Root growth of the seedlings of maize cultivars Premia and Blitz exposed to 2 µM cadmium (Cd), nickel (Ni) or both metals acting simultaneously (Cd + Ni) for 72 h was significantly reduced but not ceased. The effect was more pronounced in the seedlings of the cv. Blitz. The heavy metals (HMs) contents increased significantly in the roots. Simultaneous application of metals had an antagonistic effect on either Cd or Ni uptake in Premia but not in Blitz. In control roots the contents of ascorbic acid (AsA) and dehydroascorbic acid (DHA) were lower and gluthatione (GSH) content was higher in Premia than in Blitz. A decrease of AsA content was induced by all metal treatments in Premia but only by Cd + Ni in Blitz while an increase was induced by single metals in this cultivar. All metal treatments increased DHA contents in both cultivars. GSH content decreased significantly in Premia treated with Cd or Cd + Ni, and in Blitz treated with Ni. Unlike the contents of AsA, DHA and GSH, the increased metal concentrations in root cells did not affect the membrane potential (EM). The changes in antioxidant contents depended on both, maize genotypes and HMs treatments. Nevertheless, the results indicated a role of antioxidative system in minimizing the effects of oxidative stress and protecting cell membranes in both maize cultivars.

The fungal strain Aspergillus fumigatus 3 2 isolated from the tailings pond at the copper mine "Vlaykov vruh," Bulgaria, showed high tolerance to Cu 2þ and Zn 2þ . This study was designed to explore the relationship between Cu 2þ and Zn 2þ tolerance and cellular response to oxidative stress. The model strain was identified to species level by morphological and molecular methods. Fungal cultures were exposed to enhanced concentrations of metal ions. The effect of Cu 2þ and Zn 2þ was evaluated by the changes in fungal growth and morphology, the level of oxidative stress biomarkers, and the antioxidant activities of enzymes such as superoxide dismutase (SOD) and catalase (CAT). Two different cellular responses occurred: The concentrations of up to 500 mg/mL caused enhanced levels of oxidative stress biomarkers (glycogen and trehalose accumulation and oxidatively damaged protein content), as well as an increase in SOD and CAT activities. The treatment with concentrations from 500 to 2000 mg/mL led to enhanced glycogen consumption, accelerated proteolysis, and a decrease in SOD and CAT activities. The present results provide additional information about the participation of oxidative stress and antioxidant defense in enhanced tolerance of fungi isolated from metal-polluted soils. Probably, survival at extremely high concentrations also requires the participation of other defense mechanisms. Furthermore, the enhanced understanding of these processes will provide essential tools for efficient remediation practices.

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The processes of lipid peroxidation induced by heavy metals in leaves of woody species under the influence of an industrial enterprise were studied. In the assimilation organs of Populus italica, a high accumulation of most compounds of heavy metals was found (intratissue contamination was over five-fold higher than in the control), with zinc as the most abundant metal. Aesculus hippocastanum in the zone of severe pollution most actively accumulated nickel, while Betula pendula accumulated cadmium. At early stages of leaves development, high rates of intratissue contamination were observed for all species. In the leaves of P. italica, during their morphogenesis, the level of secondary peroxidation products (TBА-active compounds) was lowest among the studied species and did not exceed the control values by more than 1.8 times. This is apparently due to increased intensity of functioning of antioxidant enzyme systems, such as glutathione and ascorbic (Halliwell-Asada cycle), and high phytochelatin and metallothionein biosynthesis in leaves, which stipulate its highest physiological stability to altered environment. Instead, in the leaves of A. hippocastanum and B. pendula with low levels of accumulation of most heavy metals, the content of TBA-active products increased 2.7 and 2.9 times, respectively, comparing to the control. It has been shown that plantations of P. italica in industrial conditions were relatively stable with a total score of assimilation organs, branches and trunk damage up to 1.3, while in A. hippocastanum and B. pendula a long term effect of pollutants at monitoring sites resulted in 25-40% of leaves damaged by necroses and chloroses. Skeletal branches of both species were affected by rot, crown rarity reached more than 40%, and frost cracks 20-25% larger than in the control occurred. Aesculus hippocastanum and B. pendula are characterized by an unstable qualitative state of 30-60% of individuals which are at various stages of dying or significantly depressed.

The interactive effects of Cd and natural siliceous mineral analcite on Cd phytotoxicity and rate of accumulation in plant tissues have been analyzed. The test-plants of corn and hemp were grown in pots under controlled conditions of light, temperature, and soil moisture for 21 days in experiments modeling the following treatments: (1) without any amendments (control); (2) with the application of 0.1 % and 0.5 % (by weight) of CdSO4; (3) Cd salts (CdSO4) + analcite 0.1 g, 0.25 g, and 0.5 g per container. Test-plants performance was assessed by their growth characteristics (shoot height and root length), the content of photosynthetic pigments, macro- and micronutrients in leaves. The effect of Cd on maize and hemp plants inhibited their growth, chlorophyll biosynthesis in the leaves, led to a change in the balance of macro- and microelements, which leads to the accumulation of Cd in the tissues of shoots of both studied crops. Application of analcite partially compensated for the negative effects of Cd salts on the crop’s growth, chlorophyll content, and balance of nutrients and reduced Cd accumulation significantly in shoots.

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Joint influence of cadmium and nickel was investigated on the feature of their accumulation by the vegetative organs of 10-days' old maize shoots. It was established that most intensively noted metals are taken in by the roots of shoots in the first 7 hours stressing influencing, while in leaves they appear only after a 7-hour long exposition. It was stated that the absorption process of the noted metals by a root system is carried by two-phase character. The indexes of inner-tissue contamination are calculated. Activating by the cadmium and nickel ions of lipid peroxidation as marker of the stressing influencing, and also was shown the proper increase of intensity of functioning of ascorbate peroxidase as the antioxidant enzyme protection of cell.