Toxicological Impact of Herbicides on Cyanobacteria

The use of herbicides in modern agriculture to eradicate weeds has led to serious environmental contamination resulting in a loss of growth and development of many beneficial micro-organisms. Low cost, easy availability, lax in regulatory mechanism have contributed to the continuous use of the herbicides in tropical and subtropical regions. The removal of these herbicides from soil and aquatic systems is a difficult task and as a result herbicides persist in these ecosystems for a long period of time. Cyanobacteria are a diverse group of gram-negative photosynthetic prokaryotes. Their life processes require only water, carbon dioxide, inorganic substances and light and these organisms contribute greatly to terrestrial as well as aquatic ecosystems through their ability to increase soil fertility by adding nitrogen, enhancing water holding capacity, releasing vitamins and plant stimulating hormones, adding extra cellular polysaccharides and by solubilizing phosphates. The present paper review responses of cyanobacteria to herbicides and impact of herbicides on photosynthetic pigments, photosynthesis and nitrogen assimilation by cyanobacteria. The tolerance mechanisms and herbicide biodegradation potential of cyanobacteria are also reviewed.