Why does extra CO₂ raise yield?
Reveal answer
More photosynthesis → more glucose → more growth.
Key words: photosynthesis
6(a) FOOD PRODUCTION · RECALL
6.2 Carbon dioxide, temperature and crop yield
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Why does yield level off at high CO₂?
Reveal answer
Another limiting factor (light/temperature).
Key words: limiting
Why can high night temperature reduce yield?
Reveal answer
More respiration uses glucose, no photosynthesis.
Key words: respiration
Why measure CO₂ with sensors?
Reveal answer
Keep at optimum, avoid waste.
Key words: optimum
Why does yield fall at very high temperature?
Reveal answer
Enzymes denature + stomata close.
Key words: denature
What is meant by the term denature?
Reveal answer
A permanent change in enzyme shape so that it no longer works.
Key words: denature
CO₂ and temperature in glasshouses, Carbon dioxide. Why it can increase yield? Limit?
Reveal answer
Why it can increase yield: More raw material for photosynthesis. Limit: Rate plateaus when light or temperature limits.
Key words: Carbon dioxide
CO₂ and temperature in glasshouses, Temperature. Why it can increase yield? Limit?
Reveal answer
Why it can increase yield: Faster enzyme-controlled reactions. Limit: Enzymes denature above optimum; more water loss.
Key words: Temperature
CO₂ and temperature in glasshouses, Both together. Why it can increase yield? Limit?
Reveal answer
Why it can increase yield: Each removes a limiting factor. Limit: Light, water or cost may become limiting.
Key words: Both together
True or false, and why? “The hotter the glasshouse, the better the yield.”
Reveal answer
False. Above the optimum, enzymes denature and the rate of photosynthesis falls.
True or false, and why? “Adding CO₂ always increases yield.”
Reveal answer
False. Only while CO₂ is the limiting factor.
True or false, and why? “Enzymes are killed by heat.”
Reveal answer
False. Enzymes are not alive; they are denatured.
Why do some growers burn paraffin in glasshouses?
Reveal answer
It releases carbon dioxide and heat → faster photosynthesis.
Key words: carbon dioxide
Suggest why a grower stops adding carbon dioxide above a certain concentration.
Reveal answer
Another factor now limits photosynthesis → extra CO₂ costs money but gives no more yield.
Key words: limits
Below the optimum, how does raising temperature affect photosynthesis?
Reveal answer
Faster enzyme activity → faster photosynthesis.
Key words: enzyme