9.4:
REPRODUCTION IN
PLANTS
Angiosperms
Can be divided into two groups, monocotyledonous
(monocots) and dicotyledonous (dicots) plants.
Monocots
Parallel venation in leaves
Dicots
Netlike venation
3 flower parts
Seeds with one seed leaf
(cotyledon)
Vascular bundles throughout
stem
Fibrous roots
Pollen grain with one opening
4 or 5 flower parts
Two cotyledon’s
Vascular bundles in a ring
Tap root
Pollen grain with three
openings
Reproductive phase
Flowers allow for sexual reproduction in plants.
This increase variety of flowers available.
Whether a shoot becomes a leaf or a flower is
determined by temperature as well as day length
(dark period).
What is photoperiodism?
A plants response to day/night
cycles
Plant type
Flowering
Dark period
e.g.
Long-day
Midsummer
Shorter dark
period
Short-day
Late spring
Longer dark
period
Radishes,
spinach,
lettuce
Poinsettias,
chrysanthem
ums, asters
Day-neutral
Anytime
Roses,
dandelions,
tomatoes
Phytochrome (blue-green pigment) controls
flowering in plants.
There are two forms,
inactive phytochrome (Pr)
or active phytochrome (Pfr)
660nm red light
Pr
Pfr
730nm far-red light
Pfr changes to Pr in
the dark, very slowly.
Growth
response
Reproduction in Angiosperms
Flower part
Sepals
Petals
Function
Protect developing flower while
it’s a bud
Colourful to attract pollinators
Anther
Part of the stamen, produces
male sex cells, pollen
Filament
Stalk of stamen, holding up
anther
Sticky top of the carpel, pollen
lands here
Stigma
Style
Ovary
Supports the stigma
Base of carpel, female sex cells
develop here
Plants can self-pollinate. Results in inbreeding – limited genetic variation
Plants can also cross-pollinate. Pollen
carried from one plant to another, creates
genetic variation but is risky! Why?
Pollination can be controlled by scientists,
but it’s very tricky.
Remember…
Pollen is male
Stigma is female
How many vectors of pollination can you think of?
-
Wind
Water
Insects
Birds
Animals
Male sex cell fuses with female
sex cell. Diploid
formed.
zygote
How does the genetic material
in the pollen reach the egg
cells in the ovules (inside the
ovary)?
POLLEN TUBES!
Once fertilized, the growing
zygote will grow and eventually
become a seed.
http://www.sumanasinc.com/web
content/animations/content/angi
osperm.swf
Seed part
Testa
Cotyledons
Function
Protective outer layer
Seed leaves, nutrient store
Microphyle
Scar left where pollen tube
entered
Embryo root and embryo
shoot
New plant after germination
For a seed to be dormant, how
much water should it contain?
10 – 15%
Are there advantages of
dormancy? If so what are they?
What conditions are needed for germination?
Water (rehydration)
Oxygen (respiration to produce ATP)
Temperature (enzymes)
Germination
1. Water absorbed by seed. Osmosis
2. Gibberellin (gibberellic acid) released  growth
hormone. Amylase released
3.Amylase causes hydrolysis of starch  maltose
4. Maltose hydrolysed  glucose (cellular
respiration or condensed  cellulose)
5.Cellulose forms cell walls
Maltose really important until leaves are produced,
then photosynthesis takes over.
26ft
Sunflower?!!