RESUMEN
In all living cells, phosphorus plays an important function in the transport of metabolic energy and as a structural component of nucleotide and phospholipid molecules. Ni2+ is found in industrial water effluent and has the potential to harm aquatic ecosystems. The study was designed to assess the effect of phosphorous-limiting conditions in combination with the absence or presence of different concentrations of nickel on growth, pigment content, photosynthesis, and respiration activities of the studied alga Dunaliella tertiolecta. The EC50 for dissolved nickel was around 15 mg/L. Results obtained showed that, growth and chlorophyll content under phosphorus limiting conditions increased under low concentrations of dissolved nickel. The amount of O2-evolution with phosphorus limiting conditions was lower than those of untreated normal cultures. Lower dissolved nickel concentrations resulted in higher photosynthesis rates in the treated phosphorus-starved cultures than higher concentrations. The degree of response to metal toxicity in phosphorus-starved medium is depending mainly on the concentration of the element and the length of the culturing period and it was less than those in normal control culture containing phosphorus.