Resumo

JARA-ROJAS, Francisco et al. Model Validation for Estimating the Leaf Stomatal Conductance in cv. Cabernet Sauvignon Grapevines . Chilean J. Agric. Res. [online]. 2009, vol.69, n.1, pp. 88-96. ISSN 0718-5839.  http://dx.doi.org/10.4067/S0718-58392009000100011.

The coupled model of assimilation and stomatal conductance (A-g_s) 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 (g_m), maximum specific humidity (D_max) 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-g_s which allowed simultaneous measuring of the leaf net CO₂ assimilation (A) and stomatal conductance (g_s) in 2 to 3 h intervals of time. The calibration indicated that the g_m,, D_max 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-g_s 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-g_s model is affected considerably by the g_m, D_max and f₀ parameterization.

Palavras-chave : A-g_s model; photosynthesis; mesophyll conductance; stem water potential; sensitivity analysis.