No description available.

Thesis (M.S.)--Cleveland State University, 2007. / Abstract. Title from PDF t.p. (viewed on May 8, 2008). Includes bibliographical references (p. 41-45). Available online via the OhioLINK ETD Center. Also available in print.

Thesis (M.S.)--University of Wisconsin--Madison, 1982. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

No description available.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Sunflowers are considered to be a part of a group of plants known as hyperaccumulators that share the ability to accumulate high amounts of heavy metals in the above ground organs, far in excess of the levels found in other species, often without suffering any phytotoxic effects. Quantifying the effects of zinc accumulation through the lens of the elemental defense hypothesis is essential for uncovering if there is a means to increase herbivore resistance in agricultural settings without the use of external interventions such as pesticides. A greenhouse study was conducted on four widely grown commercial cultivars of sunflower. Each cultivar was grown under multiple soil Zn concentrations ranging from 0 to 200 mg/kg of soil. Growth rate measurements were taken at evenly spaced intervals until maturity. Samples of leaves were taken from plants and tested for Zn concentration. A qualitative study using Vanessa cardui was conducted to observe the effects of zinc in the diet of caterpillars. Significant variation in the level of zinc accumulated in the leaves was observed as well as variation in overall biomass per treatment level. V. cardui experienced high rates of mortality at high zinc concentrations suggesting that further study may lead to significant evidence that Zinc accumulation is a form of herbivore resistance.

A comercialização de flores vem crescendo anualmente em países em desenvolvimento, o que movimenta diversos setores produtivos. Desta forma, este trabalho teve como objetivo apresentar uma caracterização de cultivares de girassol ornamental semeados em diferentes épocas no oeste catarinense. Os cultivares avaliados foram “BRS Oásis”, “BRS Refúgio M” e “BRS Paixão M”, semeados nas seguintes épocas: 02, 16 e 31 de outubro, 17 de novembro, 01 e 15 de dezembro de 2008. O experimento foi realizado na EPAGRI localizada em Chapecó, Santa Catarina. O delineamento experimental foi o de blocos casualizados com três repetições e os tratamentos foram distribuídos em um bifatorial. Avaliou-se 36 variáveis fitomorfológicas e de produção bem como a senescência das flores após o corte. Dentre as principais variáveis fitomorfológicas de importância para a floricultura de corte, estudou-se diâmetro da inflorescência, diâmetro da haste, estatura de planta, cor da inflorescência, diâmetro do capítulo principal, número de dias até o corte das hastes, número de hastes secundárias, número de folhas principais, número de folhas secundárias, sendo que paralelamente efetuou-se também estudos de fitomassa das partes constituintes da planta. Como resultados verificou-se que os cultivares de girassol avaliados diferenciam-se quanto as principais variáveis avaliadas bem como a senescência das flores. O girassol ornamental possibilita cultivo no Oeste Catarinense, permitindo programação da colheita de suas hastes conforme necessidade de uso em ornamentações. A utilização de uma escala de senescência pode quantificar sua durabilidade de conservação das hastes. / The commercialization of flowers has been increasing annually in developing countries, what propels the diverse productive sectors. Thus, this study aimed at providing a characterization of ornamental sunflower cultivars sown at different times of the year in the west of Santa Catarina, Brazil. The cultivars assessed were BRS Oásis, BRS Refúgio M and BRS Paixão M which were sown in the following dates: October 2, 16 and 31, November 17, and December 01 and 15 of 2008. The experiment was conducted at EPAGRI, located in Chapecó, Santa Catarina. The experimental design was the randomized blocks with three replications and the treatments were distributed in a bifactorial. It was evaluated thirty-six phytomorphological and production variables as the flowers senescence after cutting. Among the main phytomorphological variables of great importance for cut flowers production, it was studied inflorescence diameter, stem diameter, plant height, inflorescence color, head diameter, number of days up to the stem cutting, number of secondary stems and number of primary and secondary leaves. It was also performed phytomass studies of the parts that constitute the plant. The results showed that the sunflower cultivars evaluated differ on the key variables assessed and flower senescence. The ornamental sunflower can be cultivated in the west of Santa Catarina, what allows picking programming of its stems as needed for using in ornamentation process. By using the senescence scale it is possible to quantify its durability of stems conservation.

Biochar, a carbon-rich and a potential solid biofuel, is produced during the liquefaction of biomass. Biochar can be combusted for heat and power, gasified, activated for adsorption applications, or applied to soils as a soil amendment and carbon sequestration agent. It is very important and advantageous to produce biochar under controlled conditions so that most of the carbon is converted. The main objective of the study was to investigate the effect of solvents, reaction temperature and reaction atmosphere on biochar production during the liquefaction of sunflower husks. The liquefaction of sunflower husks was initially investigated in the presence of different solvents (water, methanol, ethanol, iso-propanol and n-butanol) to study the effect of solvents on biochar yields. The experiments were carried out in an SS316 stainless steel high pressure autoclave at 280°C, 30 wt.% biomass loading in a solvent and starting pressure of 10 bar. Secondly, sunflower husks were liquefied at various temperatures (240-320°C) to assess the influence of reaction temperature on the biochar yield. Experiments were carried out under either a carbon dioxide or nitrogen atmosphere with a residence time of 30 minutes. Biochar samples obtained from sunflower husk liquefaction were structurally characterised by scanning electron microscopy (SEM) and Brunauer-Emmet-Teller (BET) analysis to compare surface morphological changes and pore structural changes at different reaction temperatures. Compositional analysis was done on sunflower husk biochar samples by proximate analysis, Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Elemental analysis. The results showed that biochar produced through the liquefaction of sunflower husks was significantly affected by the type of solvent used. The highest biochar yields were obtained when ethanol was used (57.35 wt. %) and the lowest yields were obtained when n-butanol was used as a solvent (41.5 wt. %). A temperature of 240°C was found to produce the highest biochar yield (64 wt. %). However, biochar yields decreased with increasing liquefaction temperature and the lowest yield was 41wt. % at 320°C. Temperature had the most significant influence on biochar yield in an N₂ atmosphere, while solvent choice had the most significant influence on biochar yield in a CO₂ atmosphere. Temperature also had an effect on the structure of biomass, as the SEM analysis shows the biochar became more porous with increasing temperature. Generally, results from the CO₂ adsorption analysis, suggested that CO₂ develops microporosity to a greater extent than N₂ reaction. The results of sunflower husk compositional analysis show that sunflower husks contain a high lignin content (34.17 wt. %), of which the high lignin content in biomass is associated with high heating value and high solid yield product. Sunflower husks as waste product can be used to produce useful products such as biochar through liquefaction, and biochar can be used to generate heat and as a soil amendment due to its high heating value and high porosity. While these preliminary studies appear promising for the conversion of sunflower husks to biochar, further studies are needed. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2014

Biochar, a carbon-rich and a potential solid biofuel, is produced during the liquefaction of biomass. Biochar can be combusted for heat and power, gasified, activated for adsorption applications, or applied to soils as a soil amendment and carbon sequestration agent. It is very important and advantageous to produce biochar under controlled conditions so that most of the carbon is converted. The main objective of the study was to investigate the effect of solvents, reaction temperature and reaction atmosphere on biochar production during the liquefaction of sunflower husks. The liquefaction of sunflower husks was initially investigated in the presence of different solvents (water, methanol, ethanol, iso-propanol and n-butanol) to study the effect of solvents on biochar yields. The experiments were carried out in an SS316 stainless steel high pressure autoclave at 280°C, 30 wt.% biomass loading in a solvent and starting pressure of 10 bar. Secondly, sunflower husks were liquefied at various temperatures (240-320°C) to assess the influence of reaction temperature on the biochar yield. Experiments were carried out under either a carbon dioxide or nitrogen atmosphere with a residence time of 30 minutes. Biochar samples obtained from sunflower husk liquefaction were structurally characterised by scanning electron microscopy (SEM) and Brunauer-Emmet-Teller (BET) analysis to compare surface morphological changes and pore structural changes at different reaction temperatures. Compositional analysis was done on sunflower husk biochar samples by proximate analysis, Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Elemental analysis. The results showed that biochar produced through the liquefaction of sunflower husks was significantly affected by the type of solvent used. The highest biochar yields were obtained when ethanol was used (57.35 wt. %) and the lowest yields were obtained when n-butanol was used as a solvent (41.5 wt. %). A temperature of 240°C was found to produce the highest biochar yield (64 wt. %). However, biochar yields decreased with increasing liquefaction temperature and the lowest yield was 41wt. % at 320°C. Temperature had the most significant influence on biochar yield in an N₂ atmosphere, while solvent choice had the most significant influence on biochar yield in a CO₂ atmosphere. Temperature also had an effect on the structure of biomass, as the SEM analysis shows the biochar became more porous with increasing temperature. Generally, results from the CO₂ adsorption analysis, suggested that CO₂ develops microporosity to a greater extent than N₂ reaction. The results of sunflower husk compositional analysis show that sunflower husks contain a high lignin content (34.17 wt. %), of which the high lignin content in biomass is associated with high heating value and high solid yield product. Sunflower husks as waste product can be used to produce useful products such as biochar through liquefaction, and biochar can be used to generate heat and as a soil amendment due to its high heating value and high porosity. While these preliminary studies appear promising for the conversion of sunflower husks to biochar, further studies are needed. / MSc (Engineering Sciences in Chemical Engineering), North-West University, Potchefstroom Campus, 2014

Common sunflower is a competitive annual native dicot found in disturbed areas, on roadsides, dry prairies, and in row crops. Common sunflower is a competitive weed, but little data exist on interference, economic impacts, and competition in field corn. Field studies were conducted in 2006 and 2007 to 1) define the density-dependent effects of common sunflower competition with corn; 2) define the necessary weed-free periods of common sunflower in corn; 3) evaluate common sunflower control with herbicides; 4) and define the economic impact of common sunflower interference with corn. Corn grain yield was significantly reduced when common sunflower densities reached 1 plant/m of row and potentitially damaging common sunflower densities occurred if allowed to compete for more than 2 to 4 wk after planting for maximum corn yield. No significant corn yield reduction occurred if common sunflowers emerged 8 wk after planting. Growing degree day (GDD) heat units for corn showed that the critical point for control of common sunflower was approximately 300 GDD. Atrazine applied PRE, atrazine followed by (fb) glyphosate or halosulfuron POST, glyphosate POST, halosulfuron POST, and halosulfuron plus nicosulfuron POST controlled >87% of common sunflower. Atrazine applied PRE in a 30-cm band, nicosulfuron POST, and atrazine broadcast plus S-metolachlor PRE showed significantly lower common sunflower control and corn grain yield, when compared to atrazine PRE fb glyphosate POST. Economic impact of one sunflower/6 m of crop row caused a yield loss of 293 kg/ha. Various corn planting densities showed that corn yield can be reduced 1990 kg/ha with common sunflower competition. Corn planting densities of 49400 and 59300 plants/ha provided the greatest net returns with or without the presence of common sunflower competition. The highest net returns occurred with no common sunflower competition in 2006 and 2007, at $3,046/ha and $2,687/ha, respectively, when net corn prices were $0.24/kg ($6.00/bu). Potential control costs of various herbicide treatments revealed net returns of $1,156 to $1,910/ha in 2006 and $1,158 to $1,943/ha in 2007. Determining the economic impact of common sunflower interference in field corn allows producers to estimate the overall net return based upon density and duration of common sunflower interference, while considering varying net corn prices, crop planting density, and herbicide application costs.