Boron deficiency symptoms:
Boron deficiency symptoms are related to its main role in plants, cell wall expansion and structure. Typical deficiency symptoms include: impaired cell expansion in rapidly growing organs (leaves, roots, pollen tube), impaired growth of the plant meristems in roots and shoots causing malformation and thick and shorter roots, flower abortion, male and female flowers sterility, and reduced seed set due to inhibition of pollen growth. Reproductive organs, which have a high concentration of pectins rich in B, are frequently most sensitive to B deficiency because of their high B demand. . These organs also have low transpiration rates which limit the movement of B to these tissues.
Leaf symptoms of B deficiency develop in young leaves of plants that cannot mobilize B. Under severe B deficiency, stunted growth and death of growing tissue commonly occur. Inhibition of root elongation, failure of flowers to set seeds and fruit abortion are also common effects of B deficiency. However, these negative effects may occur without any visible leaf symptoms of B deficiency. Additional characteristic symptoms of B deficiency include the internal breakdown of tissues, especially in root crops (e.g., sugarbeet, turnip, potatoes) and fruit cracking (e.g. apple)
The figure above demonstrates the effect of removing the micronutrient boron during growth of the popular horticultural plant Pelargonium (widely known as Geranium)