Solution

One important effect of cytokinins on plant cells is to delay the aging process. Plant cells, like all living cells, go through a natural aging process known as senescence. Senescence is accelerated in cells of plant parts that are cut, such as flower stems. Botanists think that plants must have a continual supply of cytokinins from the roots. Cut stems, of course, lose their source of cytokinins and therefore age rapidly. When cytokinins are sprayed on leaves of a cut stem of many species, they remain green, whereas unsprayed leaves turn yellow and die.