Schelt Technology

Radiation that drives photosynthesis is called photosynthetically active radiation (PAR) and, historically, is definedas total radiation across a range of 400 to 700 nm. PAR is almost universally quantified as photosynthetic photonflux density (PPFD) in units of micromoles per square meter per second (μmol m-2s-1, equal to microEinsteins persquare meter per second) summed from 400 to 700 nm (total number of photons from 400 to 700 nm). However,ultraviolet and far-red photons outside the defined PAR range of 400-700 nm can also contribute tophotosynthesis and influence plant responses (e.g., flowering).Sensors that measure PPFD are often called quantum sensors due to the quantized nature of radiation. A quantumrefers to the minimum quantity of radiation, one photon, involved in physical interactions (e.g., absorption byphotosynthetic pigments). In other words, one photon is a single quantum of radiation. Sensors that function liketraditional quantum sensors but measure a wider range of wavelengths can be thought of as an ‘extended range’quantum sensor.

Apogee Instruments PAR meters are the tool of choice for cost-effective, scientific-grade measurement of underwater PARlevels. Accurate tank PAR mapping, daily light integral measurements, and the adjusting of photosynthetic radiation levels tomimic nature are all critical to specimen health. Apogee offers three different underwater calibrated meters at three different
price points. The basic MQ-210X features our original X detector that is excellent for broadband light sources. The research-grade MQ-510 features an improved detector excellent for all light sources, including LEDs, and matches LI-COR and Kipp
& Zonen PAR sensors in accuracy while costing much less. The cutting-edge MQ-650 measures the newly confirmed far-redextended (ePAR) photosynthetic wavelengths (400-750 nm).

Mean cosine response of seven Apogee SQ-500 quantumsensors. The red data are AM measurements; the green data are PM measurements.

The ML-020P reference sensor equipment measures sunlight and calibrates outdoors at the same time asthe reference of spectroradiometer.The reference of spectroradiometer is calibrated using a standard limp traceable to NIST.

Radiation that drives photosynthesis is called photosynthetically active radiation (PAR) and, historically, is definedas total radiation across a range of 400 to 700 nm. PAR is almost universally quantified as photosynthetic photonflux density (PPFD) in units of micromoles per square meter per second (μmol m-2s-1, equal to microEinsteins persquare meter per second) summed from 400 to 700 nm (total number of photons from 400 to 700 nm). However,ultraviolet and far-red photons outside the defined PAR range of 400-700 nm can also contribute tophotosynthesis and influence plant responses (e.g., flowering).

Radiation that drives photosynthesis is called photosynthetically active radiation (PAR) and is typically defined astotal radiation across a range of 400 to 700 nm. PAR is almost universally quantified as photosynthetic photon fluxdensity (PPFD) in units of micromoles per square meter per second (μmol m-2s-1, equal to microEinsteins persquare meter per second) summed from 400 to 700 nm (total number of photons from 400 to 700 nm). However,Ultraviolet and far-red photons outside the defined PAR range of 400-700 nm can also contribute tophotosynthesis and influence plant responses (e.g., flowering).