Learning focus
Use precise biological vocabulary, trace control pathways, explain cause-and-effect mechanisms, interpret diagrams and apply ideas to unfamiliar contexts.
Water
Water enters the seed by imbibition, swelling tissues and softening the testa. It provides a medium for reactions and activates enzymes that break down food reserves. Without water, metabolism remains very slow.
Oxygen and temperature
Oxygen is required for aerobic respiration, which transfers energy for cell division, growth and active transport. A suitable temperature allows enzyme-controlled reactions to proceed. Very low temperature slows reactions; excessive temperature may denature enzymes.
Mobilising food reserves
Enzymes break large, insoluble food reserves into small soluble molecules. These are transported to the embryo and used in respiration and synthesis. The radicle emerges first, followed by shoot growth. The seedling depends on reserves until leaves can photosynthesise.
Investigating conditions
Use groups of similar seeds and change one factor at a time. A suitable design may compare water present or absent, oxygen available or excluded, and warm versus cold conditions. The control should receive all required conditions.
Practical or data skill
Set up germination treatments that separately test water, oxygen and temperature. Use enough seeds, control other variables and record the percentage germinating.
Examination tip
Light is not listed as a universal requirement for germination; water, oxygen and suitable temperature are.
Review questions and suggested answers
Question 1
Why is oxygen needed during germination?
Suggested answer
For aerobic respiration to release energy.
Question 2
What is the role of enzymes?
Suggested answer
They break stored food into soluble molecules for respiration and growth.
Question 3
Which embryonic structure normally emerges first?
Suggested answer
The radicle.
