Subject: Need Info on best colours of light for p/s

From: bbitting <[email-masked]>
Date: 12 Apr 1996 02:32:15 GMT

I am currently working on a high school boilogy lab that involves 
determining the colours of light that best effect photosynthetic activity, 
the only info. I have found was that RED and VIOLET are obsorbed by 
chlorophyll but that does not necessarily mean they effect p/s the most. 
Anyway if anyone knows or knows of a good site where I can find the info. 
I would greatly appreciate it.

Elijah Bitting

[email-masked]

&;-/  a thankyou fr. Elvis

:@) and my pet pig

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From: "Brian W. Tague" <[email-masked]>
Date: 12 Apr 1996 11:39:05 GMT

>&;-/  a thankyou fr. Elvis

A good site to find this information would be in the library, in a book on plant biology, physiology, etc.

Brian

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From: [email-masked] (Judith Kelly)
Date: 12 Apr 1996 20:14:33 -0400

Ther is an ancient saying: "Give me a fish and I will eat for today; teach 
me to fish and I will eat for the rest of my life"
You say this is for a biology lab.  Good!  Instead of looking up the 
information, design an experiment to test which color of light is most 
effective.  The end result of photosynthesis is the formation on glucose 
which the plant converts to starch to store energy.  Therefore the amount 
of starch produced may be used to measure the amount of photosynthesis 
which occurred.  Try varying the color of light a leaf recieves by 
covering the leaf with colored plastic sheets, obtainable at an art 
supplies store.  Geraniums make a good experimental subject.  The library 
is a good source of information on science fair projects.  Trust me, this 
is a classic plant physiology experiment.  Good luck!
J. Kelly
<[email-masked]>

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From: bbitting <[email-masked]>
Date: 13 Apr 1996 15:53:17 GMT

Judith, thanks for the advice, I was already planning on a similar 
expirement, but I need sources to form my priliminary hypothesis.  And I 
already checked my library, but I thought someone might know of a web site 
with good info. on this topic.

Thanks again

Elijah Bitting

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From: [email-masked] (Marco_Bleeker)
Date: Sun, 14 Apr 1996 00:55:26 GMT

>I would greatly appreciate it.

OK Elijah, I looked it up for ye. W. Nultsch says: 400 - 470 nm,
peaking at 430 nm (blue), and 640 - 670 nm, with the peak at 660 nm
(red). Essentially, it is anything but green (the color of chlorophyl)
- and also far-red (680 - 700 nm) is completely lacking.  Both
absortion peaks contribute to photosynthesis. In vitro, the absortion
peak in blue is higher, but in the living plant, and looking at the
ultimate product (starch), the effect of red seems to be higher.

Bye, Marco

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From: [email-masked] (Mahlon G. Kelly)
Date: Mon, 15 Apr 1996 06:25:34 GMT

> >I would greatly appreciate it.

Better yet, don't bother to measure the starch production, just
the oxygen released. Much easier.

On the other hand, the fellow may not have the light filters
and equipment to do any of the experiments that we are
suggesting.
-- 
Associate Professor (Emeritus)
University of Virginia
[email-masked]

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From: [email-masked] (O Monje)
Date: Thu, 18 Apr 96 05:08:49 GMT

>and equipment to do any of the experiments that we are

Measuring O2 is hard w/o an electrode.....
Going back to the starch....Starch can be detected by using an Iodine stain (messy),
but try looking at stained leaf cuttings under the microscope....It should show you where
p/s is going on, and also where it is stored.

Another suggestion....grow ~10 seedlings under different filters at the same light intensity
for about 5-10 days, harvest them, dry them, and look at the shoot dry weights.  For better uniformity,
you can thin out the seedlings that are not growing well...ie down to 5/treatment. Get a red, blue, and
a green or orange filter.

good luck!

OM