[littlefrog]

I have always assumed (with absolutely no proof...) that much of the root loss you see is due to opportunistic fungi/bacterial infection. Also, orchid roots do exchange air gasses, so keeping them entirely submerged can literally suffocate them. Again, an assumption that I have always had, but no references to back that up...

All of that said, I have had some luck in the distant past with completely hydroponic culture. IE, a plant sitting with its roots in a jar of water. Took a while to adjust to that culture, but I had a few den-phals that went nuts in that system. I think that came from a grower who used to be on the internet when it was 'new' - Rod Venger. He is out of business now.