Cytokinins

Cytokinins are a type of plant hormone or phytohormone that play a very important role in helping plants grow and stay healthy. Along with other plant hormones like auxins, gibberellins, and abscisic acid, cytokinins help plants control their development, respond to the environment, and stay balanced.

What Are Cytokinins?

Cytokinins are natural chemicals found in plants that help in cell division, especially in plant roots and shoots. These hormones are also involved in many other processes like shoot development, delaying aging (senescence), and tissue culture.

There are two main types of cytokinins:

• Natural cytokinins – like zeatin, found in corn and other plants.
• Synthetic cytokinins – like kinetin, used in laboratories and agriculture.

Functions of Cytokinins in Plants

Cytokinins have several key roles:

• Promote cell division in roots and shoots.
• Help in shoot development by stimulating shoot buds to grow.
• Delay leaf senescence (aging of leaves), keeping them green and active.
• Work with auxins to balance root and shoot growth.
• Support tissue culture and plant regeneration in labs.
• Improve nutrient mobilization by moving nutrients to parts of the plant that need them.
• Help plants respond to environmental stress like drought or injury.

How Cytokinins Work: Mechanism and Signaling

Cytokinins work by attaching to specific receptors in plant cells. This starts a signaling pathway that turns on certain genes to promote growth. This process is called the cytokinin signaling pathway.

In this pathway:

1. The cytokinin hormone binds to a receptor.
2. A signal is passed inside the cell.
3. Special genes get activated.
4. The plant shows a response, like new shoot growth or delayed aging.

Interaction With Other Hormones

Cytokinins don’t work alone. They interact with other hormones like:

• Auxins – Together, they control apical dominance (why the main stem grows more than side branches).
• Gibberellins – They combine to help in stem growth and flowering.
• Abscisic acid – Cytokinins reduce the effect of this stress hormone, helping in better growth during tough times.

Molecular and Physiological Impact

Cytokinins also play a role at the molecular level:

• They control gene expression related to cell growth.
• They manage how nutrients are used by the plant.
• They delay aging by stopping the breakdown of chlorophyll.
• They affect the plant’s reaction to light and gravity.

Cytokinins in Agriculture and Tissue Culture

In agriculture, cytokinins are used to:

• Increase crop yield.
• Delay aging of fruits and leaves.
• Promote flowering and shoot growth.

In tissue culture (a lab method to grow plants), cytokinins help:

• Grow shoots from plant cells.
• Regenerate full plants from tissues.
• Study plant development under controlled conditions.

Cytokinins for NEET and Class 11 Biology

For students preparing for NEET Biology or studying Class 11 plant growth regulators, cytokinins are an important topic. Some NCERT-based points to remember:

• Cytokinins promote cytokinesis (cell division).
• Zeatin is the most common natural cytokinin.
• They delay senescence in plants.
• Used widely in plant tissue culture.
• Often asked in neet under plant hormones.

Conclusion

Cytokinins are powerful plant hormones that help in many growth activities, from cell division to shoot development and delaying aging. They work closely with other phytohormones to support plant health. Their use in agriculture, tissue culture, and biology education makes them a very important topic to understand.

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