Poster: Heavy Metals

Abs # 105: The effects of cadmium on photosynthesis of Phaseolus vulgaris

Presenter:	Walley, Justin W., walleyjw@muohio.edu
Authors	Walley, Justin W. (A)   Huerta, Alfredo J. (A)
Affiliations:	(A): Miami University

Numerous studies have demonstrated that exposure of plants to toxic levels of the heavy metal Cd results in a reduction of the net photosynthetic rate. The reduction in photosynthesis following Cd exposure has been attributed to factors such as reductions in stomatal conductance, biosynthesis of chlorophyll, the functioning of photochemical reactions and activity of enzymes associated with the Calvin cycle. One possible explanation for the Cd-induced reduction of net photosynthesis is that Cd reduces stomatal opening, thereby reducing mesophyll CO₂ availability. Alternatively, a Cd-induced reduction in the synthesis or activity of Calvin cycle enzymes could reduce the demand for CO₂, resulting in stomatal closure. To test these contrasting hypotheses, measurements of stomatal conductance, net photosynthetic rate, modulated chlorophyll fluorescence and carbon assimilation response to leaf internal CO₂ concentration (A/Ci) were measured on Cd-treated Phaseolus vulgaris. Results presented should elucidate the mechanism responsible for the reduced photosynthetic rate. The A/Ci measurements will be used to determine stomatal limitations of photosynthesis and changes to photosynthetic carbon fixation capacity. Finally, modulated chlorophyll fluorescence will be used to determine which aspects, if any, of the photochemical reactions are damaged by Cd.