title: A global analysis of xylem vessel length in woody plants.
abstract: OBJECTIVE
  Vessels are the chief conduit for long-distance water transport in the majority of flowering plants. Vessel length is a key trait that determines plant hydraulic efficiency and safety, yet relatively little is known about this xylem feature. •
  
  
  METHODS
  We used previously published studies to generate a new global data set of vessel length in woody plants. These data were used to examine how evolutionary history, plant habit, environment, and growth ring porosity influenced vessel length. We also examined the relationship between mean vessel length and mean vessel diameter and maximum vessel length. •
  
  
  RESULTS
  Data on mean vessel length were available for stems of 130 species and on maximum vessel length for stems of 91 species. A phylogenetic analysis indicated that vessel length did not exhibit significant phylogenetic signal. Liana species had longer vessel lengths than in tree or shrub species. Vessel diameter was not predictive of mean vessel length, but maximum vessel length strongly predicted mean vessel length. Vessel length did not vary between species that differed in growth ring porosity. •
  
  
  CONCLUSIONS
  Many traits often assumed to be linked to vessel length, including growth ring porosity and vessel diameter, are not associated with vessel length when compared interspecifically. Sampling for vessel length has been nonrandom, e.g., there are virtually no data available for roots, and sampling for environment has been confounded with sampling for habit. Increased knowledge of vessel length is key to understanding the structure and function of the plant hydraulic pathway.
authors.affiliation: Department of Biology, California State University, Bakersfield, 9001 Stockdale Hwy, Bakersfield, California 93311 USA. ajacobsen@csub.edu
authors.forename: Anna L
authors.initials: AL
authors.lastname: Jacobsen
authors.forename: R Brandon
authors.initials: RB
authors.lastname: Pratt
authors.forename: Michael F
authors.initials: MF
authors.lastname: Tobin
authors.forename: Uwe G
authors.initials: UG
authors.lastname: Hacke
authors.forename: Frank W
authors.initials: FW
authors.lastname: Ewers
mesh_terms: D019684:Magnoliopsida / Q000033:anatomy & histology*; D009929:Organ Size; D010802:Phylogeny; D018547:Plant Stems / Q000033:anatomy & histology; D014934:Wood / Q000033:anatomy & histology*; D052584:Xylem / Q000033:anatomy & histology*