© 2005 Heron Publishing—Victoria, Canada
Mechanical perturbation affects conductivity, mechanical properties and aboveground biomass of hybrid poplars
Kristine A. Kern (1), Frank W. Ewers (1, 2), Frank W. Telewski (3) and Lothar Koehler (1)
1. Department of Plant Biology, Michigan State University, East Lansing, MI, 48824, USA / 2. Corresponding author (ewers@msu.edu) / 3. Department of Plant Biology, W.J. Beal Botanical Garden, Michigan State University, East Lansing, MI 48824, USA / Received May 10, 2004; accepted December 11, 2004; published online August 1, 2005
Summary
Xylem development in trees is affected by dynamic mechanical stresses imposed on stems by wind. To assess clonal differences
in response to mechanical perturbation (MP), we subjected seven greenhouse-grown F1 hybrids of Populus trichocarpa Torr. & A. Gray. × P. deltoides Bartr. ex Marsh. to a standard MP treatment consisting of 20 manually imposed stem flexures per day for 70–90 days. Effects
of MP on aboveground biomass, hydraulic conductivity (kh), specific conductivity (ks), flexural stiffness (EI), modulus of elasticity (MOE) and modulus of rupture (MOR) were determined. Treatment increased
stem radial growth and decreased height growth, leaf area and total aboveground biomass. It also significantly decreased ks, MOE and MOR, but significantly increased EI and wood specific gravity in most clones. Mechanical perturbation caused greater
stem rigidity, without having a significant effect on whole-stem kh or percent loss of conductivity due to embolism. Maximum kh was positively correlated with EI in both control (r2 = 0.54, P < 0.0001) and MP-treated (r2 = 0.61, P < 0.0001) plants, and ks and MOE were positively correlated with percent vessel lumen area (r2 = 0.45, P < 0.0001 and r2 = 0.28, P = 0.002, respectively). Thus, contrary to our expectation of a trade-off between conductivity and wood strength, there may
be an opportunity to select clones for woody biomass production that are superior in both mechanical strength and hydraulic
conductivity, as is the triploid Clone 19-61.
Keywords:
hydraulic conductivity, Populus, thigmomorphogenesis, vessel anatomy, wind stress, xylem, Young’s modulus of elasticity.
