Bacteria that provide benefit to plants are considered to be plant growth-promoting bacteria (PGPB) and can facilitate plant growth by a number of different mechanisms. Plant growth-promoting bacteria that are able to utilize the plant compound 1-aminocyclopropane-1-carboxylate (ACC) as a sole source of nitrogen, as a consequence of possessing the enzyme ACC deaminase, can protect host plants from a number of environmental stresses. In addition to ACC deaminase, PGPB may utilize other mechanisms to facilitate plant growth including IAA synthesis, siderophore production, phosphate solubilization activity, ammonia production, and antibiotic production. Plant growth-promoting bacterial endophytes employ similar plant growth promotion mechanisms to those used by rhizospheric PGPB. In fact, bacterial endophytes are PGPB that go one step further and colonize the inside of the plant tissues and provide more efficient and prompted protection to their hosts compared to those that bind exclusively to the plant’s rhizosphere. Therefore, it is likely that endophytic plant growth-promoting bacteria will be superior to similar non-endophytic bacterial strains in promoting plant growth under a wide range of environmental conditions. In the work reported here, new bacterial endophytes were isolated and characterized. Among twenty-five ACC deaminase positive strains, two best strains were selected and ACC deaminase deficient mutants were constructed. The ability of two newly isolated 1-aminocyclopropane-1-carboxylate (ACC) deaminase-containing plant growth-promoting bacterial endophytes Pseudomonas fluorescens YsS6, Pseudomonas migulae 8R6 and their ACC deaminase deficient mutants was shown to 1) delay the senescence of mini carnation cut flowers and 2) to facilitate tomato plant growth under salinity stress. In the mini carnation flower senescence evaluation, the only difference between wild-type and mutant bacterial endophytes was ACC deaminase activity, our results demonstrate that this enzyme is directly responsible for a significant delay in flower senescence. Despite containing ACC deaminase activity, the rhizosphere-binding PGPB Pseudomonas putida UW4 was not taken up by the cut flowers and therefore had no effect on prolonging flower shelf life. In evaluating the effect of bacterial endophytes under salt stress, tomato plants treated with either of the wild-type strains of the two selected bacterial endophytes demonstrated early flowering and fruiting and had significantly greater numbers of flowers, buds, and fruits than either the corresponding ACC deaminase mutant strain-treated plants or the control plants. Although both bacterial endophytes P. fluorescens YsS6 and P. migulae 8R6 showed significant plant growth-promotion capabilities, P. migulae 8R6 demonstrated better plant growth facilitation under salt stress than did P. fluorescens YsS6. P. migulae 8R6 treated tomato plants demonstrated the least sodium uptake, the highest chlorophyll content, and highest fresh and dry biomass. The results of the work presented here suggest that ACC deaminase containing selected bacterial endophytes could be employed as environmentally friendly adjuncts to agricultural and horticultural practice.

A large portion of an airport property is occupied by runways and taxiways, which must be kept in excellent condition to ensure the safety of the airplanes, and the people on board. Any free objects on the airfield can cause damage to aircraft and are a possible danger to both the airplanes and the passengers. However, deterioration of the concrete airfield can be a major hazard and the presence of de-icing and anti-icing fluids may accelerate degradation. The focus of this project was the evaluation and assessment of aircraft de-icing and anti-icing fluids on the deterioration of airfield concrete. These fluids are used to remove and prevent snow and ice formation on aircraft by lowering the freezing temperature of water. The primary component in both fluids is ethylene glycol, while additives, which are proprietary and unknown, are mixed in to control various properties. Very little research has been done regarding the effect of the de-icer and anti-icers on the concrete deterioration. The aim of this study was to gain a better understanding of its influence on the deterioration of airfield concrete through a series of mechanical and electro-chemical tests, as well as microscopic and elemental analysis. Based on the comparative experiments and analyses performed using water, ethylene glycol, de-icer, and anti-icer, it appears that de-icing fluids do not prematurely cause concrete deterioration. In addition, experimental procedures in this study utilized the de-icing fluids as a concentrate, which are unrealistic conditions on an airfield, where dilution occurs from the addition of water and the presence of snow and ice. There was precipitate formation in all cases of cement paste exposure to de-icing fluid, however, which indicates that reactions are occurring and should be investigated further to determine the long term effects on concrete. With respect to the scope of this study, it was determined that the use of de-icers and anti-icers cause no significant detrimental effects on concrete mechanical properties and durability.

Progress in DNA sequencing of plant genomes has revealed that, in addition to microorganisms, a number of plants contain genes which share similarity to microbial 1-aminocyclopropane-1-carboxylate (ACC) deaminases. ACC deaminases break down ACC, the immediate precursor of ethylene in plants, into ammonia and α-ketobutyrate. We therefore sought to isolate putative ACC deaminase cDNAs from tomato plants with the objective of establishing whether the product of this gene is a functional ACC deaminase. It was demonstrated that the enzyme encoded by the putative ACC deaminase cDNA does not have the ability to break the cyclopropane ring of ACC, but rather that it utilizes D-cysteine as a substrate, and in fact encodes a D-cysteine desulfhydrase. Kinetic characterization of the enzyme has shown that it is similar to other previously characterized D-cysteine desulfhydrases. Using site-directed mutagenesis, it was shown that altering two amino acid residues within the predicted active site changed the enzyme from D-cysteine desulfhydrase to ACC deaminase. Concomitantly, it was shown that by altering two amino acids residues at the same position within the active site of ACC deaminase from Pseudomonas putida UW4 changed this enzyme into D-cysteine desulfhydrase.

Ethylene is a plant growth regulator and plays a key role in leaf senescence. Its signaling, however, remains mostly unclear in sweet potato. Ethephon, an ethylene releasing compound, induced sweet potato detached leaf senescence and associated gene expression, and the effects were repressed by mitogen-activated protein kinase (MAPK) kinase inhibitor PD98059. These data suggest that MAPK cascade is likely involved in ethylene signaling leading to leaf senescence and associated gene expression. With gene-specific primers and RT-PCR methods, a full-length cDNA, SPMAPK, was isolated from ethephon-treated sweet potato leaves. SPMAPK contained 1098 nucleotides (365 amino acids) in the open reading frame. Sweet potato SPMAPK also exhibited high amino acid sequence identities (ca. 79.8% to 83.4%) with plant MAPKs, and was most close to Arabidopsis MPK3 and MPK6 in phylogenetic tree analysis. RT-PCR analysis showed that SPMAPK gene expression was detected in roots, stems, and leaves. The mature and partial yellowing leaves expressed higher amount. SPMAPK gene expression was also inducible and significantly enhanced by ethephon. Results from studies with inhibitors or effectors showed that ethephon treatment resulted in acceleration of leaf senescence in detached sweet potato leaves, promotion of leaf chlorophyll content reduction and decrease of photochemical Fv/Fm, and induction of associated gene expression. These ethephon-mediated effects were all delayed or repressed by pretreatment with ethylene receptor inhibitor 1-methylcyclopropene (1-MCP), MAPK kinase inhibitor PD98059, NADPH oxidase inhibitor diphenyleneiodonium (DPI), antioxidant reduced glutathione, calcium ion chelator EGTA, and de novo protein synthesis inhibitor cycloheximide, respectively. Based on these results we conclude that an ethylene-inducible mitogen-activated protein kinase SPMAPK was isolated from sweet potato leaves, and expressed higher amount in mature and partial yellowing leaves. Ethephon-induced sweet potato SPMAPK expression was significantly repressed by 1-MCP, PD98059, DPI, reduced glutathione, EGTA and cycloheximide. These data also suggest that the possible signal components in ethephon-mediated leaf senescence and associated gene expression in sweet potato leaves likely include ethylene receptor, MAPK cascade, elevated H2O2 , external calcium influx, and de novo synthesized proteins. A possible ethylene signaling model leading to sweet potato leaf senescence and associated gene expression was also proposed.

Ethylene is a gaseous growth regulator, and plays an important role in response to plant developmental and environmental stimuli. Ethylene also plays a key role in leaf senescence. Calcium is a second message, and participates in the signal transduction pathways of many plant physiological responses. In this research, ethephon, an ethylene-releasing compound, was used to induce sweet potato leaf yellowing, chlorophyll content reduction, photochemical Fv/Fm decrease, H2O2 elevation and senescence-associated gene expression. These ethephon-mediated effects were all delayed or repressed by pretreatment of a calcium ion chelator, EGTA. Treatment with a calcium ionophore A23187 also induced senescence-associated gene expression in sweet potato detached leaves, and the induction was repressed by EGTA pretreatment. Calcium signaling in general is transmitted by calcium sensor proteins, including calmodulin to translate into appropriate responses to developmental and environmental stimuli. Therefore, pretreatment with calmodulin inhibitor chlorpromazine (CPZ) delayed or repressed ethephon-mediated leaf senescence, H2O2 elevation and senescence-associated gene expression. These CPZ-mediated effects were reversed by the exogenous application of an ethephon-inducible calmodulin SPCAM fusion protein. These results suggest that external Ca2+ influx and calmodulin SPCAM play a role in ethephon signaling leading to leaf senescence, H2O2 elevation and senescence-associated gene expression. In addition, NaCl salt stress also caused sweet potato leaf senescence, H2O2 elevation and senescence-associated gene expression. Pretreatment with CPZ delayed or repressed NaCl salt stress-mediated leaf senescence, H2O2 elevation and senescence-associated gene expression. These CPZ-mediated effects were also reversed by the exogenous application of calmodulin SPCAM fusion protein. These results suggest that calmodulin SPCAM may play a role in NaCl salt stress signaling leading to leaf senescence, H2O2 elevation and senescence-associated gene expression. Based on these results, external Ca2+ influx is required for ethephon induced leaf senescence. Ethephon-inducible calmodulin SPCAM likely participates in ethylene and NaCl salt stress signaling leading to leaf senescence, H2O2 elevation and senescence-associated gene expression in sweet potato in order to cope with different developmental cues or environmental stimuli.

Ethylene oxide (EO) is a very versatile compound with considerable energy in its ring structure. Its reactions proceed mainly via ring opening and are highly exothermic. Under some conditions, it is known to undergo a variety of reactions, such as isomerization, polymerization, hydrolysis, combustion and decomposition Due to its very reactive characteristic and widely industrial applications, EO has been involved in a number of serious incidents such as Doe Run 1962, Freeport 1974, Deer Park 1988 and Union Carbide Corporation’s Seadrift 1991. The impacts can be severe in terms of death and injury to people, damage to physical property and effects on the environment. For instance, the Union Carbide incident in 1991 caused one fatality and extensive damage to the plant with the property damage of up to 80 million dollars. Contamination has a considerable impact on EO reactivity by accelerating substantially its decomposition and playing a key role on EO incidents. In this work, the reactivity of EO with contaminants such as KOH, NaOH, NH4OH, and EDTA is evaluated. Useful information that is critical to the design and operation of safer chemical plant processes was generated such as safe storage temperatures (onset temperature), maximum temperature, maximum pressure, temperature vs. time, heat and pressure generation rates as a function of temperature and time to maximum rate using adiabatic calorimetry. A special arrangement for the filling-up of the cell was constructed due to the gaseous nature and toxicity of EO. A comparison of their thermal behavior is also presented since several contaminants are studied.

Poly(ethylene succinate) (PES), poly(trimethylene succinate) (PTS) and their copolyesters (PETSAs) with various compositions were used to investigate the structure-property relationship. The results of intrinsic viscosity and GPC have proven successful in preparing high molecular weight polyesters. The chemical compositions and the sequence distribution of co-monomers in the copolyesters were determined by NMR spectroscope. The distributions of ES unit and TS unit were found to be random. Their thermal properties were characterized using differential scanning calorimeter (DSC). The thermal stability of polyesters was analyzed by thermogravimeter (TGA) and polarized light microscope (PLM) under nitrogen. The results of TGA show that all of the samples have similar thermal stability (Tstart : 246¡Ó3 ¢XC), but the thermal degradation temperature of PES and PETSA(95/05) are 213 and 200 ¢XC, respectively, estimated from the isothermal growth rates after pre-melting at various temperatures. The degradation temperature analyzed by PLM is more sensitive than that obtained from TGA. The incorporation of 5 mol% of TS units into PES significantly reduces the thermal stability of PES. In addition, wide-angle X-ray diffractograms (WAXD) were obtained for polyesters which were crystallized isothermally at a temperature 5~10 ¢XC below their melting temperatures. The results of WAXD and DSC indicate that the incorporation of TS units into PES significantly inhibit the crystallization behavior of PES. In the second part of this study, PES and PETSA(95/05) were studied in detail. The crystallization kinetics and the melting behavior were investigated by using DSC in both conventional mode and modulated mode (TMDSC). The reversing, total, and non-reversing heat flow curves were analyzed. The Hoffman-Weeks plots gave an equilibrium melting temperature of 112.7 and 108.3 ¢XC for PES and PETSA(95/05), XI respectively. Only one crystal form was found from WAXD for specimens crystallized isothermally at various temperatures. Based on the WAXD patterns, DSC and TMDSC thermograms, multiple endothermic melting peaks can be explained by two mechanisms, melting-recrystallization-remelting and dual morphologies. PLM was used to study the growth rates and morphology of the spherulites. The growth rates measured in isothermal conditions were very well comparable with those measured by the non- isothermal procedure. In addition, the temperature range of growth rates detected by the non- isothermal procedure is wider than that by the isothermal method, which is time consuming. The regime II®III transition of PES was estimated at ~ 71 ¢XC which is very close to the literature values, and that of PETSA(95/05) was found at ~ 65 ¢XC.

The plant hormone ethylene plays an important role in plant growth, development, and physiology. One of the critical components of the ethylene signal transduction pathway, ctr1 (constitutive triple response), was identified using a particularly useful seedling screen that takes advantage of the profound effects ethylene has on etiolated seedlings, known as triple response. CTR1 is one of six Arabidopsis MAPKKKs that are related to the Raf kinases, and acts as a negative regulator of ethylene response. In this study, isolation and characterization of a family of CTR1-like genes in tomato is reported. Based on amino acid alignments and phylogenetic analysis, the tomato CTR1-like (LeCTR) genes are more similar to Arabidopsis CTR1 (AtCTR1) than any other MAPKKK sequences in the Arabidopsis genome. The capacity of the LeCTR genes to function as negative regulators in ethylene signal transduction was tested through complementation of the Arabidopsis ctr1-8 mutant. Quantitative real-time PCR was carried out to generate an expression profile for the CTR1-like gene family during different stages of development marked by increased ethylene biosynthesis, including fruit ripening. The possibility of a multi-gene family of CTR1-like genes in other species besides tomato was examined through mining of EST and genomic sequence databases. Based on nucleotide and amino acid identity, At4g24480 is most similar to AtCTR1 and could potentially represent a CTR1-like gene in Arabidopsis. Arabidopsis plants carrying a T-DNA insert in the At4g24480 locus were examined for abnormal ethylene response phenotypes including sensitivity to other hormones, signal molecules and abiotic stresses. Two mutant alleles, ctr1-1 and ctr1-8, containing mutations that disrupt kinase activity and receptor association, respectively, were examined for sensitivity to these same treatments in an effort to better characterize ethylene hormone and non-hormone interactions. They also served as controls to determine if At4g24480 indeed possessed CTR1-like function. Arabidopsis and tomato represent species with very distinct fruit ripening/maturation programs. The critical dependence on ethylene for fruit ripening in tomato might have resulted in alteration or modification of the ethylene signal transduction pathway relative to Arabidopsis. Plans to characterize individual functions of the LeCTR genes through over-expression and reduced expression in tomato are outlined.

Oligo(ethylene glycol) groups have been used as substituents in poly(p-phenyleneethynylene)s (PPEs) to provide solubility, and to boost quantum yield. Properties such as water-solubility and increased quantum yield in aqueous solution make these conjugated systems promising for biosensory applications. In this thesis, a PPE containing a branched ethylene glycol side chain is synthesized as part of a polymer array for glycan biosensing. I also report that the same side chain can be put to use in a red-emissive polymer to lend water solubility. Another monomeric unit, containing ethylene glycol chains, is incorporated into a PPE to create an ampiphilic polymer. The versatility of these polymers allows them to be used for a variety of purposes, some of which will be described herein.

The effect of antiplasticization on barrier properties of poly(ethylene terephthalate) (PET) has been investigated through transport measurements and some supplementary characterization techniques including dynamic mechanical measurements and solid state 13C cross polarization/magic angle spinning (CP/MAS) NMR. Our oxygen and carbon dioxide transport results were well described by a combination of the free volume based interpretation and interaction energy estimation. Transport characterization and DSC techniques verified that there exists a third element, a de-densified amorphous fraction in crystallized PET. Both oxygen and carbon dioxide permeabilities at 1 atm at 35ºC in PET with different crystallinities were well described by the Nielsen model due to the presence of an adjustable parameter, Ar, even though it is based on a two phase model. The comparison of the barrier improvement factor (BIF) values for samples annealed at 100ºC demonstrated that a combination of antiplasticization and crystallization allows for very efficient chain packing, which significantly improves the barrier properties of PET. A thorough molecular level study using dynamic mechanical analysis supported the synergistic effect of antiplasticization and crystallization on the molecular motion in PET. Lastly, a vapor/gas permeation system with a new concept of a flexible humidity and methanol vapor partial pressure clamp was designed and constructed. Even though its permeation results are not available at this point, its operational feasibility was well verified by pre-calculations and physical explanations. This system may be used for future studies to evaluate barrier properties of PET or modified PET samples.