Auxin is a hormone common in all plants that is responsible for the growth of shoots and development within the plant. Auxin is also responsible for the production of phototropism by promoting growth in certain directions. Auxin also helps to assist plants in elongation of the stem, roots and branches. Auxin can be found in the embryos of seeds and new leaves.
This is an image of the bud of a rose bush, where they lays a large quantity of the hormone auxin.