Honors College Theses

Publication Date



Biology (B.S.B.)

Document Type and Release Option

Thesis (open access)

Faculty Mentor

Edward B Mondor


Atmospheric changes, associated with global climate change, are increasing at an unprecedented rate. Plants generally display higher rates of growth in response to elevated CO2 levels, but this response varies among species. In addition, very little is known about how plant growth/defense tradeoffs will be altered by increasing CO2 levels. By raising Broad bean, Vicia faba L., plants under ambient (400 ppm) and elevated (900 ppm) levels of CO2, it was shown that atmospheric composition directly altered plant growth/defense tradeoffs. Plants grown under elevated CO2 had lighter stem weights but greater numbers of extrafloral nectaries and higher rates of extrafloral nectar secretion. Thus, plants grown under elevated CO2 invested more in defense (extrafloral nectaries and extrafloral nectar production) than growth (biomass). These results indicate that CO2 may act as a stressor for Broad bean plants.