Following up this article..Double-headed flowers
From 1987 to 2003, it has been experimented to cause plants mutation by radiation at Okinawa Prefectural Agricultural Research Center.
The purpose was to produce new kinds of rose (Samantha) for the market demand.
The result shows 52mSv/h caused triple-headed rose.
The rose was irradiated for 16 months per generation. Because this is not to know the lowest dose to cause variety of mutation, the sensitivity of rose is not known.
Also, the effect of internal exposure of plants is not known either.
The experiment took several generations to make the mutated features appear stably.
Iori Mochizuki