Abstract
In the conventional ultra-fast up-conversion fluorescence measurement, fluorescence emitted from the opposite side of the laser excitation is detected. Only a transparent sample could be measured by this type of system. For the noninvasive in vivo measurement, we developed a new reflection-type system, in which the fluorescence emitted at the same side as the laser excitation can be detected. We measured the rise and decay of fluorescence from the green alga inside dried lichen. Lichens are drought tolerant, and have a mechanism to convert the excess light energy into heat to prevent the photoinhibition. We directly measured the time constant of the fluorescence lifetime of dry lichen to be 20 ps. No fluorescence rise corresponding to the dacay was observed suggesting that the most of the excitation energy is quenched within 20 ps.The reflection type system enables us to perform noninvasive ultra-fast measurements of opaque samples like leaves in vivo.
