Cytokinins are plant growth regulators that promote cell division. They are made mainly in root tips and in developing seeds and fruits, and are transported up the plant in the xylem.Effects of cytokinins- Cell division: cytokinins stimulate cell division in meristems, working together with auxin.
- Lateral bud growth: cytokinins promote the growth of lateral buds, opposing the inhibitory effect of auxin in apical dominance.
- Delaying leaf senescence: cytokinins slow the ageing of leaves, keeping them green and photosynthesising for longer. Leaves detached from a plant age quickly, partly because they lose their supply of cytokinins from the roots.
- Stomata: cytokinins can promote the opening of stomata.Cytokinins and tissue cultureIn plant tissue culture (micropropagation), a small piece of plant tissue is grown on a medium containing nutrients and growth regulators. The ratio of cytokinin to auxin controls what develops:- roughly equal amounts: an undifferentiated mass of cells called a callus forms;
- high cytokinin to auxin: shoots develop;
- high auxin to cytokinin: roots develop.This lets growers produce large numbers of genetically identical plants from one parent plant.Commercial usesCytokinins are used in tissue culture. They can also be applied to cut flowers and harvested leafy vegetables, such as lettuce, to delay yellowing and keep them fresh for longer.
- Lateral bud growth: cytokinins promote the growth of lateral buds, opposing the inhibitory effect of auxin in apical dominance.
- Delaying leaf senescence: cytokinins slow the ageing of leaves, keeping them green and photosynthesising for longer. Leaves detached from a plant age quickly, partly because they lose their supply of cytokinins from the roots.
- Stomata: cytokinins can promote the opening of stomata.Cytokinins and tissue cultureIn plant tissue culture (micropropagation), a small piece of plant tissue is grown on a medium containing nutrients and growth regulators. The ratio of cytokinin to auxin controls what develops:- roughly equal amounts: an undifferentiated mass of cells called a callus forms;
- high cytokinin to auxin: shoots develop;
- high auxin to cytokinin: roots develop.This lets growers produce large numbers of genetically identical plants from one parent plant.Commercial usesCytokinins are used in tissue culture. They can also be applied to cut flowers and harvested leafy vegetables, such as lettuce, to delay yellowing and keep them fresh for longer.