Biology · Ch 11 — Photosynthesis in Higher Plants
Light
Light
While discussing light as a factor that affects photosynthesis, we need to distinguish between light quality, light intensity and the duration of exposure to light.
- At low light intensities, there is a linear relationship between incident light and CO2 fixation rates — as light increases, the rate increases proportionally.
- At higher light intensities, the rate gradually does not show further increase, because other factors become limiting. …
Drawn by us to help you understand the concept clearly, and verified to make sure it's accurate. For exams, practice from your NCERT textbook's own diagram.
This graph plots the rate of photosynthesis on the vertical axis against light intensity on the horizontal axis. At low light intensities the curve rises steeply and almost linearly (region A), showing that light directly limits the rate here. As intensity increases the curve bends and then flattens into a plateau (points B to C), where the rate no longer increases because other factors such as CO2 or temperature have become limiting. This levelling shows light saturation, which occurs at only about 10 per cent of full sunlight. The dashed lines to points E and D mark the saturated rate and the intensity at which saturation begi …