Iranian Journal of Seed Research

The purpose of this study was to evaluate the effect of Nano TiO₂ and Nano CNT on some germination indices and growth parameters of some hulled barley cultivars. The experiment was conducted in a laboratory at Shahrekord University during 2014. The study was a factorial, adopting a completely randomized design with four replications. Treatments consisted of titanium dioxide nanoparticles and carbon nanotube (CNT) in four concentrations (0, 10, 30 and 60 mg.l^-1) which were applied to seeds of hulled barley cultivars such as Bahman, Makoii and Nosrat. The traits measured were the dry weight of seedling and seedling length, germination percentage, germination rate, mean germination time, the percentage of resistance of radical, seedling vigor length and weight index. The results showed that carbon nanotubes treatments with 60 mg.l^-1 had a significant impact on germination percentage, germination rate, seedling vigor length and weight index and seedling dry weight, as compared with other treatments. In this experiment, the highest percentages of resistance of radicle, seedling vigor weight index and seedling dry weight of Nosrat Cultivar were obtained under 60 mg.l^-1 carbon nanotube treatment, which was 70, 122.2 and 64.9%, respectively, as compared with control treatment. In addition, 60 mg.l^-1 carbon nanotube treatment increased the seedling vigor of Makoii cultivar by 39.8%, as compared with the control treatment. The findings were that in terms of seedling vigor length and weight index, seedling length, seedling dry weight and the percentage of resistance of radical, the Nosrat Cultivar showed better morphological characteristics than Bahman and Makoii cultivars, under laboratory conditions.
 

Extended Abstract
Introduction: Salinity is one of the most serious abiotic stresses, causing instability in germination and seed emergence due to low osmotic potential and ionic toxicity. Development of simple and low-cost biologic methods is essential for short-term management of salt stress. The use of plant growth-promoting rhizobacteria increases the rate and uniformity of germination. This research aimed to investigate the effect of bacterial growth-promoting bacteria on the germination and seedling growth indices of alfalfa c.v. Hamedani in different salinity levels.
Materials and Methods: A CRD factorial experiment with four replications was conducted in Seed Science and Technology Laboratory of Shahrekord University in 2016. The first factor consisted of 6 salinity levels 0, 2.5, 5, 7.5, 10 and 12.5 dS/m created with sodium chloride, and the second was four levels of bacterial pre-treatment: no inoculation with bacteria and biopriming, inoculation of alfalfa seeds with Acinetrobacter calcoaceticus PTCC 1318, Bacillus megaterium PTCC 1250 and Enterobacter aerogenes PTCC 1221. The seeds were treated with bacteria and placed at a 20 °C growth chamber. They were then irrigated with desired solutions depending on the salinity treatment. Germinated seeds were counted daily and the parameters of germination percentage and rate, seedling length, seedling dry weight, vigour index I, II and allometric coefficient were calculated after 10 days.
Results: Salinity levels higher than 10 dS/m reduced germination indices and seedling growth of alfalfa. The highest reductions were obtained for 12.5 ds/m salinity level versus control for germination percentage (10.81%), germination rate (49.48%), plumule and radicle length (13.30% and 28.88% respectively) and vigor index I and II, which were 30.27% and 6.28%, respectively. The seed treated with A. calcoaceticus was able to tolerate salinity stresses more than others. For example, the reduction for the seed treated with A. calcoaceticus was only 4%, compared with non-stressed control. In salinity conditions 2.5 and 5 dS/m, the highest rate of germination was obtained, using A. calcoaceticus bacteria. In addition, the seeds treated with E. aerogenes showed higher stability at different levels of salinity for seedling length traits. The highest vigour index related to the use of A. calcoaceticus in salinity was 7.5 ds/m.
Conclusions: A. calcoaceticus had a significant role in reducing the negative effects of salinity on germination percentage and rate, vigour index I and II and allometric coefficient while E. aerogenes bacteria were more effective in reducing negative effects of salinity on seedling length and dry weight.
 
 
Highlights:

1. Acinetrobacter calcoaceticus bacterium increased the percentage and rate of germination of alfalfa seeds under salt stress.
2. Enterobacter aerogenes bacteria efficiently adjusted the negative effects of salinity on alfalfa seedlings length and dry weight.