In an experiment to support the development of the FLEX candidate Earth Explorer mission, the HyPlant instrument was used on an aircraft to detect vegetation under stress. The experiment involved rolling out two fields of turf and applying one with a common herbicide and leaving the other untreated. As the image shows, the treated field on the left glows red, emitting more fluorescence compared to the control field on the right, and, in fact, more than the surrounding vegetation.
In general florescence is an indicator of photosynthetic activity, but in this case the herbicide interrupted the plant power systems so that absorbed solar energy could not be used for photosynthesis. To get rid of this energy the plants emitted more fluorescence. By detecting these abnormal peaks of florescence from space, FLEX could offer early warning of stress in plants that may appear healthy to the eye.
Read article: Plant power from above