1. Reproduction in Plants
Carissa Fletcher

2. Draw and label a diagram showing
the structure of a dicotyledonous
animal-pollinated flower.

3. Distinguish between pollination,
fertilization and seed dispersal.
Pollination is the transfer pollen from the anther to the stigmas.

4. • Fertilisation after the stigma is pollinated, the pollen grain germinates in a
response to a sugary fluid secreted by the mature stigma (mainly sucrose).
• From each pollen grain, a pollen tube grows out that attempts to travel to
the ovary by creating a path through the female tissue.
• The vegetative (or tube) and generative nuclei of the pollen grain pass into
its respective pollen tube.
http://www.biologyjunction.com/images/doublefertilazation.jpg

5. Seed dispersal the movement of seeds away from the parent plant.
http://www.field-studies-council.org/breathingplaces/food_for_us.htm

6. Draw and label a diagram showing
the external and internal structure of
a Corn - dicotyledonous seed.
1. Fertilisation takes place
2. The zygote divides rapidly by
mitosis and develops into an
embryo,
3. Differentiation into a young
shoot (plumule), a young
root, (radical) and seed
leaves (cotyledons).
4. The primary endosperm
nucleus also divides
mitotically to give a mass of
cells.

7. Explain the conditions needed for the
germination of a typical seed.
- The water content of seeds at between 5%-10% is
very low and is the major factor in preventing them
from germinating.
- As a rule the addition of water in the presence of
Oxygen and a favourable temperature (5-40OC) is
enough to break the dormancy.
- Light intensity is necessary for the germination of
certain seeds.
- A sustained period of cold is needed to make some
seeds in temperate climates germinate.
- Some will not germinate unless there has been the
intense heat of a flash fire.
- A physical abrasion or partial digestion in the
intestines of an animal may also be needed before
a seed will germinate.

8. Stages in germination
1. Seed takes up water rapidly – rupturing the testa
2. Water activates enzymes in the seed which hydrolyse insoluble storage
material into soluble substances.
3. Proteins to amino acids, starches into sugars and lipids into fatty acids
and glycerol.
4. Products are transported to the growing points of the embryos for
respiration and the growth of cell walls.
5. The amino acids are used in the formation of new enzymes and proteins.
http://www.youtube.com/watch?v=TJQyL-7KRmw

9. Economically important seeds
Peanuts
Soya beans
Caster oil seeds
Walnuts
Coconuts
Sunflower seeds

10. Explain how flowering is controlled
in long-day and short-day plants,
including the role of phytochrome.
Many plant processes are
influenced by light. Just
like the photoreceptors
used in photosynthesis.
A pigment called
PHYTOCHROME can
induce a plant light
-response.

11. Phytochrome
Phytochrome 660 absorbs red
light at 660nm
Phytochrome 730 absorbs light
in the far red region of the
spectrum.
http://plantphys.info/plant_physiology/phytochrome.shtml

12. Photoperiodism
One major influence on the timing of flowering is the length of the day or
photoperiod. The effects of the photoperiod on flowering differ from
species to species.
The main categories are;
1. Long-day plants – these only
flower when the period of
daylight exceeds a critical
length. (or a short period of
darkness) E.g. radish
2. Short-day plants – These only
flower when the period of
daylight is shorter than a
critical maximum length. (or a
long period of darkness) E.g.
Poinsetia

13. The role of phytochrome in flowering
Long day plants known to flower after short exposure to red light, the red light is
absorbed by phytochrome 660nm which converts to P730nm and induces
flowering.
Short day plants absorb light at P730 which is converted to P660nm. This is a
much slower process, and needs a long dark period.
Figure 4. Photoperiod and Flowering - Left side: Short day plants flower with
uninterrupted long nights. Right side: Long-day plants flower with short nights or
interrupted long nights
http://www.cmg.colostate.edu/gardennotes/142.html

14. Light regulated plant development