CO₂ Enrichment Effects on C₃ Plants — NEET Biology
📚 Practice ConceptThe fact that C₃ plants respond to higher CO₂ concentration by showing increased rates of photosynthesis leading to higher productivity 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.
Which of the following statements are NOT correct regarding factors affecting photosynthesis, particularly in a controlled environment like a well-lit greenhouse? S1: In a well-ventilated greenhouse, CO₂ availability for C₃ plants is rarely a limiting factor under optimal light and temperature conditions. S2: The practice of CO₂ enrichment in greenhouses is primarily aimed at enhancing the photosynthetic rate of C₄ plants by minimizing their photorespiration. S3: If the temperature in a greenhouse rises significantly above the optimum range for C₃ plants, it can become a limiting factor for photosynthesis, even with ample light and CO₂. S4: Even in a well-lit greenhouse, water stress can indirectly limit photosynthesis by inducing stomatal closure, thereby reducing CO₂ availability. S5: Blackman's Law of Limiting Factors applies, stating that the rate of photosynthesis is determined by the factor closest to its minimal value.
View solution & NCERT explanation
Correct answer: A — S1 and S2
Let's evaluate each statement to identify the incorrect ones: S1: This statement is NOT correct. NCERT states that current CO₂ levels (0.03-0.04 percent) are limiting to C₃ plants. The fact that CO₂ enrichment is used in greenhouses for crops like tomatoes and bell pepper (which are typically C₃ plants) indicates that CO₂ availability is often a limiting factor, not rarely. S2: This statement is NOT correct. CO₂ enrichment in greenhouses primarily benefits C₃ plants, as their photosynthesis rates increase significantly with higher CO₂ concentrations up to 450 µlL⁻¹. C₄ plants already have mechanisms to concentrate CO₂ and saturate at lower concentrations (around 360 µlL⁻¹), and photorespiration is negligible in C₄ plants. The main purpose is to increase productivity in C₃ plants, not primarily to mitigate photorespiration in C₄ plants. S3: This statement is correct. Dark reactions are temperature controlled, and C₃ plants have a much lower temperature optimum (20-25°C) compared to tropical C₄ plants. Therefore, high temperatures can indeed become a limiting factor. S4: This statement is correct. NCERT explains that water stress causes stomata to close, which reduces CO₂ availability, and also makes leaves wilt, reducing surface area and metabolic activity, all of which limit photosynthesis. S5: This statement is correct. Blackman’s (1905) Law of Limiting Factors states that if a chemical process is affected by more than one factor, its rate will be determined by the factor which is nearest to its minimal value. Therefore, S1 and S2 are the NOT correct statements.
What does NCERT say about fact that C plants?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.