Title: Factors affecting photosynthesis - What happens during photosynthesis? - OCR 21C - GCSE Combined Science Revision - OCR 21st Century - BBC Bitesize
Headings: Factors affecting photosynthesis
What happens during photosynthesis? - OCR 21C
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Factors affecting photosynthesis
Light intensity
Carbon dioxide concentration
Temperature
Chlorophyll
The compensation point

Content: Part of
Combined Science
Living together - Food and ecosystems
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Factors affecting photosynthesis
There are several ways of measuring the rate of photosynthesis in the laboratory. These include: the rate of oxygen output
the rate of carbon dioxide uptake
the rate of carbohydrate (glucose) production
These are not perfect methods as the plant will also be respiring, which will use up some oxygen and carbohydrate and increase carbon dioxide output. Several factors can affect the rate of photosynthesis: light intensity
carbon dioxide concentration
temperature
The amount of chlorophyll also affects the rate of photosynthesis: plants in lighting conditions unfavourable for photosynthesis synthesise more chlorophyll, to absorb the light required
the effects of some plant diseases affect the amount of chlorophyll, and therefore the ability of a plant to photosynthesise, such as downy mildew in grape vines
Light intensity
Without enough light, a plant cannot photosynthesise very quickly - even if there is plenty of water and carbon dioxide and a suitable temperature. Increasing the light intensity increases the rate of photosynthesis, until some other factor - a limiting factor - becomes in short supply. previous
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At very high light intensities, photosynthesis is slowed and then inhibited, but these light intensities do not occur in nature. Carbon dioxide concentration
Carbon dioxide – with water – is one of the reactants in photosynthesis. If the concentration of carbon dioxide is increased, the rate of photosynthesis will therefore increase.