Sunlight intensity is just the degree of sunlight a plant receive. Normally, the intensity should be optimum. Let's look at what happens if the intensity is low or high.
Plants are phototrophic which means they utilize sunlight to photosynthesize. When there is little sunlight, the rate of photosynthesis is low leading to poor plant growth. It also have effect on the plant yield returning less profit for the farmer.
High sunlight intensity is not good too, as it means an increase in water loss from the plants. There will be increased transpiration which will lead to a scorched leaf because the level of water evaporation from the leaves have increased.
Certain enzymes are deactivated too. Enzymes are normally denatured by heat which leads to certain enzymes found in the plant to be denatured leading to a decrease in photosynthesis