A METHOD FOR MEASUREMENT OF CELL‐ELONGATION‐PROMOTING ACTIVITY OF PLANT GROWTH‐REGULATORS

Abstract

THE NAME auxin was introduced by K6gl and Haagen Smit (1931) to designate a particular substance (auxentriolic acid) which they had isolated from urine and which exhibited activity in the Avenra curvature test of Went (1928). Later, a second compound (auxenolonic acid) with similar activity and closely related structure was obtained from corn germ oil and termed auxin b (Kogl et al., 1933), the first substance being then specified as auxin a. When still later a third active compound of quite different structure was isolated from urine it was named heteroauxin (K6gl et al., 1934). The identification of heteroauxin as indole-3acetic acid led rapidly to the discovery that a considerable number of compounds possess activity in the Avena test. Subsequently the generic term auxins has been endowed with a number of different meanings by various workers. Some use it very broadly to embrace all chemicals with plant growthregulatory activity of any kind, while others employ it in a much narrower sense to cover only those substances which bring about growth by cell elongation, and still other investigators would further limit the term to compounds active in the so-called standard Avena curvature test. The last restriction seems unduly arbitrary and would appear to be unfortunate if it tends to obscure the contribution to understanding of the mode of action of these substances that can be made by other techniques which also depend upon stimulation of cell enlargement.