A novel approach to verification and validation of functional–structural plant models

Functional-structural plant modelling is an established approach to realistically represent plant growth, but testing and documenting realism beyond visual comparisons is challenging. We used elements of pattern-oriented modelling to test the realism of a new model of the annual growth module (AGM) of avocado (Persea americana, cv. Hass. Lauraceae).

Two-dimensional representation of an annual growth module (AGM), that forms from an indeterminate compound inflorescence over an annual growing period, comprising one mixed reproductive and vegetative growth flush (spring, dark brown) and two vegetative growth flushes (summer, brown, and autumn, light brown).
Two-dimensional representation of an annual growth module (AGM), that forms from an indeterminate compound inflorescence over an annual growing period, comprising one mixed reproductive and vegetative growth flush (spring, dark brown) and two vegetative growth flushes (summer, brown, and autumn, light brown). The AGM contains a primary growth axis, and second- and third-order growth axes that can be either proleptic shoots (shown with a bud-scar ring at their base) or sylleptic shoots. The current season’s shoot growth develops from a terminal bud from the previous season, with the shoot initially producing lateral inflorescences without internode extension. Vegetative growth then occurs in three flushes with the formation of a terminal bud between each flush. The remains of the terminal buds turn into a bud-scar ring which becomes visible between each flush later in the season. Growth unit (GU) refers to the portion of an axis (shoot) that develops during an uninterrupted period of extension, i.e. during a single flush, while a shoot describes an axis that consists of one or more GUs (Jaeger and De Reffye, 1992; Room et al., 1994). This figure is a modification of a free vector image from all-free-download.com.

Wang et al. use seven patterns characterising AGMs to calibrate the model, which then successfully predicted nine further patterns that were not used during calibration. Their model can thus be claimed to be structurally realistic, which implies that it will be able to predict the response of an AGM to changing environmental conditions.

This paper is part of the Annals of Botany Special Issue on Functional-Structural Plant Growth Modelling. It will be free access until June 2018, then available only to subscribers until April 2019 when it will be free access again.

Reference List

Wang, M., White, N., Grimm, V., Hofman, H., Doley, D., Thorp, G., … Hanan, J. (2018). Pattern-oriented modelling as a novel way to verify and validate functional–structural plant models: a demonstration with the annual growth module of avocado. Annals of Botany, 121(5), 941–959. https://doi.org/10.1093/aob/mcx187