Organic Hydroponics

Anne Gillen ez049617 at bullwinkle.ucdavis.edu
Wed Oct 2 21:58:06 EST 1996


BRateaver (brateaver at aol.com) wrote:
: You all seem to be completely unaware that nutrients DO NOT need to be
: soluble to be absorbed by cells, no matter whether cells are from humans,
: animals or plants.
: 
: The whole idea of solublility is based on the theories of ion absorption.
: 
: Plants absorb the same way that animals and people absorb--by endocytosis.
: 
: I wish people would STOP insisting on solubility.  That is not a
: requirement.
: 
: Yes, what is used in hydroponics is soluble, but a cell that takes in ions
: has to first chelate them to enable those molecules to move through living
: tissue. That causes cells to have to put out more energy to do the
: chelating. Anyway, it is not the ions in solution that reach absorbing
: root hair cells, because the root hairs are covered with mucigel and are
: not in direct contact with solutions used.
: 
: B. Rateaver

-- 

Could you provide a reference?  Accorrding to my plant physiology book
(Plant Physiology by Taiz and Zeiger, 1991. The Benjamion/Cummings
Company, Inc.) Ions can be taken up roots either by passive or active
transport. Active transport is not the same as a molecular level as
endocytosis. Active transport is thought to involve specific transport
proteins located in the cell membrane which form a channel through which
ions move.  In endocytosis a portion of the cell membrane forms a vesical
which moves into the cell.  This does not happen plants.  "In 
animal cells, coated vesicles function in endocytosis and in the transfer
of material within the endomembrane system.  In plants, coated vesicles
have been implicated in the transport of storage protein to the
specialized protein-storing vacuoles." p. 16.  

Another good reference is
Marschner, Horst.  1995. Mineral Nutrition of Higher Plants, 2nd Edition,
Academic Press, Harcourt Brace & Company, New York

I also checked with my husband who has a Ph.D. in plant physiology and has
studied mineral nutrition of plants with Dr. Marschner. There is a lot of
evidence that ions are taken up directly by plants without need
of chelators and they can be tranlocated in the plant without being
chelated.  Which is not to say that chelators do not exist and function in
plant solute transport.

I hope this clarifies things,

Anne 
*******************************************************************************
    Anne M. Gillen                           E-mail: amgillen at ucdavis.edu
    Pomology Department                    
    University of California at Davis
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