Factors affecting photosynthesis

Photosynthesis is influenced by both environmental and genetic factors.

The environmental factors include light, availability of CO2, temperature, soil, water and nutrient supply apart from age of leaf, leaf angle and leaf orientation.

Photosynthesis is not affected by all environmental factors at a given time.

According to Blackmann who postulated Law of Limiting factor in 1905, photosynthesis is limited by slowest step of the most limiting factor in the pathway.

This means that at a given time, only the factor that is most limiting among all will determine the rate of photosynthesis.

For example, if CO2 is available in plenty but light is limiting due to cloudy weather, the rate of photosynthesis under such situation is controlled by the light.

Further, if both CO2 and light are limiting, then the factor which is the most limiting of the two will control the rate of photosynthesis.

Both quality and intensity of light influence photosynthesis.

Light between the wavelength of 400nm to 700nm is most effective for photosynthesis and this light is called photosynthetically active radiation.

As the intensity of light increases the rate of photosynthesis increases.

However, if the light intensifies, the rate of photosynthesis decreases.

This is because of higher intensity of light destruction of chlorophyll occurs.

Factors affecting photosynthesis – photochemical and dark reaction

Photochemical reactions and dark reactions of photosynthesis respond differently to temperature.

Photochemical reactions in the thylakoid remain unharmed by temperature, whereas the enzymatic dark reactions get influenced adversely.

At higher temperature, the enzymes become inactive.

Low temperature also inactivates the enzymes.

The current level of CO2 is about 0.036 per cent or 360 ppm (parts per million), which is very low as compared to the concentration of other gases in the atmosphere such as O2 and N2.

The rate of photosynthesis in all plants increases with increase in the concentration of CO2 upto 500 ppm, when other factors are not limiting.

Availability of water in soil has a prominent effect on photosynthesis.

If the soil water becomes limiting factor, the rate of photosynthesis declines.

Among various nutrients, nitrogen has a direct relationship with photosynthesis.

Since, nitrogen is a basic constituent of chlorophyll and all enzymes involved in dark reactions, any reduction in nitrogen supply to plants has an adverse effect on photosynthesis.

In general all essential elements affect the rate of photosynthesis.

Among leaf factors, such as leaf age, leaf angle and leaf orientation, leaf age has the most prominent effect on photosynthesis.

If leaf undergoes, senescence, loss of chlorophyll occurs.

The photosynthetic enzymes also get inactivated resulting in reduced rate of photosynthesis.

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Other links

Plant tissue culture – origin and techniques

Plant physiology – photosynthesis and its significance

Site of photosynthesis and Mechanism of photosynthesis

Electron transport system and photophosphorylation types

Dark reaction