Correlations of stomatal conductance with hydraulic and chemical factors in several deciduous tree species in a natural habitat.

Recent research in whole-plant stomatal physiology, conducted largely with potted plants in controlled environments, suggests that stomatal conductance (g ) might be more closely linked to plant chemical variables than to hydraulic variables. To test this in a field situation, seasonal g was examined in relation to a number of plant and environmental variables in 11 temperate, deciduous forest tree species. Stomatal conductance was generally better correlated with environmental variables (air temperature, vapor pressure deficit, PPFD) than with plant variables, and slightly better correlated with plant hydraulic variables (shoot water and osmotic potentials) than with plant chemical variables (xylem sap ABA concentration, xylem sap pH).