Root Typ: a generic model to depict and analyse the root system architecture (original) (raw)
Related papers
Links between root length density profiles and models of the root system architecture
Vadose Zone Journal, 2012
A lot of data is available in the literature on root length density profi les (i.e., root length per unit of soil volume versus soil depth), because they are a tradi onal way of represen ng root distribu on in the fi eld. In a complementary approach comprehensive models of the root system architecture are being developed, but the parameters required for these models are o en diffi cult to assess in fi eld condi ons. In this paper, we bridge both approaches, empirical and comprehensive, by evalua ng the capability of architectural models to simulate the observed diversity in root length distribu on on the one hand and the possibility of es ma ng developmental parameters from root length density profi les on the other. For this purpose, we constructed a simple model with only six parameters, to represent the root system architecture. It reproduced a large diversity of root profi les comparable to observa ons reported in the literature and encompassing many diff erent crops. The impact of each model parameter, as well as their interac ons, on the shape of the profi les was quan fi ed using a global sensi vity analysis. Finally, a sta s cal metamodel was designed and es mated to simulate the same collec on of profi les without intermediate simula ng the whole architecture. The meta-model allows for es ma on of architectural parameters from profi le shapes (inversion). Some architectural parameters could be es mated from the profi les with good accuracy, especially those quan fying the growth poten al and gravitropism of individual roots, because of their specifi c impact on root length at a specifi c depth. But others (like inter-branch distance, life dura on), which modify root density in a more diff use way throughout the profi le, could not be iden fi ed correctly using this method. Addi onal data involving specifi c measurements are necessary to iden fy these last parameters. Abbrevia ons: GSA, global sensi vity analysis; IBD, inter-branch distance; IG, intensity of gravitropism; LD, life dura on versus diameter; MRDB, maximal rela ve diameter of branch root. Root length density profi les, that is, root length per unit of soil volume versus soil depth, are a long-standing approach for representing root distribution in the soil (Böhm, 1979), and are still commonly used (Liu et al., 2011). One reason is that root profi les inherit the usual mono-dimensional representation of the soil in terms of horizontal layers, because the soil (as well as the root system) exhibits strong vertical variations. Root profi les also stem from root observation methods, especially soil coring methods with augers, which give a direct mono-dimensional map of roots. Moreover, numerous water and nutrient uptake models use a mono-dimensional representation of root length density as the input.
2010
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Root growth models: towards a new generation of continuous approaches
Journal of Experimental Botany, 2010
Models of root system growth emerged in the early 1970s, and were based on mathematical representations of root length distribution in soil. The last decade has seen the development of more complex architectural models and the use of computer-intensive approaches to study developmental and environmental processes in greater detail. There is a pressing need for predictive technologies that can integrate root system knowledge, scaling from molecular to ensembles of plants. This paper makes the case for more widespread use of simpler models of root systems based on continuous descriptions of their structure. A new theoretical framework is presented that describes the dynamics of root density distributions as a function of individual root developmental parameters such as rates of lateral root initiation, elongation, mortality, and gravitropsm. The simulations resulting from such equations can be performed most efficiently in discretized domains that deform as a result of growth, and that can be used to model the growth of many interacting root systems. The modelling principles described help to bridge the gap between continuum and architectural approaches, and enhance our understanding of the spatial development of root systems. Our simulations suggest that root systems develop in travelling wave patterns of meristems, revealing order in otherwise spatially complex and heterogeneous systems. Such knowledge should assist physiologists and geneticists to appreciate how meristem dynamics contribute to the pattern of growth and functioning of root systems in the field.
Annals of Botany
Background and Aims Many studies exist in the literature dealing with mathematical representations of root systems, categorized, for example, as pure structure description, partial derivative equations or functional-structural plant models. However, in these studies, root architecture modelling has seldom been carried out at the organ level with the inclusion of environmental influences that can be integrated into a whole plant characterization. • Methods We have conducted a multidisciplinary study on root systems including field observations, architectural analysis, and formal and mathematical modelling. This integrative and coherent approach leads to a generic model (DigR) and its software simulator. Architecture analysis applied to root systems helps at root type classification and architectural unit design for each species. Roots belonging to a particular type share dynamic and morphological characteristics which consist of topological and geometric features. The DigR simulator is integrated into the Xplo environment, with a user interface to input parameter values and make output ready for dynamic 3-D visualization, statistical analysis and saving to standard formats. DigR is simulated in a quasi-parallel computing algorithm and may be used either as a standalone tool or integrated into other simulation platforms. The software is open-source and free to download at http://amapstudio.cirad.fr/soft/xplo/download. • Key Results DigR is based on three key points: (1) a root-system architectural analysis, (2) root type classification and modelling and (3) a restricted set of 23 root type parameters with flexible values indexed in terms of root position. Genericity and botanical accuracy of the model is demonstrated for growth, branching, mortality and reiteration processes, and for different root architectures. Plugin examples demonstrate the model's versatility at simulating plastic responses to environmental constraints. Outputs of the model include diverse root system structures such as tap-root, fasciculate, tuberous, nodulated and clustered root systems. • Conclusions DigR is based on plant architecture analysis which leads to specific root type classification and organization that are directly linked to field measurements. The open source simulator of the model has been included within a friendly user environment. DigR accuracy and versatility are demonstrated for growth simulations of complex root systems for both annual and perennial plants.
A minimal continuous model for simulating growth and development of plant root systems
Plant and Soil, 2011
Aims: This paper proposes a general and minimal continuous model of root growth that aggregates architectural and developmental information and that can be used at different spatial scales. Methods: The model is described by advection, diffusion and reaction operators, which are related to growth processes such as primary growth, branching, mortality and root death. Output variable is the number of root tips per unit volume of soil. Operator splitting techniques are used to fit, solve and analyze the model with regards to ontogeny. The modeling approach is illustrated on a 2D case study concerning a part of Eucalyptus root system. Results: Operator splitting is helpful to fit the model. Basic knowledge on root architecture and development allows decreasing the number of unknown parameters and defining ontogenic phases on which specific calibrations must be carried out. Simulation results reproduce quantitatively the dynamic evolution of root density distribution with a good accuracy.
The algorithmic beauty of plant roots – an L-System model for dynamic root growth simulation
Mathematical and Computer Modelling of Dynamical Systems, 2010
Understanding the impact of root architecture on plant resource efficiency is important, in particular, in the light of upcoming shortages of mineral fertilizers and changed environmental conditions. In the 1950s, a great number of root systems of European cultivated plants were excavated and studied by L. Kutschera (1960). Her work gave enormous insight into the variety of root system architectures and helped to realize the importance of belowground processes to plant productivity. We analysed the resulting hand drawings by using mathematical modelling and found root system parameters for a newly developed parametric L-System model. In this way we were able to first reproduce the illustrations, second computationally analyse root system traits and finally access the dynamic root architecture development.