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In 2011, Poa annua L. (Poa) biotypes were collected from greens of two golf courses in Lexington, Kentucky: 1.) The Lexington Country Club (LCC) and 2.) The University Club (UC). The samples were collected based on exhibiting one of two appearances while on the same green: 1.) dark green, with few to no flower heads (dark biotype) or 2.) light green, with numerous flower heads (light biotype). Two PGRs, paclobutrazol and flurprimidol, and two herbicides, bispyribac-sodium and amicarbazone, were applied to the plants both in the field and the greenhouse. Quality ratings were recorded weekly in both the field and greenhouse and grass clippings were collected and measured weekly in the greenhouse. Flurprimidol controlled the dark biotypes and paclobutrazol controlled the light biotypes in the field in 2011. However, only location by treatment interactions were in 2012; flurprimidol, bispyribac-sodium, and amicarbazone controlled the biotypes from the LCC while paclobutrazol controlled the biotypes from UC. In the greenhouse study there was a significant three way interaction between color, location, and treatment for quality. PGRs controlled the light biotypes from LCC and the dark biotypes from UC. Herbicides controlled the light biotypes more than the dark, however, the light biotypes recovered after amicarbazone treatments. PGRs reduced clipping weights of the dark biotypes more than the light and herbicides reduced clipping weights of the light biotypes more than the dark. Both PGRs and herbicides reduced clipping weights of the Poa collected from the LCC more than UC. These results demonstrate both the potential for differential responses between Poa biotypes to PGRs and herbicides and that these differences, like all things about Poa, may be complex. A laboratory experiment was also designed to examine the absorption and potential metabolism of 14C-labeled flurprimidol in creeping bentgrass (Agrostis stolonifera (L.)), bermudagrass (Cynodon dactylon (L.)), Kentucky bluegrass (Poa pratensis (L.)), perennial ryegrass (Lolium perenne (L.)), tall fescue (Festuca arundinacea (Schreb.)), and zoysiagrass (Zoysia japonica (Steud.)) and light and dark Poa biotypes collected from golf greens. Flurprimidol absorption and translocation was greater for warm season grasses than cool season grasses. Only parent flurprimidol was detected in all turf species.

The plant growth-promoting bacterium (PGPB) Pseudomonas putida UW4, previously isolated from the rhizosphere of common reeds growing on the campus of University of Waterloo, promotes plant growth in the presence of different environmental stresses, such as flooding, high concentration of salt, cold, heavy metals, drought and phytopathogens. The known mechanisms used by P. putida UW4 to promote plant growth include 1-aminocyclopropane-1-carboxylate (ACC) deaminase, indole-3-acetic acid (IAA) synthesis and siderophore production. In this work, the genome sequence of UW4 was obtained by pyrosequencing and the gaps between the contigs were closed by directed PCR. The P. putida UW4 genome contains a single circular chromosome that is 6,183,388 bp with a 60.05% G+C content. The bacterial genome contains 5,431 predicted protein-coding sequences that occupy 87.4% of the genome. Nineteen genomic islands were predicted and thirty one complete putative insertion sequences were identified. Genome analyses were conducted in order to better characterize the general features of the UW4 genome. Genes potentially involved in plant growth promotion such as IAA biosynthesis, trehalose production, siderophore production, and acetoin synthesis were identified, which will facilitate a better understanding of the mechanisms of plant-microbe interactions. Moreover, genes that contribute to the environmental fitness of UW4 were also determined including genes responsible for heavy metal resistance such as nickel, copper, cadmium, zinc, molybdate, cobalt, arsenate, and chromate. Central metabolic pathways helped elucidate the physiological roles of diverse metabolites of UW4. Unexpectedly, whole-genome comparison with other completely sequenced Pseudomonas sp. revealed that UW4 is more similar to the fluorescens group rather than to the putida group. More surprisingly, a putative type III secretion system (T3SS) was found in the UW4 genome, and T3SS was thought to be essential for bacterial pathogenesis. Although putative T3SS was observed in other non-pathogenic Pseudomonas spp. previously, this is the first report indicating that a T3SS in a Pseudomonas sp. is highly similar to the one from Salmonella spp.

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.

Auxins are plant hormones involved in virtually all aspects of plant life. Despite long-term commercial and horticultural use of the auxin Indole-3-Butyric Acid (IBA), a full recognition of its natural occurrence in plants was made only recently. I have used multiple approaches to dissect the role of IBA in Arabidopsis thaliana. This thesis includes the first characterization of a mutant with an altered response to IBA that retains wild-type sensitivity to Indole-3-Acetic Acid (IAA), the most studied endogenous auxin. This mutant, named resistant to IBA ( rib1), has modified root architecture and gravitropism and is resistant to auxin transport inhibitors. As these phenotypes are reminiscent of those of characterized auxin transport mutants, movement of IAA and IBA was studied in wild-type and mutant plants. IBA is transported in seedlings in three distinct flows, like IAA, and this transport is saturable, indicating it is carrier mediated. However, unlike IAA, IBA is not polarly transported in inflorescence axes, and IBA transport is not sensitive to IAA transport inhibitors. These results suggest IAA and IBA transport could be mediated or regulated by different mechanisms. In rib1 seedlings, all flows of IBA transport are modified, while IAA transport levels are unchanged. Modifications in IBA transport match phenotypic differences between rib1 and wild-type, and analyses of the physiological effects of IBA also suggest IBA has a role in defining wild-type seedling morphology in Arabidopsis. Though IAA transport levels are not changed in rib1, one flow of IAA transport is rendered insensitive to IAA transport inhibitors, perhaps revealing cross-talk between IAA and IBA transport regulation. Additionally, double mutant analyses reveal that IAA transport and response mutants can suppress some phenotypes of rib1, and some mutant combinations produce novel phenotypes, further suggesting cross-talk between IBA and IAA transport and response p

Salt affected soils and their effects on land and water resources have been identified as one of the most severe environmental problems facing Australia. This current study focused on the incorporation of recycled organic products (RO) into an acidic saline soil that had been irrigated with an industrial effluent (IE), specifically to investigate the potential for these organics to be used in rehabilitation. Compost incorporated into the acidic saline soil was able to raise pH to more favourable levels required for plant growth (pH 6 – 7.5). Plant growth was however dependent on the input material of the compost as well as the irrigation scheme. The soils amended with this compost generally showed higher and more rapid microbial activity, measured by CO2 emissions, in all amendment rates than the plant derived compost. Overall it could be concluded that the application of RO on saline soils improved the establishment and growth of plants and alleviated to some degree the negative effects of IE. However great care should be taken at the selection of the input material, as high rates of ammonium, calcium and other soluble salts can increase the EC of an amended soil further.

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No description available.

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