A little on chlorophyll fluorescence measurements:

Chlorophyll fluorescence measurements include light-adapted or dark-adapted measurements. As you may know, part of the energy (light) absorbed is used to excite electrons that will be moved through the electron transport chain. Depending on the environmental and plant conditions, part of the energy is released as heat and as fluorescence.

You can use dark-adapted leaves for measuring parameters such as Fv/Fm (the maximum efficiency of the PSII). Generally, measurements taken using dark-adapted leaves are made at predawn, but you can also do it after adapting leaves to darkness during the day by using some clips. However, you will need light-adapted leaves to measure parameters such as yield and non-photochemical quenching (NPQ), which basically gives you an estimation of the efficiency of heat dissipation.

Also, if you work in a field experiment, you should consider factors such as low temperatures, which can increase electron transport to other electron sinks and reduce the yield of CO2 fixation.

I would underline that the problem is the meaning of what you measure: if you intend to dark adapted values, it would be OK, and I adhere to what Juan wrote. If you want to measure light adapted values, which would be the meaning of adapting to light leaves that are dark adapted?

As a practical problem, derived from colder temperatures, you coul face condensation onthe leaf, which might interfere in the measurements

I agree with Juan and Xavier. It would depend on which parameters you would consider. Yes, condensation on the leaves is important as it affects the optical property of leaf and thereby the fluorescence signal.

But there are some other factors that also need to be considered even within Fv/Fm measurements. You may refer (Sharma et al. 2012, Functional Plant Biology, 39, 936-947) if there's anything that could help you.

As you may know, part of the energy (light) absorbed is used to excite electrons that will be moved through the electron transport chain. and a little on chlorophyll fluorescence measurements. Chlorophyll fluorescence measurements include light-adapted or dark-adapted measurements.

Dark adapted fluorescence can be measured. But precautions should be made for speciafic experimentation and interpretation of these data.