Visible injury and growth responses of tomato and soybean to combinations of nickel,copper and ozone

Tomato (Lycopersicon esculentum Mill.) plants were grown in silica sand in controlled environments. In the first experiment Ni was added as NiSO₄ · 6 H₂O to the nutrient solution at 0, 1.5, 7.5, or 37.5 mg L^?1 for 6 day beginning 14 day from seeding, them plants were exposed to 0, 0.15, or 0.30 μL L^?1 O₃, and harvested 3 day later. Visible symptoms of Ni injury developed rapidly and there was distinctive O₃ injury. Growth variables were markedly reduced by Ni but O₃ response depended on Ni level. In the second experiment 0, 0.3, or 1.5 mg L^?1 Ni was provided from the 5th or 14th day onward. There was little effect of duration of Ni treatment on growth. Increasing Ni and increasing O₃ decreased growth but there was no interaction. In the third experiment 0, 1.5, and 3.0 mg L^?1 Ni treatments were combined with 0, 3.0, and 6.0 mg L^?1 Cu prior to 0 or 0.25 μL L^?1 O₃ treatment. There were complex interactive effects of all three factors on plant growth. Soybean (Glycine max Merr.) plants exposed to Ni and O₃ were only slightly affected by Ni or O₃ and there was no interaction.