Light intensity

The rate of photosynthesis is directly proportional to light intensity. A typical plant responds to changes in light intensity. Very high light intensities may actually damage some plants, reducing their ability to photosynthesise.

The light compensation point(the light intensity at which the rate of photosynthesis is exactly balanced by the rate of respiration) varies for different plants. Two major groups have been identified: sun plants and shade plants. Sun plants include most temperate trees, such as oak. They photosynthesise best at high light intensities. Shade plants include those of the shrub layer, such as ferns. Their light compensation point is relatively low, but they cannot photosynthesise very efficiently at high light intensities. Consequently sun plants outcompete shade plants at high light intensities.