Article Figures & Data
Figures
- Figure 1.
Responses of ci, A, and gs to DCMU (100 μm) fed through the transpiration stream of a detached leaf. DCMU was applied at time zero. Other conditions were as described in “Materials and Methods.”
- Figure 2.
Fluorescence and thermal images at three times following DCMU application. Images we taken of the leaf for which data are shown in Figure 1.
- Figure 3.
A and gs plotted versus the percent of image with near-zero ϕPSII and percent of image with temperatures above approximately 27°C. Data were calculated at 30-min intervals as DCMU was added to the leaf via the transpiration stream.
- Figure 4.
Responses of A and gs to ci at 2% (a) and 21% (b) O2. Lines drawn through the A data are best fits to the photosynthesis model of Farquhar et al. (1980) as described in “Materials and Methods.” Lines drawn through the gs data are hand-drawn approximations. Different symbols represent different replicate experiments. Parameters for the fitted A versus ci curves are given in Table I.
- Figure 5.
Responses of gs to ci at 21% oxygen in darkness (a) and for a DCMU-treated leaf at a PFD of 1,000 μE m−2 s−1 white light (b); and at 2% oxygen in darkness (c) and for a DCMU-treated leaf at a PFD of 1,000 μE m−2 s−1 white light (d). Different symbols represent different replicate experiments.
- Figure 6.
Responses of A (a) and gs (b; solid lines), and ci (dashed lines) to PFD with wavelengths above 500 nm. Ambient CO2 was manipulated to keep ci constant. Different symbols represent different replicates.
Tables
- Table I.
Parameters of the photosynthesis model of Farquhar et al. (1980) fitted to the relationships shown in Figure 4 between net CO2 A and ci
Values of the parameters Γ* and K′ (photorespiratory compensation point and effective Km for Rubisco, respectively) were calculated from expressions given by Farquhar et al. (1980) using values of Rubisco Km and turnover rates for carboxylation and oxygenation given by de Pury and Farquhar (1997) for 25°C.
Parameter Symbol Units PFD/[O2] 300/2 1,000/2 300/21 1,000/21 μE m−2 s−1/% Maximum velocity of carboxylation Vc,max μmol m−2 s−1 68 ± 6 90 ± 6 105 ± 38 109 ± 6 Potential electron transport rate J μmol e− m−2 s−1 40 ± 1 84 ± 3 39 ± 7 105 ± 5 Mitochondrial respiration rate Rd μmol m−2 s−1 0.7 ± 0.1 0.9 ± 0.1 1.0 ± 0.4 1.1 ± 0.1 Intercellular CO2 mole fraction at transition point ci μmol mol−1 79 ± 10 145 ± 20 35.9 181 ± 33 Photorespiratory compensation point Γ* μmol mol−1 3.4 35.9 Effective Km for carboxylation K′ μmol mol−1 502.3 811.9
