mineral nutrition

Warwick Silvester w.silvester at WAIKATO.AC.NZ
Thu Mar 4 16:54:04 EST 1999

Dear  Carl   Chlorine as an essential element for plants

  The first definitive paper on the essential nature of  Cl for plants was
by  Broyer et. al. in 1954. Machlis and Torrey came out in  1956  and in
fact on page 43 they say  "Evidence that Cl is essential has recently been
presented"  they go on to  show they are skeptical of the claim saying it
will require verification in many other labs.. so there are historical
reasons why  Cl is left out of their solution.  The ubiquity of Cl means
that only in the cleanest of environments would there be any deficiency
seen.  we find there is  significant Cl in our RO water  and if you live
near the sea it is hard to keep Cl low. Cl is well accepted as an essential
element see Marschner  Mineral Nutrition of Higher Plants p335 and eg Taiz
and Zeiger  p104
Warwick Silvester

For years I've made general-use nutrient solutions with what I suspect is a
>standard recipe (it's in the Machlis and Torrey lab manual, for those of
>you who go back that far, and also in the Reiss lab manual).  Only today
>did I notice that this recipe has no chloride - nitrate, phosphate, and
>sulfate are the major anions.  Chloride is not an essential element, but
>then whenever we talk about guard cells we say that chloride (as well as
>malate) is the major counterion.  Indeed, discussions of the general
>electrophysiology of plant cells seem always to involve chloride.
>So how come if chloride is so important it isn't in the nutrient solution?
>Chloride does get added when one is, for example, making a solution lacking
>nitrate -- substitute KCl for KNO3.  How do plants without chloride manage
>their membrane potentials, open/close their stomata, etc.?  Can they do it
>with the other anions?  Am I missing something?
>Carl S. Pike                         (717) 291-3958
>Department of Biology                FAX (717) 399-4548
>Franklin and Marshall College        email  C_PIKE at ACAD.FANDM.EDU
>P.O. Box 3003
>Lancaster, PA  17604-3003  USA

Warwick Silvester                      Ph. +64-7-838 4613  and voicemail
Dept of Biological Sciences          Fax +64-7-838 4324
University of Waikato                  Email w.silvester at waikato.ac.nz
Hamilton, New Zealand

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