Potted cuttings of three Eucalyptus globulus Labill.
clones (AR3, CN44, MP11) were grown over 6 months in a greenhouse under three
watering regimes: well watered (HW), moderate soil water deficit (MS) and
severe soil water deficit (SS). Transpiration efficiency
(W = total dry matter/water transpired) and
leaf intrinsic gas exchange efficiency
(A/gs = carbon assimilation
rate/stomatal conductance) increased under water stress and were
positively correlated with the stable carbon isotope composition of leaf
tissue (δ13C). The clones did not vary
significantly with respect to A/gs
and W. However, statistically significant differences were detected among
clones in δ13C, A and
biomass. W did not differ between the MS and SS regimes,
probably due to plant acclimation to increasing soil water deficits. The
increase in W with soil water deficits relative to the
well watered control was primarily associated with stomatal closure, but was
also influenced by differences in respiratory carbon losses
(?c) and variation in the leaf-to-air water vapour
difference (v). Variance in
?c and v may explain
partially why the two levels of soil water deficit were different in regard to
δ13C but not in terms of W.
Metabolic responses to water deficit in two Eucalyptus globulus clones with contrasting drought sensitivity
