2. Quiz Weeks 7 and 8 Answers
1.
2.
3.
4.
5.
6.
7.
8.
9.
Meiosis
One set of chromosomes
Dominant
None – all the offspring would carry the dominant gene.
(b)
Carbon dioxide + water + light → glucose + oxygen
(when in the presence of chlorophyll )
Process: Photosynthesis
Respiration
Phloem
(a), (b) and (d)
3. Learning outcomes
1.1 State the environmental requirements for seeds to germinate
successfully: light levels; moisture; temperature; oxygen
1.2 Describe the changes that take place in a germinating seed,
including taking in water; rising respiration rate; rapid cell
division; and the splitting of the seed coat
1.3 State the meaning of the term ‘seed dormancy
1.4 Describe methods of overcoming seed dormancy, including
soaking; hot water treatment; nicking (chipping); abrasion; and
warm and cold treatments; stating an appropriate plant
example for EACH.
1.5 Describe the behaviour of French bean (Phaseolus vulgaris),
and broad bean (Vicia faba) as examples of epigeal and
hypogeal germination
1.6 Define the term ‘viability’ in relation to seeds
1.7 State the effect that storage has on the viability and
germination potential of seed
4.
5. Seed Storage
Slow
rate of respiration within the dormant
seed.
Viable seed is able to germinate if the right
conditions are present.
Seed remains viable (alive) for variable
periods of time depending on storage
conditions and genus/species.
Successful storage means controlling the
limiting factors of respiration to keep the rate
within the seed slow.
6. Germination
Stage one (Imbibition phase) – water enters the
seed (imbibition). The seed swells and the testa
splits
Stage 2 (Lag phase)– respiration begins to speed
up, the food in the cotyledons/endosperm is broken
down. Called the ‘lag phase’ because nothing
obvious is happening.
Stage 3 (Emergence phase) – rapid cell division
begins, the radicle emerges followed by the plumule
and the shoot begins to grow. The process of
germination ends when the shoot reaches the
surface and begins to photosynthesise.
8. Hypogeal Germination
•
Cotyledons remain in the soil, plumule emerges
first. Cotyledons do not photosynthesise. E.g.
Vicia faba (Broad bean) or Pisum sativum
(Pea).
9. Key factors for germination
Water
– needed to begin the process and
then for growth
Light – presence or absence depends on
species
Temperature – too cold and the seed may
run out of energy before the shoot emerges
Oxygen – needed for respiration
Food – stored in cotyledons or endosperm
Time – depends on the species.
10. Seed dormancy
Dormant
– a seed which is viable but unable
to germinate, either because the external
conditions are not correct or because of
factors within the seed itself
Examples- ‘after ripening’, chemical
inhibition, temperature, light (presence or
absence), thick seed coat or chemical
triggers for germination.
11. Breaking dormancy
Scarification
– damaging the seed coat by
nicking with a knife or rubbing with
sandpaper.
Soaking – cold or hot water (depends on
species) to soften seed coat and remove
chemical inhibitors
Stratification – controlled exposure to
required temperatures for the species (warm
or cold). Breaks down inhibitors and/or
matures the embryo.
12. Learning outcomes
1.1 State the environmental requirements for seeds to germinate
successfully: light levels; moisture; temperature; oxygen
1.2 Describe the changes that take place in a germinating seed,
including taking in water; rising respiration rate; rapid cell
division; and the splitting of the seed coat
1.3 State the meaning of the term ‘seed dormancy
1.4 Describe methods of overcoming seed dormancy, including
soaking; hot water treatment; nicking (chipping); abrasion; and
warm and cold treatments; stating an appropriate plant
example for EACH.
1.5 Describe the behaviour of French bean (Phaseolus vulgaris),
and broad bean (Vicia faba) as examples of epigeal and
hypogeal germination
1.6 Define the term ‘viability’ in relation to seeds
1.7 State the effect that storage has on the viability and
germination potential of seed
