Angiosperm Reproduction and Biotechnology
Angiosperm Reproduction and Biotechnology
Angiosperms may reproduce
sexually or asexually.
Angiosperm Reproduction and Biotechnology
Plants show alternation
of generations.
n
mitosis
gametophyte
spores
gametes
2n
sporophyte
meiosis
Angiosperm Reproduction and Biotechnology
In angiosperms, the sporophyte
is dominant.
n
gametophyte
2n
sporophyte
Angiosperm Reproduction and Biotechnology
Angiosperm Reproduction and Biotechnology
Pollen (male gametophytes)
1. In the anther there are diploid
microsporocytes (also called
microspore mother cells)
2. These divide by meiosis to make
four haploid microspores.
Angiosperm Reproduction and Biotechnology
3. Each microspore becomes a
pollen grain, and each pollen
grain can make two sperm
4. The pollen grain doesn’t mature
and make sperm until it has
landed on the stigma of a carpel
and the pollen tube begins to
grow.
Angiosperm Reproduction and Biotechnology
Embryo sac (female gametophyte)
1. In the ovule there is a diploid
megasporocyte (megaspore
mother cell)
2. It divides by meiosis to make
four haploid megaspores, but
only one survives.
Angiosperm Reproduction and Biotechnology
3. Mitosis of the megaspore forms
the embryo sac
4. Ovule now consists of embryo
sac and integuments.
Angiosperm Reproduction and Biotechnology
Preventing self-fertilization
•carpellate vs. staminate
•pin vs. thrum
•floral organs mature at
different times
•self-incompatibility.
Angiosperm Reproduction and Biotechnology
Double fertilization
•One sperm fertilizes the egg
•The other sperm combines
with polar nuclei to make
endosperm.
Angiosperm Reproduction and Biotechnology
After fertilization
•Ovule becomes seed
•Ovary becomes fruit
•Endosperm stores nutrients
•Later, the cotyledons store
even more food.
Angiosperm Reproduction and Biotechnology
Asexual reproduction
•In stable environments:
–Stable characteristics
–Can make many copies
–Not frail
•In unstable environments:
–No variation, no evolution
–No disbursal of seeds.
Angiosperm Reproduction and Biotechnology
Asexual reproduction
•Fragmentation (cuttings)
•Apomixis (making seeds
asexually).
Angiosperm Reproduction and Biotechnology
Totipotent cells lead to:
•Cloning
•Transgenic plants
•Protoplast fusion hybrids.
Angiosperm Reproduction and Biotechnology
Uses of biotechnology:
•Insect resistance
•Herbicide resistance
•Nutritional improvement.
Angiosperm Reproduction and Biotechnology
Possible side effects:
•Allergens
•Non-target organisms
•Transgenic escape.