Mode of Action of Growth Retarding Chemicals

Abstract

The effects of the growth retarding chemicals CCC (2-chloroethyl trimethylammonium chloride) and Phosfon D (tributyl-2,4-dichlorobenzylphosphonium chloride) in combination with gibberellin on leaf growth of Raphanus sativus var. acanthiformis were tested. The inhibition by CCC and Phosfon D was greatest with the highest concentrations of gibberellin. The same effects were found when IAA was present The inhibitory effect of CCC on coleoptile growth was overcome by higher concentrations of IAA but not by gibberellin. Stem segments of Alaska peas (Pisum sativum) with growth retarded by CCC did not respond to treatment with gibberellin but had their length increased by as much as 3.3 times in IAA solutions. The diffusible auxin from stem apices of pea plants whose growth was retarded by CCC was only 1/7 as much as the diffusible auxin from normal plants. The evidence presently available indicates that the growth retarding effect of CCC is due to the lowering of the auxin level in the plant.