Abstract
We investigated how leaf hydraulic conductance (Kleaf) of loblolly pine trees is influenced by soil nitrogen amendment (N) in stands subjected to ambient or elevated CO
2 concentrations CO
2 a and CO
2 e, respectively). We also examined how Kleaf varies with changes in reference leaf water potential (Yleaf-ref) and stomatal conductance (gs-ref) calculated at vapour pressure deficit, D of 1 kPa.We detected significant reductions in Kleaf caused by N and CO
2e, but neither treatment affected pre-dawn or midday Yleaf.We also detected a significant CO
2 e-induced reduction in gs-ref and Yleaf-ref. Among treatments, the sensitivity ofKleaf toYleaf was directly related to a reference Kleaf (Kleaf-ref computed at Yleaf-ref). This liquid-phase response was reflected in a similar gas-phase response, with gs sensitivity to D proportional to gs-ref. Because leaves represented a substantial component of the whole-tree conductance, reduction in Kleaf under CO
2 e affected whole-tree water use by inducing a decline in gs-ref. The consequences of the acclimation of leaves to the treatments were: (1) trees growing under CO
2 e controlled morning leaf water status less than CO
2 a trees resulting in a higher diurnal loss of Kleaf; (2) the effect of CO
2 e on gs-ref was manifested only during times of high soil moisture.
Keywords
capacitance,
embolism,
reference conductances,
reference leaf water potential,
time constant,
turgor loss point
Citation
Plant, Cell & Environment: 1-13