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Re: [APD] Optimum Photosynthetically Active Radiation Values for Aquatic Plants ? and relation to uW/nm/lm ?

PAR involves the what portions of the spectrum are emitted by a lamp. mesurements like lumens or lux won't differentiate so long as the emissions are within the spectrum visible to humans.

Theoretically you could derive PAR for a given bulb if you had a measured graph of spectral output and lumen measurements. But you will be hard pressed to find the former for most bulbs.

The way to get usable PAR measurements would be to measure with a PAR meter at numerous locations within the aquarium and under the bulb. Measuring directly below the bulb won't give a good indication of the actual useful output because such a measurement doesn't take dispersion into account.

However, any white light will serve well since white light comprises the full range of visible light (or a balance or red, green, and blue spikes), which, it happens, includes the PAR regions. And in particular, triphospor fluourescents and white metal halides work very well.

sh




----- Original Message ----
From: Sujoy Banerjee <joyban70 at yahoo_com>
To: aquatic-plants at actwin_com
Sent: Tuesday, March 20, 2007 5:20:59 AM
Subject: [APD] Optimum Photosynthetically Active Radiation Values for Aquatic Plants ? and relation to uW/nm/lm ?


Hi 
   
  Does anybody know what is the Adequate or optimum Photosynthetically
  Active Radiation (PAR)  values that should be made available to fresh water aquatic plants for photosynthesis and is this depended on the plant concentration per unit area or plant canopy ?
   
  Also is there any method to derive the PAR values from micro watts/nm/lm ? or for that matter initial lm ? or what is the best method to calculate PAR if you have the following from the manufacturers data :-
   
  Luminous output in lumen, Luminous Efficacy in lm/W, Rated wattage in Watts
   
  Thank for all your help.
   
  Regards
   
  Sujoy
   


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