Stress factors enhancing production of algal exudates: A potential self-protective mechanism?

Abstract

Algae are known to produce extracellular organic substances under optimum conditions and increase their production under stress. The changes in amount and composition of extracellular carbohydrates and proteins of three green algae Scenedesmus quadricauda, Chlorella kessleri and Raphidocelis subcapitara (known as Selenastrum capricornutum) were studied after a 5-days' cultivation under the influence of different types of stress factors (osmotic, organic, and heavy metal stressors). NaCl enhanced the quantity of carbohydrates more than proteins. A higher increase of proteins than carbohydrates was observed after addition of 3,5-dichlorophenol, glyphosate and cadmium chloride to algal cultures. The production of dissolved organic matter differs from species to species, with the age of a culture and the type of stressor.