THE PHOTOTROPIC RESPONSES OF AVENA COLEOPTILES

Abstract

The various phototropic curvatures of the oat coleoptile are presented in a three-dimensional diagram. Three positive responses can be distinguished, separated by areas of negative or at least decreased curvatures. The reciprocity law is valid for two of the positive responses and one negative response. A third positive response is initiated over a large range of intensities at a fixed stimulus duration. The slope of its increase with stimulus duration, however, depends on light intensity.