title: Growth of Avena coleoptiles and pH drop of protoplast suspensions induced by chlorinated indoleacetic acids.
abstract: Several indoleacetic acids, substituted in the benzene ring, were compared in the Avena straight growth bioassay. 4-Chloroindoleacetic acid, a naturally occurring plant hormone, is one of the strongest hormones in this bioassay. With an optimum at 10(-6) mol l(-1), it is more active than indoleacetic acid, 2,4-dichlorphenoxyacetic acid and naphthaleneacetic acid. 5-Chloro- and 6-chloroindoleacetic acids are very strong auxins as well. Other derivatives tested have a lower activity. 5,7-Dichloro- and 5-hydroxyindoleacetic acids have very low auxin activity at 10(-4) mol l(-1) and may be anti-auxins. Some of the derivatives were compared for their effect on pH decline in stem protoplast suspensions of Helianthus annuus L. and Pisum sativum L. The change of pH occurs without a lag period or with only a very short one. Derivatives which are very active in the Avena straight growth assay cause a larger pH decline than indoleacetic acid, while inactive derivatives cause effectively no pH decline.
authors.affiliation: Institut für Allgemeine Botanik der Universität, Junguisstraße 6, D-2000, Hamburg 36, Federal Republic of Germany.
authors.forename: M
authors.initials: M
authors.lastname: Böttger
authors.forename: K C
authors.initials: KC
authors.lastname: Engvild
authors.forename: H
authors.initials: H
authors.lastname: Soll