Response to comments by Vladimir Murashov

Abstract Dr. Murashov has emphasized the major objective of our paper, which shows that exposure of growing plant roots to nanoparticles of alumina may result in growth inhibition and that this effect appears to be related to surface characteristics of the particles. The paper indicates that the mechanism(s) by which the particles may induce growth inhibition needs further attention. We agree that it is premature to draw definitive conclusions about toxicity mechanisms.