Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Biology

Committee Chair

Jonathan Cumming

Committee Co-Chair

Stephen DiFazio

Committee Member

Jennifer Hawkins

Abstract

As the world population continues to increase, so does the need for sustainable sources of fuel. Biofuels are of particular interest and could be an economically feasible fuel source given the right conditions. Populus trichocarpa, is a rapidly growing plantation species that, in addition to having a fully sequenced genome available for study, displays a wide range of phenotypic traits among genotypes. By analyzing these differences in both plantation and more controlled greenhouse settings, we aimed to discover which genotypes performed the best under drought conditions, and which physiological mechanisms granted them that high performance. In the field, differences in heights and stress tolerance among genotypes were observed, and 60 genotypes of differing water-limitation resistance were selected for further measures. No differences between resistance groups were seen in the physiological measures taken, yet the more resistant genotypes had higher stress tolerances indices and grew taller than susceptible genotypes from similar latitudes. The greenhouse study confirmed the water-limitation resistance rankings for 80% of the genotypes and found that resistant genotypes expressed greater midday stomatal control, enabling them to conserve water. Despite this temporary shutdown to photosynthesis, resistant genotypes assimilate carbon at a higher rate than the susceptible genotypes and can maintain their growth advantage. The quick response rate to water-limited conditions correlates with latitude and water availability of the collection site for the clones, suggesting that clones that do not regularly experience water-limitation are more sensitive to it and are able to make short-term adaptations to avoid such conditions. Further evaluation will be needed to examine if these short-term adaptations can maintain growth over extended periods of drought or on marginal lands in order for these genotypes to be a viable candidate for a rotational crop used for biofuel production.

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