Q1. [1] medium thorough-understanding
Which of the following correctly describes the role of auxin in phototropism?
(A) Auxin is destroyed on the lit side, so cells on that side grow shorter.
(B) Auxin diffuses to the shady side of the shoot, causing cells there to elongate more, bending the plant towards light.
(C) Auxin diffuses to the lit side of the shoot, causing cells there to elongate more, bending the plant away from light.
(D) Auxin is produced equally on both sides of the shoot, but light directly stretches cells on the shady side.
- A Auxin is destroyed on the lit side, so cells on that side grow shorter.
- B Auxin diffuses to the shady side of the shoot, causing cells there to elongate more, bending the plant towards light.
- C Auxin diffuses to the lit side of the shoot, causing cells there to elongate more, bending the plant away from light.
- D Auxin is produced equally on both sides of the shoot, but light directly stretches cells on the shady side.
Generated by claude-sonnet-4-6 · 2026-06-26 01:02 · grounding rag
Model Answer
(B) Auxin diffuses to the shady side of the shoot, causing cells there to elongate more, bending the plant towards light.
Explanation
The source passage (Chapter 6) states clearly: "auxin diffuses towards the shady side of the shoot… stimulates the cells to grow longer on the side away from light… the plant appears to bend towards light." Option A (auxin destroyed) and D (equal production) are not mentioned in the text. Option C wrongly says auxin moves to the lit side.