[Photosynthesis] 4.How does the light intensity affects the rate of photosynthesis ?

Light is the layman's term for visible radiant energy in the 400 to 700 nm wavelength region of the spectrum. In other words, it is the form of radiant energy (i.e. radiation) that animals can see. It is also the wavelengths of radiant energy that plants use in photosynthesis and for most other reactions that require light.

The rate of photosynthsis in a plant depends on the supply of carbon dioxide, supply of light, supply of water, temperature and various other factors like the amount of chlorophyll.In this blog,we will be setting the supply of light and its intensity as a more prominent factor affecting the rate of photosynthesis .

If the plant is in dim light, but has plenty of CO2, H2O and is warm enough, then it will be light which is limiting the rate of the whole process. If this is the case, then increasing the light will increase the rate of photosynthesis.

Measurement of light intensity
1) photometer or common light meter (cheapest) - measures amount of luminance
Expressed as: a) foot-candle (ft-c) - 1 lumen per square foot b) lux - 1 lumen per square meter
1 foot-candle = 10.76 lux

fig 1 : The relation between carbon dioxide exchange and
light intensity

Fig 1 shows the relation beween carbon dioxide exchange and light intensity.The rate of photosynthesis is show by the carbon dioxide exchange in the graph affected by the light intensity. As we can see , the higher the light intensity , the higher the rate of photosynthesis. However, the rate of photosynthesis will level off at the tip of the curve due to the limited amount of chlorophyll on the leave as well as the limited quantity of light that can be absorbed by the plant for photosynthesis.