An investigation into the mode of action of the herbicide M&B 39279

Derrick, P.M., 1989. An investigation into the mode of action of the herbicide M&B 39279. PhD, Nottingham Trent University.

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Abstract

This thesis describes an investigation into the mode of action of the novel herbicide M&B 39279 in two target weed species.

The herbicide acifluorfen was investigated alongside M&B 39279 in experiments to enable comparison of the activity of M&B 39279 with acifluorfen, a nitrodiphenylether herbicide which generates similar toxic symptoms in plants to those induced by M&B 39279. These two herbicides behaved indistinguishably throughout the study. It was proposed that these compounds share a common mode of action.

Both herbicides were shown to be light dependent, contact herbicides which caused necrosis of plant leaves. These toxicity symptoms were not accompanied by any changes in primary metabolism beyond those expected of moribund plants.

Blue and red light were shown to be the most active regions of the visible spectrum with these herbicides and low light intensities were sufficient to mediate their toxicity.

Diuron suppressed activity of M&B 39279 and acifluorfen although these compounds had no significant direct effect on thylakoid electron transfer and photophosphorylation.

The sequence of effects of M&B 39279 and acifluorfen on subcellular morphology was established by electron microscopy. Vesiculisation of chloroplast envelopes was the most rapid symptom of damage on an ultrastructural level in Galium aparine. Ultrastructural changes were accompanied by a decline in photosynthetic capability, loss of chlorophyll, leakage of electrolytes and malondialdehyde in leaflets maintained under identical conditions implying the occurrence of a peroxidative destruction of membrane lipids.

A decline in photosynthesis was the most sensitive response of excised G.aparine leaves and protoplasts to M&B 39279 and acifluorfen. Although photosynthesis declined after a short time lag, it proceeded evolution of short chain hydrocarbons by at least four hours in protoplasts.

Evidence is presented to support recent proposals suggesting that acifluorfen and M&B 39279 act via inhibition of protoporphyrinogen oxidase leading to an accumulation of the photosensitiser protoporphyrin IX, and thereby initiating lethal lipid peroxidation.

Item Type:	Thesis
Creators:	Derrick, P.M.
Date:	1989
ISBN:	9781369324303
Identifiers:	Number Type PQ10290181 Other
Rights:	This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without the author's prior written consent.
Divisions:	Schools > School of Science and Technology
Record created by:	Linda Sullivan
Date Added:	11 Nov 2020 15:24
Last Modified:	11 Oct 2023 10:10
URI:	https://irep.ntu.ac.uk/id/eprint/41619

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