Nickel supplements improve growth when foliar urea is the sole nitrogen source for tomato

Concentrations of up to 1.0 micromolar NiCl2 in a nutrient solution improved growth of tomato (Lycopersicon esculentum Mill. 'T-5') seedlings that received foliar urea as their sole nitrogen source. Nickel in the nutrient solution decreased the amount of urea present in the shoots and increased the amount in the roots, although it had no significant effect upon leaf urease activity. These results indicate that (a) the presence of nickel in the nutrient solution improves growth of plants receiving foliar urea and (b) the effect of nickel was related more to increased urea translocation from shoot to root than to enhanced leaf urease activity