RATE OF PHOTOSYNTHESIS

Light Intensity

Increasing light intensity will increase the rate of photosynthesis, but only up to a certain point.

Eventually the rate plateaus (levels off) as other factors become limiting (e.g. CO₂ and water availability).

Note that altering the light intensity can also affect the temperature (see below).

Light Wavelength

There are actually many different types of chlorophyll, the most common / important of these (chlorophyll a and chlorophyll b) both absorb light most strongly in the red and blue regions of the spectrum. As a result, green light is reflected and the plants appear green.

Altering the wavelength can also affect the rate of photosynthesis. For instance, plant growth is poor under green lights as most of the light is reflected.

Co₂ Concentration

Increasing CO₂ will increase the rate of photosynthesis, but only up to a certain point.

Eventually the rate plateaus (levels off) as the chloroplasts become saturated with CO₂ or other factors become limiting (e.g. light intensity).

Enzyme Activity

Photosynthesis is a series of chemical reactions. Many of these reactions are catalysed by enzymes. Enzyme activity is affected by a range of factors including:

• pH
• temperature
• enzyme concentration
• substrate concentration - the availability of the reactants (Water & Carbon Dioxide)
• product concentration - the build up of products (Oxygen & Glucose) can limit photosynthesis
• enzyme inhibitors

^{For further detail see ENZYME ACTIVITY -FACTORS}