Date of Award


Document Type

Honors Thesis



First Advisor

Dr. Karen L. Koster

Second Advisor

Dr. Bernard W. M. Wone

Third Advisor

Kumudu N. Rathnayake


Physcomitrella patens, dehydration tolerance, chlorophyll fluorescence, ecotypic variation, ‘Gransden’, ‘Villersexel'


Plant tolerance of environmental stresses such as water deficit depends on genetic factors that can vary in response to the climate in which the plants have evolved. Such genetically distinct populations of a species that live in different regions are referred to as ecotypes. The purpose of this research was to test the dehydration tolerance of two ecotypes of the moss species Physcomitrella patens, one from Little Gransden, England, which has been used for decades for research, and another more recently cultured ecotype from Villersexel, France. Little Gransden receives nearly half the yearly precipitation of Villersexel, which could have led to the ‘Gransden’ ecotype becoming more dehydration tolerant than the ‘Villersexel’ ecotype. To test my hypothesis, I allowed samples containing contained both protonemata and gametophores of each ecotype to equilibrate to a range of relative humidities (RH), measured the extent of dehydration they experienced, and then assessed their ability to survive dehydration using chlorophyll fluorescence as a measure of metabolic recovery after rehydration. The data indicate that the ‘Gransden’ ecotype survived and recovered from equilibration to RH as low as 89% RH, while the ‘Villersexel’ ecotype was less tolerant of dehydration, only surviving equilibration down to 95% RH.



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