**Acknowledgements**

is source of nutrients for plant e.g. nitrogen compounds. Microorganisms may also increase the solubility of minerals such as phosphorus, and thus make them more accessible for plants. Another mechanism of protection of plants by microorganisms is the synthesis of low molec‐ ular weight siderophores in addition to phytosiderophores. Siderophores bind the free iron in the rhizosphere of plants. Lack of free iron negatively affects the proliferation of fungal pathogens in the root system of plants [93, 94].The presence of microorganisms can also initiate the synthesis of plant hormone such as auxins, cytokinins and gibberellins, which promote the growth of plants [91, 95]. Equally important is the mechanism for reducing stress by reduction of stress hormone ethylene concentration in plant by synthesis of microbial enzyme 1-

During the life of the plant its growth may be influenced by microorganisms with one or more of these mechanisms. Influence is most evident in plants grown under stressful conditions.

In a consortium consisting of microorganisms and plants growing in the contaminated soil, in addition to the above mentioned mechanisms, can occur production of metabolites or inter‐ mediates of degradation no matter whether by plant or microorganism. These metabolites may be by the other partner further degraded and metabolized or they may be toxic. The study of the metabolism of both biological systems and their possible influence should lead to the obtaining of such a system consisting of plant - microorganisms, which increases speed and

The issue of co-operation of plants and microorganisms on degradation of CBA is solved in

Haby and Crowley [84] compared the degradation capacity of soil from the rhizosphere of perennial ryegrass (*Lolium perenne*) with non-vegetated soil. Results showed that the degrada‐ tion rate of 3-CBA was at the beginning of the experiment accelerated by the rhizosphere soil, they also showed that in soil from the rhizosphere is increased amount of microorganisms [84].

Dittmann et al. [97] examined the ability of three months old pine seedlings (*Pinus sylvestris*) with mycorrhizal fungi *Suillus bovinus* to degrade 3-CBA. They found that 3-CBA is accumu‐ lated in the aboveground parts of the seedlings and removal efficiency of 3-CBA from the soil by a consortium was very low (around 25% for 4 weeks). In plant tissues were not detected

soil. Therefore they concluded that 3-CBA was not or only to a very small extent degraded by

The aforementioned grass *Elimus dauricus*, together with microorganismus *Pseudomonas aeruginosa* R75 and *Pseudomonas savastanoi* CB35 was able to remove almost 50% of 2-CBA from soil during 56 days [98]. The consortium showed greater metabolic efficiency than non-

In this work has been continued testing the degradation capacity of microorganisms and plants with other grasses and other CBAs or with a mixture of CBAs. The same composition of the

in comparisom with control plants grown in uncontaminated

aminocyklopropan-1-carboxylate deaminase (ACC deaminase) [96].

**4.1. Plant and microbial cooperation on chlorobenzoic acids remediation**

efficiency of the xenobiotics degradation process.

20 Applied Bioremediation - Active and Passive Approaches

several publications.

elevated concentrations of Cl-

plants [97].

vegetated soil.

The work was supported by the grant GAČR 525/09/1058 and EU project MINOTAURUS (FP7- KBBE-2010-4/265946).
