Plant-soil-microbe interactions in phytomanagement systems: Influences of cadmium and nitrogen on rhizosphere microbial communities and growth of native plant species in agricultural systems

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Phytomanagement and Farming systems are of increasing importance throughout the world. In the present study, poplar and willow plants will be combined with native plant species, to further improve farm management systems. Two common contaminants (Cadmium and Nitrogen) with relevance to agricultural systems have been chosen to investigate the plants in terms of phytoremediation and its accumulation efficiency in contaminated agricultural soil. Since plant-microbe interactions play a major role in phytomanagement systems, one focus will be on microbial community shifts in the rhizosphere of plants growing on contaminated soil. To assess such changes in a plant specific microbial community structure, phospholipid fatty acids (PLFA) will serve as an adequate tool, since they are present in all living cells and rapidly degraded after cell death. Results will be compared with DNA based microbial community profiling. Furthermore, terpene, flavonoid and lipid analyses of plant tissue will provide insight into physiological shifts of plants in response to the different contaminants. A 13CO2 pulse applied to the experiment before harvest will provide further investigations of physiological shifts within plant metabolism and carbon translocation into the rhizosphere with respect to the contaminant. In this context, stable isotope probing of PLFA and DNA will be compared, and further 13C analyses of plant tissues carried out. To address the focus of phytomanagement systems, further analyses of plant parts (roots, stem, leaves, fruit and seeds) will be analysed for Cadmium and Nitrogen content. Highly contaminated plant tissues may be burned for biogas production and subsequently composted for recycling. Plant parts with high Nitrogen contents but no significant increase in Cadmium can be used as fodder material during winter periods; the use for commercial purposes may be possible and will be addressed within the present research proposal.