The impacts of different concentrations of bulk and nanosized TiO(2) on seed germination and seedling growth of wheat were studied in a randomized completely design with four replications in the College of Agriculture, Ferdowsi University of Mashhad, Iran, in 2011. The experimental treatments included five concentrations of bulk (1, 2, 10, 100, and 500 ppm), five concentrations of nanosized TiO(2) (1, 2, 10, 100, and 500 ppm), and control (without any TiO(2)). Results indicated that among the wheat germination indices, only mean germination time was affected by treatments. The lowest and the highest mean germination time (0.89 vs. 1.35 days) were obtained in 10 ppm concentration of nanosized TiO(2) and control treatments, respectively. In addition, shoot length, seedling length, and root dry matters were affected by bulk and nanosized TiO(2) concentrations, significantly. Shoot and seedling lengths at 2 and 10 ppm concentrations of nanosized TiO(2) were higher than those of the untreated control and bulk TiO(2) at 2 and 10 ppm concentrations. Employing nanosized TiO(2) in suitable concentration could promote the seed germination of wheat in comparison to bulk TiO(2) but in high concentrations had inhibitory or any effect on wheat.

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The effect of dilution on the composition of soil solutions of 8 contrasting soils ranging in pH from 5·3 to 8·8 with reference to zinc (Zn) and copper (Cu) was studied. Soil samples were equilibrated with water in various water:soil ratios for 24 h. Equilibrium solutions were extracted and analysed for dissolved organic carbon (DOC), and major and minor elements. The separation of the soil solution at field capacity (FC) was carried out by a drainage method. Although the concentration of ions decreased upon dilution, the total quantity of sodium (Na), potassium (K), Zn, Cu, and DOC extracted per unit of soil weight increased. In contrast, the total quantity of Ca and Mg decreased in most soils. The ratio of Zn and Cu to Ca correlated to dilution level, whereas the ratio of Zn to monovalent cations decreased in low pH soils. The relationship between the quantity of Zn and Cu at different levels of the water : soil ratio in the soils studied showed that the concentration of these trace metals at FC soil moisture can be estimated from the soil extract. Increases in soil moisture content led to a marked change in the ion-pair, free hydrated metal concentrations, and complexation. Log Zn2+ was linearly related to solution pH. Zinc solubility was not consistent with published solubilities of any common minerals. Also, Zn solubility in alkaline soils tended to be higher than reported values in the literature, indicating that soluble metal–organic ligand complexation was underestimated in these soils. The relationship between pH and log Zn2+ was affected by dilution in several ways.

Haloalkaliphilic bacteria have plant growth promoting characteristics that can be used to deal with different environmental stresses. To study the effect of haloalkaliphilic bacteria to reduce salinity and alkalinity stress in wheat, 48 isolates were isolated and grouped into halophiles, alkaliphiles and haloalkaliphiles based on growth characteristics. The ammonia, 3-indole acetic acid and ACC (1-aminocyclopropane-1-carboxylate) deaminase production were studied. Wheat yield was evaluated in the presence of six plant growth promoting activity superior isolates in the greenhouse condition. Definitive identification was performed by 16S rRNA gene sequencing.All three groups had plant growth promoting characteristics. Halophilic, alkaliphilic and haloalkaliphilic strains increased wheat yield about 20.6%, 42.7% and 58.2% in comparison with the control, respectively. The economic grain yield was maximum in H7 (3366 Kg ha -1 ), A11 (5530 Kg ha -1 ) and HA6 (2672 Kg ha -1 ) strains. The 16S rRNA gene sequencing indicated that all of them were owned to Bacillaceae family. These bacteria belonged to four genera including, Alkalibacillus, Bacillus, Haloalkalibacillus and Virgibacillus. H1 and H7 belonged toVirgibacillus genera and Virgibacillus pantothenticus species, respectively. Both superior alkaliphilic isolates were classified to Bacillus clausii. The haloalkaliphilic isolates (HA1 and HA6) were allocated to Virgibacillus marismortui and Alkalibacillus haloalkaliphilus species, respectively. All three extremophilic native groups of bacteria had the ability to aid the wheat plant to deal with high stresses, but plants inoculated with haloalkaliphilic strains had higher yield compared to the other groups due to better root growth and development.