The effects of phosphorus starvation on phosphate storage, three storage products and cellular organelles of Chlorella pyrenoidosa

Abstract

The ultrastructure of phosphorus starved, phosphorus restored and total nutrient cells of Chlorella pyrenoidosa was described by i morphometric analysis. The rate of phosphorus incorporation into polyphosphate bodies of phosphorus starved cells was described as a volume fraction of the whole cell volume over a 210 min period. Maximum phosphorus incorporation into polyphosphate bodies of phosphorus starved cells occurred in the first 30 min of exposure to phosphorus. After 180 min exposure, the volume fraction of the polyphosphate bodie's of these cells decreased significantly. Several different trends were observed in the volume fractions of other cellular components. The volume fraction of starch in the chloroplast was significantly larger in the total nutrient cells than in cells of any other treatment. Lipids and pyrenoid volume fractions were significantly higher in phosphorus starved and phosphorus restored cells than in total nutrient cells. Phosphorus starved cells had the smallest volume fraction of vacuoles. Upon exposure to phosphorus, the vacuolar volume fraction increased until it equalled that of total nutrient cells. No significant differences in the volume fractions of the chloroplast, nucleus or mitochondrion were observed for any treatment.