Question

$C_{3}$ plants respond to the higher $CO_{2}$ concentration by showing increased rates of photosynthesis, leading to higher productivity. This feature has been used for some greenhouse crops such as

• A. Maize and sugarcane.
• B. Wheat and sorghum.
• C. Tomato and sugarcane.
• D. Millet and bell pepper.

Answer 1

Answer: (C)

Carbon dioxide is the major limiting factor for photosynthesis.
The CO2 concentration is very low in the atmosphere; between 0.03 and 0.04% (300 - 400 ppm).
This concentration of CO2 is far below the optimum requirement of photosynthesis.
The minimum CO2 concentration below which there is no net absorption of CO2and the rate of photosynthesis is equal to rate of respiration is called
compensation point.
The maximum CO2 concentration at which photosynthesis takes place but beyond which photosynthesis takes place is called saturation point.
Very high concentration of carbon dioxide causes closure of stomata. As a result rate of photosynthesis decreases.
As carbon dioxide is the major limiting factor for photosynthesis process, the C3andC4 plants respond differently to different CO2 concentrations. Both the plant group do not respond at high CO2 conditions in low light intensity. Whereas at high light intensities the rate of photosynthesis goes up in both the groups. C3 plants respond to higher CO2 concentration by showing increased rates of photosynthesis that leads to higher productivity. This characteristic has been used for some greenhouse crops such as tomatoes and bell pepper. They are allowed to grow in carbon dioxide enriched atmosphere that leads to higher yields.