The mechanism building tolerance of plants to heavy metals is closely connected with processes which reduce the uptake and transport of metals and with detoxification on cellular membranes and inside cells.
As the soil pH increases (within 6.5-7.5), metals, especially zinc and - To a lesser degree - Copper become less toxic to plants. Higher bioavailability of heavy metals is observed in soils with a low content of humic acids.
Alpus and dangerous forest translated series#
Mobility and plant availability of heavy metals depend on a series of factors, for example the soil pH, content of organic matter, grain-size composition of soil, content of iron and manganese oxides, soil sorption capacity and the type of metal. The effect induced by heavy metals is more pronounced in the early development of plants. Crops cultivated on soil with an elevated content of heavy metals typically present inhibited growth, reduced transpiration, chlorosis of leaves, limited germination of seeds and deformations of the root system. The purpose of this study has been to discuss the characteristics of these elements in terms of the chemical properties and the role in the natural environment, the effect they produce on plants when present in excessive concentrations in soil and the response of soil microbes and enzymes to such contaminants. In Poland, soils contaminated with heavy metals, including cadmium, copper and zinc, occur only locally. Cadmium is different in that its essential role in the proper functioning of living organisms has not been proven yet. Some soils suffer from zinc and copper deficits, which is why they are enriched with fertilizers containing copper or zinc to satisfy the nutritional requirements of crops. On the contrary, such elements as copper and zinc are essential constituents of physiological processes in all living organisms, including microorganisms and plants. In the said concentrations, heavy metals do not cause undesirable changes in the development of plants. Heavy metals when present in amounts equal to the geochemical background do not interfere with the soil metabolism, which is associated with the growth and development of soil microorganisms as well as the processes of synthesis and re-synthesis, governed by intra- and extracellular enzymes.
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