From philip@GRIFFITH.DWR.CSIRO.AUWed Aug 14 12:20:36 1996 Date: Thu, 6 Jun 1996 09:44:49 +1000 From: Philip Orr To: Multiple recipients of list ALGAE-L Subject: Re: Photon flux density measurement [The following text is in the "iso-8859-1" character set] [Your display is set for the "US-ASCII" character set] [Some characters may be displayed incorrectly] In a previous message Hans Sluiman wrote:- >We need a photon flux density meter and one of the suppliers I have contacted offers two >different sensors: a Quantum sensor which has a more or less flat response between 400 and >700 nm and a PAR "Special" sensor which has a response curve that closely mimics the typical >photosynthetic action spectrum of higher plants. >Which sensor would be preferable or more accurate when measuring PAR (Photosynthetic Active >Radiation) in growth cabinets where a variety of algal (green, brown, diatoms....) cultures >are kept? Which type of sensor do experimental phycologists commonly use? >Thanks for any feedback. Hans has really opened up a can of worms here. Just what is being measured when we say PAR. It is supposed to be an approximation of the 'average' photosynthetic action spectrum of higher plants, but it is not specifically defined. Each photosynthetic organism will have a slightly different photosynthetic response because of differences in pigmentation, but despite the differences, a common definition of PAR makes direct comparisons with other people's work possible. A conventional PAR sensor measures µmol photons/m2/s between 400 and 700nm. The LI-190S and LI-192S from Li-Cor are widely used by Plant Physiologists across a range of disciplines (terrestrial and crop plants, submerged and emergent macrophytes, algal and cyanobacteria) and are almost regarded as defacto standards. They have linear, but not flat, responses from 400nm (60%) to 700nm (100%). I would choose a sensor which has a similar response, if only to make your PAR measurements compatible with everyone elses. Conversion between different methods of measuring photon irradiance (PAR, Wm-2, lux etc) is already difficult enough without the added problems of yet more units. -------------------------------------------------------------------------- Philip Orr E-mail philip@griffith.dwr.csiro.au CSIRO Division of Water Resources, FINGER for PGP Public Key Locked Bag No3. Phone +61 69 62 5604 (Home) Griffith NSW 2680 Phone +61 69 60 1555 (Work) Australia FAX +61 69 60 1600 (Work) TALK anyone@orr2.griffith.dwr.csiro.au *** Suburbs are where they cut down all the trees *** *** then name streets after them - Alfred E. Neuman *** (C) Copyright 1996 -------------------------------------------------------------------------- From JOSKA@BOTZOO.UCT.AC.ZAWed Aug 14 12:20:42 1996 Date: Thu, 6 Jun 1996 09:42:50 SAST-2 From: "JOSKA, MAP, PODGE, MRS" To: Multiple recipients of list ALGAE-L Subject: Re: Photon flux density measurement In our Phycology experiments we have been using a SKYE instrument which measures light in micro Einsteins. It is a very reliable instrument and we can also measure light intensity under water with this probe. I assume this is what you mean by a Photon flux density measurement. If you want any more information let me know.Margaret Anne Joska Phycology Laboratory Botany Department University of Cape Town Rondebosch 7700 South Africa. Fax: 027 21 6504041 Tel: 027 21 6503402 Email: joska@botzoo.uct.ac.za From H.Sluiman@RBGE.ORG.UKWed Aug 14 12:20:49 1996 Date: Wed, 5 Jun 1996 17:04:21 -0300 From: Hans Sluiman To: Multiple recipients of list ALGAE-L Subject: Photon flux density measurement We need a photon flux density meter and one of the suppliers I have contacted offers two different sensors: a Quantum sensor which has a more or less flat response between 400 and 700 nm and a PAR "Special" sensor which has a response curve that closely mimics the typical photosynthetic action spectrum of higher plants. Which sensor would be preferable or more accurate when measuring PAR (Photosynthetic Active Radiation) in growth cabinets where a variety of algal (green, brown, diatoms....) cultures are kept? Which type of sensor do experimental phycologists commonly use? Thanks for any feedback. Hans Sluiman ************************************* ** Hans J. Sluiman ** ** Royal Botanic Garden ** ** 20A Inverleith Row ** ** Edinburgh EH3 5LR ** ** Scotland (UK) ** ** Phone: +44 131 4590446 ext. 258 ** ** Fax: +44 131 5520382 ** ** http://www.rbge.org.uk ** ************************************* From henley@OKWAY.OKSTATE.EDUWed Aug 14 12:20:55 1996 Date: Thu, 6 Jun 1996 10:44:53 -0500 From: William Henley To: Multiple recipients of list ALGAE-L Subject: PAR sensors (reply) In response to Hans Sluiman's inquiry about PFD sensors, my opinion is that the best would be to have the flat spectral response, which one can always correct later for the absorption properties of one's own critters. Unlike higher plants that are fairly uniform in their absorption spectra, algae differ radically among taxa and also individual taxa exhibit much wider ranges of pigment acclimation (qualitative and quantitative) than higher plants, so a pre-corrected PFR sensor would be inappropriate and probably impossible. Any dissenting opinions out there? Bill Henley (henley@okway.okstate.edu) From lizotte@VAXA.CIS.UWOSH.EDUWed Aug 14 12:21:02 1996 Date: Fri, 7 Jun 1996 08:34:18 -0500 From: Michael Lizotte To: Multiple recipients of list ALGAE-L Subject: Re: PAR Sensors I would clarify one point in agreeing with William Henley: remember that a "flat response" can be a slope if the units are photons (einsteins) rather than energy (watts), as mentioned by Phillip Orr. The main point is that you cannot build a universal weighted spectrum PAR sensor to cover all the possibilities with algae (amongst taxa or even for acclimation by a single species). For algae, a spectrally-weighted light intensity, which would be important to know where light is limiting photosynthesis, can be calculated as something like Photosynthetically Usable Radiation (PUR: Morel, 1978, Deep-Sea Res. 25:673-688). Estimating PUR requires knowledge of the spectrum of light and the absorption spectrum of the algae. ***************************************************************** Michael P. Lizotte //tel. 414-424-0845 Department of Biology & Microbiology //fax 414-424-0845 University of Wisconsin Oshkosh //lizotte@vaxa.cis.uwosh.edu 800 Algoma Blvd. Oshkosh, WI 64901-8640 From edrew@OZEMAIL.COM.AUWed Aug 14 12:21:13 1996 Date: Sat, 8 Jun 1996 21:51:57 +1000 From: Edward Drew To: Multiple recipients of list ALGAE-L Subject: Re: Photon flux density measurement Hans - you have already seen this, but I should have sent it via the List.. >Date: Thu, 06 Jun 1996 20:12:31 >To: Hans Sluiman >From: edrew@ozemail.com.au >Subject: Re: Photon flux density measurement > > >Your supplier seems a little confused, or else you are misinterpretting their literature. > >Virtually all photosynthesis physiologists use a quantum PAR meter, and almost all get them from Licor (of Lincoln, Nebraska). Any good scientific instrument supplier should be able to get hold of one, but be warned, they are not cheap. > >The PAR designation indicates that it measures only between 400 and 700 nm, although some researchers and suppliers extend this a bit to cover 350 to 750. > >The Quantum designation indicates that the response is proportional to the energy of the quanta at different wavelengths, varying linearly from 100% at 700 nm down to about 60% at 400 nm. > >These instruments are designed for use with crop plants, and represent only the best approximation currently available for the rather different action spectra of various algae. > >You might find the following reference useful as an intruduction to light and algae: > >Drew E A (1983) Light. Chapter 2 in The sublittoral Environment of the British Isles. Edited by R Earll & D Erwin. Oxford University Press. pp 10-57 > >Hope this helps. I could send you a photocopy if the references proves elusive. > >Ed > > --------------------------- Dr Edward A Drew ------------------------- > | PO Box 361, Castletown, Hyde Park, Townsville, Q 4812, Australia | > | Tel +61-077-724452 Fax +61-077-213538 Mobile +61-014-879869 | > | E-mail edrew@ozemail.com.au WWW http://www.ozemail.com.au/~edrew | > ---------------------------------------------------------------------- > Ed ------------------------- Dr Edward A Drew ----------------------- | PO Box 361, Castletown, Hyde Park, Townsville, Q 4812, Australia | | Tel +61-077-724452 Fax +61-077-213538 Mobile +61-014-879869 | | Email edrew@ozemail.com.au WWW http://www.ozemail.com.au/~edrew | ------------------------------------------------------------------