Butachlor induces some physiological and biochemical changes in a rice field biofertilizer cyanobacterium

• Butachlor induces some physiological and biochemical changes in Nostoc sp.
• High levels of butachlor inhibit the growth, pigments synthesis, and PSII activity.
• High levels of butachlor trigger dramatic intracellular antioxidant response.

Butachlor has been widely applied in rice field in China. However, concerns are also raised about its potential adverse impacts on non-target organisms. In the present study, butachlor was found be able to induce toxic effects on a rice field biofertilizer cyanobacterium Nostoc sp. When treated with 80 mg L−1 butachlor, significant decline in the growth rate, concentrations of chlorophyll a (Chla), carotenoids (Cars), phycobiliproteins (PBPs) and; the minimal fluorescence yield (F0), fluorescence intensity at the J-step of OJIP (Fj), the maximum fluorescence yield (Fm), the potential quantum yield (Qy), the quantum yield of electron transport (ΦE0), the maximum quantum yield of primary photochemistry (ΦP0), and the performance index on absorption basis (PIABS) (14.2%, 39.5%, 55.5%, 34.8%, 38.5%, 19.8%, 18.7%, 20.4%, 10.1%, 10.3%, and 26.4%, respectively) was observed in Nostoc sp. In contrast, significant increase in Cars/Chla, PBPs/Chla, the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and, glutathione reductase (GR), content of malonaldehyde (MDA), the absorption flux per reaction center (ABS/RC) and the effective dissipation per reaction center (DI0/RC) for 0.45, 0.65, 2.36, 2.47, 1.08, 1.16, 0.87, 0.122 and 0.205 fold was also detected by comparing with the control group. These results demonstrated that high concentration of butachlor could inhibit the growth, synthesis of pigments, and photosystem II (PSII) activities of Nostoc sp., and trigger dramatic intracellular antioxidant response in the cells. Taken together, this study may provide important information on the understanding of the changes induced by butachlor stress in nitrogen-fixing cyanobacteria and the adaptive strategy of the alga.

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