Effect of priming and nano particles application on seedling emergence, establishment, growth and physiological characteristics of Sanguisorba minor Scop. and Agropyron intermedium (Host) P. Beauv forage species under drought stress in natural field

Background and objectives: Problems of germination and establishment of plants in drought and dehydration conditions is one of the common problems in arid and semi-arid regions of the country which affects the growth and production of plant communities. Improvement of seed germination and establishment of plants under drought stress is one of the most important issues in success of rehabilitation projects in natural areas. Range species of Sanguisorba minor and Agropyron intermedium are mainly distributed in semi-arid ad semi-humid climates. In this research, the possibility of germination and establishment of these species were investigated under different priming treatments in an arid region. Methodology: In this study, the effects of different priming included distilled water, polyethylene glycol (0.1 Mega-Pascal), potassium nitrate (0.2%) and silver nanoparticles (at three levels of 30, 60 and 90 mg/l) were investigated for improvement of seed germination characteristic and plant establishment under irrigation regime of field capacity and drought stress under field natural condition. The experiment was performed as a factorial in a randomized complete block design with 4 replications and in total 56 plots was considered for each species. The dimensions of each construction plot were equal to 1.5 square meters and in each plot, three planting rows with a distance of 30 cm and a length of one meter were considered and 45 seeds were planted in each experimental plot. The measured traits were included the percentage and velocity of appearance of seedlings from the soil, establishment and survival, length and weight of root and stem, vigority, prolin, carotenoid, soluble sugar,  total chlorophyll, catalase and superoxide dismutase enzymes. After sampling the studied traits in the field and obtaining the results obtained in the laboratory, analysis of variance and analysis of data in SPSS software and comparison of mean data with Duncan's multiple range tests at 5% level for the studied traits were performed in both species. Results: Statistical analysis of the results showed that the application of priming has been more effective on soil appearance percentage, appearance rate and establishment and survival of seedlings, but it has also affected other studied traits. Application of silver nanoparticles had positive or negative effects on the vegetative characteristics of seeds and seedlings grown from the seeds of the studied plants. Application of polyethylene glycol and potassium nitrate in A. intermedium and application of polyethylene glycol and silver nanoparticles with concentration of 30 mg/l in S. minor showed the highest positive effects on plant resistance under drought stress. Application of silver nanoparticle at concentrations of 60 and 90 mg/L showed negative effects on the vegetative and physiological characteristics of two studied species as well. Increase of 25% and 13% in biomass production under the treatment of silver nanoparticles with a concentration of 30 mg/l and decrease of 12% and 3% in the biomass under the treatment of silver nanoparticles at a concentration of 90 mg/l, respectively were observed for A. intermedium and S. minor species. Conclusion: Increasing the rate of water absorption and metabolism in primed seeds leads to more germination, reduces the natural and inherent physiological non-uniformity of buds and increases drought tolerance and plant yield. The positive effect of silver nanoparticles is mainly due to facilitating the penetration of water and nutrients into plant seeds and improving germination properties.Using the results of this research can increase the success rate in the cultivation and establishment of S. minor and A. intermedium range species in arid and semi-arid rangelands and increase the efficiency of biological projects for rangelands improvement and rehabilitation.