Effect of Seed Pretreatment with Salicylic Acid on Seed Germination, Growth and Biochemical Indices of Quinoa Seedlings (Chenopodium quinoa willd.) under Cadmium Stress

To investigate the effect of salicylic acid on the indicators of seed germination and growth of quinoa seedlings under cadmium stress, a factorial experiment was conducted in the form of a completely randomized basic design in four replications at Mohaghegh Ardabili University. The treatments included cadmium stress at five levels (0, 50, 100, 150, and 200 mg/l), and salicylic acid at five levels (0, 1, 1.5, 2, and 2.5 mM). The results showed that with the increase in stress intensity, the average percentage and speed of germination, dry weight, and length of quinoa seedlings decreased. In non-stressed conditions, the percentage and speed of germination and the dry weight of the seedlings obtained from the seeds pretreated with salicylic acid were significantly higher than the control seeds. Also, seed pretreatment with salicylic acid significantly increased the characteristics of germination percentage, germination rate, average germination percentage, seedling length, dry weight, activity of catalase, peroxidase, and polyphenol oxidase enzymes, but decreased the average germination time, time to 90% germination. Application of 2.5 mM salicylic acid as a pre-treatment in non-stress and cadmium stress conditions increased seedling length by 46.48 and 73.83%. By using 2.5 mM concentration of salicylic acid, the activity of catalase, peroxidase, and polyphenol oxidase enzymes increased by 45.30 to 93.89, 22.51 to 51.6, and 25.4 to 45.17%, respectively. In total, seed pretreatment with 2.5 mM salicylic acid, at different levels of cadmium stress, increased seed and seedling vigor and activity. Antioxidant enzymes had the most positive effect on the germination and growth of quinoa seedlings.