Studies on the Growth Hormone of Plants

It has long been known that when the growing point of a young dicotyledonous plant is removed, the axillary buds on the stem below it begin to develop. As long as the terminal bud is present, the development of the axillary buds is inhibited. A lateral bud may also be inhibited by the rapid growth of another lateral above it, as we have found in our experiments, or opposite it, as in those of Dostal (1926). Furthermore, Snow (1929a) has shown that the inhibition, in Pisum, is principally due to the young leaves in the developing bud. The evidence indicates that this inhibition is probably caused by a special substance (see Snow, 1929b). There was reason to believe that this inhibiting substance is of the same nature as the growth-promoting substance of Avena coleoptiles, and the experiments to be described here confirm this belief.