Question

Explain the factors affecting the rate of photosynthesis.

Answer 1

Photosynthesis is a process done by which plants prepare their own food. This process takes place in the leaf of the plant in the presence of water, chlorophyll, sunlight, and carbon dioxide. In particular, photosynthesis occurs in the chloroplast of the plant. The chloroplast absorbs sunlight and converts it into food through a series of reactions. The rate and efficiency of photosynthesis is affected by several factors.

Complete explanation:
Some of the factors affecting photosynthesis include light, concentration of carbon dioxide, water, temperature, concentration of oxygen, chlorophyll content and anatomy of the leaf.
Light is one of the major factors affecting photosynthesis. Photosynthesis cannot take place in the dark and the source of light for the plants is sunlight. Three attributes of light important for photosynthesis are intensity, quality and duration. Excessive intensity of light can cause transpiration in plants which will inhibit photosynthesis. Also, the longer the plant is exposed to sunlight, the longer the photosynthesis will continue to take place.
Optimal concentration of $C{O_2}$ is also essential for photosynthesis. Lesser or excessive $C{O_2}$ can inhibit photosynthesis. Photosynthesis enhances with increase in temperature. But beyond the optimum levels, the enzymes are deactivated and photosynthesis stops.
Water has an indirect effect on photosynthesis. Reduced water availability will lead to closure of stomata. If stomata are closed, $C{O_2}$ intake also stops which affects photosynthesis. Oxygen is very much needed for photosynthesis. It is required in photorespiration in $C3$ plants. The by-product of photorespiration is $C{O_2}$ which is very much essential for photosynthesis.

Note:
Photosynthesis in plants is governed by Blackman’s Principle of Limiting Factors. The principle states that “when a process is governed by more than one factor, the rate of the process is governed by that factor which is closest to its minimum value”. For example, if a leaf is exposed to a constant amount of light intensity and temperature but the $C{O_2}$ available is less, the rate of photosynthesis will not increase with an increase in the light intensity or temperature. The $C{O_2}$ acts as the limiting factor.