3.5 Practical: Conditions for Germination

Edexcel IGCSE Biology

what is germination?

the start of growth in the seed

what are the three factors required for successful germination?

* water
* oxygen
* warmth

why is water needed for germination?

* allows the seeds to swell up
* allows seed coat to burst and allow growing embryo plant to exit the seed
* allows the enzymes in the embryo to start working so that growth can occur

why is oxygen needed for germination?

* required for respiration
* respiration allows energy to be released for germination and growth

why is warmth needed for respiration?

* germination improves as temperature rises (up to a certain point)
* reactions which take place are controlled by enzymes
* enzymes cannot function effectively when temperature is too low

apparatus needed for germination practical

* test tubes
* test tube holder
* cress seeds
* cotton wool
* fridge

method:

1. set up 4 test tubes each containing 10 cress seeds on cotton wool
2. label test tubes A, B, C, D


1. test tube A - cotton wool dry
2. test tube B - cotton wool is moist
3. test tube C - enough water to cover the cotton wool and seeds then add layer of oil on top
4. add enough water so that cotton wool is moist
3. leave A, B, C at room temperature/incubated at specific temperature (20 degrees celsius)
4. place D in fridge (4 degrees celsius)
5. leave all test tubes for 5 days
6. compare results and see which tube has greatest number of seeds

why are the test tubes set up like this?

* each of the factors required for germination can be tested by selectively removing each in turn
* test tube A - water removed
* test tube b - control tube (all factors present)
* test tube c - oxygen is removed
* test tube d - warmth removed

results