Effect of Some Substituted Benzoic Acids and Related Compounds on the Distribution of Callus Growth in Tobacco Stem Explants.

Open Access
Publisher Website
Google Scholar
Abstract
The capacity of tobacco (Nicotiana tabacum var. Wis. 38) stem segments to transport polarly many times the endogenous levels of indoleacetic acid (IAA) was shown by the distribution in segments after 2 hours of transport. Presumptive evidence for continuous auxin production and transport by cultured tobacco stem explants was obtained. Twenty-nine compounds, mostly substituted benzoic acids, were tested on tobacco stem explants for their effect on callus growth and distribution. It was found that 2,3,6-trichloro, 2,6-dichloro, and 2,5-dibromobenzoic acids were highly active in causing apolar distribution of callus growth; 2,5-diiodobenzoic acid was weakly active. Inactive compounds were 2,3, and 4-bromobenzoic; 2, 3, and 4-iodobenzoic; 2 and 4-nitrobenzoic; 2 and 4-acetylaminobenzoic; 2,4-dichlorobenzoic; 3,4-diiodobenzoic; 2-chloro-4-aminobenzoic; 2-chloro-5-nitrobenzoic; 2,4-dimethoxybenzoic; 2,5-dinitrobenzoic; 2,4 and 2,5-dihydroxybenzoic; 2-amino and 2-hydroxy-3,5-diiodobenzoic; and 2-hydroxy-3,5-dinitrobenzoic acids; 2,4-dichloroanisole; 3,5-diiodo-L-tyrosine; 2,6-dibromo-4-nitrophenol; and KI. Alone, the highly active compounds had no inhibitory effect on callus growth; 2,5-diiodobenzoic inhibited growth markedly. None of the compounds alone noticeably stimulated pith cell enlargement. Neither 2,5-dibromo nor 2,6-dichlorobenzoic acid affected the amount of pith cell enlargement in the presence of a stimulatory IAA level (10-5[image]). It was found that 2,3,5-triiodobenzoic acid inhibits the polar transport of IAA-[alpha] -C14 in sections of bean (Phaseolus vulgaris var. Kentucky Wonder) hypocotyl, thus confirming earlier studies by a method not dependent on extraction or bioassay of IAA.