Pulses are an important component in crop rotations in the semiarid Brown soil zone of southern Saskatchewan, Canada. Besides their capability to fix nitrogen, pulse crops establish a strong symbiotic relationship with arbuscular mycorrhizal fungi (AMF), which have been shown to increase nutrient and water uptake through hyphal extensions in the soil. Incorporating strongly mycorrhizal crops in a rotation may increase inoculum levels in the soil and benefit the growth of a subsequent crop. The objective of this study was to determine if AMF potential and colonization of a durum crop is significantly affected by cropping history and to assess the impact of pulses in crop rotations on the abundance and diversity of AMF communities in the soil. In 2004 and 2005, soil, plant, and root samples were taken on Triticum turgidum L. (durum) with preceding crops of Pisum sativum L. (pea), Lens culinaris Medik (lentil), Cicer arietinum L. (chickpea), Brassica napus L. (canola) or Triticum turgidum L. (durum). Although there were few differences in soil N and P levels, previous crop had a significant effect (p<0.05) on durum yields in both years. A previous crop of pea was associated with the highest yields, while the durum monocultures were lowest. Arbuscular mycorrhizal potential and colonization were significantly affected (p<0.05) by cropping history, but not consistently as a result of inclusion of a pulse crop. Phospholipid and neutralipid fatty acids (PLFA/NLFA) were completed to analyse the relative abundance of AMF (C16:1ù5), saprophytic fungi (C18:2ù6), and bacteria in the soil. The effect of treatment on the abundance of AMF, saprotrophic fungi and bacteria were not significant (p<0.05), but the changes over time were. These results demonstrate that although previous crop may play a role in microbial community structure, it is not the only influencing factor.

Pulses are an important component in crop rotations in the semiarid Brown soil zone of southern Saskatchewan, Canada. Besides their capability to fix nitrogen, pulse crops establish a strong symbiotic relationship with arbuscular mycorrhizal fungi (AMF), which have been shown to increase nutrient and water uptake through hyphal extensions in the soil. Incorporating strongly mycorrhizal crops in a rotation may increase inoculum levels in the soil and benefit the growth of a subsequent crop. The objective of this study was to determine if AMF potential and colonization of a durum crop is significantly affected by cropping history and to assess the impact of pulses in crop rotations on the abundance and diversity of AMF communities in the soil. In 2004 and 2005, soil, plant, and root samples were taken on Triticum turgidum L. (durum) with preceding crops of Pisum sativum L. (pea), Lens culinaris Medik (lentil), Cicer arietinum L. (chickpea), Brassica napus L. (canola) or Triticum turgidum L. (durum). Although there were few differences in soil N and P levels, previous crop had a significant effect (p<0.05) on durum yields in both years. A previous crop of pea was associated with the highest yields, while the durum monocultures were lowest. Arbuscular mycorrhizal potential and colonization were significantly affected (p<0.05) by cropping history, but not consistently as a result of inclusion of a pulse crop. Phospholipid and neutralipid fatty acids (PLFA/NLFA) were completed to analyse the relative abundance of AMF (C16:1ù5), saprophytic fungi (C18:2ù6), and bacteria in the soil. The effect of treatment on the abundance of AMF, saprotrophic fungi and bacteria were not significant (p<0.05), but the changes over time were. These results demonstrate that although previous crop may play a role in microbial community structure, it is not the only influencing factor.

My dissertation research investigates the genetic architecture and evolutionary significance of physiological variation in two wildflower species, Ipomopsis aggregata and Arabidopsis thaliana. In particular, my work focuses on water use efficiency (WUE), a critical physiological trait that dictates plant growth and performance in resource-limited environments. I used a combination of quantitative trait loci (QTL) mapping, field selection experiments, and classic quantitative genetics to investigate 1) the genetic architecture of water use efficiency and flowering time, 2) patterns of natural selection on water use efficiency, flowering time, and other ecological traits in I. aggregata, and 3) additive genetic variation, genetic correlations, and selection on water use efficiency, flowering time, and plasticity to drought in Arabidopsis thaliana. Using an Ipomopsis aggregata genetic mapping population, I identified four QTL underlying WUE, three QTL-QTL epistatic interactions, and evidence for a possible QTL x cytoplasmic interaction affecting WUE. I found a similar genetic architecture underlying flowering time, with four main effect QTLs that all adjacently localized to the same linkage groups as WUE, and three QTL-QTL epistatic interactions, which occur between the same chromosome pairs as the WUE interactions. The combined main and interactive effects explain 35% and 40% of the phenotypic variation in WUE and flowering time, respectively. The adjacent localization suggests a possible role for the evolution of co-inheritance or, if the true QTL positions actually overlap, a possible role for pleiotropy underlying the phenotypic correlation between WUE and flowering time. Additionally, these results suggest epistasis is a significant factor affecting phenotypic variation in nature. In a reciprocal transplant and water addition experiment, I demonstrated variable natural selection on WUE, flowering time, and nectar production in I. aggregata across elevation/habitat and differential water availability. At low elevation in the water addition treatment, natural selection favors early flowering and greater nectar sugar concentration, while dry conditions favor high WUE and early flowering time. At high elevation, where the growing season is shorter and drier, selection favors early flowering regardless of water addition. These results suggest natural selection on ecophysiological and floral traits varies with resource availability (e.g. water availability and pollinator visitation). Using data from a glasshouse experiment involving a global panel of accessions of Arabidopsis thaliana, I demonstrated strong positive genetic correlation between WUE and flowering time, as well as selection for low WUE and early flowering under experimental season-ending drought. Finally, I found significant genetic variation in plasticity as well as selection favoring greater WUE plasticity under drought, indicating plasticity to drought is adaptive in A. thaliana. / text

Grünlandfutter mit einem hohen Ertrag und gutem Futterwert ist eine Grundvoraussetzung für die effiziente Produktion von wiederkäuenden Nutztieren. Im Zuge des prognostizierten Klimawandels werden sich die Niederschlagsmuster ändern und das Auftreten von Extremwetterereignissen, wie temporärer Trockenheit, wird sich erhöhen. Besonders produktives Grünland benötigt aber eine ausreichende und regelmäßige Wasserversorgung während der Wachstumsperiode. Deshalb werden die Futterproduktion von Grünland, die Ertragsstabilität und der Futterwert von temporärer Trockenheit beeinflusst werden. Aus diesem Grund sind Anpassungsstrategien nötig, um eine zukünftige und nachhaltige Grünlandfuttererzeugung zu sichern. Erhöhte pflanzliche Biodiversität wird oft als Möglichkeit angesehen, Funktionen von Ökosystemen, wie Produktivität und Futterwert, im Grünland zu verbessern. Es gibt eine fortlaufende Diskussion wie eine erhöhte Artenzahl auf Stress, besonders Trockenstress, reagiert und wie dabei Produktivität, Futterwert und Wassernutzung beeinflusst werden. Andere Untersuchungen zeigten, dass Artidentität und die Zusammensetzung der funktionellen Gruppen wichtige Faktoren für Produktivität und Futterwert sind. Auf Grund dessen haben wir von Juli 2009 bis Juni 2011 ein Trockenstressexperiment in einer Vegetationshalle durchgeführt. Verschiedene temporäre Trockenstressereignisse wurden in drei Aufwüchsen in zwei Vegetationsperioden durchgeführt. Die klimatischen Verhältnisse in der Vegetationshalle folgten normalen saisonalen Verläufen mit Frost im Winter und höheren Temperaturen im Sommer. Trockenstress wurde induziert, indem, nach einer anfänglichen Bewässerung, die Wasserversorgung für einen bestimmten Zeitraum eingestellt wurde. Die Wasserverfügbarkeit des Bodens konnte dabei immer kontrolliert werden. Für das Experiment wählten wir ertragsstarke und landwirtschaftlich nutzbare Arten des Grünlands der gemäßigten Zonen aus. Die Arten wurden in Monokultur und Drei- sowie Fünfartenmischungen gesät und enthielten die funktionellen Gruppen Leguminose (Trifolium repens L.), Gras (Lolium perenne L., Dactylis glomerata L.) und Kraut (Plantago lanceolata L., Taraxacum officinale F.H. Wigg. agg.). Der von uns gewählt Umfang der Artenzahl zeigte schon in anderen Biodiversitätsexperimenten einen Einfluss auf die Produktion. Untersucht wurden die Effekte von Artenzahl und funktionellen Gruppen auf Ertrag, Ertragsstabilität, Wassernutzung und Futterwert (Rohprotein, wasserlösliche Kohlenhydrate, neutrale und saure Detergenzienfasern). Als Indikatoren für die Ertragsentwicklung und die agronomische Wassernutzungseffizienz (Verhältnis von Ertrag zu Wasserverbrauch) dienten der Stickstoffertrag und die Stickstoffkonzentration der Bestände sowie δ13C Signaturen, sowohl mit unlimitierter Wasserversorgung als auch mit Trockenstress. Überdies führten wir 2009 ein Kurzzeitfeldexperiment auf einem alten Grünlandbestand auf dem Versuchsgut der Universität Göttingen in Reliehausen durch. In diesem Versuch wurde ebenso der Einfluss von Trockenstress und Artenzahl auf den Ertrag und die Wassernutzung untersucht. Unsere Daten zeigten, dass Trockenstress die Produktivität verringert und die Wassernutzung beeinflusst, beides abhängig von der Stärke des Stresses. Bei moderatem Stress war die agronomische Wassernutzungseffizienz unverändert oder stieg leicht an, bei starkem Stress verringerte sie sich jedoch. Der Stickstoffertrag und die Stickstoffkonzentration waren brauchbare Indikatoren für die agronomische Wassernutzungseffizienz, wohingegen δ13C weniger geeignet war. Die agronomische Wassernutzungseffizienz wurde von Stickstoff erhöht. Es gab keinen oder nur einen sehr geringen Einfluss von Trockenstress auf den Futterwert. Saisonale Effekte hatten mehr Einfluss auf den Futterwert. Allgemein scheint der Ertragsrückgang wichtiger als die Veränderungen des Futterwerts zu sein. Die Artenzahl beeinflusste den Futterwert und die Ertragsstabilität über die Vegetationsperiode nicht. Mit Hilfe des “sampling effect“ (Probennahmeeffekt) können der manchmal positive Einfluss der Artenzahl auf den Ertrag und die agronomische Wassernutzungseffizienz und der Rückgang dieses Einflusses unter Trockenheit erklärt werden. Mit erhöhter Artenzahl stieg der Anteil der leistungsfähigen, aber trockenheitssensitiven Leguminose. Weiterhin gab es einen Hinweis, dass die Artenzahl die Geschwindigkeit des Wasserverbrauchs erhöht. Die Ergebnisse des Feldexperiments bekräftigten die Befunde bezüglich der Effekte des Trockenstresses, des Ertrages und der Wassernutzung. Aus diesen Gründen kann die „insurance hypothesis“ (Versicherungshypothese), die besagt, dass eine erhöhte Artenzahl Ökosystemfunktionen gegenüber Umweltveränderungen stabilisieren kann, nicht bestätigt werden. Jedoch waren die funktionellen Gruppen wichtige und bestimmende Faktoren der Leistung unter nicht Wasser limitierten Bedingungen und Trockenstress. Die Leguminose hatte besonders auf Ertrag, agronomische Wassernutzungseffizienz und Rohprotein einen positiven Einfluss, jedoch erhöhte sie auch den Wasserverbrauch und die saisonale Variabilität. Gräser stabilisierten den Ertrag und den Wasserverbrauch und erhöhten die wasserlöslichen Kohlenhydrate sowie die Faserfraktionen, während sie den Ertrag und die agronomische Wassernutzungseffizienz unter den stickstofflimitierten Bedingungen unseres Experiments verringerten. Die funktionelle Gruppe Kräuter zeigte ähnliche Ergebnisse bezüglich Ertrag und Wassernutzung, aber sie erhöhte das Rohprotein. Unsere Ergebnisse demonstrieren, dass die vorhergesagte Zunahme von Trockenstressereignissen die Produktion reduzieren und die Wassernutzung ändern wird. Änderungen im Futterwert werden dabei weniger wichtig als der Ertragsrückgang sein. Für die Produktion, die Wassernutzung und den Futterwert wird die Artenanzahl weniger relevant sein als die funktionelle Zusammensetzung von Grünland. Deshalb wird eine angepasste Grasnarbenzusammensetzung für die Sicherung der Produktion von wiederkäuenden Nutztieren unter den Bedingungen des erwarteten Klimawandels Bedeutung erlangen.

Cotton plant growth and development, as well as monitoring nutrient use efficiency were evaluated using hydroponic approach. Two set of experiments were conducted to determine the influence of phosphorus (P), potassium (K) and PK and exogenous application of Indole-3-acetic acid (IAA), gibberellic acid (GA3), zeatin (Z) and their combinations on growth and development of cotton plants (Gossypium hirsutum) grown hydroponically. In the nutrient solution experiment, cotton vegetative growth was positively influenced by low P (half strength Hoagland standard solution), low K (one-sixth strength Hoagland standard solution) and high PK treatments (Hoagland standard solution). Phytohormone experiment negatively supported vegetative growth except root length at 43 days after transplanting (DAT). The nutrients levels applied significantly favoured NPK uptake by cotton plants while exogenous phytohormones application did not affect NPK uptake by cotton plants, except N uptake by stem. Low P and low K treatments estimated to have high nutrient use efficiency (NUE). For chlorophyll formation, low K and high PK significantly increased formation of chlorophyll a, b and total ab while the application of GA3, IAA, Z and IAA x GA3 x 2Z treatments significantly increased chlorophyll a, b and total ab at 80 DAT only. Low K and low P treatments stimulated endogenous phytohormone contents in the cotton plants. In the phytohormone experiment, cotton plants treated to IAA x GA3 x Z increased endogenous phytohormone contents in the cotton plants. Low P, low K, high PK treatments and phytohormones treatments significantly increased root area, root volume and root activity. Low P, low K and high PK treatments applied significantly influenced residual level of P and K in the hydroponics while phytohormone treatments did not affect residual level of P and K except at 43 DAT. Evapotranspiration rate was high at early and reproductive stages of plant growth. This report shows the response of mineral nutrients and phytohormones to support growth and development of cotton plants grown hydroponically. / Description as in abstract

Wastewater treatment is traditionally considered a separate part of an industrial activity, hardly connected to the production units themselves. It is nowadays essential to ensure that the quality of water is not degraded and that water that has been polluted is purified to acceptable levels, especially in a country with scarce water resources such as South Africa. Where water quality is concerned, Zero Effluent Discharge (ZED) is the ultimate goal, in order to avoid any releases of contaminants to the water environment. The push towards ZED in South Africa is also promoted further by the South African Government’s plan to reduce freshwater usage and the pollution of water sources due to the water scarcity in a semi-arid South Africa. Future legislation will see a marked increase in the cost of freshwater usage and/or a possible limitation of the quantity of freshwater available. There is a need in the South African Industry for a framework of Best Management Practices (BMPs) in order to provide interested stakeholders, which include not only industry, but also academia, environmental interest groups and members of the public, with a procedure to meet the ZED statutory requirements. This dissertation explores the regulatory requirements and current environmental management practices implemented. A framework of BMPs to successfully attain ZED status in South African industries is developed from the literature study and the researcher’s own experience. The BMP framework embodies practices for one integrated strategy within three dimensions. The three dimensions of the BMP framework were selected to differentiate between BMPs for management (Governance BMPs), the project management team responsible for ZED projects (Project Management BMPs) and the implementation of preventative and operational measures to obtain and sustain ZED compliance for South African industries. The BMP framework was validated against the practices applied by Mittal Steel. The Mittal Steel plant in Vanderbijlpark implemented various projects, reduced the intake of water and eliminated the discharge of effluent and by doing this successfully realised their ZED status. The BMP framework will enable South African industries to develop their own BMPs Manual which should be specific to their operational and environmental requirements. The implementation of these BMPs should be tailored and used accordingly to demonstrate compliance to ZED requirements in South African industries. / Thesis (M.Ing. (Development and Management))--North-West University, Potchefstroom Campus, 2009.

Wastewater treatment is traditionally considered a separate part of an industrial activity, hardly connected to the production units themselves. It is nowadays essential to ensure that the quality of water is not degraded and that water that has been polluted is purified to acceptable levels, especially in a country with scarce water resources such as South Africa. Where water quality is concerned, Zero Effluent Discharge (ZED) is the ultimate goal, in order to avoid any releases of contaminants to the water environment. The push towards ZED in South Africa is also promoted further by the South African Government’s plan to reduce freshwater usage and the pollution of water sources due to the water scarcity in a semi-arid South Africa. Future legislation will see a marked increase in the cost of freshwater usage and/or a possible limitation of the quantity of freshwater available. There is a need in the South African Industry for a framework of Best Management Practices (BMPs) in order to provide interested stakeholders, which include not only industry, but also academia, environmental interest groups and members of the public, with a procedure to meet the ZED statutory requirements. This dissertation explores the regulatory requirements and current environmental management practices implemented. A framework of BMPs to successfully attain ZED status in South African industries is developed from the literature study and the researcher’s own experience. The BMP framework embodies practices for one integrated strategy within three dimensions. The three dimensions of the BMP framework were selected to differentiate between BMPs for management (Governance BMPs), the project management team responsible for ZED projects (Project Management BMPs) and the implementation of preventative and operational measures to obtain and sustain ZED compliance for South African industries. The BMP framework was validated against the practices applied by Mittal Steel. The Mittal Steel plant in Vanderbijlpark implemented various projects, reduced the intake of water and eliminated the discharge of effluent and by doing this successfully realised their ZED status. The BMP framework will enable South African industries to develop their own BMPs Manual which should be specific to their operational and environmental requirements. The implementation of these BMPs should be tailored and used accordingly to demonstrate compliance to ZED requirements in South African industries. / Thesis (M.Ing. (Development and Management))--North-West University, Potchefstroom Campus, 2009.

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農林水産研究情報センターで作成したPDFファイルを使用している。

農林水産研究情報センターで作成したPDFファイルを使用している。