Cytokinins: Kinetin, Zeatin and Their Role in Plant Development

Cytokinins are a class of phytohormones primarily involved in regulating cell division, shoot development, and plant growth balance. Among these, zeatin is the most biologically active and naturally occurring cytokinin, while kinetin is widely used in research and agricultural applications.

Cytokinins play a central role in:
‣ Cell division (cytokinesis)
‣ Shoot initiation and development
‣ Delay of leaf senescence
‣ Nutrient mobilisation
Zeatin, first identified in maize, is considered the primary natural cytokinin and is directly involved in regulating plant growth and development. Kinetin, although originally identified as a synthetic compound, exhibits cytokinin activity and is commonly used in plant tissue culture and formulations.
Cytokinins act in close interaction with auxins, where the auxin-to-cytokinin ratio determines plant developmental outcomes. Higher cytokinin levels favour shoot formation, while higher auxin levels promote root development.

Cytokinins are typically present at very low concentrations and can be affected by:
‣ Light exposure
‣ Temperature
‣ Enzymatic degradation within plant tissues
Matrix complexity, particularly in plant extracts and formulated products, can also influence extraction efficiency and analytical recovery.

Quantification of cytokinins such as zeatin and kinetin is important for:
‣ Evaluating plant growth regulator formulations
‣ Supporting tissue culture and propagation systems
‣ Verifying biostimulant composition
‣ Understanding plant growth balance and hormone interactions
Accurate measurement provides insight into how products may influence shoot development, senescence, and overall plant performance.