Growth substances, also known as plant hormones or phytohormones, are naturally occurring chemical compounds that regulate various physiological processes in plants. They play a crucial role in the growth, development, and overall functioning of plants.
There are five main groups of growth substances: auxins, cytokinins, gibberellins, abscisic acid, and ethylene. Each group has distinct functions and effects on plant growth.
Auxins, for example, are essential for cell elongation, promoting the growth of shoots, and regulating apical dominance. They also stimulate the development of adventitious roots and are involved in tropic responses, such as phototropism.
Cytokinins, on the other hand, are responsible for cell division and delay senescence in plants. They are involved in the formation and growth of new organs, such as shoots and roots, and play a role in the control of apical dominance.
Gibberellins stimulate the growth of stems and leaves, as well as the elongation of cells. They also regulate seed germination, flowering, and fruit development.
Abscisic acid is involved in various processes, such as seed dormancy, control of stomatal closure, and inhibition of shoot growth. It also acts as a stress hormone, responding to adverse environmental conditions.
Ethylene is a gas hormone that influences various aspects of plant growth, including fruit ripening, senescence, and abscission (leaf or fruit drop).
Overall, growth substances are essential for the growth, development, and adaptation of plants to their environment. Their regulation and interaction ensure proper growth and functioning throughout the plant's lifecycle.
