To: bryonet-l@mtu.edu
From: "Michael A. Grusak" <mgrusak@bcm.tmc.edu>
Subject: RE: BRYONET: ferric tartrate
Dear Bernard,
I thought I would chime in on this one. I haven't cultured bryophytes for
several years, but I do work in the field of Fe nutrition. Ross Koning
commented that sequestrene might be used, as an alternative form of
chelated Fe. I'm not sure which chelate is in sequestrene 440 - it's
probably either DTPA or EDDHA, but in either case, you should note that
most of these synthetic iron chelates are light sensitive and will break
down with time, thereby releasing the Fe. You then end up with Fe
precipitated to phosphates in your solution. You also should keep in mind
that the different chelates have upper pH limits, after which they will
release the Fe. I presume you're not culturing things in the alkaline
range, but it's something to consider. (I'm not sure what the optimal
range is for ferric tartrate.) One additional thing to note is that the
commercial formulations (sequestrene and others) have lots of other things
in them besides just the Fe chelate. In particular, various phenolics have
been identified in some of the commercial preparations - these are a
hold-over from the production of the chelates. So, if you think these
might influence the growth of your cultures, you might want to consider
buying the purified chelates.
Jenny Rowntree also mentioned that some of the culture recipes call for
FeSO4:7H20. This is the ferrous form of Fe, but it should be noted that in
an oxygenated solution, almost all of the ferrous iron in solution will be
converted to ferric iron (of course there will be an equilibrium - but only
a very small amount of ferrous iron will be present). Apparently, even
non-chelated Fe will work in many cases, but I suspect it really boils down
to how actively the cultured cells are growing. Iron is a micronutrient,
after all, and cells don't need that much iron -but an actively growing
culture might benefit from a chelated, readily available iron source.
Cheers,
Mike Grusak
Michael A. Grusak, Ph.D.
USDA-ARS Plant Physiologist
Associate Professor
Dept. of Pediatrics, Baylor College of Medicine
USDA-ARS Children's Nutrition Research Center
1100 Bates Street
Houston, TX 77030-2600
phone: 713-798-7044
FAX: 713-798-7078
e-mail: mgrusak@bcm.tmc.edu
http://www.bcm.tmc.edu/cnrc/faculty/grusak.htm
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