I really do not know how to answer if they will be effected negatively by the temp reversal... Could one reset their internal clock by getting black out curtains and making the light situation reversed also. But then one would be wedded to the late night.. I say this more as a rhetorical question than as a recommendation of a thing that one should do. The idea is to make the day night . But I am usually one who likes less hassle the better. I have always pict plants that fit with my life styl and not the reverse.

No idea either on how to answer if would effect them for better or worse but another consideration is. It's not so much the amount of lighting time your cacti get right now it's also the intensity behind the light.

I tend to think it would be very difficult to get ideal " wake up cacti "lighting in a small sized room this time of the year. I would think the bulb assisted lighting in a small room for extended amount of time may not have an effect if cati are already resting.

Using your mentioned room hi to low temp as a reference the same principals may also be a factor for heat changes when considering it gets much hotter than 70 degrees in seasonal growing of cacti and knowing most cacti can easily tolerate very hi to low temp changes that can sometimes equal more than 20 degrees in a 24 hour time does propose a tougher question for any realistic answer

If cati where people I would also agree that we cant adjust any internal clock on any one or any plant by understanding some people can sleep as long as needed if tired enough regardless of the amount of dark or light or time of day people can also remain awake if wanting to regardless if dark or light.

Again as cacti aren't people I do know if we as people when awake dont provide a cati enough bright and direct sun light with reasonable heat during it's awake (or growing) times we can introduce other growing problems that MIGHT be resolved if growing problems where to develop.

On a later note as none of us know what kind of cacti your asking about I add Thank-You for adding edit features GW

This post was edited by mrlike2u on Fri, Dec 7, 12 at 0:01