The effect of growth-promoting bacteria on some morphologic and physiological traits of Celtis caucasica Willd. under lead stress

In order to investigate the effect of plant growth in soil pollution conditions in hackberry plant (Celtis caucasica Willd.), a test was carried out as a factorial design in a completely random pattern in the research conservatory of the University of Zanjan, Iran. The treatments included three levels of lead (0, 50, 100 mg/kg) and bacterial treatments invcluing Pseudomonas putida and Bacillus subtilis with concentrations of 105 and 108 cfu/ml. The attributes of the evaluation include root fresh and dry weights, plant height, total chlorophyll, total phenol, flavonoids and enzyme activity including peroxidase and malon-di-aldehyde, lead value in root and leaf and phosphorus in leaf. The two-way analysis of variance and compare the comparison with Duncan's method were used in order to investigate the effects of the lead stress and bacteria. The findings of this study showed that the use of bacteria in lead stress improved the growth and function of hackberry plant including root fresh and dry weights, plant height, total chlorophyll and flavonoids. The maximum amount of peroxidase was obtained in the treatment of 100 mg/kg lead and Bacillus subtilis (105 cfu/ml). In this treatment, the amount of lead in the fresh roots was 26.53 mg/g, which was a significant difference compared to the other treatments. Also, the highest amount of lead uptake by leaves (16.8 mg/g Fw) was observed under the treatment of Bacillus subtilis with a concentration of 108 cfu/ml. While hackberry plant performed well in terms of phytoremediation under lead stress, its growth characteristics were significantly diminished, but with the presence of growth-promoting bacteria specially Bacillus subtilis that can prevent severe reduction.