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Phytohormones are plant hormones which play a role in regulating cellular actives such as plant growth. These chemical messengers are also referred to as growth factors because without them, a plant cannot function and establish itself properly.

Phytohormones are critical for plant production and maintenance. These hormones can be manufactured and used by the same cell, or transported to other cells by travelling across the cellular membrane, through the xylem or phloem or with regulated transport proteins. In terms of crossing the membrane some hormones have been found to be membrane soluble, while others attach to proteins bound to the membrane (1).

Phytohormones regulate many activities including growth, reproduction, sex determination and pattern formation. These hormones are important during all stages of a plants life cycle from fertilization to full development. Additionally, during times of stress these hormones are released to help plants cope.

Some examples of phytohormones include auxin, cytokinins and strigolactones.

  1. Auxin is a chemical messenger which controls plant growth.
  2. Cytokinins assist a few processes such as cell division and root nodule development.  
  3. Strigolactones help attract mycorrhizal fungi.

Furthermore, all three of these hormones have a synergistic effect in controlling branching. Evidently, phytohormones are a critical component in plant development.