Mineral nutrient imbalance, total antioxidants level and DNA damage in common bean (Phaseolus vulgaris L.) exposed to heavy metals

Stress induced by soil contamination with heavy metals and their effects on some biomarkers and DNA damage in maize plants at the vicinity of Ferronikel smelter in Drenas, Kosovo

The Ferronikel smelter in Drenas is one of the main industrial areas in the Kosovo and pollution by heavy metals causes serious threat for all living organisms on this area. The objective of this study was to determine the concentration of some heavy metals (Fe, Cu, Mn, Cr, Cd, Ni and Pb) in agricultural soils and in maize plants, and their potential toxic effects on this plant through some sensitive biochemical and molecular markers. Maize seedlings growth in nine soil samples from different locations of this area. The highest concentrations of heavy metals in soils and maize leaves were conducted close to the Ferronikel smelter, and in some locations, the nickel and chromium concertation in soils exceeded 800 mg kg-1. A significant effects of heavy metals induced toxicity resulted in the, build-up aminolevulinic acid and reduced activity of δ-aminolevulinic acid dehydratase, and chlorophyll content in the maize leaves. In general, maize seedlings growth in polluted locations showed an increase in nuclear DNA content and in G2M phase. We concluded that locations close to the smelter are affected by soil heavy metals pollution and these biochemical and molecular analysis would be a powerful ecotoxicological tool in biomonitoring of heavy metal pollution.

Melatonin Modulates Plant Tolerance to Heavy Metal Stress: Morphological Responses to Molecular Mechanisms

Heavy metal toxicity is one of the most devastating abiotic stresses. Heavy metals cause serious damage to plant growth and productivity, which is a major problem for sustainable agriculture. It adversely affects plant molecular physiology and biochemistry by generating osmotic stress, ionic imbalance, oxidative stress, membrane disorganization, cellular toxicity, and metabolic homeostasis. To improve and stimulate plant tolerance to heavy metal stress, the application of biostimulants can be an effective approach without threatening the ecosystem. Melatonin (N-acetyl-5-methoxytryptamine), a biostimulator, plant growth regulator, and antioxidant, promotes plant tolerance to heavy metal stress by improving redox and nutrient homeostasis, osmotic balance, and primary and secondary metabolism. It is important to perceive the complete and detailed regulatory mechanisms of exogenous and endogenous melatonin-mediated heavy metal-toxicity mitigation in plants to identify potential research gaps that should be addressed in the future. This review provides a novel insight to understand the multifunctional role of melatonin in reducing heavy metal stress and the underlying molecular mechanisms.

Wheat biological responses to stress caused by cadmium, nickel and lead

Several stressors like different types of heavy metals are found in the soil and can affect the growth and genomic integrity of wheat grains (Triticum aestivum L.). The aim of this study was to compare the effect of exogenous Cd (30, 60, 120 mg kg^-1), Ni (50, 100 and 150 mg kg^-1) or Pb (100, 200 and 300 mg kg^-1) on wheat agronomic characteristics through the assessment of oxidative stress indices at protein and gene expression levels, photosynthetic pigments and genetic aberrations using RAPD analysis that were studied during two winter seasons (2015/2016 and 2016/2017). The results showed that all stressors significantly decreased the vegetative growth parameters, altered the activities of antioxidants enzymes in seedlings (after 30 days) and grains (after 5 months) and differently affected their expression levels in seedlings leaves and roots. Pb treated plants showed the poorest agronomic characteristics as it exhibited the worst affected wheat height, number of tillers, fresh and dry weight, flag leaf area as well as yield. Pb treatment caused poorest plant performance, it showed the highest proline content, least protein and chlorophyll contents, thus affects the overall plants growth followed by Cd and Ni, respectively. Furthermore, high Pb and Cd doses revealed highest degree of polymorphism and lowest degree of genome stability. Altogether, heavy metals accumulated mainly in wheat straw and induced genotoxic effect which consequently altered normal plant metabolism and pigment content which resulted in a significant reduction in wheat yield and quality. Moreover, Pb induced more genotoxic and phytotoxic effects than Cd and Ni.

Metal bioaccumulation and mutagenesis in a Tradescantia clone following long-term exposure to soils from urban industrial areas and closed landfills

Soil mutagens, particularly metals, may persist long after the source of pollution has been removed, representing a hazard to plants, animals, and humans in or near contaminated areas. Often, due to urban growth, previous land uses may be forgotten and hazards overlooked. We exposed Tradescantia clone #4430 plants to soil from two industrial areas (with different former uses) and two urban waste landfills in the city of Vilnius, all of which were long disused. Two modes of exposure were used: long-term exposure of growing plants in test soils for 0.5 or 1.0y, and short-term exposure of cuttings to water and dimethyl sulfoxide (DMSO) soil extracts. An increased frequency of micronuclei (MN) was observed with both modes of exposure. The concentrations of 24 metals and other elements were analyzed in the test soils and in above-ground plant parts, under both exposure modes, and the concentration coefficients (Cc) for various elements, the total contamination index (Zs) for soils and plants, and the bioaccumulation factor (BAF) for plants were calculated. These measurements allow a comparison of the contamination levels of soils and plants with equalized values. Metal accumulation levels in plants and soils showed significant differences, providing a better understanding of the genotoxicity of soils from closed landfills and highlighting the need to determine the concentrations of metals and other genotoxicants in plants in relation to genotoxicity.