Question

Statement I: C3 weeds such as Avena fatua, Phalaris minor and Chenopodium album are generally more competitive than C4 weeds especially at higher temperature conditions.
Statement II: In C4 weeds photosynthesis occurs via the Calvin-Benson Cycle and the first stable product is phosphoglyceric acid.
In light of the above statements, choose the correct answer from the options given below:

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Hint:

C4 pathway: first stable product is OAA.
C3 pathway: first stable product is PGA.
C4 weeds are more competitive at higher temperatures.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
C3 and C4 plants differ in photosynthesis pathway.
Weeds also fall into these categories.

Step 2: Key Formula or Approach:
No specific formula.
Need to understand C3 and C4 photosynthesis.

Step 3: Detailed Explanation:
Statement I: C3 weeds are more competitive than C4 weeds at higher temperatures.
This is true because C3 plants are better adapted to cooler conditions.
At high temperatures, C4 plants have an advantage.
Statement II: In C4 weeds, photosynthesis occurs via the C4 pathway.
The first stable product is oxaloacetic acid (OAA), not phosphoglyceric acid (PGA).
PGA is the first stable product in C3 plants.
Thus, Statement II is false.

Step 4: Final Answer:
Statement I is true but Statement II is false.
Hence, the correct option is (C).