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Development and verification of a water and sugar transport model using measured stem diameter variations

Veerle De Schepper (UGent) and Kathy Steppe (UGent)
(2010) JOURNAL OF EXPERIMENTAL BOTANY. 61(8). p.2083-2099
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Abstract
In trees, water and sugars are transported by xylem and phloem conduits which are hydraulically linked. A simultaneous study of both flows is interesting, since they concurrently influence important processes such as stomatal regulation and growth. A few mathematical models have already been developed to investigate the influence of both hydraulically coupled flows. However, none of these models were so far tested using real measured field data. In the present study, a comprehensive whole tree model is developed that enables simulation of the stem diameter variations driven by both the water and the sugar transport. Stem diameter variations are calculated as volume changes of both the xylem and the phloem tissue. These volume changes are dependent on: (i) water transport according to the cohesion-tension theory, (ii) sugar transport according to the Münch hypothesis, (iii) loading and unloading of sugars and (iv) irreversible turgor-driven growth. The model considers three main compartments (crown, stem and roots) and is verified by comparison with actual measured stem diameter variations and xylem sap flow rates. These measurements were performed on a young oak (Quercus robur L.) tree in controlled conditions and on an adult beech (Fagus sylvatica L.) tree in a natural forest. A good agreement was found between simulated and measured data. Hence, the model seemed to be a realistic representation of the processes observed in reality. Furthermore, the model is able to simulate several physiological variables which are relatively difficult to measure: phloem turgor, phloem osmotic pressure and the Münch’s counter flow. Simulation of these variables revealed daily dynamics in their behaviour which were mainly induced by transpiration. Some of these dynamics are experimentally confirmed in literature, while others are not.
Keywords
TREE STEMS, PHLOEM, WOODY-PLANTS, TURGOR PRESSURE, MUNCH HYPOTHESIS, RICINUS-COMMUNIS, FLOW CHARACTERISTICS, GROWTH, SAP, XYLEM, Diurnal cycles, Fagus sylvatica L, growth, modelling, Munch hypothesis, phloem translocation, Quercus robur L, sap flow, stem diameter variations, xylem

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MLA
De Schepper, Veerle, and Kathy Steppe. “Development and Verification of a Water and Sugar Transport Model Using Measured Stem Diameter Variations.” JOURNAL OF EXPERIMENTAL BOTANY, vol. 61, no. 8, 2010, pp. 2083–99, doi:10.1093/jxb/erq018.
APA
De Schepper, V., & Steppe, K. (2010). Development and verification of a water and sugar transport model using measured stem diameter variations. JOURNAL OF EXPERIMENTAL BOTANY, 61(8), 2083–2099. https://doi.org/10.1093/jxb/erq018
Chicago author-date
De Schepper, Veerle, and Kathy Steppe. 2010. “Development and Verification of a Water and Sugar Transport Model Using Measured Stem Diameter Variations.” JOURNAL OF EXPERIMENTAL BOTANY 61 (8): 2083–99. https://doi.org/10.1093/jxb/erq018.
Chicago author-date (all authors)
De Schepper, Veerle, and Kathy Steppe. 2010. “Development and Verification of a Water and Sugar Transport Model Using Measured Stem Diameter Variations.” JOURNAL OF EXPERIMENTAL BOTANY 61 (8): 2083–2099. doi:10.1093/jxb/erq018.
Vancouver
1.
De Schepper V, Steppe K. Development and verification of a water and sugar transport model using measured stem diameter variations. JOURNAL OF EXPERIMENTAL BOTANY. 2010;61(8):2083–99.
IEEE
[1]
V. De Schepper and K. Steppe, “Development and verification of a water and sugar transport model using measured stem diameter variations,” JOURNAL OF EXPERIMENTAL BOTANY, vol. 61, no. 8, pp. 2083–2099, 2010.
@article{843358,
  abstract     = {{In trees, water and sugars are transported by xylem and phloem conduits which are hydraulically linked. A simultaneous study of both flows is interesting, since they concurrently influence important processes such as stomatal regulation and growth. A few mathematical models have already been developed to investigate the influence of both hydraulically coupled flows. However, none of these models were so far tested using real measured field data. In the present study, a comprehensive whole tree model is developed that enables simulation of the stem diameter variations driven by both the water and the sugar transport. Stem diameter variations are calculated as volume changes of both the xylem and the phloem tissue. These volume changes are dependent on: (i) water transport according to the cohesion-tension theory, (ii) sugar transport according to the Münch hypothesis, (iii) loading and unloading of sugars and (iv) irreversible turgor-driven growth. The model considers three main compartments (crown, stem and roots) and is verified by comparison with actual measured stem diameter variations and xylem sap flow rates. These measurements were performed on a young oak (Quercus robur L.) tree in controlled conditions and on an adult beech (Fagus sylvatica L.) tree in a natural forest. A good agreement was found between simulated and measured data. Hence, the model seemed to be a realistic representation of the processes observed in reality. Furthermore, the model is able to simulate several physiological variables which are relatively difficult to measure: phloem turgor, phloem osmotic pressure and the Münch’s counter flow. Simulation of these variables revealed daily dynamics in their behaviour which were mainly induced by transpiration. Some of these dynamics are experimentally confirmed in literature, while others are not.}},
  author       = {{De Schepper, Veerle and Steppe, Kathy}},
  issn         = {{0022-0957}},
  journal      = {{JOURNAL OF EXPERIMENTAL BOTANY}},
  keywords     = {{TREE STEMS,PHLOEM,WOODY-PLANTS,TURGOR PRESSURE,MUNCH HYPOTHESIS,RICINUS-COMMUNIS,FLOW CHARACTERISTICS,GROWTH,SAP,XYLEM,Diurnal cycles,Fagus sylvatica L,growth,modelling,Munch hypothesis,phloem translocation,Quercus robur L,sap flow,stem diameter variations,xylem}},
  language     = {{eng}},
  number       = {{8}},
  pages        = {{2083--2099}},
  title        = {{Development and verification of a water and sugar transport model using measured stem diameter variations}},
  url          = {{http://doi.org/10.1093/jxb/erq018}},
  volume       = {{61}},
  year         = {{2010}},
}

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