Dissertations / Theses on the topic 'Rye grass'

Studies were conducted to explore the interactions among rye grass, chlorophenols and microorganisms. The objectives were to examine some of the processes by which plants affect the fate of subsurface organic contaminants. The research was divided into three studies: interactions between live grasses and 2,4-dichlorophenol (DCP), 2,4,6-trichlorophenol (TCP), and pentachlorophenol (PCP); physico-chemical interactions between the three chlorophenols and root tissue; and effect of root exudates on biodegradation of TCP. To study the interactions between plants and organic contaminants, rye grass plants were grown in solutions containing DCP, TCP or PCP for one to three weeks. The grass removed substantial amounts of the chlorophenols throughout the incubation time. The majority of each chlorophenol removed from solution could not be recovered by non-destructive solvent extraction. The removal of the chlorophenols from solution and the unrecoverability of the removed compound followed different kinetics, indicating that the two are different processes. Both contaminant removal and unrecoverability were closely related to root surface area but not to transpiration. A qualitative model was developed to describe the uptake of organic contaminants by plants. The data demonstrate the importance of physico-chemical interactions between contaminants and roots and suggest that maximization of root surface area should be one consideration when selecting a plant species for phytoremediation. To study the physico-chemical interactions between plant roots and organic contaminants, the distribution of DCP, TCP and PCP within a three phase system was examined. The three phases were severed grass roots, water and an organic solvent, either hexane or ethyl acetate. The chlorophenol mass that partitioned into the solvent phase was inversely correlated with root mass and root surface area index. Partition coefficients calculated with respect to the organic liquid phase were inversely correlated with root mass and root surface area index. A similar partitioning experiment was conducted using PCP placed in a solution containing only the dissolved organic material released by roots. These resulting partition coefficients decreased with increasing organic carbon concentration. It appeared that the organic compounds released into solution by the roots affected the movement of the chlorophenol into the organic liquid phase. It is proposed that the presence of roots simultaneously promoted retention of the chlorphenols in the aqueous phase and provided a sorption site. The effect of grass root exudates and glucose on the lag time associated with 2,4,6-trichlorophenol (TCP) degradation by an unacclimated microbial inoculant and an acclimated microbial inoculant was investigated. The presence of an alternate organic carbon source reduced lag time for both the acclimated microbial inoculant and the inoculant that had not been previously exposed to chlorinated phenols. The lag time for acclimation of microbes to TCP mineralization was affected by the ratio of the alternate organic carbon source concentration to the biomass concentration. It is proposed that the presence of a readily available, alternate organic carbon source affected lag time through promotion of microbial population growth and provision of a preferred source of carbon and energy. The results indicate that rye grass may directly, through partitioning and uptake, and indirectly, through soil microbes, affect the fate of chlorophenols in the subsurface environment.
Ph. D.

The aim of this study was to evaluate herbage quality of perennial ryegrass Lolium perenne using thermogravimetry. Both Dynamic and isothermal thermal analyses were investigated over a range of heating rates to first establish any association between thermal profiles and dry matter digestibility values. The results suggested thermal methods could be used to predict dry matter digestibility (in vitro DMD) and identified the best experimental protocols for further study. Further investigations were carried out to predict DMD values using discrete and continuous TG weight loss data streams by multivariate analysis. This approach enabled the successful modelling and prediction of DMD. Further studies were undertaken to investigate the application of the technique to predict digestible organic matter in the dry matter (in vivo DOMD) and Metabolisable energy values (ME). The results were again positive and indicated potential for the application of thermal methods and for further investigation. Thermal combustion and pyrolysis techniques were employed to study the key fibre fractions associated with neutral detergent fibre, acid detergent fibre and lignin to establish their relationship with thermal profiles. The results indicated that there was potential to further develop the method to predict the fibre fractions.

En las instalaciones de La Estación Experimental IVITA el Mantaro se evaluó el efecto de suplementar con ensilado, afrechillo de trigo y una mezcla de afrechillo más harina de pescado a ovinos que pastoreaban una pastura cultivada, sobre la ganancia diaria cuatro meses de edad y 20.2 Kg. de pesó vivo o en promedio, durante un periodo de 56 días.
At IVITA’s El Mantaro Reserarch Station n the central Andean Mantaro Valley was evaluated the effect of enhancing whit silage, wheat’s bran, and mixture of bran and fish meal to sheep that were grazed cultivated pasture.
Tesis

Predice la composición química de Rye grass mediante el uso de espectroscopia de reflectancia infrarrojo cercano. Analiza 29 muestras de Rye grass con diferentes tiempos de crecimiento, provenientes del valle del Mantaro ubicado a 3,200 metros de altitud. Realiza un análisis proximal, luego toma los espectros y desarrolla ecuaciones de calibración usando los métodos de mínimos cuadrados parciales y regresión de componentes principales, aplicando previamente diferentes transformaciones matemáticas de los datos espectrales. Los estadísticos obtenidos para proteína cruda, fibra bruta, extracto etéreo y ceniza tuvieron coeficientes de determinación de 0.96, 0.90, 0.83 y 0.95, respectivamente. Los modelos matemáticos obtenidos muestran que la técnica NIRS resulta satisfactoria para la determinación de dichos parámetros.
Tesis

This study investigated the fate of lignocellulosic biomass (wheat-feed and perennial rye grass) in different anaerobic digestion systems, evaluating the role of substrate specificity on the pattern of degradation. The two-stage (biohydrogen-biomethane) anaerobic system was found to be more effective in the degradation of lignocellulose, when compared to the conventional single-stage system. The perennial rye grass substrate possessed about 21% higher holocellulose concentration when compared to the wheat-feed; its exploitation in the acidogenic digestion was however poor, resulting in a 2.9% lower biogas yield in a equivalent two-stage system. The study therefore developed a treatment technique involving the use of cellulase and ferulic acid esterase enzyme combinations for the treatment of perennial rye grass. The enzyme cocktail at 0.202 ml enzyme/g VS added resulted in efficient bioconversion of the complex polymers to soluble carbohydrates, evident in the yield increase of soluble COD, to 321.0±10.9 mg/gVS, a 393.2% yield increase, when compared to the no enzyme added control. The yield of bio-hydrogen after enzymatic addition was 48ml/gVS, 335% higher when compared to the alkaline treatment; and more than seven fold higher than the yield obtained from the fermentation with no pre-treatment. The acetate to butyrate ratio varied from 4:1, when no pre-treatment was used, to 2:1when alkaline pre-treatment was used, then to 1:1 after the enzymatic treatment. The downstream effect of the prior hydrolysis on the subsequent processes to acidogenic fermentation like biomethane and PHA production and lignin recovery were also investigated. The hydrogenic/acidogenic fermentation resulted in methane yield improvement of 45.7%. The study shows that the more effective a hydrolysis procedure is in the depolymerisation of complex polymers, the greater the accumulation of PHA in the PHA biosynthesis operations. The enhanced hydrogenic /acidogenic fermentation having effectively degraded the holocellulose component of the perennial rye grass substrate ensured that relatively high quality lignin was obtained in an Organosolv lignin-extraction procedure. FT-IR profile show less contamination of polysaccharides and proteins in the lignin extracted from the enzymatically enhanced acidogenic fermentation. An evaluation of the economic viability of the investigated secondary processes showed that direct integrations of those processes to the biohydrogen process may not be as economically advantageous, when compared to a 2nd -stage biomethanation system.

La producción ovina en el Estado de México es una actividad pecuaria económica importante, pero el sistema de producción con alimentación intensiva en corral, debido a sus altos costos, en ocasiones es económicamente poco viable. Sin embargo, algunas alternativas alimenticias como el pastoreo con complementación, permiten reducir costos de alimentación y mejorar la calidad de la carne de ovinos alimentados bajo este sistema. Además, la adición del complejo zinc-metionina (Zinc-Met) en corderos, ha demostrado beneficios en la calidad de la carne referentes al mayor depósito de grasa intramuscular y modulación del perfil lipídico de la grasa. Por lo tanto, el objetivo de esta investigación fue evaluar el efecto de dos dosis de zinc orgánico en combinación con dos regímenes de consumo voluntario de concentrado en corderos en pastoreo sobre el comportamiento productivo y la digestibilidad de la MS de ovinos en pastoreo. Se utilizaron 32 ovinos, machos enteros, con peso promedio de 25.89 kg, con cinco meses de edad, F1 cuzas de las razas Dorper x Katahdin, dispuestos en 4 tratamientos con 7 repeticiones cada uno, en un diseño Completo al Azar, con arreglo factorial 2 niveles de Zinc-Met (0 y 80 ppm) x 2 regímenes de concentrado (0.75 y 1.5% del PV). La engorda duró de junio a diciembre 2019, los ovinos pastaron 8 h d-1 en una pradera de rye grass (Lolium perenne) establecida en la Facultad de Medicina Veterinaria y Zootecnia de la Universidad Autónoma del Estado de México; durante la tarde y noche, los ovinos se resguardaban en corrales individuales en la Unidad de Enseñanza e Investigación en Producción Animal, donde recibieron un complemento alimenticio (157 g de PC kg-1 MS; 2.6 Mcal de EM/kg MS). Las variables evaluadas fueron: consumo de concentrado diario, ganancia diaria de peso (GDP), conversión (CA) y eficiencia (EA) de uso del alimento. La digestibilidad aparente de la materia seca (DAMS) de los corderos en pastoreo se estimó a través del marcador óxido de cromo y, finalmente, se calculó el consumo de materia seca (CMS) total. Durante el periodo de pastoreo se evaluó en la pradera la acumulación neta de forraje (ANF) cada 15 d, asimismo, se analizó la composición química del forraje y del concentrado en el Laboratorio iii de Bromatología del Departamento de Nutrición Animal. La ANF promedio de la pradera fue 754.25 kg de MS ha-1, La composición química de Lolium perenne lo largo del periodo de pastoreo fue constante y similar en PC, MS, FDN y FDA. Se observó efecto (P<0.05) de tratamiento (T), período de medición (P) e interacción TxP en CMS total, CMS de concentrado y CMS de forraje. Asimismo, el tratamiento Zn-80 ppm con C-1.5% PV tuvo el mayor (P<0.05) peso vivo final, incremento de peso y GDP. Sin embargo, la CA, EA y DAMS fue similar (P>0.05) en todos los tratamientos. Se concluye que la restricción de concentrado en corderos en pastoreo promueve una mejor utilización de nutrientes disponibles, aumentando el consumo de alimento sin afectar la digestibilidad y eficiencia alimenticia.

La Tunisie dispose d'une multitude de biomasses sèches telles que la sciure de bois de cyprès (SBC) et humides telles que les margines générées par l'industrie oléicole. Ce travail vise en premier lieu à étudier la conversion thermochimique par pyrolyse lente du mélange de SBC/solutions chargées en métaux alcalins (K et Na) et alcalino-terreux (Mg et Ca) et de SBC/margines et par la suite à explorer la valorisation agronomique des biochars produits. Les analyses thermogravimétriques (ATG/TG) ont montré que l'imprégnation de la SBC avec les quatres minéraux (K, Na, Mg, Ca) induit des modifications significatives sur le processus de pyrolyse. En particulier, la dégradation de la cellulose est fortement influencée par la présence du potassium. De même, la température de pyrolyse ainsi que l'imprégnation avec les minéraux et les margines affectent d'une manière significative le rendement des biochars produits et leurs structures carbonés. Quant à la valorisation agronomique des biochars produits, nous avons démontré que les biochars issus de la sciure de bois imprégnée par les margines peut être utilisé comme un amendement efficace pour la fertilisation potassique de sols agricoles. En effet, une amélioration de la croissance du Ray Grass, en termes de matières fraîches, de l'ordre de 36 0/0 a été enregistrée. De plus, un taux relativement élevé d'exportation de K par la plante testée (37 g. Kg-1) a été estimé
Tunisia produces multitude of dry and wet biomass such as cypress sawdust (CS) and olive mill wastewaters (OMWW), respectively. The main aims of this research work are: i)to study the thermal conversion through slow pyrolysis of the CS impregnated With OMWW and various synthetic mineral solutions (K, Na, Mg and Ca), and ii) to explore the valorisation of the produced biochars as amendments for agricultural soils. The thermogravimetric analyzes (DTG/TG) showed that the impregnation of the CS with the four minerals (K, Na, Mg, Ca) and OMWW induced significant changes in the pyrolysis process. The highest impact was observed for the cellulose degradation in the presence of potassium. Moreover, the pyrolysis temperature as well as the nature of the impregnated mineral on the CS surface affect significantly the yield of the produced biochars and their structures. Regarding the valorisation of the produced biochars, experimental results showed that the biochars generated from the pyrolysis of CS impregnated with OMWW could be used as an efficient fertilizer for agricultural soils. Indeed, it improves by about 36 0/0 the growth of Rye Grass. Furthermore, a relatively high potassium rate was exported to Rye Grass ( (37g Kg-1 ) was registered

In Australia, significant effort goes into reducing the amount of nitrogen and phosphorus entering inland waters from point sources. However, little is known of the extent to which riparian organic matter may act as a source of these nutrients. Also, whilst the relationships between the nitrogen, phosphorus and carbon cycles are broadly known, there is little quantitative data regarding the release of these elements from Australian riparian organic matter and their subsequent microbial mineralisation within aquatic environments. In particular, comparatively little is known of their comparative role in nutrient and organic matter cycling within anoxic zones, and the influence that different riparian organic matter may have on stream water quality. This lack of such data presently hampers the ability of water managers to make educated decisions regarding the management of riparian zones in Australia. In order to improve understanding in this area, a combination of laboratory and in situ experiments were carried out in order to compare the abiotic release and aerobic/ anaerobic mineralisation of leaf derived dissolved organic carbon (DOC), dissolved nitrate/nitrite (NOx) and soluble reactive phosphorus (SRP) under different environmental conditions. Four plants common to Australian riparian zones were investigated: two native species, Eucalyptus camaldulensis (gum) and Phragmites australis (common reed), and two exotic species, Salix babylonica (willow) and Lolium multiflorum (rye grass). After 30 days, formaldehyde inhibited 1g willow and rye grass extracts contained the most SRP (0.7 mg/L), whilst gum extracts contained 0.3 mg/L and common reed 0.1 mg/L of SRP.Willow and rye grass abiotically released twice as much NOx than gum and common reed, although concentrations were only between 0.05-0.1 mg/L. Gum and common reed released the most DOC per gram of leaf matter (14 and 12 mmol/g of leaf matter respectively), but based on the initial carbon content of each leaf type, the largest percentage contributor of DOC under abiotic conditions was common reed and rye grass (both 38% mass/mass), with gum (33% mass/mass) and willow (30% mass/mass) being smaller contributors. The most bioavailable DOC was released by rye grass and common reed, with between 83 and 94% of this DOC microbially mineralised after 30 days in oxic conditions. When conditions were not inhibited, microbial growth was evident almost immediately in willow, rye grass and common reed leaf extracts. However, microbial growth was suppressed for the first 48 hours in gum leaf extracts. After this suppression period, the rate of DOC mineralisation was equal in willow and gum leaf extracts (0.1 day-1). Under anoxic conditions, the rate and extent of DOC mineralisation of willow and gum leaves depended on the type of electron acceptor provided. Added nitrate and iron III enhanced the mineralisation of both willow and gum leaves relative to no terminal electron acceptors (from zero to 0.01-0.04 and 0.002- 0.004 moles/day respectively), but added sulphate only enhanced the mineralisation of gum leaves (0.04 moles/day). When no additional electron acceptors were provided, particulate leaf mineralisation was more extensive under oxic than anoxic conditions. However, the mineralisation of leaf derived DOC were the same regardless of oxygen availability, and after 35 days in either condition the percentage of leaf DOC mineralised for each leaf type was of the order common reed > rye grass > willow > gum. All the leaf types tested were able to sustain the caddis fly larvae Triplectides australis under controlled laboratory conditions, and survival rates were high using all four leaf types as a food source. Triplectides australis did not significantly increase the amount of DOC released from each type of leaf matter, but they did consistently increase the proportion of simple carbohydrates present within the DOC fraction. The results of these experiments suggest that changes to riparian vegetation, particularly from the native to exotic species used in this study, will inherently alter in-stream concentrations of dissolved carbon and nutrients (particularly SRP). This potentially will affect in-stream, hyporheic and subsurface processes, particularly in areas where surface water flow is low and riparian leaf inputs are high.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Neste trabalho são apresentados estudos em três diferentes sistemas utilizando-se as técnicas de Ressonância Paramagnética Eletrônica (RPE) e absorção eletrônica. No primeiro estudou-se a formação dos possíveis complexos entre o aminoácido aliina, extraído do alho, e o íon cobre (II). Os dados de RPE e absorção eletronica no visível (400-1100 nm) foram utilizados para caracterizar os diferentes complexos obtidos. No segundo utilizou-se o monocristal do complexo dicloro bis (benzil difenil fosfinóxido) Cobre (II) e efetuaram-se medidas de RPE variando-se a direção de aplicação do campo magnético no monocristal. Os auto-valores encontrados para as componentes do tensor g¯ foram: g1= 2,0891; g2= 2,4554 e g3= 2,0767. Com base nos dados de RPE e cristalográficos e usando a teoria de campo cristalino foi proposto dxy como estado fundamental para o íon cobre (II) neste complexo. Fez-se também um estudo preliminar observando-se as variações no centro ativo de hemoproteínas moduladas pelo grau de hidratação. Metahemoglobina bovina e metamioglobina eqüina liofilizadas foram usadas e o sinal de RPE do íon ferro (III) monitorado. Dos espectros de RPE das duas proteínas são observadas pelo menos duas simetrias para o íon ferro (III), uma axial caracterizada por um valor de g próximo de 6 e outra caracterizada por g= 4,3 correspondendo a simetria rômbica. A intensidade dos sinais mostrou-se muito sensíveis ao grau de hidratação. Metahemoglobina e metamioglobina apresentaram comportamentos distintos dos sinais de RPE e sugeriu-se serem eles devido as diferenças estruturais entre as duas proteínas
In this work studies in three different systems using Electron Paramagnetic Resonance (EPR) and eletronic absorption techniques are presented. The formation of possible complexes between the amino acid aliin, extracted of garlic, and the copper (II) íon was studied in the first work. EPR and visible eletronic absorption (400-1100 nm) data were utilized to characterize the different complexes obtained. In the second work a crystal of the complex dichloro bis (benzyl diphenyl phosphinoxide) copper (II) was used and the EPR measures were made for different directions of application of the magnetic field in the crystal. The eigenvalues obtained for the g¯ tensor components were: g1= 2,0891; g2= 2,4554 and g3= 2,0767. Using EPR and crystallographic data and crystal field theory dxy was proposed as the ground state of the copper (II) íon in this complex. A preliminary study was also made observing changes at the active Center of the hemeproteins modulated by the hydration degree. Lyophilized bovine methemoglobin ande quine metmyoglobin were used and the EPR signal of the iron (III) íon monitored. Or both proteins the EPR spectra corresponding to at least two iron symmetries were observed, one axial characterized by a g value near 6.0 and another characterized by g= 4,3 corresponding to rhombic symmetry. The intensity of these signals were very sensitive to the hydration degree. Metmyoglobin and methemoglobin showed distint behaviors of the EPR signals and it was suggested that they were due to structural differences between the two proteins

The aim of the thesis is to determine the relation between subjectively perceived and financially measured performance of a firm. The introduction of the thesis is focused on performance characteristics and measurement. Further, based on foreign and domestic researches, subjectively perceived performance is defined and comparison with objectively (financially) measured one is made. Results of the researches prove that between subjectively perceived and financially measured performance, there exists substantial to very strong statistical association. Following on an own research was carried out. As the tool for data collection serves a questionnaire sent to firms from the Czech and Slovak Republic. The data collected are compared with values of select financial measures: with ROA, ROE, ROS and Gross Sales. Said own research also confirmed a positive correlation between subjectively perceived and financially measured performance of the firm, albeit weaker than in foreign researches.

Les alterations fonctionnelles et metaboliques du myocarde ont ete etudiees au cours de l'ischemie et de la reperfusion en utilisant le modele du cur de rat isole perfuse. Dans un premier temps, nous nous sommes interesses a la mise en evidence de l'implication des radicaux libres oxygenes dans la pathogenese des dommages cardiaques. Pour cela, un systeme de detection par rpe en mode continu a ete mis au point. La methode de spin trapping a permis de determiner qu'il y a une formation constante de radical hydroxyle dans le cur pendant une ischemie a debit coronaire reduit et une production massive de ce radical dans les premieres minutes de la reperfusion. De plus, le suivi en direct dans le temps de la fuite extracellulaire du radical ascorbyle provenant de l'oxydation d'un antioxydant endogene, la vitamine c, a permis d'evaluer l'importance des dommages radicalaires dans le myocarde. Dans une seconde partie, nous avons compare les effets de differents acides gras physiologiques a longue chaine au cours d'une periode d'anoxie (sans reduction du debit coronaire) et de reoxygenation, sur la recuperation fonctionnelle et metabolique post-anoxique. L'utilisation de la rmn du phosphore-31 a permis la mesure du contenu tissulaire en atp et en creatine phosphate ainsi que celle du ph intracellulaire. L'acide oleique s'est revele d'une toxicite importante, alors que les acides gras polyinsatures: linoleique, alpha et gamma-linoleniques sont cardioprotecteurs

Ce travail constitue une caractérisation des films de Langmuir-Blodgett par résonance paramagnétique électrique et par diffusion Raman résonante en lumière polarisée. Les films sont constitués de multicouches, mixtes ou alternées, de porphyrines amphiphiles et d'acide docosanoïque. Le sujet porte sur l'orientation des macrocycles porphyriniques par rapport au substrat supportant les couches

Bromus diandrus and Lolium rigidum are winter annual grass weeds that have become serious weeds of cereal crops in Australia. Surveys of Australian grain growers over the last 20 years have consistently shown L. rigidum to be one of the most troublesome weeds. Characteristics such as staggered seed germination, herbicide resistance and adaptation to environmental stresses have also made B. diandrus an increasing problem of crop production systems in Australia. From recent studies, some evidence has emerged of changes in germination behaviour of these weeds species that may be making their management more difficult. Studies of genetic variation in seed dormancy within populations of these weeds may help to better understand adaptive response of these weed species to changes in management practices. Even though several researchers have highlighted the need to understand genetic control of weed seed dormancy, not many researchers have investigated this topic. Seed dormancy was assessed in five B. diandrus populations collected from wheat fields in cropping areas of South Australia in 2017. Seedling emergence pattern showed large differences in seed dormancy among these populations. Time to 50% seedling emergence (t50) for B. diandrus populations ranged from 10.3 to 28.5d. Seedling emergence in these populations of B. diandrus continued for up to 80d which provided an opportunity to select early and late emerging cohorts within each population in 2018 and 2019. Evaluation of seeds of the progeny of these cohorts in 2019 and 2020 consistently showed significant differences in seed dormancy. Seeds produced by early cohorts had a lower dormancy than seeds of late cohorts. For example, the seeds of the early cohort of Riverton population had t50 of 23.5d as compared to 46d for the late cohort. A similar pattern of differences in t50 between the seeds of early and late cohorts was also observed in Mallala population. Consistent differences in seed dormancy expression between the early and late cohorts of the same population clearly indicated that the expression of seed dormancy in these cohorts was under strong genetic control. In order to identify genes associated with differences in seed dormancy, seeds of early and late cohorts of Riverton and Mallala were analysed for the expression of ABA1 and GA20ox genes using qPCR at 30, 60, 90 and 120 days after maturity. Higher ABA1 and lower GA20ox gene expression was observed in seeds of late cohorts (high dormancy) compared to the early emerging cohorts (low dormancy). During the after-ripening period, the expression of GA20ox increased and ABA1 decreased, which was correlated with the loss of seed dormancy in late emerging cohorts. These studies have shown large differences in seed dormancy between individuals present within the same populations of B. diandrus. Presence of genetic variation for this important trait could play an important role in their adaptation to escape pre-sowing weed control tactics and become an even greater problem in field crops grown in this region. Similar studies of seed dormancy were also undertaken on L. rigidum. Seeds of seven L. rigidum populations were collected in 2017 from wheat fields on three commercial farms in the medium (Paskeville and Roseworthy) and high (Hilltown) rainfall areas of South Australia. Presence of greater than two-fold differences in seed dormancy between populations from the same farm indicates likely influence of management practices on selection for seed dormancy. For example, the time taken to reach 50% (t50) of total seasonal seedling emergence for 3 populations from a single farm at Roseworthy ranged from 11d to 27d. Similarly, t50 for 2 populations from a farm at Hilltown varied from 13d for HT1 to 23d for HT2. Occurrence of seedling emergence over a long period in L. rigidum populations provided an opportunity to select low (LD) and high dormancy (HD) cohorts. Seeds produced by these cohorts of three L. rigidum populations over two years showed significant differences in seed dormancy between them. Seeds of low and high dormancy cohorts of HT2, PSK1 and RAC3 were concurrently analysed for seed dormancy and the expression of ABA1 and GA20ox using qPCR at 30, 60 and 90 days after maturity. Greater ABA1 and lower GA20ox gene expression was observed in seeds of high dormancy cohorts than in low dormancy cohorts. During the after-ripening period, the expression of GA20ox increased and ABA1 decreased, which was significantly correlated with seed dormancy. The results from this investigation provide evidence for genetic control of seed dormancy in field populations of L. rigidum. Presence of heritable genetic variation in seed dormancy in L. rigidum populations will allow this weed to rapidly adapt to changes in weed management practices such as delayed sowing of crops. As water stress during spring time can be a frequent occurrence in Australian grain growing regions, studies were undertaken to determine the impact of moisture stress during reproductive development on seed dormancy in B. diandrus and L. rigidum populations. Seeds of these populations were also investigated for the expression of genes involved with GA and ABA synthesis. Seeds collected from plants of both species exposed to water stress from GS31 onwards were the most dormant in both weed species. In contrast, plants that were well-watered (control) produced seeds with the lowest dormancy. The seeds collected from the well-watered treatment of both L. rigidum and B. diandrus populations reached 50% germination at 90 days after maturity (DAM) while the germination of stress at GS31 was approximately 50-67% lower than the well-watered (control) treatment. Water stress treatments altered the expression of ABA1 and GA20ox genes which was correlated with the level of dormancy in seeds of B. diandrus and L. rigidum. The ABA1 expression levels were high at 30DAM but decreased during the after-ripening periods. This coincided with the gene expression levels of GA20ox, which were low soon after maturity but gradually increased. The 2-fold increase in the GA20ox levels in all the populations and stress treatments at 90-150DAM points towards the loss of seed dormancy. The differences observed in the seed germination behaviour of water stressed vs non stressed treatments and also the gene expression levels of ABA1 and GA20ox highlighted the fact that effects of water stress on seed dormancy are mediated through these dormancy regulating genes in these two weed species.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2022

No information is available on the role of allelopathy in crop rotation systems of the Western Cape Province of South Africa, where more than 100 000 ha are under threat from herbicide-resistant rye grass. A study which investigated the use of allelopathic properties for the suppression of rye grass hybrid type (Lolium multiflorum x perenne) was undertaken. These objectives were accomplished by: a) exploring the use of allelopathic properties of crop residues for rye grass suppression; b) evaluation of the role of allelopathy from seeds, seedlings, roots and above-ground plant material of rotational crops; c) assessing the distribution of genetic and morphological variability of rye grass and d) determining the interactions among micro-organisms and allelopathic root leachates from rotational crops and rye grass. In the field trials, growth inhibitory or stimulatory effects were observed on crops exposed to the residues of others. Medic suppressed the weed type rye grass. The radicle length of rye grass was inhibited by seed leachates from wheat and lupine. Growth inhibition from lupine seed and seedling leachates was evident in rye grass radicle length and cumulative germination percentage. Morphologically, 50% of the total number of specimens was classified as rigid rye grass, 48% as the hybrid, namely L. multiflorum x perenne and 2% as perennial rye grass. The wide genetic and morphological variation detected in rye grass may be due to high genotypic plasticity and hybridisation for producing the weed type L. multiflorum x perenne. The faster growth rate of rye grass on Langgewens soil treated with barley root leachates was revealed by Principal Component Analysis (PCA) as a probable association with growth-promoting soil micro-organisms. Crop cultivars and weeds may modify the soil micro-organism populations to their advantage and to the disadvantage of other species by the release of root exudates that apparently differ in composition between plant species. The effect on microbial communities varied with source of exudates and between soils.
Thesis (PhD)--University of Pretoria, 2011.
Plant Production and Soil Science
unrestricted

Goats are found in almost every country and are an important source of protein and produce lactose-free milk. In South Africa, survival rates of goat kids are low, mainly due to malnutrition. Intensive goat production systems based on cultivated pastures were evaluated, at various stocking rates to evaluate the effects of improved nutrition on goat production. The pastures chosen to be evaluated for goat production were Pennisetum clandestinum (Kikuyu) and Secale cereale (Stooling rye). Kikuyu is one of the more important dryland summer pasture species in KwaZulu-Natal. Three stocking rates of goats on kikuyu were evaluated using ewes with kids. When analysing the period to weaning, the ewes lost weight in all stocking rate treatments and for both years. The years had a significant effect on weight loss (P<0.001; R²=95.7%) with a mean ADG of -0.0267 kg.animalˉ¹.dayˉ¹. There was a significant difference between ADGs between stocking rates, with ADGs of -0.0157, -0.026 and -0.0384 kg.animalˉ¹.dayˉ¹ at stocking rates of 30, 45 and 60 goats.haˉ¹ respectively (P<0.001; R²=95.7%). The analyses of the entire grazing period showed no significant difference in ewe ADGs between treatments, but a significant difference between the two years (P=0.03), with a mean ADG of -0.0205 kg.animalֿ¹.dayֿ¹. There was no significant difference between kid masses between treatments. There was a significant difference between kid performance between years (P<0.001; R²=21.8%). However, factors such as ewe start mass (P<0.001) and whether the kid was a singleton or a multiple (P=0.015) had an influence on kid ADG, while gender had no significant effect (P=0.446). Interpretation of the combined ewe plus kid weight revealed that the high stocking rate produced the highest total mass per hectare (P<0.001) with an overall mean of 2377 kg.haˉ¹. Kid ADG was positively correlated to ewe ADG (P=0.013; R²=5.8%) although this was not a strong relationship. Protein was negatively correlated to pasture height (P=0.036; R²=30.8%) and had a quadratic relationship with ADG (P<0.001; R²=48.4%) with maximum ADG occurring at protein levels of 26.17%. Rainfall was different between the two seasons, which affected pasture growth, with the stocking rates in the second year being too low, so the maximum stocking rate per hectare was not reached. Stooling rye is a pasture used predominantly in South Africa and is a good source of high quality winter feed. Four stocking rates were evaluated over winter, using pregnant ewes. Rainfall was not an important variable since supplementary irrigation was given and the difference in temperatures between the years was negligible. The rate of weight gain showed a similar response for both years with the level of weight gain varying significantly between years (P=0.001; R²=90.2%). The regressions for ADG on stocking rate were determined and were y=0.2340-0.00293x for 2001 (P=0.151; R²=58.0%) and y=0.1292-0.002198x for 2002 (P=0.137; R²=61.6%). Gain per hectare was determined, as were the stocking rates at which maximum gain per hectare were achieved and this was determined to be 40 goats.haֿ¹ during 2001 and 29 goats.haֿ¹ for 2002. The respective ADGs at these stocking rates were 0.1168 and 0.0633 kg.dayֿ¹ and daily gains.haֿ¹ were 4.672 and 1.898 kg.haֿ¹.dayֿ¹ respectively. Herbage analyses revealed that there were extremely high levels of protein in the pasture (33.87%) even though the pasture was not excessively fertilised. Average daily gain was negatively related to NDF levels (P=0.006; R²=38.4%). ADF levels (P<0.001; R²=48.4%) and NDF levels (P<0.001; R²=60.4%) showed a quadratic relationship with pasture age. Blood serum revealed that selenium levels in all treatments were lower than the normal range, while all other minerals were within the normal range. To maximise animal performance, the highest quality pasture should be offered to producing animals, namely growing animals. The seasonal variation between years has a large effect on the performance of goats on pastures.
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

The study compared survival and growth rate in grass carp (Ctenopharyngodon idella) juveniles in pond and recirculation aquaculture system (RAS) during winter time. The juveniles of grass carp were stocked to 5 tanks and three ponds during 2013 and 2014. In the RAS, the fish were fed by dry pellets and rearing was in constant temperature. In the pond, the temperature and feeding were only natural. In the RAS, the survival rate was significantly higher 97.79 % 0.52 % compared to 10.94 % 11.42 % in the pond. At the end of experiment, the weight of fish, Specific growth rate (SGR) and Fulton coefficient (FK) was significantly higher in RAS in comparison with the pond. The results showed that the rearing of grass carp is more effective in RAS in comparison with pond during winter time.