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Evaluating the CROPGRO–Soybean Model Ability to Simulate Photosynthesis Response to Carbon Dioxide Levels

^a Dep. of Agronomy, Univ. of Florida, Gainesville, FL 32611-0500
^b USDA-ARS and Dep. of Agronomy, Univ. of Florida, Gainesville, FL 32611-0965
^c Dep. of Agricultural and Biological Engineering, Univ. of Florida, Gainesville, FL 32611-0570. Florida Agric. Exp. Stn. Journal Ser. no. R-10598

View larger version (30K): [in a new window]   Fig. 1. Simulated soybean net leaf photosynthesis (A) response to PPF. Symbols are for measured data for eight different leaflets (adapted from Valle et al., 1985), and curves are for simulations using default CROPGRO photosynthetic equations. Open symbols and solid line are for ambient [CO2] (330 µmolmol–1); solid symbols and dashed line are for elevated [CO2] (660 µmol mol–1).

View larger version (29K): [in a new window]   Fig. 2. Simulated net leaf photosynthesis (A) of soybean as a function of intercellular [CO2] (Ci). Symbols are for measured data (mean ± SD, adapted from references), and curves are for simulations using default CROPGRO photosynthetic equations. Panels (a) and (b) are from Griffin and Luo (1999) for plants grown in 350 and 700 µmol CO2 mol–1, respectively; panel (c) is from Valle et al. (1985); panel (d) is from Sims et al. (1998); panel (e) and (f) are from the high- and low-light experiments, respectively, of Harley et al. (1985). Arrows indicate the intercellular [CO2] equivalent to ambient [CO2].

View larger version (36K): [in a new window]   Fig. 3. Comparison of observed (data adapted from references) and simulated net leaf photosynthesis using default CROPGRO photosynthetic equations. (a) Griffin and Luo (1999) for plants grown in 350 µmol CO2 mol–1; (b) Griffin and Luo (1999) for plants grown in 700 µmol CO2 mol–1; (c) Valle et al. (1985); (d) Sims et al. (1998); (e) Harley et al. (1985) (at high light, PPF > 2000 µmol photon m–2 s–1); and (f) Harley et al. (1985) (at low light, PPF 800 µmol m–2 s–1). Solid lines show linear regression, and dashed lines show the 1:1 line.

View larger version (30K): [in a new window]   Fig. 4. Comparison of observed (symbols) (data adapted from references) and simulated A using the default CROPGRO photosynthetic equations (dashed lines) or the full Farquhar photosynthetic equations (solid lines). (a) Griffin and Luo (1999) for plants grown in 350, (b) Griffin and Luo (1999) for plants grown in 700 µmol CO2 mol–1, (c) Sims et al. (1998), and (d) Harley et al. (1985). Arrows indicate the intercellular [CO2] equivalent to ambient [CO2] treatments.

View larger version (33K): [in a new window]   Fig. 5. Simulated soybean net Acan as a function of PPF at six [CO2]. Symbols are from observed data at 5-min intervals (adapted from Campbell et al., 1990), and curves are from simulation by the CROPGRO model using hourly PPF between 0600 and 1700 h, with assumption of PPF transmission of 0.88 (solid lines) or PPF transmission of 1.08 (dashed lines). The PPF on the x axis is external to and above the chamber walls.

View larger version (31K): [in a new window]   Fig. 6. Comparison of observed (adapted from Campbell et al., 1990) and simulated net Acan by the CROPGRO model at six [CO2], assuming PPF transmission of 1.08. Linear regression using hourly observed and simulated Acan values from 0700 to 1700 h (solid lines) and 1:1 line (dashed lines).