How much light does a plant really capture?

Greenhouse companies increasingly use LED lighting. These lamps offer growers numerous advantages compared to traditional HPS lighting. This allows them to apply crop- or target-specific light recipes. But how exactly plants react to LED light is often unknown. That is why the Business Unit Greenhouse Horticulture and Flower Bulbs of Wageningen University & Research developed a line sensor that measures which wavelengths a plant absorbs and to what extent, and investigates the consequences of this.

Light affects the growth of a crop in many ways. The amount of light that the leaves receive determines photosynthesis and thus the growth of the crop. The light spectrum is responsible for the development of the plant, such as the quality and elongation of the leaves. In addition to light, radiation also contains heat, which also influences the development of the crop.

In many of these respects LED differs from sunlight and conventional lighting. Moreover, LED can be used by growers in new ways: the lamps can be switched on at any time, and have a different position in relation to the crop.

But what the effects are of these changes is not known. Which parts of the light spectrum are captured by the leaves? For example, what does a plant do with UV or far-red light? And what influence does the lack of radiant heat from the light source have? There are sensors for measuring light, but these sensors do a so-called point measurement or do not integrate over a specific spectral range.

Line sensor to be placed in and under the crop
That is why WUR developed a spectral line sensor. This can be placed in and under the crop, and thus measure during different times which wavelengths are captured and to what extent. It is then important to determine the crop reactions and to assess how the spectra affect the crop. The WUR is currently working on a follow-up to the developed prototype: it is expected to be ready in April 2022. The project 'Insight into sunlight and LED light' is financed by the Ministry of Agriculture, Nature and Food Quality in the Netherlands within the program Kas als Energiebron, in collaboration with SpectraPartners and JETI.

For more information:
Wageningen University & Research 


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