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The hydraulic conductance of a plant is a significant factor in determining the / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2008.

The yield of UK’s commercial oilseed rape (Brassica napus) crops has not increased over the last three decades, while a significant increase in yield has been found in trials that test new varieties before they enter the market. It has been suggested that oilseed rape is susceptible to drought and that this may contribute to the poor yield of some commercial crops. A thorough literature review revealed that there is little information on the water relations of oilseed rape crops and in particular on root growth and function and thus no strong evidence to support the above hypothesis. The aim of this thesis was to investigate root function and water relations of oilseed rape to determine whether it is more sensitive to drought than wheat, a crop species grown in rotation with oilseed rape. The water relations of wheat (Triticum aestivum L. cv. Tybalt) and oilseed rape (Brassica napus L. cv. SW Landmark) were compared in a lysimeter experiment conducted in an open sided glass house to test the hypothesis that oilseed rape was more sensitive to drying soil than wheat. Plants were grown with or without irrigation at a population density equivalent to that of commercial field crops. Irrigated oilseed rape crops transpired more water than wheat crops and oilseed rape showed a greater reduction in growth when water was withheld. The onset of drought also occurred slightly earlier in oilseed rape. In a separate experiment the root hydraulic conductance of oilseed rape, measured on a root surface area basis, was about twice that of wheat (113.1 ± 20.0 mlNm-2Nh-1NMPa-1 for oilseed rape and 53. 5 ± 10.6 for wheat). These results suggest that oilseed rape needs a less dense root system for water extraction than wheat. In the above experiment plants were grown in relatively loose soil repacked into the lysimeters. It has been suggested that oilseed rape is particularly sensitive to soil compaction, which may be a common occurrence in commercial fields. Therefore the sensitivity of oilseed rape and wheat growth to compaction was compared in an experiment under well-watered conditions. Plants were grown in a controlled environment chamber in pots packed with soil at four different bulk densities. Although the root length, shoot mass, leaf area and stomatal conductance of oilseed rape were all reduced by soil compaction, oilseed rape was no more sensitive to soil compaction than wheat under these well-watered conditions. When soil dries it also hardens and high soil strength is known to impede root growth and alter plant-water relations. The hypothesis that oilseed rape is more sensitive to increasing soil strength than wheat was tested in an experiment in which soil bulk density and soil water content were varied to create a range of soil strengths. At low soil strength oilseed rape had a greater stomatal conductance than wheat, but as soil strength increased, stomatal conductance decreased to a greater extent in oilseed rape, indicating a more sensitive response. In dense or strong soil, plants often rely on pores created by earthworms or roots of the previous crop to explore the soil volume. The ability of oilseed rape and wheat to exploit soil pores to penetrate hard soil layers was compared in a pot experiment. A hard layer, comparable to a hard–pan in a cultivated field, was created at twelve centimetre depth of each pot by packing the soil to a bulk density of 1.5 g·cm-3 relatively loose soil at a bulk density of 1.1 g·cm-3 was present above and below the layer. In one treatment seven pores were drilled through the hard layer; controls had none. Presence of pores in the hard layer led to a significant increase in number of roots in the deeper soil, of 29% for wheat and 54% for oilseed rape. This project has shown that the physiological response to drought occurred earlier in oilseed rape than in wheat and that stomatal conductance and biomass production of oilseed rape reacted more sensitively to soil drying. However, water use by oilseed rape does not seem to be limited by the ability of its roots to explore the soil and transport water compared to wheat. The growth and distribution of roots under a range of soil conditions was as good as, if not better than, that of wheat. The implications of these findings for the commercial production of oilseed rape in the UK are discussed.

Phytostabilization offers a less expensive alternative to traditional cap and plant methods for containing metalliferous mine tailings to prevent wind erosion and contamination of nearby communities and the environment. However, plant establishment during phytostabilization of pyritic legacy mine tailings in semiarid regions is challenging due to particularly extreme conditions including low pH, low organic carbon, low nutrients, and high toxic metal(loid) concentrations. Microorganisms drive major biogeochemical cycles in soils, however, the roles microorganisms play at the root – soil interface during phytostabilization, particularly in relation to plant health and metal immobilization, are not yet fully understood. The aims of this dissertation are to focus on bacterial communities associated with the roots of buffalo grass used in the phytostabilization of pyritic metalliferous mine tailings to: i) characterize bacterial diversity and communities of rhizosphere and bulk substrate, ii) delineate associations between rhizoplane bacterial colonization patterns and environmental and plant status parameters, and iii) develop an in situ method to visually assess associations between roots, bacteria, and metals. Key findings indicate that after addition of a compost amendment to alleviate the plant-growth inhibiting characteristics of mine tailings, rhizosphere and bulk substrate contain a diverse, plant-growth supporting bacterial community. As substrate re-acidifies due to compost erosion, an emergence of an iron (Fe)- and sulfur (S)-oxidizer and Fe-reducer dominated, less diverse community develops in the bulk and rhizosphere substrate, thus posing a threat to successful plant establishment. However, even at low pH, some plant-growth-promoting bacteria are still evident in the rhizosphere. On the rhizoplane (root surface), the relative abundance of metabolically active bacteria was positively correlated with plant health, verifying the strong association between plant health and bacteria. Furthermore, pH showed a strong association with the relative abundance of Alphaproteobacteria and Gammaproteobacteria on the rhizoplane. In relation to microbe-metal interactions on the root surface, results showed that Actinobacteria and Alphaproteobacteria colocalized with Fe-plaque and arsenic (As) contaminant on the root surface, indicating their potential role in adsorbing or cycling of these metal(loid)s. Developing a more thorough understanding of bacteria-root-metal interactions in relation to plant health and metal immobilization can help to improve phytostabilization efforts and success.

This essay, on Zadie Smith’s White Teeth, deals with the characters’ identities and the influences of multiculturalism on their complex identities. It also discusses the role of the characters roots and history in constructing their identities and how they have made life problematic for the characters in multicultural London. The roots and history of the first generation of immigrants make problematic identities for the second generation in the novel. The main aim of this essay is to demonstrate the instability of identity as depicted in the novel. The characters in the novel cannot ‘’plan’’ their identities because it is a process which continues in all stages of life. Though the first generation of immigrants want to ‘’plan’’ an identity for their children (the second generation of immigrants), they are not successful. Because identity is a process and it is changeable based on place and time. The second generation of immigrants, who live in London, tries to mix the dominant culture (English culture) with their familial culture in order to have a different identity. They also want to escape from their family’s roots and history but it is difficult, because leaving roots is not an easy process.

"Pictures for an audition" are a visual tool I created to help in performing orchestral excerpts. I always had the aim to get deeper in the knowledge of the Zeitgeist of the composers I was facing, and as a consequence the aim to communicate this knowledge, this richness of roots, to the audience in a way as widely understandable as possible. I have been reflecting on the role of roots and background keeping as a reference point the figure of Dvořák, due to his strong connections with the Czech land and tradition. The inspiration I get from the composers’ background influences choices I do in dynamics, colors, articulation, and most of all expression. But how to get this inspiration when the situation is that of an orchestral audition, when the excerpts are so short, different in style and background, and played in a row with just few seconds between one and the other one? It is not possible for me to remember in few seconds what is more important about a particular excerpt, not even if I would prepare a written summary, since only to read that it would take at least one minute. Instead, visual memory is instantaneous, and somehow produces in me a more immediate inspiration than written concepts. Therefore, I decided to translate into visual inputs, i.e. selected pictures, photographs, or very short evocative sentences, the concepts which are for me more relevant about five excerpts which are often required in clarinet auditions. For each excerpt, these visual inputs have been put together in a A4 paper, and the outcome I called, for the sake of simplicity, the “picture for an audition”. I used this tool during my practice; after a while I recorded myself, and, finally, I used the picture as a reference point to check if in the recording it was clear enough what I wanted to express. In this comparison, the pictures made me more attentive to details I would have otherwise overlooked, and became an inspiration also to find new ways to practice the excerpts.

Due to the relatively small amount of work concerning radiation, it was thought feasible to use ionizing radiation as a tool to study the relationship between water and salt flux in isolated root systems. Moreover, the more quantitative potometric method lends itself well to such a study, since the two processes can be followed simultaneously. the aims of this study, therefore, were 1) to determine effects of X-irradiation on water, calcium and potassium flux in excised onion roots; 2) to determine the dose levels required for producing permeability changes; 3) to investigate the nature of radiation damage to root systems; and 4) to attempt to shed light on the relation between water transport and ion movement in root systems.

O presente estudo foi realizado na Fazenda Areão, unidade da Escola Superior de Agricultura "Luiz de Queiroz", em Piracicaba - SP (22°42'30" Latitude Sul ; 47°38'30" Longitude Oeste) e teve por objetivo avaliar a dinâmica do sistema radicular do capim Tanzânia (Panicum maximum, Jacq.) quando submetido a três intensidades de manejo, correspondidas pelos resíduos pós pastejo de 1000, 2500 e 4000 kg de matéria seca verde por hectare (MSV.ha-1). A área experimental foi irrigada por pivô central, sendo pastejada por novilhos da raça nelore e manejada de forma rotacionada com ciclo de 36 dias, sendo 3 dias de ocupação e 33 dias de descanso. Foram realizadas análises quantitativas da densidade radicular através de sua massa, superfície e comprimento. As análises qualitativas se relacionaram à separação entre as raízes vivas e mortas, de maneira que pudéssemos verificar mais efetivamente o real potencial de absorção para os diferentes tratamentos, assim como o estresse imposto pelo pastejo em cada situação. O desenvolvimento do sistema radicular do capim Tanzânia mostrou comportamento inversamente proporcional às intensidades de pastejo impostas, relacionando pastejos intensos a uma retomada mais lenta na atividade de raízes. Nas condições de irrigação e adubação impostas, o resíduo 1000 kg MSV.ha-1 mostrou menor atividade radicular em relação aos tratamentos de 2500 e 4000 kg MSV.ha-1 de resíduo pós pastejo. Até 12 dias após o pastejo não houve crescimento de novas raízes, indicando que a planta fica sob condição de estresse até pelo menos 2 semanas após ser colhida, independente do manejo imposto. No entanto, para o pastejo mais intenso (resíduo 1000 kg MSV.ha-1), o desenvolvimento radicular ficou comprometido até 21 dias após o pastejo. Para as profundidades analisadas (0-20 e 0-40 cm), na média dos 3 tratamentos, em torno de 76% das raízes vivas e 82% das raízes mortas foram encontradas nos primeiros 20 cm de solo. Estes resultados indicam a possibilidade de novas pesquisas utilizarem apenas esta profundidade para amostragens, uma vez que os valores são relevantes e a dificuldade de coleta em maiores profundidades é fator limitante para trabalhos com raízes. A separação de raízes vivas pareceu ser uma boa metodologia para melhorar a acuracidade na análise dos resultados, já que amostragens do sistema radicular de plantas forrageiras apresentam variabilidade alta. Estudos que relacionem a decomposição e renovação do sistema radicular de forrageiras tropicais com fatores bióticos e abióticos deveriam ser intensificados, buscando melhor entendimento dos fluxos de tecidos da planta inteira em diferentes estações do ano. Metodologias de amostragens associadas a conceitos de interpretação estatística em processos biológicos deveriam ser revistos, uma vez que os estudos existentes sobre sistema radicular de plantas forrageiras tropicais poucas vezes são conclusivos quando interpretados pela estatística ortodoxa. / The present study was carried out at Escola Superior de Agricultura "Luiz de Queiroz", Piracicaba - SP, SP (22°42'30" S; 47°38'30" W) to evaluate the root system dynamics of irrigated Tanzania grass (Panicum maximum cv. Tanzania) pasture managed under three grazing intensities, determinated by adjusting the post grazing residues to 1000, 2500 and 4000 kg of green dry matter per hectare (GDM.ha-1). The experimental area was irrigated by a central pivot system. Nelore steers were used in a 36 days rotational grazing system, represented by an occupation period of 3 days and resting period of 33 days. Quantitative and qualitative evaluations were both performed. In the former case the variables measured were root mass, surface and length. In the latter case, collected samples were separated into live and dead roots, providing a reliable way to assess grazing intensity effects upon root system dynamics. Root system development responded inversely to grazing intensity. Hard grazing (1000 kg GDM.ha-1) was associated to slower root system regrowth compared to moderate (2500 kg GDM.ha-1) and lenient (4000 kg GDM.ha-1) grazing. In the 1000 kg GDM.ha-1 post-grazing residue no root development was observed up to three weeks, whereas for the other two treatments root regrowth was reactivated after 12 days. The three treatments averaged, 76% and 82% of live and dead roots, respectively, were found in the 0-20 cm soil layer. This information might suggest further research on root system dynamics could focus on sampling in the range of 0-20 cm depth. This seems reasonable, since the results obtained in this soil layer were representative and also because root samplings in depth greater than 20 cm (e.g. 20-40 cm) are not so easy to be performed as compared to samplings taken from 0-20 cm. Sample separation into live and dead roots provided a reliable and more accurate method to analyze the data. In part, this can be attributed to lower variability among samples. It is important to stress that additional work has to be undertaken to study decomposition and turnover of the root system of tropical pastures, as well as the relationship between these variables with biotic and abiotic factors. This effort should provide a better understanding on tissue turnover of the plant as a whole (shoots and root system). Finally, improved methods on root samplings should be developed. Also, new concepts on statistical interpretation for biological processes should be emphasized, due to difficulties in interpreting data on root system by conventional statistical methods.

O eucalipto apresenta bom crescimento em solos com alta acidez trocável e ativa, sendo a calagem uma prática realizada com o objetivo de fornecer Ca2+ e Mg2+. No entanto, o seu efeito fica restrito à camada superficial do solo devido à baixa solubilidade dos constituintes neutralizantes. A aplicação de gesso agrícola promove a movimentação de Ca2+ e SO4-2 no perfil do solo, possibilitando a melhora do subsolo para favorecer o crescimento radicular. A maioria das plantações de eucalipto no Brasil é estabelecida em solos de baixa fertilidade, verificando-se respostas significativas à fertilização com o fim de garantir a sustentabilidade da produção a longo prazo. O objetivo do presente estudo foi avaliar o crescimento da parte aérea e radicular do eucalipto em resposta à fontes e métodos de aplicação de cálcio em um Neossolo Quartzarênico. Para tal fim, foram mensurados: i) os teores de cálcio, magnésio e enxofre no solo e nas folhas; ii) a densidade de raiz fina (DRF) por biomassa ao longo do perfil e a umidade no solo, e; iii) o crescimento em altura e no diâmetro à altura do peito das árvores de Eucalyptus. A fertilização com calcário dolomítico e calcário calcinado em faixa promoveu aumento nos teores de Ca2+ e Mg2+ trocáveis no solo, especialmente nas camadas superficiais. Os teores foliares de Ca, Mg, K e S encontram-se na faixa adequada nas três datas de amostragem. O volume de tronco das árvores foi superior com a aplicação do calcário dolomítico em faixa comparativamente à aplicação de calcário dolomítico em área total ou incorporado. A mistura de calcário dolomítico com a maior dose de gesso aumentou os teores Ca2+ e Mg2+ trocáveis no solo nas camadas superficiais. A aplicação de gesso aumentou expressivamente os teores de SO42- abaixo dos 40 cm de profundidade. A DRF foi superior com a ausência da aplicação das fontes de cálcio. Com a aplicação de gesso agrícola misturado com calcário dolomítico se obteve um volume de madeira similar à aplicação de calcário dolomítico. / Eucalyptus plantations have a good development in soils with high exchangeable and active acidity, therefore, being the liming an activity done with the goal of providing Ca2+ and Mg 2+. However, its effect is restricted to the surface layer due to the low solubility of neutralizing constituents. The application of gypsum promotes the movement of Ca2+ and SO4-2 in the soil profile providing a more adequate root growth. Most eucalyptus plantations in Brazil were established in soils of low fertility, verifying significant responses to fertilization in order to ensure the sustainability of long-term production. The aim of this study was to evaluate the nutrition and aerial and root growth of eucalypts in response to different sources and methods of application of calcium in a Quartzipsamment. It was measured: i) calcium, magnesium and sulfur levels in soil and leaf; ii) Fine root density along the profile and soil moisture; iii) Growth in height and DBH of E. urophylla plantation. The fertilization with dolomitic and calcitic limestone in furrows promoted an increase in Ca2+ and Mg2+ levels in the soil, especially in surface layers. The Ca2+ and Mg2+ foliar levels found in the good range in three times. The volume of eucalypts was increased with dolomitic limestone in furrows comparatively broadcasted distribution and incorporation of dolomitic limestone. The mix of dolomitic limestone and the high gypsum level increases Ca2+ and Mg2+ levels in the soil in surface layers. Gypsum increases SO42- levels below 40 cm deep. The fine root density was higher without calcium fertilization. The volume wood with gypsum more dolomitic limestone applied was similar compared with dolomitic limestone applied.

Thesis (MTech (Horticulture))--Cape Technikon, Cape Town, 1999 / Vegetative propagation techniques for rooting of cuttings of indigenous tree species, i.e. Olea europaea subsp. African, Podocarpus falcatus, Syzigium cordatum and introduced species, i.e. Acacia mearnsii, A. melanoxylon, Eucalyptus grandis and Melia azedarach were studied and improved at the Cape Technikon nursery from May 1994 to June 1998. These tree species are considered problematic since the indigenous species produce unwanted fruits in urban areas which attract frugivores, while the introduced species are a threat to indigenous vegetation and natural habitats, though they are of great commercial value. The progress in mutation breeding of sexual sterility in most of the problematic species created a need to propagate them vegetatively. Without cloning of seedless species, their beauty and economic value to South Africa will be lost, as the indigenous species will be neglected, while invasive species will continue to threaten the natural habitat of indigenous species. Experiments were conducted to test age, type and length of cuttings, environmental factors, growth season, hormone application, various treatments and rooting media for each of these species. This study showed that relatively few publications relevant to the vegetative propagation of indigenous tree species are available. However, some introduced species, e.g. Eucalyptus grandis, are propagated successfully for commercial forestry purposes. Ficus sur and Syzicium cordatum showed the highest rooting success, i.e. 85-90%, followed by Olea europaea subsp. africana (75-80%), and Podocarpus falcatus (60%). The introduced species showed no rooting success, however, callusing in Eucalyptus grandis (35-61%), and Melia azedarach (50%), and survival rates in Acacia mearnsii (10%) and A. melanoxylon (20%) were achieved. Treatments, i.e. etiolation, placing plants under stress, sealing basal stems of cuttings, and fungicide treatments all showed positive results in promoting callusing success. The study showed that rooting success in individual species are directly related to the growth stage of parent plants as well as the season during which the cuttings were taken. With progress towards successful vegetative propagation of sterile problem plant species, propagators and horticulturists can in future apply these improved techniques. These plants will then continue to supply timber, fire wood and improve aesthetics in the South African urban environment.