Applying auxin to cut shoots causes the growth of roots. Gardeners use this to grow new plants from plant cuttings. Usually the cut stem is dipped in rooting powder containing auxin.Auxins are also used in micropropagation and tissue culture. During micropropagation a small piece of stem, root or leaf is removed from the plant (explant), sterilised, placed in a growth medium until it forms a clump of cells called a callus. The callus is placed in a sterile culture medium which contains a balance of auxin and cytokinin. The auxin causes root growth.