Effects of nutrient limitation on biochemical constituents of Ankistrodesmus falcatus

1. Cell size and volume changed as a function of the type of resource limitation, with nitrogen-limited cells being smaller and less dense and phosphorus-limited cells being larger and more dense than non-limited cells. 2. The major biochemical constituents of the green alga Ankistrodesmus falcatus varied as a function of nitrogen or phosphorus limitation (15% of maximum growth rate) compared to cells growing at their maximum rate. Nitrogen-limited cells had much lower protein content and phosphorus-limited cells had higher carbohydrate and lipid contents than cells growing under no limitation. 3. Phosphorus-limited cells had a higher total lipid content than either nitrogen-limited or non-limited cells, but the lipid class composition was similar. 4. The protein:lipid ratio was lowest (0.38) in the nitrogen-limited cells, intermediate in the phosphorus-limited cells (0.44) and highest in the non-limited control cells (1.14).