Fig. 6

Average chlorophyll fluorescence transients (average of 7–8 samples, A) and the different expressions of relative variable fluorescence: (C) between F_o and F_m: \( {\text{V}}_{\text{t}} = \left( {{\text{F}}_{\text{t}} - {\text{F}}_{\text{o}} } \right)/\left( {{\text{F}}_{\text{m}} - {\text{F}}_{\text{o}} } \right) \) and (D) the differences of the six samples to the reference sample treated with 6000 μM N (ΔV_t), (E) between F_o and F_300 μs: \( {\text{W}}_{\text{K}} = \left( {{\text{F}}_{\text{t}} - {\text{F}}_{\text{o}} } \right)/\left( {{\text{F}}_{{ 300 \upmu{\text{s}}}} - {\text{F}}_{\text{o}} } \right) \) and F the differences of the six samples to the reference sample (ΔW_K), (B) IP phase: \( \left( {{\text{F}}_{\text{t}} - {\text{F}}_{\text{o}} } \right)/\left( {{\text{F}}_{\text{I}} - {\text{F}}_{\text{o}} } \right) {-} 1 = \left( {{\text{F}}_{\text{t}} - {\text{F}}_{\text{I}} } \right)/\left( {{\text{F}}_{\text{I}} - {\text{F}}_{\text{o}} } \right) \) in dark-adapted tea leaves under different N supply (0, 50, 100, 300, 1200 and 6000 μmol L⁻¹)