Define the following terms :
Osmotic pressure

Explanation

(a) Osmotic pressure (O.P) : It is the minimum pressure which needs to be applied to a solution to prevent the inward flow of its pure solvent across a semipermeable membrane. It is also defined as the measure of the tendency of a solution to take in pure solvent by osmosis.
(b) Action spectrum of photosynthesis : A graph showing the rate of photosynthesis, measured in terms of oxygen production at different wavelengths of light is known as action spectrum. It is obtained by plotting a graph between the rate of photosynthesis and different wavelengths of light.