Links A hormone is any chemical produced in one part of the body that has a target elsewhere in the body.
Plants have five classes of hormones.
Animals, especially chordates, have a much larger number. Hormones and enzymes serve as control chemicals in multicellular organisms. They are produced in the stem, buds, and root tips. Auxin is a plant hormone produced in the stem tip that promotes cell elongation. Auxin moves to the darker side of the plant, causing the cells there to grow larger than corresponding cells on the lighter side of the plant.