The aim of the present study was to determine if there is a difference in ovulation- and conception rates, in semiintensively managed Dohne-Merino ewes, flush fed with diets containing different nitrogen sources. Four different nitrogen sources were chosen due to the difference in dietary amino acid composition and cost. In order for a sheep farming enterprise to maximize profitability it is essential to optimize ovulation- and conception rates and to minimize lamb losses in order to increase weaning percentage and therefore profitability. However the cost of dietary supplementation is high and may increase production costs and minimize profitability. One hundred and fourty four (144) Dohne-Merino ewes (age between 14 to 85 months) were included in two dietary supplementation trials (autumn and summer) at the experimental farm of the University of Pretoria in Hatfield. The ewes were divided equally into two trial groups (n=72), with the first trial done in season 1 (started in May 2001, typical breeding season) and the second trial done in season 2 (started in November 2001, out of season; 2nd breeding season). During the day the ewes had ad-libitum access to graze on Festuca arundinaceace (Tall Fescue). In both trials the ewes (n=72) were randomly allocated into four dietary supplementation groups, each group receiving a dietary supplement with a different combination of nitrogen sources. The four dietary supplements were formulated on an iso-nitrogen basis, to eliminate the effect of protein level, and to emphasize the possible effect of protein quality (amino acid composition) on ovulation, conception and lambing rates. In both trials the total amount of crude protein intake per ewe was calculated at 256.40g/day, while the total daily allowance of digestible crude protein was calculated at 190g per ewe. The 256.40g crude protein intake per ewe per day is 2 times more than the threshold level of 125g per ewe per day. A minimum daily crude protein intake of 125g is needed for effective rumen functioning, and this together with the interconvertin of energy by the rumen indicates the complex nature of relating dietary differences to physiological responses. These values were kept the same for both the trials in season 1 and 2. The bulk of the 256.40g crude protein per day was obtained from grazing on the Festuca arundinaceace pasture. In season 1 the dietary supplement had to provide 40.00g of crude protein per day in order to get to a daily crude protein intake of 256.40g, while in season 2 the provision from the dietary supplement was calculated to be 37.45g of crude protein. The difference in the crude protein level, obtained from grazing of the Festuca arundinaceace between season 1 and 2 was due to pasture quality differences. The nitrogen sources used in the trials were urea, sunflower oilcake meal, cottonseed oilcake meal and a mixture of cottonseed oilcake meal and fishmeal. These dietary supplements were fed for a period of 9 days before mating; the weight of each ewe was recorded before the onset of the trial and again on the second day after mating to establish any live weight changes. Synchronization of the ewes was done with Chrono-gest grey sponges (40mg Fluorogestone acetate) from day one and was repeated from day 23. On day 12 each ewe were injected with 1.0ml prostaglandin F2α (Prosolvin,each milliliter containing 7.5mg Luprostiol). On day fourteen the sponges were removed and two days later all the ewes were checked for cyclic activity with the aid of six vasectomized rams. The six vasectomized rams were introduced to the whole laparoscopy group of 12 ewes, and every ewe that stood twice for mating were identified as cyclic. This practice continued for a period of 30 minutes in the morning and repeated for another 30 minutes in the afternoon up to day 18. The second round of sponges were inserted on day 23 and removed on day 37. Ewes were mated by means of hand mating with two different rams from day 39 to 42. A laparoscopy technique was used on day 45 of the trial to count the number of ovulation points (corpora lutea) on each ovarium of each ewe. The number of fetuses of each ewe was counted on day 90 after mating by means of ultrasound scanning and at birth the number of lambs born was also recorded. In both these trials dietary supplementation had no significant effect on ovulation, conception and lambing rates. However, looking at the Odds Ratio Analysis for the 144 ewes over the two breeding seasons, the different dietary supplements had a significant influence on the number of ovulation points (p<0.05). Compared to urea (dietary supplement 1), the fishmeal cottonseed oil cake mixture (dietary supplement 4) yielded the best results (1.306), followed by the cottonseed oil cake meal (dietary supplement 3) (1.298), and sunflower oil cake meal (dietary supplement 2) (1.050). The same Odds Ratio Analysis showed that the different dietary supplements had a significant effect on the number of lambs born (p<0.01). Compared to urea (dietary supplement 1), the fishmeal cottonseed oil cake mixture (dietary supplement 4) yielded better results (1.086), followed by urea (dietary supplement 1) (1.000), and sunflower oil cake meal (dietary supplement 2) (0.801) and lastly cottonseed oil cake meal (dietary supplement 3) (0.784). Breeding season (p<0.05) had a significant effect on the number of ovulation points but no difference was observed in terms of the number of lambs born. Age (p<0.01) had a significant effect on the number of ovulation points, the number of fetuses counted as well as the number of lambs born. Change in live weight (p<0.05) had a significant effect on the number of ovulation points per ewe but as with breeding season it had no significant effect on the number of lambs born. Birth status of a ewe (p<0.05), had a significant effect on the number of fetuses and the number of lambs born. The data of both the trials in season 1 and 2 suggests that under the conditions of the study with the odds ratio analyses that the four different dietary supplements had a significantly different effect compared to dietary supplement one on the number of ovulation points and the number of lambs born. However, factors like breeding season, age, change in live weight and birth status of the ewe also had a significant effect on ovulation and conception rates in Dohne-Merino ewes. / Dissertation (MSc(Agric))--University of Pretoria, 2011. / Animal and Wildlife Sciences / unrestricted

Microalgae has shown to be an ideal choice for biofuel industry. Algae has high oil productivity, a short growth cycle and survives in a wide variety of water sources including high salinity and waste water. For this project, four different species of marine microalgae were screened based on oil content. They were Dunaliella tertiolecta (CCMP364), Nannochloropsis gaditana (CCMP527), Tetraselmis sp (CCMP 908) and Nannochloropsis salina (CCMP1776). Experimental results showed that CCMP 527 and 1776 strains had higher lipid content and better fatty acids profile than the other two. Further investigations were carried on CCMP 527 in order to maximize biomass productivity and lipid content. Nutrients, salinity, pH, temperature, light intensity and aging of the culture can all affect both lipid content and fatty acid profile and were investigated. Nutrient stress is the easiest way to manipulate lipid composition and increase lipid content. Hence, various carbon and nitrogen sources were investigated to determine the range and amount of substrates that may be feasible for cultivation. For supplying lipid for biodiesel production, the optimum culture conditions for strain Nannochloropsis gaditana are using CO₂ enriched air bubbling, f/2-Si medium, pH control, and nitrate as the nitrogen source. Use of other fertilizers is feasible as well, however, the nitrogen source greatly affects lipid productivity, but trace amounts of organics in ground water do not.A model which predicts cell growth, nitrogen concentration, and lipid yield in batch systems is developed that is applicable for low nitrogen conditions. Plus, a sensitivity analysis of three major parameters was done to validate how variations in these key parameters affect simulation results. The fatty acid profile as a function of time was shown not to vary from mid-exponential to stationary phase. The model describes reactor behavior well, therefore it can be applied to the genus of Nannochloropsis to predict biomass yield and lipid accumulation, and be a useful tool to optimize and compare bioreactor systems for the biofuel industry. In addition, effects of nitrate and urea under repletion condition on microalgae growth, lipid yield and fatty acids profile for microalgae Nannochloropsis gaditana were investigated. Replacing nitrate by urea didn't show positive influence on lipid content and yield compared to normal medium. The major fatty acids for these two mediums were palmitic acid (C16:0) and palmitioleic acid (C16:1). Nannochloropsis gaditana still shows to be ideal candidate for biodiesel production using urea or nitrate enriched agriculture wastewater.

A maior dificuldade de incorporação no solo dos fertilizantes nitrogenados é preocupante no sistema de cana crua e, uma vez, que a uréia é a fonte mais utilizada, pode-se incorrer em riscos de perdas de NH3 por volatilização. Nesse sentido, foi realizado experimento em campo (LATOSSOLO VERMELHO Argiloso Distrófico) com o objetivo de avaliar a eficiência agronômica do cloreto de amônio em relação a outras fontes comerciais de N em soqueira de segundo corte (cultivar SP89 1115), bem como o efeito do N-residual no ciclo subseqüente (terceira rebrota). O delineamento experimental foi o de blocos casualizados, com quatro repetições. Os tratamentos constaram de quatro fontes nitrogenadas: cloreto de amônio (CA), nitrato de amônio (NA), sulfato de amônio (SA) e uréia (U), aplicados na dose de 120 kg ha-1 de N, enquanto que o cloreto de amônio foi aplicado nas doses de N: 60, 120 e 180 kg ha-1. Incluiu-se um tratamento testemunha sem adição de N-fertilizante. A cana soca de segundo corte foi colhida em novembro de 2006 e em dezembro de 2006 foram aplicados os tratamentos. A colheita mecanizada sem queima prévia do canavial foi realizada em novembro de 2007 e em dezembro de 2007 foi aplicado 450 kg ha-1 do formulado 20-5-19, visando avaliar o efeito do N-residual dos tratamentos implantados em dezembro de 2006. Para a safra 2006/2007 a maior produção de colmos e Pol da cana em t ha-1 relacionadas à fonte de nitrogênio foram obtidas no tratamento SA, diferindo-se significativamente da testemunha, não diferindo porém dos tratamentos U e CA. As maiores médias de concentração foliar (F+1) para nitrogênio foram dos tratamentos com adubação nitrogenada, promovendo efeito positivo nas concentrações foliares de P, Mg e S. A produtividade de colmos (TCH) na colheita de novembro de 2006 respondeu de forma linear ao incremento das doses de N na forma de cloreto de amônio. As margens de contribuição agrícola foram positivas para todos os tratamentos, inclusive para a testemunha. Com relação ao efeito do N-residual na safra 2007/2008, verificou-se em geral, que as concentrações de macronutrientes na F+1 de cana-de-açúcar estavam dentro da faixa considerada adequada para o Estado de São Paulo. O N-residual das doses de CA resultou em significativa redução na produção de colmos (TCH) e açúcar (TPH). Para o N-residual das fontes de N, o tratamento SA foi o que apresentou a maior produção de colmos, diferindo dos tratamentos U e CA. O Nresidual do tratamento SA120 foi o que apresentou a melhor relação custo-benefício para a produção de colmos. Concluiu-se, que a fonte CA na dose de 120 kg ha-1 de N em adubação de soqueira de segundo corte mostrou-se agronomicamente eficiente em relação às fontes de N comumente utilizadas pelo setor canavieiro, apresentando menor eficiência do N-residual no ciclo subsequente. / The greatest difficulty of incorporation into the soil of nitrogen fertilizer is worrying in the system of \"green cane\" (sugar cane harvested without burning), and once that urea is the nitrogen source most used, we can incur risks of loss by volatilization of NH3. Accordingly, an experiment was conducted in the field (Distrofic Red Oxisol clayed) to evaluate the agronomic efficiency of ammonium chloride in relation to other commercial sources of N in a second harvested sugarcane ratoon (cultivar SP89 1115), and the effect of residual-N in the subsequent agricultural cycle of growth (third sugar cane ratoon). The experimental design was a randomized block design with four replications. The treatments consisted of four nitrogen sources: ammonium chloride (AC), ammonium nitrate (AN), ammonium sulfate (SA) and urea (U), applied at a dose of 120 kg ha-1 of N, while the ammonium chloride was applied at doses of N: 60, 120 and 180 kg ha-1. It was included a control treatment without addition of fertilizer-N. The mechanical harvesting of second sugar cane ratoon was performed in November of 2006 (without burning) and in December of 2006 the treatments were applied. The harvest of third sugarcane ratoon without prior burning was held in November of 2007 and in December of 2007 was applied 450 kg ha-1 made of a formule 20-5-19, to evaluate the effect of residual-N. For the 2006/2007 agricultural growth season of sugarcane ratoon the greatest production of sugar cane stalks and Pol in t ha-1 related to the nitrogen source were obtained in the SA treatment, and it was significantly different from control treatment, but not differing from the U and CA treatments. The highest average concentration of leaf nitrogen (L+1) were for the treatments with nitrogen, promoting positive effect on foliar concentrations of P, Mg and S. The productivity of stalks (TCH) in the final harvest (November of 2006) responded linearly to the doses of N as ammonium chloride. The margin of agricultural contribution were positive to all treatments, including the control. Regarding the effect of residual fertilizer-N in the agricultural growth season of 2007/2008, there was in general, the concentration of nutrients in the L +1 of sugarcane were within of the considered appropriate range for sugarcane growth in the State of São Paulo. The residual doses-N of AC resulted in significant reduction in the production of stalk (TCH) and sugar (TPH). The residual-N from the SA treatment showed the highest production of stalks, differing from the U and AC treatments. The residual-N from the treatment SA120 showed the most cost-effective for the production of stalks. It was concluded that the AC source at a dose of 120 kg ha-1 of N fertilization was shown to be agronomically effective in relation on N sources commonly used by the sugarcane sector in Brazil, showing lower efficiency of residual-N in the subsequent agricultural growth cycle.

Ao longo dos últimos anos, o metabolismo ácido das crassuláceas (CAM) tem sido bem estudado em espécies das famílias Bromeliaceae e, principalmente, Crassulaceae. Essa via fotossintética é caracterizada pelo acúmulo noturno de ácidos orgânicos dentro do vacúolo e pela fixação de CO2 durante a noite pela enzima fosfoenolpiruvato carboxilase (PEPC). No entanto, pouco se sabe sobre a preferência pela atividade da enzima ATPase ou PPiase no transporte de prótons e ácidos orgânicos no interior das vesículas do tonoplasto em espécies CAM. A fotossíntese CAM pode ser induzida em plantas caracterizadas como CAM-facultativas por diversos fatores ambientais, por exemplo, déficit hídrico, termoperíodo, salinidade e deficiência de nutrientes. Contudo, pouco tem sido discutido sobre a influência dos nutrientes na indução do CAM. Esse estudo investigou o transporte de prótons através da membrana do tonoplasto em seis espécies de bromélias CAM e duas espécies de Kalanchoë. Todas as espécies usadas nesse estudo mostrou uma preferência pela ATPase do que pela PPiase para o transporte de prótons e ácidos orgânicos no interior das vesículas do tonoplasto. Nós também observamos uma maior expressão do CAM nas plantas de Kalanchoë laxiflora e Kalanchoë tubiflora mantidas na presença de 2.5 mM de NO3-. Por outro lado, Guzmania monostachia, uma espécie de bromélia epífita, exibiu a maior intensidade do CAM nas folhas mantidas na presença de NH4+ + déficit hídrico. Nessa espécie de bromélia, a maior expressão do gene ALMT9 na porção apical das folhas, seguido pelas maiores taxas de transporte de prótons pela ATPase, acúmulo de açucares solúveis e a ativação das defesas antioxidantes parecem estar relacionados com o aumento da tolerância pelo ajuste osmótico e limitação do dano oxidativo nas folhas mantidas na presença de NH4+ + déficit hídrico. Uma outra explicação para a maior intensidade do CAM no ápice das folhas mantidas em NH4+ + déficit hídrico poderia ser a maior expressão dos genes que codificam aquaporinas, principalmente GmPIPs e GmTIPs, que talvez sejam responsáveis pelo transporte de água das porções basal e mediana para a porção apical das folhas. O maior conteúdo de água conservado na porção apical poderia ajudar a aumentar a intensidade da fotossíntese CAM nessa porção das folhas de G. monostachia mantidas na presença de NH4+ + déficit hídrico / Historically, crassulacean acid metabolism (CAM) has been studied in many families, mainly Bromeliaceae and Crassulaceae. This photosynthetic pathway is characterized by the nocturnal organic acid accumulation in the vacuole as well as CO2 fixation during the night by the phosphoenolpyruvate carboxylase enzyme (PEPC). However, little is known about the preference of ATPase or PPiase activities for the proton and organic acids transport in tonoplast vesicles in CAM species. CAM photosynthesis can be inducted in CAM-facultative species by environmental factors such as, water deficit, thermoperiod, salinity and nutrients deficiency. Although, little has been discussed about the influence of nutrients on CAM induction. This study investigated proton transport in CAM bromeliad species and two CAM Kalanchoë species. All of the species used in this study showed a preference for ATPase rather than PPiase for the proton and organic acids transport into the tonoplast vesicles. We also observed a higher CAM expression in Kalanchoë laxiflora and Kalanchoë tubiflora plants kept in the presence of 2.5 mM of NO3-. On the other hand, Guzmania monostachia plants, an epiphytic tank bromeliad species, exhibited the highest CAM intensity in the leaves kept in the presence of NH4+ + water deficit. In this same bromeliad, a malate transporter gene, ALMT9, showed its highest expression in the apical portion of the leaves and the highest proton transport rates into the vacuole by ATPase. Soluble sugars and antioxidant enzymes activities were also verified in this study in order to observe their influence on increasing the drought tolerance of G. monostachia. In the leaves kept in NH4+ + water deficit the highest antioxidant activities and accumulation of soluble sugars were observed, this suggests that this inorganic nitrogen source seems to increase the drought tolerance by osmotic adjustment and limitation of oxidative damage. These factors can favor the increase of CAM intensity in the leaves kept under NH4+ + water deficiency. Another explanation for why the highest CAM intensity was observed in the apical portion of the leaves kept in NH4+ + water deficiency is because of the higher expression of aquaporin genes in the basal and middle regions of the leaves in the presence of this N source, mainly GmPIP and GmTIP, which might be responsible for transporting water from the basal and middle portions to the apical portion where these AQP genes are repressed. The fact that the highest water content is conserved in the apical portion might help to explain the increase in the intensity of CAM photosynthesis observed in the leaves of G. monostachia kept in the presence of NH4+ + water deficit

A maior dificuldade de incorporação no solo dos fertilizantes nitrogenados é preocupante no sistema de cana crua e, uma vez, que a uréia é a fonte mais utilizada, pode-se incorrer em riscos de perdas de NH3 por volatilização. Nesse sentido, foi realizado experimento em campo (LATOSSOLO VERMELHO Argiloso Distrófico) com o objetivo de avaliar a eficiência agronômica do cloreto de amônio em relação a outras fontes comerciais de N em soqueira de segundo corte (cultivar SP89 1115), bem como o efeito do N-residual no ciclo subseqüente (terceira rebrota). O delineamento experimental foi o de blocos casualizados, com quatro repetições. Os tratamentos constaram de quatro fontes nitrogenadas: cloreto de amônio (CA), nitrato de amônio (NA), sulfato de amônio (SA) e uréia (U), aplicados na dose de 120 kg ha-1 de N, enquanto que o cloreto de amônio foi aplicado nas doses de N: 60, 120 e 180 kg ha-1. Incluiu-se um tratamento testemunha sem adição de N-fertilizante. A cana soca de segundo corte foi colhida em novembro de 2006 e em dezembro de 2006 foram aplicados os tratamentos. A colheita mecanizada sem queima prévia do canavial foi realizada em novembro de 2007 e em dezembro de 2007 foi aplicado 450 kg ha-1 do formulado 20-5-19, visando avaliar o efeito do N-residual dos tratamentos implantados em dezembro de 2006. Para a safra 2006/2007 a maior produção de colmos e Pol da cana em t ha-1 relacionadas à fonte de nitrogênio foram obtidas no tratamento SA, diferindo-se significativamente da testemunha, não diferindo porém dos tratamentos U e CA. As maiores médias de concentração foliar (F+1) para nitrogênio foram dos tratamentos com adubação nitrogenada, promovendo efeito positivo nas concentrações foliares de P, Mg e S. A produtividade de colmos (TCH) na colheita de novembro de 2006 respondeu de forma linear ao incremento das doses de N na forma de cloreto de amônio. As margens de contribuição agrícola foram positivas para todos os tratamentos, inclusive para a testemunha. Com relação ao efeito do N-residual na safra 2007/2008, verificou-se em geral, que as concentrações de macronutrientes na F+1 de cana-de-açúcar estavam dentro da faixa considerada adequada para o Estado de São Paulo. O N-residual das doses de CA resultou em significativa redução na produção de colmos (TCH) e açúcar (TPH). Para o N-residual das fontes de N, o tratamento SA foi o que apresentou a maior produção de colmos, diferindo dos tratamentos U e CA. O Nresidual do tratamento SA120 foi o que apresentou a melhor relação custo-benefício para a produção de colmos. Concluiu-se, que a fonte CA na dose de 120 kg ha-1 de N em adubação de soqueira de segundo corte mostrou-se agronomicamente eficiente em relação às fontes de N comumente utilizadas pelo setor canavieiro, apresentando menor eficiência do N-residual no ciclo subsequente. / The greatest difficulty of incorporation into the soil of nitrogen fertilizer is worrying in the system of \"green cane\" (sugar cane harvested without burning), and once that urea is the nitrogen source most used, we can incur risks of loss by volatilization of NH3. Accordingly, an experiment was conducted in the field (Distrofic Red Oxisol clayed) to evaluate the agronomic efficiency of ammonium chloride in relation to other commercial sources of N in a second harvested sugarcane ratoon (cultivar SP89 1115), and the effect of residual-N in the subsequent agricultural cycle of growth (third sugar cane ratoon). The experimental design was a randomized block design with four replications. The treatments consisted of four nitrogen sources: ammonium chloride (AC), ammonium nitrate (AN), ammonium sulfate (SA) and urea (U), applied at a dose of 120 kg ha-1 of N, while the ammonium chloride was applied at doses of N: 60, 120 and 180 kg ha-1. It was included a control treatment without addition of fertilizer-N. The mechanical harvesting of second sugar cane ratoon was performed in November of 2006 (without burning) and in December of 2006 the treatments were applied. The harvest of third sugarcane ratoon without prior burning was held in November of 2007 and in December of 2007 was applied 450 kg ha-1 made of a formule 20-5-19, to evaluate the effect of residual-N. For the 2006/2007 agricultural growth season of sugarcane ratoon the greatest production of sugar cane stalks and Pol in t ha-1 related to the nitrogen source were obtained in the SA treatment, and it was significantly different from control treatment, but not differing from the U and CA treatments. The highest average concentration of leaf nitrogen (L+1) were for the treatments with nitrogen, promoting positive effect on foliar concentrations of P, Mg and S. The productivity of stalks (TCH) in the final harvest (November of 2006) responded linearly to the doses of N as ammonium chloride. The margin of agricultural contribution were positive to all treatments, including the control. Regarding the effect of residual fertilizer-N in the agricultural growth season of 2007/2008, there was in general, the concentration of nutrients in the L +1 of sugarcane were within of the considered appropriate range for sugarcane growth in the State of São Paulo. The residual doses-N of AC resulted in significant reduction in the production of stalk (TCH) and sugar (TPH). The residual-N from the SA treatment showed the highest production of stalks, differing from the U and AC treatments. The residual-N from the treatment SA120 showed the most cost-effective for the production of stalks. It was concluded that the AC source at a dose of 120 kg ha-1 of N fertilization was shown to be agronomically effective in relation on N sources commonly used by the sugarcane sector in Brazil, showing lower efficiency of residual-N in the subsequent agricultural growth cycle.

Master of Science / Department of Agronomy / Ignacio Ciampitti / Soybean [Glycine max (L.) Merr.] yields have continuously increased over time. Seed yields are determined by the genotype, environment, and management practices (G × E × M) interaction. Closing yield gaps require a continuous improvement in the use of the available resources, which must be attained via implementation of better management decisions. Linear relationships between seed yield and nitrogen (N) demand are reported in the scientific literature. Main sources of N to the plant are the biological N fixation (BNF) and the soil mineralization processes. On overall, only 50-60% of soybean N demand is met by the BNF process. An unanswered scientific knowledge is still related to the ability of the BNF to satisfy soybean N demand at varying yield levels. Seed N demand not met by N fixation plus soil mineral N, is then fulfilled by the remobilization of N from vegetative organs during the seed filling period. An early remobilization process reduces the photosynthetic activity (leaves) and can limit seed yield. The objectives of this project were to: i) study yield improvements and contribution of N via utilization of contrasting N conditions under historical and modern soybean genotypes, and ii) quantify main seed N sources during the seed filling period. For objective one, four field experiments were conducted during the 2016 and 2017 growing seasons in Kansas, United States (US) and Santa Fe Province, Argentina (ARG). Those experiments investigated twenty-one historical and modern soybean genotypes with release decades from 1980s to 2010s. As for objective two, three field experiments were conducted during the 2015 and 2016 growing seasons in Kansas, US, studying three soybean genotypes: non-roundup ready (RR), released in 1997; RR-1, released in 2009; and RR-2, released in 2014. Across all studies, seeds were inoculated and tested under three N management strategies: i) control without N application (Zero-N); ii) 56 kg N ha-1 applied at reproductive growth stages (Late-N); and iii) 670 kg ha-1 equally split at three timings (Full-N). As for yield improvements and N limitation, soybean yield improvements from the 1980s to 2010s were documented, representing 29% increases in the US and 21% in ARG. Regarding N management, the Full-N fertilization produced a 12% increase in seed yields in the US and 4% in ARG. As for main seed N sources in objective two, remobilization accounted for 59% of seed N demand, and was negatively related to new N uptake occurring during the seed filling period. Seed N demand for greater yields was dependent on both, N remobilization and new N uptake, while for lower yields, seed N demand was mainly supported by the N remobilization process. These results suggest that: a) high seed yields are somehow limited by the availability of N to express their potential, although the question about N application still remains to be fully investigated, as related to the timing and the environment by plant interactions that could promote a N limitation in soybeans; b) remobilization accounts for majority (59%) of N sourced to the seed, and c) high yielding soybean (modern genotypes) rely on diverse N sources: the N remobilization process plus new uptake of N.

The economic impact of reducing the amount of nitrate leached out of the root zone under irrigation in the arid West was examined. A general introduction into the nature of the problem and a review of the literature was provided in chapter I. In chapter ll the economic incentives of irrigation management were evaluated under the assumptions of both profit-maximizing and utility-maximizing (in reducing cost and effort expended in irrigation) decision-making criteria. The results indicate that there is a coincidence of interests of the farmer and the environment. Both behaviors result in less nitrate leaching than less profitable or less utilityproducing irrigating practices. In chapter lli the economic impact of reducing the amount of nitrate leached out of the root zone under irrigation with various nitrogen sources and application methods was examined. The economic incentives of nitrogen management were evaluated under the assumption of profit-maximizing behavior. The results indicate that there is a coincidence of interests for irrigators who respond to economic incentives and environmentalists who wish to reduce nitrate residuals in irrigation drainage and the groundwater. Profit-maximizing behavior results in less nitrate leaching than less profitable irrigating practices when salt balance is not a major concern.

L(+)-Lactic acid is a commonly occurring organic acid, which is valuable due to its wide use in food and food-related industries, and its potential for the production of biodegradable and biocompatible polylactate polymers. The aim of this study was to optimize and scale-up a biotechnological process of L(+)-lactic acid production by suspended cells of R. arrhizus DAR 36017 with waste potato starch as the substrate. Commonly used inorganic and organic nitrogen sources, including ammonium sulphate, ammonium nitrate, urea, yeast extract and peptone, were assessed in conjunction with various ratios of carbon to nitrogen (C:N). Fermentation media with a low C:N ratio enhanced the production of lactic acid, biomass and ethanol, while a high C:N ratio led to production of more fumaric acid as a by-product. The use of organic nitrogen sources (yeast extract, peptone and urea) resulted in a significant reduction of lactic acid yields by 15% - 34% with a decrease of C:N from 168 to 28. The use of inorganic nitrogen sources (ammonium nitrate and ammonium sulphate) led to a high lactic acid yield of 84% - 91% at a C:N below 168. Therefore, ammonium nitrate and ammonium sulphate were considered to be better nitrogen sources for lactic acid production. Small pellets are the favoured morphological form for many fermentation processes by filamentous fungi. However, to control filamentous Rhizopus sp in the pellet form in a submerged fermentation system is difficult due to its filamentous characteristics. An acidadapted preculture technique was developed to induce the formation of the pellet form in bioreactors. Using the acid-adapted precultures, the fungal biomass can be controlled in small dispersed pellets as a dominant morphological form. With these small pellets, a lactic acid yield of 86-89%, corresponding to a concentration of 86-89g/L, was obtained in a laboratory scale process using a stirred tank reactor (STR) and a bubble column reactor (BCR). A batch bioprocess for lactic acid production was successfully scaled-up from shake flasks to laboratory scale bioreactors. Results from a simulated scale-up process revealed that the concentration and productivity of lactic acid decreased with the increase of the scale-up steps because of increased pellet size. This suggested that a one-step scale-up process using the acid-adapted preculture may be feasible in an industrial-scale bioreactor system. A comprehensive investigation of the impact of cultivation parameters on the morphology of R. arrhizus and lactic acid production was carried out in the BCR. The results showed that the fungal morphology was significantly influenced by carbon sources, pH, starch concentrations, sparger designs and aeration rates. The favoured morphology for lactic acid production was freely dispersed small pellets, which could be retained as a dominant morphology under operation conditions at pH 5.0 – 6.0, starch concentrations of 60 – 120 g/L and aeration rates of 0.2 – 0.8 vvm, using a sintered stainless steel disc sparger. The optimal cultivation conditions at pH 6.0 and aeration rate of 0.4 vvm resulted in the formation of the freely dispersed small pellets and production of 103.8 g/L lactic acid, with a yield of 87%, from 120 g/L liquefied potato starch in 48 h. This study shows a technically feasible and economically promising process for the production of lactic acid from waste potato starch. The use of waste potato starch instead of pure glucose or starch as substrate can significantly reduce the production cost, making this technology environmentally and economically attractive. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339122 / Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering, 2008

Made available in DSpace on 2014-06-11T19:32:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-10-19Bitstream added on 2014-06-13T19:03:38Z : No. of bitstreams: 1 barroso_cb_dr_jabo.pdf: 424873 bytes, checksum: c11fcf246d6ada6dcb329194e9814468 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Devido a baixa disponibilidade de P no solo e a alta capacidade do fungo Aspergillus niger F111 em solubilizar fosfatos inorgânicos, este trabalho teve por objetivo geral avaliar a possibilidade de inocular no solo esporos ou pellets imobilizados com vista a prolongar sua habilidade de solubilização e averiguar o mecanismo de solubilização de fosfatos inorgânicos de Ca, Al e Fe por este fungo. Os pellets inoculados em meio de cultura agitado proporcionaram maior solubilização dos fosfatos, principalmente o fosfato de Fe por ser de baixa solubilidade. No solo, os pellets livres e imobilizados promoveram as maiores solubilizações de fosfato de Fe e maior produção de CO2. Avaliando-se o efeito da fonte de N, as seguintes proporções foram obtidas na solubilização dos fosfatos de Ca, glicina > Al, nitrato de amônio > Fe, ácido l-glutâmico. Os açúcares que mais solubilizaram os fosfatos foram manitol, maltose e d-galactose. Dentre os metais somente o FeCl3.6H2O promoveu maior solubilização do fosfato de Fe e os metais FeSO4.7H2O e FeCl3.6H2O promoveram maiores solubilizações do fosfato de Ca. As concentrações de álcoois que mais favoreceram a solubilização do fosfato de Fe foram 3 e 4% de etanol e metanol, para o fosfato de Ca foi 3% de etanol. A combinação dos metais com o metanol, indicou que o metanol foi o principal responsável pela solubilização. Fatores como queda do pH, a maior produção de ácidos e o menor crescimento do fungo influíram neste trabalho, principalmente em relação a solubilização do fosfato de Fe. No solo, os pellets solubilizaram quantidades semelhantes de fosfato de Fe que os esporos imobilizados de A. niger, podendo ser utilizados com vantagem devido a sua facilidade de obtenção. / Considering the low P availability in the soil and the high capability of Aspergillus niger F111 in solubilizing inorganic phosphates, this work aimed to evaluate the possibility of inoculating spores or immobilized pellets in the soil to prolong the solubilization capability and study the solubilization mechanism of inorganic calcium phosphate, aluminum phosphate and iron phosphate by this fungus. Pellets inoculated in culture medium under agitation allowed higher phosphate solubilization, especially iron phosphate, which is low soluble. In the soil, free and immobilized pellets allowed the highest solubilization of iron phosphate and CO2 production. Evaluating the effect of N sources, the following proportions were obtained in the solubilization of calcium phosphates, glycine > Al, ammonium nitrate > Fe, l-glutamic acid. The sugars that most solubilized phosphates were mannitol, maltose and d-galactose. Among the metals, only FeCl3.6H2O promoted higher iron phosphate solubilization, and FeSO4.7H2O and FeCl3.6H2O promoted higher solubilization of calcium phosphate. The alcohol concentrations that most favored iron phosphate solubilization were 3 and 4% of ethanol and methanol, while the highest solubilization of calcium phosphate was reached with 3% ethanol. The combination of metals with methanol indicated this alcohol was mainly responsible for solubilization. Factors as pH decrease, higher acid production and lower A. niger growth influenced the results, especially in the solubilization of iron phosphate. In the soil, pellets and immobilized spores solubilized similar amounts of iron phosphate. Pellets are thus preferable because they are more easily obtained.

FEIJÃO, Alexcyane Rodrigues. Crescimento, trocas gasosas, partição de íons e metabolismo do nitrogênio em plantas de milho submetidas à salinidade e diferentes fontes de N. 2009. 111 f. Dissertação (Mestrado em Bioquímica) - Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2009. / Submitted by JOANA BEZERRA (joanabib@yahoo.com.br) on 2012-12-07T21:46:44Z No. of bitstreams: 1 2009_dis_arfeijao.pdf: 674672 bytes, checksum: 5d66d02c1147abcb46edeb17e2f22ddb (MD5) / Approved for entry into archive by Érica Barros(ericabarros@ufc.br) on 2012-12-11T21:13:25Z (GMT) No. of bitstreams: 1 2009_dis_arfeijao.pdf: 674672 bytes, checksum: 5d66d02c1147abcb46edeb17e2f22ddb (MD5) / Made available in DSpace on 2012-12-11T21:13:25Z (GMT). No. of bitstreams: 1 2009_dis_arfeijao.pdf: 674672 bytes, checksum: 5d66d02c1147abcb46edeb17e2f22ddb (MD5) / This work aimed to study the effect of N source in the growing, gas exchanges, ion partitions and N metabolism in maize plants (Zea mays L.) submitted to salinity. For this, maize seeds were sown in plastic cups with vermiculite and maintained in greenhouse. After that, the seedlings were transferred to a hydroponics culture with N concentration of 6 mM, in the forms of NO3-, NO3-/NH4+ or NH4+. After five days in these conditions, we started the addition of NaCl, which was gradually increased each day by 25 mM until it reaches a final concentration of 100 mM. The harvests were carried out 4, 11 and 18 days after the beginning of the salt treatment. In control conditions, the plants fed with the mixed NO3-/NH4+ were the ones which presented the greatest shoot growth, compared to other N treatments. There was a great growth reduction when the plants were submitted to salinity, but this effect was not influenced by the N source used. Generally, the salinity reduced the stomatal conductance (gs), transpiration (E), photosynthesis (A) and the relation between the intercellular and outercellular CO2 concentration (Ci/Co ) in plants of all N treatments and in different times of harvest. However, in plants fed with NH4+ and after 18 day of salt treatment a great reduction in the gs, A and E and an increase in the Ci/Co ratio were observed. The Na+ contents increased with salinity, despite that, in plants fed with NH4+, these contents were lower than in the other N treatments in salinity conditions. The K+ contents, on the other hand, were reduced by salinity, and the plants fed with the mixed NO3-/ NH4+ and only NH4+ absorbed less K+ than the ones fed only with NO3-, mainly in the leaves and stems of plants after 11 days and in leaves and roots of plants after 18 days of salt stress. This way, there was influence of N source in the Na+/K+ ratio, particularly in roots of plants after 18 days of exposure to salt stress, whose lower increases in this parameter were observed in the plants treated only with NO3-. The greatest increments in the Cl- contents caused by salinity were observed in plants fed with NO3- and with the mixed NO3-/ NH4+. However, in control conditions, these contents were increased in leaves and stems of plants fed only with NH4+. The NO3- contents were higher in plants fed with NO3- and NO3-/NH4+, when compared to the ones fed only with NH4+, both in control and salinity conditions. The greatest and lowest Cl-/NO3- ratio were found, respectively, in plants treated with NO3- and with NH4+. The shoot NH4+ contents were little influenced by salinity or by N source, however, in roots of plants fed with NH4+ and under salinity, there was a great accumulation of these ions after 18 days of stress. The soluble carbohydrates contents, in general, increased by salinity, except in the leaves and stems (after 18 days of salt stress) and in the roots (during all the experimental period) of the plants treated with NH4+. Generally, the soluble proteins and soluble amino acids contents were increased by salinity, and the biggest quantities of these solutes were observed in the roots of plants fed with NH4+ and after 18 days of salt stress. The total N contents were reduced by salinity and it was observed especially in plants fed only with NO3-. In the leaves, the activities of nitrate reductase (NR) and nitrite reductase (NiR) were greater in plants fed with NO3- and with the mixed NO3-/ NH4+. Little influence of salinity in NiR activity was observed in maize leaves. In the leaves, the salinity influenced differently the activity of glutamine synthetase (GS) between the different sources of N and time of salt exposure. However, in the roots, in general, the GS activity increased withy salinity, except for the plants fed with NH4+, which were not influenced by this stress. After 18 days of salt exposure, the GS activity was greater in the plants fed with NH4+, compared to the other N treatments. The activity of glutamate synthase (GOGAT), in the leaves, in generral, increased with salinity, despite that, this activity was reduced in the roots mainly in the plants fed with NO3-, after 4 days, and with NH4+, after 11 and 18 days. These results suggest that the several N sources did not influence the tolerance of maize plants to salinity. However, the plants fed with NO3- had better results in ion relations. And greatest GS activities observed in roots of the plants fed with NH4+, after 18 days of stress, helped in the osmotic adjustment, as a consequence of the accumulation of soluble proteins and soluble amino acids / O objetivo deste trabalho foi estudar o efeito da fonte de N no crescimento, nas trocas gasosas, na partição de íons e no metabolismo do N em plantas de milho (Zea mays L.) submetidas à salinidade. Para isto, sementes de milho foram semeadas em copos plásticos contendo vermiculita, sendo mantidas em casa de vegetação. Em seguida, as plântulas foram transferidas para um meio hidropônico com concentração de N igual a 6 mM, nas formas de NO3-, NO3-/NH4+ ou NH4+. Após cinco dias nestas condições, iniciou-se a adição de NaCl, que foi feita em parcelas de 25 mM por dia, até atingir a concentração final de 100 mM. As coletas foram realizadas aos 4, 11 e 18 dias após o início do tratamento salino. Em condições controle, as plantas nutridas com a mistura NO3-/NH4+ foram as que apresentaram o maior crescimento da parte aérea, em comparação aos demais tratamentos de N. Houve uma forte redução do crescimento quando as plantas foram submetidas à salinidade, mas este efeito foi independente da fonte de N empregada. De maneira geral, a salinidade reduziu a condutância estomática (gs), a transpiração (E), a fotossíntese (A) e a relação entre a concentração interna e externa de CO2 (Ci/Co) das plantas de todos os tratamentos de N e nos diferentes tempos de coleta. Entretanto, nas plantas cultivadas com NH4+ e aos 18 dias do tratamento salino, foram observados uma redução acentuada na gs, A e E e um aumento na relação Ci/Co. Os teores de Na+ aumentaram com a salinidade, contudo, nas plantas nutridas com NH4+, esses teores foram menores do que os dos demais tratamentos de N em condições de salinidade. Os teores de K+, por sua vez, foram reduzidos pela salinidade, sendo que as plantas nutridas com a mistura NO3-/ NH4+ e apenas NH4+ absorveram menos K+ do que as cultivadas apenas com NO3-, principalmente nas folhas e colmos das plantas aos 11 dias e nas folhas e raízes das plantas aos 18 dias de estresse salino. Dessa forma, houve influência da fonte de N na relação Na+/K+, particularmente nas raízes das plantas aos 18 dias de exposição ao estresse salino, cujos menores aumentos nesse parâmetro foram observados nas plantas tratadas apenas com NO3-. Os maiores incrementos nos teores de Cl- causados pela salinidade foram observados nas plantas cultivadas com NO3- e com a mistura NO3-/ NH4+. Porém, em condições controle, esses teores foram aumentados nas folhas e colmos das plantas cultivadas apenas com NH4+. Os teores de NO3- foram maiores nas plantas nutridas com NO3- e NO3-/NH4+, quando comparadas às nutridas somente com NH4+, tanto em condições controle quanto de salinidade. A maior e a menor relação Cl-/NO3- foram encontradas, respectivamente, nas plantas tratadas com NO3- e com NH4+. Os teores de NH4+ da parte aérea foram pouco influenciados pela salinidade ou pela fonte de N, porém, nas raízes das plantas nutridas com NH4+ e sob salinidade, houve um grande acúmulo desses íons aos 18 dias de estresse. Os teores de carboidratos solúveis foram, em geral, aumentados pela salinidade, com exceção nas folhas e colmos (aos 18 dias de estresse salino) e nas raízes (durante todo o período experimental) das plantas tratadas com NH4+. De maneira geral, os teores de proteínas solúveis e de N-aminossolúveis foram aumentados pela salinidade, sendo que as maiores quantidades destes solutos foram observadas nas raízes das plantas tratadas com NH4+ e aos 18 dias de estresse salino. Os teores de N-total foram reduzidos pela salinidade, sendo isto observado especialmente nas plantas nutridas apenas com NO3-. Nas folhas, as atividades da redutase do nitrato (NR) e da redutase do nitrito (NiR) foram maiores nas plantas tratadas com NO3- e com a mistura NO3-/ NH4+. Foi observada pouca influência da salinidade na atividade da NiR das folhas de milho. Nas folhas, a salinidade influenciou diferentemente a atividade da sintetase da glutamina (GS) entre as diferentes fontes de N e tempos de exposição à salinidade. Porém, nas raízes, de maneira geral, a atividade da GS aumentou com a salinidade, com exceção das plantas tratadas com NH4+, que não foram influenciadas por este estresse. Aos 18 dias de exposição à salinidade, a atividade da GS foi maior nas plantas tratadas com NH4+, em comparação com os demais tratamentos de N. A atividade da sintase do glutamato (GOGAT), nas folhas, em geral, aumentou com a salinidade, contudo, nas raízes essa atividade foi reduzida principalmente nas plantas cultivadas com NO3-, aos 4 dias, e com NH4+, aos 11 e 18 dias. Esses resultados sugerem que as diversas fontes de N não influenciaram na tolerância das plantas de milho à salinidade, entretanto as plantas nutridas com NO3- foram melhores nas relações iônicas e as maiores atividades da GS observadas nas raízes das plantas cultivadas com NH4+, aos 18 dias de estresse, ajudaram no ajustamento osmótico, como conseqüência do acúmulo de proteínas solúveis e N-aminossolúveis