Plant hormones (also called plant growth regulators) play a vital role in controlling and coordinating vegetative growth — the development of roots, stems, and leaves. These hormones work together to balance growth and adapt the plant’s development to its environment.
Here’s how the main hormones regulate vegetative growth:
- Auxins:
- Promote cell elongation, especially in stems and young shoots.
- Help in root initiation and growth, which improves water and nutrient uptake.
- Control apical dominance — the main shoot grows taller while side branches stay smaller.
- Example: Indole-3-acetic acid (IAA).
- Cytokinins:
- Stimulate cell division and promote the growth of shoots and leaves.
- Work with auxins to balance root and shoot growth.
- Delay leaf aging (senescence), keeping leaves green and active longer.
- Example: Kinetin, zeatin.
- Gibberellins:
- Promote stem elongation by stimulating both cell division and elongation.
- Help expand leaves and increase overall plant height.
- Break dormancy in seeds and buds, allowing new growth to begin.
- Example: Gibberellic acid (GA₃).
- Abscisic Acid (ABA):
- Acts as a growth inhibitor during stress conditions (like drought).
- Causes stomatal closure to reduce water loss and helps the plant survive tough conditions.
- Balances growth by preventing excessive elongation.
- Ethylene:
- Influences stem thickening and leaf expansion in some plants.
- Helps plants adjust growth in response to obstacles or stress.
- Also plays a role in leaf and flower aging (senescence).
In simple terms:
- Auxins, cytokinins, and gibberellins promote vegetative growth.
- Abscisic acid and ethylene regulate and sometimes slow down growth to protect the plant.
Together, these hormones maintain a balance — ensuring healthy root, stem, and leaf growth suited to the plant’s needs and environment.