Undergraduate Honors Theses

Thesis Defended

Spring 2013

Document Type



Ecology and Evolutionary Biology

First Advisor

Dr. Barbara Demmig-Adams


Zeaxanthin is a carotenoid produced by plants for protection against photo-damage and supports human vision and health when consumed with the human diet. Zeaxanthin in plants is accumulated and retained most strongly (i) under harsh, growth-retarding conditions and (ii) by inherently slow-growing plants. By selecting for maximal biomass production, modern agriculture may have inadvertently selected for nutritionally suboptimal plants. This thesis explores whether zeaxanthin retention can be triggered by mild light stress without concomitant decreases in biomass production, and whether different plant varieties respond differently. Two ecotypes of Arabidopsis thaliana adapted to biogeographic extremes of this species’ distribution (Italy and Sweden) were grown in the presence of mild light stress and assayed for zeaxanthin content and retention, plant photo-protection capacity against damage by intense light, and biomass. When grown under mild light stress, only the Swedish ecotype retained zeaxanthin, suggesting heightened responsiveness of the Swedish ecotype to subtle environmental triggers. In addition, the Swedish ecotype demonstrated a greater ability than the Italian ecotype to rapidly form additional zeaxanthin when exposed to an experimental treatment with very high light levels. It can be concluded that both moderate changes in environmental conditions and selection of plant variety can serve to augment plant zeaxanthin content without compromising biomass production.