RHS Level 2 Certificate Year 1 Week 9 overviewPresentation Transcript
RHS Level 2 Certificate Week 9 – Germination and seed dormancy; Introduction to propagation by seed
Identify three methods of seed dispersal
Describe ideal conditions for storage of seed
Name the stages of germination
State the factors affecting germination of a seed and how dormancy may be broken.
Define the terms: ‘viability’ and ‘dormancy’.
Define: ‘epigeal’ and ‘hypogeal’ germination
Outline the steps to be taken when sowing seeds into a seed tray
Parts of the Seed - review
Seed – formed from the mature fertilized ovule and containing the embryo and stored food.
Parts of the seed – review vocabulary and structure. (Testa, plumule, cotyledons, micropyle, radicle)
Animal or bird
Enables the seed to germinate away from competition from the parent plant.
Slow rate of respiration within the dormant seed.
Viable seed is able to germinate if the right conditions are present.
Seed remains viable 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.
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) – the radicle emerges followed by the hypocotyl and the shoot begins to grow. The process of germination ends when the shoot reaches the surface and begins to photosynthesise.
Key factors for germination
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.