Studies on the Effects of Metribuzine on Phormidium and Chroococcus Species

The efficacy of metribuzine, a selective herbicide recommended for comprehensive weed control in rice, was investigated on Phormidium and Chroococcus species, common species of cyanobacteria obtained from the National Marine Cyanobacterial Facility (NFMC). A comparative study of the effects of metribuzine on both species of cyanobacteria measures their chlorophyll-a content and biochemical levels such as carbohydrate, protein, amino acid and lipid levels over 18 days of time- and dose-dependent exposure. was evaluated under laboratory conditions by Results showed that the herbicide exerted pleiotropic effects on both cyanobacterial species over the concentration range tested (2–10 μg). Chlorophyll a was more adversely affected by metribuzine at the highest concentration (10 μg) on day 18. On day 12, more than 50% inhibition of cyanobacterial growth was observed when 10 μg of metribuzine was applied. Carbohydrate, protein, amino acid, and lipid levels were reduced with herbicide, but by day 18, effects were noticeable at the highest concentrations for both cyanobacteria. Metribuzine concentrations in the 2 µg range also affected chlorophyll a and biochemical content in both cyanobacteria. Phormidium species were more affected by metribuzine than Chroococcus species. Since, Phormidium and Chroococcus species are abundant in paddy fields and can be used as inoculum for rice biofertilizer programs, protecting them from the potential residual effects of herbicides is critical to correctly managing local soil fertility.