Describe how various factors affect the rate of photosynthesis.

a) Environmental/ external factors.
-Carbon (IV) oxide concentration; carbon (IV) oxide is a raw material for photosynthesis; a decrease in carbon (IV) oxide concentration decreases the rate of photosynthesis; an increase in carbon (IV) oxide (beyond 0.04%) leads to an increase in the rate of photosynthesis; up to a given optimum; beyond optimum the rate of photosynthesis remains constant; due to other limiting factors;
-Light intensity/ quality of light; light provides energy required for photolysis/ photosynthesis; decrease in light intensity decreases the rate of photosynthesis; increase in light intensity increases the rate of photosynthesis; up to optimum level; beyond the optimum level the rate of photosynthesis remains constant; due to other limiting factors; at very high light intensity chlorophyll is damaged/ bleached; and the rate of photosynthesis drops;
-Temperature; decrease in temperature decreases the rate of photosynthesis; because enzymes are inactivated; as temperature increases the rate of photosynthesis increases; up to optimum; high temperatures above optimum denatures enzymes; thus reducing the rate of photosynthesis;
-Water; water is a raw material for photosynthesis; it influences opening and closure of stomata; which in turn affects the rate of diffusion of carbon (IV) oxide into the leaf;
b)Internal factors
-Chlorophyll concentration; chlorophyll traps light energy for photosynthesis; decrease in chlorophyll concentration decreases the rate of photosynthesis; an increase in chlorophyll concentration increases the rate of photosynthesis;
-Enzyme concentration; enzymes catalyze the photosynthetic reactions; increase in enzyme concentration increases the rate of photosynthesis; a decrease in enzyme concentration decreases the rate of photosynthesis;