PHYTOTOXICITY OF HYDROGEN-FLUORIDE AND FLUOROBORATE AND THEIR UPTAKE FROM SOLUTION CULTURE BY LYCOPERSICON-ESCULENTUM AND AVENA-SATIVA

The aims of this paper were to determine the phytoavailability and phy totoxicity of hydrogen fluoride (HF) and fluoroborate (BF4-) in soluti on when exposed to the root of the plant. As fluoroborate undergoes a slow hydrolysis to F and berate ions, the stability of BF4- under solu tion culture conditions was determined. Fluoroborate was found to have a zero order rate constant of 0.0136 and took approximately 72 days t o hydrolyse completely. Tomato (Lycopersicon esculentum) and oat (Aven a sativa) plants were grown in dilute nutrient solutions which contain ed a range of activities of HF and BF4-. Dry matter production of both tomato and oat plants grown in nutrient solutions were found to be re stricted by increased activity of HF and BF4- in solution. Tomatoes we re more sensitive to HF and BF4- than oats. Limitations to dry matter production coincided with increased uptake of F for F concentrations i n tissue of both tomatoes and oats. Fluoride uptake of both HF and BF by tomatoes and oats was orders of magnitude higher compared to simila r activities of other ionic species of F reported in previous studies. Possible mechanisms of uptake are discussed.