CBSE Class 10 Answered

i) Light - Photosynthesis is affected by intensity, quality and duration of light. Rate of photosynthesis increases with the increase in light intensity until it reaches the point of saturation where photosynthesis becomes stationary. Maximum photosynthesis occurs only in visible part of spectrum of light. Maximum photosynthesis occurs in red light and in blue light. Generally 10-12 hours duration of light per day favours good photosynthesis.

ii) Temperature - In presence of plenty of light and CO₂ , photosynthesis increases with an increase in temperature. The optimum temperature at which it is maximum is 25-30° C, though in plants like Opuntia it takes place as high as 55° C. High temperatures will inhibit the process of photosynthesis.

iii) Carbon dioxide - Basically the more CO₂ in the air, the better the rate of photosynthesis. CO₂ is taken in during the daytime, and if its content was less that normal, photosynthesis couldn't happen normally. An increase in CO₂ concentration to about 1% in atmosphere is advantageous, but above this it has an inhibitory effect on photosynthesis.

iv)  Water - It is an essential raw material of photosynthesis. It provides hydrogen and plays a significant role in opening and closing of stomata. A decrease in water content decreases photosynthesis due to closing of stomata and dehydration of protoplasm.