Re: Ca/Mg/K

>From: eworobe at cc_UManitoba.CA
>Date: Fri, 21 Feb 1997 07:34:35 -0600 (CST)
>Subject: Re: Ca/Mg/K
>Potassium is needed in the water column because it is used to maintain
>the ionic balance within the plant. There is a dynamic equilibrium
>between the K inside and outside the plant. Calcium and Magnesium are
>required in the water because they do not transport readily within the
>xylem of aquatic plants. Calcium in particlular is necessary in the water
>because there is an extracellular requirement for Ca ... if the Ca level
>drops too low then the cell wall does not form properly.

Dave, can you tell us more details about this?  I am wondering why Ca and
Mg do not travel well from the roots to the shoot in aquatic plants but
other nutrients do travel well.  Is the xylem the only means of transport,
or can the phloem also transport nutrients?  Clearly terrestrial plants get
all their nutrients, including Ca and Mg by way of their roots.  While
submerged aquatics do not have nearly the amount of water carried from
roots to leaves as terrestrial plants, they still apparently have some
water movement from roots to leaves.  Aquatic plants that take up Ca from
the water are able, apparently, to send it to their roots.  If they can
send it to their roots, why can't they send it from their roots?

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174
Goofing off instead of working in pleasant, although cooler, Jackson,