| چکیده انگلیسی مقاله |
Background: Elicitors play an important role in the supply and absorption of nutrients in plants. Also, they are able to improve growth and increase the quantity and quality of the product through making changes in the main and systemic processes of plants. Biological applications of nanoparticles and polyamines and using them as plant growth regulators and elicitors is a promising tool for realizing sustainable agriculture. Nanoparticles and polyamines may differentially affect plants depends on plant species, concentrations and application methods. Among the different nanoparticles, titanium dioxide (NiO2) can improve the efficiency of photosynthetic apparatus and increase the plant’s ability to absorb sunlight, which in this way affects the conversion of the solar energy into active electrons and chemical activities and increases the photosynthesis efficiency in plant. Putrescine polyamine is also effective on more physiological processes such as seed germination, fruit and flower growth, delaying senescence, and plant responses to environmental stresses. But so far, there are no enough researches about the effect of titanium nanoparticles and putrescine on the morphological, physiological and biochemical processes of plants especially in Rosmary (Rosmarinus officinalis L.). Rosemary oil is one of herbal medicines which its antioxidant and antibacterial properties have been proved.
Methods: In order to investigate the effectiveness of different levels of NiO2 nanoparticles (0, 50, 100, 200 and 400 ppm) and putrescine (0, 0.5, 1 and 1.5 mM) on the growth, physiological and biochemical traits of Rosmarinus officinalis L., an experiment was implemented as factorial in the form of a completely randomized design with three replications in the research greenhouse of the Sana institute of higher education. The plants were sprayed once a week and after eight weeks, growth traits (plant height, number of leaves, fresh weight and dry weight of aerial parts, fresh weight and dry weight of root), physiological traits (the content of chlorophyll a, chlorophyll b, total chlorophyll, carotenoid) and biochemical (activities of antioxidant enzymes including peroxidase and catalase, and percentage of free radical scavenging) were measured in the leaves of seedlings. Before performing the analysis, the normality of data distribution and the homogeneity of variance of experimental errors were checked using the least significant difference (LSD) test, and the means were compared with Duncan’s multi-tailed test at the 5% probability level.
Results: Scanning Electron Microscopy (SEM) confirmed the adsorption and translocation of titanium nanoparticles through plant upon experimental treatments. Analysis of variance of simple effect of titanium dioxide nanoparticle and simple effect of putrescine on all growth traits, amounts of chlorophyll pigments, phenol and DPPH of R. officinalis was significant (p<0.01). However, the analysis of variance of the interaction effect of these two treatments on the number of leaves and fresh and dry weight of aerial parts (p<0.01), fresh weight of root, amount of total chlorophyll and flavonoid of R. officinalis (p<0.05) was reported to be significant. The mean comparison of treatments showed that the different concentrations of titanium dioxide nanoparticles and putrescine caused an increase in all the growth traits, the content of chlorophyll pigments and the biochemical characteristics of R. officinalis. The highest mean growth traits of R. officinalis were obtained at the concentration of 200 ppm nanoparticle and 1 mM putrescine, the maximum content of chlorophyll and carotenoid were also obtained at the concentrations of 200 and 400 ppm nanoparticles and levels of 1 mM and 1.5 mM putrescine. Also, the biochemical traits of R. officinalis under the highest concentration of nanoparticles and putrescine had the highest mean. In fact, the treatments used increase the production of dry matter and increase photosynthesis, which increase the performance of the plant and its components. Titanium nanoparticles can increase fresh and dry weight of plants by improving light absorption, increasing nitrate absorption and converting inorganic materials into organic materials. By increasing light absorption, oxidation and reduction reactions are stimulated in plants, after which the photosynthetic capacity of the plant increases and chloroplast aging is prevented. Also, since titanium dioxide nanoparticles lead to more protein absorption, the synthesis of chlorophyll in the plant increases in this way. The role of putrescine in increasing plant growth is probably due to its antioxidant effect, helping to balance cation and anion, or acting as a nitrogen source. Also, due to the fact that ethylene and polyamines have a common precursor for synthesis, as polyamines are made in the plant, the production of ethylene decreases, and as the amount of ethylene decreases, the degradation of photosynthetic pigments also decreases. In addition, with the use of putrescine, the number of polyamines in the terminal meristem of the plant increases and as a result the growth of the plant increases. Polyamines start a chain of defense reactions, one of the results of which is the increase in the activity of antioxidant enzymes.
Conclusion: According to the obtained results in this study, NiO2 nanoparticles at 200 and 400 ppm and putrescine at 1 mM and 1.5 mM concentrations through foliar application showed strong effect on improvement of growth traits, antioxidant enzymes and the content of photosynthetic pigments in R. officinalis. Therefore, the use of appropriate concentration of NiO2 nanoparticles and putrescine seemed to be effective in increasing the content of active secondary metabolites in rosemary. Also, it is suggested to study the effect of these treatments for longer experimental periods or on some more species that could be a suitable way to find better and more reasonable results. |