Find the incorrect statement(s) about photosynthesis from the following :
A. The water splitting complex is associated with PS I.
B. C4 plants use the C3 pathway of CO2 fixation as the main biosynthetic pathway.
C. In C4 plants, photorespiration does not occur.
D. C3 plants exhibit ’Kranz’ anatomy.
E. ATP synthesis in chloroplast occurs through chemiosmosis.
Choose the answer from the options given below :
Correct Answer :
A and D only
Solution :
**Step 1: Review each statement about photosynthesis**
A. “The water‑splitting complex is associated with PS I.”
B. “C4 plants use the C3 pathway of CO2 fixation as the main biosynthetic pathway.”
C. “In C4 plants, photorespiration does not occur.”
D. “C3 plants exhibit ’Kranz’ anatomy.”
E. “ATP synthesis in chloroplast occurs through chemiosmosis.”
**Step 2: Determine which statements are false**
• The water‑splitting (oxygen‑evolving) complex, also called the Mn‑cluster, is a component of **photosystem II (PS II)**. It extracts electrons from H₂O and releases O₂. PS I receives electrons after they pass through the plastoquinone pool and cytochrome b₆f complex. Therefore, statement A is **incorrect**.
• Kranz anatomy refers to the concentric arrangement of bundle‑sheath and mesophyll cells that enables spatial separation of the C₄ pathway. This anatomical feature is **characteristic of C₄ plants**, not C₃ plants. Hence, statement D is **incorrect**.
**Step 3: Verify that the remaining statements are true**
• **Statement B** – C₄ plants initially fix CO₂ into a four‑carbon compound (oxaloacetate) via phosphoenolpyruvate carboxylase. The 4���C compound is then transported to bundle‑sheath cells where CO₂ is released and entered into the Calvin‑Benson (C₃) cycle. Thus, C₄ plants *do* use the C₃ pathway as the main biosynthetic route, making statement B **correct**.
• **Statement C** – Because the CO₂ concentration in bundle‑sheath cells of C₄ plants is high, the oxygenase activity of Rubisco is suppressed, and photorespiration is essentially absent. Statement C is **correct**.
• **Statement E** – The light‑dependent reactions generate a proton gradient across the thylakoid membrane. ATP synthase uses this gradient to synthesize ATP by chemiosmosis, exactly as in mitochondria. Statement E is **correct**.
**Step 4: Assemble the answer**
Since only statements A and D are false, the correct option is **“A and D only.”**
Access expert-curated educational resources and study materials—completely free.
Create, conduct, and manage professional online assessments with Mindyard. Perfect for teachers and institutes.
Copyright © 2026 Mindyard. All Rights Reserved.
 Set - 3-1782888548748.webp)
