Fig 3. $\Delta N/\overline{N}$ vs. ΔI for I_mean = 1.25, 3.25, 13.75 μmol m⁻² s⁻¹.

The averaged values and the standard deviations are shown by points and bars. Fitted lines are drawn by broken lines. The slopes are: 0.302 ± 0.0252 for I_mean = 1.25 μmol m⁻² s⁻¹, −0.0147 ± 0.0226 for I_mean = 3.25 μmol m⁻² s⁻¹ and −0.243 ± 0.0217 for I_mean = 13.75 μmol m⁻² s⁻¹.