Subject: Q: measuring light in liverwort cultures

From: [email-masked] (H.J. Sluiman)
Date: 18 May 1995 13:10:22 +0100

Measuring light quantity and quality in growth-chamber cultures of 
liverworts:
As part of a Doctoral project on liverwort (Asterella) taxonomy, I am 
trying to measure morphological consequences of shading. I am 
growing cultures in alternate bright and shaded (by muslin) shelves of 
a growth chamber. The effects are striking: longer narrower thalli in 
shade. How can I measure the mean light quantity and quality for 
each shelf of the chamber? What equipment do I need and can I
borrow or hire it in Britain/ Scotland/ Edinburgh?
David Long, Royal Botanic Garden Edinburgh ([email-masked])

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From: [email-masked] (Jeff Jorgensen)
Date: Sun, 21 May 1995 15:30:20 GMT

>David Long, Royal Botanic Garden Edinburgh ([email-masked])

David;
There are two measurements of light used commonly.
      -Irradience is a measure of flux of photons across a known area
per second, ie Mols photons/sec/square m. This is a measure of light
intensity formerly known as the Einstien
      -Fluence is a measure of light or energy flux through a given
area over any given period of time, ie Joules/square m/hour (or any
period of time). This is a quantification of a dose of light
      
There are commercially available devices that can take both of these
readings from one instrument. I have no idea where you might procure
these devices in the UK.

Another consideration might be a shift in wavelength caused by the
shading material. You might want to investigate this if you are trying
to simulate a  naturally occuring environment.

Good Luck!