Effect of Amino Acid and Zinc Application on Uptake and Transport of Zinc and Iron in Rapeseed in Nutrient Solution Culture

The role of amino acids on root uptake and root-to-shoot translocation of micronutrients is of great importance to improve plant nutrition management. In this nutrient solution culture experiment, the effect of application of 100μM tryptophan, arginine and histidine on the uptake and root-to-shoot translocation of zinc (Zn) and iron (Fe) in rapeseed with three Zn levels (0, 5 and 10μM as zinc sulfate) was investigated. The results showed at the 5μMZn, application of arginine and tryptophan significantly reduced the shoot dry weight compared to the amino acid-free, while at the 5μMZn, the use of histidine resulted in a significant increase in the plant shoot dry weight. The highest plant shoot Zn uptake was found at the 10μMZn plus histidine. Application of 10μMZn in the presence of arginine led to a significant increase of root Zn uptake as compared to the amino acid-free while no such effect was found in the presence of other amino acids. In the presence of amino acids, except arginine, increasing Zn concentration in the nutrient solution to 10μM resulted in lower shoot and root Fe uptake in comparison with amino acid-free. In contrast, at 10μMZn treatment, application of arginine enhanced plant shoot and root Fe uptake. The highest concentration of total amino acids in the plant shoots and roots was related to the free-Zn and free-amino acid treatment. Regardless of the type of amino acid used, the increase in Zn level up to 10μM increased the leaf activity of the catalase and ascorbate peroxidase.