MF-F

In the case of fluorescence measurements, one of the fibers guides excitation light to the sample and fluorescence back to the photomultiplier. This fiber can be connected to a “working fiber” (MF-F) which is a single fiber with one free end of 100 μm diameter. The free end can be pulled out to form a tapered tip of 10 to 30 μm. By means of a micromanipulator, this tip can be advanced into different layers of plant tissues to measure photosynthesis gradients. Similarly, light attenuation within a sample can be assessed using a pointed working fiber.