PHYTOTOXICITY OF THE FLUORIDE-ION AND ITS UPTAKE FROM SOLUTION CULTURE BY AVENA-SATIVA AND LYCOPERSICON-ESCULENTUM

Avena sativa (oats) and Lycopersicon esculentum (tomatoes) were grown in dilute nutrient solutions containing varying concentrations of fluo ride (F). Shoot and root growth of tomatoes were limited when calculat ed F ion activities (F-) were greater than 1473 mu M in solution. Howe ver, F- activities up to 5130 mu m had no effect on the dry weights of oat shoots or roots, suggesting that tomatoes are more sensitive to F toxicity. At low F activities in solution (< 684 mu M) F concentratio ns in plant shoots increased almost linearly with activity, but then i ncreased rapidly before reaching an upper asymptote. These findings ar e discussed in relation to plant uptake and toxicity of F. The complex ation of Ca with F has been proposed as the mechanism of selectively a ltering membrane permeability to F, but further studies are required t o confirm the role of Ca. Data recalculated from the literature and fr om this paper also suggest that growth solution ionic strength is posi tively related to uptake of F- by plants.