Masoud Drakhshi, Mehrnoush Eskandari Torbaghan & Masoud Eskandari Torbaghan
According to the FAO study, about 20 to 50 percent of the world's agricultural soils suffer from different degrees of salinity. Various reasons including low absorption of trace elements in saline and alkaline soils due to high-pH soils accompanied by plenty of lime such as Iran soils, ionic imbalance, low organic matter, carbonate presence in irrigation water, the inexorable and imbalance use of fertilizers and finally the subsequent droughts led to study both the bioavailability of iron and zinc within halophilic bacterial strains collected from terrestrial resources and availability of these nutrients for plants under salt stress by means of DTPA-TEA extraction method. Halophilic bacterial strains were isolated and purified from six saline soils in Khorasan Razavi Province (Iran) using the Ventosa moderately halophilic bacteria culture medium. Afterward, the concentrations of Fe and Zn in these strains with three replicates were measured by the DTPA-TEA method. The results showed that only four strains H2, H1, H11 and H3 of the fourteen isolated had iron; however, the iron concentration of the strains did not differ significantly or to the control (bacteria culture medium). Measurement of zinc showed that all halophilic strains had zinc except for two strains: H9 and H11, but the amount of zinc of strains did not differ significantly between strains or to the control. Strain H2 also showed the highest concentration of extractable iron and zinc. Concentrations of iron and zinc in the strains showed a low correlation coefficient (R2=0.15). Due to the absence of both iron and zinc in the bacteria medium, the amount of iron and zinc measured in strains may be structural and constitute some part of microbial tissues. Because of measuring these micro nutrients based on the simple method of EDTA-TEA, the chance of bioavailability of the nutrients exists in the rhizosphere of plants under salt stress conditions. In addition, the average electrical conductivity, osmotic pressure and total dissolved solids in halophilic bacterial extracts were 60.85 dS/m, 21.61 atmospheres, 3.89 percent respectively. The high osmotic pressure in bacterial extracts, which is equal to the osmotic pressure of the soil in permanent wilting point (10 to 20 atmospheres), could be another reason for the viability and efficiency of these special bacteria in high salinity. Hence, due to the high bacterial population growth and survival of bacteria under the conditions of high salinity and osmotic pressure of the soil, these bacteria may have the ability to help the stressed plants and biofortification of these important micronutrients in human food.
Published Date: 2015-06-25;