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Influence of Metal-Resistant Rhizobacteria on the Growth of Helianthus annuus L. in Cr(VI)-Contaminated Soil

Bahadur, Ali, Afzal, Aftab, Ahmad, Rizwan, Nasir, Fahad, Khan, Aman, Suthar, Vishandas, Jan, Gul, Batool, Asfa, Zia, MuhammadAmir, Mahmood-ul-Hassan, Muhammad
Water, air, and soil pollution 2016 v.227 no.12 pp. 467
Helianthus annuus, bioremediation, chromium, greenhouse experimentation, harvesting, metal tolerance, polluted soils, rhizosphere bacteria, roots, seeds, shoots
Use of heavy metal-tolerant bacteria for bioremediation is an environmentally safe and economical approach. Selected chromium-tolerant bacteria were tested in a greenhouse experiment. Different sets of pots were contaminated with three rates of Cr, i.e., 20, 30, and 40 ppm, using K₂Cr₂O₇ and incubated for 1 month. Helianthus annuus (sunflower) seeds of Hysun-33 variety were inoculated with already screened Cr-tolerant bacteria (SS1, SS3, and SS6) along with un-inoculated seeds as control. Completely randomized design was used and two plants per pot were maintained after thinning. At harvesting, fresh as well as dry shoot and root weights were measured. Shoot and root samples were analyzed for Cr contents. The maximum increase in dry shoot and root weight (58 and 63%) was obtained by SS6 followed by SS1 (48 and 42%) and SS3 (37 and 47%) over control at various Cr concentrations. Cr accumulation in shoot and root was also enhanced by all the bacteria compared to control. Regarding the extent of total Cr uptake, SS6 enhanced Cr accumulation up to 107–171%, SS1 99.3–135%, and SS3 91–138% at 20, 30, and 40 ppm Cr, respectively. It is concluded from the study that there was a decreasing trend in growth with the increase of Cr concentration. All the bacteria improved growth and Cr accumulation significantly over control; however, SS6 found best among all Cr-tolerant bacteria. These bacteria can effectively be used for crop improvement and bioremediation.