POLLEN MORPHOLOGY OF THE LEONTODONTINAE (ASTERACEAE rLACTUCEAE) by KATHLEEN J. ZELEZNAK B.S., Kansas State University, 1975 A MASTER'S THESIS Submitted in partial fulfillment of the requirement for the degree MASTER OF SCIENCE Division of Biology KANSAS STATE UNIVERSITY Manhattan, Kansas 1978 Approved by: Ma j o r T" c o f e s sor '•^ TABLE OF CONTENTS *z,Hh Pa e c . 3l § Introduction 1 Literature Review 2 Materials and Methods 11 Results 20 Exomorphology 20 Endoroorphology 52 Discussion 70 References gft LIST OF FIGURES Figure Page 1 Lactuceae Pollen Diagram 7 2 Leontodontinae Endomorphology 9 3 Method of Measuring Pollen in LM 14 4- 5 SEM micrographs of pollen grains of Rhagadiolus stellatus 26 6 SEM micrograph of a pollen grain of Aposeris f oetida 26 7 SEM micrograph of a pollen grain of Hycs^ris radiata s. radiat a ~ 26 8- 9 SEM micrographs of pollen grains of Hedypnois cretica 26 10 SEM micrograph of a pollen grain of Aposeris foetida 26 11-12 SEM micrographs of pollen grains of Hyoseris radiata s. radia ta 26 13-17 SEM micrographs of pollen grains of Hedypnois c retica 28 18 SEM micrograph of a pollen grain of Hedypnois raonspeliensis 28 19-21 SEM micrographs of pollen grains of Garhadiolus hedypno is 28 22 SEM micrograph of a pollen grain of Hypochoeris radicata 37 23-24 SEM micrographs of pollen grains of Hypochoeris glabra 37 25 SEM micrograph of a pollen grain of Hypochoeris achyrophorous 37 26-27 SEM micrographs of pollen grains of Hypochoeris uniflora 37 28 SEM micrograph of a pollen grain of Hypochoeris cretensis 37 29-30 SEM micrographs of pollen grains of Hypochoeris grandiflora 37 31-32 SEM micrographs of pollen grains of Hypochoeris tenuif_olia 39 33-34 SEM micrographs of pollen grains of Hypochoeris hohenackeri 39 35 SEM micrograph of a pollen grain of Hypochoeris arenaria v. a nd in a 39 36-37 SEM micrographs of pollen grains of Hypochoeris tweediei 39 il . Figure Page 38-39 SEM micrographs of poller, grains of Hy pochoeris taraxacoides 39 40 SEM micrograph of a pollen grSin of Leontodon crispus s. asperrimus . 44 41-42 SEM micrographs of pollen grains of Leontodon laciniatus 44 43 SEM micrograph of a pollen grain of L eontodo n hirsutus 44 44 SEM micrograph of a pollen grain of Leontodon asper 44 45 SEM micrograph of a pollen grain of Leontodon crispus s, crispus 44 46 SEM micrograph of a pollen grain of Leontodon maroccanus 44 47-48 SEM micrographs of pollen grains of Leontodon saxatilis s. saxat ilis „ 44 49-51 SEM micrographs of pollen grains of Picris hieracio ides s . hieracioides , 49 52 SEM micrograph of a pollen grain of Picris hieracioides s . kamschatica 49 53-54 SEM micrographs of pollen grains of Picris hieracioides s. hieracioides .' 49 55-56 SEM micrographs of pollen grains of Picris echioides 49 57 SEM micrograph of a pollen grain of Picris damascena v. homocarpa # 49 58 SEM micrograph of a pollen grain of Picris hieracioides s. hieracioides . .58 59 TEM micrograph of the exine of Picris hieracioides s. hieracioides 58 60 TEM micrograph of the exine of Urospermum picroides 58 61 TEM micrograph of the exine of Hypochoeris acaulis . 58 62 SEM micrograph of a pollen grain of Hypochoeris taraxacoides 58 63 TEM micrograph of the exine of Leontodon laciniatus 58 64 TEM micrograph of the exine of Leontodon maroccanus 58 65 TEM micrograph of the exine of Hyoseris radiata s. radiata 60 66 TEM micrograph of the exine of Picris hieracioides s. hieracioides . .60 iii Figure Page 67 TEM micrograph of the exine of Aposeris f oetida 60 68-69 TEM micrographs of the exine of I'rypoch oeris arenaria v. anclina 60 70 TEM micrograph of the exine of Hypoc h oeri s apargioide s 60 IV LIST OF TABLES Table Page 1. Collection Data for Specimens Used In Pollen Study 16 2. Pollen Grain Measurements 62 3. Hypochoeris 73 4. Leontodon Chromosomal and Pollen Variability 76 5. Picris Pollen Data 79 v ACKNOWLEDGMENTS I wish to express my gratitude tqDr. Spencer Tomb for suggesting this study, and for his support, encouragement and contagious enthusiasm throughout. I am indebted to Dr. Ted Barkley for originally sparking my interest in botany for for his subsequent guidance and instruction in the finer points of plant taxonomy. To these men and to Dr. Peter Wong I extend ray sincere thanks for serving on ray graduate committee. I acknowledge John Krchma for his invaluable assistance in the SEM portion of this study, and Dr. Avelina Paulsen for her skill and patience in instructing me in the techniques of transmission electron microscopy. I also wish to thank fellow graduate students Dave Dille, Mark Wetter and Tom Lane for their companionship and for technical assistance in the various aspects of assembling this thesis. The use of the SEM and TEM facilities was supported by grants to Dr. Tomb from the Kansas State Agricultural Experiment Station. 1 also wish to acknowledge the curators and staffs of the following herbaria for allowing pollen for this study to be removed from their specimens: NY The New York Botanical Garden US U. S. National Herbarium, Smithsonian Institution GH Gray Herbarium, Harvard University F Field Museum of Natural History, Chicago vi INTRODUCTION The tribe Lactuceae (Cichoriedfc) of the Asteraceae (Compositae) includes approximately 72 genera anct*2300 species. The Lactuceae has 3 main centers of distribution: central Asia, the Mediterranean Basin, and western North America. The tribe was first: recognized as a natural group by de Jussieu (1789) and has since come to be considered the most dis- tinctive tribe of the Asteraceae, sharply defined by its ligulate heads, milky sap, and the widespread occurrence of highly sculptured, echinolo- phate pollen. This study examines the pollen characters of the subtribe Leontodontinae ( Garhadiolu s, Hedypnois , Hypochoer is , Leoniiodon , Picris , Rhagadiolus , Urospermum) of Stebbins (1953). Because Jeffrey (1966) linked Apos e ris and Hyoseris with the Leontodontinae on the basis of microcharacters , the pollen of these two genera also will be considered to ascertain if pollen data can be used to support Jeffrey's disposition of them. This thesis describes and documents endo- and exomorphological pollen data of the subtribe using light microscopy (LM) , scanning electron micro- scopy (SEM), and transmission electron microscopy (TEM) . These data are used to ascertain the relative degree of cohesiveness or naturalness of the subtribe and to improve the general understanding of cichoriacious pollen. The utility of pollen morphology in determining generic limits is also discussed. LITERATURE REVIEW Students of the Lactuceae have traditionally found the tribe to be taxonomically difficult because of die paucity of distinguishing exomorphic. floral characters. Early synantherologist3 found the nature of the pappus to be the single most useful diagnostic character and based their classi- fications largely on pappus and acheiie characters. This practice pro- duced highly artificial treatments of the Lactuceae (de Jussieu, 1789; Don, 1825; Cassini, 1826; Lessing, 1332; DeCandolle, 1838; Bentham, 1873a, 1873b; Hoffman, 1891). Modern systeraatists have been able to develop more natural classifications because 20th century tools and techniques have revealed new taxonomically useful characters. Stebbins (1953) emphasized pollen, stigmatic, and chromosomal characters in conjunction with phytogeography and growth habits to cluster the genera into 8 sub- tribes which are generally acknowledged as more natural than previous groupings. Jeffrey (1966) modified Stebbins' scheme using floral micro- characters (size and shape of collecting hairs on the style and style arms, and type of pubescence on the exterior of the corolla tube) to separate the tribe into 5 groups, 11 subgroups and 23 series. Formal taxonomic status was not given to these groups because Jeffrey recognized the need for further study, and was undecided as to what status (tribal or subfamilial) should be accorded the ligulate Asteraceae. Pollen characters were not easily incorporated into systematic investigations into the Lactuceae or other taxa until relatively recently but the study of pollen is by no means a modern science. Its development has indeed progressed markedly with 20th century advances in light and electron microscopy, but centuries before the first optics were ground, man was curiously aware of this yellow dust that forms inside flowers. The Latin word pollen (noun, neuter, 3rd declension) does in fact mean a fine flour or dust. Curiosity about pollen rleveloped into genuine interest when 17th century raicroscopists Nohemiah Grev and Marcello Malphigi first described variations between pollen grains cf different species, thereby laying the cornerstone for the field of systematic palynology. In 1694 Camerarius provided the impetus that boosted the casual interest in pollen to the level of fledgling science. He succeeded in unravelling the mystery of the fertilization mechanism in plants, thereby revealing at last the function of the curious yellow dust (Wodehouse, 1935). The development of systematic palynology as a science, like many other fields, is closely allied to advancements in light microscopy. As optics improved, finer pollen characters were discernible, and their taxo- nomic value became increasingly evident. In 1830 John Lindley demonstrated the utility of pollen morphology in systematics when he used pollen characters as the basis for the establishment of 4 tribes of orchidaceous plants. By the mid-1830' s both Julius Fritzsche and Hugo Von Mohl had constructed comprehensive classifications of pollen grain forms for large numbers of families (Wodehouse, 1935). And late in the 19th century Hugo Fischer conducted a critical examination of pollen from over 2000 species of 185 families. His studies contributed much to the body of knowledge about pollen grain formation and structure, and enabled him to demonstrate con- clusively the enormous phylogenetic value of pollen grain characters (Wodehouse, 1935).