Fig. 2

Photosynthetic gas exchange under changing light conditions. The time course of the net photosynthetic rate (Pn; a, b) under changing light in the leaves of high nitrogen (HN; black) and low nitrogen (LN; grey) supply plants. The bar above the plot (a) shows the high (1600 μmol m^− 2 s^− 1; HL; white bar) and LL (100 μmol m^− 2 s^− 1; LL; grey bar) periods. The leaves were adapted under HL for 20–40 min until the Pn stabilized, after which the leaves were exposed to changing light. The grey bars, from left to right, represent 60, 120, 300, and 600 s of LL. The original Pn is shown in plot (a). In plot (b), the Pn under steady HL was taken as 100%, and the Pn under changing light conditions was calculated as a percentage of the Pn under steady HL. (c) The induction state of Pn (IS%) after LL intervals of different durations. (d-g) The integrated Pn during HL following 60 (d), 120 (e), 300 (f) or 600 s (g) LL intervals. Means ± SD, n = 6. The asterisks indicate significant differences at P < 0.05 between HN and LN leaves (T-test)