Did you carry out your treatment in the dark or the light?
Did your samples 'see' alot of light between the treatment and going into
the fluorimeter?
If your samples have seen light then it is oftern quite difficult to
reoxidise all od the closed PSII reaction centres and therefore you lose
FV.
Is the loss in FV/FM due to a decrease in Fm or to an increase in F0?
I hope this of some help.
Michael
