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Which one among the following is not a plant hormone ?
Explanation
Plant hormones, or phytohormones, are signaling molecules that regulate growth and development. Major groups include auxins, which promote stem growth and cell elongation; gibberellins, which assist in stem growth and seed germination; and abscisic acid, which acts as a growth inhibitor and induces leaf wilting [4]. Other significant plant hormones include cytokinins and ethylene [4]. In contrast, thyroxine is an animal hormone produced by the thyroid gland in humans and other vertebrates [3]. It requires iodine for synthesis and plays a vital role in regulating metabolism, growth, and maturation [3]. While plant hormones are produced throughout the plant body without specialized glands, thyroxine is secreted by a specific endocrine gland. Therefore, thyroxine is not a plant hormone.
Sources
- [1] Science , class X (NCERT 2025 ed.) > Chapter 6: Control and Coordination > Activity 6.2 > p. 108
- [4] https://pubchem.ncbi.nlm.nih.gov/compound/thyroxin
- [2] Science , class X (NCERT 2025 ed.) > Chapter 6: Control and Coordination > Do You Know? > p. 110
- [3] https://www.va.gov/WHOLEHEALTHLIBRARY/docs/Hypothyroidism.pdf