Plant flourescence

Tony Travis ajt at
Sat Jan 13 14:53:53 EST 1996

Eric Grunden wrote:
> In a previous article, siwek at (D. Siwek) says:
> >I am seeking any information on flourescent emmisions by plants.
> >Does it happen?
>                         *******
> I have seen it produced by inserting firefly genes into tobacco
> plants, but I've never heard of it occurring naturally....

Firefly's phosphoresce (emit light without combustion or heat) using 
'luciferase' and ATP ...

Fluorescence:  emiting light of a different wavelength to that absorbed.

Plants (leaves) do fluoresce when the energy of light absorbed by the 
photosystems is not captured by an electron transport chain in the 
chloroplast.  The energy absorbed by the photosynthetic pigments is 
dissipated as heat, or light at a longer wavelength to that absorbed if 
not used inphotosynthesis.

This phenomenon has been used to produce commercial leaf 'productivity' 
meters that assess photosynthetic potential by measuring how much of the 
incident photosynthetically active radiation (PAR 400-700nm) is emitted 
as fluorescence.  The idea is that the less light re-radiated as 
fluorescence, the more can be captured and used in photosynthesis.

The fluorescence of chlorophyll, one of the major photosynthetic pigments 
present in leaves, can be demonstrated by extracting the pigment from 
leaves with acetone and shining a light through the resulting solution.  
When uncoupled from the photosystems present in chloroplasts, all the 
light absorbed by the pigment is dissipated as heat or fluorescence.

Leaves, particularly leaf epidermis, also contain a large number of 
phenolic compounds which are highly fluorescent when irradiated by UV 
light.  This may not be visible to a human observer, but many 
pollentating insects have vision that extends into the UV and it is 
thought they recognise species by the colour of their flowers in the UV 
region of the spectrum rather than the PAR region which is visible to us.

Dr. A.J.Travis,                       |  mailto:ajt at
Rowett Research Institute,            |
Greenburn Road, Bucksburn,            |   phone:+44 (0)1224 712751
Aberdeen AB2 9SB, Scotland, UK.       |     fax:+44 (0)1224 716687

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