For the past two years we have been working hard on realizing an idea we had almost 10 years ago: Can we control photosynthesis of plants by measuring how quickly they photosynthesize and then adjust the light level in order to reach a specific rate. Turns out that the answer is: Yes, we can!
Using chlorophyll fluorescence measurements, we can measure how efficiently the plants are using the light they get. Combining that information with light measurements allows us the calculate the rate of the light reactions of photosynthesis (or more specifically the electron transport rate through photosystem II). We use a datalogger to automatically collect these data. The datalogger can then also adjust the amount of light provided by LED lights: if the electron transport rate is lower than desired, the light level is increased and vice versa. This can be used to build a fully automated biofeedback system that can be used to maintain a constant electron transport rate in the leaf. Our Biofeedback paper that describes this system and how plants respond to it was just published in the Journal of the American Society for Horticultural Science. You can also get more information on our webpage dedicated to this topic: http://hortphys.uga.edu/Biofeedback.html.