RESUMEN
The effect of zinc and iron withhold from the nutrient medium on the activities of aldolase, carbonic anhydrase and catalase enzymes was investigated using faba bean plants grown in nutrient solution [0.2 M strength]. A reduction in catalase activity was observed when iron alone or/and with zinc withhold from the growth medium. In the case of carbonic anhydrase, the absence of zinc and iron from the nutrient medium caused high depressive effect [91%] followed by the absence of zinc [75%] and iron [30%]. Aldolase activity showed no response to both elements. The results showed that the aldolase activity after the first spray [20 days after sowing] was increased with more zinc and less iron applied concentrations. The maximum aldolase activity was reached when plants were sprayed with 100 ppm zinc and 50 ppm iron. It was noted that the different successive levels of zinc or iron alone did not show any promotive effect on the activity of aldolase or carbonic anhydrase enzymes