Pearlman, Ryan , Walls, Ramona .
Larger-leaved Dioscorea species are able to maintain photosynthetic capacity under higher temperatures than smaller-leaved species.
The purpose of this research was to test the ability of leaves of various species of wild yams (Dioscorea) to tolerate heat stress. Dioscorea is a genus with over 400 species that is native to both tropical and temperate regions, but is predominantly tropical. This study focused on 11 species of Dioscorea from both tropical and temperate regions, grown in a common greenhouse environment. Heat tolerance was determined by measuring steady state fluorescence of detached, dark-adapted leaves subject to a temperature increase of 1 degree C per minute. The critical temperature (Tcrit) was calculated as the temperature at which fluorescence begins to rise sharply. This is the temperature at which chloroplast membranes begin to break down and photosynthesis begins to decline rapidly. Tmax, the temparature at which fluorescence reaches a maximum, was also measured. Above this temperature, photosynthetic machinery no longer functions, and leaves quickly lose their ability to absorb and re-emit photons. Phylogenetically independent contrasts were used to examine the correlations between Tcrit and Tmax and between heat tolerance and leaf size. Tcrit and Tmax were highly correlated among species. Species with large leaves had a higher Tcrit, and thus appear to be able to tolerate high temperatures better than species with smaller leaves. This is consistent with large leaves having a thicker boundary layer than smaller leaves, which would lead to larger leaves regularly experiencing higher temperatures. This study provides the first evidence of selection for large leaves to have a constitutive ability to tolerate higher temperatures than small leaves.
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1 - Stony Brook University, Ecology and Evolution, 650 Life Sciences, Stony Brook, NY, 11794-5245, USA
2 - Stony Brook University, Ecology and Evolution, 650 Life Sciences Building, Stony Brook, New York, 11794-5245, USA
Presentation Type: Poster:Posters for Topics
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM