Plant hormones, also known as phytohormones, are chemical substances produced in plants that regulate growth, development, and other physiological processes. Unlike animal hormones, they are not produced in specialized glands but in various parts of the plant, including roots, stems, leaves, and fruits. These hormones are active in very small concentrations and can have profound effects on plant growth and development. Here are some key plant hormones with their functions and examples:
Auxins:
Function: Auxins are primarily involved in the regulation of plant growth patterns. They stimulate stem elongation, root growth, and differentiation, and also play a role in phototropism (growth towards light) and gravitropism (growth in response to gravity).
Example: Indoleacetic acid (IAA) is a common naturally occurring auxin.
Gibberellins:
Function: Gibberellins stimulate stem elongation, germination, and flowering. They are also involved in breaking seed dormancy and other aspects of plant development, such as leaf and fruit growth.
Example: Gibberellic acid (GA) is one of the most well-known gibberellins.
Cytokinins:
Function: Cytokinins promote cell division and growth, stimulate shoot formation and growth, delay leaf senescence (aging), and can work in conjunction with auxins to stimulate tissue differentiation.
Example: Zeatin is a common type of cytokinin found in plants.
Ethylene:
Function: Ethylene is a gaseous hormone that is involved in the ripening of fruits, flower wilting, leaf fall, and aging processes. It also plays a role in response to stress conditions like flooding.
Example: Ethylene is not only a plant hormone but also a simple hydrocarbon gas (Câ‚‚Hâ‚„).
Abscisic Acid (ABA):
Function: ABA is often termed the “stress hormone” in plants. It plays a critical role in the closure of stomata (thus regulating water loss), seed dormancy, and inhibiting growth. It helps plants respond to environmental stress conditions like drought and salinity.
Example: Abscisic acid itself is the primary hormone in this category.
Each of these hormones can interact synergistically or antagonistically with others, providing a complex network of control that allows plants to respond dynamically to their internal and external environments.
