Orientador: Cibele Chalita Martins / Coorientador: Riselane de Lucena Alcântara Bruno / Banca: Ana Regina Pimentel de Almeida / Banca: Roberval Daiton Vieira / Banca: Felipe Batistella Filho / Banca: Rita de Cássia Panizzi / Resumo: A qualidade das sementes é influenciada pelas condições climáticas e fitossanitárias do campo de produção. A identificação das características das melhores áreas produtoras de sementes de forrageiras permite aprimoramento do setor. Assim, a presente pesquisa teve como objetivo identificar características climáticas das regiões produtoras que podem afetar a qualidade física, fisiológica e sanitária de sementes de Brachiaria brizantha cv. BRS Piatã. Foram avaliados 10 lotes de sementes de B. brizantha procedentes dos Estados de São Paulo, Goiás, Bahia, Minas Gerais e Mato Grosso do Sul. Avaliaram-se dois lotes de sementes de cada Estado pelas seguintes determinações: pureza, massa de mil sementes, teor de água, viabilidade pelo teste de tetrazólio, germinação e os testes de vigor de emergência, primeira contagem de emergência de plântulas em areia e emergência das plântulas em campo. Também foi avaliada a qualidade sanitária das sementes pelo método do papel de filtro. Foram obtidos dados de temperatura e precipitação desde o período de florescimento até a colheita das sementes de cada região de produção. As médias dos tratamentos foram comparadas pelo teste de Scott Knott, a 5% de probabilidade. Para discriminar as regiões que produzem lotes de sementes de melhor qualidade e quais fatores ambientais têm influência sobre cada um dos parâmetros de qualidade das sementes aplicou-se a análise estatística multivariada pela Análise de Componentes Principais. Locais de produção com t... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Seed quality is influenced by climatic and phytosanitary conditions of the field of production. The identification of the characteristics of the best forage seed producing areas allows the sector improvement . Thus, this research aimed to identify climatic characteristics of the producing regions that can affect the physical, physiological and sanitary quality of seeds of Brachiaria brizantha cv. BRS Piatã. Ten seed lots of B. brizantha from the states of São Paulo, Goiás, Bahia, Minas Gerais and Mato Grosso do Sul were evaluated. Two seed lots of each state were evaluated by means the following determinations: purity, mass of a thousand seeds, water content, viability by the tetrazolium test, germination and emergence vigor tests, first count of seedling emergence in sand and seedling emergence in the field. The sanitary quality of the seeds was also evaluated by the filter paper method. Temperature and precipitation data were obtained from the flowering period to the harvest of the seeds of each production region. Treatment means were compared by the Scott Knott test at 5% of probability. To discriminate the regions that produce seed lots of better quality and which environmental factors have influence on which parameters of seed quality was applied the multivariate statistical analysis through Principal Component Analysis. Production sites with temperatures above 30 °C during flowering, degrane and harvest are related to the production of lower quality piatã grass seeds. I... (Complete abstract click electronic access below) / Doutor

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Plants regulate many physiological processes in response to adverse environmental stresses. This study focused on the seed germination and seedling establishment stage and investigated the molecular signaling events when abiotic stresses, such as osmotic, water and temperature, were applied. Seeds of Arabidopsis, mutants or wild type, were used to identify the signaling components. Cold-pretreatment (stratification) is widely used to break seed dormancy and improve germination rate. Stratification at 4. significantly broke the seed dormancy of Arabidopsis in wild-type, cyp707a2, sleepy1 and sleepy1/cyp707a2, but not in ga3ox1. Stratification and exogenous ABA treatment strongly enhanced the expression and the activity of a-amylase in the freshly harvested seeds among the wild-type and those mutants, which have relatively high ABA content. Similarly, the expression of RGL2 and ABI5 were also substantially suppressed by stratification. These results suggest that stratification firstly leads to GA biosynthesis and unlocks the inhibition of RGL2 on the expression of a-amylase. Stratification also relieves the inhibition of ABA on the germination process but the inhibition of ABA on seedling development is not affected. We have isolated an Arabidopsis mutant, dsptp1, which is hyposensitive to osmotic stress during seed germination and seedling establishment, indicated by exhibiting higher seed germination rate, lower inhibition in root elongation under osmotic stress, and more tolerance to drought compared with the wild type (Col0) plants. Osmotic stress and drought enhanced AtDsPTP1 expression in seed coats, the bases of rosette leaves and roots. Compared with the wild type, the dsptp1 mutant increased proline accumulation, reduced MDA content and ion leakage, and enhanced antioxidant enzyme activity under osmotic stress. AtDsPTP1 regulated the transcript levels of various dehydration responsive genes, ABA biosynthesis and metabolic enzyme gene under osmotic stress, resulting in reduced accumulation of ABA in dsptp1 mutant plants than wild type in response to osmotic stress. AtDsPTP1 also mediated the ABA signaling pathway under osmotic stress by suppressing the expression of ABI1 and enhancing the expression of the positive regulators ABI3 and ABI5 in ABA signaling. These data suggest that AtDsPTP1 positively regulates ABA accumulation and signaling during seed germination and seedling establishment in Arabidopsis under osmotic stress. To further investigate the regulation mechanism of DsPTP1 in osmotic stress and drought signaling, we analyzed the water holding capacity between wild type and dsptp1 mutant. The dsptp1 mutant exhibited enhanced water holding capacity compared to wild type under osmotic stress resulting from reduced water loss and increased relative water content, which shall contribute the osmotic and drought tolerance. To identify the signaling components, we investigated the activity of MAPKs under osmotic and drought stress and found that the DsPTP1 differentially regulates the activities of MAPK6 and a p38 MAPK, which is inferred as MAPK12 according to its molecular weight in Arabidopsis under osmotic and salt stress. However, there is no direct interaction between DsPTP1 and 20 MAPKs indicated by the results of the of specific interaction test. These results suggest that the differential regulation of MAPK6 and MAPK12 by DsPTP1 is indirect. In addition, we screened the interaction proteins of DsPTP1 under abiotic stress. Seventeen positive clones were acquired from the sequencing results. More work need to be done to confirmed the positive interactions and the signaling cascades. In summary, seed germination and seedling growth are closely regulated by environmental cues. This should be the result of evolutionary selection since successful new growth from the seed embryo depends on the sensitive perception of environmental conditions and effective regulation of many physiological processes that are involved. We have demonstrated that plant hormones, especially ABA, play central regulative roles during such regulations. Many other signaling components, such as protein kinases and phosphatases, are also involved. Identifying the detailed signaling pathways should be the focus of further research.

Made available in DSpace on 2014-06-11T19:28:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-02-22Bitstream added on 2014-06-13T20:58:22Z : No. of bitstreams: 1 iossi_e_me_jabo.pdf: 445691 bytes, checksum: 3b74424d05bb4320fcd1e85fceffe915 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Phoenix roebelenii é uma palmeira com pequeno porte, com desenvolvimento a pleno sol e boa adaptabilidade às condições climáticas brasileiras, fatores que a tornam muito procurada. É uma espécie originária das regiões do norte do Laos e do Vietnã, e do sudoeste da China. Sementes de frutos recém colhidos e secas durante um dia foram utilizadas para o levantamento dos dados biométricos e semeadas em bandejas contendo Sphagnum sp. Algumas plântulas foram fotografadas e esquematizadas, representando as etapas do processo germinativo. A germinação de sementes de P. roebelenii é do tipo remota tubular. Para estudo da germinação e qualidade fisiológica foram desenvolvidos dois experimentos, nos quais foram utilizadas quatro repetições de 25 sementes. No primeiro experimento, avaliou-se o efeito de quatro substratos (esfagno, serragem, areia e vermiculita) associados a cinco temperaturas (20°C, 25°C, 30°C, 35°C e 40°C), conduzido com 8 horas de luz e 16 horas de escuro, em caixas gerbox. Foi utilizado o delineamento inteiramente casualizado, em esquema fatorial 5X4. Na porcentagem de germinação os melhores resultados foram obtidos sob temperatura de 25°C e 30°C em todos os substratos. Para o IVG, os melhores tratamentos foram sob a temperatura de 30°C, utilizando-se esfagno ou areia. No segundo experimento, estudou-se o efeito dos quatro substratos sobre a germinação das sementes, o peso da massa seca e o comprimento das plântulas. Os melhores substratos para a porcentagem de germinação das sementes foram serragem, areia e esfagno, sendo que este último apresentou os melhores resultados para a maioria das características das plântulas avaliadas. / Phoenix roebelenii is a pigmy palm tree, with development to full sun and good adaptability to brazilian climatic conditions, factors that turn it very sought. It's a native of the north of Laos and Vietnam, and in the Southwest of China. Seeds of freshly fruits were dried during one day to obtain the biometric data and seeded in trays containing Sphagnum sp. Some seedlings were photographed and schematized, representing the stages of the germinative process. The seed germination of P. roebelenii is of the tubular remote kind. To study the germination and physiological quality, two experiments were developed with four replications of 25 seeds each one. In the first experiment, the effect of four substratas were evaluated. (Sphagnum sp., sawdust, sand and vermiculite) associated to five temperatures (20°C, 25°C, 30°C, 35°c e 40°C), with 8 hours of light and 16 hours of darkness, in boxes (gerbox). The experimental design used was the complete randomized in a fatorial scheme 5x4. The best results of germination percentage were obtained at 25°C and 30°C in all the substratas. For speed of germination index , the best treatments were obtained at 30°C, being used Sphagnum sp. or sand. In the second experiment, was studied the effect of the same four substratas used before, in the seed germination and seedlings length and dry weight, at environmental condition. For the germination percentage, the best result was obtained with Sphagnum sp., sawdust or sand. However, the best treatments for the most of the seedlings characteristics were obtained using the Sphagnum sp.

Germination ecology of four Epipactis species (E. albensis, E. atrorubens, E. helleborine, E. purpurata) was studied. Habitat preferences of adult plants were analyzed using phytosociological relevés from the Czech Phytosociological Database. A field experiment was carried out to determine course of germination of Epipactis seeds sown in different habitat types. Relationship between ecological preferences and germination ecology, and spatial aspects of seed dispersal and seedling recruitment are discussed.

From Introduction: In 1934 the Government started an active campaign on the eradiction of Jointed Cactus. This plant was causing considerable damage to the farms and commonages of the Eastern Province, and was spreading at an alarming rate. The Officer in Charge of eradication, Mr E. du Toit, was stationed at Grahamstown which is fairly centrally situated in the infested area. In 1935 Dr A. Leemann of the Division of Plant Industry made his headquarters at Rhodes University College.

Spores of Fuligo septica (L.) Weber were studied by light and electron microscopy to determine structural changes during germination. Light microscopic observations indicate that few changes occur prior to protoplast release; however, electron microscopic observations show that a number of changes occur within the protoplast before emergence. An ovoid nucleus becomes irregular and lobed; smooth, cisternal endoplasmic reticulum develops; and concurrent development of dictyosomes and centriole occurs. The dictyosomes and centriole are localized in juxtanuclear sites, and the proximal cylinder of the centriole differentiates into a basal body of a future flagellum. When the spore case ruptures, the inner layer of the wall disappears and the nucleus reverts to its original ovoid form. The protoplast emerges through a wedge-shaped split in the wall and gradually develops into a flagellated cell or, sometimes, a myxamoeba. Simultaneously, contractile and food vacuoles develop, the cisternal endoplasmic reticulum becomes ribosome-coated, and a flagellum develops from the basal body. / Science, Faculty of / Botany, Department of / Graduate

Plant development is an iterative process of organ formation from the primary meristems of the plant. Meristem activity is driven by dynamic transcriptional programs that determine cell fate and identity as cells are displaced trough the meristematic tissue to initiate organ primordia. This regulatory network includes members of the TCP and KNOX family of transcription factors, and integrates external and intrinsic cues to efficiently adapt meristem activity to an ever-changing environment. However, how this integration occurs is not clear yet. DELLA proteins have been proposed to modulate transcriptional circuits in plants in response to environmental signals. Although they do not show DNA binding capacity, DELLAs regulate transcription through physical interaction with a large number of DNA-binding transcription factors and other transcriptional regulators. Given the observed interaction between DELLAs and several members of the TCP family of transcription factors, we have explored the relevance of this interaction in the regulation of primary meristems. We have confirmed that DELLAs interact with members of both Class I and Class II TCPs, and prevent their ability to regulate downstream targets. In the embryonic roots, DELLAs maintain a dormant meristem by impairing TCP14/15-dependent activation of cell-cycle genes. On the other hand, DELLAs participate in the establishment of the shoot apical meristem domain that keeps an indeterminate fate, through the control of KNAT1 gene expression by the TCP2/4-AS1 regulatory module. In summary, this Thesis provides a mechanistic framework to eventually explain environmental regulation of meristem activity. / El desarrollo de las plantas es un proceso iterativo de formación de órganos a partir de los meristemos primarios de la planta. La actividad meristemática está dirigida por programas transcripcionales dinámicos que determinan el destino y la identidad celular conforme las células son desplazadas a través del tejido meristemático para iniciar el primordio del órgano. Esta red regulatoria incluye miembros de las familias de factores de transcripción TCP y KNOX, e integra señales externas e intrínsecas para adaptar eficientemente la actividad meristemática al medio ambiente, siempre cambiante. Sin embargo, la manera en que esta integración ocurre no se ha desvelado todavía. Se ha propuesto que en plantas, las proteínas DELLA modulan los circuitos transcripcionales en respuesta a señales medioambientales. Aunque no muestran capacidad de unión al ADN, las DELLAs regulan la transcripción a través de su interacción física con un gran número de factores de transcripción capaces de unirse al ADN y otros reguladores transcripcionales. Dada la interacción observada entre las DELLA y varios miembros de la familia de factores de transcripción TCP, hemos explorado la relevancia de esta interacción en la regulación de los meristemos primarios. Hemos confirmado que las DELLA interaccionan con miembros de las dos clases de TCPs (Clase I y Clase II) e impiden su capacidad de regular dianas aguas abajo. En la raíz del embrión, las DELLAs mantienen el meristemo durmiente al impedir la activación de los genes de ciclo celular dependiente del módulo TCP14/15. Por otro lado, las DELLAs participan en el establecimiento del meristemo apical del tallo, que mantiene un estado indiferenciado, a través del control el módulo TCP2/4-AS1, el cual regula la expresión del gen KNAT1. En resumen, esta Tesis aporta un marco mecanístico para explicar, con el tiempo, la regulación medioambiental de la actividad meristemática. / El desenvolupament de les plantes consiteix en un procés iteratiu de formació d'órgans a partir dels meristems primaris. L'activitat meristemàtica està diridida per programes transcripcionals dinàmics que determinen el destí i la identitat cel.lular a mesura que les cèl.lules es van allunyant del meristem per formar els primordis d`órgans. Esta xarxa de regulació inclou membres de les famílies de factors de transcripció TCP i KNOX, i integra senyals externes i intrínseques per adaptar d'una manera eficient l'activitat del meristem als canvis del medi ambient. No obstant, no es coneix de quina manera la planta fa esta integració. S'ha proposat que les proteïnes DELLA modulen estes xarxes transcripcionals en resposta a senyals del medi. Estes proteïnes no tenen capacitat d'unir-se a l'ADN, però regulen la transcripció mitjançant la interacció amb factors de transcripció i altres reguladors transcripcionals. Donada la interacció entre les proteïnes DELLA i alguns membres de la família de factors de transcripció TCP, hem explorat la rellevància d'esta interacció a la regulació dels meristems primaris. Hem confirmat que les DELLA interaccionen amb membres de les dos classes de TCPs (Classe I i Classe II) i els impedeixen regular les seues dianes. A l'arrel de l'embrió, les DELLA mantenen el meristem dorment al impedir l'activació de gens del cicle cel.lular depenent del mòdul TCP14/15. Per una altra banda, les DELLA particípen a l'establiment del meristem apical de la tija, al que mantenen en un estat indiferenciat, mitjançant el control del mòdul TCP2/4-AS1, que regula l'expressió de KNAT1. En resum, esta Tesi aporta un marc mecanístic per poder explicar, més endavant, la regulació mediambiental de l'activitat meristemàtica. / Felipo Benavent, A. (2017). Modulation of primary meristem activity by gibberellins through DELLA-TCP interaction in Arabidopsis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/82237 / TESIS

Seven plants native to the moist habitats of the pine savannas, woodlands, and Hillside Bog natural area at the Crosby Arboretum, Picayune, MS, were evaluated under laboratory and nursery conditions to determine seed germination percentage, optimal germination temperature, and the effect of substrates on germination. These native plants include: titi (Cyrilla racemiflora L.), buckwheat tree (Cliftonia monophylla Britt.), flameflower (Macranthera flammea (Bartr.) Pennell), deertongue (Carphephorus odoratissimus (Gmel.) Herb. var. odoratissimus), pink coreopsis (Coreopsis nudata Nutt.), tall ironweed (Vernonia angustifolia Michx.), and swamp bay (Persea palustris (Raf.) Sarg.). Laboratory experimentation concluded with germination and determination of optimal temperature regimes. Tall ironweed had the highest rate of success in the nursery. Black Kow compost had suboptimal performance compared to Sunshine Mix 1 and pine bark / sand under nursery conditions. Several of the species tested had minimal germination and require further research to optimize germination and nursery growth.

Light and electron microscopy were employed to study the encystment and germination processes in Azotobacter. Data obtained from frozen-etched replicas and chemically fixed cells revealed that as encystment occurs, the cells become rounded, and lose their motility.