Global ETD Search

1	An examination of the relationship between NO, ABA and auxin in lateral root initiation and root elongation in tomato Sivananthan, Malini January 2006 (has links) The length of the primary root and the density of lateral roots determine the architecture of the root. In this thesis the effect of NAA, ABA and the NO donor SNP alone as well as the combination of ABA or NAA with SNP on lateral root development was investigated. The interaction between CPTIO, a NO scavenger, and NAA or SNP is also reported. Following preliminary experiments in which it was observed that the aerial part of the seedling influenced LR growth and that there was a possible inhibitory effect of light on cultured root tips, experiments were conducted with excised roots tips in the dark. NAA was shown to have the potential to initiate LRs across a wide concentration gradient with the total number of LRs and initiated lateral root primordia (LRP) remaining constant across the range of concentrations tested. Over the last decade, nitric oxide (NO), a bioactive molecule, has been reported to be involved in the regulation of many biological pathways. The presence of NO in the system provided via sodium nitroprusside (SNP), promoted LRP initiation based on the NAA concentration gradient; but without changing the total LR initiation, that is LRs plus primordia density remained constant along the concentration gradient of NAA. The absence of LR and LRP in the treatments of CPTIO (a NO scavenger) with SNP or NAA suggests that NO regulates LRP initiation triggered by NAA, which is in agreement with the recent paper published after the commencement of this study (Correa-Aragunde et al., 2006). In agreement with previous studies, ABA inhibited lateral root development by reducing LR density and the number of LRs. The experiments with fluridone, an ABA biosynthesis inhibitor, may indicate that endogenous ABA was at sufficient concentrations in the excised root tips to inhibit primordia initiation. In this study, evidence is presented for the first time to show that SNP can relieve the inhibitory effect of ABA on LR density and number of LRs suggesting the NO, released from SNP, acts downstream of ABA. Overall these data confirm a critical role for NO in LR initiation. NO ABA auxin lateral root initiation root elongation
2	An examination of the relationship between NO, ABA and auxin in lateral root initiation and root elongation in tomato Sivananthan, Malini January 2006 (has links) The length of the primary root and the density of lateral roots determine the architecture of the root. In this thesis the effect of NAA, ABA and the NO donor SNP alone as well as the combination of ABA or NAA with SNP on lateral root development was investigated. The interaction between CPTIO, a NO scavenger, and NAA or SNP is also reported. Following preliminary experiments in which it was observed that the aerial part of the seedling influenced LR growth and that there was a possible inhibitory effect of light on cultured root tips, experiments were conducted with excised roots tips in the dark. NAA was shown to have the potential to initiate LRs across a wide concentration gradient with the total number of LRs and initiated lateral root primordia (LRP) remaining constant across the range of concentrations tested. Over the last decade, nitric oxide (NO), a bioactive molecule, has been reported to be involved in the regulation of many biological pathways. The presence of NO in the system provided via sodium nitroprusside (SNP), promoted LRP initiation based on the NAA concentration gradient; but without changing the total LR initiation, that is LRs plus primordia density remained constant along the concentration gradient of NAA. The absence of LR and LRP in the treatments of CPTIO (a NO scavenger) with SNP or NAA suggests that NO regulates LRP initiation triggered by NAA, which is in agreement with the recent paper published after the commencement of this study (Correa-Aragunde et al., 2006). In agreement with previous studies, ABA inhibited lateral root development by reducing LR density and the number of LRs. The experiments with fluridone, an ABA biosynthesis inhibitor, may indicate that endogenous ABA was at sufficient concentrations in the excised root tips to inhibit primordia initiation. In this study, evidence is presented for the first time to show that SNP can relieve the inhibitory effect of ABA on LR density and number of LRs suggesting the NO, released from SNP, acts downstream of ABA. Overall these data confirm a critical role for NO in LR initiation. NO ABA auxin lateral root initiation root elongation
3	Temperature Effect on Maize Germination And Root Elongation Ali, Omar Nazhan 10 August 2018 (has links) Early planting is one technique to avoid or reduce heat and drought problems that negatively affecting grain crop production. If producers adopt early planting, cold temperatures may negatively affect corn yield. It is important to select hybrids that are suited for planting earlier in the southern United States. Experiments were conducted by imposing low temperatures during seed germination. Twenty commercially available corn hybrids were evaluated for seed germination and root elongation. The first objective was: 1) To determine if some hybrids germinate better at cooler temperatures than others; and 2) Determine variation in root elongation at cold temperatures among commercially available hybrids. Corn hybrids varied significantly for seed germination and root traits under cold temperatures. Some hybrids have significantly surpassed others in seed germination traits, and they germinated earlier as well having longer radicle length. Also, there were significant differences across temperatures for all traits measured. A second objective was: 1) To quantify the effects of cold temperature on seed germination rate; 2) To evaluate the effects of different cold temperatures on seed germination behavior of corn hybrids under laboratory conditions to determine how fast they germinated; and 3) To classify hybrids for response to cold temperature using cumulative seed germination. The results showed that standard germination performance occurred at 10ºC for all hybrids, but these hybrids performed well under other cold treatments (7.2°C and 8.6° C). There were no big differences between early hybrids 93 to 105 RM (Relative Maturity) and full season 115 to 120 RM in germination % and rate in both experiments, so that means that it pretty much depends on the hybrid. Therefore, the temperature had a major influence on seed germination parameters. These findings are useful for hybrid selection with respect to cool soil temperature conditions during early planting. Root development Root elongation Cold temperature treatment Seed germination Hybrids Corn Drought avoidance Heat avoidance Maximum germination Germination rate Velocity index.
4	The Expanding Diversity of Plant U-box E3 Ubiquitin Ligases in Arabidopsis: Identifying AtPUB18 and AtPUB19 Function during Abiotic Stress Responses Yee, Donna 17 February 2011 (has links) The ability of plants to sense and respond to environmental and endogenous signals is essential to their growth and development. As part of these diverse cellular functions, ubiquitin-mediated proteolysis has emerged to be an important process involved in how plant signalling pathways can be regulated in response to such cues. Of the three enzymes involved in linking ubiquitin to protein targets, E3 ubiquitin ligases are of interest as they confer substrate specificity during this ubiquitination process. The overall focal point of this research is on plant U-box (PUB) E3 ubiquitin ligases, a family that has undergone a large gene expansion possibly attributable to the regulation of biological processes unique to the plant life cycle. In Arabidopsis there are 64 predicted PUBs, many for which biological roles have yet to be determined. And as research continues to uncover PUB functions, the functional diversity in the gene family will likely expand. Specifically the focus of this research is on characterizing two ARM repeat-containing PUBs – AtPUB18 and AtPUB19. General analysis of pub18 and pub19 T-DNA insertion lines for growth defects did not yield distinct altered phenotypes. Closer inspection of selected lines showed independent gene assortment phenotypes that, with further inordinately convoluted pursuit, proved to have an AtPUB18/19-unrelated outcome. The availability of Arabidopsis microarray databases provided exploratory expression profiling as a starting point to elucidate PUB function. AtPUB19 and closely related AtPUB18 are notable for their increased expression during abiotic stresses. While condition-directed germination assays showed a decreased sensitivity to salt and ABA for pub18 pub19 double insertion lines, no related change in susceptibility to these or other abiotic stress treatments were seen with condition-directed root growth assays. Thus, this preliminary work has begun to reveal insight into the complex abiotic stress-related roles AtPUB18 and AtPUB19 have during mediation of environmental stress acclimation in Arabidopsis. ubiquitination E3 ubiquitin ligase Arabidopsis U-box plant U-box degradation abiotic stress ABA salinity germination root elongation non-Mendelian segregation T-DNA insertions 26S proteasome programmed cell death leaf senescence bioinformatics microarrays Bio-Array Resource ovule abortion pollen collapse DEX rescue chlorophyll retention double mutant generation higher order knock-outs partial redundancy 0309 0715 0307
5	The Expanding Diversity of Plant U-box E3 Ubiquitin Ligases in Arabidopsis: Identifying AtPUB18 and AtPUB19 Function during Abiotic Stress Responses Yee, Donna 17 February 2011 (has links) The ability of plants to sense and respond to environmental and endogenous signals is essential to their growth and development. As part of these diverse cellular functions, ubiquitin-mediated proteolysis has emerged to be an important process involved in how plant signalling pathways can be regulated in response to such cues. Of the three enzymes involved in linking ubiquitin to protein targets, E3 ubiquitin ligases are of interest as they confer substrate specificity during this ubiquitination process. The overall focal point of this research is on plant U-box (PUB) E3 ubiquitin ligases, a family that has undergone a large gene expansion possibly attributable to the regulation of biological processes unique to the plant life cycle. In Arabidopsis there are 64 predicted PUBs, many for which biological roles have yet to be determined. And as research continues to uncover PUB functions, the functional diversity in the gene family will likely expand. Specifically the focus of this research is on characterizing two ARM repeat-containing PUBs – AtPUB18 and AtPUB19. General analysis of pub18 and pub19 T-DNA insertion lines for growth defects did not yield distinct altered phenotypes. Closer inspection of selected lines showed independent gene assortment phenotypes that, with further inordinately convoluted pursuit, proved to have an AtPUB18/19-unrelated outcome. The availability of Arabidopsis microarray databases provided exploratory expression profiling as a starting point to elucidate PUB function. AtPUB19 and closely related AtPUB18 are notable for their increased expression during abiotic stresses. While condition-directed germination assays showed a decreased sensitivity to salt and ABA for pub18 pub19 double insertion lines, no related change in susceptibility to these or other abiotic stress treatments were seen with condition-directed root growth assays. Thus, this preliminary work has begun to reveal insight into the complex abiotic stress-related roles AtPUB18 and AtPUB19 have during mediation of environmental stress acclimation in Arabidopsis. ubiquitination E3 ubiquitin ligase Arabidopsis U-box plant U-box degradation abiotic stress ABA salinity germination root elongation non-Mendelian segregation T-DNA insertions 26S proteasome programmed cell death leaf senescence bioinformatics microarrays Bio-Array Resource ovule abortion pollen collapse DEX rescue chlorophyll retention double mutant generation higher order knock-outs partial redundancy 0309 0715 0307

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