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The thesis describes the first step of the research leading to transposon tagging of the resistance genes against late blight of potato (Phytophthora infestans). Different diploid potato populations have been developed in which four R-genes have been localized on the RFLP map. Screening for high regeneration and transformation competence in a segregating population showed positive correlation between the Rl gene and the competence for transformation. It resulted also in the selection of a diploid potato clone suitable for transposon tagging. The transformation of this clone with Ds-carrying T-DNA and the localization of 60 different T-DNA insertions were carried out. The involvement of other genetic factors in the expression of the R-genes was detected.
The purpose of this paper is to review the biogeochemical nitrogen cycle. The importance of nitrogen derives mainly from its fundamental nutritional role, but is also due to the fact that nitrogenous substances are important environmental pollutants. The possible effect of the interaction between nitrogen oxides and the stratospheric ozone layer is a global concern. There are also environmental problems, of local to regional character, in relation to nitrogen that deserve attention, such as the contamination of ground water by heavy applications of nitrogen fertilizer, thus making drinking-water from these sources unfit for human consumption. Increased levels of nitrogen in air and precipitation are creating changes in the atmospheric chemical climate, one result of which being eutrophication of the environment. The acidification of rain-water by nitrogen oxides is another example of the environmental consequences of nitrogen use.
Ingestion of nitrates in drinking water has long been thought to be a primary cause of acquired infantile methemoglobinemia, often called blue baby syndrome. However, recent research and a review of historical cases offer a more complex picture of the causes of infantile methemoglobinemia. Gastrointestinal infection and inflammation and the ensuing overproduction of nitric oxide may be the cause of many cases of infantile methemoglobinemia previously attributed to drinking water nitrates. If so, current limits on allowable levels of nitrates in drinking water, which are based solely on the health threat of infantile methemoglobinemia, may be unnecessarily strict.
The investigator of phosphorus and its role in the environment is well served by a large body of data covering all aspects of the subject and spanning the natural, earth and life sciences as well as the technologies of mining, manufacture and agriculture. There are two general texts devoted solely to phosphorus and the environment[1, 2] and a detailed chemistry of phosphorus, including its environmental and biochemical roles is also available [3].
Nitrogen compounds are produced from atmospheric dinitrogen (N2) by the following processes:(1) naturally occurring biochemical reactions (biological dinitrogen fixation); (2) naturally occurring abiological reactions (ozonation and combustion, e. g., via fire, lightning, and coronal discharges); and (3) anthropogenic abiological reactions (combustion and industrial synthesis).