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Horticultural and Agricultural Lighting

Plant Growth Lights

Photosynthesis is a process, where plants convert light energy into chemical energy. The way the plants use the different wavelengths of the light differs from the human perception. Thus the light for plants needs to be measured using different metrics.

PAR is acronym for Photosynthetically Active Radiation.  It is the power of the light within the wavelength range from 400 nm to 700 nm, which is the wavelength range that the plants can harness energy from. The unit for PAR is W. 

PPF is Photosynthetic Photon Flux. It is the amount of PAR light photons alight source produces. The unit for PPF is micrommoles per second or μmol·s-1. This is an important measurement to look for when comparing horticultural light fixtures. PPF tells you how much light your fixture will produce that your plants can use for photosynthesis.

PPFD is Photosynthetic Photon Flux Density. It is the amount of PAR light that lands on a square meter each second. PPFD is measured in micromoles per square meter per second (μmol·m-2·s-1). In other words, PPFD is how much PPF is hitting each square meter of your crop at any given second. It is important to look at PPFD when planning your grow light installation. Adjusting your fixtures' height and density will affect the PPFD at your crop canopy.

DLI is Daily Light Integral. It is the amount of PAR that lands on a square meter surface over a 24-hour period. DLI is measured in moles of light per square meter per day (mol·m-2·d-1). You can think of this as the accumulation of PPFD over a full day. In human terms, you can think of DLI as a plant's daily caloric intake of light. 



phytochrome Pr, phytochrome Pfr far red

chlorophyll a/b


Red / Far Red suhde

Blue Green suhde

umol/J tehokkuus

SSL ratkaisuja: SPEKTRI 80, goniot, PPFD simulator