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Maize (Zea mays) root quiescent center (QC) cells deteriorate during hypoxic treatment, halting root growth. Over-expression of the Phytoglobin1 ZmPgb1.1 is known to alleviate these effects through the retention of the auxin flow along the root profile required for QC specification. To elucidate QC-specific hypoxia responses and whether ZmPgb1.1 exercises a direct role on QC stem cells, we performed a QC functionality test. This was done by estimating the ability of QCs to regenerate a root in-vitro in a hypoxic environment. Hypoxia decreased the functionality of the QCs by depressing the expression of several genes participating in the synthesis and response of auxin. This was accompanied by a decrease in DR5 signal in oxygen deprived QCs and a consequent suppression of QC markers and genes of jasmonic acid (JA) synthesis and signaling. Over-expression of ZmPgb1.1 mitigated all these responses. Through pharmacological alterations of auxin and JA (through 1-Naphthaleneacetic acid and methyl jasmonate, respectively), it is demonstrated that both compounds are required for QC functionality under hypoxia, and that JA acts downstream of auxin during QC regeneration. A model is proposed whereby the ZmPgb1.1 maintenance of auxin in hypoxic QCs is determinant for the retention of their functionality, with JA supporting the regeneration of roots from the QCs.

To examine the function of phytoglobin 2 (Pgb2) on seed oil level in the oil-producing crop Brassica napus L., we generated transgenic plants in which BnPgb2 was over-expressed in the seeds using the cruciferin1 promoter. Over-expression of BnPgb2 elevated the amount of oil, which showed a positive relationship with the level of BnPgb2, without altering the oil nutritional value, as evidenced by the lack of major changes in composition of fatty acids (FA), and key agronomic traits. Two key transcription factors, LEAFY COTYLEDON1 (LEC1) and WRINKLED1 (WRI1), known to promote the synthesis of fatty acids (FA) and potentiate oil accumulation, were induced in BnPgb2 over-expressing seeds. The concomitant induction of several enzymes of sucrose metabolism, SUCROSE SYNTHASE1 (SUS) 1 and 3, FRUCTOSE BISPHOSPHATE ALDOLASE (FPA), and PHOSPHOGLYCERATE KINASE (PGK), and starch synthesis, ADP-GLUCOSE PHOSPHORYLASE (AGPase) suggests that BnPgb2 favors sugar mobilization for FA production. The two plastid FA biosynthetic enzymes SUBUNIT A OF ACETYL-CoA CARBOXYLASE (ACCA2), and MALONYL-CoA:ACP TRANSACYLASE (MCAT) were also up-regulated by the over-expression of BnPgb2. The requirement of BnPgb2 for oil deposition was further evidenced in natural germplasm by the higher levels of BnPgb2 in seeds of high-oil genotypes relative to their low-oil counterparts.

Maize (Zea mays) root quiescent center (QC) cells deteriorate during hypoxic treatment, halting root growth. Over-expression of the Phytoglobin1 ZmPgb1.1 is known to alleviate these effects through the retention of the auxin flow along the root profile required for QC specification. To elucidate QC-specific hypoxia responses and whether ZmPgb1.1 exercises a direct role on QC stem cells, we performed a QC functionality test. This was done by estimating the ability of QCs to regenerate a root in-vitro in a hypoxic environment. Hypoxia decreased the functionality of the QCs by depressing the expression of several genes participating in the synthesis and response of auxin. This was accompanied by a decrease in DR5 signal in oxygen deprived QCs and a consequent suppression of QC markers and genes of jasmonic acid (JA) synthesis and signaling. Over-expression of ZmPgb1.1 mitigated all these responses. Through pharmacological alterations of auxin and JA (through 1-Naphthaleneacetic acid and methyl jasmonate, respectively), it is demonstrated that both compounds are required for QC functionality under hypoxia, and that JA acts downstream of auxin during QC regeneration. A model is proposed whereby the ZmPgb1.1 maintenance of auxin in hypoxic QCs is determinant for the retention of their functionality, with JA supporting the regeneration of roots from the QCs.

To examine the function of phytoglobin 2 (Pgb2) on seed oil level in the oil-producing crop Brassica napus L., we generated transgenic plants in which BnPgb2 was over-expressed in the seeds using the cruciferin1 promoter. Over-expression of BnPgb2 elevated the amount of oil, which showed a positive relationship with the level of BnPgb2, without altering the oil nutritional value, as evidenced by the lack of major changes in composition of fatty acids (FA), and key agronomic traits. Two key transcription factors, LEAFY COTYLEDON1 (LEC1) and WRINKLED1 (WRI1), known to promote the synthesis of fatty acids (FA) and potentiate oil accumulation, were induced in BnPgb2 over-expressing seeds. The concomitant induction of several enzymes of sucrose metabolism, SUCROSE SYNTHASE1 (SUS) 1 and 3, FRUCTOSE BISPHOSPHATE ALDOLASE (FPA), and PHOSPHOGLYCERATE KINASE (PGK), and starch synthesis, ADP-GLUCOSE PHOSPHORYLASE (AGPase) suggests that BnPgb2 favors sugar mobilization for FA production. The two plastid FA biosynthetic enzymes SUBUNIT A OF ACETYL-CoA CARBOXYLASE (ACCA2), and MALONYL-CoA:ACP TRANSACYLASE (MCAT) were also up-regulated by the over-expression of BnPgb2. The requirement of BnPgb2 for oil deposition was further evidenced in natural germplasm by the higher levels of BnPgb2 in seeds of high-oil genotypes relative to their low-oil counterparts.

UV-B and UV-C can damage DNA by generating DNA photoproducts such as cyclobutane pyrimidine dimers (CPDs), pyrimidine 6-4 pyrimidone (6-4 PPs) and its Dewar isomers (Dewar PP). These DNA photoproducts inhibit DNA transcription and replication, and cause mutations. Thus, DNA photoproducts must be repaired. Plants use two different mechanisms to repair these DNA photoproducts: light-dependent repair via photolyase and light-independent repair via nucleotide excision repair (NER). The NER mechanism in plants is similar to that elucidated in yeast and mammalian models. In yeast systems, the global genomic NER (GG-NER) damage recognition complex RAD7/RAD16/ELOC/ CUL3 recognizes the damaged DNA in the non-transcribed regions of the genome. The mammalian Elongin A/B/C/CUL5 /RBX2 and the yeast Elongin A/C/CUL3/RBX1 complexes target the large subunit of the lesion stalled RNAPII on the transcribed strand for ubiqitination and degradation. Arabidopsis has two RAD16 homologs: AtRAD16 and AtRAD16b. In this thesis, I characterized the role of AtRAD16 and AtRAD16b in plant UV tolerance and growth using loss of function and gain of function analysis. Atrad16 and Atrad16b null mutants exhibited increased UV sensitivity, early flowering time and short silique length. AtRAD16 overexpression increased UV resistance, and YFP-tagged RAD16 is localized in the nucleus. In addition, AtRAD16 physically interacts with AtRAD7, all these results indicate that the role of AtRAD16 in GG-NER is conserved with its yeast counterpart. I also identified Arabidopsis ELOA homolog, ELOA, and characterized the role of both Arabidopsis ELOA and ELOC homologs in plant UV tolerance and growth. Ateloa and Ateloc null mutants exhibited increased UV sensitivity in seedlings and adult plants. AtELOA was found to physically and genetically interact with AtELOC. AtELOA is nuclear localized, whereas AtELOC localized in the nuclei and the cytosol. ELOA overexpression increases hypocotyl UV resistance and ELOA/ELOC

Barley (Hordeum vulgare L.) is the most susceptible cereal species to excess moisture stress. Waterlogging-induced hypoxia causes major physiological changes that disrupt the photosynthetic machinery of seedlings. The signaling molecule nitric oxide (NO) regulates numerous metabolic processes but increases to toxic levels during hypoxia. Phytoglobin1 (Pgb1) functions as a NO-scavenging hemeprotein that influences hypoxic stress responses such as ethylene-mediated adaptations and nitrate use. This study demonstrated that overexpression of HvPgb1 maintains photosynthetic rate in barley during waterlogging, but also confirms previously reported decreases in physiological performance during normoxic (control) conditions. Foliar ethylene was found to decrease in waterlogged wild type (WT) but remain unchanged in the HvPgb1-overexpressing line [HvPgb1(OE)]. It is proposed that ACC from the hypoxic root mobilizes to the shoot, where it induces HvPgb1 activity and nitrate generation. Foliar nitrate was measured as well and showed a significant increase in leaves of waterlogged HvPgb1(OE) plants, while remaining unchanged in waterlogged WT leaves. These changes were associated to a putative increased in the levels of polyamines. Finally, HvPgb1 expression was measured from a group of selected waterlogging-tolerant and susceptible genotypes. A sharp increase in gene expression was seen in the leaves of waterlogged tolerant genotypes, thus positioning HvPgb1 expression as a potential molecular marker for waterlogging tolerance in barley.

Barley (Hordeum vulgare L.) is the most susceptible cereal species to excess moisture stress. Waterlogging-induced hypoxia causes major physiological changes that disrupt the photosynthetic machinery of seedlings. The signaling molecule nitric oxide (NO) regulates numerous metabolic processes but increases to toxic levels during hypoxia. Phytoglobin1 (Pgb1) functions as a NO-scavenging hemeprotein that influences hypoxic stress responses such as ethylene-mediated adaptations and nitrate use. This study demonstrated that overexpression of HvPgb1 maintains photosynthetic rate in barley during waterlogging, but also confirms previously reported decreases in physiological performance during normoxic (control) conditions. Foliar ethylene was found to decrease in waterlogged wild type (WT) but remain unchanged in the HvPgb1-overexpressing line [HvPgb1(OE)]. It is proposed that ACC from the hypoxic root mobilizes to the shoot, where it induces HvPgb1 activity and nitrate generation. Foliar nitrate was measured as well and showed a significant increase in leaves of waterlogged HvPgb1(OE) plants, while remaining unchanged in waterlogged WT leaves. These changes were associated to a putative increased in the levels of polyamines. Finally, HvPgb1 expression was measured from a group of selected waterlogging-tolerant and susceptible genotypes. A sharp increase in gene expression was seen in the leaves of waterlogged tolerant genotypes, thus positioning HvPgb1 expression as a potential molecular marker for waterlogging tolerance in barley.

Reclamation and revegetation of boreal sites disturbed by oil exploration depend on the availability of topsoil salvaged on-site during the disturbance. For successful reclamation, current regulations require the salvaging of enough soil to attain at least 80% of the original topsoil depth. However, salvaged topsoil at many sites is often insufficient to achieve the 80% topsoil replacement depth (TRD80) required for successful reclamation in western Canada. We tested organic amendment effects on reclamation success of wellsites reclaimed with insufficient salvaged topsoil to a level similar to the mandatory TRD80. Two main studies were conducted to examine (i) soil responses and (ii) vegetation responses to 50% topsoil replacement depth without organic amendment (TRD50) or amended with either peat (PTRD50) or biochar (BTRD50), relative to the TRD80 treatment, following wellsite reclamation at Cold Lake, Alberta. Soil properties results showed that both amendments improved topsoil properties. Peat-amended plots showed a 113% increase in total Kjeldahl nitrogen concentration relative to the mean of other treatments, while biochar produced significantly greater potassium concentrations in TRD50 relative to peat-amended plots. Vegetation responses to insufficient topsoil depth and organic amendment application showed an increase in native species, graminoid and woody species richness while non-native and forb species richness decreased across all treatments 5 yr after reclamation. Tree growth was greater in the peat amendment and the TRD80 treatment than in the TRD50 and the biochar treatments. Peat and biochar improved soil properties of disturbed boreal sites reclaimed with insufficient salvaged topsoil to a level suitable for successful restoration. However, in the revegetation study peat improved vegetation establishment and plant community development while biochar showed no benefits on vegetation variables. Overall, the peat treatment (PTRD50) produced similar veg

Barley (Hordeum vulgare L.) is the most susceptible cereal species to excess moisture stress. Waterlogging-induced hypoxia causes major physiological changes that disrupt the photosynthetic machinery of seedlings. The signaling molecule nitric oxide (NO) regulates numerous metabolic processes but increases to toxic levels during hypoxia. Phytoglobin1 (Pgb1) functions as a NO-scavenging hemeprotein that influences hypoxic stress responses such as ethylene-mediated adaptations and nitrate use. This study demonstrated that overexpression of HvPgb1 maintains photosynthetic rate in barley during waterlogging, but also confirms previously reported decreases in physiological performance during normoxic (control) conditions. Foliar ethylene was found to decrease in waterlogged wild type (WT) but remain unchanged in the HvPgb1-overexpressing line [HvPgb1(OE)]. It is proposed that ACC from the hypoxic root mobilizes to the shoot, where it induces HvPgb1 activity and nitrate generation. Foliar nitrate was measured as well and showed a significant increase in leaves of waterlogged HvPgb1(OE) plants, while remaining unchanged in waterlogged WT leaves. These changes were associated to a putative increased in the levels of polyamines. Finally, HvPgb1 expression was measured from a group of selected waterlogging-tolerant and susceptible genotypes. A sharp increase in gene expression was seen in the leaves of waterlogged tolerant genotypes, thus positioning HvPgb1 expression as a potential molecular marker for waterlogging tolerance in barley.

UV-B and UV-C can damage DNA by generating DNA photoproducts such as cyclobutane pyrimidine dimers (CPDs), pyrimidine 6-4 pyrimidone (6-4 PPs) and its Dewar isomers (Dewar PP). These DNA photoproducts inhibit DNA transcription and replication, and cause mutations. Thus, DNA photoproducts must be repaired. Plants use two different mechanisms to repair these DNA photoproducts: light-dependent repair via photolyase and light-independent repair via nucleotide excision repair (NER). The NER mechanism in plants is similar to that elucidated in yeast and mammalian models. In yeast systems, the global genomic NER (GG-NER) damage recognition complex RAD7/RAD16/ELOC/ CUL3 recognizes the damaged DNA in the non-transcribed regions of the genome. The mammalian Elongin A/B/C/CUL5 /RBX2 and the yeast Elongin A/C/CUL3/RBX1 complexes target the large subunit of the lesion stalled RNAPII on the transcribed strand for ubiqitination and degradation. Arabidopsis has two RAD16 homologs: AtRAD16 and AtRAD16b. In this thesis, I characterized the role of AtRAD16 and AtRAD16b in plant UV tolerance and growth using loss of function and gain of function analysis. Atrad16 and Atrad16b null mutants exhibited increased UV sensitivity, early flowering time and short silique length. AtRAD16 overexpression increased UV resistance, and YFP-tagged RAD16 is localized in the nucleus. In addition, AtRAD16 physically interacts with AtRAD7, all these results indicate that the role of AtRAD16 in GG-NER is conserved with its yeast counterpart. I also identified Arabidopsis ELOA homolog, ELOA, and characterized the role of both Arabidopsis ELOA and ELOC homologs in plant UV tolerance and growth. Ateloa and Ateloc null mutants exhibited increased UV sensitivity in seedlings and adult plants. AtELOA was found to physically and genetically interact with AtELOC. AtELOA is nuclear localized, whereas AtELOC localized in the nuclei and the cytosol. ELOA overexpression increases hypocotyl UV resistance and ELOA/ELOC

Reclamation and revegetation of boreal sites disturbed by oil exploration depend on the availability of topsoil salvaged on-site during the disturbance. For successful reclamation, current regulations require the salvaging of enough soil to attain at least 80% of the original topsoil depth. However, salvaged topsoil at many sites is often insufficient to achieve the 80% topsoil replacement depth (TRD80) required for successful reclamation in western Canada. We tested organic amendment effects on reclamation success of wellsites reclaimed with insufficient salvaged topsoil to a level similar to the mandatory TRD80. Two main studies were conducted to examine (i) soil responses and (ii) vegetation responses to 50% topsoil replacement depth without organic amendment (TRD50) or amended with either peat (PTRD50) or biochar (BTRD50), relative to the TRD80 treatment, following wellsite reclamation at Cold Lake, Alberta. Soil properties results showed that both amendments improved topsoil properties. Peat-amended plots showed a 113% increase in total Kjeldahl nitrogen concentration relative to the mean of other treatments, while biochar produced significantly greater potassium concentrations in TRD50 relative to peat-amended plots. Vegetation responses to insufficient topsoil depth and organic amendment application showed an increase in native species, graminoid and woody species richness while non-native and forb species richness decreased across all treatments 5 yr after reclamation. Tree growth was greater in the peat amendment and the TRD80 treatment than in the TRD50 and the biochar treatments. Peat and biochar improved soil properties of disturbed boreal sites reclaimed with insufficient salvaged topsoil to a level suitable for successful restoration. However, in the revegetation study peat improved vegetation establishment and plant community development while biochar showed no benefits on vegetation variables. Overall, the peat treatment (PTRD50) produced similar veg

Barley (Hordeum vulgare L.) is the most susceptible cereal species to excess moisture stress. Waterlogging-induced hypoxia causes major physiological changes that disrupt the photosynthetic machinery of seedlings. The signaling molecule nitric oxide (NO) regulates numerous metabolic processes but increases to toxic levels during hypoxia. Phytoglobin1 (Pgb1) functions as a NO-scavenging hemeprotein that influences hypoxic stress responses such as ethylene-mediated adaptations and nitrate use. This study demonstrated that overexpression of HvPgb1 maintains photosynthetic rate in barley during waterlogging, but also confirms previously reported decreases in physiological performance during normoxic (control) conditions. Foliar ethylene was found to decrease in waterlogged wild type (WT) but remain unchanged in the HvPgb1-overexpressing line [HvPgb1(OE)]. It is proposed that ACC from the hypoxic root mobilizes to the shoot, where it induces HvPgb1 activity and nitrate generation. Foliar nitrate was measured as well and showed a significant increase in leaves of waterlogged HvPgb1(OE) plants, while remaining unchanged in waterlogged WT leaves. These changes were associated to a putative increased in the levels of polyamines. Finally, HvPgb1 expression was measured from a group of selected waterlogging-tolerant and susceptible genotypes. A sharp increase in gene expression was seen in the leaves of waterlogged tolerant genotypes, thus positioning HvPgb1 expression as a potential molecular marker for waterlogging tolerance in barley.

Fusarium head blight (FHB) is an important fungal disease of wheat predominantly caused by Fusarium graminearum. FHB infection in cereal crops leads to yield loss and decreased grain quality due to accumulation of mycotoxins such as deoxynivalenol. Many highly FHB resistant wheat cultivars are tall and are prone to lodging. Application of plant growth regulators (PGRs) to tall cultivars with the highest level of FHB resistant could prevent wheat from lodging and overcome the negative association between shorter plants and FHB susceptibility. The objectives of this study were to investigate the effect of PGRs on FHB infection and anther retention in spring wheat cultivars. Two commercially available PGRs, Manipulator™ and Ethrel™, were applied to five spring wheat (Triticum aestivum L.) cultivars which differed in height, FHB resistance level and semi-dwarfing alleles. Results from this study showed Ethrel™ reduced plant height under field and controlled environments conditions. Under field conditions, PGRs did not influence anther retention and FHB infection in spring wheat. In contrast, in controlled environment conditions, Manipulator™ decreased anther retention, while Ethrel™ increased anther retention. Treatment with Manipulator™ showed conflicting results on the accumulation of F. graminearum DNA in the spike. The Ethrel™ treatment showed that accumulation of F. graminearum DNA is genotype specific. Overall, the performance of PGRs on height, anther retention and FHB infection were influenced by environmental conditions.

Soybean production is negatively affected by certain morphology related factors such as the occurrence of short lowest pod height which results in stubble losses since the pods lower than the reach of the combine cutter are lost during harvest. Therefore, it is necessary to develop strategies that can promote the elongation of lower internodes such that the first pods can be set at a harvestable height. Plant hormones such as gibberellins (GA) and cytokinins play important roles in regulating stem elongation through promoting cell elongation and cell division, respectively. Therefore, plant growth regulators (PGRs) containing GAs and cytokinins can promote internode elongation and therefore the height of lowest pod bearing nodes. Using a soybean cultivar characterized by a short lowest pod height, this thesis investigated the effects of GA and/or cytokinin based PGRs, applied as a seed treatment, on enhancing the elongation of lower internodes and thereby lowest pod height. The findings show that the GA based PGR was effective in increasing the lengths of lower internodes and height of the lowest pods. In order to gain insights into the molecular basis of GA metabolism in the regulation of pod heights, this thesis examined the expression patterns of GA biosynthetic and catabolism genes in lower internodes of three different soybean cultivars with contrasting pod heights. The results indicate that the three cultivars exhibit differential expression patterns of the genes analyzed.

In the nitrogen-fixing clade, only 10 out of 28 plant families retain the nitrogen fixation trait. It is thought that the nitrogen fixation has been lost repeatedly since it evolved. Exploring the potential abiotic and biotic factors that trigger the loss of nitrogen-fixing traits is critical to understanding the evolution and ecology of plants. I designed three studies to examine how nitrogen-fixing plants respond to N deposition, different levels of CO2, herbivore damage, and less-effective symbionts. For the first study I grew three nitrogen fixers (Alnus incana ssp. rugosa, Alnus viridis ssp. crispa, and Alnus rubra) and their close non-nitrogen fixing relatives (Betula pumila, Betula papyrifera, Betula glandulosa) at ancient (1600 ppm) or present (400 ppm) CO2 over a range of soil N levels, equivalent to 0, 10, 50, and 200 kg N ha-1 year-1. I found nitrogen-fixing plants were less competitive as soil N increased compared with non-N fixers, but at ancient CO2 levels nitrogen-fixing plants are at an advantage at higher soil N levels. The seconded study explored the interaction between Alnus incana ssp. rugosa and Orgyia leucostigma under ambient (400 ppm), future (800 ppm), and ancient (1600 ppm) CO2. Herbivores preferred to feed on nodulated plant leaves grown at 400 ppm and 1600 ppm when given a choice, compared with non-nodulated leaves. At 800 ppm CO2 nodulated plants accumulated more total phenolic compounds in response to herbivore damage than plants in the non-Frankia and non-herbivore treatments. The third study examined if Alnus spp. can select against less-effective symbiont via partner choice or sanctioning. In a co-inoculation experiment, host plants could not prevent the less effective sp+ Frankia from entering roots when inoculated with a mixture of effective (sp-) and less effective (sp+) Frankia. When plant roots were inoculated with sp+ Frankia and exposed to Argon to induce Frankia cheating, specific nodule mass was not reduced. However, Argon-t

Fusarium head blight (FHB) is an important fungal disease of wheat predominantly caused by Fusarium graminearum. FHB infection in cereal crops leads to yield loss and decreased grain quality due to accumulation of mycotoxins such as deoxynivalenol. Many highly FHB resistant wheat cultivars are tall and are prone to lodging. Application of plant growth regulators (PGRs) to tall cultivars with the highest level of FHB resistant could prevent wheat from lodging and overcome the negative association between shorter plants and FHB susceptibility. The objectives of this study were to investigate the effect of PGRs on FHB infection and anther retention in spring wheat cultivars. Two commercially available PGRs, Manipulator™ and Ethrel™, were applied to five spring wheat (Triticum aestivum L.) cultivars which differed in height, FHB resistance level and semi-dwarfing alleles. Results from this study showed Ethrel™ reduced plant height under field and controlled environments conditions. Under field conditions, PGRs did not influence anther retention and FHB infection in spring wheat. In contrast, in controlled environment conditions, Manipulator™ decreased anther retention, while Ethrel™ increased anther retention. Treatment with Manipulator™ showed conflicting results on the accumulation of F. graminearum DNA in the spike. The Ethrel™ treatment showed that accumulation of F. graminearum DNA is genotype specific. Overall, the performance of PGRs on height, anther retention and FHB infection were influenced by environmental conditions.

Fusarium head blight (FHB) is an important fungal disease of wheat predominantly caused by Fusarium graminearum. FHB infection in cereal crops leads to yield loss and decreased grain quality due to accumulation of mycotoxins such as deoxynivalenol. Many highly FHB resistant wheat cultivars are tall and are prone to lodging. Application of plant growth regulators (PGRs) to tall cultivars with the highest level of FHB resistant could prevent wheat from lodging and overcome the negative association between shorter plants and FHB susceptibility. The objectives of this study were to investigate the effect of PGRs on FHB infection and anther retention in spring wheat cultivars. Two commercially available PGRs, Manipulator™ and Ethrel™, were applied to five spring wheat (Triticum aestivum L.) cultivars which differed in height, FHB resistance level and semi-dwarfing alleles. Results from this study showed Ethrel™ reduced plant height under field and controlled environments conditions. Under field conditions, PGRs did not influence anther retention and FHB infection in spring wheat. In contrast, in controlled environment conditions, Manipulator™ decreased anther retention, while Ethrel™ increased anther retention. Treatment with Manipulator™ showed conflicting results on the accumulation of F. graminearum DNA in the spike. The Ethrel™ treatment showed that accumulation of F. graminearum DNA is genotype specific. Overall, the performance of PGRs on height, anther retention and FHB infection were influenced by environmental conditions.

Soybean production is negatively affected by certain morphology related factors such as the occurrence of short lowest pod height which results in stubble losses since the pods lower than the reach of the combine cutter are lost during harvest. Therefore, it is necessary to develop strategies that can promote the elongation of lower internodes such that the first pods can be set at a harvestable height. Plant hormones such as gibberellins (GA) and cytokinins play important roles in regulating stem elongation through promoting cell elongation and cell division, respectively. Therefore, plant growth regulators (PGRs) containing GAs and cytokinins can promote internode elongation and therefore the height of lowest pod bearing nodes. Using a soybean cultivar characterized by a short lowest pod height, this thesis investigated the effects of GA and/or cytokinin based PGRs, applied as a seed treatment, on enhancing the elongation of lower internodes and thereby lowest pod height. The findings show that the GA based PGR was effective in increasing the lengths of lower internodes and height of the lowest pods. In order to gain insights into the molecular basis of GA metabolism in the regulation of pod heights, this thesis examined the expression patterns of GA biosynthetic and catabolism genes in lower internodes of three different soybean cultivars with contrasting pod heights. The results indicate that the three cultivars exhibit differential expression patterns of the genes analyzed.

In the nitrogen-fixing clade, only 10 out of 28 plant families retain the nitrogen fixation trait. It is thought that the nitrogen fixation has been lost repeatedly since it evolved. Exploring the potential abiotic and biotic factors that trigger the loss of nitrogen-fixing traits is critical to understanding the evolution and ecology of plants. I designed three studies to examine how nitrogen-fixing plants respond to N deposition, different levels of CO2, herbivore damage, and less-effective symbionts. For the first study I grew three nitrogen fixers (Alnus incana ssp. rugosa, Alnus viridis ssp. crispa, and Alnus rubra) and their close non-nitrogen fixing relatives (Betula pumila, Betula papyrifera, Betula glandulosa) at ancient (1600 ppm) or present (400 ppm) CO2 over a range of soil N levels, equivalent to 0, 10, 50, and 200 kg N ha-1 year-1. I found nitrogen-fixing plants were less competitive as soil N increased compared with non-N fixers, but at ancient CO2 levels nitrogen-fixing plants are at an advantage at higher soil N levels. The seconded study explored the interaction between Alnus incana ssp. rugosa and Orgyia leucostigma under ambient (400 ppm), future (800 ppm), and ancient (1600 ppm) CO2. Herbivores preferred to feed on nodulated plant leaves grown at 400 ppm and 1600 ppm when given a choice, compared with non-nodulated leaves. At 800 ppm CO2 nodulated plants accumulated more total phenolic compounds in response to herbivore damage than plants in the non-Frankia and non-herbivore treatments. The third study examined if Alnus spp. can select against less-effective symbiont via partner choice or sanctioning. In a co-inoculation experiment, host plants could not prevent the less effective sp+ Frankia from entering roots when inoculated with a mixture of effective (sp-) and less effective (sp+) Frankia. When plant roots were inoculated with sp+ Frankia and exposed to Argon to induce Frankia cheating, specific nodule mass was not reduced. However, Argon-t

Fusarium head blight (FHB) is an important fungal disease of wheat predominantly caused by Fusarium graminearum. FHB infection in cereal crops leads to yield loss and decreased grain quality due to accumulation of mycotoxins such as deoxynivalenol. Many highly FHB resistant wheat cultivars are tall and are prone to lodging. Application of plant growth regulators (PGRs) to tall cultivars with the highest level of FHB resistant could prevent wheat from lodging and overcome the negative association between shorter plants and FHB susceptibility. The objectives of this study were to investigate the effect of PGRs on FHB infection and anther retention in spring wheat cultivars. Two commercially available PGRs, Manipulator™ and Ethrel™, were applied to five spring wheat (Triticum aestivum L.) cultivars which differed in height, FHB resistance level and semi-dwarfing alleles. Results from this study showed Ethrel™ reduced plant height under field and controlled environments conditions. Under field conditions, PGRs did not influence anther retention and FHB infection in spring wheat. In contrast, in controlled environment conditions, Manipulator™ decreased anther retention, while Ethrel™ increased anther retention. Treatment with Manipulator™ showed conflicting results on the accumulation of F. graminearum DNA in the spike. The Ethrel™ treatment showed that accumulation of F. graminearum DNA is genotype specific. Overall, the performance of PGRs on height, anther retention and FHB infection were influenced by environmental conditions.

Plant growth-promoting bacteria (PGPB) are a heterogeneous group of soil microbes that confer beneficial effects to plants. Recent interest in sustainable and organic agriculture has highlighted the potential uses of PGPB as agricultural adjuncts. Currently, PGPB are used to increase crop yield and productivity. Substantial work has been done on the active metabolites secreted by PGPB that drive plant growth. However, little is known about their effects on the global transcriptome of the host plant. P. chlororaphis PA23 is a gram-negative bacterium that has shown great potential as a plant growth promoting agent. Using a combination of next-generation RNA sequencing and bioinformatic analyses, the mechanisms that underlie P. chlororaphis PA23 induced growth in Brassica napus seedlings were investigated. The results showed that P. chlororaphis modulates plant phytohormone signaling systems resulting in elevated expression levels of genes associated with photosynthesis and root hair development. Next, the scalability of P. chlororaphis PA23 as an agricultural adjunct with a Glycine max field study was investigated. An increase in soybean pod set following P. chlororaphis PA23 treatment was observed, suggesting plant growth-promoting activity under field conditions. To determine the effects of P. chlororaphis PA23 on the microbial communities found in the soil, a combination of marker-based sequencing and bioinformatic analyses were utilized. Here I report that the addition of P. chlororaphis PA23 does not alter the bacterial or fungal species diversity. Furthermore, I report that the community composition within the rhizosphere does not change in response to P. chlororaphis PA23. This research provides the necessary information for the development of P. chlororaphis PA23 as an agricultural adjunct and lays the foundation for multi-year field studies that integrate the utilization of P. chlororaphis PA23 as a PGPB.

Plant growth-promoting bacteria (PGPB) are a heterogeneous group of soil microbes that confer beneficial effects to plants. Recent interest in sustainable and organic agriculture has highlighted the potential uses of PGPB as agricultural adjuncts. Currently, PGPB are used to increase crop yield and productivity. Substantial work has been done on the active metabolites secreted by PGPB that drive plant growth. However, little is known about their effects on the global transcriptome of the host plant. P. chlororaphis PA23 is a gram-negative bacterium that has shown great potential as a plant growth promoting agent. Using a combination of next-generation RNA sequencing and bioinformatic analyses, the mechanisms that underlie P. chlororaphis PA23 induced growth in Brassica napus seedlings were investigated. The results showed that P. chlororaphis modulates plant phytohormone signaling systems resulting in elevated expression levels of genes associated with photosynthesis and root hair development. Next, the scalability of P. chlororaphis PA23 as an agricultural adjunct with a Glycine max field study was investigated. An increase in soybean pod set following P. chlororaphis PA23 treatment was observed, suggesting plant growth-promoting activity under field conditions. To determine the effects of P. chlororaphis PA23 on the microbial communities found in the soil, a combination of marker-based sequencing and bioinformatic analyses were utilized. Here I report that the addition of P. chlororaphis PA23 does not alter the bacterial or fungal species diversity. Furthermore, I report that the community composition within the rhizosphere does not change in response to P. chlororaphis PA23. This research provides the necessary information for the development of P. chlororaphis PA23 as an agricultural adjunct and lays the foundation for multi-year field studies that integrate the utilization of P. chlororaphis PA23 as a PGPB.

The short growing season and cold climate of the Canadian boreal forest can result in restricted amounts of available soil nitrogen, limited plant growth and low ecosystem productivity. Nitrogen fixing plants, which form symbiotic relationships with specialised bacteria, should have an advantage in low nitrogen environments, yet, their abundance in the boreal forest is low. Cool temperatures limit nitrogen fixation activity. How nitrogen fixation is affected when temperature differences occur between the soil and air, especially in the spring when soil temperatures remain cool, have not been well documented. To investigate this, two studies were conducted on the nitrogen fixing shrub Alnus alnobetula subsp. crispa (Aiton) Raus. In 2017, nitrogen fixation was monitored in both open and forested sites in the southern boreal forest. Nitrogen fixation activity began in mid June, was highest in early August at a soil temperature of 20˚C, and ceased in early October. The difference between soil and air temperature was largest in the spring. Soil temperature did not have an effect on nitrogen fixation until after bud burst and leaf development. In the open site, soil temperature warmed at an earlier date compared to the forested site. However there was no difference in nitrogen fixation rate between the sites. Soil moisture had no effect on nitrogen fixation. To examine the effects of extended delays in soil warming, past leaf development, a lab study was performed. For a period of thirteen weeks, soil was cooled to 10˚C, 14˚C and 16˚C, independently of shoot temperature (20˚C). On average, soils at 14˚C and 10˚C inhibited nitrogen fixation (by 29% and 62%, respectively) and photosynthesis (by 43% and 39%). Reductions in photosynthetic rate were mainly attributed to a reduction in nitrogen supply and the formation of new chlorophyll pigment. Although this effect was not immediate, suggesting some utilization of stored nitrogen. Reduced amounts of fixed nitrogen and photosy

The short growing season and cold climate of the Canadian boreal forest can result in restricted amounts of available soil nitrogen, limited plant growth and low ecosystem productivity. Nitrogen fixing plants, which form symbiotic relationships with specialised bacteria, should have an advantage in low nitrogen environments, yet, their abundance in the boreal forest is low. Cool temperatures limit nitrogen fixation activity. How nitrogen fixation is affected when temperature differences occur between the soil and air, especially in the spring when soil temperatures remain cool, have not been well documented. To investigate this, two studies were conducted on the nitrogen fixing shrub Alnus alnobetula subsp. crispa (Aiton) Raus. In 2017, nitrogen fixation was monitored in both open and forested sites in the southern boreal forest. Nitrogen fixation activity began in mid June, was highest in early August at a soil temperature of 20˚C, and ceased in early October. The difference between soil and air temperature was largest in the spring. Soil temperature did not have an effect on nitrogen fixation until after bud burst and leaf development. In the open site, soil temperature warmed at an earlier date compared to the forested site. However there was no difference in nitrogen fixation rate between the sites. Soil moisture had no effect on nitrogen fixation. To examine the effects of extended delays in soil warming, past leaf development, a lab study was performed. For a period of thirteen weeks, soil was cooled to 10˚C, 14˚C and 16˚C, independently of shoot temperature (20˚C). On average, soils at 14˚C and 10˚C inhibited nitrogen fixation (by 29% and 62%, respectively) and photosynthesis (by 43% and 39%). Reductions in photosynthetic rate were mainly attributed to a reduction in nitrogen supply and the formation of new chlorophyll pigment. Although this effect was not immediate, suggesting some utilization of stored nitrogen. Reduced amounts of fixed nitrogen and photosy

The short growing season and cold climate of the Canadian boreal forest can result in restricted amounts of available soil nitrogen, limited plant growth and low ecosystem productivity. Nitrogen fixing plants, which form symbiotic relationships with specialised bacteria, should have an advantage in low nitrogen environments, yet, their abundance in the boreal forest is low. Cool temperatures limit nitrogen fixation activity. How nitrogen fixation is affected when temperature differences occur between the soil and air, especially in the spring when soil temperatures remain cool, have not been well documented. To investigate this, two studies were conducted on the nitrogen fixing shrub Alnus alnobetula subsp. crispa (Aiton) Raus. In 2017, nitrogen fixation was monitored in both open and forested sites in the southern boreal forest. Nitrogen fixation activity began in mid June, was highest in early August at a soil temperature of 20˚C, and ceased in early October. The difference between soil and air temperature was largest in the spring. Soil temperature did not have an effect on nitrogen fixation until after bud burst and leaf development. In the open site, soil temperature warmed at an earlier date compared to the forested site. However there was no difference in nitrogen fixation rate between the sites. Soil moisture had no effect on nitrogen fixation. To examine the effects of extended delays in soil warming, past leaf development, a lab study was performed. For a period of thirteen weeks, soil was cooled to 10˚C, 14˚C and 16˚C, independently of shoot temperature (20˚C). On average, soils at 14˚C and 10˚C inhibited nitrogen fixation (by 29% and 62%, respectively) and photosynthesis (by 43% and 39%). Reductions in photosynthetic rate were mainly attributed to a reduction in nitrogen supply and the formation of new chlorophyll pigment. Although this effect was not immediate, suggesting some utilization of stored nitrogen. Reduced amounts of fixed nitrogen and photosy

The short growing season and cold climate of the Canadian boreal forest can result in restricted amounts of available soil nitrogen, limited plant growth and low ecosystem productivity. Nitrogen fixing plants, which form symbiotic relationships with specialised bacteria, should have an advantage in low nitrogen environments, yet, their abundance in the boreal forest is low. Cool temperatures limit nitrogen fixation activity. How nitrogen fixation is affected when temperature differences occur between the soil and air, especially in the spring when soil temperatures remain cool, have not been well documented. To investigate this, two studies were conducted on the nitrogen fixing shrub Alnus alnobetula subsp. crispa (Aiton) Raus. In 2017, nitrogen fixation was monitored in both open and forested sites in the southern boreal forest. Nitrogen fixation activity began in mid June, was highest in early August at a soil temperature of 20˚C, and ceased in early October. The difference between soil and air temperature was largest in the spring. Soil temperature did not have an effect on nitrogen fixation until after bud burst and leaf development. In the open site, soil temperature warmed at an earlier date compared to the forested site. However there was no difference in nitrogen fixation rate between the sites. Soil moisture had no effect on nitrogen fixation. To examine the effects of extended delays in soil warming, past leaf development, a lab study was performed. For a period of thirteen weeks, soil was cooled to 10˚C, 14˚C and 16˚C, independently of shoot temperature (20˚C). On average, soils at 14˚C and 10˚C inhibited nitrogen fixation (by 29% and 62%, respectively) and photosynthesis (by 43% and 39%). Reductions in photosynthetic rate were mainly attributed to a reduction in nitrogen supply and the formation of new chlorophyll pigment. Although this effect was not immediate, suggesting some utilization of stored nitrogen. Reduced amounts of fixed nitrogen and photosy

The fungal pathogen, Fusarium graminearum, is a primary causal agent of the wheat (Triticum aestivum L.) disease Fusarium head blight in North America. Heavy infection from this pathogen leads to economic losses due to a decrease in the quality and quantity of grain. Infection by F. graminearum also leads to accumulation of deoxynivalenol (DON), a mycotoxin that produces harmful side effects to both humans and animals when ingested. Development of resistant wheat cultivars is needed to maintain a sustainable, safe, food supply. In this study, a double haploid population derived from a cross between two winter wheat cultivars, Flourish and Emerson, was used to identify quantitative trait loci (QTL) associated with FHB symptoms and DON accumulation in the grain. So far, there are no fully resistant cultivars of wheat to protect against FHB infection. Therefore, alternative methods need to be considered. A newly developed bio-fungicide containing a fungal antagonist to F. graminearum, Clonostachys rosea, was studied and compared to the commercially available fungicide, Caramba® (active ingredient, metconazole). These QTL were present on chromosomes 1B, 2B, 4D, 6D and 7A. Results from this study showed that there was some potential in using C. rosea in a bio-fungicide treatment plan. However, the fungi’s sensitivity to environmental conditions may have contributed to poor and inconsistent control of F. graminearum in this study.

Solid waste management and landfill leachate has been investigated widely for waste treatment and environmental safety. This study aimed to 1) remove organic contaminants from landfill leachate by sole or combined biological and chemical methods, 2) investigate the solid waste management situations in Canadian First Nations communities, 3) evaluate the feasibility of landfill leachate for plants irrigation, and 4) remove nutrients and salinity from leachate and soil by means of phytoremediation. Aerobic sequencing batch reactor (SBR) with activated sludge was used as the biological treatment to remove ammonium. The chemical treatments included ozone (O3), ozone + hydrogen peroxide (O3 + H2O2), Fenton’s reagents (H2O2 + Fe2+), and ozone + Fenton’s reagents (O3 + H2O2 + Fe2+). Results indicated that ozonation of raw leachate achieved 16% COD removal after 240 min of treatment while O3 + H2O2 achieved 33% COD removal of raw leachate with 900 mg/L H2O2 in 120 min. Moreover, the COD removal from raw leachate was only 33% by using Fenton’s reagents. After biological stabilization, ozonation removed 52% of the COD within 240 min. The Fenton’s reagents achieved 67% COD removal using equal doses of H2O2 and Fe2+. However, Fenton’s reagents in conjunction with O3 removed 69% and 72% COD in 120 min and 240 min, respectively. The dosage test also revealed that the 2:1 ratio of H2O2 and Fe2+ had the best COD removal. Two native halophytes Puccinellia nuttalliana (Alkaligrass) and Typha latifolia (Cattail) were selected in this study to investigate bioaccumulation of Sodium (Na+) and Chloride (Cl-) in greenhouse condition. Different treatments were applied on same soil condition, namely control (C), fertilizer (F) and diluted landfill leachate (LL). The results shown that alkaligrass and cattail accumulated 6.86±0.96 and 7.00±0.20 g Na+/Kg biomass with the irrigation of LL, respectively. Alkaligrass and cattail irrigated with LL accumulated 120.15% and 94.48% more Cl- than contro

The effect of drought stress on 3-leaf stage (V2) maize (Zea mays L.) seedlings over-expressing or down-regulating the Zea mays phytoglobin 1 gene (ZmPgb1) was investigated using applications of 25% w/v polyethylene glycol (PEG) to mimic drought. Over-expression of ZmPgb1 increased drought tolerance, decreased wilting, and decreased the accumulation of ethylene and reactive oxygen species (ROS), compared to wild type (WT) plants and plants in which the level of ZmPgb1 was down-regulated. Gene expression studies conducted during the first 16 hours of water stress revealed a transcriptional induction of ethylene synthesis and response, as well as ROS production, in the ZmPgb1 down-regulating plants relative to WT plants. This was in contrast to the ZmPgb1 over-expressing plants where genes participating in ethylene synthesis and response exhibited the lowest expression levels, and ROS production was also limited. Based on these results, a model is proposed in which suppression of NO signalling by ZmPgb1 reduces ethylene accumulation and response, and production of ROS, which are conditions alleviating drought stress.

The fungal pathogen, Fusarium graminearum, is a primary causal agent of the wheat (Triticum aestivum L.) disease Fusarium head blight in North America. Heavy infection from this pathogen leads to economic losses due to a decrease in the quality and quantity of grain. Infection by F. graminearum also leads to accumulation of deoxynivalenol (DON), a mycotoxin that produces harmful side effects to both humans and animals when ingested. Development of resistant wheat cultivars is needed to maintain a sustainable, safe, food supply. In this study, a double haploid population derived from a cross between two winter wheat cultivars, Flourish and Emerson, was used to identify quantitative trait loci (QTL) associated with FHB symptoms and DON accumulation in the grain. So far, there are no fully resistant cultivars of wheat to protect against FHB infection. Therefore, alternative methods need to be considered. A newly developed bio-fungicide containing a fungal antagonist to F. graminearum, Clonostachys rosea, was studied and compared to the commercially available fungicide, Caramba® (active ingredient, metconazole). These QTL were present on chromosomes 1B, 2B, 4D, 6D and 7A. Results from this study showed that there was some potential in using C. rosea in a bio-fungicide treatment plan. However, the fungi’s sensitivity to environmental conditions may have contributed to poor and inconsistent control of F. graminearum in this study.

Solid waste management and landfill leachate has been investigated widely for waste treatment and environmental safety. This study aimed to 1) remove organic contaminants from landfill leachate by sole or combined biological and chemical methods, 2) investigate the solid waste management situations in Canadian First Nations communities, 3) evaluate the feasibility of landfill leachate for plants irrigation, and 4) remove nutrients and salinity from leachate and soil by means of phytoremediation. Aerobic sequencing batch reactor (SBR) with activated sludge was used as the biological treatment to remove ammonium. The chemical treatments included ozone (O3), ozone + hydrogen peroxide (O3 + H2O2), Fenton’s reagents (H2O2 + Fe2+), and ozone + Fenton’s reagents (O3 + H2O2 + Fe2+). Results indicated that ozonation of raw leachate achieved 16% COD removal after 240 min of treatment while O3 + H2O2 achieved 33% COD removal of raw leachate with 900 mg/L H2O2 in 120 min. Moreover, the COD removal from raw leachate was only 33% by using Fenton’s reagents. After biological stabilization, ozonation removed 52% of the COD within 240 min. The Fenton’s reagents achieved 67% COD removal using equal doses of H2O2 and Fe2+. However, Fenton’s reagents in conjunction with O3 removed 69% and 72% COD in 120 min and 240 min, respectively. The dosage test also revealed that the 2:1 ratio of H2O2 and Fe2+ had the best COD removal. Two native halophytes Puccinellia nuttalliana (Alkaligrass) and Typha latifolia (Cattail) were selected in this study to investigate bioaccumulation of Sodium (Na+) and Chloride (Cl-) in greenhouse condition. Different treatments were applied on same soil condition, namely control (C), fertilizer (F) and diluted landfill leachate (LL). The results shown that alkaligrass and cattail accumulated 6.86±0.96 and 7.00±0.20 g Na+/Kg biomass with the irrigation of LL, respectively. Alkaligrass and cattail irrigated with LL accumulated 120.15% and 94.48% more Cl- than contro

The effect of drought stress on 3-leaf stage (V2) maize (Zea mays L.) seedlings over-expressing or down-regulating the Zea mays phytoglobin 1 gene (ZmPgb1) was investigated using applications of 25% w/v polyethylene glycol (PEG) to mimic drought. Over-expression of ZmPgb1 increased drought tolerance, decreased wilting, and decreased the accumulation of ethylene and reactive oxygen species (ROS), compared to wild type (WT) plants and plants in which the level of ZmPgb1 was down-regulated. Gene expression studies conducted during the first 16 hours of water stress revealed a transcriptional induction of ethylene synthesis and response, as well as ROS production, in the ZmPgb1 down-regulating plants relative to WT plants. This was in contrast to the ZmPgb1 over-expressing plants where genes participating in ethylene synthesis and response exhibited the lowest expression levels, and ROS production was also limited. Based on these results, a model is proposed in which suppression of NO signalling by ZmPgb1 reduces ethylene accumulation and response, and production of ROS, which are conditions alleviating drought stress.

The fungal pathogen, Fusarium graminearum, is a primary causal agent of the wheat (Triticum aestivum L.) disease Fusarium head blight in North America. Heavy infection from this pathogen leads to economic losses due to a decrease in the quality and quantity of grain. Infection by F. graminearum also leads to accumulation of deoxynivalenol (DON), a mycotoxin that produces harmful side effects to both humans and animals when ingested. Development of resistant wheat cultivars is needed to maintain a sustainable, safe, food supply. In this study, a double haploid population derived from a cross between two winter wheat cultivars, Flourish and Emerson, was used to identify quantitative trait loci (QTL) associated with FHB symptoms and DON accumulation in the grain. So far, there are no fully resistant cultivars of wheat to protect against FHB infection. Therefore, alternative methods need to be considered. A newly developed bio-fungicide containing a fungal antagonist to F. graminearum, Clonostachys rosea, was studied and compared to the commercially available fungicide, Caramba® (active ingredient, metconazole). These QTL were present on chromosomes 1B, 2B, 4D, 6D and 7A. Results from this study showed that there was some potential in using C. rosea in a bio-fungicide treatment plan. However, the fungi’s sensitivity to environmental conditions may have contributed to poor and inconsistent control of F. graminearum in this study.

The fungal pathogen, Fusarium graminearum, is a primary causal agent of the wheat (Triticum aestivum L.) disease Fusarium head blight in North America. Heavy infection from this pathogen leads to economic losses due to a decrease in the quality and quantity of grain. Infection by F. graminearum also leads to accumulation of deoxynivalenol (DON), a mycotoxin that produces harmful side effects to both humans and animals when ingested. Development of resistant wheat cultivars is needed to maintain a sustainable, safe, food supply. In this study, a double haploid population derived from a cross between two winter wheat cultivars, Flourish and Emerson, was used to identify quantitative trait loci (QTL) associated with FHB symptoms and DON accumulation in the grain. So far, there are no fully resistant cultivars of wheat to protect against FHB infection. Therefore, alternative methods need to be considered. A newly developed bio-fungicide containing a fungal antagonist to F. graminearum, Clonostachys rosea, was studied and compared to the commercially available fungicide, Caramba® (active ingredient, metconazole). These QTL were present on chromosomes 1B, 2B, 4D, 6D and 7A. Results from this study showed that there was some potential in using C. rosea in a bio-fungicide treatment plan. However, the fungi’s sensitivity to environmental conditions may have contributed to poor and inconsistent control of F. graminearum in this study.

Excess soil moisture creates an oxygen deficient growth environment that adversely affects plant growth and has led to greater agricultural losses than any other abiotic stress factor affecting the Canadian prairies, especially Manitoba. The hypoxic environment limits cellular respiration in root tissues and disrupts the antioxidative systems of plants, resulting in accumulation of reactive oxygen species which react with and damage essential cellular components. The antioxidative capacity of plants and therefore their tolerance to stress conditions such as excess moisture can be improved by treatments with growth regulators such as polyamines, which play important roles in mediating plant response to their environment. This thesis investigated the role of treatments with polyamines in improving seedling growth and enzymatic antioxidant capacity in the tissues of seedlings and young vegetative soybean plants under excess soil moisture conditions. The results indicate that treatment with polyamines can improve the growth of excess moisture-stressed seedlings and this is associated with an enhanced antioxidative response with improved expression of antioxidative genes and activity of the corresponding enzymes. Furthermore, the results of this study indicate that polyamine treatments also increase the enzymatic antioxidant capacity in the leaf tissues of young soybean plants exposed to excess moisture.

Rewardless flowering plants may bloom early to take advantage of naïve pollinators and avoid competition with rewarding species. However, at high latitudes, this strategy may be constrained by the shorter growing season. I surveyed Cypripedium candidum populations to determine if reproductive success is correlated with latitude. At 21 sites, in four regions (Iowa, southern Minnesota, northern Minnesota, and Manitoba), I assessed the composition of the co-flowering community and C. candidum’s fruiting success. At 15 sites, I surveyed the insect community and quantified orchid flower morphology. As latitude increased, so did the diversity of plants and insects, but all regions shared many common taxa. Pollinating insects at higher latitudes were often too large to pollinate C. candidum, and more appropriately-sized insects were found further south. Fruiting success was highest in Iowa and was associated with a warmer growing season, a decrease in potential co-flowering competitors and an increase in facilitators.

Rewardless flowering plants may bloom early to take advantage of naïve pollinators and avoid competition with rewarding species. However, at high latitudes, this strategy may be constrained by the shorter growing season. I surveyed Cypripedium candidum populations to determine if reproductive success is correlated with latitude. At 21 sites, in four regions (Iowa, southern Minnesota, northern Minnesota, and Manitoba), I assessed the composition of the co-flowering community and C. candidum’s fruiting success. At 15 sites, I surveyed the insect community and quantified orchid flower morphology. As latitude increased, so did the diversity of plants and insects, but all regions shared many common taxa. Pollinating insects at higher latitudes were often too large to pollinate C. candidum, and more appropriately-sized insects were found further south. Fruiting success was highest in Iowa and was associated with a warmer growing season, a decrease in potential co-flowering competitors and an increase in facilitators.

Excess soil moisture creates an oxygen deficient growth environment that adversely affects plant growth and has led to greater agricultural losses than any other abiotic stress factor affecting the Canadian prairies, especially Manitoba. The hypoxic environment limits cellular respiration in root tissues and disrupts the antioxidative systems of plants, resulting in accumulation of reactive oxygen species which react with and damage essential cellular components. The antioxidative capacity of plants and therefore their tolerance to stress conditions such as excess moisture can be improved by treatments with growth regulators such as polyamines, which play important roles in mediating plant response to their environment. This thesis investigated the role of treatments with polyamines in improving seedling growth and enzymatic antioxidant capacity in the tissues of seedlings and young vegetative soybean plants under excess soil moisture conditions. The results indicate that treatment with polyamines can improve the growth of excess moisture-stressed seedlings and this is associated with an enhanced antioxidative response with improved expression of antioxidative genes and activity of the corresponding enzymes. Furthermore, the results of this study indicate that polyamine treatments also increase the enzymatic antioxidant capacity in the leaf tissues of young soybean plants exposed to excess moisture.

Rewardless flowering plants may bloom early to take advantage of naïve pollinators and avoid competition with rewarding species. However, at high latitudes, this strategy may be constrained by the shorter growing season. I surveyed Cypripedium candidum populations to determine if reproductive success is correlated with latitude. At 21 sites, in four regions (Iowa, southern Minnesota, northern Minnesota, and Manitoba), I assessed the composition of the co-flowering community and C. candidum’s fruiting success. At 15 sites, I surveyed the insect community and quantified orchid flower morphology. As latitude increased, so did the diversity of plants and insects, but all regions shared many common taxa. Pollinating insects at higher latitudes were often too large to pollinate C. candidum, and more appropriately-sized insects were found further south. Fruiting success was highest in Iowa and was associated with a warmer growing season, a decrease in potential co-flowering competitors and an increase in facilitators.

Rewardless flowering plants may bloom early to take advantage of naïve pollinators and avoid competition with rewarding species. However, at high latitudes, this strategy may be constrained by the shorter growing season. I surveyed Cypripedium candidum populations to determine if reproductive success is correlated with latitude. At 21 sites, in four regions (Iowa, southern Minnesota, northern Minnesota, and Manitoba), I assessed the composition of the co-flowering community and C. candidum’s fruiting success. At 15 sites, I surveyed the insect community and quantified orchid flower morphology. As latitude increased, so did the diversity of plants and insects, but all regions shared many common taxa. Pollinating insects at higher latitudes were often too large to pollinate C. candidum, and more appropriately-sized insects were found further south. Fruiting success was highest in Iowa and was associated with a warmer growing season, a decrease in potential co-flowering competitors and an increase in facilitators.

Salinity is a major abiotic stress that reduces the growth and survival of most plants. In Canada, elevated levels of NaCl pose reclamation challenges for habitats disturbed by the oil sand industry. I examined the salt tolerance of Elaeagnus commutata (wolf willow), a native nitrogen fixing boreal shrub that has potential for land reclamation, by conducting greenhouse hydroponics experiments with seedlings (uninoculated or inoculated with Frankia), exposed to 0,50 and 100 mM NaCl for 12 weeks. All plants survived 100 mM NaCl, suggesting that E.commutata is a moderately salt tolerant plant. Despite reductions in performance of salt stressed seedlings, they were still able to maintain relatively high levels of physiological activities and shoot/root growth. Plant mostly maintained nutritional balance even with elevated levels of Na+ and Cl- in their tissues. However, salinity inhibited root nodule formation and severely reduced root nitrogen fixation. To confirm the suitability of E. commutata as a potential species for saline land reclamation, field studies should be conducted.

I examined the effect of Frankia spp. and ectomycorrhizal fungi on green alder (Alnus viridis ssp. crispa), growing in nutrient-poor soil and saline conditions. The first experiment involved inoculating green alder growing in low fertility soil with three species of ectomycorrhizal fungi (Lactarius torminosus, Lactarius theiogalus, Hebeloma crustuliniforme) alone or in combination, with and without Frankia spp. on. Frankia spp. inoculation significantly increased plant performance compared to non-Frankia treatments. However, nodulated plant total biomass decreased with an increasing number of fungi. The second experiment examined the effect of Hebeloma crustuliniforme and Frankia spp. on green alder exposed to 0, 50 and 100 mM NaCl. Frankia spp. inoculation showed significant increase on plant performance but Hebeloma crustuliniforme did not. Plant mass, root:shoot ratio, nodule allocation and total nitrogen fixation decreased with NaCl exposure. A decrease in root:shoot ratio caused by salt was more moderate in nodulated plants compared to non-nodulated plants.

Plant hormones and ion transporters are key elements for plant salt tolerance. To investigate the potential involvement of jasmonic acid (JA) and root ammonium transporters (AMTs) in salt tolerance, salt stress responses of tomato (Solanum lycopersicon) JA-deficient mutant def-1 (defenseless-1) and two tomato species (S. lycopersicon and S. pennellii) varying in salt tolerance were analyzed, respectively. The physiological and biochemical analyses of def-1 under salt stress showed a reduction in nitrogen (N) content and an increase in hydrogen peroxide and malondialdehyde compared to the wild type (WT) plants. The ROS (reactive oxygen species)-associated injury phenotype for def-1 was associated with lower activity of both enzymatic antioxidants and non-enzymatic antioxidants. These findings suggest that JA plays a role in maintaining N and ROS homeostasis under salt stress. The results of the bioinformatics analysis for tomato AMTs indicated that the three known genes belong to the plant AMT1 subfamily (electreogenic NH4+ transport system) and five new genes were found in the plant AMT2 subfamily (electroneutral NH3 transport system). Gene expression analysis revealed that tomato roots expressed two members of the AMT1 subfamily (involved in NH4+ uptake) and one member of the AMT2 subfamily (potentially involved in the efflux of the gaseous NH3 species). The comparative analysis between S. lycopersicon and the wild species S. pennellii under salt stress, indicated that the latter is more salt tolerant. In root tissues of both species, the expression of key genes for NO3− uptake and assimilation were reduced under salt stress. However, salt tolerance of S. pennellii was coupled with higher relative mRNA levels of NH4+ uptake genes (AMT1-type transporters, AMT1.1 and AMT1.2) and assimilation genes. These findings suggest that AMTs are involved in salt tolerance by facilitating the NH4+ uptake and reducing the energy requirements for growth. Overall, the results of my

Salinity is a major abiotic stress that reduces the growth and survival of most plants. In Canada, elevated levels of NaCl pose reclamation challenges for habitats disturbed by the oil sand industry. I examined the salt tolerance of Elaeagnus commutata (wolf willow), a native nitrogen fixing boreal shrub that has potential for land reclamation, by conducting greenhouse hydroponics experiments with seedlings (uninoculated or inoculated with Frankia), exposed to 0,50 and 100 mM NaCl for 12 weeks. All plants survived 100 mM NaCl, suggesting that E.commutata is a moderately salt tolerant plant. Despite reductions in performance of salt stressed seedlings, they were still able to maintain relatively high levels of physiological activities and shoot/root growth. Plant mostly maintained nutritional balance even with elevated levels of Na+ and Cl- in their tissues. However, salinity inhibited root nodule formation and severely reduced root nitrogen fixation. To confirm the suitability of E. commutata as a potential species for saline land reclamation, field studies should be conducted.

Plant hormones and ion transporters are key elements for plant salt tolerance. To investigate the potential involvement of jasmonic acid (JA) and root ammonium transporters (AMTs) in salt tolerance, salt stress responses of tomato (Solanum lycopersicon) JA-deficient mutant def-1 (defenseless-1) and two tomato species (S. lycopersicon and S. pennellii) varying in salt tolerance were analyzed, respectively. The physiological and biochemical analyses of def-1 under salt stress showed a reduction in nitrogen (N) content and an increase in hydrogen peroxide and malondialdehyde compared to the wild type (WT) plants. The ROS (reactive oxygen species)-associated injury phenotype for def-1 was associated with lower activity of both enzymatic antioxidants and non-enzymatic antioxidants. These findings suggest that JA plays a role in maintaining N and ROS homeostasis under salt stress. The results of the bioinformatics analysis for tomato AMTs indicated that the three known genes belong to the plant AMT1 subfamily (electreogenic NH4+ transport system) and five new genes were found in the plant AMT2 subfamily (electroneutral NH3 transport system). Gene expression analysis revealed that tomato roots expressed two members of the AMT1 subfamily (involved in NH4+ uptake) and one member of the AMT2 subfamily (potentially involved in the efflux of the gaseous NH3 species). The comparative analysis between S. lycopersicon and the wild species S. pennellii under salt stress, indicated that the latter is more salt tolerant. In root tissues of both species, the expression of key genes for NO3− uptake and assimilation were reduced under salt stress. However, salt tolerance of S. pennellii was coupled with higher relative mRNA levels of NH4+ uptake genes (AMT1-type transporters, AMT1.1 and AMT1.2) and assimilation genes. These findings suggest that AMTs are involved in salt tolerance by facilitating the NH4+ uptake and reducing the energy requirements for growth. Overall, the results of my

Reclamation success is highly dependent upon final soil quality of stockpiled soils, such as those found Cold Lake Oil Sands Region. Stockpiled soils, however, are generally poor in quality. Soils were amended with, biochar (BC), humalite (HU), a sub-bituminous coal; and peat (PT), as well as 50:50 blends of biochar:humalite (BCH) and biochar:peat (BCP). These amendments were applied at rates of 0, 6.55, 13.1 and 26.2 g C kg-1 each. Biochar, PT, and BCP applied at the rate of 26.2 g C kg-1 were found to reduce N2O emissions by 34, 54, and 70%, respectively, relative to the control. Within the bioassay, BC and PT amendment resulted in a 38 and 40% increase in dry matter yield (DMY) respectively. Finally, amendment typically resulted in significant net decreases in Olsen P values, while nitrate and ammonium concentrations were high in PT amended soils. In general, PT had the best overall performance.

Plant development is tightly linked to the environment. Environmental signals interact with endogenous hormonal cues, allowing plants to optimize their response to external stress. The plant hormone abscisic acid (ABA) is involved in a variety of stress tolerance mechanisms. These pathways have been widely studied in the model plant Arabidopsis thaliana. In this thesis I investigate the effect of light, ABA, and ABA mediated salt and osmotic stress on Arabidopsis seed germination, examining the role of light signaling component DE-ETIOLATED 1 (DET1) in these mechanisms. DET1 is a negative regulator of the light response promoting transcription factor ELONGATED HYPOCOTYL 5 (HY5). Thus, det1 mutants resemble light grown plants when grown in complete darkness. In this study, det1 mutants showed a variety of different germination phenotypes on control, ABA, and salt/osmotic stress conditions. Germination of det1 was sensitive to ABA but resistant to salt and osmotic stress. det1 ABA sensitive germination appeared to be due to an upregulation of a germination inhibiting transcription factor ABSCISIC ACID INSENSITIVE 5 (ABI5) by HY5. On the other hand, we propose that in salt/osmotic stress conditions, HY5 downregulates another transcription factor, ABSCISIC ACID BINDING FACTOR 3 (ABF3) which inhibits seed germination, thus det1 mutants exhibited resistant germination. In addition, DET1 exhibits genetic interactions with genes in the ABA signalling pathway during development. Both hy5 and abf1 mutants suppressed det1 phenotypes not only during vegetative development but also during germination, suggesting that a pathway whereby DET1 negatively regulates HY5, and HY5 positively regulates ABF1. Moreover components of distinct CULLIN4 DAMAGED DNA BINDING PROTEIN 1 (CUL4-DDB1) E3 ligase complexes both suppressed and enhanced det1 phenotypes. Finally, the det1 rapid water loss phenotype was independent of all genes considered except for ABF1. In conclusion, my PhD research sho

Reclamation success is highly dependent upon final soil quality of stockpiled soils, such as those found Cold Lake Oil Sands Region. Stockpiled soils, however, are generally poor in quality. Soils were amended with, biochar (BC), humalite (HU), a sub-bituminous coal; and peat (PT), as well as 50:50 blends of biochar:humalite (BCH) and biochar:peat (BCP). These amendments were applied at rates of 0, 6.55, 13.1 and 26.2 g C kg-1 each. Biochar, PT, and BCP applied at the rate of 26.2 g C kg-1 were found to reduce N2O emissions by 34, 54, and 70%, respectively, relative to the control. Within the bioassay, BC and PT amendment resulted in a 38 and 40% increase in dry matter yield (DMY) respectively. Finally, amendment typically resulted in significant net decreases in Olsen P values, while nitrate and ammonium concentrations were high in PT amended soils. In general, PT had the best overall performance.

Preharvest sprouting (PHS), the germination of seeds on the maternal plant before harvest, is a big challenge for barley producers worldwide. It is attributed mainly to low seed dormancy. The balance between two classical plant hormones, gibberellin (GA) and abscisic acid (ABA) regulates seed dormancy and germination, and the endogenous level of these two hormones in plants is determined by their biosynthesis and catabolism. This thesis characterized the expression patterns of the major GA and ABA metabolism genes in barley cv. Betzes during seed development, and germination in both dormant and non-dormant seeds. The results indicate that specific gene family members of the two hormones play distinct temporal roles in regulating seed development, dormancy onset and release, and germination. Since only two genes encoding the GA deactivating GA 2-oxidase enzyme have been known so far in barley, this study also identified two new GA2ox genes designated as HvGA2ox1 and HvGA2ox3.

Revegetation is employed to mitigate the spread of mine tailings in the environment by ameliorating tailings with organics to promote plant cover. Revegetation has proven to be successful in establishing plant cover, but the long-term effects are largely unknown. A field study was conducted to evaluate the success of four artificially revegetated tailings from Manitoba by comparing plant cover and diversity. Central Manitoba, Flin Flon, and Thompson had moderate cover while cover was low in Lynn Lake. All four sites had low diversity and were composed of early-successional species. The results suggest that while current revegetation methods promote plant growth on tailings, it is currently difficult to determine if and how the vegetation will progress from a grass-legume community to a boreal forest. In addition, while various amounts of effort were invested into each site, the results indicate the degree of remediation does not affect overall success.