Influence of titanium dioxide nanoparticles on growth characteristic and nutrient uptake of marigold under NaCl stress

Introduction:

 Titanium dioxide nanoparticles (TiO2NPs) generally have positive impacts on the growth, biochemical, and physiological characteristics of plants. Salinity is one of the major environmental factors that limited the growth and production of most crops due to the different plant species and growth stages. Based on severity and duration of the salinity stress different reactions of the plants were observed. Salinity reduces the growth of plants due to the existing osmotic materials around the roots. In addition, salinity exerts hypertonic stress on the plants. Under salinity, ions, mostly Na+ and Cl-, accumulate in the tissues of plants and cause significant physiological disorders and reduction in plant growth and development. Therefore, using different methods for reducing the harmful effects of salinity is very important. Various ameliorating agents such as nanoparticles (NPs) have been used for combating various abiotic stresses like salinity. Application of NPs to stressed plants have been shown to mitigate stress-induced oxidative and osmotic stress. Calendula officinalis L. (marigold) is an annual ornamental and medicinal plant from Asteraceae family that widely cultivated for different purposes like producing industrial products in culinary, pharmaceutical, and cosmetics industries.

Materials and Methods:

 This study aimed to evaluate the effects of TiO2NPs on biochemical and physiological parameters of marigold (Calendula officinalis L.) under NaCl stress. Treatments included TiO2NPs applied as foliar spraying in three levels (50, 100, and 200 mg/L), no foliar application as control, and different NaCl levels (0, 30, 60, and 90 mM) by adding NaCl into irrigation water.The studied traits were included growth characteristic (height, number of brunches, Number of flowering branch Number of flowers, Flower diameter, Total flower fresh weight, Total flower dry weight, Flower yield, Leaf area , Plant fresh and dry weight, Root fresh and dry weight, Root length and volume)) and element content (N, P, K, Fe, Mn,Mg,Ca, Zn, Na, Ti). Statistical analysis was performed using JAMP 13software. The mean comparison was done by LSD test at the 5% probability level.

Results and Discussion:

 The results of the mean comparison showed that, with increasing salinity, the growth characteristics of the plant decreased and the application of titanium dioxide nanoparticles, especially in 200 mg/L level, improved these traits. In addition salinity affected the nutrient uptake of the plant. Application of titanium dioxide nanoparticles improved the nutrient uptake of marigold under NaCl stress. According to the findings of this study, titanium dioxide nanoparticles mitigate the detrimental effects of salinity on the studied traits which were decreased under different NaCl concentrations.Among different titanium dioxide nanoparticles levels that used in this study, 200 mg/L is more effective than the other concentrations.

Conclusions:

 Based on the results of this experiment, the stimulatory effect of foliar application of TiO2NPs under NaCl stress on enhancing growth characteristics and nutrient uptake of marigold were observed in this study. At the higher NaCl levels, the negative effects of NaCl on plant growth and osmotic abilities were observed. The application of titanium dioxide nanoparticles had different effects on the studied traits. TiO2NPs application increased the studied parameters under salinity stress in comparison with no application of TiO2. In most cases, 200 mg/L titanium dioxide was the most effective concentration to mitigate the negative effects of salinity.In addition, TiO2 helped the plants to resist NaCl stress and mitigate the harmful effects of salinity.On the other hand, proper osmoprotectants and antioxidants may induce the synthesis and accumulation of bioactive naturally compounds. Based on the findings of this study, it is concluded that foliar application of TiO2NPs under NaCl stress can alleviate the deleterious effects of salinity and also improve the growth of marigold by increasing the nutrient element content such as Fe, Mg and N that effective in chlorophyll synthesis.