Abstract

The Leaf Economics Spectrum (LES) describes the continuous range of leaf ecophysiological strategies that plants across the globe utilize to achieve a net-positive return on their resource investment. This spectrum is measured by traits such as leaf mass per area, leaf nitrogen, and leaf lifespan. Unsuitable leaf trait combinations are selected against in nature due to a net-loss on the return of initial resource investment, while some potentially extremely effective trait combinations may not be possible due to genetic constraints. Existing genetic variation in LES traits, however, suggests the spectrum may be less rigid than previously expected. To test this, we exploit phenotypic plasticity by subjecting cultivated sunflower, Helianthus annuus, to environmental stress to generate variability in LES traits. In a greenhouse experiment, treatment groups of Helianthus were exposed to six varying intensities each of four acute stress applications: nutrient limitation, high soil salinity, heat, and simulated herbivory. Leaves formed during the onset of stress and post-stress were sampled to measure leaf traits; changes in plant fitness were estimated through total plant biomass and the time of first flowering. Results from statistical analyses show a variety of significant effects that stress applications had on plant growth and LES traits. Our findings explore the possibility of achieving off-axis LES trait combinations through salt-induced trait plasticity, and if further studies are needed to reassess the rigidity of the spectrum.

Thesis Completion

2021

Semester

Spring

Thesis Chair

Mason, Chase

Degree

Bachelor of Science (B.S.)

College

College of Sciences

Department

Biology

Degree Program

Biology

Language

English

Access Status

Open Access

Release Date

11-1-2021

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