Iutynska O. Iutynska O.A. Cytomorphological and biological aspects of the course of Tobacco mosaic virus infection under chronic effect of heave metal ions. - Manuscript.

The thesis is focused on investigation of biological properties and cytomorphological aspects of the development of TMV-induced infection under chronic effect of heavy metals. For the first time, we have established positive dependency between the elevated content of zinc in plant tissues and increased concentration of TMV in systemically infected tobacco plants. It was demonstrated that additional stress factor of abiotic nature (heavy metals) may influence the course of infection invoked by TMV or PVX. Plants, both in field and laboratory conditions, accumulate more virus in systemically invaded tissues. Dual effect of both stress factors (heavy metals and virus infection) leads to the development of more pronounced virus-specific symptoms, however delayed in appearance. Time of symptoms' development coincides with maximum virus content in plants. We have shown that systemic transport of TMV in tobacco plants is inhibited by adding average amounts of zinc (but not lead) compounds into soil. Additionally, influence of Zn2+ and Pb2+ on the arrangement of virus particles in vitro and on the formation of virus-specific cell inclusions in vivo has been confirmed. It was demonstrated that prolonged cultivation of TMV on systemically infected Nicotiana tabacum cv. Samsun plants under chronic effect of zinc at toxic concentration does not induce qualitative and quantitative alterations in virus properties. Cytomorphological studies revealed synergetic combination of virus infection and heavy metals' impact on TMV-infected parenchyma cells of tobacco leaves. For the first time, crystal inclusions of TMV have been found in peroxisomes.