| Abstract | dc.description.abstract | The aim of this study was to investigate, during
the summer of the year 2008, the variation in leaf water and
photosynthetic characteristics of Eucryphia cordifolia Cav.
(Cunoniaceae) along its broad latitudinal distribution in central
south Chile (36° to 42° S). The latitudinal variation in
water potential (Ψw), water potential at saturation (Ψπsat),
water potential at the turgor lost point (Ψπtlp), stomatal density
of the leaves, leaf nitrogen concentrations and photosynthetic
light response were studied in eight populations. The
populations located in the northern region of the distribution
of E. cordifolia had the lowest leaf water potential. Osmotic
potential at full turgor was highest in the two southernmost
populations and gradually decreased towards the northernmost
points. Similarly, osmotic potential at zero turgor was
the lowest in the northern population. On the contrary, the
symplastic water content was lower in the two southernmost
populations. The highest net photosynthesis rate was recorded
for plants in the populations of intermediate distributions,
and it was dependent on the precipitation and
temperature gradient. The northern populations, which are
subject to the lowest precipitations, showed the lowest stomatal
densities, which were tightly linked with stomatal conductance
variation. Therefore, the variability of Amax was
independent of stomatal density and conductance, so that
the northern populations, subject to environments with less
water availability, presented higher photosynthetic water use
efficiency. Photosynthesis variations were also not associated
with changes in leaf water potential or in nitrogen content
in E. cordifolia leaves, which did not show any consistent
latitudinal or altitudinal trend. In conclusion, the results support
our hypothesis that the leaf water relations, stomatal
characteristics and photosynthetic rates of the leaf would
vary along its latitudinal gradient, helping to explain the
ability of E. cordifolia trees to inhabit a broad latitudinal
and altitudinal range throughout the central south Chile. | en_US |
