Cold tolerance is definitly not an easy task.. I don't know for certian, but
I'll assume that cold tolerance is a multi-gene adaptation... And these genes
may or may not be linked, and may not be the same in each family (even genus
and species). In otherwords, it's a difficult task.
The cloning of the 'trap' genes into other plants would be interesting,
however as we all know the importance for the proper environmental
conditions, the idea is very far-fetched, and would probably not be
practical in any sense.
Currently, the way to make larger plants would involve hormone addition.
Somthing to try.. A little GA to increase the internode distance. Something to
try.
Jeff