title: Allelopathic Monoterpenes Interfere with Arabidopsis thaliana Cuticular Waxes and Enhance Transpiration.
abstract: Exposure to the allelopathic monoterpenes camphor (100 mg/10 L) and menthol (50 mg/10 L) for 24 h enhanced transpiration of Arabidopsis thaliana fully developed rosette leaves similar to de-waxing. As ascertained by ESEM analyses the leaf surfaces were spotted with platelet like structures which seem to be partly mixed with the lipophilic epicuticular layers. The structures are supposed to contain the condensed monoterpenes, which could be identified by GC. Long term exposure (more than 48 h) to 100 mg/50 mg killed the plants by desiccation, a 24 h exposure caused necrotic spots that became visible one to two days after the treatment. Examinations of the stomatal apertures indicated that monoterpenes induced stomatal opening followed by extreme swelling and a final break down of the protoplasts. Exposure of Arabidopsis thaliana to volatiles of Mentha piperita, Lavandula latifolia and Artemisia camphorata resulted in a dramatic increase of the stomata aperture but swelling of the protoplasts was less exhibited.In contrast to de-waxing, expression of the fatty acid condensing enzyme encoding CER6 gene and de novo synthesis of CER6 protein was not induced after 24 h of exposure to the monoterpenes.The aim of the study was to demonstrate that the lipophilic layers of the leaf surface and the stomata are primary targets of monoterpene allelopathic attack. Enhanced transpiration results from a combination of affected lipophilic wax layers and a disturbed stomata function.
authors.affiliation: IMBIO Institut für Molekulare Physiologie und Biotechnologie der Pflanzen; Universität Bonn; Bonn, Germany.
authors.forename: Margot
authors.initials: M
authors.lastname: Schulz
authors.forename: Petra
authors.initials: P
authors.lastname: Kussmann
authors.forename: Mona
authors.initials: M
authors.lastname: Knop
authors.forename: Bettina
authors.initials: B
authors.lastname: Kriegs
authors.forename: Frank
authors.initials: F
authors.lastname: Gresens
authors.forename: Thomas
authors.initials: T
authors.lastname: Eichert
authors.forename: Andreas
authors.initials: A
authors.lastname: Ulbrich
authors.forename: Friedhelm
authors.initials: F
authors.lastname: Marx
authors.forename: Heinz
authors.initials: H
authors.lastname: Fabricius
authors.forename: Heiner
authors.initials: H
authors.lastname: Goldbach
authors.forename: Georg
authors.initials: G
authors.lastname: Noga