Plant Photobiology

Accurate Measurement of Light is PAR for the Course!

ILT offers a full line of light measurement systems designed to test, quantify and monitor both natural and artificial light sources used in plant growth, photobiology, photomedicine, and UV photobiology studies.

ILT systems cover the full range of optical radiation (UVB, UVA, VIS,& NIR-Far Red) spectrum for measurement of PAR, PPF, PPFD, and RQE with direct readout in µmol/m2/sec (pronounced micro moles per square meter per second). ILT Spectrometers are available to provide complete spectral analysis from UV-NIR in µmol/m2/sec/nm, as well as transmission and reflectance.

Please SCROLL DOWN to review our selection of light meter systems for use in plant photobiology.

The interaction of light and plant growth (photobiology) is a complex science involving various pigments within the plant such as chlorophyll, carotenes and xanthophylls that transmit, reflect or absorb energy from certain wavelengths that are then used to maximize the photosynthesis process.

PPD, PPFD, PAR, Plant Growth



However, photosynthesis is not the only consideration when producing a plant for profit. Other aspects like shape, biomass, flowering, coloration, taste, smell, root development and medicinal benefits, etc. are often equally important.

It is well known that there is great variation in light spectrum and intensity requirements among species and desired affects (stem growth, seed germination,leaf growth, fruit bearing, flowering, etc).

Photoreceptors for photosynthesis are most efficient in the blue (400-500 nm) and red (600-700 nm) area of the spectrum. Far-red, (700–800 nm) is critical for flowering of many plants. The (500–600 nm) green area is less understood and even though much of this range is reflected, it is considered beneficial for carotenoids and lycopene (for color and photo-protection).

UV (UVB 280-315 nm and UVA 315-400 nm) radiation is important in inducing production of phenolics, anthocyanins (coloration), antioxidants and vitamins that inhibit mold growth.

Thus the full spectrum from about 350–780 nm at a suitable light intensity can be considered beneficial in plant cultivation. A proper ratio between red and blue light complemented with the correct proportions of far-red and green light and small doses of UV are most often the best mix. The key is to understand and supply the correct spectrum and intensity during the appropriate stage of growth that is optimally suited for the task at hand.


We offer a wide range of products designed for monitoring, measuring, quantifying and studying the affects of light on plants.

International Light Technologies provides a complete range of plant growth radiometers designed through the joint efforts of International Light Technologies and a team of plant physiologists to specifically measure the effect of light on plant growth in the PAR region of the spectrum.

ILT also offers customized Spectrometers and Photosynthetic Photon Flux Density (PPF) sensors to provide a more accurate weighting to match the exact spectrum required for the species or task under test.

Please contact our technical sales staff for a quote on a customized system or see the list of our most commonly sold products below:


Application Common Sources Spectral Range ILT System Options
Click Links Below
Measurement Range Units
PLANT GROWTH (PAR, PPFD, RQE) Sun, Solar Simulators, Plant Growth Lamps, Pink Houses, Green Houses, LED Lights 350-780 nm ILT950 SPECTRORADIOMETER Customized spectrum µmol/m²/sec/nm
    350-780 nm ILT550V SPECTRORADIOMETER Customized spectrum µmol/m²/sec/nm
    410-770 nm ILT5000, SED033/PAR/W 2e-6 to 1e+3 µmol/m²/sec
    410-770 nm ILT2400, SED033/PAR/W 6e-5 to 1e+3 µmol/m²/sec
    410-770 nm ILT2400, SED033/PAR/QNDS1/W 4e-5 to 3e+4 µmol/m²/sec
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Photosynthetic Photon Flux ("PPF") Individual LEDs, Small Lamps, Focus Beam/Spot 350-780 nm ILT950 SPECTRORADIOMETER Customized spectrum µmol/sec/nm
    350-780 nm ILT550V SPECTRORADIOMETER Customized spectrum µmol/sec/nm
    410-770 nm ILT5000, SED033/PAR/INS125 1e-9 to 5e-1 µmol/sec
    410-770 nm ILT2400, SED033/PAR/INS125 1e-9 to 5e-1 µmol/sec
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Blue Spectrum Sun, Solar Simulators, Plant Growth Lamps, Pink Houses, Green Houses, LED Lights 370-515 nm ILT5000, SED033/TBLU/W 1.4e-10 to 2.86e-1 W/cm²
Red Spectrum   610-730 nm ILT5000, SED033/TRED/W 5.9e-11 to 1.18e-1 W/cm²
Far Red Spectrum   710-810 nm ILT5000, SED033/TFRD/W 7.7e-11 to 1.5e-1 W/cm²
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* All Radiometers/Photometers/Spectroradiometers are NIST Traceable.
* If units of measure are not shown please contact us (empirical units also available i.e. fc, fL, nits, lm/ft²).


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