I tried colchicine a few years ago with radish. I took some colchicum autumnale bulbs in summer. I cleaned them and crushed them. The sap coming from pressing was put on a paper sheet with radish seeds. i also put some seed on paper with only water. after they germinated i put them into normal potting soil. some of the seedlings treated with colchicine looked different. THey were much thicker and more green. this was an indication that plyploids were formed. Unfortunalty i threw them away after some days. I want to try it again with other seed.

I`m looking forward to people who did this and other mutagenic treatments also.

Using colchicine, I created a polyploid tomato plant from Supersteak. It was dark green and refused to bloom.

I have used a commercial gibberellin antagonist, Arest, to prevent stem or petiole elongation of several plants including banana. If you give a banana plant enough Arest, it will end up looking like a bromeliad. Gibberellic acid can be use to countereact Arest.

The most interesting plant growth regulators are brassinosteroids, which I have been unable to obtain.

BTW, I forgot to mention the link below might be of interst.

Here is a link that might be useful: Chimeras

A good species to try (Dendrobium moniliformeis ) is mentioned at the link below. The species is pictured in a link about 5 or 6 followups down the page. The title of the OP is off topic.

Interesting that a topic can get better as we get more followups.

Here is a link that might be useful: Gardenweb botany forum

Here is a discussion of chromosome doubling in the Hybridizing Forum.

Here is a link that might be useful: Ploidy Doubling