and female (♀)
     gametophyte (embryo sac)
    Flower Structure
 Reproductive shoots of angiosperm sporophyte
 Flower organs:
  1. Sepal – leaflike, protect flower bud
  2. Petal – modified leaves, attract pollinators
  3. Stamen – ♂ reproductive organ
        anther + filament
    4. Carpel – ♀ reproductive organ
        stigma + style + ovary
 Flower attached to stem at receptacle
 Pollination by wind, insects, birds
    Floral Variations
   Complete: has petals, sepals, stamen, carpels
   Incomplete: lacks 1+ of the above
   Perfect: has both stamen + carpel
   Imperfect: has stamen or carpel, not both (grass -
    no petals)
   Monoecious: plant species w/ both staminate and
    carpellate flowers on the same individual (corn)
   Dioecious: plant species w/ staminate flowers and
    carpellate flowers on different individual plants
    (date palm, arrowhead)
  Male Gametophyte                   Female Gametophyte
= Pollen Sac                        = Embryo Sac

Produced in anther                  Produced in ovule (in ovary)
Has 2 haploid nuclei:               Has 3 important haploid nuclei:
1. Tube nucleus (forms pollen       1. Egg (fuses with sperm)
   tube)                            2. 2 polar nuclei (fuses with 2nd
2. Generative nucleus (divides to      sperm to make 3n endosperm)
   form 2 sperm cells)
 Pollination: transfer pollen from anther to
  stigma
 Pollen tube grows down into ovary
    Double Fertilization
  Union of 2 sperm cells with different cells of
   embryo sac
1. One sperm + egg  zygote (2n)
2. One sperm + 2 polar bodies  endosperm
   (triploid 3n)
    ◦   Endosperm = nutrition for embryo plant
3. Ovule   develops into seed; ovary develops
    into fruit
    ◦   Seed = embryo + endosperm
The development of a plant embryo
Fruit
 Protects enclosed seed(s)
 Aids in dispersal by water, wind, or
  animals

       Simple          Aggregate         Multiple

    Single ovary of   Many ovaries of Many ovaries of
      one flower       one flower      many flowers

       Cherry           Raspberry        Pineapple
Developmental origins of fruit
 Seeds
Adaptations:
1. Dormancy = “resting”
      Low metabolic rate, not growing or developing
      Increases chances of germination in most
       advantageous time & place
2. Dispersal: varietyof methods
3. Protection: well protected by fruit
Germination
   Imbibition: uptake of H2O
    ◦ Seed expands and seed coat ruptures
    ◦ Trigger metabolic changes to begin growth
    ◦ Enzymes digest storage materials of
      endosperm (cotyledons)
    ◦ Nutrients transferred to growth regions of
      embryo
Germination
1.       Radicle  Root
2.       Shoot tip emerges above ground
             Stimulated by light
3.       Foliage leaves expand & turn green 
         photosynthesis

        Very hazardous for plants due to
         vulnerability
     ◦       Predators, parasites, wind
               Plant Reproduction
         Sexual                           Asexual
                    Both ways to reproduce

                                   Runners, bulb, root, graft,
      Flower  seeds
                                vegetative (grass), fragmentation

      Genetic diversity                      Clone
More complex & hazardous for
                                    Simpler & safer for plant
           plant
                               • Monoculture - cultivate w/ 1
                                 plant
                               • Reduces competition
                               • Benefits farmers

				
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posted:10/23/2012
language:English
pages:23