The process of photosynthesis influenced by a no. of external and internal factors.
a) Light : It is most important factor for photosynthesis. Light affects the rate of photosynthesis in three different ways:-
I) Light intensity: The rate of photosynthesis increases with the increase of light intensity but very high and very low intensity decrease the rate of photosynthesis.
ii) Light quality: The rate of photosynthesis is different in different wavelength of light. It is more in red light which is followed by blue light while in green light, min. photosynthesis takes place. It is more in white light then monochromatic light.
Iii) Duration of light : Increase in duration of light increase the rate of photosynthesis but more than 12 hr. of light duration may decrease the rate of photosynthesis.
b) CO2 : Carbondioxide is all source of carbon for various organic products formed in plant like glucose, starch, etc. If CO2 concentration rise from 0.3% to 1 %, the rate of photosynthesis become high but higher concentration of CO2 decrease the rate of photosynthesis.
c) Water : Water is the essential raw material for photosynthesis because water and CO2 undergo chemical reaction in the formation of carbohydrate. Therefore, deficiency of water decrease the rate of photosynthesis. It also check the rate of entry of CO.
d) Temperature: The optimum temperature for photosynthesis is 20-30 0 Below this temperature, rate of photosynthesis decrease. In high temperature, denaturation of enzyme takes place which is essential for dark reaction.
e) Chlorophyll contents : The rate of photosynthesis directly relate with the amount of chlorophyll because it is the main pigment for absorption of light. Chlorophyll lacking plant i.e. fungi, bacteria are unable to show photosynthesis.
f) Anatomy of leaves : Anatomy of leaf like structure, position, distribution of stomata, cuticle, intercellualr space directly affects the rate of photosynthesis.
g) Leaf age: rate of photosynthesis increase in young or mature leaf but decrease in ageing leaf.
h) Accumulation of photosynthetic products : Accumulation of photosynthetic products decrease the rate of photosynthesis.