Techn. Universiẗat, Diss., 2005--München.

Thesis (Ph. D.)--Universität Göttingen, 2008. / Title from PDF t.p. (viewed July 29, 2010). Includes bibliographical references.

Cedrela fissilis é uma espécie arbórea decídua com uma ampla distribuição de ocorrência na América Latina. Ocorre desde a Argentina até o Panamá, na América Central. É uma espécie que pode habitar áreas baixas de florestas, ao nível do mar e pode ocorrer em altitudes de até 1000 metros. Conhecida popularmente como cedro, cedro branco, cedro rosado, cedro missioneiro, cedro vermelho. Ela pertence a um dos gêneros de espécies mais importantes de todo o mundo para a produção de madeira, sendo por isso muito explorada. Estudos dendrocronológicos podem ajudar a entender quais fatores ambientais influenciam as taxas de crescimento da formação de lenho nas plantas. Bem como podem dar informações sobre a dinâmica de populações, o desenvolvimento e a produtividade dos ecossistemas. Devido à grande amplitude de ocorrência e a formação anual nas zonas de incremento no xilema secundário, C. fissilis é uma das espécies mais promissoras para estudos dessa natureza em regiões tropicais e subtropicais na América do Sul. / Cedrela fissilis a deciduous tree, is a species with a widespread distribution in Latin America. Occurring from Argentina to Panamá and Costa Rica in Central America. It can live in lowland forests from sea level up to 1000 m. Is popularly named as cedro, cedro branco, cedro rosado, cedro missioneiro, cedro vermelho. It belongs to a world’s economically most important timber genus from the point of view of the excellence of its wood properties, which is the reason this species has been much exploited. Dendrochronological studies would help to understand the influence of environmental factors on its growth rate and wood formation, as well as to provide valuable information on the population dynamics and on the development and productivity of ecosystems. Due to its widespread distribution and the annual formation of increment zones in the secondary xylem Cedrela fissilis is one of the most promising tree species for dendroclimatological studies in tropical and subtropical South America.

Les modèles climatiques prédisent pour le futur une accentuation de la fréquence et de l’intensité des épisodes de sécheresse, ce qui affecterait sérieusement les écosystèmes forestiers. En conséquence, il y a une demande croissante pour du matériel végétal plus résistant à la sécheresse, et pour la compréhension des mécanismes génétiques et physiologiques de la tolérance des arbres à la sécheresse. Dans des conditions de sécheresse, la tension dans les vaisseaux du xylème augmente, et la cavitation peut se produire causant une embolie du vaisseau qui devient alors non fonctionnel. La vulnérabilité du xylème à la cavitation est corrélée à la tolérance à la sécheresse, indiquant l’importance de ce caractère pour la tolérance à la sécheresse. Cependant, peu était connu sur la variabilité de ce caractère au niveau intra-spécifique et ses bases génétiques étaient inconnues. Dans un premier temps, nous avons démontré que la vulnérabilité à la cavitation du xylème de peuplier (Populus tremula x Populus alba) s’acclimate à des conditions de sol plus sec et que ceci s’accompagne de changements dans la structure du xylème et d’expressions géniques. Ce processus d’acclimatation appuie l’hypothèse du rôle important joué par la vulnérabilité du xylème à la cavitation dans la tolérance à la sécheresse. Dans un second temps, nous avons étudié les bases structurales et génétiques de la vulnérabilité à la cavitation grâce à deux approches. La première a consisté à étudier les changements anatomiques et d’expressions géniques se produisant au cours de l’acclimatation de la vulnérabilité du xylème à la cavitation à des conditions plus sèches. Nous avons déterminé que l’augmentation de la vulnérabilité à la cavitation dans des conditions plus sèches est corrélée à une diminution du diamètre de la paroi de la ponctuation. Nous avons observé des changements d’expression géniques dans des conditions de sécheresse mais ceux ci n’ont pas pu être reliés à un changement de la vulnérabilité à la cavitation. Dans une seconde approche, nous avons utilisé dix lignées de peupliers dont l’expression de gènes impliqués dans le métabolisme de la lignine ont été modifiés et deux lignées surexprimant une pectine méthylestérase (PME) pour examiner le rôle de ces gènes dans la vulnérabilité à la cavitation. Chez les peupliers ayant un métabolisme des lignines modifié, nous avons également testé la relation entre les propriétés hydriques et mécaniques. Nous apportons des preuves que les lignines et les pectines (à travers les PME) sont impliquées dans la vulnérabilité à la cavitation et nos données sur les lignées transgéniques de peupliers ne soutiennent pas un lien exclusif entre les propriétés hydriques et mécaniques. / Climatic models predict greater frequency and intensity of drought episodes in the future that would seriously affected forest ecosystems. As a consequence, there has been a rising demand for more drought-resistant plant materials and for the understanding of the physiological and genetic bases of tree drought tolerance. Under drought conditions, the tension in the xylem conduits increases and cavitation can occur that causes embolism and makes the vessel non functional. Xylem vulnerability to cavitation is correlated with drought tolerance, pointing that it’s an important trait for drought tolerance of trees. However, few was known about the variability of this trait at the within species level and its genetic bases were unknown. In a first part, we demonstrated that the xylem vulnerability to cavitation of poplar (Populus tremula × Populus alba) acclimated to drier soil conditions, and was accompanied with changes in xylem structure and gene expressions. This acclimation process supports the role of vulnerability to cavitation in drought tolerance. In a second part, we investigated the structural and genetic bases for vulnerability to cavitation through two approaches. In a first one, we investigated the anatomical changes and the gene expressions that occur during the acclimation of vulnerability to cavitation to drier conditions. We found that the increase in vulnerability to cavitation in drier soil conditions was related to a decrease in pit wall diameter. We observed changes in gene expressions in drier conditions but these changes could not be related to change in vulnerability to cavitation. In a second approach, we used ten transgenic poplar lines modified for expression of genes involved in lignin metabolism and two transgenic lines overexpressing a pectin methylesterase (PME) to examine the role of the respective genes in the vulnerability to cavitation. In poplars modified in lignin metabolism, we also tested the relation between hydraulic and mechanical properties. We present evidence that lignins and pectins (through PME) are involved in the vulnerability to cavitation and our data on the transgenic poplar lines do not support the exclusive link between mechanical vs. hydraulic properties.

Cedrela fissilis é uma espécie arbórea decídua com uma ampla distribuição de ocorrência na América Latina. Ocorre desde a Argentina até o Panamá, na América Central. É uma espécie que pode habitar áreas baixas de florestas, ao nível do mar e pode ocorrer em altitudes de até 1000 metros. Conhecida popularmente como cedro, cedro branco, cedro rosado, cedro missioneiro, cedro vermelho. Ela pertence a um dos gêneros de espécies mais importantes de todo o mundo para a produção de madeira, sendo por isso muito explorada. Estudos dendrocronológicos podem ajudar a entender quais fatores ambientais influenciam as taxas de crescimento da formação de lenho nas plantas. Bem como podem dar informações sobre a dinâmica de populações, o desenvolvimento e a produtividade dos ecossistemas. Devido à grande amplitude de ocorrência e a formação anual nas zonas de incremento no xilema secundário, C. fissilis é uma das espécies mais promissoras para estudos dessa natureza em regiões tropicais e subtropicais na América do Sul. / Cedrela fissilis a deciduous tree, is a species with a widespread distribution in Latin America. Occurring from Argentina to Panamá and Costa Rica in Central America. It can live in lowland forests from sea level up to 1000 m. Is popularly named as cedro, cedro branco, cedro rosado, cedro missioneiro, cedro vermelho. It belongs to a world’s economically most important timber genus from the point of view of the excellence of its wood properties, which is the reason this species has been much exploited. Dendrochronological studies would help to understand the influence of environmental factors on its growth rate and wood formation, as well as to provide valuable information on the population dynamics and on the development and productivity of ecosystems. Due to its widespread distribution and the annual formation of increment zones in the secondary xylem Cedrela fissilis is one of the most promising tree species for dendroclimatological studies in tropical and subtropical South America.

Cedrela fissilis é uma espécie arbórea decídua com uma ampla distribuição de ocorrência na América Latina. Ocorre desde a Argentina até o Panamá, na América Central. É uma espécie que pode habitar áreas baixas de florestas, ao nível do mar e pode ocorrer em altitudes de até 1000 metros. Conhecida popularmente como cedro, cedro branco, cedro rosado, cedro missioneiro, cedro vermelho. Ela pertence a um dos gêneros de espécies mais importantes de todo o mundo para a produção de madeira, sendo por isso muito explorada. Estudos dendrocronológicos podem ajudar a entender quais fatores ambientais influenciam as taxas de crescimento da formação de lenho nas plantas. Bem como podem dar informações sobre a dinâmica de populações, o desenvolvimento e a produtividade dos ecossistemas. Devido à grande amplitude de ocorrência e a formação anual nas zonas de incremento no xilema secundário, C. fissilis é uma das espécies mais promissoras para estudos dessa natureza em regiões tropicais e subtropicais na América do Sul. / Cedrela fissilis a deciduous tree, is a species with a widespread distribution in Latin America. Occurring from Argentina to Panamá and Costa Rica in Central America. It can live in lowland forests from sea level up to 1000 m. Is popularly named as cedro, cedro branco, cedro rosado, cedro missioneiro, cedro vermelho. It belongs to a world’s economically most important timber genus from the point of view of the excellence of its wood properties, which is the reason this species has been much exploited. Dendrochronological studies would help to understand the influence of environmental factors on its growth rate and wood formation, as well as to provide valuable information on the population dynamics and on the development and productivity of ecosystems. Due to its widespread distribution and the annual formation of increment zones in the secondary xylem Cedrela fissilis is one of the most promising tree species for dendroclimatological studies in tropical and subtropical South America.

No description available.

Equisetum giganteum L., a giant horsetail, is one of the largest living members of an ancient group of non-flowering plants with a history extending back 377 million years. Its hollow upright stems grow to over 5 m in height. Equisetum giganteum occupies a wide range of habitats in southern South America. Colonies of this horsetail occupy large areas of the Atacama river valleys, including those with sufficiently high groundwater salinity to significantly reduce floristic diversity. The purpose of this research was to study the ecophysiological and biomechanical properties that allow E. giganteum to successfully colonize a range of habitats, varying in salinity and exposure. Stem ecophysiological behavior was measured via steady state porometry (stomatal conductance), thermocouple psychrometry (water potential), chlorophyll fluorescence, and ion specific electrodes (xylem fluid solutes). Stem biomechanical properties were measured via a 3-point bending apparatus and cross sectional imaging. Equisetum giganteum stems exhibit mechanical characteristics of semi-self-supporting plants, requiring mutual support or support of other vegetation when they grow tall. The mean elastic moduli (4.3 Chile, 4.0 Argentina) of E. giganteum in South America is by far the largest measured in any living horsetail. Stomatal behavior of E. giganteum is consistent with that of typical C3 vascular plants, although absolute values of maximum late morning stomatal conductance are very low in comparison to typical plants from mesic habitats. The internode stomata exhibit strong light response. However, the environmental sensitivity of stomatal conductance appeared less in young developing stems, possibly due to higher cuticular conductance. Exclusion of sodium (Na) and preferential accumulation of potassium (K) at the root level appears to be the key mechanism of salinity tolerance in E. giganteum. Overall stomatal conductance and chlorophyll fluorescence were little affected by salinity, ranging from very low levels up to half strength seawater. This suggests a high degree of salinity stress tolerance. The capacity of E. giganteum to adapt to a wide variety of environments in southern South America has allowed it to thrive despite tremendous environmental changes during their long tenure on Earth.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19036号 / 農博第2114号 / 新制||農||1031(附属図書館) / 学位論文||H27||N4918(農学部図書室) / 31987 / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 髙部 圭司, 教授 髙野 俊幸, 教授 矢﨑 一史 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

The process of xylem tracheary element differentiation involves the coordination of vascular cambium activity, cell fate determination, cell expansion/elongation, secondary wall synthesis, programmed cell death, and cellular autolysis. The end result of tracheary element differentiation is a cellular corpse lacking a protoplast and consisting of a thickened cell wall composed mostly of lignin and cellulose. Little is known about the genetic mechanisms regulating the process of tracheary element differentiation. XCP2 expression localizes to tracheary elements according to two independent methods of analysis: promoter reporter experiments and immunogold localization by electron microscopy. XCP2 may be involved in catalyzing the degeneration of the protoplast during the final autolytic stages of tracheary element differentiation. To this date XCP2 function has not been directly demonstrated. In principle, any tracheary element-specific markers can be linked to upstream regulatory genes with roles in tracheary element differentiation. To develop the XCP2 promoter as a tool for identification of transacting factors, a promoter deletion analysis was carried out. Utilizing information from 5â and 3â deletion constructs, a 70-bp region upstream of the XCP2 translational start site is both necessary and sufficient for TE-specific expression of the UidA reporter gene. Mutational analysis of the ACTTTA element at position -113-bp strongly suggests it is a cis element required for XCP2 expression. In silico analysis of an 18-bp promoter region located within 200-bp of the translation start site and including the ACTTTA element revealed high indentity shared between xylem-specific XCP2 homologs from Zinnia elegans, Populus trichocarpa, and XCP1 from Arabidopsis thaliana. / Master of Science