Auxins - occur naturally, can be synthesized, affect plant cell elongation, apical dominance and rooting. Which hormone primarily promotes cell elongation and apical dominance?

Auxins - occur naturally, can be synthesized, affect plant cell elongation, apical dominance and rooting. Which hormone primarily promotes cell elongation and apical dominance?

• A. Gibberellins
• B. Ethylene
• C. Cytokinins
• D. Auxins

Answer: (D)

Auxins drive both rapid cell elongation and apical dominance. They’re produced mainly in the shoot tip and move downward through the plant in a directed (polar) fashion. Auxins stimulate elongation by promoting proton pumps in the cell membrane, acidifying the cell wall, and activating enzymes that loosen the wall so cells can expand as water pressure pushes them outward. At the same time, high auxin levels in the apical region suppress the growth of lateral buds, keeping the main shoot dominant. While other hormones influence growth in different ways—gibberellins also promote elongation, cytokinins boost cell division and shoot formation, and ethylene is involved in aging and ripening—the combination of promoting elongation and enforcing apical dominance points to auxins as the primary hormone for these traits.

Auxins drive both rapid cell elongation and apical dominance. They’re produced mainly in the shoot tip and move downward through the plant in a directed (polar) fashion. Auxins stimulate elongation by promoting proton pumps in the cell membrane, acidifying the cell wall, and activating enzymes that loosen the wall so cells can expand as water pressure pushes them outward. At the same time, high auxin levels in the apical region suppress the growth of lateral buds, keeping the main shoot dominant. While other hormones influence growth in different ways—gibberellins also promote elongation, cytokinins boost cell division and shoot formation, and ethylene is involved in aging and ripening—the combination of promoting elongation and enforcing apical dominance points to auxins as the primary hormone for these traits.