Question

Present level of atmospheric ${\text{CO}}_2$ is not limiting factor for which of the following photosynthetic plant category:-

• A. Wheat plants
• B. Maize plants
• C. Sugarcane plants
• D. Bryophyllum plants

Answer 1

The correct option is C Sugarcane plants

Sugarcane is a champion at photosynthesis under the right conditions and is a prime example of a ${\text{C}}_4$ plant (one which uses ${\text{C}}_4$ photosynthesis). Sugarcane has been recorded at $7\%$ photosynthetic efficiency. ${\text{C}}_4$ plants almost never saturate with light and under hot, dry conditions, they much outperform the ${\text{C}}_3$ plants.

In intercropping condition, dry weight of shoot of ${\text{C}}_4$ plants get decreased under elevated ${\text{CO}}_2$ concentration. This indicates that competitive ability of those plants get reduced in these situations. In all investigated plants, root to shoot ratio is reduced by increasing ${\text{CO}}_2$ concentration.

In ${\text{C}}_4$ plants, the ${\text{CO}}_2$ compensation point is zero or nearly zero, reflecting their very low levels of photorespiration. The ${\text{CO}}_2$, absorbed by ${\text{C}}_4$ leaves is fixed into organic acids, which maintains high levels of ${\text{CO}}_2$. The mesophyll of ${\text{C}}_3$ plants has no such mechanism of fixing ${\text{CO}}_2$.

So, the correct answer is Sugarcane plants.