Some Properties of Inhibitor β from Solanum tuberosum Compared to Abscisic Acid

The growth‐inhibiting effect of inhibitor β, extracted from the potato variety Majestic, was compared with the effect of abscisic acid by means of the Avena coleoptile straight‐growth test. Dose‐response curves showed that total growth inhibition is attained by inhibitor β, but this is never caused by abscisic acid even in high unphysiological doses. By chromatographic methods inhibitor β can be separated into three active components. One of these is a phenolic substance with weak growth‐inhibiting effect. The two others contribute equally to the inhibitory effect, and one of them is probably abscisic acid. Beside these inhibiting substances there are components without inhibitory effect, many of phenolic character, included in the inhibitor β complex.