The major goal of this project was to identify regulators of leaf senescence in barley leaves that are important for initiation and progression of the process in the field. The results reveal distinct differences between barley varieties in the sequence of degradation of stroma- and grana thylakoids under different conditions. It could be shown that nitrogen availability plays a major role in regulation of these processes. In addition, changes in gene expression during senescence under different nitrogen-supply conditions were analyzed using a novel barley microarray. This approach allowed the identification of barley genes involved in developmental and nitrogen dependent senescence. Interesting candidates are genes encoding factors involved in protein degradation and transcription factors, especially of the NAC and WRKY families. On top of regulation of environment-sensitive leaf senescence via transcription factors, there is another regulatory level, the epigenetic control. To include this new view in our study of barley leaf senescence, 57 barley genes, which encode putative epigenetic control factors, were identified and changes in expression of these genes during leaf senescence were analyzed. Interestingly, genes encoding specific epigenetic control factors as histone deacetylases, histone methyltransferases and chromatin remodelers were differentially regulated during senescence. Our data reveal that leaf senescence, which is important for quality and quantity of grain yield, is regulated at different levels in an environment-sensitive way.