The effect of zinc on the growth and physiological and biochemical parameters in seedlings of Eruca sativa (L.) (Rocket)

Eruca sativa seedlings were treated with different Zn concentrations (0, 250, 500, 1,000, 2,000 µg g⁻¹ dried growth medium) under controlled conditions. The seedlings were harvested 20 days after Zn treatment. Physiological parameters, such as root and shoot length, fresh and dry weight, were measured and Zn content of roots and shoots was determined. Furthermore, various biochemical parameters were studied on E. sativa leaves: enzymatic antioxidants, such as superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (POD), ascorbate peroxidase (APX), and non-enzymatic antioxidants, such as ascorbate, non-protein thiols. Malondialdehyde, which is an index of lipid peroxidation, was assayed. Zn treatment did not have any significant effect on fresh and dry weights, whereas 500 µg g⁻¹ Zn increased root growth significantly (p<0.05). Zn accumulated in roots 2–8 times more than it did in leaves. Lipid peroxidation increased in proportion with the increase in Zn. Although a decrease in SOD and CAT activities at increased Zn was found, a significant increase in APX and POD was observed at 500 and 1,000 µg g⁻¹ Zn, respectively. In addition, an increase in the amounts of non-protein thiols and total AsA (Ascorbate) was observed with the increase in Zn.