Different Action of Auxin-A and of Hetero-Auxin (Preliminary Note)

It is well known that unilateral growth hormone application to young coleoptiles and hypocotyls causes negative curvatures (growth substance curvatures) in these organs. Light affects these curvatures as has been shown in an earlier paper (Van Overbeek 1933) for the hypocotyls of Raphanus. Light also has an effect on the growth substance curvatures of Avena coleoptiles, as will be shown below.