The Evaluation of Heavy Metal Toxicity in Plants Using the Biochemical Tests

Abstract

The evaluation of the toxicity and stress caused by heavy metals on plants is very important part of the phytoremediation research. Several physiological parameters can be used to assess the heavy metalinduced stress such as germination, plant growth and biomass production, photosynthetic pigments, antioxidant enzymes or antioxidants. Published results of measured physiological parameters in plants exposed to metals were characterized from of the negative effects of metals point of view and compared with the experimental study of the metal (Cu, Cd, Zn) toxicity in flax (Linum usitatissimum) and China aster (Callistephus chinensis) using the biochemical tests under the laboratory conditions. The germination and biomass production of C. chinensis significantly decreased with the increase of metal concentration which is considered a very typical response, however in L. usitatissimum slight stimulation of germination and biomass production at low metal content was observed. From the two studied plants C. chinensis expressed typical symptoms of the heavy metal toxicity including the decrease of total chlorophyll, chlorophylls a, b. On the contrary, heavy metal ions affected positively the physiological parameters of L. usitatissimum when low metal concentrations were added for example slight increase of the chlorophyll concentration in leaves was recorded. The decrease of the chlorophyll content was observed only at the high metal content. On the other hand, the typical response of plants on the heavy metal stress - the increase in peroxidase activity - was observed only for L. usitatissimum but not for C. chinensis that in all other tests showed significant toxicity symptoms. So if only one physiological parameter would be considered incorrect interpretation could be concluded. With the increase of phytoremediation practical applications the more systematic tests of heavy metal stress are necessary to help scientists working in that field correctly interpret their results and understand the plant behaviour.