A busca por alimentos saudáveis, seguros e sustentáveis tem levado a um grande aumento do consumo de alimentos orgânicos, em todo o mundo. Embora esses alimentos sejam claramente menos expostos aos perigos químicos, diversos estudos têm demonstrado contaminação microbiológica significativa em produtos como as alfaces orgânicas, as quais são amplamente comercializadas. Dessa forma, o objetivo deste estudo foi avaliar a cadeia produtiva de alfaces orgânicas no sul do Brasil, através de análises microbiológicas e dos sistemas de gestão da inocuidade, buscando identificar possíveis medidas de intervenção a partir do ponto de vista da segurança dos alimentos. Três propriedades rurais de alface orgânica foram analisadas, utilizando as ferramentas Horticultural Assessment Scheme (HAS) e Horticulture Safety Management System Diagnosis (HSMS-DI). Amostras de adubo, solo adubado, mudas de alface, alface, água de irrigação e lavagem foram coletadas ao longo da cadeia produtiva, seguindo a ordem de inicio do plantio, durante o crescimento e na colheita das alfaces. As análises microbiológicas foram realizadas segundo o protocolo do HAS e normas internacionais. Para avaliação dos sistemas de gestão de segurança dos alimentos a ferramenta de diagnóstico HSMS-DI, com 58 questões, foi aplicada em cada propriedade rural. As Informações obtidas no HAS e HSMS-DI foram combinadas e um diagnóstico de cada propriedade foi elaborado, assim como foram sugeridas medidas de intervenção. Os resultados do HSMS-DI indicaram que as propriedades rurais apresentavam clara organização e forte embasamento quanto à prevenção dos riscos químicos, no entanto estavam operando em um contexto de risco microbiológico moderado a elevado. Os resultados obtidos com o HAS demonstraram contaminação por microrganismos de origem fecal em diversas amostras, além disso, foi detectada a presença de E. coli O157:H7 na água de irrigação e lavagem das alfaces, e a presença de Salmonella em adubo. Estes resultados demonstraram a existência natural e inerente de fontes de contaminação microbiológica na cadeia de produção de alfaces orgânicas. Contudo, destaca-se a necessidade de maior apoio aos produtores orgânicos, principalmente na implementação de medidas de controle da compostagem dos adubos e na qualidade da água de irrigação e lavagem dessas propriedades. / The search for healthy, safe and sustainable food has led to a large increase in the consumption of organic foods worldwide. Although these foods are clearly less exposed to chemical hazards, several studies have demonstrated significant microbial contamination in products such as organic lettuces, which are widely marketed. Thus, the aim of this study was to evaluate the production chain of organic lettuce in southern Brazil, through microbiological analyses and safety management systems in order to identify potential measures from the point of view of food safety. Three rural properties of organic lettuce were analyzed using the Horticultural Assessment Scheme (HAS) and the Horticulture and Safety Management System Diagnosis (HSMS-DI) tools. Samples of compost, fertilized soil, lettuce seedlings, lettuce, irrigation and wash water were collected along the production chain, following the beginning of the planting, the growing and the harvesting of lettuce. Microbiological analyzes were performed according to protocol HAS and international standards. For evaluation of the food safety management, the diagnostic tool HSMS-DI, with 58 questions, was administered to each farm. Information collected on HAS and HSMS-DI was combined and a diagnosis of each property was developed, as were suggested intervention measures. The results of the HSMS-DI indicate that the farms had clear and strong organizational foundation for the prevention of chemical risks, however, were operating in a context of moderate to high microbiological risk. The results obtained with the HAS showed contamination by microorganisms of fecal origin in several samples, furthermore, we detected the presence of E. coli O157: H7 in irrigation and wash water, and the presence of Salmonella in manure. These results demonstrated the existence of inherent and natural sources of microbiological contamination in the production chain of organic lettuces. However, there is a need for greater support for organic producers, especially in the implementation of control measures for fertilizer composting and in the quality of irrigation and wash water of these properties.

A busca por alimentos saudáveis, seguros e sustentáveis tem levado a um grande aumento do consumo de alimentos orgânicos, em todo o mundo. Embora esses alimentos sejam claramente menos expostos aos perigos químicos, diversos estudos têm demonstrado contaminação microbiológica significativa em produtos como as alfaces orgânicas, as quais são amplamente comercializadas. Dessa forma, o objetivo deste estudo foi avaliar a cadeia produtiva de alfaces orgânicas no sul do Brasil, através de análises microbiológicas e dos sistemas de gestão da inocuidade, buscando identificar possíveis medidas de intervenção a partir do ponto de vista da segurança dos alimentos. Três propriedades rurais de alface orgânica foram analisadas, utilizando as ferramentas Horticultural Assessment Scheme (HAS) e Horticulture Safety Management System Diagnosis (HSMS-DI). Amostras de adubo, solo adubado, mudas de alface, alface, água de irrigação e lavagem foram coletadas ao longo da cadeia produtiva, seguindo a ordem de inicio do plantio, durante o crescimento e na colheita das alfaces. As análises microbiológicas foram realizadas segundo o protocolo do HAS e normas internacionais. Para avaliação dos sistemas de gestão de segurança dos alimentos a ferramenta de diagnóstico HSMS-DI, com 58 questões, foi aplicada em cada propriedade rural. As Informações obtidas no HAS e HSMS-DI foram combinadas e um diagnóstico de cada propriedade foi elaborado, assim como foram sugeridas medidas de intervenção. Os resultados do HSMS-DI indicaram que as propriedades rurais apresentavam clara organização e forte embasamento quanto à prevenção dos riscos químicos, no entanto estavam operando em um contexto de risco microbiológico moderado a elevado. Os resultados obtidos com o HAS demonstraram contaminação por microrganismos de origem fecal em diversas amostras, além disso, foi detectada a presença de E. coli O157:H7 na água de irrigação e lavagem das alfaces, e a presença de Salmonella em adubo. Estes resultados demonstraram a existência natural e inerente de fontes de contaminação microbiológica na cadeia de produção de alfaces orgânicas. Contudo, destaca-se a necessidade de maior apoio aos produtores orgânicos, principalmente na implementação de medidas de controle da compostagem dos adubos e na qualidade da água de irrigação e lavagem dessas propriedades. / The search for healthy, safe and sustainable food has led to a large increase in the consumption of organic foods worldwide. Although these foods are clearly less exposed to chemical hazards, several studies have demonstrated significant microbial contamination in products such as organic lettuces, which are widely marketed. Thus, the aim of this study was to evaluate the production chain of organic lettuce in southern Brazil, through microbiological analyses and safety management systems in order to identify potential measures from the point of view of food safety. Three rural properties of organic lettuce were analyzed using the Horticultural Assessment Scheme (HAS) and the Horticulture and Safety Management System Diagnosis (HSMS-DI) tools. Samples of compost, fertilized soil, lettuce seedlings, lettuce, irrigation and wash water were collected along the production chain, following the beginning of the planting, the growing and the harvesting of lettuce. Microbiological analyzes were performed according to protocol HAS and international standards. For evaluation of the food safety management, the diagnostic tool HSMS-DI, with 58 questions, was administered to each farm. Information collected on HAS and HSMS-DI was combined and a diagnosis of each property was developed, as were suggested intervention measures. The results of the HSMS-DI indicate that the farms had clear and strong organizational foundation for the prevention of chemical risks, however, were operating in a context of moderate to high microbiological risk. The results obtained with the HAS showed contamination by microorganisms of fecal origin in several samples, furthermore, we detected the presence of E. coli O157: H7 in irrigation and wash water, and the presence of Salmonella in manure. These results demonstrated the existence of inherent and natural sources of microbiological contamination in the production chain of organic lettuces. However, there is a need for greater support for organic producers, especially in the implementation of control measures for fertilizer composting and in the quality of irrigation and wash water of these properties.

A busca por alimentos saudáveis, seguros e sustentáveis tem levado a um grande aumento do consumo de alimentos orgânicos, em todo o mundo. Embora esses alimentos sejam claramente menos expostos aos perigos químicos, diversos estudos têm demonstrado contaminação microbiológica significativa em produtos como as alfaces orgânicas, as quais são amplamente comercializadas. Dessa forma, o objetivo deste estudo foi avaliar a cadeia produtiva de alfaces orgânicas no sul do Brasil, através de análises microbiológicas e dos sistemas de gestão da inocuidade, buscando identificar possíveis medidas de intervenção a partir do ponto de vista da segurança dos alimentos. Três propriedades rurais de alface orgânica foram analisadas, utilizando as ferramentas Horticultural Assessment Scheme (HAS) e Horticulture Safety Management System Diagnosis (HSMS-DI). Amostras de adubo, solo adubado, mudas de alface, alface, água de irrigação e lavagem foram coletadas ao longo da cadeia produtiva, seguindo a ordem de inicio do plantio, durante o crescimento e na colheita das alfaces. As análises microbiológicas foram realizadas segundo o protocolo do HAS e normas internacionais. Para avaliação dos sistemas de gestão de segurança dos alimentos a ferramenta de diagnóstico HSMS-DI, com 58 questões, foi aplicada em cada propriedade rural. As Informações obtidas no HAS e HSMS-DI foram combinadas e um diagnóstico de cada propriedade foi elaborado, assim como foram sugeridas medidas de intervenção. Os resultados do HSMS-DI indicaram que as propriedades rurais apresentavam clara organização e forte embasamento quanto à prevenção dos riscos químicos, no entanto estavam operando em um contexto de risco microbiológico moderado a elevado. Os resultados obtidos com o HAS demonstraram contaminação por microrganismos de origem fecal em diversas amostras, além disso, foi detectada a presença de E. coli O157:H7 na água de irrigação e lavagem das alfaces, e a presença de Salmonella em adubo. Estes resultados demonstraram a existência natural e inerente de fontes de contaminação microbiológica na cadeia de produção de alfaces orgânicas. Contudo, destaca-se a necessidade de maior apoio aos produtores orgânicos, principalmente na implementação de medidas de controle da compostagem dos adubos e na qualidade da água de irrigação e lavagem dessas propriedades. / The search for healthy, safe and sustainable food has led to a large increase in the consumption of organic foods worldwide. Although these foods are clearly less exposed to chemical hazards, several studies have demonstrated significant microbial contamination in products such as organic lettuces, which are widely marketed. Thus, the aim of this study was to evaluate the production chain of organic lettuce in southern Brazil, through microbiological analyses and safety management systems in order to identify potential measures from the point of view of food safety. Three rural properties of organic lettuce were analyzed using the Horticultural Assessment Scheme (HAS) and the Horticulture and Safety Management System Diagnosis (HSMS-DI) tools. Samples of compost, fertilized soil, lettuce seedlings, lettuce, irrigation and wash water were collected along the production chain, following the beginning of the planting, the growing and the harvesting of lettuce. Microbiological analyzes were performed according to protocol HAS and international standards. For evaluation of the food safety management, the diagnostic tool HSMS-DI, with 58 questions, was administered to each farm. Information collected on HAS and HSMS-DI was combined and a diagnosis of each property was developed, as were suggested intervention measures. The results of the HSMS-DI indicate that the farms had clear and strong organizational foundation for the prevention of chemical risks, however, were operating in a context of moderate to high microbiological risk. The results obtained with the HAS showed contamination by microorganisms of fecal origin in several samples, furthermore, we detected the presence of E. coli O157: H7 in irrigation and wash water, and the presence of Salmonella in manure. These results demonstrated the existence of inherent and natural sources of microbiological contamination in the production chain of organic lettuces. However, there is a need for greater support for organic producers, especially in the implementation of control measures for fertilizer composting and in the quality of irrigation and wash water of these properties.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Richard H. Mattson / Medical and psychological responses of patients recovering from surgery were evaluated in hospital rooms with ornamental indoor plants. Three clinical studies were conducted in two hospitals with 80 thyroidectomy patients, 90 appendectomy patients, and 90 hemorrhoidectomy patients. Patients in each surgical procedure were randomly assigned to either control or plant rooms. Eight species of foliage and flowering plants were placed in the hospital rooms during the recovery period following surgery until discharge. Data collected from each patient included length of hospitalization, analgesics used for postoperative pain control, vital signs (blood pressure, temperature, heart rate, and respiratory rate), ratings of pain intensity, pain distress, anxiety and fatigue (PPAF), the State-Trait Anxiety Inventory Form Y-1 (STAI-Y1), the Environmental Assessment Scale (EAS), and the Patient’s Room Satisfaction Questionnaire (PRSQ). Effects were assessed by analysis of covariance and the exact chi-square test. Patients in the plant rooms had significantly more positive health outcomes than those in the control group with no plants. Patients exposed to plants experienced shorter hospitalizations, fewer intakes of postoperative analgesics, more positive physiological responses, and less pain, anxiety, and fatigue than patients in the control group. Patients with plants also felt more positively about their rooms and evaluated them with higher satisfaction as compared to those in the control group. Based on patients’ comments, plants brightened up the room environment, reduced stress, and also conveyed positive messages of the hospital caring for patients. Findings of this study confirmed the therapeutic value of plants in the hospital environment as a noninvasive, inexpensive, and effective intervention for surgical patients in a general hospital ward. Outcomes of this study will substantially affect patients’ and hospital administrators’ decisions that indoor plant intervention can foster improved medical outcomes, increase satisfaction with providers, and be acceptably cost effective as compared to other alternatives.

La gestion de l’irrigation et de la fertilisation dans les systèmes de production hors sol est particulièrement cruciale afin de limiter tous risques d’asphyxie racinaire, de lessivage d’éléments minéraux, voire de développement de pathogènes liés à une irrigation excédentaire, ou, à l’inverse, de réhumectation délicate et de stress hydrique de la plante dans des conditions limitantes en eau. Ayant pour finalité d’améliorer l’efficience de l’eau pour les plantes cultivées sur substrats, les travaux développés dans cette thèse ont visé à analyser l’évolution des propriétés hydrauliques de différents substrats au cours de laculture, en se focalisant tout particulièrement sur les effets combinés du développement racinaire et de la gestion de l’irrigation.Des essais culturaux ont été menés sur tourbe, fibres de coco, fibres de bois et écorce, prenant pour plante modèle utilisée le rosier Knock Out®. Des mesures de biomassesracinaires et aériennes, ainsi que celles des propriétés de rétention en eau et en air, de conductivité hydraulique, de diffusivité des gaz et de mouillabilité ont été effectuées surchaque substrat soumis à des régimes d’irrigation différents (variant d’un optimum hydrique à des conditions de stress hydrique). Les résultats montrent d'importantes modifications aufil du temps, principalement en raison de l'histoire hydrique. Cela conduit à des modifications(1) de la distribution et de la taille des pores, traduite par une réduction de leur tortuositéqui génère une augmentation de la diffusion gazeuse dans le milieu, ainsi que (2) unediminution de / Precise irrigation management of substrates is of vital importance in horticultural soilless systems to avoid root asphyxia, nutrient leaching, and plant disease in case of excessive watering; as well as, nutrient and water deficiency, and then plant physiological stress in the driest conditions. The study presented here aimed to improve water efficiency for plants grown in pots or containers, focusing on the evolution of hydraulic properties of substratesdue to root development and irrigation strategies during plant growth. Crop trials were performed on peat, coir, wood fiber and pine bark, using the rose Radrazz Rosa x hybrida as plant model.Shoot and roots biomasses, air and water retention properties, hydraulic conductivity, relative gas diffusivity and wettability were measured on each substrate, managed with different irrigation strategies (from an optimal water content to hydric stress conditions). Results showed significant changes over time, mainly due to the hydric history. This led to changes (1) in pore distribution and size, and then a decrease in pore tortuosity generating an increase in relative gas diffusivity in the substrates, and (2) a decrease in substrates’ wettability according to the intensity of drying. Although they were with weaker amplitude to those resulting of the hydric history, filling of macroporosity by the root system led to limit substrates’ consolidation due to drying/wetting cycles, and moreoverto amplify pore connectivity and then relative gas diffusivity and to limit degradation inwettability.

<p>Plant microbiomes are increasingly recognized for their potential to help plants with critical functions such as nutrient acquisition. Nitrogen is the most limiting nutrient in agriculture and growers apply substantial amounts to meet crop needs. Only 50% of N fertilizers are generally taken up by plants and the rest is subject to loss which negatively affects environmental quality. Organic fertilizers such as cover crops and animal manure can help reduce this loss, though these materials must mineralize via microbial mediated processes before they are available for plant uptake, which makes managing fertility using these sources difficult. Some plants can scavenge nutrients from organic materials by stimulating positive priming processes in soil. Carrot (<i>Daucus carota.</i> L) is known as an N scavenging crop, making it an ideal model crop to study these interactions. In a greenhouse trial, soils were amended with an isotopically labeled corn residue to track N movement, and planted with one of five carrot genotypes expected to differ in nitrogen use efficiency (NUE). Changes in soil b-glucosidase activity, ammonium (NH₄⁺-N) and nitrate (NO₃^--N) concentrations, soil bacterial community composition, weight and carbon and N concentrations, and total δ¹⁵N of above and below ground carrot biomass were determined. Results indicate that there are genetic differences in the ability of carrots to promote priming under N limited conditions, which could be exploited to enhance NUE in carrots. Soil microbial communities differed between genotypes, indicating that some of these microbes could play a role in the differential N scavenging responses observed, and/or contribute to other important functions such as resistance to pests. Endophytic microbes residing inside carrot taproots also have potential to contribute to NUE and other benefits, but are notoriously difficult to isolate and culture. New next generation sequencing technologies have revolutionized the study of microbiomes, though using these tools to study bacterial endophytes in plants is still difficult due to co-amplification of plant organelles. Consequently, a second study was conducted to determine if subjecting carrot tissues to hollow fiber microfiltration followed by enzymatic digestion could enhance recovery and amplification of bacterial endophytes. Carrot taproot digests were subject to amplification using a standard V3-V4 16S primer set, as well as two alternative (blocking and mismatch) primer sets that have prevented amplification of plastids/mitochondria in other plant species. Results indicate that the microfiltration/digestion procedure can increase the number of bacterial endophyte OTUs assigned and could be further optimized for use in carrots. The blocking and mismatch primer sets were not as effective in blocking co-amplification of plant products as they are in other studies, possibly due to the presence of a high number of chromoplasts in carrot tissues. Taxonomic assignment of bacterial endophytes differed significantly between the primer sets, indicating that multiple primer sets may be needed to fully characterize these communities in carrots. The enzymatic digestion procedure could artificially inflate certain taxa, which could be helpful if targeting specific taxa. These studies demonstrate that carrots are intimately connected with microbes residing in the soil and within their taproots, and further exploration of these plant-soil-microbial relationships could enhance the yield and sustainability of carrot production systems.</p>

This diploma thesis deals with the theme of horticultural therapy in the Czech Republic. The thesis is especially focused on the utilization of this therapy with seniors. The theoretical part contains chapters dealing with age, needs, and horticultural therapy, which is an effective way of meeting the needs of the elderly. The horticultural therapy is presented from the historical point of view. In addition the state of the horticultural therapy in Czech Republic is described in general. Furthermore this chapter describes the usage of the horticultural therapy abroad. Key features of the horticultural therapy are presented in order to ensure effectiveness of this method. Therapeutic gardens are defined in this part, as well as key differences between horticultural therapy and other generally used therapeutic approaches. The research is based on semi-structured interviews with relevant persons in the Czech Republic. The interviews were conducted with three groups of people. The first group consists from individuals who are mainly oriented in the theoretical level of horticultural therapy. For example they have an overview of the state of horticultural therapy in the Czech Republic, especially in the realization of horticultural therapy or legislative issues. The second group are those who practice...

Trädgårdsterapi är en behandlingsmetod där deltagarna genomgår ett program baserat på upplevelser och arbete i en terapeutisk trädgård med stöd av ett multidisciplinärt team med syftet att behandla olika sjukdomstillstånd. I Sverige tillämpas trädgårdsterapi främst vid vård av psykisk ohälsa som depression, utmattningssyndrom och schizofreni.  Syftet med detta arbete var att undersöka vilken effekt trädgårdsterapi har visats ha vid olika sjukdomstillstånd. Därför genomfördes en litteraturöversikt med systematisk ansats. Sökningar utfördes i databaserna PubMed, APA Psychinfo samt Swemed+ vilket resulterade i tio experimentella studier. Dessa har kvalitetsgranskats och deras resultat har bedömts och sammanställts. Studierna undersöker: cancer i palliativ vård, schizofreni, demens, stroke, smärta, depression och utmattningssyndrom samt hjärt- och kärlsjukdomar. Många av studierna har metodologiska problem som sänker deras kvalitet och bevisvärde.  Det finns inget stöd för att trädgårdsterapi skulle kunna användas för att öka livskvaliteten i palliativ vård för patienter med cancer. Det har inte heller visats fungera bättre än konventionell behandling vid stroke-rehabilitering eller för att förbättra stämningsläget hos personer med demens. Däremot har trädgårdsterapi visats ha gynnsamma effekter på symptomen vid schizofreni, depression och långvarig smärta samt bidra till rehabilitering av depression och utmattningssyndrom. De positiva effekterna på flera av sjukdomstillstånden visar att behandlingen kan ha potential att öka hälsa och lindra sjukdom. Detta kan motivera till ytterligare studier och en fortsatt utveckling av trädgårdsterapin. / Horticultural Therapy is an activity where the participants are working in and experiencing a therapeutic garden with the support of a multidisciplinary team with the aim to treat various illnesses. In Sweden the method is mainly used to treat mental health problems such as depression, fatigue and schizophrenia. The objective of this paper was to examine the effects of horticultural therapy on different illnesses. To reach the objective a review with a systematic approach was performed. A key word search was made in the databases PubMed, APA Psychinfo and Swemed+ which resulted in ten experimental studies that has been used for analyses in this paper. The quality of the studies has been examined and the results have been evaluated and compiled. The included publications examine palliative care, schizophrenia, dementia, stroke, pain, depression, fatigue and cardiopulmonary diseases. Several of the studies have methodological shortcomings which limits their quality and evidential value.  There is no evidence that horticultural therapy could be used to improve the quality of life in cancer patients in palliative care. Neither has it been shown to perform better than conventional treatments in the rehabilitation of stroke or to improve the mood of persons with dementia.  However, horticultural therapy had significant positive effects on the symptoms of schizophrenia, depression and chronic pain and contributed to the rehabilitation of depression and fatigue. The positive effects indicate that horticultural therapy could potentially contribute to promoting health and treating disease. This could motivate further studies and a continued development of the treatment.

<p>Nitrogen (N) is one of the major nutrient elements that affects growth, development, and quality of floriculture crops. Both sub-optimal and supra-optimal levels of N can negatively affect crop growth. In addition, over- fertilization may cause run-off and leaching of the N fertilizer leading to environmental pollution. Therefore, it is crucial to maintain optimal N level in plant tissue to produce good quality crops and increase productivity. This requires regular monitoring and measurement of plant N status. Laboratory analysis, the only direct method available to measure tissue N content, is destructive of plant tissue and expensive. Other available indirect methods are laborious, expensive, and/ or less reliable. In addition to measuring plant N status, it is crucial to understand acclimation responses at biochemical, leaf, and whole-plant levels in floriculture crops to N-deficit conditions. This will aid in developing a mechanistic model of plant responses to sub-optimal levels of N, proper fertilizer guidelines during production, and screening tools for identifying new varieties with tolerance to low-N level in the root zone. Unfortunately, there is limited research on floriculture crops that is simultaneously focused on plant responses at different scales to N-deficit conditions. The objectives of this research were to (i) assess the feasibility of image-based reflectance ratios for estimating tissue N content in poinsettia (Expt. 1), (ii) develop an affordable, remote sensor that can accurately and non-destructively estimate tissue N <a>content</a> in poinsettia (Expt. 2), (iii) study the physiological acclimation at whole-plant, leaf, and biochemical scales in poinsettia cultivars to N-deficit conditions (Expt. 3).</p> <p>In Expt. 1, we compared several spectral ratios based on the ratio of reflectance of near infrared <i>(R₈₇₀)</i> to reflectance of blue (<i>R</i><i>₈₇₀/R₄₅₀</i>), green (<i>R₈₇₀/R₅₂₁</i>), yellow (<i>R₈₇₀/R₅₉₃</i>), red (<i>R₈₇₀/R₆₂₅</i>), hyper-red (<i>R₈₇₀/R₆₆₀</i>), and far-red(<i>R₈₇₀/R₇₃₀</i>) wavelengths from plants<i></i>to measure whole-plant tissue N content in<i></i>four cultivars of poinsettia (<i>Euphorbia pulcherrima</i>) using a multispectral image station. Results indicated the reflectance ratio <i>R₈₇₀/R₆₂₅</i> was most suitable for assessing tissue N content in plants. In Expt. 2, a low-cost remote sensor was developed based on the findings of Expt. 1 that captured red and near-infrared images of plants, from which a reflectance ratio (<i>R_ratio</i>) was developed. The ratio was linearly related to tissue N content in all poinsettia cultivars. Furthermore, <i>R_ratio</i>was found to be more specific to N than to other elements in the tissue and related to the chlorophyll concentration of the plant. In Expt. 3, poinsettia cultivars ‘Jubilee Red’ (‘JR’) and ‘Peterstar Red’ (‘PSR’) displayed different acclimation strategies for physiology and growth under N-deficit conditions. Significantly higher growth was observed in ‘JR’ than in ‘PSR’ in the sub-optimal treatment, which indicates that ‘JR’ is more tolerant to N stress compared to ‘PSR’. Further analyses indicated that N uptake was higher in ‘JR’ than in ‘PSR’ under N-deficit conditions, without any changes in root morphology or growth. This is possible when higher levels of energy are available to transport nitrate and/or ammonia from the substrate into the root cells. Supporting this, significantly higher photosynthesis and carboxylation efficiency were observed in ‘JR’ than ‘PSR’ under N-deficit condition. These results shows that higher growth of ‘JR’ than ‘PSR’ under N-deficit conditions was likely due to increased N uptake (likely due to increased energy-driven transporter activity), which increased tissue N and chlorophyll levels. Further, these increases resulted in higher carboxylation efficiency and photosynthesis by ‘JR’ than ‘PSR’. Increased carbohydrate synthesis supported leaf growth and provided required energy in the fine root cells for N uptake from the substrate.</p>

Thesis (M.Sc. (Horticulture)) --University of Limpopo, 2007 / Bush tea (Athrixia phylicoides DC) has been used for many years by the people of South Africa for medicinal purposes. The herbs was only harvested from the wild, therefore data on the effects of mineral nutrition on total antioxidant activity had not been established. The objective of this study was to determine the seasonal effect of nitrogen (N), phosphorus (P) and potassium (K) nutrition on total antioxidant activity (TAA) in cultivated bush tea leaves. Treatments consisted of 0, 100, 200, 300, 400 or 500 kgha-1 N, P or K in a randomized complete block design with four replications under 50 % shade nets. Three (N, P and K) parallel trials were conducted per season (autumn, winter, spring and summer). TAA was determined using 2,2-diphenyl-1-picrylhydrazyl-hydrate (DPPH) method and analyzed in a spectrophotometer. Results of this study demonstrated that regardless of season, the application of N, P and K fertilizers increased quadratically levels of TAA in bush tea with most of the increase occurring between 0 and 300 N, 300 P and 200 K kgha-1. Therefore, for improved total antioxidant content in bush tea leaves, 300 N, 300 P and 200 K kgha-1 N are recommended. / National Research Foundation (NRF), Agricultural Research Council(ARC-LNR)