Abstract
The effects of the pyridinone herbicide, fluridone, on the growth, pigment content and composition, and photosynthetic capability of Oscillatoria agardhii Gomont were investigated. Batch-culture flasks were inoculated with equal amounts of culture volume from an exponentially-growing culture and subjected to fluridone concentrations ranging from 0 to 100 μg. 1- i. Culture populations were allowed to grow without interruption for 96 h after which populations were analyzed. Biomass, and chlorophyll a and total carotenoid contents decreased with increasing fluridone concentration. No change was observed in C-phycocyanin content. Within the lipophilic pigment fraction, decreases in the relative abundances of myxoxanthophyll, zeaxanthin, β-carotene, and an unidentified, minor carotenoid caused corresponding increases in the relative abundance of chlorophyll a. The light-limited slope, the maximum light-saturated rate of photosynthetic O 2 evolution, and the irradiance value at onset of light saturation decreased with increasing fluridone concentration. Inhibition of growth and chlorophyll content was considered a secondary response attributable to the photo-oxidation of chlorophyll molecules. Inhibition of the photosynthetic efficiency and maximum were attributed to reduced carotenoid content.
Published Version
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