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absorption spectrum, Chandra, chlorophyll a, chlorophyll b, CO2, grow light, horticulture, light absorption, PAR, photosynthesis, PPFD, zenith LED grow lights -

Words and images by Richard Jones. How 'high' must Photosynthetic Photon Flux Density (PPFD, µmol/m2/s) be to induce peak photosynthesis in Cannabis? In 2008, Chandra measured a maximum rate of photosynthesis at 1,500 µmol/m2/s. In 2015, Chandra conducted a similar assessment and measured a maximum rate of photosynthesis at 2,000 µmol/m2/s. So, problem solved... right? Not necessarily. Chandra, 2008. Chandra's 2008 Cannabis analysis is a two part study. First, he measured the photosynthetic response to a range of light intensities at various temperatures. The light and temperature combination that produced peak photosynthesis was then applied to a series designed to...

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absorption spectrum, chlorophyll a, chlorophyll b, grow light, horticulture, light absorption, PAR, photosynthesis, PPFD, zenith LED grow lights -

Words and images by Richard Jones. Part 3, PPFD Photosynthetic Photon Flux (PPF) is the total amount of Photosynthetically Active Radiation (PAR) emitted by a light. Measured in micromoles per second (µmol/s), PPF provides a general understanding of a light's full output, but it does not measure the photons that actually reach your specimen. To rationalize the true utility of natural and artificial light, the Horticulture Industry relies on a narrow interpretation of photon delivery by gauging Photosynthetic Photon Flux Density (PPFD). Expressed as micromoles, per square meter, per second (µmol/m2/s), PPFD is an evenly weighted measurement of PAR that...

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absorption spectrum, chlorophyll a, chlorophyll b, grow light, horticulture, light absorption, lumens, PAR, photosynthesis, zenith LED grow lights -

Words and images by Richard Jones. Part 2, Lumens Lumens is a measurement of total light emitted by a source, but it's only a narrow representation of the PAR spectrum. As defined by the LI-COR LI-210R Photometric Sensor, the spectral response is a weighted measure designed to rationalize light associated with peak human sensitivity (555nm). This is ideal for testing household, office and public lighting, but it's a limited gauge for assessing the intensity and effectiveness of horticulture lights. Consumer Interpretation of Lumens Although lumens primarily measure the intensity of Green and Yellow light, it's possible to glean a couple...

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absorption spectrum, chlorophyll a, chlorophyll b, grow light, horticulture, light absorption, PAR, photosynthesis, zenith LED grow lights -

Words and images by Richard Jones. Part 1, PAR Photosynthesis is the photochemical process by which plants and other organisms use light to synthesize sugars from carbon dioxide and water. The spectral range of light that induces photosynthesis is called Photosynthetically Active Radiation (PAR). PAR is defined as visible light that is measured from 400 to 700 nanometers (nm) and includes Violet, Blue, Green, Yellow, Orange and Red. Of these colors, Violet to Blue (400 to 500nm) is associated with vegetating growth and Orange to Red (600 to 700nm) is associated with flowering growth. Although many plant pigments are not...

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