title: Effects of 2,4-D, glyphosate and paraquat on growth, photosynthesis and chlorophyll-a synthesis of Scenedesmus quadricauda Berb 614.
abstract: The effects of 2,4-D, glyphosate and paraquat on growth, photosynthesis and chlorophyll-a synthesis by a freshwater green alga, Scenedesmus quadricauda Berb 614, were determined. These herbicides are the most often used in Hong Kong. Within the concentration range 0.02-200 mg/l, paraquat was more toxic than glyphosate and 2,4-D to the growth, photosynthesis and chlorophyll-a synthesis. The presence of 0.02, 0.2 or 2 mg/l of 2,4-D was not toxic to the alga. Algal growth, photosynthesis and chlorophyll-a synthesis were stimulated by the presence of low concentrations (0.02 or 0.2 and 0.02 mg/l, respectively) of 2,4-D and glyphosate. The presence of 0.02 or 0.2 mg/l of paraquat, 2 mg/l of glyphosate or 20 mg/l of 2,4-D was significantly inhibitory to the three test parameters, whereas the presence of 2 or more mg/l of paraquat, 20 or more mg/l of glyphosate or 200 mg/l of 2,4-D completely inhibited algal growth, photosynthesis and chlorophyll-a synthesis. The use of the alga as a bio-indicator of herbicide contamination in freshwater environment was discussed.
authors.affiliation: Department of Biology, The Chinese University of Hong Kong, Shatin, N. T., Hong Kong SAR, People's Republic of China. pkwong@cuhk.edu.hk
authors.forename: P K
authors.initials: PK
authors.lastname: Wong
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000009:adverse effects*; D002734:Chlorophyll / Q000096:biosynthesis*; D000077194:Chlorophyll A; D000460:Chlorophyta / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005998:Glycine / Q000009:adverse effects / Q000031:analogs & derivatives*; D006540:Herbicides / Q000009:adverse effects*; D010269:Paraquat / Q000009:adverse effects*; D010788:Photosynthesis / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000009:adverse effects; D000097797:Glyphosate
chemical_list: D015084:2,4-Dichlorophenoxyacetic Acid; D002734:Chlorophyll; D000077194:Chlorophyll A; D005998:Glycine; D006540:Herbicides; D010269:Paraquat; D014874:Water Pollutants, Chemical; D000097797:Glyphosate