Kabuli chickpea (<i>Cicer arietinum</i> L.) has two leaf types, the fern and unifoliate. Yield potential is limited for kabuli chickpea in Saskatchewan. It is limited by a short-season, a semi-arid environment, and end-of-season rainfall. Manipulating plant population, and choosing chickpea cultivars with the best leaf type for biomass production, radiation interception and yield for the early, middle, or late growth season, may increase chickpea yield. Therefore, the objectives of this study were: to (i) determine the relationship between leaf type and key growth parameters of six chickpea cultivars varying in leaf morphology at moderate and high plant population densities; (іі) to characterize the reaction of the fern and unifoliate leaf to altered canopy light environments. Different light environments were created by 50% defoliation at vegetative growth, first flower, and 50% shading from vegetative growth to first flower, as well as two light enrichment treatments initiated at the first flower and pod formation stages.<p> Fern leaf cultivars exhibited higher maximum light interception, seasonal cumulative intercepted radiation and a higher harvest index compared to unifoliate leaf cultivars. However, both leaf type canopies had less than 95% light interception for most of the season. The fern and unifoliate leaf type contributed to similar radiation use efficiency in three out of four location-years. In addition, fern leaf cultivars produced significantly higher seed yield than cultivars with unifoliate leaves.<p>Plant density influenced growth parameters. For example, the 45 plants m-2 treatment had a higher harvest index than the 85 plants m-2 treatment, in two location-years, while both population treatments were similar in the other two location-years. Yield of chickpea was increased by higher plant population in only one location-year, but was not significantly affected by plant population in the other location-years. The effect of canopy light environment manipulation on chickpea yield depended on the stages of plant development when they were applied. Defoliation at vegetative growth and first flower had no effect on yield. However, plants responded significantly to the 50% shade treatment; the crop growth rate, harvest index and yield were less in the shaded treatment compared to the control. Shading also increased plant height. Light enrichment treatments increased the yield. However, the degree of yield increase was greater when light enrichment occurred at first flower, than at the later stage of pod formation. These results highlighted the importance of the amount of irradiance during the flowering stage. It was concluded that chickpea breeders should select lines with fern leaves for improved radiation interception when breeding cultivars for semiarid short-season environments such as in Saskatchewan. Management and breeding practices should ensure that the crop can make efficient use of the solar radiation at flowering to maximize yield. Improvement at the canopy and subsequent yield level is yet to be made in Saskatchewan environments by increased light interception, increased growth before flowering, and increased and stable harvest index.

How patterns arise from an apparently uniform group of cells is one of the classical problems in developmental biology. The mechanism is complicated by the fact that patterning occurs on a growing medium. Therefore, changes in an organism’s size and shape affect the patterning processes. In turn, patterning itself may affect growth. This interaction between growth and patterning leads to the generation of complex shapes and structures from simpler ones. Studying such interactions requires the possibility to monitor both processes in vivo. To this end, we developed a new technique to monitor and quantify vein patterning in a growing leaf over time using the leaves of Arabidopsis thaliana as a model system. We used a transgenic line with fluorescent markers associated with the venation. Individual leaves are followed in many samples in vivo through time-lapse imaging. Custom-made software allowed us to extract the leaf surface and vein pattern from images of each leaf at each time point. Then average spatial maps from multiple samples that were generated revealed spatio-temporal gradients. Our quantitative description of wild type vein patterns during leaf development revealed that there is no constant size at which a part of tissue enclosed by vasculature will become irrigated by a new vein. Instead, it seemed that vein formation depends on the growth rate of the tissue. This is the first time that vein patterning in growing leaves was quantified. The techniques developed will later be used to explore the interaction between growth and patterning through a variety of approaches, including mutant analysis, pharmacological treatments and variation of environmental conditions.

Fiber optic sensors are designed to measure various parameters. The distributed fiber optics sensor has been a very promising candidate for the structural health monitoring. In this thesis, we characterized LEAF (Large Effective Area Fiber) fiber’s Brillouin scattering spectrum and investigated its potentiality for the distributed Brillouin temperature and strain sensor. Optical fibers with complex refractive index profiles are applied to improve the Brillouin threshold by varying the Brillouin linewidth. As LEAF fiber has a modified refractive index profile, we investigated its Brillouin linewidth’s dependence on the square of the pump light’s frequency. We verified the Brillouin frequency’s variation with input SOP experimentally for LEAF fiber in the spontaneous regime. This sets a limitation for the frequency resolution of distributed Brillouin sensors. We also realized a simultaneous temperature and strain sensor with LEAF fiber applying the Brillouin optical time domain analysis. Based on the direct detection of LEAF beat frequencies, a simultaneous strain and temperature sensor was demonstrated.

This research evaluates the decomposition of leaf litter while in litter traps. More specifically this study asks, ‘Does sugar maple (Acer saccharum Marsh.), American basswood (Tilia Americana L.) and American beech (Fagus grandifolia Ehrh.) leaf litter collected bi-weekly from litter traps undergo a loss of dry mass and nutrient content (C, N, P, K, Ca and Mg) in comparison to freshly abscised leaf litter?’The objective of the initial experiment was to determine if sugar maple, basswood and beech leaf litter collecting in litter traps, while exposed to in-situ conditions, experienced decomposition. Results indicated that sugar maple, basswood and beech leaf litter experienced early stages of decomposition and identified precipitation, freezing temperatures and microbial activity as possible mechanisms for the observed decomposition. It was found that the dry weight of sugar maple and basswood differed significantly (p < 0.05 and p < 0.10, respectively) post- 14-day experiment period as compared to the initial dry weight. Consequently, three experiments were completed to examine the aforementioned variables. Conclusions were based on measured changes in the mass and nutrient (C, N, P, K, Ca and Mg) content of freshly abscised sugar maple, basswood and beech leaf litter under ex-situ conditions. It was found that the dry weight sugar maple and basswood leaf litter exposed to 30 mm, 60 mm and 100 mm of precipitation differed significantly (p < 0.05) as compared to freshly abscised leaf litter. In general, this research affirmed that precipitation and freezing temperature contribute to a change in mass and nutrient content of leaf litter collecting in litter traps. Furthermore, through measurable production of CO2 and Community Level Physiological Profiling it was determined that microbes are present and active on the leaf surface and contribute to the decomposition of leaf litter in litter traps.

This research evaluates the decomposition of leaf litter while in litter traps. More specifically this study asks, ‘Does sugar maple (Acer saccharum Marsh.), American basswood (Tilia Americana L.) and American beech (Fagus grandifolia Ehrh.) leaf litter collected bi-weekly from litter traps undergo a loss of dry mass and nutrient content (C, N, P, K, Ca and Mg) in comparison to freshly abscised leaf litter?’The objective of the initial experiment was to determine if sugar maple, basswood and beech leaf litter collecting in litter traps, while exposed to in-situ conditions, experienced decomposition. Results indicated that sugar maple, basswood and beech leaf litter experienced early stages of decomposition and identified precipitation, freezing temperatures and microbial activity as possible mechanisms for the observed decomposition. It was found that the dry weight of sugar maple and basswood differed significantly (p < 0.05 and p < 0.10, respectively) post- 14-day experiment period as compared to the initial dry weight. Consequently, three experiments were completed to examine the aforementioned variables. Conclusions were based on measured changes in the mass and nutrient (C, N, P, K, Ca and Mg) content of freshly abscised sugar maple, basswood and beech leaf litter under ex-situ conditions. It was found that the dry weight sugar maple and basswood leaf litter exposed to 30 mm, 60 mm and 100 mm of precipitation differed significantly (p < 0.05) as compared to freshly abscised leaf litter. In general, this research affirmed that precipitation and freezing temperature contribute to a change in mass and nutrient content of leaf litter collecting in litter traps. Furthermore, through measurable production of CO2 and Community Level Physiological Profiling it was determined that microbes are present and active on the leaf surface and contribute to the decomposition of leaf litter in litter traps.

Kabuli chickpea (<i>Cicer arietinum</i> L.) has two leaf types, the fern and unifoliate. Yield potential is limited for kabuli chickpea in Saskatchewan. It is limited by a short-season, a semi-arid environment, and end-of-season rainfall. Manipulating plant population, and choosing chickpea cultivars with the best leaf type for biomass production, radiation interception and yield for the early, middle, or late growth season, may increase chickpea yield. Therefore, the objectives of this study were: to (i) determine the relationship between leaf type and key growth parameters of six chickpea cultivars varying in leaf morphology at moderate and high plant population densities; (іі) to characterize the reaction of the fern and unifoliate leaf to altered canopy light environments. Different light environments were created by 50% defoliation at vegetative growth, first flower, and 50% shading from vegetative growth to first flower, as well as two light enrichment treatments initiated at the first flower and pod formation stages.<p> Fern leaf cultivars exhibited higher maximum light interception, seasonal cumulative intercepted radiation and a higher harvest index compared to unifoliate leaf cultivars. However, both leaf type canopies had less than 95% light interception for most of the season. The fern and unifoliate leaf type contributed to similar radiation use efficiency in three out of four location-years. In addition, fern leaf cultivars produced significantly higher seed yield than cultivars with unifoliate leaves.<p>Plant density influenced growth parameters. For example, the 45 plants m-2 treatment had a higher harvest index than the 85 plants m-2 treatment, in two location-years, while both population treatments were similar in the other two location-years. Yield of chickpea was increased by higher plant population in only one location-year, but was not significantly affected by plant population in the other location-years. The effect of canopy light environment manipulation on chickpea yield depended on the stages of plant development when they were applied. Defoliation at vegetative growth and first flower had no effect on yield. However, plants responded significantly to the 50% shade treatment; the crop growth rate, harvest index and yield were less in the shaded treatment compared to the control. Shading also increased plant height. Light enrichment treatments increased the yield. However, the degree of yield increase was greater when light enrichment occurred at first flower, than at the later stage of pod formation. These results highlighted the importance of the amount of irradiance during the flowering stage. It was concluded that chickpea breeders should select lines with fern leaves for improved radiation interception when breeding cultivars for semiarid short-season environments such as in Saskatchewan. Management and breeding practices should ensure that the crop can make efficient use of the solar radiation at flowering to maximize yield. Improvement at the canopy and subsequent yield level is yet to be made in Saskatchewan environments by increased light interception, increased growth before flowering, and increased and stable harvest index.

The fungus <i>Colletotrichum truncatum</i> (Schw.) Andrus and Moore causes lentil anthracnose, which is a major challenge to lentil production in Western Canada. The pathogen infects leaves and stems, resulting in defoliation, stem girdling, plant wilting, and possibly plant death. Two races, Ct0 and Ct1, have been identified in the pathogen population in Canada. However, the differences in the infection process between the two races have not been described in detail. Currently, several lentil cultivars, such as CDC Redberry, CDC Robin, CDC Rosetown, CDC Rouleau, and CDC Viceroy, have resistance against race Ct1, whereas there are no cultivars showing resistance to race Ct0. The objective of this study was to investigate differences in the infection process between race Ct0 and race Ct1 using the fully susceptible cultivar Eston and the race Ct1-resistant cultivar CDC Robin. Experiments on glass well slides showed that race Ct0 had no inherently different conidium germination rate compared to race Ct1, and that differences in conidium germination between the two races on lentil plants were the result of specific interactions between the two races and lentil resistance. Investigations of the infection process of the two races on detached and attached leaves of both lentil cultivars were conducted starting 12 h postinoculation (hpi) until 72 hpi, including conidium germination, appressorium formation, and leaf penetration. Results indicated that differences in virulence of the two races may be related to the ability of conidia to germinate and form appressoria, as well as the ability of primary infection hyphae to grow in response to cues from the lentil cultivars. Furthermore, resistance of lentil to isolates of race Ct1 appeared to involve an inhibition in and/or delay of the spread of primary infection hyphae inside the plant tissue. Results of infection studies of one isolate from each race on attached leaves did not completely agree with results of the same isolates on detached leaves. Based on this study, race Ct0 and race Ct1 do not appear to be classical physiological races, but may represent aggressive races or some intermediate forms.

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

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

Ethylene has long been considered as the main plant growth regulator that plays a key role in the regulation of leaf senescence. In sweet potato, ethephon, an ethylene releasing compound, promoted leaf senescence and H2O2 elevation. These ethephon-mediated effects were alleviated or attenuated by exogenous reduced glutathione and ascorbic acid. Ethephon treatment gradually increased endogenous total and reduced glutathione and ascorbic acid levels in sweet potato detached leaves 3 days after treatment. The H2O2 amount, however, was also increased at 72 h after treatment. Sweet potato detached leaves pretreated with reduced glutathione did significantly increased endogenous total and reduced glutathione levels at 24 h and remarkably decreased H2O2 amount at 72 h after ethephon application compared to that of ethephon alone control. Ethephon caused quick elevation of a small H2O2 peak at about 4 h after application, and the enhancement was eliminated by reduced glutathione pretreatment in treated sweet potato leaves. Pretreatment of diphenylene iodonium (DPI), an NADPH oxidase inhibitor, also repressed leaf senescence and H2O2 elevation at day 3 after ethephon treatment in sweet potato detached leaves, and the attenuation was effective within the first 4 h after ethephon treatment. For senescence-associated gene expression, ethephon and L-buthionine sulfoximine (BSO), an endogenous glutathione synthase inhibitor, did induced asparaginyl endopeptidase (SPAE) and cysteine proteases (SPCP1, SPCP2 and SPCP3) gene expression and the activation was repressed by reduced glutathione pretreatment. Based on these data we conclude that ethephon treatment may cause quick elevation of a small H2O2 peak likely via the NADPH oxidase, which may function as a signal component leading to leaf senescence, H2O2 elevation and senescence-associated gene expression in sweet potato detached leaves. The rate of endogenous antioxidant such as reduced glutathione elevation is also important and affects leaf senescence, H2O2 elevation and senescence-associated gene expression in sweet potato leaves.