Advances in chemical and bio-technology have helped boost modern agriculture with increased food productivity and consequently, impacted the environment leading to more saline and drought prone arable lands. Mandate of world food security heavily depends on crop improvement and developing strategies to increase abiotic stress tolerance. The use of rhizobacteria and their excreted compounds is a contextually safe and viable option. Lipo-chito-oligosaccharide (LCO) from Bradyrhizobium japonicum 532C and Thuricin 17 (Th17) from Bacillus thuringiensis NEB17 are bacterial signal compounds promoting plant growth in legumes and non-legumes. The effect of these compounds at proteome level under unstressed and salt stressed conditions on Arabidopsis thaliana was studied using root drench method. The phytohormones in Arabidopsis thaliana rosettes were differential expressed at 24 h treatment. At the proteome level, > 2-fold changes in the activation of the carbon and energy metabolism pathway proteins in both LCO and Th17 were observed in comparison to control. At 250 mM NaCl stress, the control plants under osmotic-shock shut down most of the carbon-metabolism and up-regulated the energy-metabolism and antioxidant pathways, while the LCO and Th17 with salt stress retained some of the Light harvesting complex, Photosystem I and II proteins along with the up-regulation of energy and antioxidant pathways suggesting that the rosettes were able to amend the salt stress better when treated with LCO and Th17.Soybean (Absolute RR) germination for salt tolerance suggested that LCO and Th17 helped seeds germinate the best at 100 mM NaCl. The proteome suggested efficient and speedier partitioning of storage proteins, up-regulation of carbon, nitrogen and energy metabolisms in LCO and Th17 seeds in comparison with controls both under optimal and salt stress. These findings suggest that the Arabidopsis rosettes and the soybean germinating seeds alter their proteome based on bacterial signals and on stress. The specificity of this response plays a crucial role in the plants life cycle, and understanding this response is of importance in commercial application. / Les progrès de la chimie et de la biotechnologie ont contribué à stimuler l'agriculture moderne et la productivité accrue de nourriture. La conséquence en est l'impact sur l'environnement rendant les terres arables plus sujettes à la salinité et à la sécheresse. La sécurité alimentaire mondiale dépend fortement de l'amélioration des cultures et du développement de stratégies visant à accroître la tolérance aux stress abiotiques. L'utilisation de rhizobactéries et de leurs composés excrétés est dans ce contexte une option sécuritaire et viable.Le lipo-chito-oligosaccharide (LCO) du Bradyrhizobium japonicum 532C et le Thuricin 17 (Th17) du Bacillus thuringiensis NEB17 sont des composés de signaux de bactéries favorisant la croissance des plantes dans les légumineuses et les non-légumineuses. L'effet de ces composés au niveau du protéome d'Arabidopsis thaliana, sans stress et avec le stress du sel, a été étudié en utilisant la méthode par trempage de racine. Les phyto-hormones dans les rosettes d'Arabidopsis thaliana ont été exprimées de manière différentielle lors du traitement de 24h. Au niveau du protéome, des changements 2 fois supérieurs en comparaison au témoin ont été observés dans l'activation des protéines de la voie métabolique énergétique du carbone, pour LCO et pour Th17. Sous un stress produit par 250 mM de NaCl, les plants témoins sous choc osmotique ont diminué la plupart du métabolisme du carbone, et régulé à la hausse les voies du métabolisme énergétique et antioxydant ; tandis que LCO et Th17 sous stress salin ont conservé une partie du complexe de capture de la lumière, les protéines de Photosystem I et II, et régulé positivement les voies énergétiques et antioxydants. Cela suggère que les rosettes furent en mesure de modifier positivement le stress salin lorsque traitées avec LCO et Th17.La germination des graines de soja (Absolute RR) pour la tolérance au sel, a montré que LCO et Th17 aident les graines à germer de manière optimale avec 100 mM de NaCl. Pour les graines avec LCO et Th17 et par rapport aux témoins à la fois sous stress optimal et salin, le protéome suggère: une séparation des protéines de stockage éfficace et plus rapide, et la régulation à la hausse des métabolismes du carbone, de l'azote et énergétiques.Ces résultats démontrent que les rosettes d'Arabidopsis et les graines de soja en germination modifient leur protéome selon les signaux bactériens et le stress. La spécificité de cette réponse joue un rôle crucial dans le cycle de vie des plantes, et la compréhension de cette réponse est d'importance dans son application commerciale.

Protoplasts and spontaneous fusion bodies can be isolated from a number of tissues, by treating the tissues with a mixture of macerating and cellulolytic enzymes. The shape of the spontaneous fusion bodies frequently reflects the parental tissue structure. An electron microscopic study of the treatment of the oat root tip and tobacco leaf with enzymes, reveals that spontaneous fusion is brought about by the expansion of plasmodesmatal connexions within the tissue. Specific treatments befo3B and during enzyme treatment can affect the level of spontaneous fusion. The culture of spontaneous fusion bodies in solid media is less successful than in liquid media, where cytoplasmic reorganization, wall regeneration and division occur. The pattern of division is irregular and may not be mitotic. The level of multinucleation in cultures declines with time. Whilst some spontaneous fusion bodies decline and others may subdivide, microdensitometric evidence suggests that nuclear fusion or close aggregation may be occurring. There is, however, no microscopic evidence for nuclear fusion. The fusion of originally separate, uninucleate protoplasts can be induced by treatment with sodium nitrate. Membrane adhesion and fusion are followed by organelle redistribution and vacuolar fusion. No interspecific fusion bodies are formed and the intraspecific fusion products demonstrate a low viability. Other salts induce protoplast adhesion and abnormal plasmalemmar activity but not fusion. Similarly, Concanavalin A and lysozyme induce strong adhesion but no fusion. Treatment of protoplasts with Sendai virus can induce adhesion and eventual lysis, with membrane fusion as a likely intervening stage. Lysolecithin induces a similar reaction. It is possible that such reactions could be controlled to successfully induce protoplast fusion.

During the field seasons 1993 and 1994, five-year-old field-grown ash trees as well as potted two-year-old saplings and one-year-old seedlings of ash (Fraxinu. g exccl. 5ior L. ) were exposed to ozone episodes in open-top chambers. The plants received either charcoal-filtered air (CF) or charcoal-filtered air to which 150 ppb of ozone were added (CF+03). Plants in unchambered plots, receiving ambient air (Ambient), were included into the investigation for comparison. Half of the two-year-old saplings of each of the three pollution treatments were subjected to three drought cycles of 7-14 days, while the rest of the plants were well watered as a control. The two-year-old saplings were the main object of the investigation. On these, the main parameters investigated were: stomatal conductance; the growth parameters - extension growth, radial increment at the stembase and radial increment at the base of the new shoot; leaf area; aboveground biomass production; the microscopic determination of ringwidth; and the structure of the latest annual ring for samples taken from the stembase. Additionally, stomatal conductance was measured in the five-year-old trees and total biomass accumulation, photosynthate allocation and ring parameters of the latest annual ring were investigated in the one-year-old seedlings. The ozone episodes were shown to influence stomatal conductance in plants of different water status differently. Drought stress led to a significant decrease of stomatal conductances, and the drought-ozone interaction caused a further decrease which was also significant. The ozone episodes also affected stomatal responsiveness of the plants, restricting stomatal aperture of the droughted two-year-old saplings, when the drought cycles were finished and the plants were maintained at high soil moisture again. The drought cycles alone, however, left the functioning of the stomata unimpaired. The restriction of stomatal aperture which was found for the droughted CF+03 treatment caused reductions of growth and biomass accumulation, but a significant decrease was found only for radial growth at the stembase of those plants. Analysis of the annual rings showed that this was caused by a reduction of xylem growth, while phloem development did not seem to be affected. Radial increment at the base of the new shoot was less affected by the pollution treatment. Here only a significant impact of the drought could be found, and the growth reduction was less pronounced. In the well-watered plants, ozone caused a slight increase in stomatal conductance which led to increased aboveground biomass accumulation, but concomitantly biomass allocation was slightly altered, favouring the crown rather than the lower plant organs. A reduction of photosynthate allocation to the roots became evident from measurements on the one-year-old saplings. Due to chamber effects, stomatal conductance as well as growth, biomass accumulation and allocation differed from those of plants from the Ambient treatment. The responses to ozone that were found in this study could lead to increased crown growth during periods of good water availability and to a strong reduction of water uptake during and following drought conditions. Thus crown demand for water may increase in ash trees exposed to elevated ozone concentrations, while the supply of water to the crown may become limiting.

The spectral composition of natural daylight was examined using horizontal planar receptor surfaces. During the day, incident spectra were remarkably uniform. Particular attention was paid to physiologically important variables. The mean 660:730 nm photon fluence ratio (R:FR) was 1.15, corresponding to a phytochrome photoequilibrium of 0.53, but in late winter R:FR was lower than in late summer (ca. 1.0 and 1.25 respectively). The mean blue:red ratio (0.86) was strongly affected by cloud cover. The light environment of shade habitats was also examined. Under cloudy conditions in an oak woodland, R:FR fell to ca. 0.55 during the leafy phase, but higher values (ca. 0.8) were recorded in late summer as a result of the seasonal trend in incident R:FR. Reflectance and transmittance spectra and pigment content of the leaves and the transmittance of the canopy were measured. Beneath a dense sugar beet canopy, R:FR was well-correlated with canopy transmittance and fell to very low levels (ca. 0.06). However, even this would not sustain a classical "high irradiance response", so it is unlikely to be important under natural conditions. In all three habitats, R:FR was lower and the blue:red ratio higher during twilight than during the day, but the latter was much less affected by the canopies. However, fluence rate was much more reliable as potential source of photoperiodic time signals. The involvement of phytochrome amd other receptors is discussed. Leaf and stomatal morphogenesis in Chenopodium album L. was studied using a high irradiance growth cabinet. Reduced fluence rates of white or blue light produced larger leaves but had no effect on stomatal index (SI) while supplemntary far-red reduced SI but had no effect on leaf area. Thus. both factors affect stomatal density. However no differences in gas exchange characteristics were detected. A flexible computer graphics program for data plotting is also described.

Nitrogen (N) and the levels of N in plants play a vital role in the physiology, regulating their development and metabolism. We grew Arabidopsis thaliana under agronomic conditions at low (6 mg N/L) and high (106 mg N/L) N fertilizer regimes, maintaining a constant NO3-N to NH4-N ratio (3:1). Using a shotgun mass spectrometry proteomics approach, multi-dimensional protein identification technology (MudPIT), we characterized a total of 2134 reproducibly identified proteins shared between the two N treatments. By statistical analysis in both treatments we found 37 differentially expressed proteins that satisfied both the AC test and the FDR q-value specified cutoffs, where 18 proteins were down regulated and 19 proteins were up regulated under low and high N treatments. We also found 35 differentially expressed proteins that are statistically important but did not satisfy the q- test. These differentially expressed proteins appear to have roles in glycolysis, metabolic, developmental, and signaling processes, or protein binding, transport and nucleic acid binding. The proteins associated with glycolysis indicate glutamine metabolism is of major importance in the plant N economy since it provides N to young developing tissues. Our study indicates that under varying N level treatments, proteins responsible for glutamate synthase (GOGAT), glutamine synthase (GS), and dehydrogenase activity (DH) that serve as enzymes to catalyze a link between carbohydrate and amino acid metabolism are up regulated. Thus, this study has enabled us to apply comparative shotgun proteomics to characterize A. thaliana at the proteomic level and will provide the tools necessary to provide an improved understanding of how and what up-regulates and down regulates different proteins under varying environmental conditions. / La fertilisation en azote (N) et la teneur en N des plantes ont un rôle clef dans leur physiologie, régulant leur développement et métabolisme. Tout en gardant un rapport de NO3-N à NH4-N de 3:1, des plants d'Arabidopsis thaliana (L.) Heynh furent cultivés sous deux régimes de fertilisation: bas (6 mg N/L) et élevé (106 mg N/L). Utilisant une technique protéomique en vrac par spectrométrie de masse et une technologie d'identification multidimensionnelle des protéines (MudPIT), nous avons pu caractériser un total de 2134 protéines identifiées de façon récurrente comme apparaissant dans les deux traitements de fertilisation azotée. Une analyse statistique des deux traitements a indiqué la présence de 37 protéines différentiellement exprimées, satisfaisant à la fois le test Audic-Claverie (AC) et le seuil de valeur q dans l'estimation du taux d'erreur (FDR). De celles-ci, 18 protéines furent régulées à la baisse lors des traitements à haut ou bas niveau de N, et 19 furent régulées à la hausse dans les mêmes circonstances. En plus, 35 protéines différentiellement exprimées du point de vue statistique ne passèrent tout de même pas le test de la valeur q. Les protéines différentiellement exprimées semblent avoir des rôles dans les processus de glycolyse, de métabolisme, de développement, de signalisation, et de transport, ainsi que dans la liaison des protéines et des acides nucléiques. Une analyse des protéines associées à la glycolyse indique que le métabolisme de la glutamine est d'une importance majeur dans l'économie en N de la plante, puisqu'il fournit l'azote aux jeunes tissus en voie de développement. Notre étude indique que, sous différents niveaux de fertilisation en N, les protéines responsables pour l'activité glutamate synthétase (GOGAT), glutamine synthétase (GS), et déshydrogénase (DH), servant comme enzymes dans la catalyse du lien entre les voies de métabolisme des glucides et celui des acides aminés, sont régulés à la hausse. Ainsi, cette étude nous permettra d'utiliser une technique protéomique en vrac comparative afin de caractériser A. thaliana au niveau protéomique, et nous fournira les outils nécessaires à mieux comprendre quelles protéines sont régulées à la hausse ou à la baisse sous différentes conditions environnementales et comment cette régulation est mise en œuvre.

This thesis involved an investigation of potato (Solanum tuberosum L.) tuber antioxidant capacity, particularly the phytonutrients vitamin C and polyphenolics. Tubers of 12 Canadian-grown and 5 foreign cultivars were screened for antioxidants qualitatively and quantitatively following 1 and 7 months of storage (5±1 oC). Significant differences were seen in quality and quantity of tuber antioxidants (including vitamin C and polyphenolics) between cultivars, storage intervals, and tuber tissues (skin, cortex, and pith). A potato microtuber model system was developed to test the effects of hormesis on microtuber antioxidant capacity. Hydrogen peroxide sprays (2 and 4 mM) increased the antioxidant capacity of microtubers in 2 cultivars by 12-26 %, showing the potato microtuber model system to be sensitive and useful for manipulating phytonutrient composition via hormetic treatments. Information in this thesis may have future applications for better cultivar selection and cultivation practices for improved phytonutrient content of field-grown potato tubers. / La capacité antioxydante des tubercules de pomme de terre (Solanum tuberosum L.), particulièrement celle conférée par la vitamine C et les polyphénoliques, fit l'objet de cette étude. La teneur et la gamme des antioxydants présents dans les tubercules de 12 cultivars de pomme de terre sélectionnés au Canadiens et 5 cultivars sélectionnés à l'étranger, ont été.evalués après 1 ou 7 mois d'entreposage à 5±1oC. Le cultivar, la durée d'entreposage, et le tissu échantillonné (peau, chair, ou moelle) eurent tous un effet significatif sur la teneur et la gamme des antioxydants (vitamine C et les polyphénoliques) présents. Un système modèle avec microtubercules servit à l'examen d'effets d'hormèse sur la teneur en antioxydants des microtubercules de deux cultivars. Une aspersion au péroxide (2 ou 4 mM) augmenta de 12% à 26% la capacité antioxydante de microtubercules de deux cultivars différents, indiquant que ce système modèle est sensible et se prête bien à la manipulation du contenu nutritif des tubercules par traitements hormetiques. Ces connaissances pourraient s'avérer utile dans la sélection de cultivars et la mise en oeuvre de pratiques culturales pouvant améliorer, au champ, le contenu nutritif des pommes de terre.

No description available.

'Honeycrisp', a new apple cultivar, has high susceptibility to physiological disorders, including soft scald (SS) and soggy breakdown (SB). An important factor inducing these disorders is cool weather conditions at the end of the growing season. 'Honeycrisp' apples were harvested in Ontario (three sites), Québec (two sites) and in Nova Scotia (one site), in 2009 and 2010, in addition to data from Ontario (four sites), from 2002 to 2006. Analyses were made to link fruit quality to the weather at each site. A combination of dry conditions (for phenological stages BBCH 71-75), and cool conditions (BBCH 65-71 and 77.5-80) increased SS susceptibility. A combination of cool and wet conditions (BBCH 77.5-80) increased SB susceptibility. Models were developed for SS (RMSE = 18.71) and SB (RMSE = 6.88) predictions. Producers could use these in establishing more appropriate management of fresh fruit loads depending on regional and seasonal susceptibility to these disorders. / 'Honeycrisp', une nouvelle variété de pommes, est susceptible à l'échaudure molle (ÉM) et au brunissement interne (BI). Des conditions froides à la fin du développement des pommes induiraient leur développement. Des 'Honeycrisp' ont été récoltées en Ontario (trois sites), au Québec (deux sites) et en Nouvelle-Écosse (un site), en 2009 et 2010, avec l'ajout de données de l'Ontario (quatre site) entre 2002 et 2006. Des analyses ont été faites pour lier la qualité des pommes aux conditions météorologiques. Une combinaison de conditions sèches (aux stades phénologiques BBCH 71-75) et de températures froides (BBCH 65-71 et 77.5-80) augmenterait l'incidence d'ÉM, alors que des conditions froides et de fortes précipitations (BBCH 77.5-80) intensifierait le BI. Deux modèles de prédiction ont été développés pour l'ÉM (RMSE = 18.71) et le BI (RMSE = 6.88). Ceux-ci peuvent servir d'outils aidant les producteurs à élaborer une stratégie de mise en marché appropriée, selon les conditions régionales et saisonnières.

ABSTRACT Bacteriocins are small peptides, produced by many bacteria, which have adverse effects on microorganisms closely related to the producer strain. Two new Class IId bacteriocins, thuricin 17 and bacthuriocin F4 were isolated from plant growth promoting rhizobia (PGPR). Initial studies showed that both the bacteriocins can promote soybean growth. My experimental results demonstrated that these two bacteriocins promoted germination and emergence of corn, soybean, canola and wheat, but had no effect on barley, when compared with the control under optimal growth conditions. Of the tested crops, corn was most positively affected. Further abiotic stress experiments on corn showed that the two bacteriocins promoted corn emergence under low temperature, high salinity and polyethylene glycol induced water deficit stress. Field experiment data also showed that thuricin 17 can effectively promote corn emergence under cool spring field conditions in southwestern Quebec. / RÉSUMÉ Les bacteriocines sont les petits peptides produits par les bactéries qui ont des effets défavorables sur les microorganismes génétiquement proches de la souche productrice. Deux nouvelles bacteriocines de la classe IId, thuricin 17 et bacthuriocin F4, ont été isolées de bactéries présentes dans la rhizosphere et qui promouvoit la croissance des plantes (PGPR). Des études préalables ont démontré que ces deux bacteriocines peuvent promouvoir la croissance du soja. Mes résultats expérimentaux ont démontré que ces deux bacteriocines promouvoit la germination et l'émergence du maïs, du soja, du canola et du blé, mais n'ont pas d'effet sur l'orge, lorsque comparées aux contrôles sous des conditions optimales pour la croissance. Parmi les cultures testées, le maïs était le plus positivement affecté. Les expériences subséquentes sous stress abiotiques ont démontré que les deux bacteriocines ont augmenté l'émergence du maïs sous conditions de basse température, de salinité et de stress hydrique provoqué par le glycol de polyéthylène. Aussi, les expérimentations en champ ont démontré que le thuricin 17 peut promouvoir efficacement l'émergence du maïs dans le sud-ouest du Québec, où les températures printanières sont souvent fraîches.

No description available.