Thesis (PH.D.)--University of Illinois, 1919. / Thesis note on verso of t.-p. Bibliography: p. 79-91. Also available in print.

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Foraging theory predicts active responses by organisms upon encounter with a resource, as opposed to the passive responses of differential survivorship and growth. Stems of the parasitic plant Cuscuta subinclusa invest in resource acquisition (coil) relative to host quality in a way predicted by the marginal value theorem (MVT) in that: (1) stem coiling, the necessary antecedent and determinant of resource uptake, precedes exploitation of host materials; and (2) mean coiling on a host species is proportional to: (a) mean growth/haustorium, (b) mean biomass accumulation over the season, and (c) mean parasite growth/host individual. Coiling is correlated with growth/host individual for the 5 native host species examined, but not when a non-native species is added to the model, suggesting coiling response is a result of natural selection. Preliminary evidence indicates that coiling in C. subinclusa is induced by host bark chemicals. Resource-poor stems of C. subinclusa are more likely to coil, and coil more, than resource-rich stems, thus nutritional state of the parasite as well as host value affects foraging responses. Evidence from other experiments suggests that the costs of growth, or "search costs", may affect host acceptability. When water is readily available, transplanted C. subinclusa stems are less likely to coil on branches of Platanus racemosa. During the dry season, when cellular expansion is difficult, all p. racemosa branches were coiled upon. Large parasites are more likely to over-winter and set seed a second season, and parasites that start from over-wintered tissue are significantly larger at flowering than are those that have started from seed. Seed set is correlated with parasite size, thus linking foraging response and fitness of the plant. C. subinclusa's foraging response does not, however, predict population level patterns of host use. The principal determinant of host use by C. subinclusa is average proximity of a species to Malosma laurina. Parasite individuals infest many host species each season, but initially establish, set most seed, and over-winter only on M. laurina. Individual response of C. subinclusa contributes to the model of host use only after proximity to M. laurina is accounted for, suggesting that mechanisms maximizing exploitation of a host take effect after contact between host and parasite.

odder is the common name for the group of plants in the genus Cuscuta· It is a serious weed in nearly all the legume seed producing areas of southern and western United States (5). Dodder is of major economic importance in the production of alfalfa, lespedeza, clover, and of less importance in such crops as flax, onions, sugar beets, and some ornamentals.

In recent years the weed commonly known as dodder has become an important reason for the rejection of several alfalfa seed fields for certification in Utah. The rapid spread of infestation in alfalfa seed fields, difficulty in removing the dodder seed from the alfalfa seed due to the similarity in size, and a lack of adequate control are among the main causes for the rising concern with dodder, Dodder is an annual which reproduces from seed each year.

Dodder (Cuscuta spp.) is a parasitic weed which attacks alfalfa, clovers, lespedeza and many other species of plants. This pest is especially troublesome when these crops are grown to produce seed.

Tsang, Kwok On. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 147-165). / Abstracts in English and Chinese. / ACKNOWLEDGMENTS --- p.i / ABSTRACT --- p.ii / TABLE OF CONTENTS --- p.vii / LIST OF FIGURES --- p.xiv / LIST OF TABLES --- p.XX / Chapter CHAPTER 1 --- Introduction --- p.1 / Chapter 1.1 --- "Mikania micrantha, a problematic weed around the world" --- p.1 / Chapter 1.1.1 --- Current situation --- p.1 / Chapter 1.1.2 --- Properties of M micrantha --- p.2 / Chapter 1.1.3 --- Control methods of M. micrantha --- p.6 / Chapter 1.1.3.1 --- Manual removal --- p.6 / Chapter 1.1.3.2 --- Chemical control methods --- p.7 / Chapter 1.1.3.3 --- Biological control methods --- p.7 / Chapter 1.2 --- Parasitic plants --- p.10 / Chapter 1.2.1 --- Introduction --- p.10 / Chapter 1.2.2 --- Modes of parasitism --- p.10 / Chapter 1.2.3 --- Biology of Cuscula spp. --- p.13 / Chapter 1.2.3.1 --- Seed germination --- p.15 / Chapter 1.2.3.2 --- I lost detection and parasitism --- p.17 / Chapter 1.2.3.3 --- Reproduction --- p.19 / Chapter 1.2.3.4 --- Impacts on hosts --- p.21 / Chapter 1.3 --- Previous researches on the control of M. micrantha by cuscuta --- p.23 / Chapter 1.4 --- Research significance --- p.25 / Chapter 1.4.1 --- Knowledge gap --- p.25 / Chapter 1.4.2 --- Experimental objectives and significance --- p.26 / Chapter 1.4.3 --- Thesis layout --- p.28 / Chapter CHAPTER 2 --- Germination biology of Cuscuta japonica --- p.29 / Chapter 2.1 --- Introduction --- p.29 / Chapter 2.2 --- Materials and Methods --- p.34 / Chapter 2.2.1 --- "Cuscuta seeds collection, treatment and storage" --- p.34 / Chapter 2.2.2 --- Imbibition --- p.35 / Chapter 2.2.3 --- Germination --- p.35 / Chapter 2.2.4 --- Emergence --- p.36 / Chapter 2.2.5 --- Germination dynamics --- p.37 / Chapter 2.2.6 --- Statistical analysis --- p.37 / Chapter 2.3 --- Results --- p.38 / Chapter 2.3.1 --- Imbibition test --- p.38 / Chapter 2.3.2 --- Germination test --- p.40 / Chapter 2.3.3 --- Emergence test --- p.42 / Chapter 2.3.4 --- Germination dynamic --- p.43 / Chapter 2.4 --- Discussion --- p.44 / Chapter 2.4.1 --- Seed dormancy --- p.44 / Chapter 2.4.2 --- Germination requirements --- p.48 / Chapter 2.4.3 --- Emergence ability --- p.51 / Chapter 2.4.4 --- Germination dynamics --- p.52 / Chapter 2.5 --- Conclusions --- p.54 / Chapter CHAPTER 3 --- Life cycle of C. japonica --- p.55 / Chapter 3.1 --- Introduction --- p.55 / Chapter 3.2 --- Materials and Methods --- p.57 / Chapter 3.2.1 --- Site description --- p.57 / Chapter 3.2.2 --- Data collection --- p.62 / Chapter 3.3 --- Results --- p.64 / Chapter 3.4 --- Discussion --- p.71 / Chapter 3.4.1 --- Life cycle of C. japonica in Dragon's Back and its implication --- p.71 / Chapter 3.4.2 --- Life cycle of (\ japonica in Shan Tong Road and Yau King Lane --- p.74 / Chapter 3.5 --- Conclusions --- p.80 / Chapter CHAPTER 4 --- Effect of infestation by C. japonica and C. campcstris on the growth of M. micrantha --- p.82 / Chapter 4.1 --- Introduction --- p.82 / Chapter 4.2 --- Materials and Methods --- p.84 / Chapter 4.2.1 --- Sites description --- p.84 / Chapter 4.2.2 --- Plant materials --- p.85 / Chapter 4.2.3 --- Infestation --- p.86 / Chapter 4.2.4 --- Harvest of plant materials --- p.87 / Chapter 4.2.5 --- Chlorophyll extraction and concentration determination --- p.87 / Chapter 4.2.6 --- Measurements --- p.88 / Chapter 4.2.7 --- Statistical analysis --- p.89 / Chapter 4.3 --- Results --- p.89 / Chapter 4.3.1 --- "Changes in length of stem, leaf size and number of leaves" --- p.89 / Chapter 4.3.2 --- Changes in biomass of hosts and parasites --- p.94 / Chapter 4.3.3 --- Changes in the chlorophyll concentration --- p.97 / Chapter 4.4 --- Discussion --- p.99 / Chapter 4.2.1 --- Cuscuta as a strong sink to the host --- p.99 / Chapter 4.2.2 --- Growth of cuscuta and comparison of its influence on M micrantha --- p.104 / Chapter 4.5 --- Conclusions --- p.106 / Chapter CHAPTER 5 --- Effect of C. japonica infestation on the activities of anti-oxidative enzymes of M. micrantha --- p.107 / Chapter 5.1 --- Introduction --- p.107 / Chapter 5.2 --- Materials and Methods --- p.110 / Chapter 5.2.1 --- Plant materials --- p.110 / Chapter 5.2.2 --- Infestation --- p.111 / Chapter 5.2.3 --- Harvest of plant materials --- p.111 / Chapter 5.2.4 --- Measurement of enzyme activity --- p.112 / Chapter 5.2.4.1 --- Reagent preparation --- p.112 / Chapter 5.2.4.2 --- Extraction method --- p.112 / Chapter 5.2.4.3 --- Enzyme activity determination --- p.113 / Chapter 5.3 --- Results --- p.115 / Chapter 5.3.1 --- SOD activity --- p.115 / Chapter 5.3.2 --- CAT activity --- p.116 / Chapter 5.3.3 --- POD activity --- p.117 / Chapter 5.4 --- Discussion --- p.1 19 / Chapter 5.4.1 --- Changes in SOD activity --- p.120 / Chapter 5.4.2 --- Changes in CAT and POD activity --- p.122 / Chapter 5.4.3 --- Effects and implications of the changes in the activities of the anti-oxidative enzymes --- p.123 / Chapter 5.5 --- Conclusions --- p.124 / Chapter CHAPTER 6 --- Host range of C. japonica --- p.126 / Chapter 6.1 --- Introduction --- p.126 / Chapter 6.2 --- Materials and methods --- p.130 / Chapter 6.2.1 --- Field study --- p.130 / Chapter 6.2.1.1 --- Site description --- p.130 / Chapter 6.2.2.2 --- Data collection --- p.130 / Chapter 6.2.2 --- Greenhouse study --- p.131 / Chapter 6.2.2.1 --- Site description --- p.131 / Chapter 6.2.2.2 --- Plants selection --- p.131 / Chapter 6.2.2.3 --- Experimental setup --- p.132 / Chapter 6.2.2.4 --- Statistical analysis --- p.133 / Chapter 6.3 --- Results --- p.133 / Chapter 6.3.1 --- Field study --- p.133 / Chapter 6.3.2 --- Greenhouse study --- p.137 / Chapter 6.4 --- Discussion --- p.138 / Chapter 6.4.1 --- Field study --- p.138 / Chapter 6.4.2 --- Greenhouse study --- p.140 / Chapter 6.4.3 --- Implications on application --- p.141 / Chapter 6.5 --- Conclusions --- p.143 / Chapter CHAPTER 7 --- General Summary and Conclusions --- p.144 / REFERENCES --- p.147 / APPENDIX A --- p.166 / APPENDIX B --- p.173 / APPENDIX C --- p.176

It is surprising to know the small amount of work that has been done on alternate freezing and thawing of seeds. Many experiments, however, have been conducted to see the effect of very low temperatures on seeds and to notice the effect it had on their vitality. Some experimenters subjected seeds to temperatures as low as liquid hydrogen with very interesting results but in very few cases, if any, was the effect of alternate freezing and thawing studied. The work that follows deals directly with the effects of alternate freezing and thawing on impermeable seeds of alfalfa and of dodder. It is known that this seed does not germinate readily; therefore it often lays over winter in the soil. Does this natural freezing and thawing aid or hinder this impermeable seed in it's later germination? this has been the main question kept in mind throughout this experiment.

Dodder (Cuscuta gronovii Willd.) is a weed of serious concern to cranberry (Vaccinium macrocarpon Ait.) growers. It develops vigorously and has a long-lived seed bank. Cranberries are a perennial crop and therefore strategies available to growers of annual crops are not practical. Herbicides, the primary management tool for dodder, although effective, have a narrow window of application and extended seedling emergence after applications can result in escapes. This project examined the effect of water temperature on dodder seed germination and the use of short-term floods (less than 72 hr) for dodder management. Experiments investigated the effect of water temperature on dodder seed germination. Studies, ran twice, submerged dodder seed in water for 0 to 48 hr at 10, 15, and 20 C in one experiment (simulating spring water temperatures) and 0 to 48 hr at 15, 20, and 25 C in a separate experiment (simulating summer water temperatures). In Run 1, the effect of temperature on percent seed germination varied by flood duration; and by temperature alone in Run 2. Percent seed germination however, always fell within normal ranges (35-59%), indicating that flooding may not impact seed germination. Two 1-yr field studies were conducted to evaluate the use of short-term floods (24 to 48 hr) for managing dodder in cranberries. Two scenarios were simulated: cranberry beds with no emergent weed populations (cranberries alone) and cranberries with emergent weed populations (cranberries with additional host). There were three flood durations (0, 24, and 48 hr) and four flood initiations (1 to 4 wk after first seedling emergence). In 2006, mean percent germination from seeds incubated in Petri dishes was lower for seeds submerged 3 and 4 wk after first emergence (AFE) for the 48-hr flood durations. In 2007, mean percent germination for seeds submerged for 24 and 48-hr decreased for floods initiated at 4 wk AFE. Flooding 4 wk AFE resulted in lowest mean attachment ratings in both years and lowest mean dodder biomass on cranberry in the 2007 cranberry and tomato study, suggesting later flood initiation may provide better dodder management.

Cuscuta pentagona is an obligate parasitic plant that hinders production of crops throughout the world. Parasitic plants have unique morphological and physiological features, the most prominent being the haustorium, a specialized organ that functions to connect them with their host's vascular system. The Cuscuta haustorium is remarkable in that it enables mRNA movement to occur between hosts and parasite, but little is known about the mechanisms regulating cross-species mRNA transfer or its biological significance to the parasite. These questions were addressed with genomics approaches that used high throughput sequencing to assess the presence of host mRNAs in the parasite as well as parasite mRNAs in the host. For the main experiment Cuscuta was grown on stems of Arabidopsis thaliana and tomato (Solanum lycopersicon) hosts because the completely sequenced genomes of these plants facilitates identification of host and parasite transcripts in mixed mRNA samples. Tissues sequenced included the Cuscuta stem alone, the region of Cuscuta-host attachment, and the host stem adjacent to the attachment site. The sequences generated from each tissue were mapped to host reference genes to distinguish host sequences, and the remaining sequences were used in a de novo assembly of a Cuscuta transcriptome. This analysis revealed that thousands of different Arabidopsis transcripts, representing nearly half of the expressed transcriptome of Arabidopsis, were represented in the attached Cuscuta. RNA movement was also found to be bidirectional, with a substantial proportion of expressed Cuscuta transcripts found in host tissue. The mechanism underlying the exchange remains unknown, as well as the function of mobile RNAs in either the parasite or host. An approach was developed to assay potential translation of host mRNAs by detecting them in the Cuscuta translatome as revealed by sequencing polysomal RNA and ribosome-protected RNA. This work highlights RNA trafficking as a potentially important new form of interaction between hosts and Cuscuta. / Ph. D.