Fig. 4

Morphology of surface and inner C. regularis cells cultivated under two conditions (nitrogen limitation and P 45 mg L⁻¹, N_limP45, a–c; nitrogen limitation and P 250 mg L⁻¹, N_limP250, d–f) with beneficial and inhibition effects for growth. The subfigures in b and e show representative enlarged views of cells. The red, blue, orange, and green arrows indicate light colored cells, large sized cells, fold structure, and lysed cells devoid of recognizable contents, respectively. cw cell wall, pm plasma membrane, m mitochondria