تأثیر نانوسلنیوم و سلنات‌سدیم بر واکنش‌های رشدی و بیوشیمیایی گیاه اسفناج (Spinacia oleracea L.) رقم ویروفلای در شرایط گلخانه

Introduction

Selenium is one of the essential food elements for humans and animals. Seleno-proteins participate in antioxidant defense systems and regulation of oxidation in mammals, and their deficiency leads to immune system dysfunction. Selenium concentration in soils has been declared insufficient and as a result, according to estimates, 15-20% of children and adults in the world suffer from selenium deficiency. Plants, as the best source of selenium for humans and animals, absorb the element from the soil and enter the food chain. Nanotechnology is a promising field of bioengineering. Selenium nanoparticles have been introduced as stable nanoparticles as fertilizers in agriculture. Foliar spraying of plants with nano-selenium has been associated with the improvement of antioxidant defense mechanisms, photosynthetic indices and secondary metabolites.

Spinach, an annual and long-day plant, is one of the important leafy vegetables of the cold season. Fresh spinach contains sugars, lecithin, secretin, chlorophyll, carotene, saponins, phenolic compounds, caffeic acid, ortho-coumaric acid, para-coumaric acid, myristicin and oxalates. Since selenium is one of the useful elements in plants (including spinach) and due to the toxic effects of this element in high concentrations, in this research, the effects of selenium (in both bulk and nano forms) were considered on spinach plants. The aim of this research is to compare foliar spraying with nano-selenium (5, 10 and 20 ppm) and sodium selenate (5, 10 and 20 mg/liter) on growth (leaf and root dry matter, aerial and root length and number of leaves), physiological (ion leakage rate, proline content and malondialdehyde) and antioxidant parameters (phenol, flavonoid content, antioxidant activity and activity of catalase and peroxidase enzymes) in spinach.



Material and Methods

The experiment was carried out in a completely randomized design. The factors were included foliar spraying of nano selenium (5, 10 and 20 ppm), sodium selenate (5, 10 and 20 mg/L) and distilled water (control plants). Growth (leaf and root dry matter, shoot and root length, leaf number) and biochemical (Proline content, ion leakage, MDA, flavonoid and phenol contents, antioxidant, the activity of catalase and peroxidase enzymes) traits were investigated at the end of the experiment. The normality of the data was determined by the Shapiro-Wilk method. Tukey's test was performed to compare the mean (P < 0.01, 0.05). Statistical analysis of data was done with SAS Ver.9.4 software. Also, the pictures were drawn with the help of EXCEL 2016 program.

Results

Based on findings, increasing the levels of both treatments (up to 20 ppm and mg/L) led to enhanced root dry matter, shoot length, leaf number, proline, flavonoid, antioxidant activity, CAT and POX activities, and decreased ion leakage and MDA. Therefore, the lowest MDA and ion leakage was obtained at 20 ppm nano-Se. Despite the enhancement in leaf dry matter, root length and phenol at low levels of nano-Se (5 and 10 ppm), a decline in the mentioned traits was observed via increasing levels of this treatment. The highest leaf dry matter and antioxidant activity was observed at 10 ppm n of nano-Se. Moreover, at 20 ppm nano-Se, the highest shoot length, proline content and peroxidase activity was obtained. However, the highest CAT activity was observed under 10 mg/L sodium selenate. In addition, under different levels of sodium selenate, a similar trend was observed in leaf dry matter and phenol content. As the highest amount of phenol and flavonoid contents was recorded at 5 mg/L sodium selenate. Boosting in sodium selenate levels (up to 20 mg/L) also caused a decrease in root length. Thus, the highest root length was recorded at 5 ppm of nano-Se.

Conclusion

Data obtained from the impact of various selenium compounds on spinach Virofly variety in this research, indicated that high levels of selenium in nano form had an increasing effect on shoot and root length, proline content and POX activity, and in the form of sodium selenate on root dry matter and leaf number. Nevertheless, the highest level of nano-Se showed a reducing effect on MDA. In addition, data illustrated the enhancing effects of medium levels of nano-Se on root length and antioxidant activity, and sodium selenate on flavonoid, phenol and CAT activity. But, the reduction of ion leakage occurred at the lowest level of sodium selenate. This difference in the effect of various levels of treatments on the studied traits shows that each trait appears optimally under certain levels of treatments. Therefore, the importance of selenium compounds (bulk or nano) dosage is highlighted in research activities.