IMapple: A Functional-Structural Growth and Fruiting Simulation Model of 'Golden Delicious' Apple Trees

Functional-structural modeling is a useful approach to explore the integration of factors that influence growth and development. Such models may allow us to test hypotheses and conduct virtual experiments much more quickly and efficiently than traditional field-based approaches. Combining knowledge from fields such as plant biology, computer science, and applied mathematics is required for the development of functional-structural plant models (FSPMs). Functional- structural plant models refers to simulating the development of plant structure considering plant physiology, genetics, environmental factors and management interventions with the objective of capturing the plant structure (3D shape) and function. From a horticultural perspective, appropriate orchard design and efficient management practices can be investigated using this approach.

We have developed the IMapple (Interactive Model for Apple) by combining expertise from horticulture and computer science. Initially we have focused on developing a model that describes growth and fruiting of ‘Golden Delicious’ apple trees growing on G16 rootstock in Indiana. Inspired by the L-PEACH model, we have restated the underlying model and IMapple has been developed de novo in C# code using data from our results and from the literature. Where adequate data are lacking we have made some assumptions, which over time we hope to replace with data. Our model uses contemporary algorithms from computer graphics. We simulate various environmental factors, such as illumination and gravity. A simulation of one year tree development with the time step of one hour can be executed within a couple of minutes on a desk top computer. The model is representative of real tree growth and development, and will likely be useful as a tool for researchers, instructors, students and growers.