農林水産研究情報センターで作成したPDFファイルを使用している。

Made available in DSpace on 2016-08-17T18:39:38Z (GMT). No. of bitstreams: 1 3709.pdf: 10453405 bytes, checksum: e58384df9cb0940e97fe5a0f8206ade2 (MD5) Previous issue date: 2011-06-10 / Universidade Federal de Minas Gerais / Mechanical injuries are a major cause of post-harvest losses, since they may cause metabolic and physiological changes in fruit and vegetables. However there are few studies that characterize the state of the tissue after injury and during the reaction of the tissue, which was called "Period of Instability (PI). In this work the objective was to characterize the "Period of Instability (PI) of tomatoes (Solanum lycopersicum L.) and kale leaves (Brassica oleracea v. acephala L.) after harvest, injured by puncture with different diameters. So, it was realized a tissues histological study of and plants water status analysis subjected to injury by puncture with diameters of 1.5 and 3.5 mm. Analysis of the structure of kale leaf and tomato injured tissues was performed using techniques of light microscopy during 9 and 24 days after harvest, respectively. The water status was evaluated by firmness of tomatoes, turgor pressure and firmness of the kale leaves. They were examined for 19 days in tomatoes and for seven days in kale leaves. Healthy tissues of tomatoes 'Carmen' showed uniform arrangement until the 16th day after harvest. In the tomato injured tissues PI there was adherence to the dead cell walls on the healthy cells. Puncture injuries with diameters of 1.5 and 3.5 mm did not change the firmness of tomatoes in 'Carmen' stored at 25°C, but the tomatoes firmness decreased after two days of post-harvest. The healthy leaves of kale showed degradation of cellular structures after nine days of harvest. The injured leaves by puncturing the 1.5 and 3.5 mm exhibited PI with physiological response, characterized by the accumulation of mucilage in the damaged region. Firmness and turgor pressure were not altered in the kale leaves injured stored at 5°C. However, healthy and injured leaves had a water recovery from the first to the second day after harvest, when stored in refrigerator at 5°C. After the water recovery, the treatments have a decreased of firmness and turgor pressure, and the injured groups showed variation in the values of firmness between the fourth and seventh day of post-harvest. / As injúrias mecânicas são a maior causa de perdas pós-colheita, uma vez que podem causar alterações metabólicas e fisiológicas em frutos e hortaliças. No entanto são escassos estudos que caracterizam o estado do tecido logo após a lesão e durante a reação do tecido lesionado, ao qual denominamos Período de Instabilidade (PI). Neste trabalho o objetivo foi caracterizar o Período de Instabilidade (PI) de tomates (Solanum lycopersicum L.) e folhas de couve-manteiga (Brassica oleracea v. acephala L.), após a colheita, submetidos à lesão mecânica por punção com diferentes diâmetros. Para isso foi realizada a análise histológica dos tecidos e um estudo do estado hídrico desses vegetais submetidos a lesão por punção com diâmetros de 1,5 e 3,5mm. A análise da estrutura dos tecidos da folha de couve-manteiga e de tomate lesionados foi realizada por meio de técnicas usuais de microscopia de luz durante 9 e 24 dias após a colheita, respectivamente. A avaliação do estado hídrico foi feita pelo estudo da firmeza de tomates, e da pressão de turgescência celular e firmeza das folhas de couve-manteiga. As medidas foram realizadas durante 19 dias para tomates e sete dias para as folhas de couve-manteiga. Os tecidos sadios de tomates Carmen apresentaram disposição uniforme até o 16° dia após a colheita. Durante o PI nos tecidos lesionados de tomates verificou-se a adesão das paredes celulares mortas às células sadias quatro dias após a colheita. As lesões por punção com diâmetros de 1,5 e 3,5 mm não alteram a firmeza em tomates Carmem armazenados a 25°C, no entanto os tomates apresentam decaimento da firmeza dois dias após a colheita. As folhas sadias de couve-manteiga apresentaram degradação tardia das estruturas celulares, após o 9° dia de colheita. As folhas lesionadas por punção de 1,5 e 3,5mm apresentam PI com resposta fisiológica, caracterizada pelo acúmulo de mucilagem na região danificada. A firmeza e a pressão de turgescência também não são alteradas nas folhas de couvemanteiga lesionadas por punção de 1,5 e 3,5mm, e armazenadas a 5°C. Porém, folhas sadias e lesionadas apresentam recuperação hídrica do primeiro para o segundo dia após a colheita, quando armazenadas em refrigerador a 5°C. Após a recuperação hídrica, todos os tratamentos apresentam diminuição gradativa da firmeza e da turgescência celular, sendo que os grupos das lesões mostram oscilações nos valores de firmeza entre o quarto e sétimo dia após a colheita.

La faible représentation de la biodiversité dans les modèles de végétation a longtemps été un obstacle à la compréhension et à la projection des processus écosystémiques. La forte biodiversité des forêts tropicales, leur rôle clé dans les cycles biogéochimiques globaux, ainsi que leur vulnérabilité aux perturbations anthropiques directes et indirectes, amplifient les difficultés et enjeux de ces questions de recherche. En particulier, l'augmentation prédite de la fréquence et de l'intensité des sécheresses pourrait impacter la structure et composition floristique de ces forêts, comme dors et déjà observé au cours d'expériences naturelles et artificielles. Cette thèse explore ces questions de recherche à travers deux approches complémentaires, de modélisation et de mesures écophysiologiques. Dans le premier chapitre, je décris un simulateur de croissance forestière individu-centré et spatialement-explicite, TROLL, qui intègre les progrès récents en physiologie des plantes. Les processus sont paramétrés à l'aide de traits fonctionnels espèce-spécifiques, pour une forêt tropicale amazonienne. Une régénération forestière est simulée, et validée par des observations faites en Guyane française. La sensibilité du modèle à plusieurs paramètres globaux clés est évaluée. Enfin, l'influence de la variation de la richesse et composition spécifiques sur les propriétés écosystémiques est explorée. La réponse des forêts tropicales à la sécheresse est mal connue, empêchant la représentation pertinente des processus en jeu dans les modèles de végétation. Les chapitres 2 à 5 de cette thèse ont ainsi pour but de documenter la tolérance à la sécheresse et sa diversité dans une forêt amazonienne. Une méthode récente et rapide de détermination d'un trait de tolérance des feuilles à la sécheresse, le potentiel hydrique des feuilles au point de perte de turgescence (ptlp), est validée et utilisée, permettant de quantifier pour la première fois un tel trait de tolérance à la sécheresse dans une forêt amazonienne à l'échelle de la communauté. Ce jeu de données permet l'exploration des déterminants de la tolérance à la sécheresse des feuilles, à travers les espèces d'arbres, les tailles des individus, les stades de succession, les expositions à la lumière, ainsi que les lianes. La variabilité de ptlp observée suggère une large diversité de réponses à la sécheresse au sein des communautés de plantes amazoniennes. Ceci est confirmé par le suivi direct du flux de sève au cours d'une saison sèche sur divers arbres de canopée. Enfin, je discute les implications de ces résultats pour le développement des futurs modèles de végétation. / A great part of uncertainties in our current understanding and projections of the carbon cycle lies in the vegetation compartment. The problem of biodiversity representation in vegetation models has long been an impediment to a detailed understanding of ecosystem processes. The high biodiversity of tropical forests, their disproportionate role in global biogeochemical cycles, together with their vulnerability to direct and indirect anthropogenic perturbations, amplify the relevance of this research challenge. In particular, the predicted increase in drought intensity and frequency in the tropics may impact forest structure and composition, as already observed in natural and artificial experiments. This thesis explores how new advances in modelling and ecophysiology should help improve our understanding of these processes in the future. In the first chapter, I describe an individual-based and spatially-explicit forest growth simulator, TROLL, that integrates recent advances in plant physiology. Processes are linked to species-specific functional traits parameterized for an Amazonian tropical rainforest. This model is used to simulate a forest regeneration, which is validated against observations in French Guiana. Model sensitivity is assessed for a number of key global parameters. Finally, we test the influence of varying the species richness and composition on ecosystem properties. Tropical forest response to drought is not well understood, and this hampers attempts to model these processes. In chapters 2 to 5 I aimed at documenting drought-tolerance and its diversity in an Amazonian forest. A rapid method of determination of a leaf drought tolerance trait, the leaf water potential at turgor loss point (ptlp), was validated and applied to a range of plant species. We established the first community-wide assessment of drought tolerance in an Amazonian forest. These results inform on the drivers and determinants of leaf drought tolerance, across tree species and lianas, tree size, successional stages, light exposition, and seasons. Variability in ptlp among species indicates the potential for a range of species responses to drought within Amazonian forest communities. This is further confirmed by direct monitoring of whole-plant water use on diverse canopy trees during a marked dry season. Finally, I discuss the implications of these results to increase the dialogue between the vegetation modeling community and ecology, to enhance model's predictive ability, and to inform policy choices.

No description available.