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Thesis Abstract – Walker (2007)


Phenotypic Plasticity of Coastal Sage Scrub and Nursery Herbs Under Varying Water Availability

Author and college:

Katelyn Walker, Harvey Mudd College


April 25, 2007


Bachelor of Science in Biology


Stephen Adolph, Harvey Mudd College


Leaf biomass per photosynthetic area (LMA) is one way to quantitatively measure resource allocation in plants. In this experiment, I examine the phenotypic plasticity of LMA under varying water conditions for seven species: Heterotheca grandiflora, Marrubium vulgare, Centaurea solstitalis, Digitalis purpurea, Rudbeckia hirta, and Ocimum basilicum. These species are representative of three families, have varying life spans, and come from two habitats, which allowed me to compare plasticity of LMA across these life history traits. I hypothesized that LMA is a derived trait which is predicted by environment, not by taxonomy. I predicted that LMA would be more plastic in species taken from coastal sage scrub habitat, which has highly variable inter-annual rainfall, as compared to species available from seed in a nursery. However, I observed no pattern of LMA plasticity in any of the groups studied in this experiment. Although LMA is capable of plasticity, it is one of many traits which are plastic under variable water conditions. Thus, it seems that every species has a different combination of plastic traits which allow it to adapt to variation in water availability.

For more information:

Contact Stephen Adolph – stephen_adolph@hmc.edu

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