Which one among the following is a plant hormone?

Gibberellins are a major class of plant hormones that regulate various physiological processes, including stem elongation, seed germination, and fruit ripening [1]. They were originally identified from the fungus Gibberella fujikuroi, which caused rice plants to grow excessively tall [2]. Unlike the other options, gibberellins specifically promote growth in plants by helping in the growth of the stem and promoting cell division [1]. In contrast, insulin is an animal hormone produced by the pancreas to regulate glucose metabolism [4]. Thyroxin is produced by the thyroid gland in animals to regulate metabolism and growth [5]. Estrogen is a primary female sex hormone produced in the ovaries, responsible for reproductive functions and physical development in animals [6]. Therefore, gibberellin is the only plant hormone among the choices provided.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 6: Control and Coordination > Activity 6.2 > p. 108
2. [2] https://pmc.ncbi.nlm.nih.gov/articles/PMC4002599/
3. [3] https://pmc.ncbi.nlm.nih.gov/articles/PMC6761896/
4. [4] https://www.ncbi.nlm.nih.gov/books/NBK613062/
5. [5] Science , class X (NCERT 2025 ed.) > Chapter 6: Control and Coordination > Do You Know? > p. 110
6. [6] Science , class X (NCERT 2025 ed.) > Chapter 7: How do Organisms Reproduce? > 7.3.3 (b) Female Reproductive System > p. 123