Which of these influences growth movement in plants?

Step 1: Analyze the question The question asks which substance influences growth movement in plants. Growth movements are called tropisms (e.g., phototropism, geotropism). They happen when different parts of a plant grow at different rates in response to a stimulus.

Step 2: Explain the concept Tropisms are controlled by plant growth hormones, especially auxins (such as indoleacetic acid, IAA). Auxins are made at the shoot tip and move down the stem. They affect cell elongation:

• Phototropism: Light causes auxin to move to the shaded side of the shoot. Cells on that side elongate more, so the shoot bends toward the light.
• Geotropism: Auxin collects on the lower side of a horizontal root or shoot. This inhibits growth in roots and promotes growth in shoots, so roots bend downward and shoots bend upward.

Step 3: Check each option

• A. Acetic acid: An organic acid, not a plant growth regulator. Wrong.
• B. Auxins: The hormones that control cell elongation and tropic growth movements. Correct.
• C. Chlorophyll: The pigment that traps light energy for photosynthesis. It does not control growth movement.
• D. Enzyme: Enzymes speed up biochemical reactions in general. They are not specific to growth movements.
• E. Ethylene: A plant hormone that mainly promotes fruit ripening and leaf fall (abscission). It is not the main hormone behind tropic growth movements.

Step 4: Answer The correct option is B. Auxins.

Tip: Link the words "growth movement" or "tropism" with auxin. Link "ripening" with ethylene. These two pairings appear often in NECO, WASSCE and JAMB Biology.