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
