The Contribution of Foliar Exposure to Boron Toxicity

ABSTRACT

Boron toxicity is commonly considered in terms of plant B uptake and accumulation. This work tested the hypothesis that foliar exposure of water with high B content leads to more severe toxicity reactions in plants as compared to exposure to high B simply through the soil solution. Growth and B uptake were studied in corn, tomatoes, onions, celery and radish where B laden water was applied with and without a component of foliar contact. Increased visual symptoms of B toxicity and decreased yields were found in plants with foliar applied B for all of the crops, while associated increased B tissue concentrations were not measured. The results imply that the relative toxicity of B entering through the leaves is greater than that of B entering via roots. Biomass reduction due to B was found to be a function of neither absolute B accumulation nor relative B mobility in the plant.

Keywords:

• boron
• toxicity
• foliar contact
• accumulation
• growth

ACKNOWLEDGEMENT

This work was made possible through support provided by The Middle East Regional Cooperation Program, US Agency for International Development, Grant M24-014 and the Mevuot HaNegev High School teaching greenhouse. Grateful thanks to Yusuf Eldenfiri and Inna Feingold for technical support.