Clemson University TigerPrints All Dissertations Dissertations 12-2007 Enhancing the ability of Panicum virgatum to survive flooding and its effects on soil activity when used for lakeshore stabilization Lee Edwards Clemson University, [email protected] Follow this and additional works at: https://tigerprints.clemson.edu/all_dissertations Part of the Plant Biology Commons Recommended Citation Edwards, Lee, "Enhancing the ability of Panicum virgatum to survive flooding and its effects on soil activity when used for lakeshore stabilization" (2007). All Dissertations. 146. https://tigerprints.clemson.edu/all_dissertations/146 This Dissertation is brought to you for free and open access by the Dissertations at TigerPrints. It has been accepted for inclusion in All Dissertations by an authorized administrator of TigerPrints. For more information, please contact [email protected]. ENHANCING THE ABILITY OF PANICUM VIRGATUM TO SURVIVE FLOODING AND ITS EFFECTS ON SOIL ACTIVITY WHEN USED FOR LAKESHORE STABILIZATION A Dissertation Presented to the Graduate School of Clemson University In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Plant and Environmental Sciences by Joan Lee Edwards December 2007 Accepted by: Dr. Larry A. Dyck, Committee Chair Dr. Melissa B. Riley Dr. Tom McInnis Dr. Christina E. Wells ABSTRACT Reservoirs in upstate South Carolina are subject to erosion and vegetation has been placed to help stabilize banks, but soils are nutrient-poor and have high bulk densities. Panicum virgatum L. (switchgrass) has been planted in several sites, and it is hypothesized that over time, changes in microbial activity and soil quality will occur in response to the planting. As vegetated sites aged, acid phosphomonoesterase, nitrate reductase, and dehydrogenase activity increased. Low values of nitrogen fixation and substrate-induced respiration were measured at all sites with no statistical differences between sites. Fatty acids indicative of Gram negative bacteria were found in vegetated sites and the diversity of fatty acids increased in vegetated sites indicating more diverse microbial communities. Switchgrass plants may experience periods of flooding resulting in ethylene production. Switchgrass plants were placed in a modified Hoagland’s solution and treated with an ethylene producer and ethylene inhibitor to determine morphological responses. Ethylene treatment resulted in increases in the number of adventitious roots. No effects were observed on aerenchyma development, shoot elongation, root length, average root diameter, root system volume, or root surface area. Switchgrass therefore does not appear to be sensitive to ethylene which may be produced in response to flooding resulting in no effect on switchgrass growth. Serratia ficaria, an ACC deaminase bacterium, was isolated from lakeshore soils and then added to switchgrass seeds/young plants to determine its effect as a plant growth-promoting bacterium (PGPB) under three different water regimes. Treatments ii inoculated with bacteria had increased root to shoot ratios in unflooded and completely submerged water regimes, but the opposite was true for crown-flooded treatments. Shoot growth was fastest in inoculated treatments, except for completely submerged treatments, where values were not statistically different between inoculated and uninoculated groups. The bacterium was beneficial when there is no water stress, but became detrimental when water levels rose until submergence Overall switchgrass appears to increase microbial activity and diversity over time, has limited response to ethylene due to flooding, and is able to grow in soils with minimal nutrients making it a good plant for use in lakeshore stabilization along Lake Hartwell. iii DEDICATION I absolutely could not have completed this program without the love and support of my husband, Rick Edwards. He is my anchor in the storm and the best friend I could ever wish for. I love you will all my heart and look forward to the rest of our lives together. I dedicate all the hard work it took to complete my Ph.D. to you. iv ACKNOWLEDGMENTS I want to express my sincere appreciation to my committee for guiding me through my Ph.D. program. My major advisor, Dr. Larry Dyck, is one of the best teachers I know. He has shown me not only to appreciate the details, but also to fit those details into the “big picture”. I have learned so much from him, and I know I will look at the world differently from now on. Without Dr. Lissa Riley I would never have completed the research and the writing of this dissertation. I can never thank her enough for the moral support and guidance she gave me and the countless hours she spent revising these chapters. I want to thank Dr. Christina Wells for opening up her lab to me and allowing me to use whatever I needed. She always made me feel like part of her lab team, and I appreciate her hospitality. Dr. Tom McInnis was always a supportive committee member and I valued his thoughts on the approach I should take with my research. I enjoyed and learned so much from the classes I took from him. Those classes gave me a very strong basis for this research. v TABLE OF CONTENTS Page TITLE PAGE....................................................................................................... i ABSTRACT......................................................................................................... ii DEDICATION..................................................................................................... iv ACKNOWLEDGEMENTS................................................................................. v LIST OF TABLES............................................................................................... viii LIST OF FIGURES ............................................................................................. ix CHAPTER 1. LITERATURE REVIEW..................................................................... 1 Bank Stabilization of Lake Hartwell............................................... 1 Switchgrass. .............................................................................. 5 Enzymatic Activity of Soils............................................................ 8 Dehydrogenase Activity............................................................ 8 Substrate-induced Respiration.................................................. 9 Acid Phosphomonoesterase Activity........................................ 10 Nitrate Reductase Activity........................................................ 11 Nitrogen Fixation...................................................................... 12 Fatty Acid Methyl Ester Analysis............................................. 13 Ethylene Involvement in Plant Growth........................................... 15 Ethylene’s Effect on Different Plants ....................................... 16 Ethylene Inhibitors and Promoters............................................ 18 Plant Growth-Promoting Bacteria................................................... 19 Lowering Ethylene Concentration by PGPB ............................ 19 Evidence for the model ............................................................. 20 Ethylene and IAA Exposure ..................................................... 22 Literature Cited............................................................................... 24 vi 2. SITE MODIFICATION AND ITS EFFECTS ON ENZYMATIC ACTIVITY OF SHORELINE SOILS ON LAKE HARTWELL............................................................................. 35 Abstract........................................................................................... 35 Introduction..................................................................................... 37 Materials and Methods.................................................................... 44 Results............................................................................................. 57 Discussion....................................................................................... 62 Literature Cited............................................................................... 76 3. EFFECTS OF ETHYLENE ON THE MORPHOLOGICAL CHARACTERISTICS OF PANICUM VIRGATUM. .............................. 94 Abstract........................................................................................... 94 Introduction..................................................................................... 95 Materials and Methods.................................................................... 101 Results............................................................................................. 104 Discussion....................................................................................... 106 Literature Cited............................................................................... 110 4. THE IMPACT OF SERRATIA FICARIA ON THE GROWTH OF PANICUM VIRGATUM UNDER THREE DIFFERENT WATER REGIMES................................................................................. 117 Abstract........................................................................................... 117 Introduction..................................................................................... 119 Materials and Methods.................................................................... 124 Results............................................................................................. 128 Discussion......................................................................................