No, no PhD-stress here, or not more than just a little. I have been teaching a practical course on the measurement of plant stress to our master students. They are asked to study stress levels in plant leaves with the use of two old but impressive measuring devices that capture leaf fluorescence.
Yes, I am really talking about fluorescence in which objects emit light, even when the light source is already gone. No, this does not result in leaves glooming like eyes of a cat in the dark, unfortunately. Leaves send out light at a wavelength invisible for the eye (but not for my old but impressive devices): infrared.
In the practical course, students find out that the fluorescence of a leaf is the result of light being absorbed by the leaf that cannot be used by photosynthesis. It serves hence an indirect way of measuring how much light energy the plants can use, which is then a measure for their health level.
With an ingenuous sequence of light pulses to activate and deactivate the photosynthesis apparatus of the leave, we can find out how much a plant is suffering.
I for my part, learned a lot of this practical course, of the experiment as well as the teaching experience. Let me see next weeks if the same holds true for the students as soon as they start handing in their reports…