Morphological Reactions of Germinating Seeds as Criteria for the Plant Growth Regulating Activity of Auxin-Type Chemicals

Abstract

STUDYING the plant growth regulating effects of more than one hundred chemicals, we directed our attention to the following problems, closely related to the mode of action of auxins : (1) Is there only one, common, basic (auxin-) reaction, underlying the diversity of ‘auxin-like’ growth effects? (2) Do higher plant species differ with regard to their relative sensitivity towards different auxins? (3) Is the physiological activity of potential auxin precursors to be simply explained by the conversion of the inactive precursor to the active auxin? (4) How far can species differences in the enzymatic conversion of auxin precursor to auxin explain the differences between their sensitivity to the application of auxin precursors? None of these questions has been so far answered^1–6.