title: Phenotypic plasticity of leaves enhances water-stress tolerance and promotes hydraulic conductivity in a tall conifer.
abstract: Leaves respond to environmental signals and acclimate to local conditions until their ecological limits are reached. Understanding the relationships between anatomical variation in leaves and the availability of water and light improves our ability to predict ecosystem-level impacts of foliar response to climate change, as it expands our knowledge of tree physiology.
  
  
  
  We examined foliar anatomy and morphology of the largest plant species, Sequoiadendron giganteum, from leafy shoot samples collected throughout crowns of trees up to 95 m tall and assessed the functionality of within-crown variation with a novel drought/recovery experiment.
  
  
  
  We found phenotypic variation in response to water availability in 13 anatomical traits of Sequoiadendron leaves. Shoot expansion was constrained by the hydrostatic gradient of maximum water potential, while functional traits supporting succulence and toughness were associated with sites of peak hydraulic limitation. Water-stress tolerance in experimental shoots increased dramatically with height.
  
  
  
  We propose a heat-sink function for transfusion tissue and uncover a suite of traits suggesting rapid hydraulic throughput and flexibility in water-stress tolerance investments as strategies that help this montane species reach such enormous size. Responses to water stress alter the amount of carbon stored in foliage and the rate of the eventual release of carbon.
authors.affiliation: Department of Natural Resources, American River College, 4700 College Oak Drive, Sacramento, California 95841 USA alanaroseo@gmail.com.
authors.forename: Alana R O
authors.initials: AR
authors.lastname: Chin
authors.affiliation: Department of Forestry and Wildland Resources, Humboldt State University, 1 Harpst Street, Arcata, California 95521 USA.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Sillett
mesh_terms: D000222:Adaptation, Physiological; D055864:Droughts; D010641:Phenotype; D018515:Plant Leaves / Q000502:physiology*; D018520:Plant Shoots / Q000033:anatomy & histology / Q000502:physiology; D032488:Sequoiadendron / Q000502:physiology; D013312:Stress, Physiological; D064028:Tracheophyta / Q000033:anatomy & histology / Q000502:physiology*; D014867:Water / Q000502:physiology*
chemical_list: D014867:Water
keywords: Cupressaceae; LMA; Sequoiadendron giganteum; experimental drought; hydraulic limitation; leaf anatomy; outside-xylem transport; phenotypic plasticity; succulence; transfusion tissue; water-stress tolerance