Boron is an essential micronutrient for plants and is taken up in the form of boric acid (BA). Despite this, a high BA concentration is toxic for the plants, inhibiting root growth and is thus a significant problem in semi-arid areas in the world. In this work, we report the molecular basis for the inhibition of root growth caused by boron. We used microarrays to detail the global gene expression underlying boron toxicity in roots. Overall design: 5-day-old arabidopsis plants were transferred to medium with high boron concentration (½ MS medium supplemented with 5mM BA) and control conditions (½ MS medium). We determined that 5 mM BA is the minimum concentration that produces the maximum effect, stunting root growth by ~50% after 5 days as compared with control conditions. We analyzed the transcript profiles in roots by microarray analysis (Affymetrix ATH1 Genome Array). We compared the transcripts obtained at 12 hrs of BA treatment.