Physiological-Biochemical Reactions of Sorghum bicolor to Bacterization and Impact of Pollutants

The physiological and biochemical parameters of sorghum (Sorghum bicolor L. Moench) characterizing the reactions of its 3-week-old seedlings to the presence of biotic (bacterial strain Gordonia sp. N7) and abiotic (nickel and n-hexadecane) factors were studied. Such indicators as plant survival, biomass of roots and shoots, tolerance indices, nickel translocation factor (TF), content of photosynthetic pigments, and spectrum and activity of peroxidases in root exudates were studied. It was shown that the responses of sorghum to the combined influence of stressors differed from those under their individual influence. It was shown that n-hexadecane and bacterization, individually and together, had a stimulating effect on the growth of sorghum biomass. On the contrary, nickel at the studied concentration (20 mg/kg) showed pronounced inhibitory impact on the studied indicators. The combination of the studied components changed some indicators relative to the individual ones, but the toxicity of the metal dominated, significantly leveling the stimulating effect of n-hexadecane and strain N7 on plant growth. However, depending on the state of the photosynthetic apparatus and the activity of peroxidases in root exudates, different plant responses to combined stress were noted. Significant changes occurred in the processes of nickel accumulation in plant organs: in the presence of n-hexadecane and, especially, bacteria, the accumulation of nickel in the aboveground part of sorghum increased and TF increased more than two times. The obtained results provide justification for the feasibility of using the strain Gordonia sp. N7 as a technological method facilitating the process of phytoremediation to extract nickel from contaminated soil using Sorghum bicolor. At the same time, it should be noted that the identified effect should be taken into account in agricultural feed production since it indicates an increase in the contamination of plant products with heavy metal.