Fig. 3.

Time course of N compounds in an axenic A. coffeaeformis culture in response to dark/anoxic conditions (A) and light/oxic conditions (B). Cells were preincubated with ¹⁵NO₃⁻ (A) or ¹⁴NO₃⁻ (B) in the growth medium under light/oxic conditions. Experimental conditions were initiated at 0 h. ¹⁵NH₄^+* denotes isotopically labeled N compounds measured with the hypobromite assay. Intracellular NO₃⁻ concentrations are expressed in μmol/L of growth medium. Values are mean ± SD of three replicate culture tubes are shown.