Re: Comparing chlorophylls action spectrum with its absorption spectrum

Hi, 

Actually spectrophotometer is up to now the only equipment we use to measure
absorption spectrum, and the older model is not very expensive. Without it 
you can not get valuable information about chlorophylls action spectrum.

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Admin note: 

David Hershey adds the following:

To do a chlorophyll absorption spectrum requires a spectrophotometer which
is not an uncommon instrument in American high schools.

A photosynthesis action spectrum was probably first generated in 1883 by
T.W. Engelmann who used a prism to shine different colors of light on a
filamentous algae (Spirogyra) on a microscope slide. The rate of
photosynthesis with different colors of light was measured visually by
observing bacteria that were attracted to oxygen. The colors that produced
the most photosynthesis also produced the most oxygen and attracted the
most bacteria. This experiment is often mentioned in botany textbooks such
as Stern (1991) or Moore and Clark (1995).

You can do a qualitative photosynthesis action spectrum by using the leaf
disk photosynthesis assay described in my book and using colored films
around the syringe. The difficulty in doing a quantitative photosynthesis
action spectrum is mainly in getting equal amounts of light of each color.
To do that a botanist would use a quantum light sensor which measures
photosynthetically active radiation (PAR) and make sure the PAR was the
same for each color.

References

Hershey, D.R. 1995. Plant Biology Science Projects. New York: Wiley.

Moore, R. and Clark, W.D. 1995. Botany: Plant Form and Function. Dubuque,
Iowa: Wm. C. Brown.

Stern, K.L. 1991. Introductory Plant Biology. Dubuque, Iowa: Wm. C. Brown.


David Hershey