Cytokinins are a class of plant hormones that play a significant role in plant cell culture. They are involved in regulating cell division, growth, and differentiation in plants. In plant tissue culture, cytokinins are commonly used to stimulate cell proliferation, promote shoot regeneration, and control the balance between shoot and root development.
The key roles of cytokinins in plant cell culture are listed below:
Cell Division and Proliferation
Cytokinins are primarily known for their ability to promote cell division in plant tissues. By supplementing the culture medium with cytokinins such as kinetin, zeatin, or benzyladenine (BA), cell proliferation can be induced. Cytokinins stimulate the formation of actively dividing cells, allowing the production of callus and the establishment of cell suspension cultures.
Shoot Regeneration
Cytokinins play a crucial role in shoot regeneration from explants in plant tissue culture. They promote the outgrowth and development of shoots from callus or other explant tissues. When combined with auxins, cytokinins can induce the formation of shoots from callus cultures or the differentiation of adventitious shoots from explants. This process is widely used in micropropagation techniques to produce large numbers of identical plantlets.
Axillary Bud Activation
Cytokinins are involved in the activation and outgrowth of axillary buds, which are responsible for the development of lateral shoots. By providing cytokinins in the culture medium, the growth of lateral shoots can be stimulated, leading to the branching of plantlets. This is important for controlling the growth pattern and overall morphology of plants in tissue culture.
Shoot-to-Root Balance
Cytokinins play a role in regulating the balance between shoot and root development in plant tissue culture. The ratio of cytokinins to auxins in the culture medium influences the fate of the cultured tissue. Higher concentrations of cytokinins relative to auxins promote shoot development, while lower concentrations favour root development. This balance can be manipulated to control the growth and development of plantlets in tissue culture.
Delayed Senescence
Cytokinins have been found to delay senescence, the natural aging process in plants. They help maintain the greenness and vitality of cultured tissues by preventing the breakdown of chlorophyll and delaying the onset of senescence-related processes. This can be particularly useful for long-term maintenance of tissue cultures and preservation of valuable traits.
Overall, cytokinins are essential for plant cell culture as they promote cell division and proliferation, stimulate shoot regeneration, control shoot-to-root balance, and delay senescence. Their precise control and manipulation in culture media allow researchers to manipulate plant tissues and achieve desired growth and developmental outcomes. Cytokinins, along with other plant hormones, contribute to the success of various applications in plant tissue culture, including micropropagation, genetic transformation, and production of secondary metabolites.
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