Submitted to: Plant and Soil Proceedings
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/1996
Publication Date: N/A
Interpretive Summary: We have been developing the analytical techniques for using the stable isotopes of boron to study the importance of boron in human nutrition. We have turned to plants to develop these analytical methods because of the essentiallity of boron in plant nutrition and the higher plant tissue concentrations. Until recently, it was believed that once a plant absorbed boron, the mineral was fixed in the plant and could not be moved to other parts of the plant. While boron is typically provided to plants as a soil fertilizer, research has recently demonstrated that boron applied to plant foliage can also be moved to other parts of the plants. We have demonstrated that when boron is applied to broccoli leaves it can be transported to the edible part of the broccoli head, and for boron deficient plants this can increase the yield by 75%. It is concluded that boron fertilization applied to plant leaves may be more effective for preventing boron deficiency than soil fertilization.
Technical Abstract: The translocation and effectiveness of foliar-fertilized boron (B) was investigated in broccoli plants supplied via the root system with luxuriant, sufficient or deficient amounts of B. 10B-enriched boric acid was applied three times to lower leaves, beginning one week prior to inflorescence emergence; the shoot and floret yields, as well as the 10B and 11B contents or concentrations of xylem sap, phloem exudate and various plant parts, were determined three weeks after inflorescence emergence. The amount of 10B translocated in phloem from fed leaves to the remainder of the shoot did not exceed 0.5% of that supplied, but was inversely related to plant-B status. The partitioning of translocated 10B to florets (16-30%) and the degree of enhancement in floret yields (28-75% also inversely related to plant-B status. Foliar-B fertilization may be more effective for preventing B deficiency than soil-derived B in leaves.