"Hildegard Crous" <[EMAIL PROTECTED]> queried thusly: > Hi All, > perhaps someone out there could throw some light on this matter? > 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've wondered about this myself, but came to the conclusion that although charcoal may adsorb certain compounds, this does not necessarily mean that they are sequestered such that they are biologically unavailable. This is to say, no *specific* nutrient deficiency is observed, but rather a general decline of the plant. What are your carbon sources (i.e., sugars)? > I had hoped that adding IBA to the clear medium would stimulate root > development to such an extent that it would be unnecessary to incorporate any > charcoal. IBA (indol-butyric acid) is a powerful rooting hormone generally > used in tissue culture practices, - would anyone have any any knowledge as to > whether it would perhaps inhibit rooting of terrestiral orchids if the > concentration levels in the medium were incorrect? You'd have to do a spread of concentrations with the plants and media you are employing. Specifically, you'd have to try with and without charcoal (charcoal WILL remove organic constituents like IBA), and in different concentrations. I typically try a "doubling" spread, like 1, 2, 4, 8, 16, 32 (and then in the other direction- 0.5, 0.25, 0.125, etc., if required). Naturally, with something like IBA, you wouldn't need to go very far in either direction. > Adding banana to the medium is great, but root development is still poor. Banana is an interesting mix; it's unclear WHY there's such an influence. Some attribute it to the hormones, but I think it's the sugars. The B852 mixture from PhytoTech labs (50/50 mix of freeze-dried banana and malto-dextrin) is very effective at making germination more "comfortable" for some species at 5 grams/liter added to P668 (similar to the 1/2 strength M&S), and very good at growing on plants in replate at 21 grams/liter added (again) to P668. However, banana *may* inhibit germination of some species; I suspect that mainly paphs are affected. Use coconut for these species. Surely someone with more expertise in the subject (Alan?) will chime in! Which genera have proven problematic for you? I'd try experimentation with B852 (PhytoTech labs) on top of P668 or 1/2 MS, either singly or in conjunction with manipulation of monosaccharides (glucose at 8-12 grams/liter) or sucrose (10-15 grams/liter) if you must. Glucose strongly preferred for these terrestrials, but sucrose isn't terribly objectionable. Good luck, -AJHicks The Orchid Seedbank Chandler, AZ _______________________________________________ the OrchidGuide Digest (OGD) [EMAIL PROTECTED] http://lists.orchidguide.com/mailman/listinfo/orchids
