Previous Year Question

The carbon fertilisation effect refers to an increase in the rate of photosynthesis and growth in some plants due to an increased concentration of carbon dioxide in the atmosphere.

During photosynthesis, plants use energy from sunlight to produce carbohydrates from carbon dioxide and water.

Carbon dioxide is an essential raw material for photosynthesis. Under favourable conditions, its increased availability may increase the rate of photosynthesis.

The carbon fertilisation effect is generally more pronounced in C₃ plants, such as rice, wheat and soybean.

In C₃ plants, an increased CO₂ concentration can reduce photorespiration and increase the efficiency of carbon fixation.

C₄ plants, such as maize and sugarcane, possess an internal mechanism for concentrating CO₂. Therefore, their direct response to additional CO₂ may be comparatively smaller under normal conditions.

Increased CO₂ may cause the stomata of plants to close partially. This can reduce transpiration and increase water-use efficiency.

The carbon fertilisation effect is not unlimited. Actual plant growth also depends on water, nitrogen, phosphorus, temperature, light, soil and other environmental conditions.

When nutrients or water are deficient, an increased concentration of CO₂ alone will not produce the expected increase in plant growth.

Under increased CO₂, carbohydrates may increase in some food crops, while the concentrations of protein and certain micronutrients such as iron and zinc may decrease.

Option (b) describes the greenhouse effect of carbon dioxide, not carbon fertilisation.

Option (c) describes ocean acidification, in which carbonic acid is formed when seawater absorbs CO₂.

Option (d) describes biological adaptation to climate change, not carbon fertilisation.

Therefore, carbon fertilisation is best described as increased plant growth due to an increased concentration of atmospheric CO₂.