There aren't many natural sources of substantial radiation, unless you go digging up and concentrating the relevant elements or go far enough back in earth's history that plants hadn't been invented yet. There is virtually no call for the adaptation of radiation resistance, outside of a few man made regions.
However, as it happens, the biochemical adaptations required to survive severe dessication or extreme heat(which, like radiation, pretty much go all bull-in-a-china-shop on your genome and metabolically important molecules) happen to, in a number of cases, be pretty useful in radiation resistance as well. Bacteria like d. radiodurans, t. gammatolerans, and organisms like tardigrades are extremely radiation resistant; but as a side effect of their adaptations to heat and dessication.
Given the survival value, particularly for seeds, of being able to survive hard times and then germinate, or aggressively seize territory(and light) left open by forest fires, it wouldn't be a total surprise if plants had picked up a few adaptations in the same vein.
However, as it happens, the biochemical adaptations required to survive severe dessication or extreme heat(which, like radiation, pretty much go all bull-in-a-china-shop on your genome and metabolically important molecules) happen to, in a number of cases, be pretty useful in radiation resistance as well. Bacteria like d. radiodurans, t. gammatolerans, and organisms like tardigrades are extremely radiation resistant; but as a side effect of their adaptations to heat and dessication.
Given the survival value, particularly for seeds, of being able to survive hard times and then germinate, or aggressively seize territory(and light) left open by forest fires, it wouldn't be a total surprise if plants had picked up a few adaptations in the same vein.
