Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2017-04-26T18:19:19Z No. of bitstreams: 1 texto completo.pdf: 181029 bytes, checksum: bb60cd42c084c397b198944f508a21cc (MD5) / Made available in DSpace on 2017-04-26T18:19:19Z (GMT). No. of bitstreams: 1 texto completo.pdf: 181029 bytes, checksum: bb60cd42c084c397b198944f508a21cc (MD5) Previous issue date: 2000-11-23 / Coordenadoria de Aperfeiçoamento de Pessoal de Nível Superior / Com a finalidade de estudar a senescência de hastes cortadas de lírio, foram desenvolvidos três experimentos para avaliar os efeitos do estádio de colheita e da utilização de sacarose e STS (tiossulfato de prata) sobre a longevidade e a qualidade de inflorescências de lírio (Lilium longiflorum), variedade Ace. Para isso, botões florais foram colhidos em diferentes estádios de desenvolvimento, tomando-se como base o comprimento do maior botão. Os comprimentos dos botões florais utilizados foram: estádio A- 7+1,0 cm; estádio B- 10+1,0 cm; estádio C- 13+1,0 cm; e estádio D-16+1,0 cm (sendo este último o ponto de colheita recomendado por Nowark e Rudnicki em 1990). As hastes de lírio contendo as inflorescências foram cortadas com 55 cm de comprimento e submetidas a pré-tratamentos com sacarose (0, 5, 10 e 15%) e STS (0 e 1 mM). A longevidade foi favorecida pela colheita antecipada. Hastes não-tratadas apresentaram baixa qualidade das suas flores, bem como diâmetro e vida útil reduzidos. Os pré-tratamentos com sacarose e STS não apresentaram efeito sobre o aumento da longevidade, no entanto favoreceram o aumento do diâmetro e a vida útil da flor. Quando se utilizou o STS em estádios mais jovens (estádios A e B), observou-se efeito fitotóxico caracterizado pelo retorcimento das pétalas e pela redução do percentual de abertura dos botões e dos teores de clorofila. A sacarose foi efetiva na redução dos efeitos fitotóxicos provocados pelo uso de STS. O uso de solução contendo 1 mM de STS e 5% de sacarose possibilitou a colheita antecipada de inflorescências de lírio (estádio B), preservando a qualidade final do produto, o que traz, como grande benefício, aumento da vida pós-colheita, possibilitando maior período de comercialização aos produtores. / With the objective of studying the senescence of cut stems of lily, three experiments were developed to evaluate the effects of the harvest stage and the use of saccharose and STS (silver tiosulphate) on the longevity and quality of lily (Lilium longiflorum), variety Ace, inflorescences. With this purpose, floral buds were collected in different stages of development, based on the length of the bigest bud. The floral bud lengths weree: stage A – 7 ± .1.0 cm; stage B – 10 ± .1.0 cm; stage C – 13 ± .1.0 cm; stage D – 16 ± .1.0 cm (being this last one the harvest point recommended by Nowark and Rudnicki in 1990). The lily stems holding the inflorescences were cut with 55 cm of length and gone through pre-treatments with saccharose (0, 5, 10 and 15%) and STS (0 and 1 mM). Longevity was favored by the advanced harvest. Non-treated stems showed low quality of flowers, as well as reduced diameter and lifespan. The saccharose and STS treatments did not show any effect on the increasing of longevity, however they favored flower diameter and lifespan increase. When STS was used in younger stages (A and B), a phytotoxic effect characterized by petal twisting and reduction of bud blossoming and chlorophyll levels. Saccharose was effective for the reduction of phytotoxic effects caused by the use of STS. The use of solution containing 1 mM STS and 5% saccharose made possible the advanced harvest of lily inflorescences (stage B), keeping the product final quality, bringing about, as a great benefit, a post-harvest life increase, making possible for the commercialization. producers a longer period of commercialization. / Não foram localizados o cpf e o currículo lattes do autor.

La fertilisation chez les plantes dépend de la livraison des cellules spermatiques contenues dans le pollen à l’ovule. Au contact du stigmate, le grain de pollen s’hydrate et forme une protubérance, le tube pollinique, chargé de livrer les noyaux spermatiques à l’ovule. Le tube pollinique est une cellule à croissance rapide, anisotrope et non autotrophe; ainsi tout au long de sa croissance à travers l’apoplaste du tissu pistillaire, le tube pollinique puise ses sources de carbohydrates et de minéraux du pistil. Ces éléments servent à la synthèse des constituants de la paroi qui seront acheminés par des vésicules de sécrétion jusqu’à l’apex du tube. Ce dernier doit aussi résister à des pressions mécaniques pour maintenir sa forme cylindrique et doit répondre à différents signaux directionnels pour pouvoir atteindre l’ovule. Mon projet de doctorat était de comprendre le rôle du cytosquelette dans la croissance anisotrope du tube pollinique et d’identifier les éléments responsables de sa croissance et de son guidage. Le cytosquelette du tube pollinique est composé des microfilaments d’actine et des microtubules. Pour assurer une bonne croissance des tubes polliniques in vitro, les carbohydrates et les éléments de croissance doivent être ajoutés au milieu à des concentrations bien spécifiques. J’ai donc optimisé les conditions de croissance du pollen d’Arabidopsis thaliana et de Camellia japonica qui ont été utilisés avec le pollen de Lilium longiflorum comme modèles pour mes expériences. J’ai développé une méthode rapide et efficace de fixation et de marquage du tube pollinique basée sur la technologie des microondes. J’ai aussi utilisé des outils pharmacologiques, mécaniques et moléculaires couplés à différentes techniques de microscopie pour comprendre le rôle du cytosquelette d’actine lors de la croissance et le tropisme du tube pollinique. J’ai trouvé que le cytosquelette d’actine et plus précisément l’anneau d’actine localisé dans la partie sub-apicale du tube est fortement impliqué dans la croissance et le maintien de l’architecture du tube à travers le contrôle de la livraison des vésicules de sécrétion. J’ai construit une chambre galvanotropique qui peut être montée sur un microscope inversé et qui sert à envoyer des signaux tropistiques bien précis à des tubes polliniques en croissance. J’ai trouvé que les filaments d’actine sont impliqués dans la capacité du tube pollinique à changer de direction. Ce comportement tropistique dépend de la concentration du calcium dans le milieu de croissance et du flux de calcium à travers des canaux calciques. Le gradient de calcium établi dans le tube pollinique affecte l’activité de certaines protéines qui se lient à l’actine et dont le rôle est la réorganisation des filaments d’actine. Parmi ces protéines, il y a celles de dépolymérisation de l’actine (ADF) dont deux spécifiquement exprimées dans le gamétophyte mâle d’Arabidopsis (ADF7 et ADF10). Par marquage avec des proteins fluorescents, j’ai trouvé que l’ADF7 et l’ADF10 ont des expressions différentielles pendant la microsporogenèse et la germination et croissance du tube pollinique et qu’elles partagent entre elles des rôles importants durant ces différents stades. / Fertilization in plants depends on the delivery of the sperm cells in the pollen grain through the pollen tube to the ovule. The pollen tube is a highly anisotropic, fast growing cellular protuberance. Because the pollen tube is non autotrophic, it requires a steady supply of carbohydrates and minerals supplied by the pistil to sustain its growth. These elements serve for the synthesis of cell wall material, delivered to the site of cell wall assembly in secretory vesicles that are transported along the actin cytoskeleton and deposited at the growing apex of the tube. The tube has to resist external deformation forces in order to maintain its cylindrical shape and to respond to various directional signals in order to reach its target. My objectives were to identify the role of the cytoskeleton in the anisotropic growth of the pollen tube and to determine how the tube responds to directional cues. The cytoskeleton in the pollen tube consists of microfilaments and microtubules, both forming long filamentous elements. For in vitro growing pollen tubes, carbohydrates and growth minerals have to be added to the growth medium in specific amounts order to sustain pollen tube growth. I optimized the growth conditions of Arabidopsis thaliana and Camellia japonica pollen tubes which, in addition to pollen from Lilium longiflorum, were used as model species for my experiments. I developed a microwave based, fast and efficient fixation and labelling protocol for pollen tubes. I used pharmacological, mechanical, molecular and microscopical tools to study the role of the cytoskeleton in pollen tube growth and tropism. I found that the actin cytoskeleton, and more specifically the subapical actin fringe, plays an important role in the regulation of pollen tube growth and architecture through the controlled delivery of secretory vesicles to the growing apex. I constructed a galvanotropic chamber that can be mounted on an inverted microscope to induce controlled tropic triggers. I found that the actin cytoskeleton is also involved in the ability of the pollen tube to change its direction. This tropic behaviour was shown to be dependent on the concentration of calcium ions in the growth medium and calcium influx through calcium channels. The cytosolic calcium gradient in the pollen tube regulates the activity of various actin binding proteins that are responsible for remodelling the actin cytoskeleton. Among these proteins are two Arabidopsis gametophyte-specific actin depolymerizing factors (ADFs) that I tagged with two intrinsically fluorescent proteins. I found that ADF7 and ADF10 are differentially expressed during microsporogenesis and pollen tube germination and growth and that they likely divide important functions between them.

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