What is the primary function of the plant hormone auxin?

What is the primary function of the plant hormone auxin?

• A. Promotes cell elongation
• B. Inhibits growth
• C. Converts glucose to starch
• D. Regulates transpiration

Answer: (A)

Auxin’s main role is to promote cell elongation in plant shoots. It does this by stimulating proton pumps in the cell membrane, which lowers the cell wall pH and activates enzymes that loosen the wall. This loosening allows cells to take up water and expand, leading to the bending and growth of stems toward light (phototropism) and overall shoot elongation. The other options describe processes not driven by auxin: converting glucose to starch is a storage metabolism, transpiration is about water loss and gas exchange managed mainly by stomatal regulation and other hormones, and while auxin can influence growth in various contexts, its primary, standard function in shoots is to promote elongation rather than inhibit growth.

Auxin’s main role is to promote cell elongation in plant shoots. It does this by stimulating proton pumps in the cell membrane, which lowers the cell wall pH and activates enzymes that loosen the wall. This loosening allows cells to take up water and expand, leading to the bending and growth of stems toward light (phototropism) and overall shoot elongation.

The other options describe processes not driven by auxin: converting glucose to starch is a storage metabolism, transpiration is about water loss and gas exchange managed mainly by stomatal regulation and other hormones, and while auxin can influence growth in various contexts, its primary, standard function in shoots is to promote elongation rather than inhibit growth.