title: Understanding the effect of carbon status on stem diameter variations.
abstract: BACKGROUND
  Carbon assimilation and leaf-to-fruit sugar transport are, along with plant water status, the driving mechanisms for fruit growth. An integrated comprehension of the plant water and carbon relationships is therefore essential to better understand water and dry matter accumulation. Variations in stem diameter result from an integrated response to plant water and carbon status and are as such a valuable source of information.
  
  
  METHODS
  A mechanistic water flow and storage model was used to relate variations in stem diameter to phloem sugar loading and sugar concentration dynamics in tomato. The simulation results were compared with an independent model, simulating phloem sucrose loading at the leaf level based on photosynthesis and sugar metabolism kinetics and enabled a mechanistic interpretation of the 'one common assimilate pool' concept for tomato.
  
  
  RESULTS
  Combining stem diameter variation measurements and mechanistic modelling allowed us to distinguish instantaneous dynamics in the plant water relations and gradual variations in plant carbon status. Additionally, the model combined with stem diameter measurements enabled prediction of dynamic variables which are difficult to measure in a continuous and non-destructive way, such as xylem water potential and phloem hydrostatic potential. Finally, dynamics in phloem sugar loading and sugar concentration were distilled from stem diameter variations.
  
  
  CONCLUSIONS
  Stem diameter variations, when used in mechanistic models, have great potential to continuously monitor and interpret plant water and carbon relations under natural growing conditions.
authors.affiliation: Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium. tom.deswaef@ugent.be
authors.forename: Tom
authors.initials: T
authors.lastname: De Swaef
authors.forename: Steven M
authors.initials: SM
authors.lastname: Driever
authors.forename: Lieven
authors.initials: L
authors.lastname: Van Meulebroek
authors.forename: Lynn
authors.initials: L
authors.lastname: Vanhaecke
authors.forename: Leo F M
authors.initials: LF
authors.lastname: Marcelis
authors.forename: Kathy
authors.initials: K
authors.lastname: Steppe
mesh_terms: D015374:Biosensing Techniques; D002244:Carbon / Q000494:pharmacology*; D003198:Computer Simulation; D018551:Solanum lycopersicum / Q000033:anatomy & histology* / Q000187:drug effects*; D008954:Models, Biological; D010788:Photosynthesis / Q000187:drug effects; D053147:Plant Exudates / Q000378:metabolism; D018547:Plant Stems / Q000033:anatomy & histology* / Q000187:drug effects*; D012212:Rheology / Q000187:drug effects; D013395:Sucrose / Q000494:pharmacology; D013696:Temperature; D055548:Vapor Pressure
chemical_list: D053147:Plant Exudates; D013395:Sucrose; D002244:Carbon