Plant physiological changes and leaf reflectivity

MSc Thesis Project

Project start                January 2026

Company supervisor   Romy Steenkamer

In high-tech greenhouses, the amount of available sunlight is an important factor governing cultivation strategies. Supplementary lighting (via LED lamps) is an effective way to artificially reach required light levels but it is also an important expense item. Therefore, growers have an interest in obtaining accurate information on the lighting conditions inside the greenhouse.

A common way to measure light is by using PAR (Photosynthetically Active Radiation) sensors, which accurately measure light intensity in a spot. However, as the greenhouse interior is not a uniform environment, it is not sufficient to measure PAR in a single spot: a map of light intensity throughout the greenhouse allows more efficient light management.

Project

FOTONIQ has been developing a camera-based method to calculate PAR inside operational greenhouses. As the model works based on the light that is reflected by the plants’ leaves, a way to improve it would be to incorporate information on the plants’ morphology and physiological status, for example considering the chlorophyll content of the leaves or their spatial information. This would give the model more accurate information on the physical parameters needed to calculate PAR (e.g. leaf reflectivity at different wavelengths).

However, leaf reflectivity is not a constant as plant changes its physiological status in different grow cycles and/or environmental conditions. Understanding more about how the plants develop specific leaf conditions can be crucial to improve the accuracy of the model.

Methods

The research questions will be answered by means of extensive literature research. Theories, insights and hypotheses will be discussed.

Research Questions

• What are the determinants of leaf reflectance?
• How do plants adjust their light intercepting mechanism in response to different environmental conditions?
• In what ways does leaf reflectance change during different growth stages?
• How does leaf reflectance affect photosynthesis rate and light use efficiency?

Sounds interesting?