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the remediation of degraded areas should be preceded by analyses in the hydroponic
system and then field trials, in order to determine actual capacity to absorb toxic
elements and to identify the effect of environmental conditions on plant behaviour
(Zabłudowska et al. 2009). Another essential criterion is associated with biomass,
since plants exhibiting high efficiency of heavy metal uptake are generally
characterised by a slight increase in biomass (Herna ´ndez-Allica et al. 2008). In
this respect full understanding of the genetic regulation of plant biomass production
is crucial (Demura and Ye 2010). Within the last 20 years many different tools have
been used to increase the efficiency of phytoremediation thanks to the application
of specific additives in the form of complexing substances (Yan et al. 2012) and the
application of bacteria.

5.2 Role of Soil Conditions in Natural Plant Growth
(Macro- and Microelements)

Soil is a very important natural element of the environment preconditioning plant
life. It covers the earth crust (lithosphere) with a thin stratum 1.5–2.0 m thick which
developed from definite parent material under the influence of soil-forming factors
and processes. The essence of these processes consists in transformations of
mineral (degradation and synthesis) and organic (mineralisation and humification)
materials, horizontal and vertical dislocation of many chemical elements and
compounds, as well as exchange of matter and flow of energy between live
organisms and soil substrate or soil phases (solid, liquid, and gaseous)
(Prusinkiewicz 1999). The coloured effect of soil-forming processes involves
appropriate formation and arrangement of genetic horizons in the soil perpendicular
cross section. The upper horizons, called epipedons, as well as internal horizons
referred to as endopedons, are characterised by strictly defined parameters and exert
a strong impact on the membership of a given soil in a specific taxonomic unit
(FAO 2007; PTG 2011).
From the point of view of plant growth and development as well as biomass
production, near-surface horizons—frequently referred to as accumulative-humus
horizons—play a particularly important role. They are made up of the following
four components: mineral material and organic matter (solid phase), soil water
(liquid phase), and air (gaseous phase) (Fig. 5.1). In mature soils, this triple-phase
system remains in a certain state of dynamic equilibrium determining physical,
chemical, and biological soil properties. A disturbance of this balance under the
influence of natural factors is described as soil evolution, whereas any deterioration
of soil properties as a result of anthropogenisation (human pressure) results in soil
physical, chemical, or biological degradation. The most important constituents of
the solid phase comprise mineral and organic colloids, i.e. particles of dimensions
below 2 μM. Soils inherit their mineral colloid content together with their parent
material from which they were formed. In the majority of cases, these are classic-
sedimentary rocks and partially non-classic rocks, primarily, of post-glacial origin