As our lab explores ways of tracking the physiology of pollination, we have gotten interested in whether there is a visual way of tracking fertilization with our blue pollen tubes (Lat52:GUS containing pollen). Mark Johnson at Brown University, who initially showed us how to best visualize our blue tubes, mentioned that you can see ovule fertilization as a blue dot on the ovule. When a blue-tube reaches an ovule, the tube degenerates to release the two sperm cells that will double-fertilize the ovule. When that happens, the enzymes in the pollen tube that produce the blue color are released onto the ovule. You can see some of these dots marked with black arrows, below.