CARBON COST OF ROOT SYSTEMS - AN ARCHITECTURAL APPROACH

Root architecture is an important component of nutrient uptake and may be sensitive to carbon allocational changes brought about by rising C O2. We describe a deformable geometric model of root growth, SimRoot, for the dynamic morphological and physiological simulation of root arc hitectures. Using SimRoot, and measurements of root biomass deposition , respiration and exudation, carbon/phosphorus budgets were developed for three contrasting root architectures. Carbon allocation patterns a nd phosphorus acquisition efficiencies were estimated for Phaseolus vu lgaris seedlings with either a dichotomous, herringbone, or empiricall y determined bean root architecture. Carbon allocation to biomass, res piration, and exudation varied significantly among architectures. Root systems also varied in the relationship between C expenditure and P a cquisition, providing evidence for the importance of architecture in n utrient acquisition efficiency.