Fig 2. Ammonium induces sexual morphologies in T. pseudonana CCMP1335.
(A) Proportion of sexual cells (oogonia and auxospores) relative to the total population in cultures of T. pseudonana grown in the presence of NH4Cl or NaNO3; n = 3 independent cultures, average of 300 cells counted per replicate. Oogonia and auxospores were only observed beginning in stationary phase, data are mean values, error bars are s.d.. Inset: corresponding growth curve linking the onset of stationary phase with first appearance of sexual cells on day six. (B) Sexual cells were observed in cultures with NH4Cl present at inoculation (blue hatched and solid blue bars) or following NH4Cl addition at the onset of stationary phase (yellow bars). Legend shows concentration of nitrogen source provided at inoculation and concentration of nitrogen source added at the time of the second dosing. Two control treatments were supplied 200 μM nitrogen source at inoculation only. Inset: corresponding growth curve showing the onset stationary phase and timing of 2nd nitrogen addition; n = 3 independent cultures, average of 281 cells counted per replicate, data are mean values, error bars are s.d..