Plant cell walls: interactions with nitrogen supply and silicon deposition in Brachypodium distachyon and wheat – Københavns Universitet

Plant cell walls: interactions with nitrogen supply and silicon deposition in Brachypodium distachyon and wheat

PhD defence by Sylwia Emilia Głazowska

Grasses (Poaceae) are an abundant and widespread source of food, feed and energy. Currently, the majority of energy produced worldwide comes from fossil fuels, however, uncertain supply, depletion of know reserves, and concerns over negative environmental impacts associated with use of fossil fuels prompted incorporation of biofuels as an energy alternative. Non-edible agricultural waste residues as well as dedicated energy crops are crucial lignocellulosic feedstocks for sustainable, low-carbon biorefining into fuels, chemicals and other products. The innate resistance of plant cell walls to mechanical damage and degradation with hydrolytic enzymes, defined as recalcitrance, poses major limitation for efficient and cost-efficient use of biomass for biorefining. Biotechnological approaches have been successfully conducted in order to reduce cell wall recalcitrance without compromising plant growth and productivity, however, often drastic changes in cell wall structure lead to increased plant susceptibility to pathogens and abiotic stresses, decreased vigour, growth and productivity. Alternative solutions that can be implemented alongside biotechnological approaches involve modification of plant nutrition practices.

The aim of this PhD thesis was to address if modification of mineral nutrition might be a prospective strategy to alter cell wall recalcitrance. The study focused on nitrogen (N), an essential element that promotes plant growth and productivity. An additional focal point was silicon (Si), a beneficial element which improves plant performance and alleviates biotic and abiotic stresses, but may increase the recalcitrance of biomass to degradation. The impacts of Si, inorganic N form and supply rate on plant performance and cell wall composition were investigated in the grass model plant species Brachypodium distachyon and in the crop species wheat.

The results presented in the PhD thesis confirm that Brachypodium distachyon is a suitable model plant for studies of the importance of nutrient supply for the cell wall composition in grasses. Furthermore, the level and form of nitrogen supply affect the composition of cell walls in lignocellulosic biomass. The same is the case for changes in silicon uptake and deposition. However, the accompanying effects on cell wall recalcitrance towards enzymatic hydrolysis are negligible.

Assessment Committee:

Miroslav Nikolic, Professor, University of Belgrade, Serbia

Pai Rosager Pedas, Senior Scientist, Carlsberg Research Laboratory, Denmark

Henning Jørgensen, (Chairman) Associate professor, University of Copenhagen, Denmark

Supervisor:

Jan K. Schjørring, Professor, University of Copenhagen, Denmark

Reception:

The defence is followed by a reception on the 6th floor in meeting room R660/661