title: Branch age and light conditions determine leaf-area-specific conductivity in current shoots of Scots pine.
abstract: Shoot size and other shoot properties more or less follow the availability of light, but there is also evidence that the topological position in a tree crown has an influence on shoot development. Whether the hydraulic properties of new shoots are more regulated by the light or the position affects the shoot acclimation to changing light conditions and thereby to changing evaporative demand. We investigated the leaf-area-specific conductivity (and its components sapwood-specific conductivity and Huber value) of the current-year shoots of Scots pine (Pinus sylvestris L.) in relation to light environment and topological position in three different tree classes. The light environment was quantified in terms of simulated transpiration and the topological position was quantified by parent branch age. Sample shoot measurements included length, basal and tip diameter, hydraulic conductivity of the shoot, tracheid area and density, and specific leaf area. In our results, the leaf-area-specific conductivity of new shoots declined with parent branch age and increased with simulated transpiration rate of the shoot. The relation to transpiration demand seemed more decisive, since it gave higher R(2) values than branch age and explained the differences between the tree classes. The trend of leaf-area-specific conductivity with simulated transpiration was closely related to Huber value, whereas the trend of leaf-area-specific conductivity with parent branch age was related to a similar trend in sapwood-specific conductivity.
authors.affiliation: Department of Forest Sciences, University of Helsinki, Post Office Box 27, Helsinki FI-00014, Finland leila.gronlund@helsinki.fi.
authors.forename: Leila
authors.initials: L
authors.lastname: Grönlund
authors.affiliation: Department of Forest Sciences, University of Helsinki, Post Office Box 27, Helsinki FI-00014, Finland.
authors.forename: Teemu
authors.initials: T
authors.lastname: Hölttä
authors.affiliation: Department of Forest Sciences, University of Helsinki, Post Office Box 27, Helsinki FI-00014, Finland.
authors.forename: Annikki
authors.initials: A
authors.lastname: Mäkelä
mesh_terms: D008027:Light; D041605:Pinus sylvestris / Q000378:metabolism* / Q000528:radiation effects; D018515:Plant Leaves / Q000378:metabolism* / Q000528:radiation effects; D018520:Plant Shoots / Q000378:metabolism* / Q000528:radiation effects; D018526:Plant Transpiration / Q000528:radiation effects
keywords: leaf area; sapwood; shoot structure; tree structure