Cytokinins are a type of phytohormone capable of stimulating cell division, (hence its name). They work together with the auxins and were discovered after the search of a series of molecules capable of stimulating the proliferation of cells in vegetable tissue cultures.

Natural cytokinins have been discovered in coconut milk, tomato juice, roots and tubers. A good source of natural cytokinins are fruits and immature seeds. Thus, a natural source of cytokinins is the malt extract, which is nothing more than germinating barley or wheat seeds.

Cytokinins are also synthesized by microorganisms (bacteria and fungi), most of them phytopathogens, for example: Agrobacterium tumefaciens, Pseudomonas savastanoi or the fungus Plasmodiophora brassicae). These microorganisms produce and secrete cytokinins or cause the plants to synthesize them, which causes important alterations in their development.

Among their functions, cytokinins stimulate cell division, proliferation of axillary buds (rupture of apical dominance, have morphogenic action to induce the formation of organs. In this aspect they are closely related to auxins, so that, in plant tissue cultures, the balance between auxin and cytokinin causes caulogenesis (auxin balance/ cytokinin-friendly cytokinin), or rhizogenesis (auxin/cytokinin balance favorable to auxin). In this way, cytokinins have a role in coordinating the development of roots and stems. They are easily absorbed by the roots, providing information to the stems about their nutritional status.

Cytokinins delay leaf senescence by delaying the disappearance of chlorophyll and protein degradation. They are mobilizing agents of numerous substances, directing them towards the areas of the plant where they are applied. Together with the light they control the germination and the synthesis of pigments.