[Coral-List] RE: Coral-List Digest, Vol 31, Issue 31 What is PAR?
jasonlicamele at hotmail.com
Tue Jan 24 22:03:05 EST 2006
P.A.R. is Photosynthetically Active Radiation which unit of measurement is:
meter^2 second^2 (mol m^-2 s^-2)
It is not a percentage but a unit of displacement over time of photon
molecules.The appropriate unit for discussing photosynthesis is referred to
as Photosynthetic Photon Flux (PPF) which is measured in mol m^-2 s^2.
P.A.R. ranges between 400 - 700 nm.
Lumen is derived from illumination which is determined with the human eye
(or lux meter) and is usually referred to as lux (lx). The human eye is
capable of adjusting to light quickly and is not an accurate measure of
light (radiation of an electromagnetic wave with wavelengths in a range of
1nm to 1mm). Plant Scientists refer to PAR rather than Lux.
I assume you are using the bulbs for some type of algal / coral system.
Theoretically bulbs with the same lumen will have the same PAR. However to
be completely accurate (due to variation in manufacturing) a measurement of
PAR should be taken.
Jason D. Licamele
Environmental Research Laboratory
Soil, Water & Environmental Science
Agriculture and Biosystems Engineering
University of Arizona
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>Subject: Coral-List Digest, Vol 31, Issue 31
>Date: Tue, 24 Jan 2006 12:00:16 -0500 (EST)
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> 1. Photosynthetically Active Radiation (Jade Maggs)
>Date: Tue, 24 Jan 2006 11:57:56 +0200
>From: "Jade Maggs" <jmaggs at seaworld.org.za>
>Subject: [Coral-List] Photosynthetically Active Radiation
>To: "Coral List Server" <coral-list at coral.aoml.noaa.gov>
>Message-ID: <000a01c620cc$a6872610$c401a8c0 at AQUARIUM02>
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>Please can someone explain what P.A.R. is. I gather it is a percentage of
>lux which is photosynthetically active. For two bulbs with the same lumen
>output, can P.A.R. differ.
>uShaka Marine World
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>End of Coral-List Digest, Vol 31, Issue 31
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