Limiting Factors in Photosynthesis Graph

Steps:

• The graph shows photosynthesis rate increasing with light intensity until a plateau, indicating initial limitation by light then other factors.
• From P to Q, the rising curve means rate directly depends on increasing light, so light is limiting.
• From Q to R, the flat line shows no further increase despite higher light, so another factor (e.g., CO2 or temperature) limits the rate.
• Statement 1 is false as multiple factors can limit photosynthesis; statements 2 and 3 match the graph segments.

Why C is correct:

• C selects 2 and 3, aligning with the limiting factor principle: the factor in shortest supply determines the rate, shifting from light (P-Q) to others (Q-R plateau).

Why the others are wrong:

• A includes 1, but light is not the sole limiting factor overall.
• B selects only 1, ignoring the graph's plateau where other factors limit.
• D selects only 3, missing the light-limited rise in P-Q.

Final answer: C