Texte remanié de: Diss.--Heidelberg--Univ. Heidelberg, 2001.

Common gromwell (Lithospermum officinale) acts as a host plant for the monophagous moth Ethmia dodecea  whose larvae are completely dependent on the leaves. As conservation authorities now want to reinstate the regionally extinct moth to Mälardalen, a stable population of its host plant is a requirement. To facilitate the work of strengthening the presence of gromwell a partnership was therefore initiated between Västmanland County Board and Uppsala University. In this cooperation, I performed two studies. In the first one I examined how water and temperature affect plant germination and how nutrient levels affect early growth. In the second study I investigated whether the germination is influenced by chemical treatment (soaking in acid) and mechanical damage (seeds scratched with sandpaper) on the seeds. I worked with the hypothesis that gromwell is grazed by cows and is therefore dispersed and germinates in the spring. This should mean high water levels combined with high temperatures would produce higher germination. For the second study, it means that the germination rate should be higher in the seeds treated with the acid than in the scratched and control treatments. In the first study, so few seeds germinated that I could not draw any conclusions, but germinations appear to go faster in the combination with high nutrients high temperature and frequent watering. In the second study, the seeds scraped with sandpaper had the highest germination rate. This indicates that gromwell may be dispersed by birds, and I propose sandpaper rubbing as a method to easily increase the germination rates of L. officinale in greenhouses in order to reinforce small populations in the field.

京都大学 / 新制・課程博士 / 博士(農学) / 甲第24673号 / 農博第2556号 / 新制||農||1099(附属図書館) / 学位論文||R5||N5454(農学部図書室) / 京都大学大学院農学研究科応用生命科学専攻 / (主査)教授 矢﨑 一史, 教授 梅澤 俊明, 教授 伊福 健太郎 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

En el sudoeste de la provincia de Buenos Aires, la diversificación en los sistemas productivos sumado a un ambiente impredecible, hacen que el escenario ambiental de producción agrícola-ganadera difiera año a año. El éxito de las malezas depende, en gran medida, de su adaptación a dichos cambios. Las mismas constan de diferentes estrategias, como ser el efecto materno: cambios fenotípicos transgeneracionales consecuentes de las condiciones ambientales imperantes durante el ciclo de vida de la planta madre, especialmente en el desarrollo seminal. Las variaciones morfo-fisiológicas que se generan en la descendencia, se expresan principalmente en los estadios iniciales contribuyendo al establecimiento de la plántula. Comprender los efectos ambientales sobre la ecología de las malezas es de gran utilidad para diseñar estrategias de manejo y control más efectivas. Buglossoides arvensis es una maleza anual facultativa de invierno de creciente expansión en el sudoeste de la provincia de Buenos Aires, Argentina. Los objetivos generales del presente trabajo de tesis consistieron en: i) comprender las diferencias en el nivel de dormición de semillas de B. arvense provenientes de madres con ambientes contrastantes y dilucidar el control hormonal y ii) determinar cambios en las características morfo fisiológicas de las semillas y plántulas vinculadas a diferentes ambientes, a los fines de comprender mejor la estrategia de adaptación al medio. Con la finalidad de cumplir con dichos objetivos se realizaron experimentos que contaron con una fase inicial de generación de las plantas madres bajo condiciones contrastantes de niveles nitrogenados y/o hídricos en el suelo y un gradiente de intensidad lumínica. Los ensayos de la descendencia incluyeron i) evaluaciones en plancha de gradiente térmico con el fin de modelar la dormición y poder predecir su dinámica en función del ambiente experimentado por la planta madre, ii) ensayos en laboratorio con hormonas y sus inhibidores para entender variaciones en la dormición a nivel fisiológico y iii) cuantificación de la emergencia en cámaras de crecimiento y medición de atributos morfológicos de las plántulas resultantes a fin de correlacionarlos con ventajas adaptativas en los primeros estadios de vida. Una mayor fertilización nitrogenada, una menor disponibilidad hídrica y una baja intensidad lumínica generaron una descendencia con mayores porcentajes de emergencia e hipocótilos más largos. El menor nivel de dormición de las semillas provenientes de madres fertilizadas y de las sometidas a estrés hídrico se explica por una mayor temperatura media máxima permisiva de germinación. Las semillas provenientes de plantas fertilizadas mostraron similar sensibilidad al ácido abscísico y giberélico, principales hormonas reguladoras de la dormición, y similar comportamiento ante el agregado de los inhibidores de síntesis hormonal. Los resultados manifiestan la importancia de los efectos maternos en la adaptación al ambiente de B. arvensis. Una germinación temprana da ventajas competitivas en la toma de recursos ante los competidores. El conocimiento de los cambios en el nivel innato de dormición y en la emergencia de la maleza proporciona indicios para la predicción de la emergencia en cohortes permitiendo optimizar el momento de control. / In the southwest zone of Buenos Aires’ province, an unpredictable ambience plus the vast array of cultivation systems determines that the environmental situation for farming & livestock change year by year. The success of the weeds depends, to a great extent, on their adaptation to the mentioned changes. Weeds count with different strategies, such as the mother effect: transgenerational phenotypic changes consequent to the prevailing environmental conditions during the mother plant’s life cycle, particularly in the seminal development. The morpho-physiological variations generated in the offspring are expressed mainly in the initial stages contributing to the settlement of the seedling. Understanding the environmental effects on the ecology of the problematic weeds is of great help to design more effective management and control strategies. Buglossoides arvensis is an annual winter facultative weed species of growing expansion in the area of the study. The general objectives of this thesis consisted of: i) understanding of the differences in the dormancy level of B. arvensis due to the maternal environment and study of the hormonal control and ii) determination of the maternal influence on morpho-physiological characteristics of the offspring in seed and seedling state with the aim of better understanding the strategy of adaptation to the environment. In order to achieve such objectives experiments with an initial stage in which mother plants were obtained under contrasting conditions of nitrogen and water levels in the soil and with a light intensity gradient were performed. The offspring’s test included i) evaluations on thermic plate to model dormancy and to predict its dynamic according to the environment experienced by the mother plant, ii) laboratory experiments with hormone imbibition and inhibitors to understand dormancy variations at a physiological level and iii) emergence quantification in a growing chamber and measurement of the morphologic traits of the seedlings. More nitrogen fertilization, less hydric availability and a low light intensity increases emergence percentages and produced longer hypocotyls. The lower dormancy level of the seeds originated from fertilized and water stressed parent plants is explained by higher maximum of medium germination-permissive temperature. Seeds originated in fertilized plants showed similar sensitiveness to abscisic and gibberellic acids, which are the main hormones in regulating dormancy and similar behavior after the addition of the hormonal synthesis inhibitors. This results show the importance of maternal effects on the environmental adaptation of B. arvensis. Early germination provides superior competitive advantage in resources capture. Knowledge of innate dormancy levels, and hence plant emergence, contributes to prediction of the emergence cohorts, optimizing the moment for the weed control.

<div>Grand Sable Dunes, as a perched dune field on the shore of Lake Superior, is a sensitive</div><div>ecosystem subject to continual disturbance. Repeated natural disturbances necessitate specialized</div><div>plant communities to develop. There were two objectives of my research in this system that are</div><div>treated in separate chapters. They include: 1) the quantification of successional changes in the</div><div>plant community over time, and the identification of population demography changes for rare</div><div>species within the dunes and 2) the evaluation of evaluate in pollinator species for two plants</div><div>Hieracium caespitosum (Yellow Hawkweed) and Lithospermum caroliniense (Carolina</div><div>Puccoon).</div><div>For the first objective, target plant community composition and structures (i.e. richness,</div><div>diversity) were quantified in 2011 and 2018 across Grand Sable Dunes in 1 m² quadrats.</div><div>Additionally, two relatively rare plant species (Cirsium pitcheri and Tanacetum bipinnatum)</div><div>were selected to quantify demographic (i.e. flowering, non-flowering) patterns and changes over</div><div>time. Samples for C. pitcheri and T. bipinnatum were acquired via circle-plots 2.5 m in diameter.</div><div>Population comparisons between 2011 and 2018 illustrate minimal change in community</div><div>structure (richness and diversity). Composition increased slightly with eight species occurring in</div><div>2018, but not 2011. Additionally, community similarity was high (~78%) between the two years.</div><div>C. pitcheri occurrence was inversely related to presence of other species. Plant community</div><div>composition in eastern and western survey zones within the dunes appear to be diverging. Minor</div><div>changes in the plant community composition and structures indicate successional changes have</div><div>occurred, but without major disturbance. This divergence in community composition may be</div><div>related to weather related incidents associated with Lake Superior disturbance potential.</div><div>The secondary objective concerns pollinator species on two similar plant species found in</div><div>the Grand Sable Dunes. Individuals of H. caespitosum and L. caroliniense were observed and all</div><div>floral visitors were identified to family. The majority of arthropod families were observed</div><div>10</div><div>visiting both H. caespitosum and L. caroliniense, with an absence of typically important families</div><div>(e.g. Apidae, Bombiliidae). Halictidae, Muscidae and Syrphidae were the most common visitors,</div><div>with L. caroliniense attracting far more Muscidae than their H. caespitosum competitors.</div><div>Overlap in visitors for both species was observed, which may lead to decreased reproduction in</div><div>L. caroliniense.</div>