Question

why is the rate of photosynthesis more during a bright sunny day as compared to a cloudy day?

Answer 1

Rate of photosynthesis increases to a certain limit during a bright sunny day due to high intensity of sunlight and increased transpiration rate and CO₂ intake. On the other hand, rate of photosynthesis will be less on cloudy day, because of reduced intensity of light and less transpiration (Transpiration increases absorption of water needed for photosynthesis).