Question

The external factor that is rarely a limiting factor and the factor that is a major limiting for photosynthesis, respectively, are

• A. CO₂ and temperature
• B. Light and CO₂
• C. CO₂ and H₂O
• D. Temperature and light

Answer 1

The correct option is B

Light and CO₂

Light saturation of photosynthesis occurs at $10\%$ of full sunlight. Hence light is rarely a limiting factor in nature. $C{O}_2$ makes up just $0.03\%$ of the earth's atmosphere and thus is a major limiting factor for photosynthesis.