Limiting factors HT: Cell level systems: Biology: GCSE (9:1)

Photosynthetic rate

The rate at which plants take in carbon dioxide, water and the energy from sunlight to produce glucose

Chlorophyll

A green pigment in plants that absorbs light energy used to carry out photosynthesis

Role of enzymes

Photosynthesis is an enzyme-controlled reaction where the enzymes are needed to convert carbon dioxide into glucose

Temperature

Increases the rate of reaction up to an optimum rate, after which the denaturation of enzymes will occur

Sunlight

Is needed as an energy source for photosynthesis to occur

Carbon dioxide (CO2)

Enters the plant through the stomata during gas exchange and is the source of carbon needed to make glucose

Temperature effect

Photosynthesis rate increases to an optimum and then decreases due to denaturing enzymes

Light intensity effect

Photosynthesis rate increases and then plateaus due to another limiting factor such as temperature or carbon dioxide

Carbon dioxide concentration effect

Photosynthesis rate increases and then plateaus due to another limiting factor such as temperature or light intensity

Chlorophyll effect

Plants with diseases or variegated leaves may have less chlorophyll which reduces the rate of photosynthesis

Limiting factor

An environmental factor that prevents photosynthetic rate from increasing

Three main limiting factors

Temperature, light intensity and carbon dioxide concentration

Plateau

Where a graph levels off and no longer increases past a certain point

Inverse-square law

Light intensity is inversely proportional to the square of the distance from a light source

Inversely proportional relationship

As the distance of light from a plant increases, the light intensity decreases