Cytokinins are plant hormones that are derivatives of the purine adenine. (They are not to be confused with cytokines.)
They were discovered as an absolutely essential ingredient in medium for growing plant cells in culture. [View] Without cytokinins in the medium, plant cells will not divide by mitosis.
Cytokinins have been implicated in many plant activities; usually along with some other plant hormone such as auxin or ethylene.Among these:
One of the clearest examples of cytokinin activity occurs in the germination of seeds. The endosperm of monocot seeds, such as corn (maize), contains large stores of the precursor to the cytokinin zeatin (right). When the corn kernel germinates, zeatin moves from the endosperm to the root tip where it stimulates vigorous mitosis.The steps in cytokinin signaling:
|Other plant hormones|
|Abscisic acid (ABA)||Auxin||Brassinosteroids||Ethylene||Gibberellins||Jasmonates||Strigolactones|
|As you read about these various hormones, you will note that: (1) each hormone affects several, or even many, different processes and |
(2) each process is, in turn, influenced by several different hormones.
How these overlapping signals are integrated to produce a particular response remains a topic of active research.