I wouldn't leave it outside. If it happened to survive the sporadic freezing nights, you're right, it probably wouldn't yield anything substantial.

From what I remember reading about a few purple strains, cooler temperatures will result in a darker purple. Potency would probably remain unaffected, but you'd most likely have a purple -er bud nonetheless.

I've heard stories of somehow supplementing plants with nitrous oxide, but I couldn't attest to anything I haven't tried. If I had a tank of NOS, I probably would be worrying too much about supplementing the plants. I'd be too busy floating on cloud #9 from doing "whippets" all the time! :upsidedow