SEARCH

SEARCH BY CITATION

Figure S1. Representative plot of net CO2 assimilation (Anet, µmol CO2 m−2 s−1) versus irradiance (µmol photons m−2 s−1) to illustrate the Kok effect and related calculations. Data are from a well-watered, ambient 'CO2'-grown replicate plant measured in February 2009 of the experiment. Solid symbols show measured rates of Anet over the 0–100 µmol photons m−2 s−1 range, with rates of leaf respiration in darkness (Rdark = 1.17 µmol CO2 m−2 s−1) shown. The break from linearity at irradiances below 40 µmol photons m−2 s−1 (dotted line) is shown, with a linear regression fitted (r2 = 0.992 for this replicate) to values between 40 and 100 µmol photons m−2 s−1 to estimate apparent rates of leaf R in the light (Rlight ‘apparent’, ◊ = 0.21 µmol CO2 m−2 s−1) at the y-axis intercept. Actual rates of Rlight (□ = 0.22 µmol CO2 m−2 s−1) that take into account changes in internal CO2 concentration (ci) that occur as irradiance declined (Kirschbaum & Farquhar 1987) are also shown 'assuming infinite internal conductance (gi)'. For this replicate, measurements of Anet were also made under saturating irradiance (1800 µmol photons m−2 s−1), yielding rates of Asat of 21.96 µmol CO2 m−2 s−1, with the underlying rates of carboxylation (Vc) and oxygenation (Vo) being 26.32 and 8.28 µmol CO2 m−2 s−1, respectively (calculated using Eqns 2 and 3 in the main text). At an irradiance of 100 µmol photons m−2 s−1, the corresponding values were: A100 = 4.24 µmol CO2 m−2 s−1, Vc100 = 5.08 µmol CO2 m−2 s−1, and Vo100 = 1.22 µmol CO2 m−2 s−1. Finally, for this replicate, actual Rlight values when assuming gi = 0.012Asat were 0.26 µmol CO2 m−2 s−1 (Eqn 5 in main text). For parameters above, Γ* was assumed to be 36.9 and 38.6 µL L−1 when assuming Ci and Cc, respectively (Von Caemmerer et al. 1994).

Figure S2. Rates of leaf respiration in the light (Rlight, µmol CO2 m−2 s−1) calculated assuming that internal conductance (gi) is infinite plotted against the corresponding Rlight values assuming an ‘estimated’ gi (gi = 0.012Asat; Evans & Von Caemmerer 1996). For the latter, we calculated cc at any given irradiance according to: cc = ci − (Anet/gi), with Rlight then being estimated via application of the Kirschbaum & Farquhar (1987) correction procedure after replacing ci with cc. For these calculations, Γ* was assumed to be 36.9 and 38.6 µL L−1 when assuming Ci and Cc, respectively (Von Caemmerer et al. 1994). Data are shown for all growth 'CO2' and water availability treatments, using data collected over the 4 month experimental period (December–March). Values shown are individual replicates. The dashed line shows the 1:1 relationship. See Supporting Information Table S2 for treatment averages of the ‘estimated’ gi values and corresponding Rlight values.

Figure S3. Rates of photosynthetic electron transport (J, µmol m−2 s−1) calculated assuming that internal conductance (gi) is infinite plotted against the corresponding J-values assuming an ‘estimated’ gi (gi = 0.012Asat; Evans & Von Caemmerer 1996). For the latter, we calculated cc at any given irradiance according to: cc = ci − (Anet/gi), with J then being estimated after replacing ci with cc. For these calculations, Γ* was assumed to be 36.9 and 38.6 µL L−1 when assuming Ci and Cc, respectively (Von Caemmerer et al. 1994). Data are shown for all growth 'CO2' and water availability treatments, using data collected over the 4 month experimental period (December–March). Values are shown for individual replicates of J calculated at two irradiances (100 and 1800 µmol m−2 s−1 PFFD). The dashed line shows the 1:1 relationship.

Figure S4. Rates of carboxylation (Vc) and oxygenation (Vo) by Rubisco (µmol m−2 s−1) calculated assuming that internal conductance (gi) is infinite plotted against the corresponding J-values assuming an ‘estimated’ gi (gi = 0.012Asat; Evans & Von Caemmerer 1996). For the latter, we calculated cc at any given irradiance according to: cc = ci − (Anet/gi), with J then being estimated via application of the Kirschbaum & Farquhar (1987) correction procedure after replacing ci with cc. For these calculations, Γ* was assumed to be 36.9 and 38.6 µL L−1 when assuming Ci and Cc, respectively (Von Caemmerer et al. 1994). Data are shown for all growth 'CO2' and water availability treatments, using data collected over the 4 month experimental period (December–March). Values are shown for individual replicates calculated at two irradiances (100 and 1800 µmol m−2 s−1 PFFD). The lines show the 1:1 relationship.

Figure S5. Plots of rates of leaf respiration in the light (Rlight) '(a) and (b)' and the ratio of Rlight to that in darkness (Rlight/Rdark) '(c) and (d)' against corresponding rates of photorespiration (i.e. oxygenation rate by Rubisco) at 1800 µmol m−2 s−1 PPFD (Vo1800) '(a) and (c)', the carboxylation rate by Rubisco at 1800 µmol m−2 s−1 PPFD (Vc1800) '(b) and (d)' in ambient (circles) and elevated (triangles) CO2 treatments. Open symbols represent the droughted plants and closed symbols represent the well-watered plants. The regression equation and associated statistics are summarized in Table 3. Values shown were calculated assuming infinite internal conductance (gi). Similar plots of Rlight and Rlight/Rdark ratios against rates of Vc and Vo 100 µmol m−2 s−1 PPFD are shown in Fig. 4 (main text). Data shown are for the two months where Rlight and light-saturated photosynthesis were measured on the same leaf (i.e. February and March only). In December and January, data on light-saturated photosynthesis were measured using adjacent leaves to those used for Rlight measurements; consequently, only data from February and March are shown in this figure.

Figure S6. Comparison of linear relationships between Rlight and photorespiration (i.e. oxygenation rate of Rubisco) at 100 µmol m−2 s−1 (Vo100) for calculations made assuming that internal conductance (gi) is infinite (left-hand panel) and assuming an ‘estimated’ gi (gi = 0.012Asat; Evans & Von Caemmerer 1996). For the latter, we calculated Cc at any given irradiance according to: Cc = Ci − (Anet/gi), with Rlight then being estimated via application of the Kirschbaum & Farquhar (1987) correction procedure after replacing Ci with Cc. Similarly, Vo100 values were calculating using J-values that employed Ci or Cc values. For these calculations, Γ* was assumed to be 36.9 and 38.6 µL L−1 when assuming Ci and Cc, respectively (Von Caemmerer et al. 1994). Data are shown for the four growth 'CO2' and water availability treatments, using data collected over the 4 month experimental period (December–March). Values shown are individual replicates.

Table S1. Means ± standard error per month and per treatment (n = 3) of Eucalyptus saligna leaves for the following variables: area-based rates of leaf respiration the light (Rlight) and dark (Rdark), carboxylation rates of Rubisco at 100 and 1800 µmol m−2 s−1 PPFD (Vc100 and Vc1800), oxygenation rates of Rubisco at 100 and 1800 µmol m−2 s−1 PPFD (Vo100 and Vo1800), net photosynthesis at 100 and 1800 µmol m−2 s−1 PPFD (A100 and Asat), ratios of leaf R (in the light and in the dark) to ‘gross’ rates of light-saturated photosynthesis (where ‘gross’ A = Asat plus Rlight), total soluble sugars, mass-based leaf nitrogen concentration (N), mass-based leaf phosphorus concentrations (P) and leaf mass per surface area (LMA). Note: gas exchange rates are for leaves measured in the mid-late morning at the prevailing ambient air temperature of each month.

Table S2. Overview of the effect of assumed internal conductance (gi) on calculated rates of leaf R in the light (Rlight; µmol CO2 m−2 s−1) for trees grown under ambient/elevated 'CO2' and well-watered/droughted conditions. Rlight/Rlight ratios are shown in parentheses. Rlight values were calculated on the assumption of an infinite internal conductance (gi) (i.e. Ci = Cc) and ‘estimated’ gi (i.e. gi = 0.012Asat) (Evans & von Caemmerer, 1996). For the latter, we calculated Cc at any given irradiance according to: Cc = Ci − (Anet/gi), with Rlight then being estimated via application of the Kirschbaum & Farquhar (1987) correction procedure after replacing Ci with Cc. For these calculations, Γ* was assumed to be 36.9 and 38.6 µL L−1 when assuming Ci and Cc, respectively (Von Caemmerer et al. 1994). Data shown are averages over the 4 month experimental period (December–March).

Table S3. Results from linear regression analysis of relationships between area-based respiration and month-to-month variations in leaf temperature (Tleaf). Rlight represents the non-photorespiratory respiration in illuminated leaves (assuming infinite internal conductance) and Rdark represents the mitochondrial respiration in dark-adapted leaves. See Fig. 2 in main text for treatment/monthly average data.

FilenameFormatSizeDescription
PCE_2465_sm_FigS1-S6-TableS1-S3.pdf216KSupporting info item

Please note: Wiley Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.