Importance of a realistic leaf shape in light modelling

Functional-structural plant models (FSPMs) are useful in scientific research to capture the dynamic interactions between a plant's architecture and its environment. In tomato (Solanum lycopersicum L.), this research has focused on light modelling and light distribution in the canopy as the use of assimilation light in greenhouses is gaining importance in northern climates. In previous research, the complex shape of tomato leaflets has been simplified to geometric shapes such as rectangles and rhombuses. The extent to which these simplifications alter light simulations have, however, never been investigated. Modelled realistic leaflet shapes were compared with simplified leaflets in terms of light absorption and photosynthesis. Geometrical parameters used within the simplified shapes were also altered and compared. It was concluded that canopies with longer leaflets, but identical leaflet area, absorbed more light and had higher photosynthetic rates. At the whole-plant level these differences were small but significantly altered the absorption gradient. This led to substantial differences, most notably in the highest leaves in the canopy, which, in turn, affected canopy photosynthetic potential. It was therefore concluded that leaf shape simplifications in tomato FSPMs should be warily considered, as they can alter the results of the optimization goal these models are designed for.