Effects of glyphosate on photosynthesis, chlorophyll fluorescence and physicochemical properties of cogongrass (Imperata cylindrical L.)

Cogongrass is one of the most destructive weed in China. It has been reported as one of the ten most troublesome weed species in the world. Therefore, developing an effective method to control this weed has become a significant and worthwhile practice. The effect of glyphosate on this weed growth was investigated during the 2009-2011 years. The photosynthesis, chlorophyll fluorescence, chlorophyll a and b content, proline content and shikimic acid content were assessed at the second, fifth, and ninth day after treatment with different concentration levels of glyphosate (0%, 0.3%, 0.5%, 1.0%, and 2.0%) in this study. Our results showed that the chlorophyll a and b content, the net photosynthetic rate (PN), effective quantum yield of photochemical energy conversion (Yield), and the relative rate of electron transport through PSII (ETR) decreased significantly after treated with different concentration levels of glyphosate. However, the photochemical quenching (qP) and the transpiration rate (E) increased significantly with damage of glyphosate. Therefore, glyphosate could constrain the growth of Cogongrass effectively by causing adverse effects on photosynthetic pigments, photosynthesis, photochemical activity and the shikimic acid pathway.