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Rhizobium species involved in root nodule formation on legume plants are one of the best known groups of micro organisms. The Rhizobium legume symbiosis continues to be of strategic importance particularly in the context of food production. As the world population grows, it is also neces sary to have new developments taking place in crop improve ment. The development and application of new technologies in biological sciences over the past number of years have made the entire area of plant-microbial interaction an exciting and challenging research area to be involved in. In view of the importance of symbiotic nitrogen fixation, it is not surpris ing that it still represents one of the priority areas for commercial development in agricultural biotechnology. Since this symbiosis involves an association between procaryotic and eucaryotic partners, it requires of necessity a co-ordinated and interdisciplinary approach. It was in this spirit that this international conference was organised. The scientific programme was designed to focus on physio logical limitations affecting symbiotic nitrogen fixation and the potential for overcoming such limitations using genetic technologies. Participants were drawn from contractants of the EEC DGVI "Energy in Agriculture" nitrogen fixation prog ramme. The scientific programme was also supplemented with invited scientists from Europe and North America to provide appropriate expertise on the various conference topics.
List of contents
Section I: Physiological Factors Affecting Nitrogen Fixation.- The influence of host plant energy supply on nitrogen fixation.- Carbon metabolism and the exchange of metabolites between symbionts in legume nodules.- Bacterial catabolism of nitrogen containing compounds in symbiotic nitrogen fixation.- Studies on the Rhizobium-pea symbiosis: The role of malate dehydrogenase and the effect of the plant on the efficiency of the nitrogenase reaction.- Energetics of symbiotic nitrogen fixation: The relationships between oxygen, malate and hydrogen.- Rhizobium strain effect on nitrogen accumulation in pea relates to PEP carboxylase activity in nodules and asparagine in root bleeding sap.- Flavanoid-Rhizobium interactions.- Peribacteroid membrane stability and phytoalexin production in legume nodules.- Section II: Environmental Factors Affecting Nitrogen Fixation.- Limitations and benefits of oxygen diffusion control in legume nodules.- Factors controlling legume nitrogen fixation and their measurement in the field.- Inhibition of symbiotic nitrogen fixation by nitrate.- Variations in nodulation ability by strains of R. trifolii in the presence of nitrate.- Positive and negative aspects of denitrification in Rhizobium-legume associations.- Competition between nodulating and non-nodulating Rhizobium strains: Delay of nodulation.- Effect of soil pH on nitrogenase activity, crop yield and Rhizobium multiplication.- Section III: Genetics of Nitrogen Fixation.- Dicarboxylic acid utilisation and nitrogen fixation efficiency in Rhizobium-legume symbiosis.- Regulation of nitrogen fixation in the Rhizobium meliloti-alfalfa symbiosis.- Structure and regulation of fix genes from Rhizobium meliloti.- Organization and expression of hydrogen-uptake (hup) genes of Rhizobium leguminosarum.- Two classes of Rhizobium genes required for the nodulation of legumes.- The role of nodulins in root nodule development.- Author Index.- List of Participants.
