Changes in Levels of Cellular Constituents of Dunaliella parva Associated with Inorganic Phosphate Depletion

Abstract: The effect of phosphorous limitation on some physiological and biochemical parameters of the green alga Dunaliella parva have been examined. Algal cells were cultured under conditions of either Pi limitation or nutrient sufficiency. At the end of the experiment and under phosphorus limitation conditions the percent of decrease in number of cells and growth rate reached 58.4 % and 36.3 % respectively, while the generation time increased by 2.21 days compared to nutrient sufficient medium. The content of chlorophyll fractions, glycerol,-carotene, total soluble carbohydrates and proteins were also significantly reduced in response to phosphorus limitation. The photosynthetic and respiratory activities in nutrient sufficient control medium increased gradually till the 12 days of culturing where at the 16 day they decreased by 8.9 % and 17.8 % forth th photosynthesis and respiration, respectively. Phosphorous limitation resulted in 36.8 % lower rate of respiration and 65.5 % decline in rate of photosynthesis at the 16 day of culturing compared to control. The results clearedth also that D. parva when cultured under phosphorous starvation conditions, growth of the alga was the most sensitive parameter followed by photosynthesis then respiration. Key words: Phosphorous limitation Photosynthesis Respiration Growth rate Dunaliella parva Algae INTRODUCTION Phosphate appears also to be required for the Inspite of its absence in nature phosphate is limitation should thus directly reduce metal uptake as has frequently the limiting nutrient in many environments been observed in studies of nickel uptake b