Coordination of leaf structure and gas exchange along a height gradient in a tall conifer Public Deposited

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  • The gravitational component of water potential and frictional resistance during transpiration lead to substantial reductions in leaf water potential (Wl) near the tops of tall trees, which can influence both leaf growth and physiology. We examined the relationships between morphological features and gas exchange in foliage collected near the tops of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees of different height classes ranging from 5 to 55 m. This sampling allowed us to investigate the effects of tree height on leaf structural characteristics in the absence of potentially confounding factors such as irradiance, temperature, relative humidity and branch length. The use of cut foliage for measurement of intrinsic gas-exchange characteristics allowed identification of height-related trends without the immediate influences of path length and gravity. Stomatal density, needle length, needle width and needle area declined with increasing tree height by 0.70 mm 2 m 1, 0.20 mm m 1, 5.9 · 10 3 mm m 1 and 0.012 mm2 m 1, respectively. Needle thickness and mesophyll thickness increased with tree height by 4.8 · 10 2 mm m 1 and 0.74 lm m 1, respectively. Mesophyll conductance (gm) and CO2 assimilation in ambient [CO2] (Aamb) decreased by 1.1 mmol m 2 s 1 per m and 0.082 lmol m 2 s 1 per m increase in height, respectively. Mean reductions in gm and Aamb of foliage from 5 to 55 m were 47% and 42%, respectively. The observed trend in Aamb was associated with gm and several leaf anatomic characteristics that are likely to be determined by the prevailing vertical tension gradient during foliar development. A linear increase in foliar d13C values with height (0.042& m 1) implied that relative stomatal and mesophyll limitations of photosynthesis in intact shoots increased with height. These data suggest that increasing height leads to both fixed structural constraints on leaf gas exchange and dynamic constraints related to prevailing stomatal behavior.
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  • Woodruff, D. R., F. C. Meinzer, B. Lachenbruch, and D. M. Johnson. 2009. Coordination of leaf structure and gas exchange along a height gradient in a tall conifer. Tree Physiology 29: 261-272
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  • description.provenance : Approved for entry into archive by Sue Kunda(sue.kunda@oregonstate.edu) on 2010-10-01T16:20:46Z (GMT) No. of bitstreams: 1 Woodruff_09_TreePhys_LfStructure HtGradient.pdf: 336368 bytes, checksum: d92b896b7be42d8eefbf30b15ed06352 (MD5)
  • description.provenance : Made available in DSpace on 2010-10-01T16:20:46Z (GMT). No. of bitstreams: 1 Woodruff_09_TreePhys_LfStructure HtGradient.pdf: 336368 bytes, checksum: d92b896b7be42d8eefbf30b15ed06352 (MD5) Previous issue date: 2009
  • description.provenance : Submitted by Barbara Lachenbruch (barb.lachenbruch@oregonstate.edu) on 2010-09-29T15:48:49Z No. of bitstreams: 1 Woodruff_09_TreePhys_LfStructure HtGradient.pdf: 336368 bytes, checksum: d92b896b7be42d8eefbf30b15ed06352 (MD5)

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