Interactive Effect of Silicon (Si) and Salicylic Acid (SA) in Maize Seedlings and Their Mechanisms of Cadmium (Cd) Toxicity Alleviation

The present study has been conducted to evaluate the impact of silicon (Si) and salicylic acid (SA) in the regulation of Cd-induced toxicity in maize seedlings. Cadmium (Cd: 100 mu M) significantly reduced root and shoot fresh weight and length, photosynthetic pigments, total soluble protein content and chlorophyll fluorescence parameters. Cadmium decreased root and shoot length by 23 and 19% and fresh weight by 27 and 24%, respectively when compared to their respective controls. Similarly, total chlorophyll, carotenoids and total soluble protein were decreased by 21, 18 and 28%, respectively by Cd. In contrast, the addition of SA (500 mu M) and Si (10 mu M), and their combination (SA + Si) together with Cd treatment successfully ameliorated Cd-induced harmful impacts on studied parameters as SA and Si alone and in combination reduced Cd accumulation and oxidative stresses and thus refurbish the damages. Cd significantly stimulated activity of superoxide dismutase while inhibited activities of ascorbate peroxidase (APX), glutathione reductase (GR) and dehydroascorbate reductase (DHAR), and declined total ascorbate and glutathione contents. In contrast, the addition of SA and Si alone and in combination stimulated the activities of APX, GR and DHAR and significantly increased levels of total ascorbate and glutathione. In conclusion, the present study suggested that although SA and Si both alone are able to alleviate Cd-induced toxicity in maize seedlings, but their combination was the most effective in nullifying Cd-induced toxicity in maize seedlings.