[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Salt

     >On the opposite side of the thought, what is it about salt that is 
     >bad for plants?  I would guess it's not the sodium. If so, the 
     >addition of sodium bicarbonate for buffering would have fallen from 
     >favor a long time ago.  So how do the Cl ions hurt plants? 
     It is the total solute concentration, not necessary NaCl, that can be 
     detrimental to plants.  If the solute concentration surrounding a 
     plant is higher than the concentration within its' cells, then water 
     will move out of the plant via osmosis.  Since most plants do not 
     require sodium, and NaCl is a common solute, it is usually the 
     culprit.  You could dehydrate a plant by immersing it in a solution of 
     sugar, for example, if the concentration was high enough.
     Marine plants can live in high salinity water by excreting excess 
     sodium or by maintaining a high cellular concentration of other 
     solutes, e.g., K, or mannitol, for osmotic balance.
     Many aquarists have reported difficulty growing plants in water with a 
     high (500 ppm +) mineral content.  As I mentioned above, it is the 
     osmotic concentration of solutes, not necessarily the total weight of 
     soultes, that determines suitability, and for that physiologists 
     measure concentrations in osmoles, i.e., the total number of moles of 
     solute per liter of solvent.  Given the recent discussion on units of 
     hardness, I won't even touch this.