Further Experiments on the Inhibition of the Development of Lateral Buds by Growth Hormone

The inhibition of lateral buds brought about by the application of growth substance after decapitation is not due to a stimulation of the growth of the experimental plants, since inhibition is complete without any accompanying increase in stem length or thickness. The application of two different crystalline preparations of growth substance, auxin B and Hetero-auxin, to decapitated Pisum shows these to be at least as active in causing inhibition as the impure preparation from Rhizopus, when used in the same growth substance concentrations. A third crystalline compound, auxin A, which had lost most of its growth-promoting activity produced no inhibition. The inhibition produced by the application of the growth hormone is not accompanied by any injury to the plant.