© 2007 Heron Publishing—Victoria, Canada
The ecological and functional correlates of nocturnal transpiration
Christian O. Marks (1-3) and Martin J. Lechowicz (1)
1. Biology Department, McGill University, 1205 Dr. Penfield Avenue, Montreal, QC, H3A 1B1, Canada / 2. Present address: Department of Ecology, Evolution, and Behavior, University of Minnesota, 100 Ecology Building, 1987 Upper
Buford Circle, St. Paul, MN 55108-6097, USA / 3. Corresponding author (marks071@umn.edu) / Received May 17, 2006; accepted October 10, 2006; published online January 2, 2007
Summary
Contrary to the conventional theory of optimal stomatal control, there is substantial transpiration at night in many tree
species, but the functional significance of this phenomenon remains uncertain. To investigate the possible roles of nocturnal
transpiration, we compared and contrasted the correlations of both nocturnal and diurnal sap flow with a range of traits in
21 temperate deciduous tree species. These traits included soil water affinity, shade tolerance, cold hardiness, nitrogen
concentration of tissues, minimum transpiration rate of excised leaves, growth rate, photosynthetic capacity, stomatal length
and density, and the water potential and relative water content of leaves at the wilting point. Nocturnal sap flow was higher
in species with higher leaf nitrogen concentrations, higher rates of extension growth and lower shade tolerances. Diurnal
sap flow was higher in species with higher leaf nitrogen concentrations and photosynthetic capacities on a leaf area basis.
Because leaf metabolism and dark respiration, in particular, are strongly related to leaf nitrogen concentration, our findings
suggest that nocturnal transpiration functions to sustain carbohydrate export and other processes driven by dark respiration,
and that this function is most important in fast- growing shade-intolerant tree species.
Keywords:
growth rate, leaf nitrogen concentration, nocturnal transpiration, photosynthetic capacity, sap flow, shade tolerance, water-use
strategy.
