FOR 496: Poplar - a model to address tree-specific questions

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The main aim of the Poplar Research Group Germany is to address tree-specific questions with respect to nutrition and adaptation to environmental stresses. Furthermore it is possible to analyse potential interactions between both factors. -- Tree specific questions in respect of nutrition:In forest ecosystems the availability of nitrogen limits the growth of trees and its acquisition in trees is - in contrast to the model plant for annual herbs Arabidopsis - strongly affected by symbiotic interactions with mycorrhizal fungi. Furthermore, regulation of nitrogen nutrition in trees is more complex because of seasonally fluctuating nutrient demand and exposure to changing environmental stresses. By combination of ecophysiological, biochemical and molecular methods the regulation of nitrogen uptake into roots will be studied. These data will be used to create a model of a whole-plant-N-flux. Towards this goal the mechanism of nitrogen transport, the tissue-specific expression and regulation of transport systems and enzymes will be analysed. In addition to nitrogen, phosphorus and potassium are important for growth and wood formation. By use of anatomical, electrophysiological and molecular techniques and by employing microdissection the question will be addressed to which extent the supply with macronutrients influences wood formation. -- Adaptation to environmental stresses:Salinity is a major problem in the world. In the genus Populus, Populus euphratica is outstanding with respect to its salt tolerance. Therefore this model tree offers perfect prerequisites for the Poplar Research Group Germany to study structural, physiological and molecular adaptations to stress. The physiological and molecular basis for salt tolerance will be identified in Populus euphratica. By microarray analyses new candidate genes related to stress-induced changes will be identified. In contrast to herbs poplar trees emit high amounts of isoprene. One potential function of the strong isoprene production in trees is to increase temperature tolerance. Transgenic poplars overexpressing genes of the isoprene biosynthesis pathway will be investigated for thermotolerance. These results can be utilised to obtain trees which are better capable of surviving salt stress and extended heat periods and show better growth under stress conditions.