ABSTRACT
Model validation for estimating the leaf stomatal conductance in cv. Cabernet Sauvignon grapevines.

Francisco Jara-Rojas1, Samuel Ortega-Farías1*, Héctor Valdés-Gómez1,2, Carlos Poblete1, and Alejandro del Pozo3
 
The coupled model of assimilation and stomatal conductance (A-gs) was evaluated to estimate leaf stomatal conductance of a drip-irrigated vineyard (Vitis vinifera L. cv. Cabernet Sauvignon) located in the Pencahue Valley (35º22’ S, 71°47’ W, 150 m.a.s.l.), Maule Region, Chile, during the 2003-2004 and the 2004-2005 growing seasons. Additionally, a calibration of the three parameters mesophyll conductance (gm), maximum specific humidity (Dmax) and coupled factor (f0) was applied on vines growing in 35 L pots. An infrared gas analyzer was used to calibrate and evaluate the A-gs which allowed simultaneous measuring of the leaf net CO2 assimilation (A) and stomatal conductance (gs) in 2 to 3 h intervals of time. The calibration indicated that the gm, Dmax and f0 values were 1.15 mm s-1, 52.31 g kg-1 and 0.90, respectively. The validation in the drip-irrigated vineyard indicated that the A-gs model was able to estimate the leaf stomatal conductance with a root mean square error (RMSE) of 0.05 mol m-2 s-1, model efficiency of 61% and agreement index of 90%. The sensitivity analysis indicated that the A-gs model is affected considerably by the gm, Dmax and f0 parameterization.
Keywords: A-gs model, photosynthesis, mesophyll conductance, stem water potential, sensitivity analysis.
1 Universidad de Talca, Facultad de Ciencias Agrarias, Centro de Investigación y Transferencia en Riego y Agroclimatología (CITRA), Casilla 747, Talca, Chile.
2 Universidad de Talca, Facultad de Ingeniería, Escuela de Bioinformática, Casilla 747, Talca, Chile.
3 Universidad de Talca, Facultad de Ciencias Agrarias, Departamento de Producción Agrícola, Casilla 747, Talca, Chile. *Corresponding Author (sortega@utalca.cl).