Effects of the Application of Different Concentrations of NaN3 for Different Times on the Morphological and Cytogenetic Characteristics of Barley （Hordeum vulgate L.） Seedlings

Sodium azide （NAN3） has been used in many biological studies as a mutagen. In the present study, the morphological and cytogenetic effects of NaN3 on barley （Hordeum vulgare L.） seedlings were investigated. Seeds of barley were treated with different concentrations of NaN3 （0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mmol/L） and applied for different periods of time （3 and 4 h）. Parameters investigated, except for the mitotic index, were determined on Days 7 and 14. Increasing concentrations of NaN3 affected germination rates on Days 7 and 14 following application for 3 and 4 h. Although the length of the roots and leaves was affected by treatment with NaN3 on Day 14 of the germination period, coleoptile length was affected by NaN3 treatment on Day 7. Increasing concentrations of NaN3 and increased treatment period decreased the mitotic index compared with the untreated control. The inhibitory effects of NaN3 on the mitotic index indicate that NaN3 can have genotoxic and mutagenic effects on barley seedlings.

Cytogenetic studies of chromium(Ⅲ) oxide nanoparticles on Allium cepa root tip cells

The current study evaluates the cytogenetic effects of chromium（Ⅲ） oxide nanoparticles on the root cells of Allium cepa.The root tip cells of A.cepa were treated with the aqueous dispersions of Cr2O3 nanoparticles（NPs） at five different concentrations（0.01,0.1,1,10,and 100 μg/m L） for 4 hr.The colloidal stability of the nanoparticle suspensions during the exposure period were ascertained by particle size analyses.After 4 hr exposure to Cr2O3 NPs,a significant decrease in mitotic index（MI） from 35.56%（Control） to 35.26%（0.01 μg/m L）,34.64%（0.1 μg/m L）,32.73%（1 μg/m L）,29.6%（10 μg/m L） and 20.92%（100 μg/m L） was noted.The optical,fluorescence and confocal laser scanning microscopic analyses demonstrated specific chromosomal aberrations such as-chromosome stickiness,chromosome breaks,laggard chromosome,clumped chromosome,multipolar phases,nuclear notch,and nuclear bud at different exposure concentrations.The concentration-dependent internalization/bio-uptake of Cr2O3 NPs may have contributed to the enhanced production of anti oxidant enzyme,superoxide dismutase to counteract the oxidative stress,which in turn resulted in observed chromosomal aberrations and cytogenetic effects.These results suggest that A.cepa root tip assay can be successfully applied for evaluating environmental risk of Cr2O3 NPs over a wide range of concentrations.

Assessing combined toxic effects of tetracycline and P25 titanium dioxide nanoparticles using Allium cepa bioassay

Usage of titanium dioxide nanoparticles(TiO_(2) NPs)and tetracycline(TC)has increased significantly in the present era.This leads to their release and accumulation in the environment.Both the compounds,individually,can have adverse toxic effects on the plants.Their binary mixtures can increase this degree of damage.The present study aimed to evaluate the toxicity of both the contaminants in individual and binary mixtures in Allium cepa.Further,the toxicity of TiO_(2) NPs upon UVA pre-irradiation was also measured.Results showed that UVA pre-irradiated NPs(UVA-TiO_(2) NPs)had a significant decrease in cell viability than their non-irradiated counterparts(NI-TiO_(2)),denoting an increase in photocatalytic activity upon UVA pre-irradiation.Very low concentrations of TC(EC10=0.016µmol/L)mixed with TiO2 NPs significantly increased the toxicity for both UVA-TiO_(2) and NI-TiO_(2) NPs.Intracellular ROS generation was significantly high for UVA-TiO_(2) NPs.However,TC did not have any effects on ROS production.Both the compounds exhibited genotoxic potential in A.cepa.Different chromosomal abnormalities like anaphase bridges,telophase bridges,laggard chromosomes,binucleate cells,etc.were observed.The binary mixture of UVA-TiO_(2) NPs and TC showed the highest chromosomal aberrations(64.0%±1.26%)than the mixture with NI-TiO_(2) or the individual contaminants.This decreased significantly after recovery(46.8%±1.92%),denoting the self-repair processes.This study proved that UVA-TiO2 NPs were more toxic and could be enhanced further when mixed with a sub-lethal concentration of TC.This work will help to assess the risk of both compounds in the environment.