There is an interesting article about this with the title "Effects of Manganese Nanoparticle Exposure on Nutrient Acquisition in Wheat (Triticum aestivum L.)" . You can view and download this article via the following link:
See attached. As stated in the attached article 'In plants, Mn is one of the 17 essential elements for growth and reproduction'. Google (Scholar) is your friend.
Anything 'nano' will typically dissolve quicker, react quicker, and therefore directly affect bioavailability and toxicity. The size may also decide the ultimate fate of the nanomaterial in the environment.