Fig. 3.

Exposure of seedlings to pulses of inorganic and organic N shifts the phase of the circadian clock. (A–C) Plots of the phase shift of CCA1::LUC expression in response to a 4-h pulse of inorganic N (20 mM KNO₃/20 mM NH₄NO₃) (A), 10 mM Glu (B), or 10 mM Gln (C) against the time at which the pulse was administered to wild-type seedlings. Pulses were administered at 3-h intervals spanning one complete circadian cycle, and data were collected over the next six cycles. Phase shifts are double-plotted to emphasize the circadian pattern of the response. Phase advances (the peak in expression occurring earlier) are plotted as positive values, and delays are plotted as negative values. (D) CCA1::LUC expression of control (untreated) seedlings. In all panels, the entraining photocycle (16:8) is indicated by the vertical white (light) and gray (dark) bars. The mean ± standard error of the mean is shown.