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Infared Light--Does it grow plants?

Jeffrey Kirby ez043438 at dilbert.ucdavis.edu
Tue Apr 7 11:21:34 EST 1998

Ross Koning (koning at ECSUC.CTSTATEU.EDU) wrote:
: At 3:00 AM -0400 4/7/98, Jeffrey Kirby wrote:
: >Ross Koning (koning at ECSUC.CTSTATEU.EDU) wrote:
: >: The Krebs Cycle does not respond to light...neither
: >: does the Calvin Cycle.  The light reactions, which
: >
: >We really must stop calling them the light reactions since that implies
: >that the Calvin cycle contains the dark reactions.

: I don't think plant physiologists will go from "light
: reactions" to "them". If we want to change the name
: of the light reactions we will need an alternative
: name.

I hope you didn't take my previous response as a personal flame - it
wasn't meant to be. It was instead a reaction of the wide-spread
use of the terminology "light reactions" (which I usually refer to as "the
so-called 'light reactions'"). By labeling these reactions the light
reactions, it excludes other reactions from being light reactions, even if
they only take place in the light (like the Calvin cycle). That's what my
argument is. Incidentally, I did give an alternative name in my posting:
the photosynthetic electron transport chain (if you don't care to write it
out every time, define P-ETC or PS-ETC as an acronym for it). 

: The name "dark reactions", I agree, should be replaced
: with Calvin Cycle, carbon-fixation pathway, or whatever...

I think RPP (reductive pentose phosphate) cycle is the latest flavor.

: I don't agree that using "light reactions" forces one
: to think of the Calvin Cycle as "dark reactions"
: (which is completely wrong-headed!). That argument
: is very much like the one that our students use...
: "if you say that plants do photosynthesis then that
: implies plants do not do respiration!"  Such arguments
: are inherently flawed

I don't believe my argument to be parallel with your students' argument. 
My problem is with the exclusivity used with a phrase that would normally
be broad in the English language. "Light reactions" implies reactions that
occur (only) in the light - they depend on light being present. My
argument is that there are other reactions (within photosynthesis) which
fit this description and that it is therefore a poor name (due to its lack
of clarity). You're correct that this does not assign the "dark reactions"
to other reactions.

Am I making sense? If I'm not, please keep shooting down my arguments
since it's the only way I'm going to learn to be lucid. 


-----------------------------                                      -----
        Jeffrey A. Kirby                         jakirby at ucdavis.edu


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