Which one among the following is not a plant hormone?

The correct answer is Thyroxine.

Key Points

• Thyroxine is a hormone secreted by the thyroid gland and is not classified as a plant hormone.
• It plays a vital role in regulating metabolism, heart rate, and body temperature in animals and humans.
• Plant hormones, also known as phytohormones, include substances like gibberellins, abscisic acid, and auxins, which regulate plant growth and development.
• Gibberellins, auxins, and abscisic acid are essential for processes such as seed germination, cell elongation, and stress responses in plants.
• Thyroxine is specific to animals and humans, making it distinct from plant hormones.

Additional Information

• Plant Hormones Overview:
  • Auxins: Promote cell elongation and are involved in phototropism and gravitropism.
  • Gibberellins: Stimulate seed germination, stem elongation, and fruit development.
  • Abscisic Acid: Plays a key role in stress responses such as drought tolerance by closing stomata.
  • Cytokinins: Promote cell division and delay leaf aging.
  • Ethylene: Regulates fruit ripening and response to stress.
• Thyroxine (T4) in Humans and Animals:
  • Produced by the thyroid gland and controlled by the pituitary gland through thyroid-stimulating hormone (TSH).
  • Essential for energy metabolism, growth, and development in animals.
  • An imbalance in thyroxine levels can cause disorders such as hypothyroidism or hyperthyroidism.
• Differences Between Plant and Animal Hormones:
  • Plant hormones regulate growth, development, and responses to environmental stimuli.
  • Animal hormones, like thyroxine, regulate metabolic and physiological processes in the body.
  • Plant hormones are often multifunctional, while animal hormones have more specialized roles.
• Phytohormones vs. Synthetic Hormones:
  • Phytohormones are naturally occurring in plants, while synthetic hormones are artificially created for agricultural use.
  • Examples of synthetic plant hormones include 2,4-D (a synthetic auxin) used as a herbicide.