Table 1.

Gas exchange parameters, state transitions, and redox equilibration between plastocyanin and P ₇₀₀

Leaf gas exchange was measured on the youngest fully expanded leaf of plants grown at 350 µE m⁻² s⁻¹ light intensity. All measurements were performed at 22°C and in saturating CO₂ (2000 ppm) to repress photorespiration and determine the maximum quantum efficiency of photosynthetic CO₂ assimilation. Leaf respiration was measured after a minimum of 30 min of dark adaptation. Then, the light intensity was stepwise increased until light saturation of photosynthesis was reached, to determine the maximum capacity of leaf assimilation. Assimilation capacity was corrected for dark respiration. The maximum quantum efficiency of CO₂ assimilation was calculated in the linear range of the light response curve, between 0 and 100 µE m⁻² s⁻¹ actinic light intensity. The capacity to perform state transitions is expressed as the F_R parameter (Lunde et al., 2000). Redox equilibration between plastocyanin and P₇₀₀ during a short dark interval interrupting steady-state photosynthesis in saturating light is described by the apparent redox equilibrium constant, K_app (according to Kirchhoff et al., 2004).

Parameter	Wild type	Nt-∆psaI-1	Nt-∆psaI-5
Respiration [µmol CO2 m−2 s−1]	−1.5 ± 0.3	−1.6 ± 0.3	−1.6 ± 0.5
Assimilation capacity [µmol CO2 m−2 s−1]	31.4 ± 3.1	31.6 ± 4.1	32.0 ± 4.5
Quanta / CO2	12.3 ± 0.8	11.9 ± 0.8	12.2 ± 1.0
FR	0.72 ± 0.06	0.77 ± 0.08	0.81 ± 0.05
Kapp	14.6 ± 2.3	16.0 ± 2.1	16.3 ± 1.9