Although an important element for plants, excess boron can result in boron toxicity. So, we need to know about the visible symptoms and misconceptions about boron toxicity:
For a wide variety of plant species, the typical visible symptom of boron toxicity is leaf burn, often at the margins and tips of older leaves. These symptoms reflect the distribution of boron in most species, with Boron accumulating at the end of the transpiration stream
Contrary to the general perception, leaf burn is not the visible symptom of boron toxicity in all species. In some species, the symptoms of toxicity are fruit disorders (gummy nuts, internal necrosis), bark necrosis etc.
Visible symptoms of boron toxicity do not appear to develop in roots. As boron concentrations in the roots remain relatively low compared to those in leaves, even at very high levels of Boron supply, toxic concentrations do not occur in root tissues.