© 2007 Heron Publishing—Victoria, Canada
Plant size, not age, regulates growth and gas exchange in grafted Scots pine trees
D. Vanderklein (1, 5), J. Martínez-Vilalta (2, 3), S. Lee (4) and M. Mencuccini (2)
1. Department of Biology and Molecular Biology, Montclair State University, Montclair, NJ, USA / 2. School of GeoSciences, University of Edinburgh, Edinburgh, U.K. / 3. CREAF/Unitat d’Ecologia, Universitat Autònoma de Barcelona, Bellaterra, Spain / 4. Forest Research, Northern Research Station, Roslin, U.K. / 5. Corresponding author (vanderkleid@mail.montclair.edu) / Received October 2, 2005; accepted March 19, 2006; published online October 2, 2006
Summary
We studied the effect of scion donor-tree age on the physiology and growth of 6- to 7-year-old grafted Scots pine (Pinus sylvestris L.) trees (4 and 5 years after grafting). Physiological measurements included photosynthethetic rate, stomatal conductance,
transpiration, whole plant hydraulic conductance, needle nitrogen concentration and carbon isotope composition. Growth measurements
included total and component biomasses, relative growth rates and growth efficiency. Scion donor trees ranged in age from
36 to 269 years at the time of grafting. Hydraulic conductance was measured gravimetrically, applying the Ohm’s law analogy,
and directly, with a high-pressure flow meter. We found no effect of scion donor-tree age on any of the variables measured.
There was, however, great variation within scion donor-tree age groups, which was related to the size of the grafted trees.
Differences in size may have been caused by variable initial grafting success, but there was no indication that grafting success
and age were related. At the stem level, hydraulic conductance scaled with total leaf area so that total conductance per unit
leaf area did not vary with crown size. However, leaf specific hydraulic conductance (gravimetric), transpiration, photosynthesis
and stomatal conductance declined with increasing total tree leaf area and needle width. We hypothesize that needle width
is inversely related to mesophyll conductance. We conclude that canopy and needle size and not scion donor-tree age determined
gas exchange in our grafted trees.
Keywords:
aging, Caledonian pine, crown size, hydraulic limitation, leaf-level adjustment, leaf specific conductance, Pinus sylvestris
.
