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Re: algae, plants and potassium

     >I've heard or read that potassium is used by algae and plants for 
     >turgor, phototropism and transport.  Are there other important roles? 
     >It seems to me that these functions (with the exception of turgor) 
     >might be much more important to higher plants than they are to algae. 
     >I've never heard of algae "following the sun" and they would seem to 
     >have much smaller transport requirements than higher plants.
     >Does a shortage of potassium favor the growth of algae over higher 
     I don't see how.  K deficiency would be equally perturbing to both, as 
     algae have approximately the same K requirements as higher plants, 
     i.e., their intracellular K concentrations are about equal.  Both have 
     an amazing ability to uptake and concentrate K many many times greater 
     than that of their external environment.  K is also an activator of 
     some enzymes, BTW.  It's mainly the osmotic requirements for K that 
     cause plants to concentrate it in their cells, though.
     However, potassium is strongly adsorbed by many soils, so if you have 
     a substrate with a high potassium-binding capacity, then I can 
     envision a situation where the water column could be low in potassium, 
     but the soil could have tons o' K.  Here, it seems this situation 
     would favor rooted plants over non-rooted ones.
     Kinda like that P-limiting idea Sears and Conlin came up with ;-)