Juliane Frenzel

The influence of the activity of PEP-Carboxylase on the C and N metabolism of poplar (P. tremula x P. alba)

The shortage of fossil resources as well as advancing climate change has led to an increasing interest in regenerative energy sources within the last decade. The energetic utilisation of biomass therefore plays an important role in current calculations of our prospective energy mix. The cooperative project ProBioPa (Sustainable Production of Biomass using Short Rotation Plantations of Poplar on marginal locations) aims to discover to which extent the use of biomass can contribute to a significant reduction of greenhouse gas emission in comparison to fossil energy sources.

In my PhD thesis I focus on two aspects of this project. In one part of the project we compare several commonly bred genotypes in combination with different irrigation and fertilisation regimes. Therefore, we periodically measure gas exchange and VOC emission rates of the poplar plants on our experimental short rotation plantation in Sigmaringen/Baden-Württemberg, Germany. In the other part of the project the focus lies on the optimisation of plant attributes, e.g. improved nitrogen use and reduced trace gas emission (isoprene). This is supposed to be reached by producing transgenic plants which over-express the enzyme phosphoenolpyruvate carboxylase (PEPC). PEPC functions as a metabolic link between nitrogen use efficiency and VOC emission. Its over-expression supposably leads to a stronger emphysis on nitrate assimilation and anabolism in poplar, leaving smaller reserves of the substrate PEP for isoprene emission. Transgenic PEPC lines will be produced and characterised in detail in the course of this project.

Supervisors: Heinz Rennenberg; Jürgen Kreuzwieser; Jörg-Peter Schnitzler (Head of the Department of Environmental Engineering (EUS), Institute of Biochemical Plant Pathology, HelmholtzZentrum München)