Factors Affecting Photosynthesis Rate — NEET Biology
📚 Practice ConceptAn understanding of the factors that affect photosynthesis is necessary. The rate of photosynthesis is very important in determining the yield of plants including crop plants. Photosynthesis is under the influence of several factors, both internal (plant) and external. The plant factors include the number, size, age and orientation of leaves, mesophyll cells and chloroplasts, internal CO₂ concentration and the amount of chlorophyll. The plant or internal factors are dependent on the genetic predisposition and the growth of the plant.
Which of the following statements are correct regarding the internal factors influencing the rate of photosynthesis? S1: Plant factors, including leaf age and orientation, are largely determined by the genetic predisposition and overall growth of the plant. S2: The number of chloroplasts, internal CO₂ concentration, and amount of chlorophyll are all classified as internal factors that affect photosynthesis. S3: Chloroplasts within the mesophyll cells are typically aligned such that they receive an optimum quantity of incident light. S4: Older leaves consistently exhibit a higher rate of photosynthesis compared to younger, expanding leaves due to a more developed vascular system. S5: While plant factors influence the rate of photosynthesis, their impact is generally less significant than that of external factors.
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Correct answer: C — S1, S2 and S3 are correct
Let's evaluate each statement regarding internal factors affecting photosynthesis: S1: This statement is correct. NCERT states that plant or internal factors are dependent on the genetic predisposition and the growth of the plant. S2: This statement is correct. NCERT lists the number of mesophyll cells and chloroplasts, internal CO₂ concentration, and the amount of chlorophyll as internal (plant) factors affecting photosynthesis. S3: This statement is correct. NCERT mentions that chloroplasts align themselves along the walls of the mesophyll cells to get the optimum quantity of the incident light. S4: This statement is incorrect. While not explicitly detailed, older leaves often have a reduced metabolic activity and senesce, generally leading to a lower, not higher, photosynthetic capacity compared to optimally mature leaves. The reason given is also not typically why older leaves would have higher rates. S5: This statement is incorrect. Internal factors determine the plant's maximum potential for photosynthesis, which can be just as significant as external factors in determining the final rate. The statement implies a lesser significance which is not accurate as internal factors set the upper limits. Therefore, statements S1, S2, and S3 are correct.
What does NCERT say about understanding factors that affect?
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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.