Investigate the factors necessary for germination (LC 2026) (Leaving Cert Biology): Revision Notes

Investigate the factors necessary for germination

Background:

Three factors are necessary for germination:

1. Water: necessary to soften testa and activate the enzymes needed for germination.
2. Suitable temperature: required for enzymes to work at optimum activity.
3. Oxygen: required for aerobic respiration.

Materials needed:

• Petri dishes
• Crest seeds
• Cotton wool
• Fridge set to 4°C
• Cooled boiled water
• Oil
• Incubator set to 27°C
• Test tube

Method:

Four experimental set ups are required for this experiment. The control has all the factors necessary for germination. The other three must each be missing one of the factors necessary for germination.

4. Place dry cotton wool into first petri dish and add 5 crest seeds to dish. This experiment is missing water. (A)
5. Place wet cotton wool into second petri dish and place into fridge at 4°C This experiment is missing a suitable temperature. (B)
6. Place cotton wool into a test tube with 5 crest seeds and place cooled boiled water over them, followed by a layer of oil. This process eliminates oxygen. (C)
7. The remaining petri dish is filled with wet cotton on top of which 5 crest seeds are added. (D)
8. Dishes A and D are all left exposed to oxygen and placed in an incubator 27°C for 72 hours. C is also placed in the incubator.
9. Record results obtained. A fair test in this experiment is ensured by using the same number of cress seeds in each petri dish.

	A	B	C	D (control)
Cotton wool	Dry	Wet	Wet	Wet
Temperature	Incubator at 27°C	Fridge at 4°C	Incubator at 27°C	Incubator at 27°C
Oxygen	Present	Present	Absent	Present
Missing Factor	Water	Suitable temperature	Oxygen	None

Results:

	A	B	C	D (control)
Result	No growth	No growth	No growth	Growth
Reason	No water to softening the testa or to activate enzymes.	No suitable temperature for enzymes to act.	No oxygen for respiration to occur.	Has all the factors necessary for germination.