Statement-1 : C₃ and C₄ plants respond differently to CO₂ concentration.

Statement-2: At low light conditions neither group (C₃ and C₄ plants) respond to high CO₂ concentrations

Both statement I and statement II are correct.

Statement I is correct. C₃ and C₄ plants have different photosynthetic pathways and respond differently to changes in CO₂ concentration. C₄ plants have a more efficient carbon fixation mechanism that allows them to perform photosynthesis effectively even at lower CO₂ concentrations compared to C₃ plants. C₄ plants are better adapted to environments with limited CO₂ availability, such as hot and dry conditions.

Statement II is also accurate. Both C₃ and C₄ plants require adequate light for photosynthesis to occur. In low light conditions, the rate of photosynthesis in both C₃ and C4 plants can be limited, and increasing CO₂ concentration alone may not significantly enhance their photosynthetic rates. Light is a primary limiting factor for photosynthesis, and without sufficient light, the benefits of elevated CO₂ concentrations may not be fully realized.