No description available.

Four populations of Deschampsia caespitosa (L.) Beauv (a Poaceae species), growing on disturbed and undisturbed sites at Climax, Colorado, were examined for metal tolerances (Zn, Cu, Pb, Al). Root growth assessments on parent plant and offspring material for each population were conducted using nutrient solutions containing elevated levels of Zn, Cu, Pb, or Al. Seed germination and seedling survival tests for each population were conducted on both alpine topsoil and mine spoil material. Evidence is presented that supports the hypothesis that ecotypic variation exists within Deschampsia caespitosa and that this variation has allowed certain Deschampsia populations to become successfully established on alpine mine spoils. Acid mine spoil populations showed significantly less root growth retardation in the presence of zinc, copper or aluminum.

The theme of this thesis is the impact of water deficit on the concentration of proline and electrolyte leakage from representatives of the Panicoideae tribe. The impact of drought on agricultural production in the environment of the Czech Republic is currently an important issue. The exceptionall dry year of 2014/2015 and the associated water deficit in the soil had an impact mainly on the harvest of wide-row crops, including maize. Representatives of the Panicoideae tribe - sorghum and foxtail millet are the most drought-resistance crops in the world. Sorghum and foxtail millet belong to II. group of cereals like maize. Sorghum and foxtail millet show lower transpiration coefficient than maize, they also tolerates less demanding growing conditions and are more resistant to diseases and pests. They also compete with maize in a wide range of applications. It is therefore appropriate to determine how these crops respond to water deficit during their ontogenetic development. For the purposes of this experiment genotypes originating from conditions of temperate climate were selected, this genotypes have a shorter growing season. A short growing season is an important factor in the timing of the harvest of the late sown crops in our climate. The aim of the thesis was to determine and evaluate the impact of water deficit on the concentration of proline and electrolyte leakage in selected genotypes of sorghum and foxtail millet and on the basis of the results to select genotypes with high resistance to water deficit. Based on the aims the following hypotheses were set: to determine whether there are differences in the concentration of proline and electrolyte leakage between selected genotypes depending on the effect of water deficit and whether there are differences in these physiological characteristics in response to water deficit between sorghum and foxtail millet. To fulfill the objectives and evaluation the hypothesis was based on the greenhouse experiment with selected genotypes of sorghum and foxtail millet at the Department of Botany and Plant Physiology in the Czech University of Life Sciences Prague. The experiment included 4 genotypes of the species Sorghum bicolor (L.) Moench. (Sorghum): 1216, 30485, Barnard Red and Ruzrok and one variety of the species Setaria italica (L.) Beauv. (Foxtail millet) Ruberit. A total of 4 variants were designated for the experiment (one control and three under the influence of water deficit in different times). The plants in the control variant were full irrigated throughout the experiment. Variant KS was irrigated for the first 14 days, followed by 10 days without watering and the last 4 days were again irrigated. Plants in variant SK were under the influence of water deficit for the first 10 days of the experiment, then 18 days with watering and the plants in the variant SS were without watering for the first 10 days, for the next 4 days were without watering, then the same pattern was repeated: 10 days without and 4 days with watering. Physiological characteristics were observed in plants in the developmental stages BBCH 14-16. The concentration of proline was determined by measuring the absorbance of the samples formed by the reaction with ninhydrin. Subsequently, the measured values were compared with the calibration curve. To measure the sample absorbance at 520 nm a spectrophotometer Hellios gama (Thermo) was used. Electrolyte leakage on discs made from leafs was measured with electrical conductivity meter GRYF 158 (HB Griffin, Ltd.). The obtained results show that the proline concentration increased in response to water stress, since the highest concentration of proline was detected in plants growing in the most stressed variant of SS (670.13 micrograms) compared with other variants of stress. Plants variant KS (643.85 micrograms) showed a higher accumulation than the proline in variant SK (636.69 micrograms). The highest concentration of proline was measured on a genotype in the variety of sorghum Ruzrok (642.94 micrograms). The lowest content of proline was found in the variety of sorghum 1216 (623.78 micrograms), this value was also the only significant difference from the contents of proline to other genotypes. Which at least partly confirms the proposed hypothesis that there are differences in the content of proline between genotypes. The highest electrolyte leakage cell damage was respectively exhibited in plants from the variant SS (39.56%). Plants of the SK variant showed a higher rate of cell damage (32.95%) than plants from the variant KS (29.88%). The lowest cell damage was exhibited in plants grown under control conditions, which again indicates that damage cells increases in response to water deficit. In this experiment the highest degree of cell damage was found in the variety of sorghum 1216 (29.26%) and lowest cell damage was observed in the variety of sorghum Ruzrok (27.03%). A significant different degree of cell damage appeared only in the variety foxtail millet Ruberit (28.6%), which confirms our hypothesis that there are differences in the electrolyte leakage between sorghum and foxtail millet. The hypotheses were not fully confirmed by the experiment. Nevertheless, on the basis of obtained results we conclude that the least drought-resistance genotype is the 1216 variety and the best adapted to the water deficit was the Ruzrok variety. It also confirmed that the higher proline accumulation may protect the plant against the negative effects of water deficit on the cell membranes, which is then reflected in a reduced electrolyte leakage.

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Biológicas, Departamento de Ecologia, Programa de Pós-Graduação em Ecologia, 2008. / Submitted by Allan Wanick Motta (allan_wanick@hotmail.com) on 2010-03-24T16:26:14Z No. of bitstreams: 1 2009_FelipeSalvoAires.pdf: 772435 bytes, checksum: c19b7839c975acd161c6fc695ecb3ee4 (MD5) / Approved for entry into archive by Daniel Ribeiro(daniel@bce.unb.br) on 2010-04-15T15:06:07Z (GMT) No. of bitstreams: 1 2009_FelipeSalvoAires.pdf: 772435 bytes, checksum: c19b7839c975acd161c6fc695ecb3ee4 (MD5) / Made available in DSpace on 2010-04-15T15:06:07Z (GMT). No. of bitstreams: 1 2009_FelipeSalvoAires.pdf: 772435 bytes, checksum: c19b7839c975acd161c6fc695ecb3ee4 (MD5) Previous issue date: 2009-05 / A conversão de florestas nativas e ecossistemas savânicos em pastagens representa uma parcela cada vez maior e significativa do uso da terra, alterando a cobertura vegetal, a diversidade e os ciclos biogeoquímicos. Para a formação destas pastagens utilizou-se, em sua maioria, gramíneas de origem africana que invadiram áreas naturais. Uma das gramíneas invasoras que tem causado grande impacto na biodiversidade do Cerrado é Melinis minutiflora P. Beauv. (capim-gordura). M. minutiflora não é resistente ao pastejo intensivo, indicando que a remoção da parte aérea produzirá efeito contrário ao esperado para as espécies nativas, que tendem à florescer abundantemente após eventos de corte. Desta forma, o corte sucessivo em áreas invadidas com capim-gordura poderia ser uma ferramenta de manejo no controle desta invasora. Este estudo foi conduzido em duas parcelas de campo sujo invadidas por M. minutiflora na Reserva Ecológica do IBGE, Brasília (DF), entre agosto de 2007 e agosto de 2008. Na primeira parcela não foi aplicado nenhum tratamento (S), e na segunda foi realizado o corte da biomassa aérea (CA) em setembro de 2007 e em julho de 2008, além de semeadura com um coquetel de sementes de gramíneas nativas. Foram determinados: a biomassa aérea e a cobertura vegetal do estrato rasteiro, a densidade de sementes no banco de sementes do solo, e a emergência de plântulas nas áreas de semeadura. A parcela S não apresentou alterações significativas em relação à biomassa e a cobertura vegetal. Entretanto, o banco total de sementes apresentou diminuição de 77%: 1863 sementes/m em setembro de 2007 e 425 sementes/m em junho de 2008. Em 2007, as sementes de M. minutiflora representavam 87% das sementes presentes no banco e em 2008 foi registrada uma diminuição significativa para este componente (188 sementes germinadas/m). As sementes de dicotiledônea apresentaram o mesmo padrão entre setembro de 2007 (200 sementes de germinadas/m) e junho de 2008 (100 sementes germinadas/m). Somente as gramíneas nativas apresentaram um aumento significativo entre as duas coletas: 63 sementes germinadas/m em 2007 e 113 sementes germinadas/m em 2008. O corte em CA foi realizado em setembro de 2007 e, 8 meses após o tratamento, a biomassa aérea recuperou somente 37% do valor inicial (7,1 2,6 Mg/ha). Entretanto, não houve alteração significativa na proporção de cobertura vegetal total. O banco de sementes total apresentou uma diminuição de 54%: 863 sementes/m para 2007 para 400 sementes/m em 2008. A densidade de sementes de capim-gordura diminuiu significativamente entre as duas coletas: de 525 em 2007 para 213 sementes germinadas/m em 2008. As dicotiledôneas não apresentaram diminuição entre setembro de 2007 (175 sementes germinadas/m) e junho de 2008 (100 sementes germinadas/m). Apesar da baixa quantidade de biomassa, o número de sementes de gramíneas nativas não apresentou alterações significativas entre 2007 (75 sementes germinadas/m) e 2008 (38 sementes germinadas/m). As áreas de semeadura não apresentaram diferenças significativas no número total de plântulas emergidas/m em relação às áreas controle. Entretanto, a densidade de plântulas de gramíneas nativas/m nas áreas semeadas foi significativamente maior do que a de plântulas de capim-gordura entre 8 e a 11 quinzena de observação. Foi registrada a presença de Gymnopogon spicatus (Spreng.) Kuntze nas áreas de semeadura, indicando a eficiência do coquetel, já que esta gramínea não existia na parcela CA no início do trabalho. O tratamento de corte, associado à semeadura com o coquetel de sementes de gramíneas nativas, tem se mostrado eficiente em combater o processo de invasão por M. minutiflora, visto que impediu a entrada de novas sementes da espécie invasora, além de estimular a floração de gramíneas nativas e de dicotiledôneas presentes no estrato rasteiro, e aumentar a riqueza de espécies. _________________________________________________________________________________ ABSTRACT / The conversion of native forests and savanna ecosystems into pastures represents a growing and significant part of land use change, modifying plant cover, diversity and biogeochemical cycles. These pastures were formed by using mostly African grasses that invaded natural areas. The Melinis minutiflora P. Beauv. (molasses) are one of the greatest threat to the biodiversity of the Cerrados. M. minutiflora is not resistant to intensive browsing, indicating that the removal of the aerial part, in opposite to native species that abundantly blossom after being cut down, will have a negative effect. Therefore, the successive cutting down in areas invaded with molasses could be a management tool in the controlling this invasive grass. This study was carried out from August 2007 to August 2008 in two sites of campo sujo invaded by M. minutiflora in the Ecological Reserve of IBGE, Brasilia (DF). The first site was the control area, with no treatment (S), in second one the aerial biomass was cut down (CA) in September 2007 and July 2008 and sewed with a mixture of native grasses seeds. Aerial biomass and plant cover of the herbaceous layer, the density of seeds of the bank seed in the ground and the seedlings in the sowing areas, were determined. Site S did not present significant alterations in relation to the biomass and the plant cover. However, the total bank seed presented reduction of 77%:1863 seeds/m in September 2007 and 425 seeds/m in June 2008. In 2007, the seeds of M. minutiflora represented 87% of the seeds in the bank and in 2008 registered a significant reduction for this component (188 germinated seeds/m). The dicots seeds presented the same pattern between September 2007 (200 germinated seeds/m) and June 2008 (100 germinated seeds/m). The native grasses were the only to present a significant increase between the two collections: 63 germinated seeds/m in 2007 and 113 germinated seeds/m in 2008. The cut down was carried out in the site CA in September 2007 and, 8 months later the aerial biomass only recovered 37% of the initial value (7.1 2,6 Mg/ha). However, it did not present significant alteration in the total plant cover ratio. The total bank seed presented a reduction of 54%: 863 seeds/m for 2007 and 400 seeds/m for 2008. There was a significant decrease in the density of molasses seeds between the two collections: from 525 in 2007 to 213 germinated seeds/m in 2008. The dicots did not present reduction between September 2007 (175 germinated seeds/m) and (100 germinated seeds/m) in June 2008. Besides the low amount of biomass, the number of seeds of native grasses did not present significant alterations between 2007 (75 germinated seeds/m) and 2008 (38 germinated seeds/m). The sowing areas did not present significant differences in the total number of seedlings/m in relation to the control one. However, the grass density of native seedlings/m in the sowing areas was significantly greater than seedlings of molasses between 8o and 11o 15-day period. The presence of Gymnopogon spicatus (Spreng.) Kuntze registered in the sowing areas, indicated the efficiency of mixture of seeds, since this grass where not present in site CA at the beginning of the work. The cutting treatment, associate to the sowing of the mixture of native grasses seeds has shown to be efficient in halting the invasive process by M. minutiflora, since it hindered the entrance of new seeds of the invasive species, besides stimulating the budding of native grasses and dicots in the herbaceous layer, and increasing the species richness.