What is the percentage of photosynthetically active radiation

In the broad sense, photosynthetically active radiation (PAR) is the part of electromagnetic radiation that can be used as the source of energy for photosynthesis by green plants. Technically, it is defined as radiation in the spectral range from 400 to 700 nm [ −2 s −1), since photosynthesis is a quantum process, or in terms of photosynthetic radiant flux density (PAR irradiance, W m −2), more suitable for energy balance studies. A fundamental term in the quantification of light used by plants in the photosynthesis process is the fraction of absorbed photosynthetically active radiation (fAPAR) calculated as the ratio of absorbed to total incident PAR in a vegetation canopy. This variable is widely used in vegetation functioning models at a range of spatial scales from the plant to the globe as an indicator of the amount of energy... Photosynthetically active radiation (PAR): The part of electromagnetic radiation that can be used as the source of energy for photosynthesis by green plants, measured as PAR irradiance or PPFD. PAR waveband: Spectral region for electromagnetic radiation defined by the wavelength limits of 400–700 nm. PAR irradiance: Radiant flux density, or the radiative energy received by unit surface area in unit time, carried by photons in the PAR waveband. Photosynthetic photon flux density (PPFD): The number of photons with wavelengths in the PAR waveband passing through unit surface area in unit time; synonymous to PAR quantum flux. Photosynthetic action...

UPDATE: Fondriest Environmental is offering their expertise in photosynthetically active radiation through their new online knowledge base. For an updated and comprehensive look at PAR and its importance to environmental and water quality, check out: Photosynthetically Active Radiation. Photosynthetically Active Radiation (PAR) is the amount of light available for photosynthesis, which is light in the 400 to 700 nanometer wavelength range. PAR changes seasonally and varies depending on the latitude and time of day. Levels are greatest during the summer at mid-day. Factors that reduce the amount of PAR available to plants include anything that reduces sunlight, such as cloud cover, shading by trees, and buildings. Air pollution also affects PAR by filtering out the amount of sunlight that can reach plants. Why is Photosynthetically Active Radiation Important? Photosynthetically Active Radiation is needed for photosynthesis and plant growth. Higher PAR promotes plant growth, and monitoring monitoring PAR is important to ensure plants are receiving adequate light for this process. PAR values range from 0 to 3,000 millimoles per square meter. At night, PAR is zero. During mid-day in the summer, PAR often reaches 2,000 to 3,000 millimoles per square meter. How is Photosynthetically Active Radiation measured? Photosynthetically Active Radiation (PAR) is reported as millimoles of light energy per square meter. Photosynthetically Active Radiation Technology Photosynthetically Acti...