As I remember, Graphite was used by Prof Joseph Arditti as a colourant for agar about 30+ years ago when he was working with antimicrobials in culture media which would have been trapped by charcoal. A good source of powdered graphite is puff lubricant for keyholes. regards, greig
----- Original Message ----- From: <[EMAIL PROTECTED]> Sent: Thursday, July 15, 2004 12:32 PM Subject: Orchids Digest, Vol 6, Issue 284 Message: 4 > > Hildegard Crous stated: > > "I get excellent root development on terrestrial orchids if the plants are > initially on a clear medium, (1/2 MS) and then replated onto the same > medium > but containing charcoal. However, with the follow up replate, (charcoal > added > to the medium), the plants lose colour, (pH drops and leaves turn white, ) > probably because the charcoal has adsorbed some critical nutrients." > > I wonder if you couldn't get the "darkening at the roots" effect that > charcoal > provides without the non-specific adsorption/absorption problems by using > an > alternate insoluble, dark pigmented carbon compound. What I would > tentatively > suggest for this purpose is graphite which I think (but don't know for > sure) is > relatively inert and doesn't adsorb the way charcoal does. How's that, > substitute > one artists' drawing medium for another? If you try this, and it works > well, please > remember to credit me with the idea (in the unlikely event it turns out to > be unique). > > Best of luck, > > Marquis _______________________________________________ the OrchidGuide Digest (OGD) [EMAIL PROTECTED] http://lists.orchidguide.com/mailman/listinfo/orchids
