Thesis (Ph. D.)--University of Washington, 2008. / Vita. Includes bibliographical references (leaves 76-89).

Thesis (Ph. D.)--Washington State University, December 2006. / Includes bibliographical references.

Effects of mineral nutrition on drought and cavitation resistance of poplars were examined in two sets of greenhouse-grown trees. First, two drought-sensitive and two drought-resistant hybrid clones of black cottonwood (Populus trichocarpa Torr. & Gray) and eastern cottonwood (P. deltoides Bartr.) were grown at three concentrations of nitrogen (N) applied factorially with two concentrations of phosphorus (P) in a sub-irrigation sand-culture system. The trees were subjected to 0, 4, 6, and 8 days of gradual drought stress before measurements of cavitation, anatomical features affecting cavitation, and nutrient mobilization during drought. High foliar concentrations of N increased cavitation compared to barely adequate concentrations, whereas high concentrations o f P decreased cavitation as measured by both hydraulic flow apparatus and dye perfusion techniques. For one test, cavitation was 48% at high N and low P, but only 28% at high N and high P. Vessel pit membrane mean pore diameters were 0.132 μm at low P and 0.074 μm at high P: smaller pores would decrease air-seeding cavitation. No other significant effects of mineral nutrition on vessel dimensions were observed. Scanning election microscopy showed less damage to pit membranes, suggesting greater membrane strength in drought-resistant clones than in drought-sensitive clones. In the second experiment, three drought-resistant and three drought-sensitive poplar clones (including P. trichocarpa) were grown at two levels of N and three levels of potassium (K) and either well-watered, cyclically droughted, or droughted once. Cavitation, osmotic potential, gas exchange, and nutrient mobilization were measured at each stage of drought and re watering, and fall nutrient retranslocation was monitored. Cavitation was greater with adequate foliar N than at deficiency levels. Moderate supplies of K increased cavitation, but luxury levels sometimes reduced cavitation by decreasing foliar water loss and thus xylem tension. Preconditioning did not reduce vulnerability to cavitation, but there was some evidence of cavitation reversal in a drought resistant clone at high N supply. Vessel diameters were 36.6 μm at low N but 45.2 μm at high N, so within Populus, larger diameter vessels correlated with susceptibility to cavitation. High N supply increased water stress during the first drought, but also increased instantaneous water use efficiency (WUE) before drought occurred, and osmotic adjustment and hardening after drought. Increased K also increased WUE before drought and decreased water stress (decreasing transpiration and wilting) at luxury levels, but did not influence osmotic adjustment or hardening. Mobilization of nutrients differed with speed and intensity of drought. Gradual drought led to resorption of N and P. In the second experiment, drought was too rapid for retranslocation. Nutrients became more concentrated; some (e.g., N) facilitated hardening and osmotic adjustment, and some (e.g., K) moved out of the leaves on re watering. In fall, N, P, Cu and K were resorbed, the latter more proficiently with greater N supply at low levels of K. Clones which were more productive on dry sites resisted severe, but not moderate cavitation. Cavitation-resistant clones maintained high transpiration rates (and less negative water potentials) in drought, especially after hardening, had more, but smaller, stomata and decreased leaf loss in drought, but did not have increased WUE or osmotic adjustment. Nitrogen fertilization increased cavitation, greater P supply reduced this effect, and K fertilization may make vessels more vulnerable to cavitation but decrease the tension on the xylem that causes cavitation. Nitrogen fertilization levels should be tailored to site water supplies, and appropriate P, and possibly K additions may increase drought resistance. / Graduate

Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Cankering by Cytospora chrysosperma (Pers.) Fr. was investigated in a poplar nursery at Lulu Island, B. C. Cankers were observed to be more numerous in early winter than at other times and more numerous on Populus trichocarpa T & G than on the P.x canadensis hybrid cultivars P. ‘Robusta Bachieleri' and P. 'Regenerata'. The upper part of the shoot appeared to become cankered before the lower part. Experiments with cuttings of the three poplars showed that cankers developed from inoculations only when the bark moisture content was below a critical level. The hybrids were found to have a lower critical level than P. trichocarpa. Also, the incubation period was longer in the hybrids than in P. trichocarpa and longer in the lower part of the shoot than in the upper. Cankers were arrested when the cuttings were placed in water, the arresting time being shorter in the lower part of the shoot than in the upper part. Inoculated P. trichocarpa plants in the greenhouse became cankered when they were subjected to drought but the two hybrids required both drought and low relative humidity conditions for cankering to take place. The rate of moisture loss from cuttings exposed to a uniform relative humidity was found to be faster in P. trichocarpa than in the hybrids and faster from the upper part of the shoot than from the lower part. A basis for a superior water economy in the hybrids was suggested by their anatomical characteristics which included larger pith, wider vessels, greater sieve tube zone, more numerous bark fibres, thicker periderm and fewer lenticels than in P. trichocarpa. The lower shoot had a larger sieve tube zone, a thicker periderm and fewer lenticels than the upper part. In the nursery, the hybrids were found to have a significantly higher shoot moisture content during winter than P. trichocarpa and the lower part of the shoot had a higher moisture content than the upper part. The moisture content minima for all species occurred in late autumn. The results suggested that the greater resistance of the hybrids to Cytospora canker observed in the nursery was attributable to their greater water storage capacity and to the slower rate at which water was lost by evaporation during dormancy. The occurrence of the heaviest outbreaks of the disease in early winter could be attributed in part to the decrease in shoot moisture content in the late autumn. / Science, Faculty of / Botany, Department of / Graduate

During the 1950's and 1960's a railroad yard located in Oneida, Tennessee, was used as a creosote treatment facility for railroad ties. After the cross-ties were treated with creosote, the excess creosote was stored in an holding pond located about 100 feet north of Pine Creek (Fetterolf 1998). In 1990, during a creek modification project, creosote was discovered seeping through the banks of Pine Creek. The creosote had leached through the bottom of the pond and migrated towards the creek. In 1997, the Tennessee Department of Environment and Conservation authorized a remedial strategy prepared by Geraghty & Miller, Inc (Fetterolf 1998). The strategy involved the use of phytoremediation and a previously installed interception trench system. The primary goals of the phytoremediation plan are to stimulate biodegradation and to decrease groundwater flow, thus minimizing the migration of the contaminant into Pine Creek. Poplar trees were selected for the phytoremediation plan and were planted in two sections. The objectives of this report involved analyzing the hydrogeology of the Oneida, Tennessee site and organizing the collected data for the purpose of evaluating the impact of the phytoremediation and interception trench systems on the aquifer. The water level data was used to evaluate water level and hydraulic gradient changes due to evapotranspiration, rainfall, and groundwater extraction. It was obvious from the water level and rainfall comparison plots that the rainfall has a measurable effect on the water table elevation (i.e. groundwater flow). Some areas may be less affected because the coal layer has a tendency to decrease recharge. Meanwhile, the interception trench lowers the water level around the trench. The decrease in head occurs before and after the trench, thus the water level forms a "v-shape" at the trench. This "v-shape" lends to the notion that the hydraulic gradient also slopes towards the trench in both directions. As for the phytoremediation, there was not sufficient evidence to suggest that the water levels were being lowered by evapotranspiration. This was expected since the poplar trees were had only completed their second growing season. GMS MODFLOW was used to predict the effects on the water table due to the phytoremediation and the interception trench systems. The calibrated model did an adequate job in simulating the site when the interception trench was not in operation and the trees were not in their growing season. By using variable recharge in some areas, the results are expected to improve. For example, it is important to know the location of the coal layer so this area can be given a lower recharge value than the other areas in the model. As for the trench model, the simulated heads were much lower than the observed heads, which emphasizes that using wells is not the best method to simulate the interception trench. In the future, a transient model should be used to simulate the site with the trench operation, and the drain package could be used to model the trench itself. Meanwhile, the ET model was a valuable simulation, because it illustrates how effective the poplar trees can be even under conservative conditions. With an assumed root zone of just 3 feet and a maximum potential evapotranspiration rate of 4.6 gallons per day per tree, the majority of the site will experience the dry conditions expected. / Master of Science

Flavonoids are important and ubiquitous secondary metabolites and are known to participate in various developmental and stress response processes in plants. Common flavonoids include anthocyanins, proanthocyanidins and flavonols. This thesis aims to determine, at the molecular level, how the biosynthesis of flavonoids, in particular the proanthocyanidins, is regulated in poplar. Poplars accumulate large amount of flavonoids and the major flavonoid biosynthetic genes in poplar have been identified. Flavonoid biosynthesis is known to be regulated by MYB transcription factors. Previous work had identified MYB134 as a key regulator of proanthocyanidin synthesis in poplar. Here I describe experiments on five additional genes encoding MYB activators (MYB115 and MYB117), MYB repressors (MYB165 and MYB194), and one bHLH cofactor (bHLH131) as possible flavonoid regulators in poplar. The objective of this work is to determine the in planta functions of these new flavonoid regulators using reverse genetic methods, phytochemical and transcriptome analysis, to identify their target genes and to determine how these transcriptional regulators interact using promoter transactivation and yeast two- hybrid assays. MYB115 was identified as a second proanthocyanidin regulator. Similar to the effects of MYB134, overexpression of MYB115 in poplar led to increased proanthocyanidin content and upregulated flavonoid biosynthesis genes, but reduced the accumulation of salicinoids. Overexpression of repressor type MYBs, MYB165 or MYB194 led to reduced anthocyanin, salicinoid and hydroxycinnamic ester accumulation in leaves, while reducing proanthocyanidin content in roots. Transcriptome analysis demonstrated the downregulation of most flavonoid genes in these transgenics, as well as some shikimate pathway genes, confirming the broad repression function on the phenylpropanoid pathway. By contrast, MYB117 encodes an anthocyanin activator, and was shown to be specific to this branch of the flavonoid pathway. Overexpression of MYB117 in transgenic poplar increased accumulation of anthocyanin in all tissues, resulting in red poplar plants. One bHLH cofactor, bHLH131 was shown to interact with both MYB activators and repressors and required by MYB activators to activate flavonoid gene promoters. This indicate an important role of bHLH131 in the flavonoid biosynthesis. Proanthocyanidin MYB activators, MYB134 and MYB115 could activate each other. This indicates a positive feedback loop of proanthocyanidin MYB activators. Interestingly, repressor MYB165 suppressed expression of other flavonoid MYB repressors including MYB194 and MYB182, which shows a negative feedback loop of MYB repressors. The expression of bHLH131 was also regulated by MYB activators and repressors. These results reveal the complex interaction between these regulators. iii iv Unexpectedly, overexpression MYB134, MYB115 or MYB117 poplars upregulated flavonoid 3’5’-hydroxylase and cytochrome b5 genes, and lead to enhanced flavonoid B- ring hydroxylation and an increased proportion of delphinidin, myricetin Overexpression of flavonoid 3’5’-hydroxylase in poplar confirmed its function in enhancing B-ring hydroxylation. However, overexpression of cytochrome b5 in flavonoid 3’5’-hydroxylase- overexpressing plants did not further increase flavonoid B-ring hydroxylation. Thus its role in flavonoid B-ring hydroxylation remained unclear. These results show that flavonoid MYBs could also alter flavonoid structure. Together, these studies outline the complex regulatory network formed by flavonoid MYB activators and repressors, and bHLH cofactors controlling both flavonoid accumulation and structure. / Graduate / 2020-12-04

No description available.

The projected increased demands for forest products and the dwindling softwood supplies are expected to lead to increased pressure on the hardwood raw material base. The Eastern United States' hardwood region offers a great potential for supplying the nation's growing demand for wood based products. The problem in realizing this potential is that eastern hardwoods in general, and yellow-poplar (Liriodendron tulipifera L.) in particular, are underutilized. At present, dimension lumber used in light frame construction is almost exclusively manufactured from softwood species. Recent literature, research, and conferences have pointed to the possibility and feasibility of using yellow-poplar dimension lumber. It is an accepted species for light framing in the grading rules of the Northern Hardwood and Pine Manufacturers Association. Yet, if utilization of yellow-poplar as a dimension lumber species is to be realized, lumber yields and residue volumes for various grade and size classes of yellow-poplar trees must be available in order to allow land managers to assess the value of standing yellow-poplar timber, develop sound management objectives for the species, and encourage its wide use. Similar yield and residue information for yellow-poplar sawlogs is also needed to allow sawmill operators to evaluate the economic feasibility of producing dimension lumber from yellow-poplar logs. Yellow-poplar log grades were established to stratify yellow-poplar logs into salable dimension lumber classes when the lumber was manufactured by the Saw-Dry-Rip manufacturing system. These log grades are based on the southern pine log grades with log defect exclusion limits. Dimension lumber and residue yields for the yellow-poplar dimension lumber log grades are presented. The use of various grading schemes for stratifying yellow-poplar trees into salable dimension lumber classes was evaluated. It was found that estimates of salable dimension lumber yield from pooled data yielded better results than estimates using tree grades for stratification. Estimates for the dimension lumber yield are listed. Producing dimension lumber from yellow-poplar logs of various diameters and quality classes was evaluated in light of producing alternate products using net revenue graphs. The net revenue graphs suggested that a sawmill should utilize the lower diameter and lower quality logs for dimension lumber production. / Ph. D.

Thesis (M.A.)--University of Montana, 2007. / Title from title screen. Description based on contents viewed Sept. 25, 2007. Includes bibliographical references (p. 46).