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Mecanismos de controle de tolerância à dissecação em sementes de Caesalpinia echinata LAM. (Pau-Brasil) e Caesalpinia peltophoroides BENTH. (Sibipiruna)Silva, João Paulo Naldi [UNESP] 22 February 2010 (has links) (PDF)
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silva_jpn_me_botib.pdf: 1461698 bytes, checksum: f3d2da00e4477125c12042e4a44960b3 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A aquisição da tolerância à dessecação ocorre durante a maturação da semente, após acúmulo de reservas e antes do início do processo natural de secagem, porém, com o avanço da germinação a sensibilidade a dessecação aumenta. Estresses hídricos podem induzir ou restabelecer a tolerância à dessecação em sementes, porém, não se sabe em quais processos ele atua, como na ativação de genes. O objetivo deste trabalho foi avaliar a aquisição e perda de tolerância à dessecação em sementes de Caesalpinia echinata Lam. (pau-brasil), e a possibilidade de indução deste processo avaliando as modificações nos carboidratos solúveis e de ciclitóis, nos níveis endógenos de ABA e na expressão de aquaporinas. Foram observadas diferenças na aquisição de tolerância em sementes imaturas de mesma idade, produzidas nas mesmas matrizes em 2007 e 2008, com diferentes composições de carboidratos solúveis. Sementes maduras perdem a tolerância à dessecação logo após protrusão da raiz primária, em comprimentos dependentes do grau de deterioração da semente. Sementes imaturas e maduras tolerantes de C. echinata suportaram a desidratação de formas diferentes, utilizando reservas de amido e ciclitóis, com papel da sacarose quando secas. Esses resultados foram comparados com sementes de Caesalpinia peltophoroides Benth (sibipiruna), demonstrando comportamentos fisiológicos distintos, provavelmente relacionados com o tipo de reserva que acumulam / The acquisition of desiccation tolerance occurs during seed maturation, after reserves accumulation and before the natural process of drying, however, with seed germination the desiccation sensitivity increases. Water stress can induce or restore the desiccation tolerance in seeds, but it is unclear what processes it acts, like activation of genes. The objective of this work was to evaluate the acquisition and loss of desiccation tolerance in Caesalpinia echinata Lam (brazil-wood) seeds, and the possibility to induction this process, evaluating the soluble carbohydrates and cyclitols changes, the ABA endogenous levels and expression of aquaporins. Differences were observed in the tolerance acquisition in immature seeds of the same age, produced by the same trees in 2007 and 2008, showing different compositions of soluble carbohydrates. Mature seeds lose desiccation tolerance soon after radicle protrusion in length depending on the degree of seed deterioration lot. Immature and mature tolerant seeds of C. echinata support the dehydration by different ways, using starch reserves and cyclitols, seen sucrose when the seed dry. These results were compared with seeds of Caesalpinia peltophoroides (sibipiruna), showing different physiological parameters, probably related to the type of reserves that they accumulate
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Efeito de rodas compactadoras submetidas à cargas verticais em profundidades de semeadura nas características agronômicas do milho (Zea mays L.)Silva, Rouverson Pereira da [UNESP] 18 December 2002 (has links) (PDF)
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silva_rp_dr_jabo.pdf: 1027218 bytes, checksum: 5735563bb21198339668c23b86ede607 (MD5) / Uma semeadura bem realizada é funtfamental para o sucesso de implantação de uma cultura e, as rodas compactadoras utilizadas nesta operação, devem ser capazes de melhorar o contato solo-semente para promover boa emergência das plântulas. O presente trabalho teve por objetivo estudar a influência de três modelos de roda compactadora, três profundidades de semeadura e três níveis de carga sobre a roda compactadora sobre a germinação e o desenvolvimento da cultura do milho, em uma pista de ensaios projetada para esta finalidade. O trabalho foi desenvolvido no município de Uberaba, MG, em LA TOSSOLO VERMELHO distrófico, textura média, preparado com enxada rotativa. O delineamento experimental utilizado foi o de parcelas sub-sub-divididas, com 27 tratamentos e quatro repetições. Os resultados obtidos evidenciaram que aumento da profundidade de semeadura não provocou alterações significativas no teor de água, mas provocou diminuição da temperatura do solo. A profundidade de semeadura foi o fator que mais afetou o desenvolvimento vegetativo da cultura do milho no estádio 2, enquanto que no estádio 4 nenhum dos fatores afetou as medidas de desenvolvimento da cultura. / The success of the establishment of a crop depend on several factors and the seeders press wheels should be capable to improve the contact soil-seed to promote good seed germination. The present work had as objedive to study the influence of three models of press wheel, three depths of sowing and three load levels on the press wheel on the germination and the initial and vegetative development of the culture of the corn, in a projected sowing assay lane for this purpose. The experiment was carried in the municipal district of Uberaba, State of Minas Gerais, with split split plot array, 27 treatments and four replications, used to evaluate agronomic characteristics of the corn crop. The results evidenced that the depth of sowing was the fadar that more affected the vegetative development of the culture of the maize in the stadiums 2, while that in stadium 4 did not have significant differences in the measures of development of the culture.
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Long-Term Effectiveness of Revegetation at the Tuba City, Arizona Uranium Mill Tailings Disposal SiteBenally, Quentin Y., Benally, Quentin Y. January 2016 (has links)
Revegetation is a reclamation method used to stabilize land that has been disturbed (i.e. Uranium contamination) by mining in an effort to establish a sustainable plant community. During 1986-88, large amounts of topsoil were removed at the site adjacent to the Tuba City disposal cell to remove windblown contaminated soil and construct the Uranium disposal cell. Re-establishing a sustainable plant community is critical to minimizing dust emissions, controlling erosion, and improving rangeland condition, and enhancing evapotranspiration. The objective of this study was to evaluate the long-term effectiveness of revegetation efforts by 1) comparing plant species composition and abundance on the reclaimed area and native rangeland protected from grazing, 2) current rangeland condition by comparing plant communities on grazed and protected native rangeland 3) differences in soil fertility, particle size distribution, and morphology that could be influencing vegetation differences in the three areas, 4) landscape-scale evapotranspiration rates and effects on groundwater recharge in the three plant communities, and 5) the value of using relatively undisturbed Legacy Management parcels as reference areas. Plant cover in the revegetated area was greater in 2014 (24%) than in 1998 (15%); however, plant species composition and diversity in the revegetated area and in the reference area remained markedly different. The effectiveness of revegetation is improving, but given the extended amount of time the improvement is not matching the protected area’s percent cover. The reference area showed highest cover during the early cool-season. However, the grazed area possessed the highest plant species composition and highest foliar cover in the late warm-season. The vegetation relevé estimate and foliar cover statistics show the revegetated area (24%) was significantly less than the surrounding vegetation (35%), even after 26 years since original revegetation. These results are critical in assisting Legacy Management to identify environmentally sustainable methods for the continuous management of this site and others in the area.
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Regeneration of the forest after logging at Kintap, South Kalimantan, IndonesiaJafarsidik, Yusuf January 1998 (has links)
No description available.
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Molecular phylogenetic studies of the vascular plantsRai, Hardeep Singh 05 1900 (has links)
To investigate vascular-plant phylogeny at deep levels of relationship, I collected and analyzed a large set of plastid-DNA data comprising multiple protein-coding genes and associated noncoding regions. I addressed questions relating to overall tracheophyte phylogeny, including relationships among the five living lineages of seed plants, and within two of the largest living gymnosperm clades (conifers and cycads). I also examined relationships within and among the major lineages of monilophytes (ferns and relatives), including their relationship to the remaining vascular plants. Overall, I recovered three well-supported lineages of vascular plants: lycophytes, monilophytes, and seed plants. I inferred strong support for most of the phylogenetic backbones of cycads and conifers. My results suggest that the cycad family Stangeriaceae (Stangeria and Bowenia) is not monophyletic, and that Stangeria is instead more closely related to Zamia and Ceratozamia. Within the conifers, I found Pinaceae to be the sister-group of all other conifers, and I argue that two conifer genera, Cephalotaxus and Phyllocladus (often treated as monogeneric families) should be recognized under Taxaceae and Podocarpaceae, respectively. Systematic error likely affects inference of the placement of Gnetales within seed-plant phylogeny. As a result, the question of the relationships among the five living seed-plant groups still remains largely unresolved, even though removal of the most rapidly evolving characters appears to reduce systematic error. Phylogenetic analyses that included these rapidly evolving characters often led to the misinference of the “Gnetales-sister” hypothesis (Gnetales as the sister-group of all other seed plants), especially when maximum parsimony was the inference method. Filtering of rapidly evolving characters had little effect on inference of higher-order relationships within conifers and monilophytes, and generally resulted in reduced support for backbone relationships. Within the monilophytes, I found strong support for the majority of relationships along the backbone. These were generally congruent with other recent studies. Equisetaceae and Marattiaceae may be, respectively, the sister-groups of the remaining monilophytes and of the leptosporangiate ferns, but relationships among the major monilophyte lineages are sensitive to the outgroups used, and to long branches in lycophytes. / Science, Faculty of / Botany, Department of / Graduate
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Rheological studies of non-aqueous poly methyl methacrylate dispersions stabilised using graft copolymer steric stabilisersSavage, Matthew John January 1998 (has links)
Steric stabilisers were synthesised via the copolymerisation of styrene with acrylic macromonomers. The macromonomers were prepared by end capping reactions of poly 2-ethyl hexyl acrylate (PEHA) prepolymer with vinyl containing species. Preliminary reaction routes proceeded via the use of oxalyl chloride to create an acyl chloride intermediate followed by end capping with hydroxy ethyl methacrylate. This process was found to be inefficient due to the moisture sensitivity of the acyl chloride. The second route involved the direct end capping of the PEHA pre-polymer with glycidyl methacrylate (GMA). Macromonomer conversion levels were improved for the GMA route via the use of high temperatures and tertiary amine catalysts. An optimum set of conditions was achieved using 1.4 diazabicyclo [2.2.2.] octane as the catalyst and a reaction temperature of 160 QC. Non aqueous dispersion polymerisations of methyl methacrylate were performed. The factors affecting particle size in both single stage and twin stage polymerisation schemes were studied. Increases in the particle sizes of these dispersions were observed with increases in the total monomer concentration and also with decreases in the total stabiliser concentration. Increases in the particle size could also be achieved by increasing the proportion of the total monomer in the seed stage of the twin stage reaction and also by decreasing the proportion of the total stabiliser in the seed stage. The importance of the role of the seed upon the final particle size was firmly established. The rheology of these non aqueous dispersions was studied over a range of concentrations and under increasing shear stresses. At Iow and intennediate volume fractions the dispersions were observed to be predominantly Newtonian. Non-Newtonian behaviour was only observed at the extremes of the shear stress ranges studied. At high volume fractions of the dispersions non-Newtonian behaviour was observed over the range of shear stresses studied. Maximum volume fractions (~m) were calculated for these dispersions using the Kreiger-Dougherty equation. When these dispersions were blended in size ratios of 2:1 it was observed that 4 > m could be increased due to improved particle packing efficiency.
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Emerging diseases of maize and onion caused by bacteria belonging to the genus PantoeaGoszczynska, Teresa 15 July 2008 (has links)
Center rot of onion, caused by Pantoea ananatis, was first described in the USA, in 1997. P. ananatis is seed-borne in onions and it was suggested that it was introduced into the USA on infected seed lots from South Africa. Center rot has not been observed in South Africa and it was essential to determine if P. ananatis is present in local onion seed. Colonies resembling those of P. ananatis were isolated from four South African seed lots on PA 20, a new semi-selective medium. Pathogenicity tests demonstrated that the South African and America strains induced the same symptoms on onion. Phenotypic and genotypic analyses identified the strains from seed as P. ananatis. In 2004/2005, an unreported disease of maize, brown stalk rot, was observed on commercial fields in South Africa. The representative strains induced disease symptoms similar to those observed in the field. The phenotypic and genotyping tests showed that the strains belonged to the genus Pantoea and separated them into two groups. The first group was identified as P. ananatis. The F-AFLP genomic fingerprints generated by the second group of strains, were distinctly different from those generated by known Pantoea species. To resolve the taxonomic position of Pantoea isolated from onion and maize, sixty-seven strains were subjected to a polyphasic study. The methods used included phenotypic characterisation, genomic fingerprinting, 16S rRNA gene sequence analysis and DNA-DNA hybridisation. The results revealed that the strains belong to three different species within the genus Pantoea: P. ananatis, P. vagens and a novel species, Pantoea allii sp. nov. / Thesis (PhD (Microbiology))--University of Pretoria, 2009. / Microbiology and Plant Pathology / unrestricted
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Capturing the dynamics of the South African sunflower seed market in a partial equilibrium frameworkVan Zyl, Izak Cornelius Johannes 16 August 2010 (has links)
Sunflower is the most important oilseed crop in South Africa and accounts for approximately 60 % of all oilseeds produced locally. The primary by-products of the sunflower seed crushing industry provides high-value inputs towards the food and animal feed manufacturing sector in the form of edible oil and protein meal. Prior to 1996, the South African sunflower seed complex market was controlled by the Oilseed Board, which operated a single-channel pool scheme and regulated the marketing of oilseeds and oilseed products. Since the liberalisation of the South African agricultural sector, role-players have been fully exposed to the dynamics and risks of the international oilseed complex market. Over the years participants in the agricultural commodity markets have developed various instruments to assist them in their decision-making process – one of them being commodity modelling, which is described as a methodological technique that provides a powerful analytical tool for examining the complexities of commodity markets. In South Africa, many role-players in the various agricultural industries make use of a multi-sector commodity level partial equilibrium model better know as the BFAP sector model which is maintained by the Bureau for Food and Agricultural Policy (BFAP) at the University of Pretoria. The objective of this study was to expand the coverage of the existing BFAP sector model by developing a comprehensive system of equations for the total sunflower seed complex, which includes not only a partial equilibrium model for sunflower seed, but also sunflower oil and cake. In this study much emphasis was not only placed on the formation of prices of the various products, but also the application of the most suitable model structures in order to trace the behaviour of the various prices under real market conditions as accurately as possible. This study applied the methodology developed by the Food and Agricultural Policy Research Institute (FAPRI) and further adapted by the Bureau for Food and Agriculture Policy (BFAP) to develop the partial equilibrium model of the South African sunflower complex. The single equations were estimated by mainly using ordinary least squares (OLS), but in cases where the results of the OLS were contradictory to the theory or where insufficient data was available, calibration techniques were employed and the equations were synthetically constructed. The constructed model was applied to lay down a baseline projection for the total production and consumption blocks of sunflower seed, oil and oilcake. The baseline projections also formed part of the ex post validation of the model’s performance. Finally the consistency of the model was evaluated in the form of scenario analysis. Various real-world market- and policy-related shocks were imposed and the results were compared to the baseline projections. In general the model developed in this dissertation performed well and can be used to analyse the effects of economic, technological and policy changes on the South African sunflower seed complex. It also provides a sound structure for the development of a complete South African oilseed complex model that includes soybeans, canola, groundnuts, cotton and imported palm oil. Copyright / Dissertation (MScAgric)--University of Pretoria, 2010. / Agricultural Economics, Extension and Rural Development / unrestricted
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The effects of urbanization on avian seed dispersal success of Toxicodendron radicans (Anacardiaceae)Stanley, Amber 05 April 2018 (has links)
The rate of global urbanization is increasing at an alarming pace, as the human population has grown to over 7 billion people—from 1.6 billion people in the 1900s—, half of which reside in urban areas. This increase has necessitated the expansion of urban habitat and increased consumption of natural resources. While the effects of urbanization on species diversity is well-documented (increasing urbanization decreases species diversity), its effects on species interactions have been less studied. Plant-animal interactions, such as seed dispersal, may be especially sensitive to urbanization. For plants, animal-based seed dispersal depends on several aspects, including 1) the rate of interactions with seed dispersers, 2) the probability of seed dispersal from an interaction event, 3) the identity and the number of seed disperser species –especially regarding differential ability to scarify seeds through digestion, and 4) the probability of germination after seed dispersal. Urbanization may affect seed dispersal dynamics by altering the frequency of interactions and/or the identity and diversity of seed dispersers. Consequently, the probability of seed dispersal and the ability of seeds to germinate and survive after being dispersed may be negatively affected by urbanization. In this study we ask specifically: 1) Will birds visit T. radicans at a greater rate in urban or natural habitats? 2) Will the diversity of dispersers be higher in urban or natural habitats? 3) Do seeds from urban or natural sites have a greater probability of dispersal? 4) Will seeds from urban or natural habitat be more likely to germinate? To compare differences in rate of visitation and disperser diversity between urban and natural habitats, individual T. radicans plants in two urban and two natural sites were observed for interactions by birds. Dispersal probability was estimated by marking fruits with a UV fluorescent dye and estimating a proportion of dispersed seeds at the end of the season. Seeds dispersed = total fruits marked – number of recovered fruits. Germination success will be estimated by collecting defecated—thus scarified—seeds in natural and urban sites as well as collecting non-dispersed seeds (that will be treated with either water or sulfuric acid). Seeds will be cold stratified 90 days before planting in constant 28oC and 16:8 L:D conditions. Preliminary results indicate that the rate of visitation, species diversity, and probability of seed dispersal are all significantly higher in urban sites. This trend suggests that T. radicans in urban habitat may be more successful than in natural habitat, however further research is necessary to confirm this.
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Assessing farmers’ willingness-to-way for improved common bean seed varieties in Malawi : a case study of Kasungu and Dedza districtsMunthali, Grace Timanyechi January 2013 (has links)
Common beans are one of the most important food and cash crops for most Malawians. The
insufficient production of the crop in the country coupled with low yields has made scientists
give much interest to the crop so that they can address the constraints to the productivity
problems. In this regard, breeders have been engaged in the development and release of
improved varieties of common beans which in most cases are disease resistant, high yielding,
drought resistant, and fast cooking. Therefore it is the interest of this study to find the reasons
why productivity of the crop is still low despite the release of the improved varieties.
The study adopted contingent valuation (CV), a method frequently used to assess willingnessto-
pay of people for non-market goods or services and this was applied to assess farmer’s
willingness-to-pay for the new improved bean seed varieties which are high yielding. Double
bounded dichotomous choice with an open ended follow-up format was used to obtain the
household’s willingness-to-pay. In addition; the study reviewed the existing dissemination
channels of bean seed to make recommendations with regard to seed supply.
Descriptive statistics from the 132 households interviewed shows that the structural
constraints to seed acquisition are compounded by farmers’ poverty. Otherwise, most farmers are aware of the existence of improved varieties of common bean seed and perceive that with
the use of this seed, productivity can improve hence willing to pay for the good. The study is
95% confident that mean price farmers are willing to pay for improved common bean seed is
between MK 527.78 and MK 591.92. Three major existing informal dissemination channels
of bean seed were discovered in the study areas.
Therefore there is a need for government to work in collaboration with NGOs towards
ensuring a formal supply system of bean seed characterised by vertically organised production
and dissemination of tested and approved seed varieties, and using strict quality control rules,
so that farmers can be assured of accessing improved seed varieties. This will increase the
nation’s food security. / Dissertation (MSc Agric)--University of Pretoria, 2013. / gm2014 / Agricultural Economics, Extension and Rural Development / unrestricted
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