P.A.R. (Fotosynthetic Active Radiation)
What is Photosynthetically Active Radiation (PAR)?
Plants and humans perceive light very differently. Humans primarily focus on the middle of the spectrum. You’ve probably heard of the term “lumen,” which is based on the model of the human eye and how light is perceived by it. The curve shows that humans are much more sensitive to green light than to blue or red light. Plants, however, perceive light in a completely different way. They are more sensitive to blue and red light to stimulate photosynthesis. PAR stands for photosynthetically active radiation and spans from blue (400nm) to red (700nm). PAR essentially indicates the type of light needed to carry out photosynthesis. The amount and spectral quality of PAR light are important factors to consider when designing your lighting solution.
How do I measure PAR?
PAR refers to the range of 400-700nm. The unit measured within PAR is photons, expressed in micromoles per second (μMol/s). Measuring the number of photons within the PAR range is possible with a quantum sensor and can, in combination with a light meter, measure the direct light intensity on the crop. It is also possible to measure the cumulative light intensity using a data logger. This way, you have a record of the entire day. We call this DLI.
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