LAUSR

Plants use the enzymatic and non-enzymatic antioxidant defense mechanisms to avoid and/or tolerate environmental stresses. As a useful element in plants, silicon plays an important role in activating these defense systems and thus in improving plant resistance to environmental stresses. The present research studied the effect of silicon on important antioxidants including Super Oxide Dismutase (SOD) and Catalase (CAT) and also on glucomannan, mannose, and aloin in Aloe vera. 60 Aloe vera plant of Aloe barbadensis Mill variety were taken. After applying the fertilizer treatments during cold stress treatment, 30 pots were placed at 25 °C (control) and 30 pots at 4 °C (stress), and then fertilizer sidetreatments were applied. During their growth, the plants were treated with various silicon concentrations (500, 1000, 1500, and 2000 mg/l). Ninety days after they were planted, 30 of the plants were separated and exposed to cold stress at 4 °C for seven days. After applying the cold stress treatment, leaf samples were taken and analyzed simultaneously from treated and untreated plants. Results of ANOVA showed that cold stress and silicon treatments had significant effects on SOD, CAT, glucomannan, mannose, and aloin. Application of cold stress increased SOD and CAT activities and reduced glucomannan, mannose, and aloin concentrations. Increases in silicon concentration improved both enzymatic antioxidant activity and concentrations of soluble sugars and of aloin in Aloe vera. These results indicate that silicon plays a key role in enhancing plant defense systems against cold stress. Therefore, application of silicon fertilizers is of great importance in reducing losses caused by climatic stresses and in achieving the goals of sustainable agriculture.