Angiosperm pollen shed in the binucleate condition (which is the case for most species) may be more susceptible to UV radiation damage than pollen shed in the trinucleate condition. The speculation is supported by data summarized from the literature which show that trinucleate pollen is more physiologically advanced at the time when it is shed from the anther. The time course of germination, penetration of the stigma, and successful fertilization is thus more rapid in these trinucleate species. The results in less exposure to solar ultraviolet and consequently less damage should be expected. Experiments are needed to test the sensitivity of these pollen types in vivo and to evaluate the efficacy of possible repair mechanisms.