5 × α × PAR × Φ PSII Rate of linear electron transport in PSII at given photosynthetic active irradiance (PAR), assuming that there is equal partitioning of absorbed light between PSI and PSII (constant value 0.5)4,5  NPQ = (F m − F m ′)/F m ′ Non-photochemical quenching3,8  qP = (F m ′ − F s ′)/(F m ′ − F 0 ′) Coefficient of photochemical quenching based on the “puddle” model (i.e., unconnected PSII units)2,4,6  qL = qP × (F 0/F s ′) Coefficient of photochemical quenching based on the “lake” model (i.e., fully connected PSII units)12  qCU = (F m ′ − F s ′)/((p/(1–p)) × (F s − F 0 ′) + F m ′ − F 0 ′) Coefficient

of photochemical quenching based on the “connected units model” model (intermediate model)11,13 parameter p is defined in Table 2. selleck chemical  Φ NO = 1/[NPQ + 1 + qL(F m/F 0 − 1) Quantum yield of non-regulated energy dissipation in PSII13  Φ NPQ = 1 − Φ YAP-TEAD Inhibitor 1 PSII − Φ NO Quantum yield of pH-dependent energy dissipation in PSII13 Based on 1 Kitajima and Butler (1975);

2 Schreiber (1986); 3 Schreiber et al. (1988); 4 Björkman and Demmig (1987); 5 Genty et al. (1989); 6 Bilger and Björkman (1990); 7 Krause and Weis (1991); 8 Walters and Horton (1991); 9 Evans (1993); 10 Schreiber et al. (1995); 11 Lavergne and Trissl (1995); 12 Oxborough and Baker (1997); 13 Kramer et al. (2004)   3. Protocol for studying the

effect of HL was as described below First, photochemical efficiency of PSII (ΦPSII) was Cell Cycle inhibitor calculated from fluorescence measurements in leaves after they were kept in dark for 30 min. This was followed by a 15-min exposure to 50 μmol photons m−2 s−1 of light. Thereafter, leaves were exposed for 1 h to 1,500 μmol photons m−2 s−1 (obtained from an external halogen lamp, 2050-HB, with a filter eliminating wavelengths of light above 710 nm). During this time, 4 saturation light flashes (16,000 μmol photons m−2 s−1) were applied every 15 min. After 1, 5, and 15 min of dark period recovery from HL, ΦPSII (Butler 1978; Quick and Stitt 1989; Havaux et al. 1991) was obtained.   4. ChlF induction curve was measured using Handy-PEA fluorimeter (Hansatech Instruments Ltd., UK). Ribonucleotide reductase First, we measured fluorescence transient from leaves kept in darkness for 30 min; this was our control. Then, we applied HL (see above); and fluorescence transient was measured 30 min after recovery from light. Fast fluorescence transients, thus obtained, were analyzed by the so-called “JIP test” (Strasser and Strasser 1995; Srivastava et al. 1999; Strasser et al. 2000, 2004, 2010; for the assumptions used, and pros and cons, see Stirbet and Govindjee 2011). The measured and calculated JIP parameters are described in Table 2.