A few years ago, it became possible to watch fertilization in flowering plants live with a microscope (for most recent examples, see Hamamura et al., 2014; Kawa-shima et al., 2014). The process is more complicated, of course, than in animals. Two sperm are carried inside the fast-moving pollen tube to the center of the future seed. Once there, one sperm fuses with the egg to create the zygote, whereas the other fuses with the central cell to generate the endosperm. Making this double fertilization happen on a microscope stage turned out to be a very difficult trick, and success rates remain low even today. However, live imaging immediately clarified the timing of events and helped answer a number of long-standing questions (reviewed in Kurihara et al., 2013). For example, are the two sperm equivalent? Selectively labeling one of the sperm by photo-conversion reveals that yes, they are.
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