Why do land plants need small amounts of boron?

Boron is classified as a microelement, meaning it is an essential nutrient required by land plants in small quantities (typically 0.01 percent or less) to complete their life cycle.1

While the precise biochemical role of boron in plant life is not yet fully understood, most researchers agree that it is essential for the normal growth and functioning of apical meristems, which are the growing tips of plant shoots. A deficiency in boron often leads to stunted or misshapen growth, as well as specific disorders such as vegetable "brown heart" and "dry rot" in sugar beets.2

Because boron is necessary for the healthy development of these plants, it is considered indirectly essential for animal life as well. When applied to soil in the form of soluble borates, it can alleviate deficiency, though it must be used carefully, as excess quantities can act as unselective herbicides.2