Re: increased K+ needs in low light?

>>"Under very humid conditions, where the light level is lower, you plant will
>>require more potassium -- as much as twice the normal amount.  This is
>>because photosynthesis is more difficult with a lower light level and
>>potassium is necessary for photosynthesis."

I had a course in plant nutrition, and I never heard of this increased need
for potassium in low light.  The argument also sounds wrong from a
biochemical point of view.  It doesn't make sense to say that
photosynthesis is 'more difficult' in low light.  The process of
photosynthesis occurs at a lower rate because chlorophyll absorbs fewer
photons of light per second.  A photon is a photon, regardless of the light
level, and once absorbed by chlorophyll, the subsequent reactions will be
the same regardless of the light level.  Potassium is known to be an
activator of many enzymes and to play an important role in osmosis and
ionic balance.  I can't find any direct role for potassium in
photosynthesis in my textbooks.  I could go on, but I would like to see
some scientific substantiation of this claim for higher K in low light.

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174