No description available.

Graduation date: 1995

An isotopic dilution method was used to test the effects of osmotic potential, (IJ' ,), upon nitrification, ammonification, N-immobilization, and nitrous oxide production rates in soil at solute concentrations encountered in Penoyer soil. A nitrification potential assay was also performed to approximate maximum nitrification rates. Nitrification potential rates in soil slurries exponentially declined in response to decreased osmotic potential. However, nitrification was independent of salt concentration at the ambient NIL+ concentrations of the soil. The differential response was attributed to the variable NIL+ substrate quantities. The effects of osmotic potential were secondary to NIL+ substrate levels in controlling nitrification rates. Ammonification rates declined exponentially as a function of decreased osmotic potential; however, the 33% reductions in ammonification rates were restricted to a range of osmotic potentials between 0 and -500 kPa. Ammonification rates were independent of osmotic potential at potentials between -500 and -1800 kPa. Immobilization rates of both NH/ and N03- declined exponentially as osmotic potential decreased. Absolute rates ofN03- immobilization exceeded those of N~ • by a factor of 4, indicating that under N~+ limited conditions, substantial N03- assimilation occurred. However, the generalization that N~ + is the preferred N source was in fact supported by the data, where immobilization rates relative to the respective pool sizes clearly favored NH4 + assimilation. Nitrous oxide production rates increased linearly as osmotic potential decreased. An NH4 + dependence indicated the evolved N20 was derived from nitrification rather than denitrification.

Joint-head grass (Arthraxon hispidus) is a widespread nonindigenous plant species in the eastern United States. It is observed forming large monodominant patches that impact native and managed grassland systems. With such little understanding of its foundational biology or ecological impacts, leaving land managers desperate for effective control measures to manage A. hispidus invasion. We conducted a series of complementary experiments on six populations of A. hispidus to better understand how environmental factors affect seed germination. Germination is a critical life stage that allows a species to disperse. Freshly harvested seeds germinated effectively within 14 days of imbibition in the dark at 23°C, exhibiting little to no dormancy or influence by light. A pH range of 5 - 10 resulted in ≥ 80% germination, suggesting that pH will not limit colonization in other portions of the United States. Arthaxon hispidus was tolerant to abiotic stressors such as salinity and osmotic potential. The concentration required to limit germination to 50% (LD50) in the populations tested surpassed soil salinity found in the contiguous United States and some tidal systems (Frederick, MD = 354; Lincoln, MO = 354; Williamsburg, VA = 298 mM NaCl). While drought adversely affects A. hispidus germination, the LD50 occurred in moderate to more severe osmotic potentials (Frederick, MD = -0.67; Lincoln, MO = -0.37; Williamsburg, VA = -0.25 MPa) making A. hispidus expansion more likely in wetter years and regions. Constant temperature treatments resulted in germination percentages across a range of temperatures (8 - 37°C), and A. hispidus is well distributed in several major temperature regimes found in the United States. Finally, emergence greatly decreased with burial depth. Emergence occurred at ≥ 43% at 1 - 2 cm, decreasing to 5% at 6 cm, and 0% at 8-cm depths. With adequate soil moisture, a broad range of germination temperatures, and a decreased emergence rate with depth, we believe A. hispidus is unlikely to develop a seed bank. These initial studies on A. hispidus' germination posit a broad range of environmental tolerances; although, it may be limited by other life stages. / Master of Science / Joint-head grass is a non-native invasive plant species commonly found in the eastern United States. It is observed growing in large patches that negatively affect the environment. These effects can include decreasing biodiversity or lowering forage availability which negatively can impact cattle production. To better understand the basic biology of joint-head grass, we decided to harvest seeds to study from several populations in the United States. We tested differences in the populations by examining the different environmental effects on joint-head grass germination. Germination is a critical life stage of invasive plants; therefore, we developed complementary experiments to test the effects of the environment on seed germination. We've determined that germination occurs effectively under the effect of several environmental stressors. Germination occurred under salty (NaCl) conditions which may allow it to establish in tidal systems where brackish water is present. We've also determined that germination occurs effectively ( ≥ 80%) at a pH range from 5 - 10. This will allow joint-head grass to germinate in more basic soils commonly found in the western part of the United States. Further, we tested the moisture requirements for germination to occur, and we've found that it is tolerant to moderate to more severe drought conditions. Joint-head grass is also capable of germinating across a range of temperatures (8-37°C). The United States has well-distributed rainfall and suitable temperatures in large portions of the country. We believe the climate of the United States is well-suited for joint-head grass establishment, and that it may spread more frequently in years with higher precipitation during the growing season. This species potentially poses a threat to both our natural and agricultural systems.

Made available in DSpace on 2014-06-11T19:23:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-26Bitstream added on 2014-06-13T20:49:50Z : No. of bitstreams: 1 souzafilho_prm_me_rcla.pdf: 756070 bytes, checksum: 652b52c110793d21851356ab23905d6a (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Synedrella nodiflora (L.) Gaertn. é uma espécie herbácea daninha da que apresenta a produção de cipselas dimórficas. Os dois morfotipos são: o periférico que possui alas membranáceas e o central que possuem formato lanceolado com pappus cerdoso. Esse trabalho objetiva caracterizar as cipselas dimórficas de S. nodiflora por medição morfométricas, por taxa de embebição e por padrões germinativos; e avaliar o desenvolvimento das plantas originadas das cipselas. As respostas da germinação foram avaliadas por gradientes de temperaturas constantes (10 a 45ºC, com intervalos de 5ºC) e alternadas (20/30°C, 25/35°C e 30/40°C), disponibilidade de água (0,0 a -1,2 MPa, com intervalos de -0,2MPa), qualidade de luz (fotoequilíbrios diferentes) e longevidade no banco de sementes com duração de sete meses. O crescimento das plantas foi analisado para ambos morfotipos sob luz solar direta e sombra em casa de vegetação por 150 dias. O morfotipo central é mais leve, comprido e com pappus mais alongado, promovendo uma vantagem na dispersão ectozoocórica sobre o periférico. Em termos de germinabilidade houve diferença significativa entre eles quando colocados em tratamentos sob escuro contínuo. As cipselas germinam melhor em ambientes que as condições de temperaturas estão entre 25 e 30°C, sob luz solar direta e com grande disponibilidade de água. De modo geral, as cipselas centrais apresentam uma maior taxa de germinação que não é causada por diferenças na embebição. As plantas submetidas à luz solar direta apresentaram rápido desenvolvimento quando comparadas com as plantas que cresceram na sombra, contudo as últimas promoveram uma maior produção de cipselas centrais em comparação as periféricas. S. nodiflora é adaptada a condições de sombra o que determina uma grande distribuição em tais ambientes. / Synedrella nodiflora (L.) Gaertn. is a herbaceous weed species that shows dimorphic cypselas features. The two morphotypes are: the peripheral which has a membranal wing and the central which has lanceolate shape with awned pappus. This works objective is to characterize the S. nodiflora dimorphic cypselas by morphometric measurements, by imbibition rates and by germinative patterns; and evaluate the plant development from cypselas. The germination responses was evaluated by constant (10 to 45°C, with 5°C intervals) and alternated (20/30°C, 25/35°C and 30/40°C) temperature gradients, water availability (0.0 to -1.2 MPa, with -0.2 intervals), light quality (different phytochrome photoequilibrium) and longevity in the seven month seed bank. Plant growth was analyzed for both morphotypes under direct sun light and shade light in a greenhouse for 150 days. The central morphotype was lighter, longer and its pappi were elongated, promoting advantages in ectozoochoric dispersion over peripheral. In terms of germinability there was significant difference between them under continuous dark treatments. The cypselas germinate better in environments which temperature conditions are between 25 and 30°C, under direct sun light and have high water availability. Generally, the central cypselas showed higher germination rates which were not caused by imbibition differences. The plants under direct sun light showed fast development when compared with shade grown plants, although these last ones promoted higher central cypselas production compared to peripheral ones. S. nodiflora is adapted to shade conditions which determine a great distribution in these environments.

Submitted by (lucia.rodrigues@ufrpe.br) on 2016-08-03T14:52:48Z No. of bitstreams: 1 Jose Benjamin Machado Coelho.pdf: 973299 bytes, checksum: eedb2e1f9cf8814fb63a0c3a9a896d70 (MD5) / Made available in DSpace on 2016-08-03T14:52:48Z (GMT). No. of bitstreams: 1 Jose Benjamin Machado Coelho.pdf: 973299 bytes, checksum: eedb2e1f9cf8814fb63a0c3a9a896d70 (MD5) Previous issue date: 2012-02-24 / Salinization of soils is one of the abiotic stresses which most limits the growth and crop productivity. To withstand salt stress, plants have developed complex mechanisms which contribute to the adaptation to osmotic and ionic stresses. The cowpea, as a species adapted to semiarid conditions, can develop in saline environments without great loss. The quantification of the permanent wilting point constitutes an important information for water management in irrigated soils. Some researchers report that the soil permanent wilting point soil varies not only with soil texture, but also with the cultivated plant species. Two experiments carried out in a greenhouse at UFRPE, in Recife (Brazil), aiming to evaluate the effect of salt stress on plant growth, accumulation of organic solutes, water use and leaf osmotic potential, and determine the physiological wilting point of cowpea. The statistical design was completely randomized with a factorial 2 x 4, composed of two soil textures and four levels of soil electrical conductivity (4, 8 and 12 dS m-1 at 25°C, and the control without addition of salt, with five replications, totalizing 40 plots per experiment. Cowpea [Vigna unguiculata L. (Walp.)], cultivar pele de moça, was used as test crop. The results were subjected to analysis of variance and regression, using the statistical program SAEG. It was concluded that the permanent wilting point of cowpea was lower by the physiological method than as determined by Richards chamber; the osmotic potential of cowpea leaves decreases with increasing of soil salinity; soil salinity caused a reduction of plant height, leaf number and shoot dry biomass of cowpea and, the increase on soil salinity resulted in higher levels of proline and total soluble carbohydrates of cowpea. / A salinização de solos é um dos estresses abióticos que mais limita o crescimento e a produtividade das culturas. Para suportar o estresse salino, as plantas têm desenvolvido mecanismos complexos, que contribuem para a adaptação aos estresses osmótico e iônico. O feijão vigna, por ser uma espécie adaptada às condições semiáridas, consegue se desenvolver em ambientes salinizados sem grandes prejuízos. A quantificação do ponto de murcha permanente constitui-se numa importante informação para o manejo da água em solos irrigados. Alguns pesquisadores relatam que o ponto de murcha permanente do solo varia não apenas com a textura do solo, mas também com a espécie vegetal cultivada. Dois experimentos foram conduzidos em casa de vegetação da UFRPE, em Recife-PE (Brasil), com os objetivos de avaliar os efeitos do estresse salino no crescimento, acúmulos de solutos orgânicos, consumo de água e potencial osmótico foliar, bem como determinar o ponto de murcha permanente fisiológico do feijoeiro vigna. O delineamento estatístico utilizado foi o inteiramente casualizado, com arranjo fatorial 2 x 4, composto por: duas texturas de solos e quatro níveis de condutividade elétrica do solo (4, 8 e 12 dS m-1 a 25ºC, além da testemunha sem a adição de sais), com cinco repetições, totalizando 40 parcelas por experimento. Como cultura teste foi utilizada o feijão vigna [Vigna unguiculata L. (Walp.)], cultivar pele de moça. Os resultados foram submetidos à análise de variância e de regressão, através do programa estatístico SAEG. Concluiu-se que o ponto de murcha permanente do feijoeiro vigna é menor no método fisiológico que o determinado na câmara de Richards; o potencial osmótico das folhas do feijoeiro vigna diminui com o aumento da salinidade do solo; a salinidade do solo ocasiona a redução da altura da planta, do número de folhas e da biomassa seca da parte aérea do feijão vigna e, o aumento dos níveis de salinidade no solo proporciona elevação dos teores de prolina e de carboidratos solúveis totais do feijoeiro vigna.

Made available in DSpace on 2016-01-26T18:56:20Z (GMT). No. of bitstreams: 1 PAULO ROBERTO COSTA.pdf: 691880 bytes, checksum: 9c1227e2bd33119238b57603b29f4ca2 (MD5) Previous issue date: 2006-01-30 / The germination decreasing as a water deficit function is a wide spread occurrence in agricultural systems. This assay was divided in two steps. Firstly, the actions of different osmotic in the simulation of water deficit during germination were tested determining what is the most efficient. The second part was done using mannitol to determine the effect of water deficit in soybean of different sizes. In the first navy bean seeds cv 'IAC-Carioca-80-SH' were germinated at different water deficit potentials (zero; -0.6; -1.2 and 1.8 MPa) of mannitol, CaCl2, KCl and NaCl. In the second soybean seeds cv 'IAC-18' classified in sizes 12 and 13 and 'IAC-22' in 12, 13 and 14 were germinated in mannitol solutions with the same potentials used in the first. Experiment were carried out as completely random with four repetitions per treatment. The treatment evaluation was done by germination, first germination counting , vigour classification, hypocotil and shoot length and by shoot and root dry weight. The results showed that KCl and NaCl solutions had also the toxicity effect on the seeds, and they were not recommended as water deficit simulators. In relation to seed size, in higher water deficits the germination was bigger in larger seeds. Germination was less affected in both experiments then the seedling development in the different water potentials. / A diminuição da germinação em função de deficiência hídrica é ocorrência comum em sistemas agrícolas. Este estudo foi subdividido em duas etapas. Na primeira etapa, procurou-se discutir a ação de diferentes osmóticos na simulação de deficiência hídrica na germinação de sementes determinando-se o osmótico mais eficiente. Posteriormente, utilizou-se o osmótico manitol para determinar o efeito da deficiência hídrica em sementes de soja de diferentes tamanhos. No primeiro estudo, sementes de feijão cv. IAC Carioca-80SH foram germinadas em diferentes potenciais osmóticos (zero; -0,6; -1,2 e 1,8 MPa) obtidos com soluções de manitol, CaCl2, KCl e NaCl. No segundo, sementes de soja cv. IAC-18 e IAC-22 , classificadas em peneiras nos tamanhos 12 e 13, e, 12, 13 e 14, respectivamente, foram germinadas em soluções de manitol de concentrações iguais à primeira etapa. Os experimentos foram conduzidos em delineamento inteiramente casualizado com quatro repetições por tratamento. Para avaliação dos tratamentos foram quantificadas a germinação, primeira contagem de germinação, classificação de vigor, comprimento de hipocótilo e raiz e massa seca de parte aérea e raiz. Os resultados indicaram que as soluções de KCl e NaCl, além de funcionarem como reguladores osmóticos, manifestaram toxidez às sementes, não sendo recomendadas, portanto, como simuladores de deficiência hídrica. Quanto ao tamanho de sementes, para ambos os cultivares, em potenciais menores ocorre maior germinação das sementes maiores. A germinação foi menor afetada, em ambos os experimentos, que as avaliações de desenvolvimento de plântula, nos diferentes níveis de potencial.

Made available in DSpace on 2016-07-18T17:51:05Z (GMT). No. of bitstreams: 1 PAULO ROBERTO COSTA.pdf: 691880 bytes, checksum: 9c1227e2bd33119238b57603b29f4ca2 (MD5) Previous issue date: 2006-01-30 / The germination decreasing as a water deficit function is a wide spread occurrence in agricultural systems. This assay was divided in two steps. Firstly, the actions of different osmotic in the simulation of water deficit during germination were tested determining what is the most efficient. The second part was done using mannitol to determine the effect of water deficit in soybean of different sizes. In the first navy bean seeds cv 'IAC-Carioca-80-SH' were germinated at different water deficit potentials (zero; -0.6; -1.2 and 1.8 MPa) of mannitol, CaCl2, KCl and NaCl. In the second soybean seeds cv 'IAC-18' classified in sizes 12 and 13 and 'IAC-22' in 12, 13 and 14 were germinated in mannitol solutions with the same potentials used in the first. Experiment were carried out as completely random with four repetitions per treatment. The treatment evaluation was done by germination, first germination counting , vigour classification, hypocotil and shoot length and by shoot and root dry weight. The results showed that KCl and NaCl solutions had also the toxicity effect on the seeds, and they were not recommended as water deficit simulators. In relation to seed size, in higher water deficits the germination was bigger in larger seeds. Germination was less affected in both experiments then the seedling development in the different water potentials. / A diminuição da germinação em função de deficiência hídrica é ocorrência comum em sistemas agrícolas. Este estudo foi subdividido em duas etapas. Na primeira etapa, procurou-se discutir a ação de diferentes osmóticos na simulação de deficiência hídrica na germinação de sementes determinando-se o osmótico mais eficiente. Posteriormente, utilizou-se o osmótico manitol para determinar o efeito da deficiência hídrica em sementes de soja de diferentes tamanhos. No primeiro estudo, sementes de feijão cv. IAC Carioca-80SH foram germinadas em diferentes potenciais osmóticos (zero; -0,6; -1,2 e 1,8 MPa) obtidos com soluções de manitol, CaCl2, KCl e NaCl. No segundo, sementes de soja cv. IAC-18 e IAC-22 , classificadas em peneiras nos tamanhos 12 e 13, e, 12, 13 e 14, respectivamente, foram germinadas em soluções de manitol de concentrações iguais à primeira etapa. Os experimentos foram conduzidos em delineamento inteiramente casualizado com quatro repetições por tratamento. Para avaliação dos tratamentos foram quantificadas a germinação, primeira contagem de germinação, classificação de vigor, comprimento de hipocótilo e raiz e massa seca de parte aérea e raiz. Os resultados indicaram que as soluções de KCl e NaCl, além de funcionarem como reguladores osmóticos, manifestaram toxidez às sementes, não sendo recomendadas, portanto, como simuladores de deficiência hídrica. Quanto ao tamanho de sementes, para ambos os cultivares, em potenciais menores ocorre maior germinação das sementes maiores. A germinação foi menor afetada, em ambos os experimentos, que as avaliações de desenvolvimento de plântula, nos diferentes níveis de potencial.

Bibliography : leaves 197-209 / 210 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Botany, 1991

Orientador: Massanori Takaki / Banca: Victor José Mendes Cardoso / Banca: Eliana Akie Simabukuro / Resumo: Synedrella nodiflora (L.) Gaertn. é uma espécie herbácea daninha da que apresenta a produção de cipselas dimórficas. Os dois morfotipos são: o periférico que possui alas membranáceas e o central que possuem formato lanceolado com pappus cerdoso. Esse trabalho objetiva caracterizar as cipselas dimórficas de S. nodiflora por medição morfométricas, por taxa de embebição e por padrões germinativos; e avaliar o desenvolvimento das plantas originadas das cipselas. As respostas da germinação foram avaliadas por gradientes de temperaturas constantes (10 a 45ºC, com intervalos de 5ºC) e alternadas (20/30°C, 25/35°C e 30/40°C), disponibilidade de água (0,0 a -1,2 MPa, com intervalos de -0,2MPa), qualidade de luz (fotoequilíbrios diferentes) e longevidade no banco de sementes com duração de sete meses. O crescimento das plantas foi analisado para ambos morfotipos sob luz solar direta e sombra em casa de vegetação por 150 dias. O morfotipo central é mais leve, comprido e com pappus mais alongado, promovendo uma vantagem na dispersão ectozoocórica sobre o periférico. Em termos de germinabilidade houve diferença significativa entre eles quando colocados em tratamentos sob escuro contínuo. As cipselas germinam melhor em ambientes que as condições de temperaturas estão entre 25 e 30°C, sob luz solar direta e com grande disponibilidade de água. De modo geral, as cipselas centrais apresentam uma maior taxa de germinação que não é causada por diferenças na embebição. As plantas submetidas à luz solar direta apresentaram rápido desenvolvimento quando comparadas com as plantas que cresceram na sombra, contudo as últimas promoveram uma maior produção de cipselas centrais em comparação as periféricas. S. nodiflora é adaptada a condições de sombra o que determina uma grande distribuição em tais ambientes. / Abstract: Synedrella nodiflora (L.) Gaertn. is a herbaceous weed species that shows dimorphic cypselas features. The two morphotypes are: the peripheral which has a membranal wing and the central which has lanceolate shape with awned pappus. This works objective is to characterize the S. nodiflora dimorphic cypselas by morphometric measurements, by imbibition rates and by germinative patterns; and evaluate the plant development from cypselas. The germination responses was evaluated by constant (10 to 45°C, with 5°C intervals) and alternated (20/30°C, 25/35°C and 30/40°C) temperature gradients, water availability (0.0 to -1.2 MPa, with -0.2 intervals), light quality (different phytochrome photoequilibrium) and longevity in the seven month seed bank. Plant growth was analyzed for both morphotypes under direct sun light and shade light in a greenhouse for 150 days. The central morphotype was lighter, longer and its pappi were elongated, promoting advantages in ectozoochoric dispersion over peripheral. In terms of germinability there was significant difference between them under continuous dark treatments. The cypselas germinate better in environments which temperature conditions are between 25 and 30°C, under direct sun light and have high water availability. Generally, the central cypselas showed higher germination rates which were not caused by imbibition differences. The plants under direct sun light showed fast development when compared with shade grown plants, although these last ones promoted higher central cypselas production compared to peripheral ones. S. nodiflora is adapted to shade conditions which determine a great distribution in these environments. / Mestre