Hence, we developed a model that enables simulation of stemdiameter variations driven by the water and the carbohydrate flow.Stem diameter variations are calculated as volume changes of boththe xylem and the phloem tissue. These volume changes depend on:(i) the water transport according to the cohesion–tension theory, (ii)the transport of carbohydrates according to the Münch hypothesis,(iii) loading and unloading of carbohydrates and (iv) irreversibleturgor-driven growth. The model tree is subdivided in threecompartments: crown, stem and roots. To validate the model, weconducted double girdling experiments on young oak (Quercus roburL.) trees in growth rooms. During these experiments, data wascollected of stem diameter variations, photosynthesis and xylem sapflow for both manipulated and non-manipulated trees. In addition tothese plant variables, the micro-climate was also monitored. A goodagreement was found between simulated andmeasured data. Hence,the model is a realistic representation of the processes observed inreality.

Email Address for correspondence: Veerle.DeSchepper@UGent.be

doi:10.1016/j.cbpa.2009.04.548

P6.1110:30 Monday 29th June 2009Sharing efforts for modelling plant systems: from publications toreusable software components

Christian Fournier (INRA), Christophe Pradal (CIRAD), Michael Chelle(INRA), Frédéric Boudon (CIRAD), Gaëtan Louarn (INRA), CorinneRobert (INRA), Didier Combes (INRA), Thomas Cokelaer (CIRAD),Jessica Bertheloot (INRA), Kai Ma (INRA), Sébastien Saint-Jean (INRA),Alban Verdenal (INRA), Abraham Escobar-Gutièrrez (INRA), BrunoAndrieu (INRA), Christophe Godin (CIRAD)

Plant models become increasingly complex and their implemen-tation often implies the use of advanced techniques in computerscience. This evolution has been accompanied by the production ofdedicated plant modelling tools, such as simulation platforms, thatfacilitate research in this field. However, much less sharing isobserved for plant models themselves, that is for computer programsproduced by scientists to address their specific questions. Yet, theseprograms could be highly valuable for other researchers, to avoidredundant development of similar code or to help non-specialists tosimulate parts of a complex system. Model descriptions found inacademic publications, even combined with code sources, aregenerally not sufficient for model reuse. Most difficulties come fromthe heterogeneity of language used, the structure of the programs,the download and installation procedures, the accessibility to thesource code of the model, and the availability of documentation. TheOpenAlea initiative (http://openalea.gforge.inria.fr) has beenlaunched to address these problems by providing plant modellerswith collaborative tools and guidelines to increase software quality,hence re-usability of their models. The Alinea pilot project furthertested these concepts in a sample community of ecophysiologists andbiophysicists. Based on this experience, we illustrate pros and cons ofthe approach and discuss future direction of progress. We foreseethree steps towards a better re-usability of models: a betterinteroperability of existing tools and simulation platforms, theemergence of design patterns for plant modelling, and the definitionof standardised data structures.

Email Address for correspondence: Christian.Fournier@supagro.inra.fr

doi:10.1016/j.cbpa.2009.04.549

P6.1211:10 Monday 29th June 2009Designing the sorghum crop model in APSIM to simulate thephysiology and genetics of complex adaptive traits

Graeme L. Hammer (The University of Queensland), Erik Van Oosterom(TheUniversity of Queensland), GregMcLean (QueenslandDepartment ofPrimary Industries and Fisheries), Scott Chapman (CSIRO Plant Industry)

Progress in crop improvement generally and inmolecular approachesto plant breeding particularly are limited by our ability to predict plantphenotype based on its genotype, especially for complex adaptive traits.However, the capacity of crop growth and developmentmodels to bridgethis predictability gap is questionable if the models rely on algorithmsthat describe key aspects of crop growth and development too simply, orif theydelve too far into detailedprocess specification requiringextensiveand sophisticatedparameterisation.Hereweoutline a generic cereal cropgrowth and development model designed to retain good predictive skillat crop level while also introducing sufficient physiological rigour thatcomplex phenotypic responses become emergent properties of themodel dynamics, thus facilitating effective gene-to-phenotype links. Thegeneric template has been constructed in the APSIM software platform,which facilitates on-going and collaborative development. We detailexperimentsunderpinningdevelopmentandtestingof the sorghumcropmodel implemented in this template. The approach is focussed aroundquantifying capture and use of radiation,water, and nitrogen.Wepresentan example of how introducing genetic variation in plant height cangenerate emergent simulated phenotypic differences in green leaf arearetention associated with nitrogen dynamics. The relevance of thiscapability for complex trait dissection and plant breeding is discussed.

Email Address for correspondence: g.hammer@uq.edu.au

doi:10.1016/j.cbpa.2009.04.550

P6.1311:50 Monday 29th June 2009Scaling root growth responses from seedlings to field

A.G. Bengough (Scottish Crop Research Institute), Tracy A. Valentine(Scottish Crop Research Institute), Ian J. Bingham (SAC), Blair M.McKenzie (Scottish Crop Research Institute)

Good root system development is essential for optimum plantgrowth, especially in soils where water and nutrients are limiting.Climate change offers the likelihood of increased rainfall variabilityresulting in soils that are either toowet or too dry for good root growth.Soil physical limitations to root growth may decrease seedling rootextension rates to 40% or less of their unimpeded rate if soil strengthexceeds 2 MPa penetrometer resistance, air-filled porosity is less than0.10, or if matric potential approaches −1.5 MPa. Our field and labmeasurements in sandy–loam soil indicate that such physically limitingconditions occur for much of the growing season, and vary greatly withdepth, time, and soil cultivation. We have evidence that physicallylimiting conditions, particularly soil strength, are often present in arablesoils throughout Eastern Scotland. In the light of these results, we willdiscuss some major uncertainties underlying our ability to predict rootgrowth in the field: namely the relation between seedling root growthand the growth of older plants, and the plasticity of root systems inresponding to heterogeneous soil environments.

Email Address for correspondence: Glyn.Bengough@scri.ac.uk

doi:10.1016/j.cbpa.2009.04.551

Abstracts / Comparative Biochemistry and Physiology, Part A 153 (2009) S219–S229S222