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Cadmium (Cd) is one of the most widespread and toxic soil pollutants that inhibits plant growth and microbial activity. Polluted soils can be remediated using plants that either accumulate metals (phytoextraction) or convert them to biologically inaccessible forms (phytostabilization). The phytoremediation potential of a symbiotic system comprising the Cd-tolerant pea (Pisum sativum L.) mutant SGECdt and selected Cd-tolerant microorganisms, such as plant growth-promoting rhizobacterium Variovorax paradoxus 5C-2, nodule bacterium Rhizobium leguminosarum bv. viciae RCAM1066, and arbuscular mycorrhizal fungus Glomus sp. 1Fo, was evaluated in comparison with wild-type pea SGE and the Cd-accumulating plant Indian mustard (Brassica juncea L. Czern.) VIR263. Plants were grown in pots in sterilized uncontaminated or Cd-supplemented (15 mg Cd kg−1) soil and inoculated or not with the microbial consortium. Cadmium significantly inhibited growth of uninoculated and particularly inoculated SGE plants, but had no effect on SGECdt and decreased shoot biomass of B. juncea. Inoculation with the microbial consortium more than doubled pea biomass (both genotypes) irrespective of Cd contamination, but had little effect on B. juncea biomass. Cadmium decreased nodule number and acetylene reduction activity of SGE by 5.6 and 10.8 times, whereas this decrease in SGECdt was 2.1 and 2.8 times only, and the frequency of mycorrhizal structures decreased only in SGE roots. Inoculation decreased shoot Cd concentration and increased seed Cd concentration of both pea genotypes, but had little effect on Cd concentration of B. juncea. Inoculation also significantly increased concentration and/or accumulation of nutrients (Ca, Fe, K, Mg, Mn, N, P, S, and Zn) by Cd-treated pea plants, particularly by the SGECdt mutant. Shoot Cd concentration of SGECdt was twice that of SGE, and the inoculated SGECdt had approximately similar Cd accumulation capacity as compared with B. juncea. Thus, plant–microbe systems based on Cd-tolerant micro-symbionts and plant genotypes offer considerable opportunities to increase plant HM tolerance and accumulation.

The aim of our study was to assess the efficiency of application of biomodified nitrogen fertilizers for barley, to reveal the sources of nitrogen used for biomass formation with the use of the 15N stable isotope, and to study nitrogen flows in the system of fertilizers–soil–plants–atmosphere. We demonstrated in a model experiment the ability of the plant growth-promoting bacteria Bacillus subtilis Ch-13 to move from the granules of mineral fertilizers to plant roots and to colonize them effectively. The effectiveness of biomodified nitrogen fertilizers for barley, Nur variety, was assessed in a microfield trial. After the application of biomodified nitrogen fertilizers, the accumulation of 15N in the plants increased by 2–5 %, its incorporation in the soil decreased and gaseous losses were decreased by 7 % as compared with the use of the usual forms of fertilizers. The application of biomodified nitrogen fertilizers can be used in agricultural practice as a novel technology to regulate nitrogen flows in the system of fertilizers–soil–plants–atmosphere.

Aluminium being one of the most abundant elements is very toxic for plants causing inhibition of nutrient uptake and productivity. The aim of this study was to evaluate the potential of microbial consortium consisting of arbuscular mycorrhizal fungus (AMF), rhizobia and PGPR for counteracting negative effects of Al toxicity on four pea genotypes differing in Al tolerance. Pea plants were grown in acid soil supplemented with AlCl3 (pHKCl = 4.5) or neutralized with CaCO3 (pHKCl = 6.2). Inoculation increased shoot and/or seed biomass of plants grown in Al-supplemented soil. Nodule number and biomass were about twice on roots of Al-treated genotypes after inoculation. Inoculation decreased concentrations of water-soluble Al in the rhizosphere of all genotypes grown in Al-supplemented soil by about 30%, improved N2 fixation and uptake of fertilizer 15N and nutrients from soil, and increased concentrations of water-soluble nutrients in the rhizosphere. The structure of rhizospheric microbial communities varied to a greater extent depending on the plant genotype, as compared to soil conditions and inoculation. Thus, this study highlights the important role of symbiotic microorganisms and the plant genotype in complex interactions between the components of the soil-microorganism-plant continuum subjected to Al toxicity.

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