A carbon cost-gain model explains the observed patterns of xylem safety and efficiency

Teemu Holtta, Maurizio Mencuccini, Eero Nikinmaa

Research output: Contribution to journalArticlepeer-review

Abstract

Efficient water transport from the soil to the leaves is essential for plant function, while building and maintaining the water transport structure in the xylem require a major proportion of the assimilated carbon of the tree. Xylem transport also faces additional challenges as water in the xylem is under tension and therefore cavitation cannot be completely avoided. We constructed a model that calculates the xylem structure that maximizes carbon-use efficiency while simultaneously taking into account pit structure in increasing the resistance to water transport and constricting the spreading of embolisms. The optimal xylem structure predicted by the model was found to correspond well to the generally observed trends: xylem conduits grew in size from the apex towards the base while simultaneously decreasing in number, and vulnerability to cavitation increased with conduit size. These trends were caused primarily by the axial water potential gradient in the xylem. The pits have to be less porous near the apex where water potential is lower to restrict the spreading of embolisms, while whole-plant carbon-use efficiency demands that conduit size decreases and conduit number increases simultaneously. The model predictions remained qualitatively the same regardless of the exact optimality criterion used for defining carbon-use efficiency.

Original languageEnglish
Pages (from-to)1819-1834
Number of pages16
JournalPlant, Cell and Environment
Volume34
Issue number11
DOIs
Publication statusPublished - Nov 2011

Keywords

  • cavitation
  • conduit tapering
  • hydraulic architecture
  • Murray's law
  • optimality
  • pipe model
  • pit membrane
  • WBE model
  • AIR-SEEDING THRESHOLDS
  • BORDERED PIT FUNCTION
  • HYDRAULIC RESISTANCE
  • WATER TRANSPORT
  • ANGIOSPERM VESSELS
  • STOMATAL CONTROL
  • WOOD DENSITY
  • SUGAR MAPLE
  • TALL TREES
  • CAVITATION

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