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