Cytokinins: plant hormones that regulate growth and development

Structure and signalling

Chemically, most cytokinins are derivatives of adenine with various side chains; some forms are isoprenoid while others are aromatic. Perception and response use a multistep phosphorelay (a two‑component type system) that moves signals from membrane receptors to nuclear response regulators, changing gene expression and cellular behavior.

Major biological roles

Cytokinins promote mitotic activity in plant tissues and support shoot initiation and growth; they also delay leaf senescence, sustain chloroplast function and affect source–sink relationships for nutrients. Transported through the xylem, they commonly originate in roots and act systemically. Their action often depends on the balance with auxin: a high cytokinin:auxin ratio favors shoot formation, while the reverse favors root formation.

Practical uses and examples

• In tissue culture and micropropagation, cytokinins encourage shoot proliferation and organogenesis.
• Agricultural and horticultural treatments use synthetic cytokinins to influence flowering, delay senescence and improve postharvest quality.
• Research tools include natural forms and synthetic analogues to study developmental pathways and hormone crosstalk.

History and distinctions

Cytokinins were characterized in the mid‑20th century as substances that promote cell division in plant tissues. Natural cytokinins, such as zeatin related compounds, contrast with synthetic compounds like benzyladenine in stability and activity. They interact with other hormones (auxin, ethylene, abscisic acid) to produce complex developmental outcomes.

Further reading

For an introduction to plant hormones and their functions see plant hormone overview. For information on synthetic cytokinin compounds and applications, consult synthetic cytokinins. For basic explanations of cell division and growth processes influenced by cytokinins, see cell division resources.