Production of bioethanol from crop residues such as wheat straw, has been considered as a viable approach to meet the ever increasing demands for energy without affecting our environment. However, lignin hinders the success of efficient production of bioethanol as it confers recalcitrance of lignocellulosic biomass to hydrolysis. Genetic modification of plant biomass lignin content or composition without affecting its agronomic functions, can reduce biomass recalcitrance, however, application of this strategy requires a detailed understanding of the molecular mechanisms underlying lignin synthesis. This thesis performed comprehensive analysis of the expression of wheat lignin biosynthesis candidate genes and identified genes that are predominant across different tissues. Using three commercial wheat cultivars that exhibit variation in stem resistance to lodging, it investigated the association of expression of these predominant genes with tissue lignin content. Furthermore, this identified transcriptional changes mediating the response of lignin biosynthesis in wheat to changes in soil moisture. / May 2015