There is also a study from 2014 that suggests that prions were not detected in stems even though the roots of wheat plants were exposed to them. I don't know if there is conclusive evidence yet on getting sick by eating a plant based diet.

"This suggests wheat was unable to transport sufficient PrP(TSE) from the roots to the stem to be detectable by the methods employed."

Source: https://pubmed.ncbi.nlm.nih.gov/24509640/