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Atrazine resistance entails a limited xanthophyll cycle activity, a lower PSII efficiency and an altered pattern of excess excitation dissipation
Author(s) -
Váradi Gyula,
Polyánka Hilda,
Darkó Éva,
Lehoczki Endre
Publication year - 2003
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2003.00089.x
Subject(s) - xanthophyll , excitation , dissipation , atrazine , chemistry , biophysics , biology , photosynthesis , physics , biochemistry , agronomy , thermodynamics , pesticide , quantum mechanics
Atrazine‐resistant (AR) weeds have a modified D1 protein structure, with a Ser 264 →Gly mutation on the D1 protein, near the plastoquinone binding niche. The photosynthetic performance, the light response of the xanthophyll cycle and chlorophyll fluorescence quenching‐related parameters were compared in attached leaves of susceptible (S) and AR biotypes of the C 3 dicot Chenopodium album L., Epilobium adenocaulon Hausskn., Erigeron canadensis L., Senecio vulgaris L. and Solanum nigrum L. and the C 4 dicot Amaranthus retroflexus L. grown under natural high‐light conditions. No significant difference in CO 2 assimilation rate per leaf area unit was found between the S and AR biotypes of the investigated C 3 plants, whereas the AR biotype of A. retroflexus exhibited a relatively poor photosynthetic performance. The D1 protein mutant plants expressed a reduced activity of light‐stimulated zeaxanthin formation. Neither the lower violaxanthin de‐epoxidase activity nor the depletion of ascorbate seems to be the cause of the lower in vivo zeaxanthin formation in the AR plants. All the D1 mutant weeds had limited light‐induced non‐photochemical (NPQ) and photochemical (q P ) quenching capacities, and displayed a higher photosensitivity, as characterized by the ratio (1‐q P )/NPQ and a higher susceptibility to photoinhibition. Analysis of the chlorophyll fluorescence parameters showed that a lower proportion of excitation energy was allocated to PSII photochemistry, while a higher excess of excitation remained in the AR weeds relative to the S plants.