Development of a dynamic 3D growth model for lettuce.

MSc-thesis abstract (submitted 2 April 2015):
With the rise of vertical farming systems the possibilities of spacing and lighting strategies for crop growth have increased tremendously. Both one dimensional (1D) and three dimensional (3D) models can be used to explore the possibilities and best strategies for vertical farming systems.

3D functional-structural plant models (FSPMs) have the advantage of moving objects in a 3D environment and therefore are more suited to evaluate spacing and lighting strategies. In FSPMs plant structures are simulated in a three dimensional (3D) environment based on physiological processes at the organ level. A 3D simulation of the plant architecture and lighting allows the exploration of different lighting and spacing strategies and the effects of plant architecture on light absorption and photosynthesis, which was hardly possible until the introduction of FSPMs.  

The aim of this research was the development of a dynamic lettuce FSPM which could simulate a growing lettuce plant under non-competitive conditions. The focus was on assimilate distribution towards organs and the use of received assimilates for organ growth. An existing dynamic source-sink FSPM, created on the GroIMP platform by Jochem Evers, was used as starting point to develop the dynamic lettuce FSPM. Development of the model was based on data obtained through an experiment during this research.

The existing dynamic source-sink FSPM has been adapted to a functioning dynamic lettuce FSPM. Calibration of essential variables has been performed; the plastochron, phyllotaxis, length/width ratio, leaf shape, leaf weight and growth period and the leaf mass area. Other variables not measured during the experiment, e.g. shoot/root mass ratio and growth/maintenance respiration, were set at values obtained from literature. Changes in code regarding the graphical 3D representation of the plant structure were based on pictures made during the experiment. Particularly the leaves were of interest during this study and received most attention.

The current light model does not allow for different wavelengths and the use of LEDs. The first priority for further development is to incorporate a new light model into the current dynamic lettuce FSPM which can make use of different wavelengths and allows the use of LEDs. Once the LEDs are incorporated an elaborated model validation can be performed. The model application can be widened by implementing options to rearrange plants during growth and by studying and implementing growth changes related to different light quality and directions. In this way the model can be used to assess different spacing and lighting options.

Student: Maarten Verhoog

Supervisor(s): Prof. dr ir L.F.M. Marcelis