If auxin transport was limited at shoot tips, what would occur? 1) No new leaves would form. 2) It would result in increased formation of leaf primordia at many locations. 3) It would have no effect on leaf formation. 4) Leaf primordia formation would be limited to the cells where auxin was transported.
The correct answer and explanation is:
Correct Answer: 4) Leaf primordia formation would be limited to the cells where auxin was transported.
Auxin is a key plant hormone that plays a major role in coordinating growth and development. One of its important functions is regulating the formation of leaf primordia, which are the early developmental stages of leaves. In the shoot apical meristem, auxin concentration must be precisely controlled and localized for proper organ patterning.
Auxin is actively transported from cell to cell, and this movement creates localized areas of high auxin concentration. These areas act as signals that trigger the formation of new leaf primordia. Specialized proteins known as PIN-FORMED (PIN) proteins help direct the flow of auxin within plant tissues, guiding it toward specific sites on the shoot tip.
If auxin transport is limited at the shoot tips, the hormone would not be able to accumulate in specific areas. This would prevent the formation of distinct auxin concentration peaks needed to initiate leaf primordia. Therefore, leaf formation would not occur broadly or randomly across the meristem, but only in cells where auxin is still successfully transported and concentrated. This explains why the formation of leaf primordia would be limited to those cells where auxin could reach.
Option 1 is incorrect because it overstates the effect; some leaf formation may still occur where auxin transport remains functional. Option 2 is inaccurate since increased primordia formation at many locations would require more widespread auxin activity, not less. Option 3 is wrong because auxin clearly influences leaf initiation, so reduced transport cannot have no effect.
Thus, the most accurate outcome of restricted auxin transport at the shoot tip is a limitation of leaf primordia formation to cells where auxin continues to be delivered, making option 4 the best answer.
