INTRASPECIFIC VARIATION IN GERMINATION OF SCOTCH THISTLE (ONOPORDUM ACANTMUM L.) CYPSELAS by Miwais Mauj Qaderi Department of Plant Sciences Submitted in partial fulfillment of the requirements for the degree of Master of Science Faculty of Graduate Studies The University of Western Ontario London, Ontario August 1998 cb Mirwais Mauj Qaderi 1998 National Library Biiliothbque nationale du Canada Acquisiîiis and Acquisitions et Bibliographie Services seMcas bibliographiques The author has granted a non- L'auteur a accordé une licence non exclusive licence ailowing the exclusive permettant à la National Li'brary of Canada to Bibliothèque nationale du Canada de reproduce, loan, distri'bute or sell reproduire, prêter, disûi'buer ou copies of this thesis m microfom, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/fiLa de reproduction sur papier ou sur format élecîronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiels may be printed or otherwise de celleci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son pexmission. autorisation. Cypselas (seeds) of Scotch thistle, Onopordum acanthium, range from non- dormant to strongly dormant. The effects of environmental factors during tipening and on dispersed but ungerrninated cypselas are not well understood. Through three sets of experiments I investigated how domancy in Scotch thistle cypselas could be affeded. First, conditions under which cypselas matured on the mother plant had a great impact on the onset of dorrnancy. The warmer the conditions the more germinable were the cypselas. Second, cypselas treated with gibberellic acid and potassium nitrate germinated to higher percentages while those treated with sodium bicarbonate germinated to the same or lower percentages. Third, incubation conditions strongly affected germination patterns. Light had no effect on percent germination at 35/20°C but strongly promoted germination at 25/10°C. Thus, both pre- and postdispersal conditions were involved in the germinability of Scotch thistle cypselas. In al1 experiments stn'king differences among locally collected populations were rewrded. Keywords: Scotch thistle, Onopordum acanthium, weed, cypsela, dorrnancy, seed maturation, mother plant, collection time, gibberellic acid, potassium nitrate, sodium bicarbonate, Iight, temperature. CO-AUTHORSHIP The following thesis contains material from research performed by Minvais Qaderi. The papers will be coauthored with my supervisor, Dr. Paul B. Caven. Chapter 5 has been submitted to the Canadian Journal of Botany. Chapters 3 and 4 will be submitted to the Canadian Journal of Botany and Seed Science Research, respectively. DEDICATION To my children Bizhan, Shahnad and Homan. ACKNOWLEOGEMENTS It is my pleasure to acknowledge the following people for sharing their knowledge and love with me and bringing this thesis to completion. I would like to decfare rny great thanks to my supervisor, Dr. Paul B. Caven, who took me to the unlimited land of weed seed ewlogy. Many thanks are also extended to my committee advisors, Dr. Norman P. A. Huner and Dr. M. Anwar Maun for their constructive comments and helpful suggestions thmugh the entire time of rny study. I would like to thank several members of the Department of Plant Sciences for their advice and technical support: Dr. James Phipps, Dr. Jane Bowles, Dr. Jianhua Zhang, Dr. Allan Hamill, Dr. Sheila Macfie, Marguerite Kane, Peter Duenk, Caroline Rasenberg, Daphne Boyce, Magdalena van Hal, Vicky Lightfoot, Erika Mueller, Monika von Dehn, Ron Smith, Alan Noon, lan Craig, Don Yakobchuk, Donna Cheshuk, Stefani Tichbourne and Doreen Beres. I am very grateful to the members of the Department of Zoology, Dr. Roger Green, Dr. Robert Bailey and Dr. Gary Umphrey, for their helpful suggestions with statistical analyses of data and Dr. Terence Laverty and Dr. Stan Caveney for their help with identifying sorne pollinating insects. I am indebted to the following colleagues for their friendship and help: Michael Downs, Randy Manku, AnneMarie Coulombe, Hua Chen, Amy Tsang, Prashant Patil, James Macklin, Kellie White and undergraduate helpers, especially Alexa Seal and Shelley Kilby. Many thanks to Jeff Goossens, Park Programs and Services supervisor at the Upper Thames River Conservation Authority and Gord Tanton, manager of the Stebbins Paving and Construction Limited, for allowing me to use th& properties for cypsela collecting from thistles growing in those areas. Finally, I would like to thank my brother, Hashim Qaderi, for his help in taking thistle pictures and assisting in amputer skills and applications and my wife, Zakera, for her great patience, help and kindness - without her support it would not have been possible to complete this project. vii TABLE OF CONTENTS Page CERTlFlCATE OF EXAMINATION ii ABSTRACT iii CO-AUTHORSHIP iv ACKNOWLEDGEMENTS vi TABLE OF CONTENTS viii LIST OF TABLES xi LIST OF FIGURES xiv LIST OF APPENDICES xv CHAPTER 1 GENERAL INTRODUCTION 1 3.1 VVhat is a weed? 1.2 Life cycles and role of seeds 1.3 Seed dormancy 1.3.7 Domancy mechanisms 1.3.1.1 Embryo dortnancy 7.3.1.2 Coat-imposed dormancy 1-4 Germination requirements 1.5 Seed banks 1.6 Cypsela germination and seedling emergence in Scotch thistle 1.7 Thesis objectives 1.8 References CHAPTER 2 DESCRIPTION OF ONOPORDUM ACANTWIUM L. 13 2.1 Geographical distribution 2.2 Botanical description 2.3 Life cycle viii 2.4 Economic importance 2.4.1 Detrimental 2.4.2 Beneficial 2.5 Methods of control 2.5.1 Mechanical control 2.5.2 Chemical control 2.5.3 Grazing management 2.5.4 Other biological control 2.6 References CHAPTER 3 INTERPOPULATION VARIANCE IN GERMINATION RESPONSES OF CYPSELAS OF SCOTCH THISTLE, ONOPORDUM ACANTHIUM L., MATURED UNDER GREENHOUSE AND FIELD CONDITIONS 3.1 lntroduction 3.2 Materials and methods 3.2.1 Cypsela collection 3.2.1.1 1996 (greenhouse and field) 3.2.7.2 1997 (greenhouse and Md) 3.2.2 Germination tests 3.2.3 Statistical analyses 3.3 Results 3.3.1 Cypsela maturation (greenhouse and field, 1996) 3.3.2 Cypsela maturation (greenhouse and field, 7 99 7) 3.4 Discussion 3.4.1 The mle of temperature during maturation 3.4.2 Seasonal msponses - early versus late 3.4.3 Differences among populations 3.4.4 The germination window 3.5 References CHAPTER 4 INTERPOPULATION VARIANCE IN GERMINATION RESPONSES OF SCOTCH THISTLE, ONOPORDUM ACANTWM L., TO VARIOUS CONCENTRATIONS OF GA,, KNO3 AND NaHCO3 4.1 Introduction 4.2 Materials and methods 4.2.7 Cypsela collecfion 4.2.2 Germination tests 4.2.3 Statistical analyses 4.3 Results 4.3. i The effects of gibberellic acid 4.3.2 The efkcfs of potassium nitrate 4.3.3 The eHects of sodium bicarbonate 4.4 Discussion 4.4.7 Gibberellic acid and cypsela getminafion 4.4.2 Potassium nitrate and cypsela germination 4.4.3 Sodium bicarbonate and cypsela germination 4.4.4 Ecological implications 4.4.5 Variation in response to chernicals among populations 4.5 References CHAPTER 5 INTERPOPULATION VARIANCE IN GERMINATION RESPONSES OF SCOTCH THISTLE, ONOPORDUM ACANTHlUM L., UNDER CONTRASTING LlGHT AND TEMPERATURE REGIMES 5.1 Introduction 5.2 Materials and methods 5.2.7 Cypsela aollection 5.2.2 Germhafion tests 5.2.3 Statistical analyses 5.3 Results 5.3.1 Temperature efects 5.3.2 Light-temperature interactions 5.3.3 Different populations 5.4 Discussion 5.4. f The impact of different temperature regimes 5.4.2 The role of light 5.4.3 Four populations from one local area 5.5 References CHAPTER 6 GENERAL DISCUSSION 6.1 The higher the maturation temperature the wider the germination window 6.2 Changes in germination window by chernicals 6.3 A wider germination window at higher germination temperatures 6.4 Concluding remarks 6.5 References APPENDICES VlTA LIST OF TABLES Page Table 3.1 Total germination percentages of freshly-harvested cypselas of Onopordum acanthium, from three populations (ESW, FCA, GP) grown under greenhouse and field conditions in London, Ontario. Cypselas were collected from Aug. 05 to Oct. 04, 1996 and inwbated at 25OC for 14h light, and 10°C for 1Oh dark. 33 Table 3.2 Coefficient of germination rates of freshly-harvested cypselas of O. acanthium from three populations (ESW, FCA, GP) grown under greenhouse and field conditions and incubated at 25OC for 14h light, and lO0C for 10h dark. 35 Table 3.3 Total germination percentages of freshlyharvested cypselas of 0. acanthium, from three populations (ESW, QI Ola) grown under greenhouse and field conditions in London, Ontario. Cypselas from al1 three populations were collected from July 06 to July 23, 1997 in the greenhouse and from Aug. 09 to Sept. 21, 1997 in the field and incubated at 25OC for 14h light, and 1O°C for 1Oh dark. 37 Table 3.4 Coefficient of germination rates of freshly-harvested cypselas of O. acanthium from three populations (ESW, Q, Ola) grown under greenhouse and field conditions and incubated at 25OC for 14h light, and 1O°C for 10h dark. 38 Table 4.1 The pH of solutions used as germination media for cypselas of O. acanthium collected in London, Ontario in 1996197. 53 Table 4.2 Total germination percentages of cypselas of 0.acanthium, collected from four populations (ESW, Q, Ola, GP) in London, Ontario in Sept. 1996 and Sept. 1997. Cypselas were subjected to various concentrations of gibberellic acid (Gk)and incubated at 25OC for 14h light, and 10°C for 10h dark from Dec. 22, 1996 to Feb. 05, 1997 (stored) and from Sept. 1 1 to Oct. 15, 1997 (fresh). 60 Table 4.3 Coefficient of germination rates of cypselas of O.