Fig. 2.

Changes in the total carbon of starch and of TAG, in cell number, and in CO₂ assimilation activity during N deprivation. (A) Time-course of starch and TAG formation. Dunaliella tertiolecta cells were pre-labeled for 48 h in complete growth medium with 50 mM [¹⁴C]bicarbonate and then transferred to N-deficient medium containing the same [¹⁴C]bicarbonate concentration for 8 d. Samples were withdrawn at the indicated times, lipids were extracted and separated, and the ¹⁴C contents in starch and in TAG were determined. Results are expressed in nmol C 10⁶ cells⁻¹ (means of three independent experiments). (B). Daily changes in de novo synthesis activity of TAG and of PLs during the progress of N deprivation. Dunaliella tertiolecta cells were pulse-labeled for 24 h with [¹⁴C]PlA during each day of 8 d of N deprivation. Lipids were extracted, separated, and analyzed for ¹⁴C content as described in the Materials and methods (means ± SD of three independent experiments). (C). Cell proliferation and changes in photosynthetic CO₂ assimilation. Dunaliella tertiolecta cells were cultured in N-deprived growth medium for 7 d. Each day samples were taken to determine cell number and CO₂ uptake activity as described in the Materials and methods (means ± SD of three independent experiments). (This figure is available in colour at JXB online.)