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Agave adaptation to aridity is examined, comparing trends among phylads, clines in Deserticolae taxa of Baja California, and variation in A. deserti along an elevational gradient. Agave physiology is reviewed and recent evolutionary scenarios are discussed. Tentative hypotheses predict characteristics of Agave leaves and rosettes in arid climates. A study of bioclimatology in the Vizcaino Region of Baja California follows, aimed at defining aspects of a subtropical arid climate that are relevant to a plant. The Vizcaino Region is described in terms of its physiography, vegetation physiognomy and floristics. Ombrothermic diagrams and juxtaposed graphs relate temperature and rainfall at stations throughout the region. Temperature regimes are compared using the 5th, 25th, 75th, and 95th percentiles of their respective distributions of monthly means, and subregional groups with similar regimes are defined. Conditions when soil moisture is available are examined by segregating 'wet' months with rainfall totals of 5 mm or more. Thermal distributions of wet months are compared with respect to their shapes and to temperatures delimiting the central two-thirds of wet months. Patterns in mean annual precipitation are presented. Variables are derived to estimate stress imposed on plants by drought. Median annual precipitation deficit, defined as the difference between total annual potential evapotranspiration and total annual rainfall, expresses the stress typically experienced by plants. The 90th percentile of potential evapotranspiration of dry intervals estimates the severity of droughts that longer-lived perennials survive. Each derived climate variable shows a different geographic pattern. Variance in leaf measurements from collection sites throughout the range of Agave cerulata is studied with a principal components analysis. Leaf characters associated with the major components of variance together with leaf volume/surface ratios are used as dependent variables in multiple regression equations with climate variables, which are estimated for each collection site. As the precipitation deficit increases, leaf size generally decreases, but where the longest droughts are most stressful, leaves tend to be larger. Leaf volume/surface is coupled with leaf size. When size variables are included in regressions, higher volume/surface is associated with more extreme cold, cooler summers, and warmer winters. Warmer summers, higher precipitation deficits, and more warm-season storms are correlated with higher length/width ratios. Larger basal surfaces occur in conjunction with higher precipitation deficits, warmer temperatures, and less warm-season rainfall.

En el presente trabajo se realizó la determinación químico bromatológico del “aguamiel” de Agave americana L., de la muestra procedente de la provincia de Vilcashuamán, departamento de Ayacucho. Así mismo se realizó la elaboración de néctar de aguamiel, con materia prima proveniente de la misma provincia. En la evaluación químico bromatológico, se obtuvieron los siguientes resultados expresados en g % de muestra fresca: 87.38 de humedad, 0.30 de proteína, 0.01 de grasa, 12.03 de carbohidratos, 0.23 de cenizas, 0.05 de fibra cruda, 0.97 de azúcares reductores, 9.08 de azucares reductores totales (Expresado estos dos últimos en g% de glucosa). Y minerales expresados en mg%: 16.92 de sodio, 21.56 de potasio, 7.41 de magnesio, 9.51 de calcio, 4.20 de fósforo, 0.06 de fierro, 0.07 de zinc y 0.02 de cobre. Vitamina C 14.82 mg%. Se preparó néctar con conservante y néctar sin conservante. De los ensayos preliminares de elaboración de néctar a diferentes valores de pH y grados Brix, tanto con conservante y sin conservante, se eligió la formulación de pH 4.50 y Grados Brix 15.50 por ser la de mayor aceptación en la evaluación sensorial. De la determinación del tiempo de vida útil de néctar mediante la evaluación de los parámetros químicos y sensoriales, durante tres meses; almacenadas a 4°C, temperatura ambiental (aprox. 20 a 22 °C) y 37 °C, se ha obtenido que las temperaturas en las que mejor se conservan ambas formulaciones es a 4 °C y a temperatura ambiente. El néctar con conservante se conserva ligeramente mayor tiempo a comparación de néctar sin conservante. / Presently work was carried out the chemical bromatology study about the aguamiel of Agave americana L, the sample coming from the province Vilcashuaman, department of Ayacucho (Perú). In this work it was also carried out preparation nectar of aguamiel with matter prime coming of the same province. In the chemist bromatology determination, the following results obtained expressed en g% of fresh sample: 87.38 of humidity, 0.30 of totals proteins, 0.01 of fats, 12.03 of carbohydrates, 0.23 of ash, 0.05 of raw fibre, 0.97 of sugars directes reducers (g% glucose), 9.08 of sugars totals reducers (g% glucose). And minerals expressed in mg%: 0.79 of sodium, 14.24 potassium, 7.41 of magnesium, 9.51of calcium, 4.20 of phosphorum, 0.06 of iron, 0.07 of zinc and 0.02 of cupper. Also 14.82 mg% of vitamin C. In this case the nectar prepared with preservative and without preservative. According to the experiments preliminaries of elaboration of nectar to differents values of pH and Brix degrees, with preservative and without preservative, it was selected the formulation of pH 4.50 and Brix degrees 15.50, it was because, it had the best acceptation in the sensorial evaluation. About the time determination of the useful like of the nectar, by means of the evaluation of parameter sensorial and chemical, during three months kept to 4 °C, ambient temperature (approximately 20 to 22 °C) and 37 °C, it has been obtained than the temperatures in which better can conserve both formulations are the 4 °C and ambient temperature. The nectar with preservative it can conserve lightly better than nectar without preservative. / Tesis

En el presente trabajo se realizó la determinación químico bromatológico del “aguamiel” de Agave americana L., de la muestra procedente de la provincia de Vilcashuamán, departamento de Ayacucho. Así mismo se realizó la elaboración de néctar de aguamiel, con materia prima proveniente de la misma provincia. En la evaluación químico bromatológico, se obtuvieron los siguientes resultados expresados en g % de muestra fresca: 87.38 de humedad, 0.30 de proteína, 0.01 de grasa, 12.03 de carbohidratos, 0.23 de cenizas, 0.05 de fibra cruda, 0.97 de azúcares reductores, 9.08 de azucares reductores totales (Expresado estos dos últimos en g% de glucosa). Y minerales expresados en mg%: 16.92 de sodio, 21.56 de potasio, 7.41 de magnesio, 9.51 de calcio, 4.20 de fósforo, 0.06 de fierro, 0.07 de zinc y 0.02 de cobre. Vitamina C 14.82 mg%. Se preparó néctar con conservante y néctar sin conservante. De los ensayos preliminares de elaboración de néctar a diferentes valores de pH y grados Brix, tanto con conservante y sin conservante, se eligió la formulación de pH 4.50 y Grados Brix 15.50 por ser la de mayor aceptación en la evaluación sensorial. De la determinación del tiempo de vida útil de néctar mediante la evaluación de los parámetros químicos y sensoriales, durante tres meses; almacenadas a 4°C, temperatura ambiental (aprox. 20 a 22 °C) y 37 °C, se ha obtenido que las temperaturas en las que mejor se conservan ambas formulaciones es a 4 °C y a temperatura ambiente. El néctar con conservante se conserva ligeramente mayor tiempo a comparación de néctar sin conservante. / Presently work was carried out the chemical bromatology study about the aguamiel of Agave americana L, the sample coming from the province Vilcashuaman, department of Ayacucho (Perú). In this work it was also carried out preparation nectar of aguamiel with matter prime coming of the same province. In the chemist bromatology determination, the following results obtained expressed en g% of fresh sample: 87.38 of humidity, 0.30 of totals proteins, 0.01 of fats, 12.03 of carbohydrates, 0.23 of ash, 0.05 of raw fibre, 0.97 of sugars directes reducers (g% glucose), 9.08 of sugars totals reducers (g% glucose). And minerals expressed in mg%: 0.79 of sodium, 14.24 potassium, 7.41 of magnesium, 9.51of calcium, 4.20 of phosphorum, 0.06 of iron, 0.07 of zinc and 0.02 of cupper. Also 14.82 mg% of vitamin C. In this case the nectar prepared with preservative and without preservative. According to the experiments preliminaries of elaboration of nectar to differents values of pH and Brix degrees, with preservative and without preservative, it was selected the formulation of pH 4.50 and Brix degrees 15.50, it was because, it had the best acceptation in the sensorial evaluation. About the time determination of the useful like of the nectar, by means of the evaluation of parameter sensorial and chemical, during three months kept to 4 °C, ambient temperature (approximately 20 to 22 °C) and 37 °C, it has been obtained than the temperatures in which better can conserve both formulations are the 4 °C and ambient temperature. The nectar with preservative it can conserve lightly better than nectar without preservative.

Material from thesis (PH. D.)--University of Michigan, 1937. / Cover-title. "Paper no. 736 from the Department of Botany and the Botanical Garden of the University of Michigan." "Reprinted from the American Journal of Botany, vol. 31, no. 5 ... May, 1944." "Literature cited": p. 297-298.

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Recently, it was hypothesized that pollinator selectivity for large inflorescences has led to the evolution of monocarpic reproduction in agaves. To test this hypothesis, fruit set and stalk length data were collected for six species of paniculate agaves and two species of spicate agaves. Regression results, for all of the paniculate species and for one species of the spicate agaves, showed no significant correlation between fruit set and stalk length. These results do not support the pollinator selectivity hypothesis. The validity of the assumptions was then examined, utilizing the results from hand pollination, pruning, and tie down experiments. These results imply that factors other than pollinator availability might be important in determining fruit set in agaves. In an effort to determine the relative importance of resource and pollinator limitation to fruit set in Agave chrysantha, three treatments were applied to entire plants: (1) natural pollination, (2) natural and hand pollination, and (3) hand pollination. When fruits were collected, there were no significant differences between percent fruit set for the three treatments, implying that fruit set is not limited by the availability of pollinators. When additional plants were pruned to reduce the total number of flowers by approximately one-half, thereby doubling the amount of resources available to each flower, the percent fruit set was twice that for control plants, implying that percent fruit set is energy limited. It is common for plants that exhibit resource limited fruit set to have relatively low fruit-to-flower ratios. This is surprising, since it appears that the resources expended for production of these "excess flowers" could be allocated to fruit maturation and thereby increase fruit production. Four hypotheses explaining the fruit set in Agave mckelveyana are tested. Results from pruning, bagging, and hand pollination experiments indicate that the apparently "excess flowers" do not contribute to fruit production (female fitness). Additional data on nectar production imply that these flowers act primarily as pollen donors and contribute only to male fitness. The importance of pollen donation (male fitness) in determining fruit set is examined for hermaphroditic, monecious, and dioecious plants.

Reproduction de : Thèse de doctorat : Sciences des agroressources : Toulouse, INPT : 2005. / Titre provenant de l'écran-titre. Bibliogr. 101 réf.

CoordenaÃÃo de AperfeiÃoamento de NÃvel Superior / The present work aims performing a comparative analysis between economic efficiency and competitiveness of the productive chains of Sisal in Brazil and Fique, in Colombia. The Matrix Methodology of Political Analysis (MAP) was used. The informative data to reach the objective were obtained from several public and private institutions based on secondary data supplemented by field information from semi-structured qualitative interviews, conducted with key representatives, directly involved with the productive chains of Sisal and Fique in Brazil and Colombia. The results show the importance in generating employment and income in both cultures, since the soil conditions and climate make other crop impossible. Nowadays, Brazil is the leader of Sisal production in the Americas. Colombia, however, leads the production of Fique in South America. Brazil, with 6% of the world production of natural fiber is the third largest global exporter and Colombia, with 1%, is the tenth. Broadly speaking, the analysis of productive chains, allows us to infer that they have similar structure predominantly in small and medium establishments, allowing us to classify the Fique and the Sisal cultures as a family economy. According to the analysis conducted by MAP, it is possible to conclude that from the 12 indicators which enable the comparison as to efficiency and competitiveness, 8 favor Brazil and 6 Colombia; nevertheless, Colombia is more efficient in private terms and Brazil presents the best performance in social terms; both productive chains have low rates in terms of efficiency and competitiveness what makes them vulnerable to external factors. As to the impact of political taxation and subsidies, it was found that the policy adopted in Brazil distort the economic incentives from the foreign market, causing lower prices than the international ones. On the other hand, the policies in Colombia do not influence the price in a relevant way, possibly due to the high internal consumption. / O presente trabalho teve como objetivo realizar uma anÃlise comparativa entre eficiÃncia e competitividade econÃmica das cadeias produtivas do Sisal no Brasil e Fique na ColÃmbia. Utilizu-se a Metodologia Matriz de AnÃlise de PolÃticas (MAP). As informaÃÃes para atingir o objetivo foram obtidas em diversas instituiÃÃes pÃblicas e privadas baseadas em dados secundÃrios complementados por informaÃÃes de campo obtidas a partir de entrevistas qualitativas semiestruturadas, realizadas com representantes chave, diretamente envolvidos com as cadeias produtivas de Fique e Sisal na ColÃmbia e no Brasil. Os resultados evidenciam a importÃncia que tem as duas culturas na geraÃÃo de emprego e renda, em Ãreas onde as condiÃÃes de solo e clima impossibilitam outros cultivos. Atualmente, o Brasil à o lÃder da produÃÃo de Sisal no continente americano. Por outro lado, a ColÃmbia lidera a produÃÃo de Fique na AmÃrica do Sul; Brasil, com 6% da produÃÃo mundial de fibra em natura à o terceiro maior exportador global e ColÃmbia, com 1% à o dÃcimo. Em termos gerais, a anÃlise das cadeias produtivas, permitem inferir que elas tÃm estruturas semlhantes predominando os estabelecimentos pequenos e medianos, tornado as culturas do fique e do sisal uma atividade de economia familiar. Da anÃlise realizada pela MAP, pode-se concluir que dos 12 indicadores que permitem realizar comparaÃÃes de eficiÃncia e competitividade, 8 favorecem ao Brasil e 6 à ColÃmbia; No entanto, a ColÃmbia Ã, mas eficiente em termos privados e o Brasil apresenta melhor desempenho em termos sociais. Ambas cadeias apresentam Ãndices baixos de eficiÃncia e competitividade o que as torna vulnerÃveis a fatores externos. Quanto ao impacto das polÃticas de taxaÃÃo e subsÃdio, percebeu-se que as polÃticas adotadas no Brasil distorcem os incentivos econÃmicos do mercado externo, ocasionando preÃos e receitas internas inferiores Ãs internacionais. Por outro lado, na ColÃmbia, as polÃticas nÃo influenciam de maneira relevante o preÃo devido, possivelmente, ao alto consumo interno.