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Boron, Calcium & Pollen: A Vitality Crisis!

December 2009 - Thomas E. Ferrari

Boron & Calcium analyses using soils or tissues DO NOT predict the reproductive needs of crops during bloom.

Root hairs obtain boron and calcium from soils, they are then transported through roots to stems, branches, shoots and finally to flowers. Eventually both elements reach pistils and anthers. Periodic leaf and soil analyses are routine cultural practices used by farm managers to monitor nutrients needed for vegetative stages of plant health and growth. "Vegetative" refers to leaves, stems, roots, ect. On the other hand, flowers are the "reproductive" apparatus of plants. The two phases are different concerning function and nutritional needs.

Healthy flowers promote pollen germination, tube growth, fertilization and early embryo growth. Boron and calcium are vital during these four reproductive processes. Responses of pollen to both elements fit a bell-shaped curve. Thus, a proper balance of boron and calcium is important to optimize a flower's fruitfulness. It is important to emphasize that "balance" is the key word: too much can be just as detrimental as too little. At excessive amounts, both boron and calcium become toxic and impair pollen performance. When deficient, many pollen tubes fail to reach the ovary and fertilization does not occur. Our research data showed that in a majority of cases, boron and calcium imbalances in flowers during bloom impair pollen vitality. It became obvious to us that protocols used for nutrient analyses during the vegetative phase, do not correlate with pollen vitality during the reproductive phase.

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