Cadmium (Cd) is one of the most toxic environmental pollutants affecting cytogenetically the various organisms. The cytogenetic damage in root tip cells exposed to cadmium nitrate (CdNO3) solutions at four different concentrations (1, 10, 100 and 200 microM) was evaluated with biological tests based on micronucleus (MN) assay in two plant species, Allium sativum and Vicia faba. Additionally to the cytogenetic analysis, lipid peroxidation analyses were performed in both A.sativum and V.faba roots. Cd enhanced the MN frequency in both A.sativum and V.faba root tip cells, but no dose-dependent. Induction of MN is not depending on CdNO3 concentrations. Besides, high concentrations of Cd decreased the mitotic index and caused the delay in mitosis stages in both plants, mainly in V.faba. On the other hand, lipid peroxidation was significantly enhanced with external Cd in V.faba. The results clearly indicate that high concentrations of cadmium induce the lipid peroxidation resulting in oxidative stress that may contribute to the genotoxicity and cytotoxicity of Cd ions.

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The effects of drought, cadmium (Cd) and drought-Cd combinations on antioxidant compounds, antioxidant enzymes and shoot growth were investigated for drought tolerant [Lycopersicon peruvianum (L.) Mill.] and sensitive of (Lycopersicon esculentum Mill. cv. Lukullus) tomato species. Drought-Cd combinations significantly decreased shoot growth in both species (P < 0.01), drought stress also decreased shoot growth in drought sensitive L. esculentum. Cd was accumulated higher in the roots of drought sensitive L. esculentum than drought tolerant L. peruvianum. The chlorophyll contents decreased in all stress treatments in L. esculentum but did not change in L. peruvianum. Carotenoid contents significantly increased in all stress treatments in both species (P < 0.01). Significant increases in the contents of carotenoids in both species under stress conditions seemed to be associated with a protective role against reactive oxygen species (ROS). Ascorbate (ASC) content decreased during drought stress while increased under Cd stress. Catalase (CAT) and glutathione reductase (GR) activities significantly increased under drought stress in L. peruvianum while decreased in L. esculentum (P < 0.001). Ascorbate peroxidase (APX) activity decreased under all stress treatments in both species. Drought and Cd stresses increased superoxide dismutase (SOD) activity in both species. The present data did not show a relation between drought tolerance and levels of antioxidative defence system that was induced from Cd. However, there is a clear relationship between Cd uptake and drought tolerance of plants.

IntroductionSilver nanoparticles (AgNPs) are widely used among other nanoparticles in many industries within a wide range of consumer products because of their antibacterial and biocidal properties (Thuesombat et al., 2014). In recent years, the significant increase in the consumption of nanoparticles has caused environmental, health, and safety concerns regarding their potential effects (Ma et al., 2010;Pokhrel and Dubey, 2013). Nanoparticles could uncertainly spread to the environment. However, the interaction between AgNPs and plant systems is still not well known (Patlolla et al., 2012;Song et al., 2013).AgNPs are known to be absorbed by plants and could interact with intracellular parts causing water imbalances, cell damage, and decreases in photosynthesis (Kumari et al., 2009;Qian et al., 2013). They are also reported to have genotoxic effects on plant cells, inducing chromosomal aberrations and micronucleus induction (Patlolla et al., 2012). However, the impacts of nanoparticles on plants can vary according to the nanoparticle concentration, size, chemical properties, and plant species (Ma et al., 2010;Thuesombat et al., 2014).Nanotoxicity could lead to oxidative stress and previous studies indicate that AgNPs could induce toxicity due to their effect on reactive oxygen species (ROS) formation (Qian et al., 2013;McShan et al., 2014). The imbalance of ROS production and antioxidant activity can cause oxidative damage, and plants cope with this oxidative damage by their antioxidant defense mechanism (Saed-Moucheshi et al., 2014). Previously, studies on the genotoxicity of nanoparticles have used cell viability, chromosome aberration, or micronucleus assays to identify the genotoxic effect, and comet analysis for detecting the DNA damage in different plant species (Kumari et al., 2009;Kumari et al., 2011;Patlolla et al., 2012;Ghosh et al., 2012). However, these methods are very restricted for identifying the genotoxic effects of nanoparticles at the DNA level. DNA-based techniques are sensitive and selective assays that help to determine the genotoxic effects of environmental pollutants on DNA. One of these methods used for these aims is the intersimple sequence repeat (ISSR)-PCR assay. ISSR-PCR uses as primer microsatellite repeats (Zietkiewicz et al., 1994). The ISSR-PCR method is more sensitive than the random amplified polymorphic DNA assay (RAPD) (Correia et al., 2014;Bajpai et al., 2015), because of the exhibiting specificity of the sequence-tagged-site markers and high ratio of reproducibility potential owing to the use of longer primers (16-25 bp).

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