The incidences of suspected Boron (B) deficiency have increased recently in Kentucky tobacco fields, potentially due to recent changes in management practices. The symptoms observed in the field include; hollow stalk, stunted growth, deformed or no bud formation, small slits on the lower leaf midrib and uncontrollable breaking of the midrib approximately two inches from the stalk. B is a micronutrient tobacco needs in minute amounts, however excessive additions of B could cause toxicity. The objectives of this work were to 1) establish critical points for B sufficiency, 2) describe and define B deficiency and toxicity symptoms and 3) develop field strategies to aid in the mitigation of B deficiency. A general nutrient response curve was generated utilizing solution culture experiments. The peak of the response curve appeared to occur at solution B concentration of 100 µM. Trace-levels of B contamination and small plant size in the solution culture limited the development of deficiency symptoms. Toxicity was observed at solution concentrations of 400 µM and above. Despite choosing sites with a history of B deficiency, deficiency symptoms were not observed during this study. Toxicity was observed when 0.56 kg B/ha or greater was applied as simulated transplant water treatments. No toxicity was observed when B was applied as a soil broadcast or foliar application. Recommendations are to apply B with caution as a broadcast application to avoid potential problems with toxicity. Additional research is required to refine the nutrient response curve and better understand B deficiency.

Nowadays, the environmental pollution by heavy metals is very serious problem all around the world. Radionuclides, including uranium, are heavy metals that cause both chemical and radioactive pollution. Naturally occurring uranium is not so dangerous for living organisms. Human activities, especially uranium ore mining and use of phosphate fertilizers, have increased its concentration in the environment with consequent contamination of soil, water and air. Compared to other countries, the Czech Republic is relatively rich in deposits of uranium ore. Extensive mining results in large contaminated areas, containing not only uranium but also other heavy metals and xenobiotics that need to be removed from the environment. One way how to decontaminate soils and waters is phytoremediation. This eco-friendly and cost-effective technique exploits the ability of plants to take up, translocate, transform and sequester xenobiotics. In order to provide functional phytoremediation, it is necessary to understand the mechanisms of plant responses to stress caused by xenobiotics. Therefore in my master thesis, I focused on the impact of uranium on physiological processes of uranium-stressed plants, with the emphasis on carbohydrate metabolism and antioxidative defense mechanism. Powered by TCPDF (www.tcpdf.org)