M.A. El-Kholy’s research while affiliated with Al-Azhar University and other places

In this study we compared the cytological effect and chromosomal behavior of root meristems of Allium cepa, induced by ZnO bulk and ZnO nanoparticles (NP). Four different concentrations of ZnO bulk and ZnO nanoparticles (2.5, 5, 10 and 20 ppm) were used to treat the root tips at different durations (2, 4, and 6 hours). The influence of these treatments on germination percentage and radicle length as well as mitotic index and chromosomal aberration was investigated. Our results indicate that all applied concentrations of ZnO bulk and ZnO nanoparticles caused a reduction in seed germination percent and radicle growth, as well as in mitotic index (MI) of Allium cepa seeds as compared to control. These reductions were accompanied by increase in concentration and/or duration of treatment. The total percentage of chromosomal aberrations were variable, with the change in concentrations and duration of treatment. Both bulk ZnO molecules and ZnO nanoparticles, induced different types of chromosomal abnormalities such as micro-nuclei, disturbed chromosomes, chromosomal stickiness, laggards, bridges, chromosomal fragmentation and diagonal. These abnormalities indicates true clastogenic possibility of ZnO bulk and ZnO nanoparticles.

The effects of different treatments with zinc sulfate (Zn(2+)) on the cytology and growth of Nigella sativa and Triticum aestivum were investigated. Five concentrations of zinc sulfate ranging from 5 to 25mg/l were applied for 6, 12, 18, and 24h. The treatments reduced the germination percentages of N. sativa seeds and T. aestivum grains and inhibited the root growth of both plants. Concentrations higher than 25mg/l of Zn(2+) applied for 24h were toxic for both plants. The non-lethal concentrations of Zn(2+) showed an inhibitory effect on cell division in root tips of both plants and caused a decrease in their mitotic index values. The reduction in MI in root tips of T. aestivum was more evident than that of N. sativa. All treatments changed the frequency of mitotic phases as compared with the control values. The total percentage of abnormalities in N. saliva was more than that in T. aestivum. Zn(2+) treatments produced a number of mitotic abnormalities in dividing cells in root tips of both plants resulting from its action on the spindle apparatus such as C-metaphases, lagging chromosomes and multipolar anaphases and telophases. Also, Zn(2+) induced vacuolated nuclei and irregular prophases. The induction of chromosomal stickiness and chromosomal aberrations such as bridges and breaks indicates its action on the chromosome. These abnormalities (chromosome breaks and chromosomal bridges at ana-telophases) indicate true clastogenic potential of the ions tested.