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Why is boron essential for the growth of many land plants?

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A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — boron group element Modern version of the periodic table of the elements (printable).

Boron is classified as an essential microelement for many land plants, meaning it is required in small concentrations (0.01 percent or less) for the plant to complete its life cycle.1

While the precise biological role of boron in plant life remains a subject of ongoing research, it is widely accepted that the element is essential for the normal growth and functioning of apical meristems, which are the growing tips of plant shoots.2

When plants experience a long-term deficiency of boron, they often exhibit stunted or misshapen growth. Specific disorders resulting from this deficiency include vegetable "brown heart" and "dry rot" in sugar beets. Conversely, while boron is necessary for growth, it is important to note that in excess quantities, borates can act as unselective herbicides, and some plants growing in naturally boron-rich soil have been observed to exhibit gigantism. Boron deficiency can typically be corrected by applying soluble borates to the soil.2