How Important Is Leaf Realism in Functional-Structural Plant Modelling?

Making a realistic plant in a computer model is possible, but is it necessary. All the computations generating the plant slow down the speed of any simulation. As a result it’s common to use simple geometric shapes for the leaves. But do you lose accuracy in the results, when you lose accuracy in the leaves? Jonathan Vermeiren and colleagues have been examining models of tomato, Solanum lycopersicum, to quantify the errors you get with simplifying leaflet shapes.

“In this study, a static FSPM [Functional-Structural Plant Model] for tomato is constructed to evaluate deviations in simulated light conditions and photosynthesis as a result of leaf shape simplifications used in previous research,” write the authors.“Tomato plants were grown under a commercial glasshouse set-up with assimilation lighting, where the 3-D plant structure, assimilation light conditions and glasshouse were characterized and reconstructed in a virtual FSPM. Realistic leaflet shapes of tomato plants were reconstructed using scanned images of leaflets that were converted to triangulation points, which can be easily used by 3-D simulation software. Using such an FSPM, we investigated to what extent simplified leaflet shapes alter light absorption and gross photosynthesis in a tomato canopy and how these results can be translated to other crops.”

The differences mattered in some simulations, but not others. “Our results showed that a simplification of the leaflet shape in a tomato crop can lead to small, but significant, deviations in simulations of light absorption and gross photosynthesis. At the canopy level, this effect was shown to be mitigated somewhat by the canopy closure in dense canopies, such as that used in the glasshouse simulation, as overall less light escapes the canopy. At the individual leaf level, however, these differences persisted for both the individual plant and the glasshouse scenario, which can only be attributed to the geometrical properties of the shapes, as leaflet area was kept constant across different shapes.”

Vermeiren and colleagues say that the bulk of the increased workload is in setting up the simulation rather than running it. “The main workload for re-creating realistic shapes is a one-time investment to create a shape database and automated scripts for shape extraction and reconstruction. Additionally, the cost in simulation time is only marginally increased.” They argue that the small deviations they see in static FPSMs could lead to greater differences in dynamic FPSMs.”