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Physiology and Dormancy of the Aquatic Angiosperm Potamogeton Crispus L

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Physiology and Dormancy of the Aquatic Angiosperm Potamogeton Crispus L PHYSIOLOGY AND DORMANCY OF THE AQUATIC ANGIOSPERM POTAMOGETON CRISPUS L. TURIONS A DISSERTATION SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY Deborah “Jo” Heuschele IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Advisor: Dr. Florence Gleason December 2013 © D. Jo Heuschele 2013 Acknowledgements This work was sponsored by-grant in-aid from the University of Minnesota and Aquatic Plant Management Society’s Graduate Student Grant. Additional support was provided by the University of Minnesota Plant Biology and Graduate School. I am grateful to R. Newman, T. Smith, D. Gilpin and O. Heuschele for their assistance in field collection. Many unique conversations and bird watching events occurred during those collection trips. A special thanks to Dwayne Albee and Diane Gilpin for the use of their boats “Little Brown Floater” and “John Boat”. Without their use collecting of turions would not have been possible. I would like to thank the members of my committee, Florence Gleason, Neil Olszewski, Adrian Hegeman, Jerry Cohen, and Ray Newman for their suggestions, comments, and general assistance. I would especially like to thank Florence for writing guidance and multiple reviews. Thank you to my father who kept reminding me that good science is not limited to the “Ivory Tower” of academia. I am very grateful to Otto, Octavia, Opal and Joel for their patience, and support. Do not worry; Mami will still take you out on boats looking for invasive species. i Dedication This dissertation is dedicated to my family; Joel, Otto, Octavia, and Opal. Their patience and tolerance these last five years has been appreciated. Also, I would like to dedicate this work to Christ. This project would not have gotten done without divine intervention. ii Comprehensive Abstract Vegetative buds (turions) are the major source of propagation for the aquatic invasive angiosperm, Potamogeton crispus L. (Potamogetonaceae). An understanding of the regulation of turion dormancy could lead to better methods of population control. The majority of Potamogeton crispus turions remain dormant over the summer and sprout in the autumn, while a small subset of turions remain dormant for an unspecified time. Hormonal control of dormancy in aquatic plant vegetative propagules is not well understood. For this study turions were divided into two different age groups, newly formed (current season) and older than one year (overwintered). The effect of varying light durations and temperatures on sprouting was monitored in these different groups. Non-structural carbohydrates, photosynthesis, and aerobic respiration were measured to determine metabolic activity. We also measured abscisic acid concentrations and sprouting levels in turions that were exposed to various hormones, temperatures, and light durations to elucidate hormonal control of dormancy. Current season turions were found to sprout mainly in response to day length and were metabolically active over a 6 week period. They are in a semi-dormant state and 60-70% will sprout in the autumn. The remaining current season turions presumably go into a state of deep dormancy and remain dormant over the winter. Turions that have overwintered are not photosynthetically active, have stable carbohydrate levels, and can remain dormant but viable for several years. Under laboratory conditions, they sprouted mainly in response to an increase in water temperature. These different age groups correspond to different turion physiological states and can explain sprouting variability recorded by other iii researchers. Current season turions produce and sprout in response to changes in ABA levels. A reduction of ABA in new turions is correlated with the breaking of dormancy. Overwintered turions do not sprout in response to ABA or GA changes. The results indicate two different pathways utilized by P. crispus turions to maintain and break dormancy. iv Table of Contents Acknowledgements………………………………………………………………...i Dedication...……………………………………………………………………….ii Comprehensive Abstract………………………………………………………….iii List of Tables……………………………………………………………....……viii List of Figures…………………………………………………………...………..ix Prologue …………………………………………………………………………..1 Chapter 1 - Asexual Reproduction in Freshwater Aquatic Angiosperms ............... 4 General Characteristics of Vegetative Propagules ...................................... 6 Ecology ....................................................................................................... 8 Propagule Development ............................................................................ 10 Dormancy .................................................................................................. 13 General Conclusions ................................................................................. 15 Potamogeton crispus L. ............................................................................ 16 Chapter 2 - Regulation of Turion Dormancy in Potamogeton crispus L. ............. 32 Introduction ............................................................................................... 33 Materials and Methods .............................................................................. 35 Turion Collection .......................................................................... 35 Turion Sprouting Conditions ........................................................ 36 Glucose and Starch Analyses ........................................................ 37 Chlorophyll and Tannin Analyses ................................................ 38 Photosynthesis and Respiration Rates .......................................... 39 Statistics ........................................................................................ 39 Results ....................................................................................................... 40 Turion Sprouting ........................................................................... 40 Glucose and Starch Content .......................................................... 41 Chlorophyll a and Tannin Content ................................................ 42 Photosynthesis and Respiration Rates .......................................... 42 Discussion ................................................................................................. 43 v Conclusion ................................................................................................ 47 Connection between Chapters ............................................................................... 58 Chapter 3 - Hormonal Control of Dormancy of Potamogeton crispus L. Turions 59 Introduction ............................................................................................... 60 Material and Methods ............................................................................... 62 Adult Potamogeton crispus ........................................................... 62 Turions .......................................................................................... 63 Sprouting Assays .......................................................................... 64 Abscisic Acid Measurements ........................................................ 65 Synthesis of 2H – ABA ................................................................. 67 Results ....................................................................................................... 67 Adult Plants ................................................................................... 67 Current Season Turions................................................................. 67 Overwintered Turions ................................................................... 70 Discussion ................................................................................................. 72 Turion Formation .......................................................................... 72 Current Season Turions................................................................. 73 Overwintered Turions ................................................................... 80 Conclusion ................................................................................................ 83 Chapter 4 - Concluding Remarks .......................................................................... 98 Summary…………………………………………………………98 Management Implications……………………………………….99 Future Directions…………………………………………….…100 References ........................................................................................................... 106 Appendix A - Turions Formation During Flooding ............................................ 118 Purpose .................................................................................................... 118 Materials and Methods ............................................................................ 118 Results ..................................................................................................... 118 Discussion ............................................................................................... 119 vi Appendix B - Turion Storage Verification ......................................................... 126 Purpose .................................................................................................... 126 Materials and Methods ............................................................................ 126 Results ..................................................................................................... 126 Discussion
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