Effect of Salt Stress on the Salicylic Acid Synthesis in Young Maize (Zea mays L.) Plants

The effect of salt stress on salicylic acid (SA) synthesis was investigated parallel with the induction of antioxidant enzymes in young maize plants. Two-week-old maize plants grown in hydroponic solution were treated with 50 or 100 mm NaCl for 7 days. Antioxidant enzyme activities, and the SA and o-hydroxy-cinnamic acid (oHCA) levels were measured on the 3rd and 7th day of treatment and after 4 days of recovery. Ascorbate peroxidase activity increased in the leaves, but changes in guaiacol peroxidase activity only could be detected in the roots after 7 days. Glutathione reductase activity increased both in the leaves and in the roots after the 3rd day of 100 mm NaCl treatment. Free SA only increased during recovery in the leaves and roots. In the leaves of plants treated with 100 mm NaCl, a slight increase was observed in the free oHCA level, which rose dramatically after recovery, while in the roots an increase could only be seen after recovery. These results suggest that oHCA may serve not only as a precursor of SA but may also have an antioxidant role during salt stress and recovery.