The effect of biofilm forming growth promoting bacterium and tryptophan on root characteristics of rye and their relationship with root cadmium accumulation

 Auxin producing plant growth-promoting bacteria can prevent the entry of heavy elements such as cadmium into the aerial section of plants. This issue was investigated using Bacillus atrophaeus in the presence and absence of tryptophan by inoculation of rye under cadmium contamination.

 This experiment with 12 treatments including two bacterial levels (inoculation with B. atrophaeus and non-inoculation), two levels of the tryptophan amino acid (application and non-application) and three cadmium levels (zero, 50 and 100 mg.L-1) was performed as hydroponic culture with rye culture in factorial experiment with randomized complete design.

 The results showed that the co-application of tryptophan with bacterial inoculation of rye as a superior treatment reduced the entry of cadmium into its aerial section by 53 and 37% compared to the control treatment respectively at 50 and 100 mg.L-1 of cadmium. Also, the highest amount of cadmium accumulation in the roots, especially at the level of 100 mg.L-1 cadmium, was 2 times higher than the control treatment. The study of root characteristics also showed that there is the highest correlation between root cadmium concentration and root surface density and root surface density characteristics (r2=0.87).

 In order to reduce the entry of cadmium into the shoots of rye, B. atrophaeus can be inoculated alone or with the addition of tryptophan. Due to the high accumulation of cadmium in the roots, this compound can be used in the cadmium phyto-stabilization process.