Made available in DSpace on 2014-06-11T19:31:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-10-23Bitstream added on 2014-06-13T20:22:28Z : No. of bitstreams: 1 ferraz_mv_dr_botfca.pdf: 840655 bytes, checksum: b0d5852179ca8a48bd111ba5ccc663f0 (MD5) / Universidade Estadual Paulista (UNESP) / A demanda atual de plantas ornamentais e flores no Brasil ainda é muito baixa quando comparada aos valores consumidos em países do primeiro mundo. Enquanto um brasileiro gasta em média US$ 6,00/ano, um norueguês consome US$ 143,00/ano. O mercado de plantas ornamentais e flores no país vêm crescendo muito nos últimos anos. Para verificar o potencial de uso de recipientes biodegradáveis um experimento foi conduzido na área experimental do Departamento de Recursos Naturais/Ciências Florestais na Fazenda Experimental Lageado da Faculdade de Ciências Agronômicas da UNESP de Botucatu-SP. O experimento teve início em 09/08/04 e término no 22/09/04. Segundo os dados da estação metereológica da UNESP de Botucatu, SP, os meses de agosto e setembro apresentaram em ambiente externo temperatura mínima de 13,18ºC a 17,00ºC; temperatura máxima de 25,01ºC a 29,86ºC; temperatura média de 17,6ºC a 21,84ºC e umidade relativa de 45,38% a 46,53%, respectivamente. Inicialmente o experimento foi conduzido no interior de estufa (A) com controle de umidade relativa, que era coberta com tela de sombreamento de 50%. Para registro da temperatura no interior da estufa (A), foi usado termômetro de máxima e mínima do tipo capela (plástico). A estufa (B) tinha um agrofilme transparente de 150 micra para proteção das mudas, não havendo controle de temperatura e umidade relativa, foram utilizados termômetro de máxima e mínima do tipo capela (plástico) e higrômetro de leitura direta (plástico). Os recipientes usados para formação das mudas foram saquinhos plásticos de polietileno na cor preta (tradicionais) e tubetes biodegradáveis. Os saquinhos plásticos tinham 0,60 micra de espessura, nas dimensões de 10,00 cm de comprimento, 5,00 cm de diâmetro, correspondendo a 196,25 cm3 de volume sendo a parte interna completamente lisa... / The current demand of ornamental plants and flowers in Brazil is still very low when it is compared with the consumed values of development. While one Brazilian spends US$ 6,00 per year, one Norwegian consumes US$ 143,00. The market of ornamental plants and flowers in the country have been growing a lot in recent years. To verify the potencial of biodegradable containers an experiment was lead in the experimental area of the Department of Forest Sciences in Lageado Experimental Farm of the Agronomic Science College of UNESP in Botucatu-SP. The experiment have started in 09/08/04 and ended in 22/09/04. According to the metereológical station of the UNESP of Botucatu, SP, the months of August and September had presented in external environment minimum temperature of 13,18ºC to 17,00ºC; maximum temperature of 25,01ºC to 29,86ºC; average temperature of 17,6ºC to 21,84ºC and relative humidity of 45,38% to 46,53%, respectively. Initially the experiment was lead inner a greenhouse (A), that was covered with screen of shadow of 50%. For register of the temperature in the interior of the greenhouse (A), with 5 control of relative humidity, it was used thermometer of maximum and minimum of the type chapel (plastic) The greenhouse (B) had one agrofilm transparent of 150 micra for protection of the seedlings, not having temperature control and relative humidity, thermometer of maximum and minimum of the type chapel (plastic) and higrômeter of direct reading had been used (plastic).The containers used for the growth of the plants were small black bags of polyethylene (traditional ones) and biodegradable containers. The small black bags had 0,60 micra of thickness, in the dimensions of 10,0 cm of length and 5,0 cm of diameter, with a 196,25 cm3 volume, smooth in the internal wall... (Complete abstract, click electronic access below)

Made available in DSpace on 2014-06-11T19:30:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-01-20Bitstream added on 2014-06-13T19:00:13Z : No. of bitstreams: 1 silva_gs_me_botfca.pdf: 632349 bytes, checksum: 498e1b397bf6abc7096a3228b6ca7ca0 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O processo limitante na produção de mudas de algumas palmeiras é a germinação, pois, suas sementes perdem a viabilidade rapidamente depois de colhidas. Essa pesquisa teve como objetivo avaliar o armazenamento de plântulas de Euterpe edulis em câmara fria a 100C (0, 3, 6 e 9 meses), em diferentes estádios de desenvolvimento (de zero a dez semanas do início do processo germinativo), visando a obtenção de plântulas ao longo do ano. Foram coletadas amostras de cada tratamento para a determinação da atividade da peroxidase, envolvida no germinação de sementes, desenvolvimento de plântulas e também, ligadas ao estresse e senescência, possibilitando avaliar os efeitos na fisiologia das sementes provocados pelos tratamentos. Foi observado o desenvolvimento vegetativo das sementes e/ou plântulas após os tratamentos em condições de casa de vegetação, por período de 6 meses, para determinar a taxa de sucesso (plântulas com desenvolvimento normal). A taxa de sucesso de plântulas foi afetada negativamente pela permanência das sementes/plântulas em câmara de germinação e armazenamento em câmara fria. Dos parâmetros morfológicos de desenvolvimento analisados no final do experimento (comprimento de parte aérea, comprimento de parte aérea total, comprimento de raiz, diâmetro do coleto, massa de matéria fresca e massa de matéria seca), somente ocorreu diminuição do comprimento da raiz, sob estas condições. A atividade da peroxidase aumentou em decorrência do aumento do período de armazenamento em câmara fria, relacionada com a senescência das plântulas. Apesar da redução da taxa de sucesso das plântulas, não ocorreu redução dos parâmetros de desenvolvimento vegetativo (exceto comprimento de raiz) analisados das sementes/plântulas, portanto, o armazenamento em câmara fria é um instrumento viável para prolongar o período de uso das sementes de Euterpe... / Germination is the limiting process in the seedling production of some palm trees, since their seeds lose viability rapidly after collection. This study aimed to evaluate the storage of Euterpe edulis seedlings in a cold chamber at 10ºC (0, 3, 6 and 9 months) at different developmental stages (from zero to ten weeks after the initiation of the germinative process) in order to obtain seedlings throughout the year. Samples from each treatment were collected for assay of peroxidase activity, involved in seed germination, seedling development and also related to stress and senescence, which allows evaluating the treatment effect on seed physiology. The vegetative development of seeds and/or seedlings was observed under greenhouse conditions for six months to determine the success rate (seedlings presenting normal development). The success rate of seedlings was negatively affected by the maintenance of seeds/seedlings in germination chamber and storage in cold chamber. Among the morphological traits of development analyzed at the end of the experiment (shoot length, total shoot length, root length, stem diameter, fresh matter and dry matter), only root length decreased under such conditions. Peroxidase activity increased due to the longer period of storage in cold chamber, which was related to the senescence of seedlings. Despite the reduction in the success rate of seedlings, there was no decrease of vegetative developmental traits (except root length) analyzed in seeds/seedlings. Therefore, the storage in cold chamber is a viable instrument to extend the use of seeds for propagation of Euterpe edulis

Orientador: Ricardo Ribeiro Rodrigues / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-04T19:36:42Z (GMT). No. of bitstreams: 1 Viani_RicardoAugustoGorne_M.pdf: 2276190 bytes, checksum: 011893720115e5dc7fd5216c130b3bae (MD5) Previous issue date: 2005 / Resumo: As plântulas são fundamentais para a manutenção das populações arbustivo-arbóreas. Em regiões tropicais estão normalmente representadas por um elevado número de espécies e indivíduos, ocorrendo não apenas em formações florestais nativas, mas também em sistemas florestais, cujas práticas de manejo possibilitam sua presença, como cultivos de Eucalyptus spp.. Por outro lado, reflorestamentos com espécies nativas voltados a restauração ecológica, muitas vezes contam com poucas espécies e não atendem a critérios mínimos de diversidade, dentre outros aspectos, pela baixa disponibilidade de espécies nos viveiros de produção de mudas. Assim, o objetivo geral desse trabalho foi avaliar o potencial de uso da regeneração natural (plântulas arbustivo-arbóreas = 30cm de altura) de remanescente de Floresta Estacional Semidecidual e de talhões de Eucalyptus spp, localizados em Bofete-SP, como estratégia de produção de mudas de espécies nativas e resgate da diversidade vegetal na restauração ecológica. No Capítulo 1, a avaliação da comunidade de plântulas na borda e no interior de remanescente florestal (10 parcelas de 4x4m em cada ambiente), indicou elevada diversidade. Além disto, as plântulas mostraram uma distribuição espacial agregada para a comunidade e para as principais espécies e uma correlação negativa entre densidade de indivíduos e altura. No interior e borda do remanescente foram encontradas, respectivamente, 118 espécies (243.625±142.945 indivíduos.ha-1) e 81 espécies (139.750±90.307 indivíduos.ha-1). Ambas as áreas contaram com várias espécies que são pouco comuns ou não utilizadas nos plantios de restauração ecológica. No Capítulo 2, o acompanhamento em remanescente florestal, de 80 parcelas (20 parcelas de 2x2m por tratamento) submetidas a diferentes tratamentos de retirada das plântulas (100% de retirada com e sem revolvimento posterior do solo, 50% de retirada sem revolvimento posterior do solo e testemunha sem retirada de plântulas), constatou uma marcada sazonalidade no recrutamento. Além disso, o revolvimento do solo não se mostrou como prática incrementadora da regeneração natural, provavelmente em função da cobertura vegetal da floresta estudada. Apesar das áreas submetidas à retirada de plântulas terem se mostrado capazes de auto-recuperação no tempo, o curto período de acompanhamento e a ocorrência de elevados níveis de recrutamento de pelo menos uma espécie (Protium spruceanum), dificultam a compreensão dos reais efeitos desta prática sobre a dinâmica de regeneração da floresta e demonstram a necessidade de novos estudos. No Capítulo 3, a avaliação da comunidade de plântulas (87 parcelas de 2x2m) sob plantios de Eucalyptus spp. encontrou 42 espécies e densidade média de 8.046 (± 2.295) indivíduos.ha-1, porém, com grande variação no número de indivíduos e espécies entre os talhões analisados. Em geral talhões com maior riqueza de espécies e densidade de regeneração natural (= 1,5m) foram também mais ricos e densos na comunidade de plântulas. No Capítulo 4 foi avaliada a sobrevivência em viveiro de plântulas transferidas do remanescente florestal (2.424 indivíduos, 110 espécies) e dos talhões de Eucalyptus spp. (280 indivíduos, 42 espécies). As taxas de sobrevivência foram respectivamente 69% e 66,8%, com grande variação entre as espécies; no entanto espécies pioneiras apresentaram taxa de sobrevivência significativamente maior que as não pioneiras. Muitas das espécies sobreviventes em viveiro não são encontradas nos viveiros florestais e certamente também estão ausentes nos plantios de restauração de áreas degradadas. Portanto, o aproveitamento da regeneração natural das áreas estudadas é uma estratégia complementar e viável de produção de mudas de espécies nativas, elevando a diversidade dos viveiros florestais. Sob os plantios florestais (áreas agrícolas, não protegidas pela legislação ambiental) o método pode ser utilizado, focado principalmente nas espécies que apresentam alta densidade na área, ou nas pouco comuns nos viveiros e plantios de restauração ecológica. Entretanto, em áreas naturais recomenda-se que a princípio este método seja executado apenas em situações que irreversivelmente envolverão a supressão da vegetação nativa, tais como autorizações para construção de estradas e hidrelétricas, atividades mineradoras, etc / Abstract: Seedlings are essential to the maintenance of shrubs and trees populations in tropical forests. They are usually represented by a high number of species and individuals; they occur not only in native forest formations, but also in forest systems whose management allows its presence possible, such as Eucalyptus spp. plantations. Generally, ecological restoration with native species usually does not reach the minimal diversity that is necessary. The low availability of native species in the nurseries seems to be one of the causes of this situation. This study evaluated the potential of natural regeneration (shrubs and trees seedlings with height = 30cm) of a Seasonal Semideciduous Forest fragment and Eucalyptus spp. plantations located in Bofete-SP, to produce seedlings of native species, as a strategy to rescue the plant diversity in the ecological restoration programs. In Chapter 1, the evaluation of the seedling community in the edge and interior of the forest fragment (10 plots of 4x4m in each environment) found high plant diversity. Moreover, the seedlings showed an aggregated spatial distribution in the community level and to the main species. A negative correlation between density of individuals and height were observed. In the interior and edge were found 118 species (243625±142945 indiviuals.ha-1) and 81 species (139750±90307 individuals.ha-1) respectively. In both areas, some species which are rarely found or absent in ecological restoration plantations were recorded. In Chapter 2, the monitoring in the forest fragment of permanent plots (2x2m) submitted to different treatments of removing seedlings (100% of seedlings removal, previously to soil revolving; 100% of seedlings removal and no soil revolving; 50% of seedlings removal without soil revolving, and control plots) revealed a strong seasonality on the recruitment process. Moreover, the soil revolving did not promote an improvement of the natural regeneration, probably due to the high level of forest covering in the studied area. Despite the capacity of areas to self-recuperate after removal of seedlings, the short monitoring time and the occurrence of high levels of recruitment to one species at least (Protium spruceanum), has brought difficulties to the understanding of the real effects of this practice on the dynamics of the forest regeneration, showing the necessity for new studies. In Chapter 3, the evaluation of the seedling community (87 plots of 2x2m) in Eucalyptus spp. plantations found 42 species and an average density of 8046 (± 2295 indivíduals.ha-1), but with a great variation in the numbers of individuals and species between the sites analyzed. Sites with higher density and species richness in the natural regeneration stratum (height = 1.5m) showed higher density and species richness in the seedling community either. In Chapter 4 the survivorship in the nursery of seedlings transplanted from the forest fragment (2424 individuals, 110 species) and Eucalyptus spp. plantations (280 individuals, 42 species) was evaluated. Seedlings survivorship (respectively 69% e 66.8%) was variable between species, however, pioneer species showed a survival rate significantly higher than non-pioneers. A lot of species that survived in the nurseries were never recorded in these places and certainly were absent in the restoration plantations of disturbed areas. Therefore, the natural regeneration could be used as a complementary and available strategy to produce seedlings of native species. In forest plantations (agricultural lands, not protected by environmental laws) this methodology could be used, mainly when focused in species with higher densities, as well as species that are less common in nurseries and have been scarcely found in ecological restoration programs. However, in natural forests, these practices should be recommended only in situations in which there were permission to build roads and hydroelectrics, mining activities, and so on, becoming an initiative to compensate the environmental impact / Mestrado / Mestre em Biologia Vegetal

Made available in DSpace on 2014-10-09T12:28:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:04Z (GMT). No. of bitstreams: 0 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Os metais são componentes da biosfera, ocorrendo naturalmente no solo e nas plantas, contudo como consequência de ações antrópicas, os seus níveis vêm se aumentado muito, dependendo da região. O cobre (Cu) e zinco (Zn) são elementos essenciais para o crescimento e desenvolvimento das plantas, mas em excesso são tóxicos. O objetivo deste trabalho foi avaliar o potencial das plantas em absorver os metais Cu e Zn e os efeitos que estes ocasionam nas plântulas cultivadas in vitro. Os resultados deste estudo poderão contribuir principalmente em pesquisas agrícolas e nas da área do meio ambiente. A planta investigada neste trabalho foi a Aechmea blanchetiana, pertence à família Bromeliaceae, e que pode ser terrestre ou epífita e é amplamente utilizada como planta ornamental. Na parte experimental, o cultivo das plântulas e a exposição das plântulas em diferentes concentrações de Cu ou Zn, foram realizados no Instituto de Botânica (IBt) de São Paulo. Após a germinação das sementes as plântulas foram transferidas para crescimento e expostas em meios de cultivo contendo diferentes concentrações de Cu ou de Zn. Após este período de cultivo in vitro, as plântulas foram analisadas por meio da morfometria, anatomia e análise por ativação com nêutrons. O controle de qualidade dos resultados da análise por ativação avaliado por meio das análises dos materiais de referência certificados mostrou boa precisão e exatidão dos dados para os diversos elementos determinados. As concentrações mais altas de Cu utilizadas na exposição da espécie foram as que causaram maiores variações estruturais nos parâmetros morfométricos e anatômicos, no entanto para o Zn não houve diferenças significativas para a maioria dos parâmetros analisados. A A. blanchetiana mostrou ser uma espécie bioacumuladora de Zn, apresentando altos valores de absorção deste elemento nas suas partes aéreas e radiculares. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP / FAPESP:08/55680-8

Made available in DSpace on 2015-04-13T12:17:32Z (GMT). No. of bitstreams: 1 Dissertacao Final Leocinira Mendes.pdf: 3023098 bytes, checksum: af83eb3ac95ef496a2e4102b8cef8476 (MD5) Previous issue date: 2008-04-14 / FAPEAM - Fundação de Amparo à Pesquisa do Estado do Amazonas / Clarisia racemosa Ruiz et Pavon (guariúba) of the family Moraceae, is a native tree in the Amazon region which is used commercially as timber in the local market and also for exportation. The seeds of guariúba are recalcitrant and germinate immediately after they are dispersed or collected, this way, the identification of the substrate most adequate for germination and production of seedlings is made with quality is important. The objective of this study was to avaliate the influence of different substrates in the germination and production of seedlings of guariúba in two cultivative environments. The experiment was conducted in a nursery and inside a asa de vegetação (house of vegetation) of the Faculty of Agrarian Sciences of the Federal University of Amazonas UFAM. The seeds were extracted manually form matured fruits sown in flowerbeds covered with a 50% sombrite screen. The substrates tested for the germination of seeds were washed sand, a medium granulometria vermiculite , sawdust, sawdust + sand (1:1) and humus ( 0 - 20 cm layer of forest soil). A delineamento experitental inteiramente casualizado (DIC) (experimental delineation completely casualized) with five treatments and four repetitions of 25 seeds was used. The criterion for germination was the emergence of the caulicle above the substrate, considering normal, the plantule with total coverage of the eofilo . The avaliations were made on daily basis considering the average time for germination in days (TM), the percentage of germination (% G) and the index of velocity of emergence (IVE). The items used were subsoil + sand 3:1 (T+Ar), subsoil + sand + cowdung 3:1:1 (Ts+Ar+Eg), subsoil + sand + cowdung + organic compost 3:1:0,5:0,5 (Ts+Ar+Eg+Co), subsoil + sand + organic compost 3:1:1 (Ts+Ar+Co) and one fraction forest soil (Sf), in a completely casualized delineament (DIC), with five treatments and three repetitions, with three plants in a factorial scheme, with two environmental factors (nursery and house of vegetation) and five compositions of substrates. The growth analyses avaliated within the periods of 30, 60, 90 and 120 days after the transplanting were height (ALT altura ), neck diameter (DC diametro de colo ), number of leaves (NF número de folhas ), and at 120 days also, a destructive collection was made in order to obtain of leaf area (AF) the weight of dry material of the airy part (PMSPA), weight of dry material of the radicular system (PSR), the relation airy part/ radicular system (RPAR). The fruits presented in medium, length of 33,29 mm and weight of 6,712 g. The seeds presented length of 24,61mm and weight of 2,83g. The results of the analyses of the variables studied for the germination did not present significant differences between the substrates tested with average germination of 90% starting from the 30th day and ending on the 45th day after planting. The substrates, forest soil, subsoil + sand + cowdung and subsoil +sand + cowdung + organic compost proportioned the best growths in all the variables, with the exception of the relation PMSPA/PSR. The nutrient teors on the leaves followed the decreasing order of N>K>Ca>Mg>P. The environment, house of vegetation, proportioned the best results in all the variables compared to the nursery with the exception of the RPAR. / Clarisia racemosa Ruiz et Pavon (guariúba), Moraceae, é uma árvore nativa da região Amazônica, de valor madeireiro no mercado local e para a exportação. As sementes de guariúba são recalcitrantes e germinam logo após a dispersão ou coleta. Dessa forma a identificação do substrato mais adequado para a germinação e produção de mudas com qualidade é importante. O objetivo desse estudo foi avaliar a influência de diferentes substratos na germinação de sementes e produção de mudas de guariúba. O experimento foi conduzido em viveiro e dentro da casa de vegetação da Faculdade de Ciências Agrárias da Universidade Federal do Amazonas UFAM. Os substratos testados para a germinação de sementes foram: areia lavada, vermiculita de granulometria média, serragem, serragem+areia (1:1) e terriço (camada de 0 a 20 cm de solo de floresta), foi utilizado o delineamento experimental inteiramente casualizado (DIC) com cinco tratamentos e quatro repetições de 25 sementes. O critério de germinação foi a emergência do caulículo acima do substrato, sendo considerado plântula normal aquela com total abertura do eofilo. As avaliações foram feitas diariamente, considerando o tempo médio da germinação em dias (TM), a porcentagem de germinação (%G) e o índice de velocidade de emergência (IVE). Os substratos testados para produção de mudas foram terra de subsolo+areia (T1); terra de subsolo+areia+esterco de gado (T2); terra de subsolo+areia+esterco de gado+composto orgânico (T3); terra de subsolo+areia+composto orgânico (T4) e solo de floresta (T5). Foi utilizado o delineamento inteiramente casualizado com três repetições (recipientes plásticos) e três plantas por repetição, num esquema fatorial 2 x 5 representado pelos ambientes (casa de vegetação e viveiro) e tipo de substrato. As análises de crescimento avaliadas nos períodos de 30, 60, 90 e 120 dias após o transplantio foram: altura (ALT), diâmetro de colo (DC), número de folhas (NF) e aos 120 dias foi realizada a coleta destrutiva para obtenção de área foliar (AF), peso da matéria seca da parte aérea (PMSPA), peso da matéria seca do sistema radicular (PSR), relação parte aérea / sistema radicular (RPAR), as características químicas e teor de nutrientes foliar. Os frutos de guariúba apresentaram em média o comprimento de 33,29 mm e o peso de 6,712 g. As sementes de guariúba apresentaram em média o comprimento de 24,61 mm, o peso de 2,83 g, número de sementes por kg de 409,80 e teor de água de 42,10% com germinação média de 90% em todos os substratos sem tratamento pré-germinativo, com início aos 30 dias e final aos 45 dias após a semeadura. Os resultados das análises das variáveis estudadas para germinação não apresentaram diferenças significativas entre os substratos. Aos 120 os substratos solo de floresta, terra de subsolo+areia+esterco de gado+composto orgânico e terra de subsolo+areia+esterco de gado proporcionaram os melhores crescimentos em todas as variáveis, exceto na relação PMSPA/PSR. O teor de nutrientes nas folhas seguiu a ordem decrescente de N>K>Ca>Mg>P. O ambiente casa de vegetação proporcionou os melhores resultados em todas as variáveis em relação ao viveiro com exceção da RPAR.

>Magister Scientiae - MSc / With a decrease in water availability and arable land, and the ever-increasing reports of toxic chemical pollutants, it is crucial to elucidate plants’ mechanisms of adaptability to these abiotic stressors. South Africa alone accounts for approximately 30% of global Zirconium (Zr) production. However, reports on Zr-induced stress in plants are sparse. Increased mining activity leads to soil contamination which subsequently has harmful effects on crop plants. Under normal conditions B. rapa crop plants flourish, they are rapid in their cycling and circumvent the seed dormancy stage which enables them to have high yields over relatively short periods. However, when unfavourable conditions arise, such as exposure to toxic chemicals and metal ions like Zirconium, the development and growth of B. rapa L., much like other crop plants is affected. More specifically, the damaging effects of Zr is not only attributed directly; as with substitutions of biometals [like Iron (Fe)] in various biomolecules rendering them inactive, but more as a consequence of the production of toxic molecules such as reactive oxygen species (ROS) and methylglyoxal (MG). ROS such as superoxide anion (O₂⁻) and hydrogen peroxide (H₂O₂ ) are known to have signalling roles in plants with reports on their involvement in alleviating seed dormancy and seedling development. However, the signalling roles of MG are not known with regards to plant cells and have been reported more so in animal cells; playing vital roles in fat signalling in diseases such as diabetes. Furthermore MG, in plant and animal cells, directly converts oxygen (O₂) to O₂⁻ and thus increases the cell’s oxidative imbalance, leading to cell damage if O₂⁻ is not rapidly dismutated to H₂O₂ and H₂O by superoxide dismutase (SOD). In turn, H₂O₂ is more stable than O₂⁻ and consequently is more toxic to cells over time. Therefore, H O must be removed as well by a collection of enzymes, such as ascorbate peroxidase (APX) and catalases (CAT). In this study, possible stress-signalling of MG in seedlings under normal conditions and Zr-stress were investigated to establish whether MG at a low dose (6 μM) would benefit seedling growth and development, via a proposed preinduction of the B. rapa L. antioxidant system. Therefore, it was proposed that ROS accumulation due to the exogenous application of MG, would incite the activation of antioxidants and thus mitigate the effects of Zr stress. Physiological tests to determine dry weights (figure 3.2.3) and germination percentage (figure 3.2.2) revealed that MG-treated seedlings yielded an improved biomass and early development compared to Zr-treated seedlings and the control. Membrane damage as assessed by lipid peroxidation viz. Malondialdehyde [MDA] (figure 3.2.4) and conjugated dienes [CD] (figure 3.2.5) also indicated less damage in MG-treated seedlings compared to the Zr-treated set. The chlorophyll content observed was prominent (table 3.1). MG-treated seedlings exhibited a 40% and 15.5% increase compared to Zr-treated seedlings and the control respectively. Moreover cell viability had improved in MG-treated seedlings compared to the control, and in MG+Zr-treated seedlings only a slight increase in cell death occurred despite Zr being present. O₂⁻, H₂O₂ and •OH (figure 4.2.1 – 4.2.3) were investigated in B. rapa L. seedlings in response to Zr and MG by spectrophotometric biochemical assays, as well as their scavenging enzymes, MG accumulation and Gly-I activity. Furthermore, BrGLY1 gene expression and Zr-uptake by ICP-OES were performed. Seedlings treated with MG and Zr respectively showed an increase in ROS. However, all of the ROS observed in MG+Zr-treated seedlings were markedly lower compared to Zr-treated seedlings. SOD and CAT activity observed in MG+Zr-treated seedlings had decreased compared to Zr-treated seedlings, whereas APX activity had increased. Gly-I activity and BrGlyI gene expression had increased across all treatments, showing an elicited response to oxidative stress, due to the observed upregulation, as a result of the accumulated MG. The observed Zr-uptake in MG+Zr-treated seedlings was inhibited by 5-fold compared to Zr-treated seedlings. Clear signs of stress were evident in seedlings treated with Zr compared to the control and MG- treated seedlings, the MG-supplemented (MG and MG+Zr) seedlings displayed a vast improvement comparatively. Modulation of antioxidant activity observed in this study is indicative of an incited response to oxidative stress (figure 4.2.4 – 4.2.6). MG revealed distinct involvement in stress-signalling, ROS levels had increased, although not as severely as with Zr-treated seedlings, but seemingly enough to activate antioxidants without eliciting damage. Furthermore, the proposed early-onset activation of antioxidants has been observed in B. rapa L. seedlings of this study, and as such has resulted in improved growth, development and seed germination. The results of this study has therefore negated the previous reports on MG-toxicity (at high concentrations), and has shed light on further properties of this ubiquitous and inevitably-occurring metabolite at low levels. / National Research Foundation (NRF)

>Magister Scientiae - MSc / Riparian vegetation occurs in two distinct zones, the wet bank and the dry bank. Knowledge on how the flow regime influences the zonal structure of riparian vegetation is required to mitigate the adverse effects of water resource utilization on riparian vegetation. The first objective of this study was to determine whether flow exerts a physical influence on zonal structure pre- or post-recruitment. An examination of the survival of seedlings and saplings was conducted along Western Cape rivers to investigate seedling persistence and survival on lateral zones. A comparison of the ratios of seedlings, saplings and adults in different riparian zones for the years, 2004, 2011 and 2013, was carried out. The results suggest that in general seeds are deposited randomly on the banks, where they germinate and become seedlings. Seedlings that become established at locations unsuitable for their persistence into adulthood are removed either by high flows or perish during dry conditions. Thus, lateral zonation eventually develops due to species differences in tolerance to conditions at different positions on the banks. The second objective was to explore the effects of the reduction in dry season low flows on the recruitment success of riparian species at sites upstream and downstream of abstraction points. At most sites plants were arranged into different lateral zones and the numbers of species between upstream and downstream sites were not significantly different. There were significant differences in the abundances between up- and downstream sites, with the loss of herbaceous plants and sedges at downstream sites, both of which favour moist conditions. Also, in the absence of dry season flows, the seedlings of dry bank tree species recruited closer to the channel than those at the sites with summer flows. The shifting of the dry bank into the channel narrows the channel, which may affect the hydraulic pressures exerted during floods. The spatial arrangement in the riparian zone has as much to do with flow conditions post recruitment as it does with conditions during recruitment. This shows that the structure of riparian plants is determined not only by whether or not the minimum flows are met, this points to the need to reinstate the naturally variable flow and adopting a holistic approach for the understanding and management of aquatic systems.

Please read the abstract in the dissertation / Dissertation (MSc (Agric))--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted

Phenylketonuria and hyperphenylalanemia are autosomal recessive inborn errors of phenylalanine metabolism that are caused by mutations in the phenylalanine hydroxylase gene. Due to the stringency of the present dietary therapy, alternative treatments are being studied. Phenylalanine ammonia-lyase (PAL) is one of the potential dietary supplements for these patients. PAL is a well-studied plant enzyme which breaks down phenylalanine into trans-cinnamic acid and ammonia (Camm and Towers, 1973). It is found in the cytoplasm of the plant cells and is naturally encapsulated by plant cell walls which may protect it against the acidic pH environment in the gastrointestinal tract. It presumably degrades ingested Phe that circulates in the intestinal lumen. In this study, red spring wheat seedlings (Triticum aestivum L.) found to contain high PAL activity naturally were investigated as a potential alternative oral therapy. Specifically, the objectives were (1) to evaluate different drying methods on generating concentrated and dried preparation of wheat seedlings containing high levels of PAL activity; (2) to examine the retention of PAL activity over three months of storage under various storage conditions; (3) to determine the stability of PAL activity in simulated human digestion condition to establish if further study of using plant source enzyme in vivo is warranted. Freeze-drying (FD) was found to have retained the most activity (>90 % recovery dry wt basis) compared to air-drying (AD) and vacuum-microwave drying (VMD) for both leaf and residual seed/root samples. Pre-freezing of leaf tissues at -18 °C before FD significantly retained the highest PAL activity compared to pre-freezing at -25 °C, -35 °C, and -80 °C (P<0.05). Over three months of storage, 60-80 % of PAL activity was recovered in leaf and —100 % was recovered in residual seed/root tissues after storage at -20 °C. After in vitro protein digestion, 36% and 42 % of PAL activity was recovered in fresh leaf and root tissues respectively; however, FD tissues were found to be susceptible to proteases and acidic environment and no activity was recovered after three hours of in vitro protein digestion. High performance liquid chromatography (HPLC) analysis of the residual Phe after in vitro protein digestion confirmed that fresh tissues had significantly higher conversion of Phe than that of FD tissues. Together, these results suggest that red spring wheat seedlings may have potential as a dietary supplement for phenylketonuric patients while further study to enhance PAL activity in plant preparations is required. / Land and Food Systems, Faculty of / Graduate

Subtropical Thicket is the dominant vegetation biome in the Eastern Cape. Little regeneration through seedlings has been observed in Thicket. This is of serious concern, as Thicket has been degraded over large areas of its distribution. An understanding of the seed dynamics is necessary for any restoration project. A number of possible causes for the lack of seedlings were therefore investigated. Study sites were best classified according to the biogeographical regions of the Subtropical Thicket Ecosystem Planning (STEP) project. The seed bank of Thicket is dissimilar to the aboveground vegetation, as it lacks woody species and is dominated by herbs and grasses, making little contribution to the regeneration of Thicket species. An increase in canopy cover resulted in lower soil and air temperatures, as well as light, and an increase in litter depth. Seedling abundance and species richness increases with mean annual rainfall, with woody seedlings being dominant in the higher rainfall areas, and succulent species in the lower rainfall regions. Anemochorous species dominated the germinable seed bank, and zoochorous species were more prevalent underneath the canopy, compared to open areas, an indication of active seed dispersal. No germination was recorded in many Thicket species, and dormancy mechanisms were lacking in many of the species that did germinate. Immersion in hot water increased germination in the hard seeds of Acacia karroo, whereas shade enhanced germination in small seeded Burchellia bubalina. The response of seedlings of four Thicket species with varying distribution to shade and drought was studied. Ptaeroxylon obliquum and Aloe africana are drought tolerant species, whereas Burchellia bubalina and Rhus dentata were intolerant to low soil moisture. All four species were able to grow in deep shade, although Rhus dentata would be classified as a shade avoider, unlike the other three species that are shade tolerant. This results in the four species having different regeneration niches. It was concluded that dispersal and the lack of “safe sites” for seedlings were the main limitations to seedling establishment in Mainland Thicket.