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STUDIES ON PLANT GROWTH‐REGULATING SUBSTANCES
Author(s) -
TOOTHILL JOYCE,
WAIN R. L.,
WIGHTMAN F.
Publication year - 1956
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1956.tb02152.x
Subject(s) - biology , halogen , avena , amino acid , stereochemistry , botany , biochemistry , chemistry , organic chemistry , alkyl
A study has been made of the growth‐regulating activity of a number of phenoxy acids possessing halogen or methyl substituents in the 2:6‐ or 33‐ positions of the nucleus. The pea curvature, Avena cylinder elongation and tomato‐leaf epinasty tests have been used for assessing biological activity. The results show that in general 3:s‐ is more closely associated with inactivity than 2:6‐ substitution. The introduction of a further halogen atom into the 4‐ position does not enhance activity in the 2:6‐ compounds but does so in the 3:s‐ derivatives. Although the 2:4:6‐trichloro‐ and 2:4:6‐tribromo‐phenoxyacetic acids are almost inactive, a:4‐dichloro‐6‐fluoro‐ and 2:4‐dibromo‐6‐fluoro‐ phenoxyacetic acids are very highly active. When a methyl group is substituted into the side‐chain of certain phenoxyacetic acids possessing 2:6‐ substituents, growth‐promoting activity is increased. Some of these findings conflict with recent theories on mode of action of phenoxy acids which are discussed in relation to the present work.