Changes in the Xanthophyll Cycle and Fluorescence Quenching Indicate Light-Dependent Early Events in the Action of Paraquat and the Mechanism of Resistance to Paraquat in Erigeron canadensis (L.) Cronq

• Published in: Plant physiology (Bethesda) Vol. 123; no. 4; pp. 1459 - 1469
• Main Authors: VARADI, G, DARKO, E, LEHOCZKI, E
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01-08-2000
• Subjects: beta Carotene - analogs & derivatives; beta Carotene - metabolism; Bioenergetics and Photosynthesis; Biological and medical sciences; Chemical control; Chlorophylls; Chloroplasts; Dark adaptation; Fluorescence; Fundamental and applied biological sciences. Psychology; Herbicides - metabolism; Leaves; Light; Luminous intensity; Lutein - metabolism; Oxidation-Reduction; Oxygen - metabolism; Paraquat - metabolism; Parasitic plants. Weeds; Photoinhibition; Photosynthesis - physiology; Phytopathology. Animal pests. Plant and forest protection; Plant Leaves - metabolism; Plants; Plants - metabolism; Resistance mechanisms; Weeds; Xanthophylls; Conyza canadensis; Xanthophyll; Environmental factor; Compositae; Zeaxanthin; Energy dissipation; Dicotyledones; Light; Angiospermae; Violaxanthin; Pigments; Intraspecific comparison; Pesticide resistance; Mechanism of action; Chloroplast; Chlorophyll; Weed; Pesticides; Herbicide; Quaternary ammonium compound; Sensitivity resistance; Penetration; Paraquat; Spermatophyta; Photosynthesis; Chemical weed control
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.123.4.1459

Violaxanthin de-epoxidation, chlorophyll fluorescence quenching, and photosynthetic O2 evolution in the presence of paraquat (Pq) were studied in intact attached leaves of Pq-susceptible, and Pq-resistant (PqR) biotypes of Erigeron canadensis under different light conditions. Initially, similar changes were induced in the two biotypes, but the effects relaxed only in the PqR plants, indicating a Pq elimination process. The penetration of Pq into the chloroplasts of PqR plants proved to be somewhat restricted and highly light-dependent, as revealed by both the light response curves of violaxanthin de-epoxidation and fluorescence quenching and the short-term high-light pre-illumination experiments. An irregular down-regulation of the non-photochemical fluorescence quenching processes was observed, reflected by lower steady-state zeaxanthin and non-photochemical fluorescence quenching levels as compared with the corresponding non-treated high-light controls. It is concluded that light is essential not only for the initiation of the mechanism of resistance to Pq, but also for the penetration of Pq into the chloroplasts in the PqR E. canadensis. Also, the Pq elimination process may cause a modification to the regulation of the non-radiative energy dissipation in PqR plants in the presence of Pq.