Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaf 119). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaf 119). Also available on the Internet.

Two aspects of drought resistance were investigated on wet and dry ecotypes of three conifer species: 1) the relative importance of drought avoidance and drought tolerance mechanisms in resisting drought stress was assessed on Douglas-fir (Pseudotsuga menzieseii) and lodgepole pine (Pinus contorta) seedlings, and 2) the effects of drought on root hydraulic conductance and low temperature, on root water flow rates Were assessed on first-year seedlings of Douglas-fir, lodgepole pine and white spruce (Picea glauca). To study drought avoidance, Douglas-fir and lodgepole pine seedlings were grown in sealed containers in wet (522% water content) or dry (318% water content) peat/vermiculite soil in a factorial treatment design. Dry weights, water use, and root length were determined for seedlings at each of five harvests and stomatal conductance and shoot water potentials were measured during the last 12 weeks of the experiment. Lodgepole pine seedlings had greater dry matter production, water use, stomatal conductance and new root length than Douglas-fir seedlings. New root weight of lodgepole pine seedlings exceeded that of Douglas-fir seedlings during the last five weeks of the experiment, and specific root length of new roots was higher for lodgepole pine seedlings throughout the experiment. Douglas-fir seedlings showed higher water use efficiency (WUE) than lodgepole pine seedlings, although water uptake rates per unit of root dry weight showed little difference between species. Soil water treatment influenced specific root length of new roots, water uptake per unit of new root length, and WUE in Douglas-fir seedlings more than in lodgepole pine seedlings. To study drought tolerance, Douglas-fir and lodgepole pine seedlings were grown under drought and well-watered conditions. At each of three harvests a pressure-volume curve was produced for each seedling. Douglas-fir maintained a lower osmotic potential at full saturation [special characters omitted] and lower turgor loss point [special characters omitted] than lodgepole pine under both watering regimes,. Both species had lower [special characters omitted] when drought-stressed. Douglas-fir appears to be a more conservative species, maintaining low stomatal conductance and tolerating drought conditions, whereas lodgepole pine avoids drought by producing large amounts of roots to exploit the soil resource. To study root hydraulic conductance (Lproot) and water flow rates through roots (WFRR), water flow was measured through de-topped roots of Douglas-fir, lodgepole pine, and white spruce seedlings in a pressure chamber. In a drought experiment, seedlings were grown in sandy soil in a greenhouse under drought and well-watered conditions during their first growing season and, in a low temperature experiment, seedlings were grown in sandy soil in growth chambers at 25/20°C (day/night) and 15/10°C, In the drought experiment, water flow through roots was measured at three pressures. No differences in Lproot were found for Douglas-fir and white spruce seedlings grown under the two watering regimes, however, lodgepole pine seedlings had reduced Lproot when grown under drought conditions. Welk watered seedlings of lodgepole pine and white spruce had higher Lpr00t in 1989 than in 1990 whereas Douglas-fir seedlings had the same Lproot in both years. In the low temperature experiment, WFRR was measured at 1.0 MPa and temperatures of 20°C for 24 hours or 20°, 12°, and 4°C for 18, 15, and 15 hours respectively. At 20°C, white spruce seedlings had higher WFRR than the other two species. Lodgepole pine and white spruce seedlings grown in the 1S°/10°C growth chamber had higher WFRR than seedlings grown in the 25°/20°C growth chamber. Water flow rate decreased with temperature in all three species. After correcting for viscosity, all seedlings had lower WFRR with reduced temperature, except for Douglas-fir and white spruce seedlings grown at 15°/10°C which had the same WFRR at 20°C and 12°C. Therefore, Douglas-fir and white spruce seedlings were found to become less sensitive to low temperature (chilling) stress when pre-conditioned at low temperatures. In the drought and low temperature studies, dry weight biomass of white spruce was lowest but white spruce had a greater specific root length than lodgepole pine and Douglas-fir. In the drought study, biomass production in seedlings from wet ecotypes of each species was more reduced when drought-stressed than seedlings from dry ecotypes. / Graduate

Made available in DSpace on 2014-06-11T19:24:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-06-25Bitstream added on 2014-06-13T19:11:15Z : No. of bitstreams: 1 piffer_cr_me_botfca.pdf: 885929 bytes, checksum: 8a690c85db21a182780380b841102d8b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / O presente trabalho teve como objetivo estudar o desenvolvimento do sistema radicular de amaranto (Amaranthus cruentus, variedade BRS Alegria), de milheto (Pennisetum glaucum (L.), variedade BN-2) e de pé de galinha (Eleusine coracana L.) em função de quatro níveis de compactação, caracterizados pelas densidades de 1,21; 1,31; 1,41 e 1,51 Mg.m-3 em duas classes de solo, classificados como Latossolo Vermelho Distrófico e Nitossolo Vermelho Distroférrico. O experimento foi conduzido no campo da Faculdade de Ciências Agronômicas - UNESP, Campus de Botucatu/SP, durante os meses de Novembro de 2002 à Fevereiro de 2003, em um delineamento experimental de blocos ao acaso com quatro repetições em arranjo fatorial de 2 x 3 x 4. Os vasos foram montados com quatro anéis de PVC sobrepostos, com diâmetro interno de 19,5 cm, totalizando 40 cm de altura. Estes comportaram um volume de 12,56 litros de solo, sendo que somente um anel foi compactado, correspondendo à profundidade de 10 a 20 cm. Os vasos, assim montados, foram enterrados a 40 cm de profundidade, encerrando-se o experimento na fase da inflorescência de cada cultura. A seguir, determinou-se o comprimento radicular, volume radicular, diâmetro radicular, massa seca radicular, bem como a massa seca e altura das partes aéreas das plantas. Os dados obtidos foram submetidos à análise de variância com teste de Tukey a 5 % de probabilidade para comparar as médias. Os resultados mostraram que o pé de galinha apresentou, em relação ao amaranto e ao milheto, o sistema radicular com maior comprimento, volume e massa seca, penetrando nas camadas compactadas dos solos até a densidade 1,41 Mg.m-3, aumentando, desta forma, a aeração dos solos e incorporando a matéria orgânica em profundidade; o milheto proporcionou maior quantidade de massa seca na parte aérea em ambos os solos, mostrando... / This paper aimed to study the development of root system of amaranth (Amaranthus cruentus, BRS Alegria variety), milhet (Pennisetum glaucum (L.) BN-2 variety) and pé de galinha (Eleusine coracana L.) according to four density levels of soil compaction, characterized by 1,21; 1,31; 1,41 and 1,51 Mg.m-3 densities within two soil types, classified as Distrofic Red Latosoil and Distroferic Red Nitosoil. The experiment was carried out at Faculdade de Ciências Agronômicas - UNESP - Botucatu/SP, from November 2002 to February 2003, in a randomized block experimental design with four repetitions and 2 x 3 x 4 factorial desing. The pots were assembled with four rings of overlayed PVC tubes, 19,5 cm of inner diameter, summing up 40 cm high, containing 12,56 liters of soil, with only ring compacted at 10 to 20 cm depth. Tubes were assembled and buried at 40 cm depth. The experiment was finished at influorescence phase of each culture. Measurement of root length, root volume, root diameter, root dry matter were measured as well as dry matter and lenght of aerial part of plants. Obtained data were submitted to variance analysis under Tukey's test with 5 % of probability for mean comparison. Results showed that the pé de galinha showed, regarding to amaranth and milhet, root system with longer length, volume and dry matter working in compacted soil layer up to 1,41 Mg.m-3 density increasing soil aeration and incorporating organic matter; milhet showed the highest aumont of dry matter at aerial part in both soils showing to have good characteristic for soil covering, compared to amaranth and pé de galinha; amaranth was sensitive to soil compaction in all the studied densities and variables compared to milhet and pé de galinha; and the Distrophic Red Latosoil showed best easy terms to plants development, to present a lower resistance to root penetration compared to Distropheric Red Nitosoil.

Orientador: Ivany Ferraz Marques Valio / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-10T07:14:10Z (GMT). No. of bitstreams: 1 Frigeri_RenitaBeteroCorrea_D.pdf: 1952747 bytes, checksum: 56334acb7a1f414b02ad8d99c78ee37c (MD5) Previous issue date: 2007 / Resumo: O crescimento de plântulas de espécies arbóreas tropicais, em ambientes com disponibilidade luminosa contrastante, depende de interações entre características morfológicas e fisiológicas. Dentre as várias alterações morfológicas que ocorrem em condições de baixa irradiância, uma é a razão de crescimento entre a raiz e a parte aérea. A razão raiz:parte aérea de plântulas pode ser indicativa de especialização a diferentes ambientes. No geral, quanto mais sombreado o ambiente, maior a alocação de biomassa para as folhas. O aumento da biomassa da parte aérea (folhas e caules) se faz em detrimento da biomassa das raízes. Com o objetivo de verificar os efeitos de diferentes níveis de irradiância na alocação diferencial de fotossintatos, entre a parte aérea e subterrânea de plântulas de algumas espécies arbóreas tropicais, foram analisados o papel dos cotilédones e da região apical do caule e raiz na alocação, o teor de amido e a translocação de compostos de carbono. Plântulas de Copaifera langsdorfii, Dalbergia nigra, Hymenaea courbaril, Myroxylon peruiferum, Peltophorum dubium e Poecilanthe parviflora, consideradas tolerantes ao sombreamento e Bauhinia longifolia, Enterolobium contortisiliquum, Erythrina speciosa, Piptadenia gonoacantha, Senna macranthera e Schizolobium parahyba, consideradas pioneiras, foram crescidas por aproximadamente 2 meses sob 4, 18, 50 e 100 % da irradiância total. O acúmulo de biomassa de todas as espécies estudadas aumentou em resposta ao aumento da disponibilidade luminosa, bem como as taxas de crescimento relativo e a assimilação líquida. Verificou-se, em geral, redução na razão raiz: parte aérea das plântulas sob baixa irradiância. Apesar deste padrão geral, as espécies estudadas variaram quanto à razão raiz:parte aérea. Plântulas de espécies consideradas tolerantes ao sombreamento como Myroxylon peruiferum, Poecilanthe parviflora e Hymenaea courbaril apresentaram pouca alteração na razão raiz:parte aérea entre os diferentes tratamentos. Bauhinia longifolia, Copaifera langsdorfii, Erythrina speciosa, Enterolobium contortisiliquum e Piptadenia gonoacantha destacaram-se pelas altas razões raiz:parte aérea sob altas irradiâncias. A remoção dos cotilédones das plântulas, da maioria das espécies estudadas, resultou em redução da biomassa total. No geral, não houve diferença significativa na fração de biomassa alocada ao caule, às raízes e às folhas e na razão raiz:parte aérea, com a remoção dos cotilédones. O acúmulo relativo de amido nas folhas não pareceu associado ao decréscimo na partição de biomassa para as raízes, nas plântulas das espécies analisadas. Plântulas de Erythrina speciosa, que pouco diferiram neste aspecto quando mantidas a 2 e 50 % da irradiância, apresentaram a maior alteração na razão raiz:parte aérea. Plântulas de Poecilanthe parviflora, que não alteraram significativamente a distribuição de massa seca entre raiz e parte aérea, diferiram significativamente quanto ao acúmulo relativo de amido nas duas irradiâncias. Aparentemente, a remoção parcial dos diferentes órgãos contribuiu pouco para a redução da biomassa total. No geral, as plântulas das espécies analisadas revelaram um crescimento compensatório em resposta à remoção, tanto sob baixa quanto alta irradiância. A razão raiz:parte aérea não foi alterada em relação às plântulas intactas. A avaliação da distribuição de compostos com carbono radioativamente marcados demonstrou que a direção do movimento dos assimilados nas plântulas de Erythrina speciosa, Poecilanthe parviflora e Enterolobium contortisiliquum, após 48 horas de aplicação, deu-se no sentido da folha aplicada para o caule e em menor proporção para a raiz, exceto em plântulas de Hymenaea courbaril que retiveram quase a totalidade de assimilados na folha aplicada. No geral, não se observou uma diferença marcante em termos de movimento de assimilados, em plântulas mantidas a 2 e 50 % da irradiância. Em resumo, as espécies consideradas pioneiras apresentaram mudanças morfológicas e fisiológicas mais amplas, revelando grande plasticidade e habilidade em adaptar-se às variadas intensidades luminosas a que foram submetidas, em relação às espécies secundárias que revelaram baixa plasticidade fenotípica, a qual geralmente está associada à tolerância ao sombreamento. Entretanto, verificou-se a existência de espécies com respostas intermediárias e variáveis em relação aos parâmetros analisados / Abstract: The growth of seedlings of rain-forest tree species, in environments with contrasting light availability depends on the interaction between morphological and physiological characteristics. Among the various morphological alterations which occur in low-irradiance conditions, one of them is the ratio of growth between the root and shoot. The root: shoot ratio of seedlings can be suggestive to specialization to different environments. In general, the more shadowed the environment is, bigger is the biomass allocation on the leaves. The increase of biomass on the leaf area (leaves and stalk) occurs due to biomass detriment on the roots. Aiming to verify the different radiation level effects in the differential allocation of photosynthates between the root and the shoot of seedlings from some rain-forest tree species, the role of cotyledons and the apical region in the stalk and root in the allocation, the starch tenor and the translocation of carbon compounds radiolabelled. Seedlings of Copaifera langsdorfii, Dalbergia nigra, Hymenaea courbaril, Myroxylon peruiferum, Peltophorum dubium e Poecilanthe parviflora, considered shade tolerant and Bauhinia longifolia, Enterolobium contortisiliquum, Erythrina speciosa, Piptadenia gonoacantha,, Senna macranthera e Schizolobium parahyba, considered pioneers, were grown for approximately two months under 4, 18, 50 and 100 % of total irradiance. The biomass accumulation increased in all the studied species in response to light availability increase as well as the relative growth rate and net assimilation rate. In general, it was observed a reduction in the root:shoot ratio of seedlings under low irradiance. Despite this general pattern, the studied species varied regarding the root:shoot ratio. Seedlings of species considered shading tolerant as Myroxylon peruiferum, Poecilanthe parviflora e Hymenaea courbaril did not present a significant change in the root: shoot ratio. Bauhinia longifolia, Copaifera langsdorfii, Erythrina speciosa, Enterolobium contortisiliquum e Piptadenia gonoacantha contrasted due to high root: shoot ratio under high irradiance. The removal of cotyledons from the seedlings, in most of the studied species, resulted in reduction of the total biomass. Generally, there was not significant difference in the biomass portion allocated in the stalk, in the root and in the leaves and in the root:shoot ratio, with the removal of cotyledons. The accumulation of starch in the leaves did not seem associated to the decrease of biomass partitioning to the seedlings roots in the analyzed species. Seedlings of Erythrina speciosa which little differed in this aspect when put under 2 and 50% of irradiance, presented a higher alteration in the root: shoot ratio. Seedlings of Poecilanthe parviflora, which did not alter significantly the distribution of dry mass between root and shoot, differed significantly in the relative accumulate of starch in both irradiance. Apparently, the partial removal of these different organs little contributed for the total biomass reduction. In general, the analyzed seedling species, revealed compensatory growth in response to removal, either under low or high irradiance. The root:shoot ratio was not altered compared to the intact seedlings. The analyses of distribution of carbon compounds radioactively marked, showed that the moving direction of the assimilate in the seedlings of Erythrina speciosa, Poecilanthe parviflora e Enterolobium contortisiliquum, after 48 hours of application, occurred in the application leaf to stalk way also in lower portion to the root except in seedlings of Hymenaea courbaril which retained almost all the assimilate in the applied leaf. In an overall, a distinct difference was not observed in assimilates flow in seedlings put under 2 to 50 % of irradiance. Altogether, the species considered pioneers presented more ample morphological and physiological changes, revealing great plasticity and ability in adapting to various light intensities which they were submitted. In relation to the secondary species which revealed low phenotypical plasticity to which is generally associated with shadow tolerating therefore, there was found the existence of species with intermediate variable according to the analyzed parameters / Doutorado / Doutor em Biologia Vegetal

Orientador: Simone L. Kirszenzaft Shepherd / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-06T01:33:54Z (GMT). No. of bitstreams: 1 Gomes_MarciaAparecidaNovaes_D.pdf: 2698134 bytes, checksum: 2482e20d3a6cf3447826fb16c66c4c7c (MD5) Previous issue date: 2006 / Resumo: Sinningia allagophylla (Gesneriaceae) é uma herbácea perene amplamente distribuída no Brasil, encontrada principalmente em formações campestres do Cerrado, bem como em alguns afloramentos rochosos da Mata Atlântica, crescendo, assim, em ambiente inóspito (sujeito à seca e ao fogo, em solos ácidos, deficientes em nutrientes e com teores elevados de alumínio e de manganês). Como outras espécies do Cerrado, apresenta fases fenológicas bem definidas: no outono as partes aéreas das plantas morrem e o órgão subterrâneo passa por um período de dormência no inverno, seguido por um período de rápida brotação na primavera. É uma espécie com potencial ornamental e o tubérculo que produz possui potencial exploração econômica pelo conteúdo de carboidratos que apresenta. Também é ecologicamente importante como fonte de néctar para beija-flores. Estudos anteriores mostraram que S. allagophylla responde de forma satisfatória ao cultivo in vitro, podendo ser obtido em um curto período um número grande de plantas. Entretanto, em tais estudos as microplantas não produziram o microtubérculo que apresentam in natura e um sistema radicular desenvolvido, estes necessários para a produção de mudas da espécie, disponíveis o ano todo, para a sua comercialização, preservação e para a realização de estudos fisiológicos. Para tanto, foram realizados estudos utilizando-se como explantes segmentos nodais da região mediana do caule de plântulas, estas resultantes da germinação in vitro de sementes da espécie. As sementes foram obtidas a partir de plantas crescidas em área de Campo Cerrado (solos com valor de pH 3,9, com baixos teores de nutrientes e altos para alumínio trocável), da Reserva Biológica e Estação Experimental de Moji-Guaçu (22° 15-16¿S e 47° 8-12¿ W, 585 ¿635 m de altitude), SP. Investigações in vitro de vários aspectos da presença de alumínio no cultivo de S.allagophylla, bem como do enraizamento e da tuberização, resultaram três experimentos, estes realizados com explantes cultivados em meio líquido ½ B5, com valor de pH 4,6 e fotoperíodo de 16 h. No primeiro experimento verificou-se o efeito da concentração de sacarose e de diferentes temperaturas na produção de raízes adventícias e de microtubérculos. No segundo experimento procurou-se obter uma melhor produção de microtubérculos pelas microplantas, tendo sido testados os efeitos do regulador de crescimento ANA e da intensidade luminosa. Já no terceiro experimento foram avaliadas as respostas da espécie ao estresse do alumínio, bem como para a deficiência de nutrientes e baixo valor do pH. Os resultados obtidos foram: (a) maior concentração de sacarose (40 g/kg) que a usada no meio padrão MS (30 g/kg) promoveu a produção de raízes adventícias em S. allagophylla; (b) a temperatura de 25 ± 2°C no período de luz e 20 ± 2°C no período de escuro apresentou um efeito indutor no crescimento radicular e na produção de microtubérculos pela microplanta; (c) a aclimatação bem sucedida ocorreu apenas nas microplantas apresentando microtubérculos com diâmetro aproximado de 8,0 mm, num período de cultivo de pelo menos 120 dias; (d) A presença do regulador de crescimento ANA, suplementado ao meio de cultivo, foi tóxico, induzindo a formação de calo na base da microplanta e de clorose nas folhas; (e) a mistura de luz fluorescente com incandescente (F+I) induziu a produção de microtubérculos e estes com diâmetro maior; (f) o efeito do alumínio sobre o crescimento da microplanta dependeu da concentração testada: em 200 µM ocorreu clorose nas folhas e necrose nas extremidades das raízes, cessando o crescimento das microplantas; em 100 µM não ocorreram sintomas de toxicidade, o crescimento das microplantas não foi prejudicado e, ao contrário, ocorreu um crescimento significativamente maior do diâmetro do microtubérculo e uma tendência, em nível não significativo, de maior crescimento do sistema radicular; (g) as análises químicas da parte aérea das microplantas revelaram um acúmulo de alumínio e de manganês, em mais de 1000 mg/kg e de 300 mg/kg, respectivamente, não apresentando deficiência dos demais nutrientes e (h) com o aumento da concentração de alumínio no meio, de 50 µM para 100 µM, ocorreu um maior acúmulo, tanto de alumínio como de manganês, na parte aérea das microplantas. Os resultados obtidos permitiram a elaboração de um protocolo de micropropagação para S. allagophylla, o qual torna possível a produção de mudas homogêneas da espécie. Também, demonstrou que S. allagophylla é uma espécie acumuladora de alumínio e de manganês e é eficiente na absorção dos nutrientes presentes em substratos com deficiências minerais, com baixo valor do pH e com alumínio disponível. A espécie apresenta, assim, estratégias que permitem a sua sobrevivência nas condições a que está sujeita no bioma Cerrado / Abstract: Sinningia allagophylla (Gesneriaceae) is a perennial herb found throughout Brazil, found mainly in the Cerrado, and also in rocky outcrops within the Atlantic forest, growing in environments subject to drought, fire and soils with low pH, deficient in nutrients and with high aluminium and manganese saturation. As other plants of the Cerrado, it is characterized by well defined phenological phases: in autumn, the aerial parts of the plants die and the underground organs remain dormant throughout winter, followed by a rapid sprouting period at the beginning of spring. The species presents ornamental potential and possesses a tuber with potential use for economic exploitation due to the carbohydrates content present and it is ecologically important as nectar source for hummingbirds. Earlier studies showed that in vitro propagation of S. allagophylla is successful, with rapid propagation of plants. However, the formation of adventitious roots and microtuber is difficult but necessary for seedling production, including commercial production, preservation and for ecophysiological studies. Therefore, studies were developed using nodal segment explants, obtained the germination of in vitro seedlings. The seeds were collected from plants growing in ¿campo cerrado¿ (soil with pH 3,9, low nutrient availability and high aluminium content), of the Reserva Biológica e Estação Experimental de Moji-Guaçu (22° 15-16¿ S e 47° 8-2¿ W, 585 ¿ 635 m of altitude), SP, Brazil. Research of various aspects of rooting, microtuber induction and interface of aluminium presence in vitro cultivation was wade in S. allagophylla. From those results, three experiments were performed with explants cultivated in liquid ½ B5 medium with pH 4,6 and under 16 h photoperiod. The first experiment examined the effect of sucrose concentration and different temperatures on adventitious roots and microtubers production. The second experiment aimed to improve microtubers production, by testing the effects of the growth regulator ANA and light intensity. In the third experiment responses of the species to aluminum stress, as well as nutrient deficiency and low pH condition were tested. The results show that: (a) higher sucrose concentration (40 g/kg) than the standard MS medium (30 g/kg) optimized in vitro adventitious roots production; (b) temperature of 25 ± 2°C in the light period and 20 ± 2°C in the dark period induced rooting and microtubers formation in vitro; (c) successful acclimatization occurred in microplants that produced microtubers with diameters around 8.0 mm, for a cultivation period of at least 120 days; (d) the growth regulator ANA, when inoculated to the medium was toxic, inducing callus formation in the base of the microplant and chlorosis in the leaves; (e) mixture of fluorescent with incandescent light (F+I) induced microtuber production, and stimulated larger diameters of these; (f) aluminium effect depended on the concentration: 200 µM was toxic, causing foliar chlorosis and root necrosis, ceasing the growth of microplants; while 100 µM did not produce toxic symptoms; in fact, there was a significant positive effect on the growth of microtubers (larger diameter) and in larger rooting, but not to a significant statistical level (g) chemical analysis of the aerial part of the microplants revealed aluminium and manganese accumulation, in more than 1000 mg/kg and 300 mg/kg, respectively, without any deficiency in concentrations of other nutrients and (h) the increase of concentration of aluminium in the medium, from 50 mM to 100mM, resulted in a higher aluminium and manganese accumulation in aerial part of microplants. These in vitro studies allowed the elaboration of a protocol for in vitro propagation of S. allagophylla that makes possible the production of homogeneous seedlings of the species. Besides demonstrated that S. allagophylla is an aluminium and manganese accumulator and efficient in absorbing of the nutrients present in a substratum poor in these, with low pH values and considerable aluminium concentration. Therefore it is a species with strategies that allow its survival in Cerrado conditions / Doutorado / Doutor em Biologia Vegetal

No description available.

South Africa has the highest species diversity of ericaceous plants belonging to the Erica genus. There are over 850 identified species in the Cape Floral Region. The Albany Centre of Endemism (ACOE) is located within this region and is a hotspot of diversity consisting of various plant genera. The success of Erica plants is ubiquitously attributed to mycorrhizal relationships they engage in with a diverse group of fungi. This symbiosis is known as the ericoid mycorrhizal (ERM) association. The overall aim of this study was to establish the diversity of root fungi associated with Erica plants using morphological, molecular and 454 pyrosequencing techniques. Six Erica species were identified using leaf and flower morphology according to taxonomic keys. The identified plants were Erica cerinthoides, Erica demissa, Erica chamissonis, Erica glumiflora, Erica caffra and Erica nemorosa. Roots from sampled plants were stained and examined microscopically to determine their mycorrhizal status. Ericoid mycorrhizal associations together with dark septate endophyte (DSE) structures and hyphae that did not form any specific structure were observed in all the roots. In addition arbuscular mycorrhizal (AM) structures in the form of vesicles were detected in E. glumiflora and E. cerinthoides. In order to identify the culturable fungi associated with the respective hosts, sterilised roots were placed on various culture media for cultivation. Thereafter isolated fungi were morphologically classified into 67 morphotypes. These were mostly sterile and darkly pigmented. Non-sporulating mycelia of variable colouration such as white, cream-yellowish, beige, green and brown were also observed. Further identification was carried out using molecular techniques. DNA was extracted separately from pure cultures and amplified using ITS1 and ITS4 primers in a polymerase chain reaction (PCR). Thereafter sequencing and Basic Local Alignment Search Tool (BLAST) were used to identify the isolates to generic level. The fungi were taxonomically classified into 54 operational taxonomic units and 94 percent were Ascomycetes and Helotiales was the dominant order. Unclassified Helotiales with affinities to fungi currently identified as Epacrid root fungus was common in all hosts. Other isolates that were identified included Oidiodendron, Meliniomyces, Phialocephala, Cadophora, Lachnum, Leohumicola Cryptosporiopsis, Chaetomium, Acremonium and Epicoccum species. Basidiomycetes were represented by two OTUs belonging to the genus Mycena. Four OTUs comprised fungi that had no significant alignments in the reference databases. Direct root DNA extraction together with 454 pyrosequencing was used to detect the diversity of culturable and unculturable fungi associated with the identified hosts. The ITS2 region was targeted for sequencing. Although Ascomycetes remained the dominant phyla, Basidiomycetes were also detected in all host plants. Glomeromycota was present in E. caffra and E. cerinthoides. Helotiales was dominant in all Erica plants with the exception of E. cerinthoides and E. chamissonis which were dominated by the order Chaetothyriales. The OTUs identified to genus level included Epacris pulchella root fungus, Oidiodendron cf. maius, Acremonium implicatum, Leohumicola, Lachnum, Capronia and Mycena species. Culture-based techniques and pyrosequencing detected similar fungal composition comprising Ascomycetes, while, pyrosequencing was able to detect Glomeromycetes and Basidiomycetes.

Athletic field rootzones are often sand-based for improved drainage. Sand-based rootzones may have stability issues if turfgrass is not fully established. Our objective was to use organic amendments to improve the stability of sand-based fields during the turfgrass establishment period and avoid overuse of inorganic materials, which have negative effects. We tested coconut coir, peat and wheat straw at 1% organic material, peat at 2% organic material, and an inorganic stabilizing fiber, StaLok, in the top 10 cm of the rootzone. Surface hardness, volumetric water content, traction, penetration resistance and visual quality were measured 2 to 4 months after construction of the plots. Surface hardness was greatest in the inorganic stabilizer and the wheat straw treatments. The kinetic penetration had no differences between the wheat straw (33.78-51.10 kPa) and the StaLok fibers (34.99-56.23 kPa). Wheat straw could be used to stabilize sand-based fields as an organic alternative to inorganic fibers.

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