The response of understory species to elevated temperatures is not well understood but is important because these plants are highly sensitive to their growth conditions. Three-year-old plants of Panax quinquefolius, an understory herb endemic to the eastern deciduous forests of North America, were grown in a greenhouse at 25/20°C (day/night) or 30/25°C for one growing season and analyzed each month. Plants grown at high temperatures had an early onset of leaf senescence and therefore accumulated less carbon. From May to July, P. quinquefolius grown at high temperatures had decreased photosynthesis (52%), stomatal conductance (60%), and root and total biomass (33% and 28%, respectively) compared to plants grown at low temperatures. As P. quinquefolius prepared to overwinter, plants grown at high temperatures had less root biomass (53%) than plants in low temperatures. The amount of storage-root ginsenosides was unaffected by temperature, and differences in storage root size may explain why plants grown at high temperatures had greater concentrations of storage root ginsenosides (49%) than plants grown at low temperatures. Panax quinquefolius is clearly sensitive to a 5°C increase in temperature, and therefore other understory species may be negatively impacted by future increases in global temperature.
Effects of elevated temperature on Panax quinquefolius ecophysiology and pharmacological activity on human breast MCF-7 carcinoma cells Gera M. Jochum The purpose of this study was to determine the effects of increased temperatures associated with climate change on an understory medicinal herb, Panax quinquefolius. Three-year old P. quinquefolius were grown in a greenhouse at low (25°C day/20°C night) or elevated (30°C /25°C) temperatures for one growing season. Elevated temperatures decreased photosynthesis and accelerated leaf senescence. At the end of the growing season, biomass was detrimentally affected by increased temperatures; yet the concentration of root ginsenosides, secondary metabolites thought to be the primary pharmacological components, was higher in plants grown in the elevated temperature treatment than in plants grown in the low temperature treatment. Changes in the pharmacological activity of these extracted ginsenosides were determined by treating estrogen receptor-positive human breast cancer MCF-7 cells with known concentrations of total ginsenosides. Extracts from plants grown in the low temperature treatment were effective at lower concentrations and were overall more effective at decreasing the number of MCF-7 cells than extracts from plants in the elevated temperature treatment. This response was consistent for extracts harvested early and late in the season. Increased global air temperatures associated with climate change may have important implications for the ecology and pharmacological activity of sensitive understory herbs. iii ACKNOWLEDGEMENTS There are many people who deserve recognition for helping me to complete this work. Of course, none of my work would have been possible without the guidance of my advisor, Dr. Richard Thomas. I am very grateful that he gave me the freedom and support I needed in order to conduct this research. I need to thank Dr. Christy Foran, who inspired me to cross over into the molecular realm of cancer research; Dr. Mike Miller, who made the cancer project possible; Dr. Jim McGraw, who led me to this research indirectly through my undergraduate experience as a field technician in his lab; Dr. Bill Peterjohn for answering countless questions; and Dr. Ken Mudge and his colleges at Cornell University for opening their lab and equipment to me for the ginsenoside analysis. I would also like to acknowledge Dr. Clint Springer, Rebecca Merrit, and Maricica Pacurari for teaching me the techniques to complete this work. The graduate student body has been a tremendous source of support and I am very thankful to them, as well as to the biology staff. This list wouldn't be complete without thanking Bob Rounsley, who in addition to being a great laboratory technician any time I needed him, was a large part of my foundation throughout this period. Lastly, I need to thank my parents, Jack and Karen Jochum, for inspiring me to always better myself. iv
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