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Newcastle University (2015)

Exploiting the potential of Agave for bioenergy in marginal lands

Al Baijan, Dalal B. A. S

Titre : Exploiting the potential of Agave for bioenergy in marginal lands

Auteur : Al Baijan, Dalal B. A. S

Université de soutenance : Newcastle University

Grade : Doctor of Philosophy (PhD) 2015

Résumé partiel
Drylands cover approximately 40% of the global land area, with minimum rainfall levels, high temperatures in the summer months, and they are prone to degradation and desertification. Drought is one of the prime abiotic stresses limiting crop production. Agave plants are known to be well adapted to dry, arid conditions, producing comparable amounts of biomass to the most water-use efficient C3 and C4 crops but only require 20% of water for cultivation, making them good candidates for bioenergy production from marginal lands. Agave plants have high sugar contents, along with high biomass yield. More importantly, Agave is an extremely water-use efficient (WUE) plant due to its use of Crassulacean acid metabolism. Most of the research conducted on Agave has centered on A. tequilana due to its economic importance in the tequila production industry. However, there are other species of Agave that display higher biomass yields compared to A. tequilana. These include A. mapisaga and A. salmiana and A. fourcroydes Lem has been reported to possess high fructan content making it a promising plant for biofuel feedstock. Also, fructans act as osmo-protectants by stabilizing membranes during drought and other abiotic stress. This project set out to examine several hypotheses. In the first experimental chapter (Chapter 2), the central aim was to start identifying traits for the improvement of Agave species for biomass production on arid lands by first examining if the capacity of CAM, and fructan accumulation are linked traits. To address this question 3 species of Agave varying in succulence were compared under different water regimes. Measurements were made of leaf, gas exchange and titratable acidities as markers of CAM and of soluble sugar and fructan content using high performance liquid chromatography (HPLC). High leaf succulence is associated with increased magnitude of CAM, manifested as higher H+ and nocturnal CO2 uptake and fructan accumulation also increased with leaf succulence in Agave. Sucrose provided most, if not all of the substrate required for dark CO2 uptake. At the leaf level, highest CAM activity was found in the tip region whilst most fructan accumulation occurred in the base of the leaf. These results indicate that CAM and fructan accumulation are subject to contrasting anatomical and physiological control processes. v In Chapter 3, the aim was to test 4 hypotheses relating to succulence and biochemical capacity for C3 and C4 carboxylation in Agave.

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