Effect of nitrogen and potassium supply on concentration of iron and manganese and activities of catalase, peroxidase and aconitase in pepper plants

Pepper plants (Capsicum annuum L. cv. Lamuyo) grown in soil filled pots wer e fertilized with 4 levels of NH4NO3 (6, 12, 18 and 24 g/pot) and 3 levels of K2SO4 (4, 8 and 12 g/pot). The lowest concentrations (N-1 and K-1) were selected as controls. The foliar levels of Fe and Mn, both total and extrac table, were measured, together with the activities of catalase, peroxidase and aconitase. The N and K treatments affected the Fe and Mn nutritional st atus of the leaves. The effects on the catalase and peroxidase activity sho wed an Fe-Mn interaction more clearly than the concentrations of Fe and Mn in leaves. In the present experiment aconitase activity did not prove to be a good indicator for the Fe nutritional status of plants.