Plant hormones, also known as phytohormones or plant growth regulators, are chemical substances produced by plants in various parts of their bodies. These hormones play a crucial role in controlling and regulating plant growth, development, and responses to environmental stimuli. There are five main classes of plant hormones:
1. Auxins: Auxins stimulate cell elongation, regulate apical dominance (the suppression of lateral bud growth), promote root formation, and coordinate tropisms (growth responses to stimuli such as light, gravity, and touch).
2. Gibberellins: Gibberellins promote stem and leaf elongation, seed germination, flowering, and fruit development. They also help in breaking dormancy in buds and seeds.
3. Cytokinins: Cytokinins promote cell division and differentiation, delay senescence (aging), and regulate the balance between shoot and root growth. They are also involved in stimulating lateral bud growth.
4. Abscisic Acid (ABA): ABA regulates seed dormancy, helps in stomatal closure during water stress to prevent water loss, inhibits bud growth, and promotes leaf senescence.
5. Ethylene: Ethylene is involved in various processes, including fruit ripening, leaf and flower senescence, and the abscission (shedding) of leaves, flowers, and fruits. It is also produced in response to stress, such as mechanical damage or pathogen attack, and can promote plant defense mechanisms.
These plant hormones work in a complex interplay, with each hormone having specific functions and interactions with others to regulate plant growth and development.
what are plant hormones
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