Tryptophane, tryptamine, sugars, pH and the regeneration of the physiological tip in the Avena coleoptile

In earlier investigations it was found that the geotropic reaction of decapitated coleoptile sections in auxin solutions is very sensitive to the concentration (Anker 1954, 1956). Similar sections, kept horizontally in water, can be used for determining with great precision the beginning of the regeneration of the physiological tip (Anker 1967). At 23 °C the curvature starts about 2 hours after the decapitation, the exact moment being variable due to unknown factors. In the present investigation it was tried to shorten this period by addition of “food factor” and of probable precursors of indoleacetic acid, the latter substance being considered as the auxin produced by the new tip.