Cytokinin

Cytokinins are plant hormones that promote cell division and regulate shoot growth, leaf aging, and nutrient allocation. Their effects depend on interactions with other hormones and environmental signals.

Cytokinin signaling: A plant signal-transduction pathway in which cytokinin receptors activate phosphorelay proteins and transcription factors. This pathway carries cytokinin signals from membrane-associated receptors to genes controlling growth.
Zeatin: A naturally occurring cytokinin found in plants, named after its discovery in maize kernels. Zeatin is a major endogenous cytokinin and a standard example of the hormone class.
Plant tissue culture: The growth of plant cells, tissues, or organs on a sterile nutrient medium. Adjusting cytokinin relative to auxin can steer cultured tissue toward shoot formation.
Folly of the Ropes: A 1950s plant tissue-culture experiment series by Carlos Miller and colleagues that led to kinetin's identification. This research found a substance that promoted cell division in cultured tobacco tissue.
Nutrient signaling in plants: The molecular processes through which plants sense nutrient availability and adjust growth and metabolism. Cytokinin participates in signaling that coordinates nutrient availability with shoot growth.
Histidine kinase: An enzyme that transfers phosphate from ATP to a histidine residue in a target protein. Several cytokinin receptors are histidine kinases that initiate the signaling phosphorelay.
Isopentenyladenine: A cytokinin with an isoprenoid side chain attached to adenine. It is a common cytokinin form in plants and a precursor to other active cytokinins.
Micropropagation: The rapid production of many plants from small explants grown under sterile conditions. Cytokinins are commonly used to stimulate shoot multiplication in culture.
Kinetin: A cytokinin first identified as a cell-division-promoting compound in degraded DNA preparations. Its discovery provided the first clear evidence for a distinct class of cell-division regulators.
Nutrient remobilization: The transfer of nutrients from aging or expendable tissues to growing or reproductive organs. Cytokinin's effects on leaf aging can alter when nutrients leave mature leaves.

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