drosera drosera <droseradrosera@hotmail.com> queried thusly:

> I believe that there was a technique mentioned using sand as a support
> instead of agar (I think that it was an idea from Roger Smith). Is there
> any more information about this?

Dunno about sand, but I've used perlite with orchids with good results.

I've been experimenting with field expedient techniques for use under relatively rudimentary conditions (i.e., in the jungle, for conservation purposes closer to the source) based on information first provided by Moises Behar, M.D..

It's pretty simple: I've been using baby food jars, with about 1" of perlite in them. Add nutrient media (without agar) to just above the level of the perlite. Put a piece of Whatman filter paper on top of the perlite (I suppose almost any paper would do), cap and autoclave.

When cool, seeds may be sown directly on the filter paper.

One interesting note is that because the media has no solidifying agent, there are no problems with potential phytotoxicity as a result of the presence of the gelling agent. Further, because metabolitic byproducts (such as phenolics, which orchids produce in large quantities) are mobilized in the absence of a gelling agent, they are diluted- with less negative effect on growth.

One other factor is that very slow-growing orchids may benefit from this technique, since there is much more liquid present for the plants than when agar is used- it doesn't dry out as quickly. If one desires to keep them growing on, they can use a sterile pipette to withdraw the concentrated solution and replace it with more nutrient solution without disturbing the plants- a possible benefit.

One last note: Ernst (?) experimented with glass wool as a substrate, from which I have drawn conclusions that perlite and glass wool apparently share the same benefits. Inert, silica-based substrates (sand, glass wool, perlite, whatever) should do just fine- they're just one step away from liquid media, after all.

 -AJHicks

 Orchid Seedbank Project