Pollen in unopened flowers of most species is totally screened from solar ultraviolet‐B radiation by imbricated petals that are largely opaque to UV‐B. Following flower opening but before anther dehiscence, the anther walls of the species investigated filter out over 98% of the UV‐B radiation. Reflectance of UV from corollas of open flowers does not generally appear to add significantly to the solar UV‐B radiation environment of pollen.
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Flint et al. (1983) studied this question.