Analysis of Increasing Glyphosate Resistance and Growth-promoting Effects in Soybean by Desmodesmus subspicatus
[Objective]This study is to characterize the tolerance of Desmodesmus subspicatus,a microalga,to glyphosate as well as effects of adsorbing or degrading glyphosate.Also it is to evaluate the effects of D.subspicatus application on improving glyphosate resistance and promoting growth of soybean(Glycine max)seedlings,and removing glyphosate residues from rhizosphere.These findings may offer new insights into elucidation of the absorption or degradation mechanism of glyphosate and other organophosphorus pesticides by microalgae.[Method]Different dosages of glyphosate were added to the liquid medium,respectively,in which D.subspicatus was cultured for 5 d.Then microalgal growth and photosynthesis,together with glyphosate residue in the culture solution were examined.Glyphosate was added to the soybean seedling hydroponic solution for 7 d of cultivation,and then the growth and photosynthesis of soybean seedlings were measured.The algal cultures of D.subspicatus were added to the soybean seedling hydroponic solution for 14 d of cultivation under glyphosate stress.After that,physiological parameters were examined for the soybean seedlings,followed by analyzing levels of glyphosate residues in both the seedlings and hydroponic solution.[Result]The D.subspicatus had a certain degree of tolerance to glyphosate and maintained effective growth under 100 mg/L glyphosate stress.The removal rate of glyphosates added to the culture solution was high up to 72.26％after 5-day cultivation of the microalga.Glyphosate stress significantly inhibited soybean seedling growth.D.subspicatus application enhanced the plant height,root length,fresh weight and dry weight of soybean seedlings cultivated in the glyphosate-stressed solution by 15.98％,49.03％,49.20％and 25.63％,respectively,compared with the glyphosate-stressed controls.Similarly,values of chlorophyll fluorescence parameters Y(Ⅱ),ETR and Fv/Fm increased while NPQ value decreased.Importantly,glyphosate residues in the soybean seedlings and the culture solution significantly reduced by 26.3％and 34.6％,respectively.[Conclusion]D.subspicatus cells could absorb or degrade glyphosate in large quantities.The application of D.subspicatus may effectively alleviate the damage of glyphosate stress on the photosynthesis of soybean seedlings,and also significantly reduce the absorption and enrichment of glyphosate in soybean seedlings,thus promoting soybean seedling growth and blocking the migration of glyphosate residues.
Desmodesmus subspicatussoybean seedlingglyphosate residueresistance to stressgrowth-promoting effect
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