Figure 1.

Potential variability in the estimation of mesophyll conductance after a step change in light. Mesophyll conductance (g_m) was measured every 100 s (A) for 10 min in darkness followed by 50 min under a PPFD of 1,000-μmol photons m⁻² s⁻¹ in Arabidopsis (blue), and (C) for 10 min in darkness followed by 50 min under a PPFD of 1,500-μmol photons m⁻² s⁻¹ in tobacco (red), respectively. CO₂ concentration and air temperature in the leaf chamber were set to 400 µmol mol⁻¹ and 24°C, respectively. A sensitivity of g_m was evaluated in (B) Arabidopsis and (D) tobacco by changing the value of day respiration rate in the light (R_d), CO₂ concentration in intercellular airspaces (C_i), discrimination in the carboxylation reaction by Rubisco and PEPC (b), and the observed carbon isotope discrimination (Δ_o) using data collected 10 (dark) and 40 min (pale) after the light was turned on. The vertical bars on each plot indicate the standard deviation (A, C) or standard error (B, D) with 6–8 replicate leaves for Arabidopsis and 3–6 leaves for tobacco. The numbers (0, 1,000, and 1,500) in the grey and white boxes at the top of (A) and (C) indicate the light intensity.