Khomenko I. Adaptive reactions of lettuce plants (Lactuca sativa L.) under the action of cadmium ions and metal nanoparticles

The thesis deals with the study of variety-specific adaptive reactions of two different in phenol metabolism lettuce varieties (Lactuca sativa var secalina L., green Lolo variety and red/anthocyanin variety – Lolo Ross) under increased cadmium ions and metal nanoparticles influence in the substratum. According to the obtained results, the sortspecificity of the adaptive reactions of different anthocyanin-colored phenotypes of lettuce (Lactuca sativa L. var. secalina) to the action of cadmium ions and nanoparticles of metal-micronutrient elements was revealed. The adaptive response to mineral stressors of investigated lettuce plants manifests itself at the level of a holistic organism as the integration of multi-level systems and set of exogenous and endogenous mechanisms of leveling the negative effects of the transformed nutritional medium. It has been established that early-ontogenic lettuce plants of the studied varieties demonstrated a non-specific reaction of growth inhibition and activation of heavy metal intracellular detoxification mechanisms for the influence of the cadmium-loaded environment, which manifests itself in reducing the anthocyanin content in the roots and accumulation of these compounds in the leaves. It was found that red Lolo Ross's lettuce phenotype more intensively accumulated Cd2+, compared with the green Lolo variety, with a significant prevalence of root content. Estimation of the translocation factors of different in anthocyanin level lettuce phenotypes indicates the high protective ability of the Lolo Ross red variety under the influence of cadmium in comparison with the green Lolo. The obtained translocation factor results are important for the assessment of the plant nutritional value of the transformed environment but demonstrate the inapplicability of this culture use in phytoremediation purposes. It was shown that Lolo Ross lettuce variety is able to support the metabolism homeostasis under the influence of cadmium ions, whereas green Lolo variety plants showed the increase in xeromorphic features of the leaf blades, a decrease of photosynthetic pigments content and peroxidase activity against the background of increasing the non-enzymatic antioxidant metabolites content. It was established that pre-treatment of lettuce plant with metal nanoparticles of nutritive microelements contributed to seed germination and increase of growth parameters of both early-ontogenic investigated varieties, and also showed the induction of the phenolic activity of green lettuce Lolo, in contrast to the red Lolo Ross variety. Moreover, it was shown that pre-treatment with metal nanoparticles showed the prolonged influence on red Lolo Ross lettuce variety under the obtained parameters of tolerance index, guaiacol-peroxidase activity, photosynthetic and phenolic pigments content. A slight leveling of the essential metal nanoparticles pre-treatment for the negative Cd-effect in the green Lolo variety was established, which is manifested in the growth of the dry mass, the maintenance of the photosynthetic apparatus pigment composition, the decrease of the lipid peroxidation process products content, and the accumulation of phenolic compounds with a decrease of the guaiacol-peroxidase enzyme activity.