Document Type


Date of Degree Completion

Spring 2018

Degree Name

Master of Science (MS)



Committee Chair

Jennifer Dechaine

Second Committee Member

Mary E. Poulson

Third Committee Member

Alison G. Scoville


Historically agriculture has met global food production demands, but abiotic stresses are predicted to decrease crop yield in the context of climate change. In order to prevent losses in crop yield under conditions of increasing environmental stress and to reduce environmental damage from unsustainable farming practices, improvements must be made in crop breeding and bioengineering. However, these improvements require insight into the mechanisms of abiotic stress resistance. In this study, 60 different genetic sunflower (Helianthus annuus) lines were grown in the field under fertilized and unfertilized treatments to assess phenotypic traits associated with low nutrient stress resistance. Sunflowers were assessed for stress resistance using height, stem diameter, biomass, and root structure traits. Sunflowers responded to nutrient stress through a decrease in overall size and increased root width near the surface and steeper lateral root angles. Height, stem diameter, biomass, root mass, root area, and root density were found to be correlated with nutrient stress resistance. Overall plasticity of sunflowers was also found to be correlated with nutrient stress resistance. Root width allocation, root mass, root area, root density, and plasticity should be studied further for their potential to improve crop breeding and bioengineering efforts.