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Germination and asexual reproduction in plants
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Seeds need the right conditions to germinate. Plants can also reproduce without seeds.
Conditions for germination
Seeds need water, oxygen and a suitable temperature to germinate.
Practical: set up tubes of seeds on cotton wool: one with water (control), one dry, one with boiled water covered with oil (no oxygen), and one with water in a fridge (cold). Only the control germinates well.
Practical: set up tubes of seeds on cotton wool: one with water (control), one dry, one with boiled water covered with oil (no oxygen), and one with water in a fridge (cold). Only the control germinates well.
Food reserves
A seed contains stored food (such as starch in the cotyledons).
The germinating seed uses these reserves for respiration and growth until its first leaves can photosynthesise.
Enzymes digest the starch into sugars that the embryo can use.
The germinating seed uses these reserves for respiration and growth until its first leaves can photosynthesise.
Enzymes digest the starch into sugars that the embryo can use.
Asexual reproduction
Natural: runners are side shoots that grow along the ground (as in strawberry plants). New plants form where they touch the soil.
Artificial: gardeners take cuttings: a short piece of stem with leaves is put in damp compost, and it grows roots.
The new plants are genetically identical to the parent (clones).
Artificial: gardeners take cuttings: a short piece of stem with leaves is put in damp compost, and it grows roots.
The new plants are genetically identical to the parent (clones).
Why is the boiled water in the 'no oxygen' tube covered with a layer of oil?
- Boiling removes dissolved oxygen from the water.
- The oil stops oxygen from the air dissolving back in.
Answer: To stop oxygen from the air dissolving back into the water.
Germination needs water, oxygen and a suitable temperature. Seeds use stored food until leaves can photosynthesise. Plants reproduce asexually by runners (natural) or cuttings (artificial), producing genetically identical offspring.
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