The potential role of plant oxygen and sulphide dynamics in die-off events of the tropical seagrass, Thalassia testudinum

1 Oxygen and sulphide dynamics were examined, using microelectrode techniques, in meristems and rhizomes of the seagrass Thalassia testudinum at three different sites in Florida Bay, and in the laboratory, to evaluate the potential role of internal oxygen variability and sulphide invasion in episodes of sudden die-off. The sites differed with respect to shoot density and sediment composition, with an active die-off occurring at only one of the sites. 2 Meristematic oxygen content followed similar diel patterns at all sites with high oxygen content during the day and hyposaturation relative to the water column during the night. Minimum meristematic oxygen content was recorded around sunrise and varied among sites, with values close to zero at the die-off site. 3 Gaseous sulphide was detected within the sediment at all sites but at different concentrations among sites and within the die-off site. Spontaneous invasion of sulphide into Thalassia rhizomes was recorded at low internal oxygen partial pressure during darkness at the die-off site. 4 A laboratory experiment showed that the internal oxygen dynamics depended on light availability, and hence plant photosynthesis, and on the oxygen content of the water column controlling passive oxygen diffusion from water column to leaves and belowground tissues in the dark. 5 Sulphide invasion only occurred at low internal oxygen content, and the rate of invasion was highly dependent on the oxygen supply to roots and rhizomes. Sulphide was slowly depleted from the tissues when high oxygen partial pressures were re-established through leaf photosynthesis. Coexistence of sulphide and oxygen in the tissues and the slow rate of sulphide depletion suggest that sulphide reoxidation is not biologically mediated within the tissues of Thalassia. 6 Our results support the hypothesis that internal oxygen stress, caused by low water column oxygen content or poor plant performance governed by other environmental factors, allows invasion of sulphide and that the internal plant oxygen and sulphide dynamics potentially are key factors in the episodes of sudden die-off in beds of Thalassia testudinum . Root anoxia followed by sulphide invasion may be a more general mechanism determining the growth and survival of other rooted plants in sulphate-rich aquatic environments.

The political economy of poverty alleviation strategies. The initiative for heavily indebted poor countries in Bolivia: More of the same

In the year 2000, approximately 1.1 billion people lived in extreme poverty while developed countries spent US$600 billion a year on defense. The Heavily Indebted Poor Countries (HIPC) Initiative is a recent component of a larger poverty reduction strategy supported by the International Financial Institutions, as well as many developed and developing countries. By implementing lessons of the past fifty years, this program attempts to diminish misery around the globe. As such, it provides debt relief while seeking to enable the poorest countries to simultaneously attain sustainable debt and promote human development. Interest in poverty reduction around the globe reemerged in the 1990s. This study contributes directly to this recent effort by presenting a nuanced approach that builds on the stepping-stones generated by other poverty scholars. To fulfill its goal, this investigation applies a political economy framework. Within this framework, the author conducts an actor-specific analysis. This dissertation addresses the following question: How do domestic and international actors respond to the implementation of poverty alleviation strategies? The author assumes actors desire to maximize their utility calculation and suggests these calculations are based on the player's motivations and external influences. Based on their motivations, the external influences, and the initiative's guidelines, each actor develops a set of expectations. To fulfill those expectations, stake holders utilize one or several strategies. Finally, the actors' ability to achieve their expectations determines each player's assessment of the initiative. The framework described is applied in an in-depth, actor-specific analysis of the HIPC in Bolivia. Bolivia's National Revolution represents the country's first attempt at reducing poverty. Since then, all governments have taken specific steps to combat poverty at the local and national levels. The Initiative for Heavily Indebted Poor Countries (HIPC) is one of the most recent macro strategies of this kind. The case study demonstrated that three factors (national ownership, effective sponsorship and the local context) determine the success levels of poverty reduction strategies from abroad. In addition, the investigation clearly shows that poverty reduction is not the sole motivation in the implementation of poverty alleviation strategies. All actors, however, share the dream of poverty reduction.

Rich and poor, white and black, free and slave: The social history of Cuba's tobacco farmers, 1763--1817

Tobacco was of primary importance to Spain, and its impact on Cuba's economy and society was greater than just the numbers of farms, workers, or production, demonstrated by the Spanish crown's outlay of monies for capital assets, bureaucrats' salaries, and payments to farmers for their crop. This study is a micro- and macro-level study of rural life in colonial Cuba and the interconnected relationships among society, agricultural production, state control, and the island's economic development. ^ By placing Cuba's tobacco farmers at the forefront of this social history, this work revisits and offers alternatives to two prevailing historiographical views of rural Cuba from 1763 (the year Havana returned to Spanish control following the Seven Years' War) to 1817 (the final year of the 100-year royal monopoly on Cuban tobacco). Firstly, it argues against the primacy of sugar over other agricultural crops, a view that has shaped decades of scholarship, and challenges the thesis which maintains the Cuban tobacco farmer was almost exclusively poor, white, and employed free labor, rather than slaves, in the production of their crop. ^ This study establishes the importance of tobacco as an agricultural product, and argues that Cuban tobacco growers were a heterogeneous group, revealing the role that its cultivation may have played in helping some slaves earn their freedom. ^

Characterizing Poor Performance in For-Profit and Not-for-Profit Food Service Operations

In this article the authors explore the performance-related employee behaviors that are the most troublesome in food service. Four subsegments of food service were surveyed and differences in profit and not-for-profit operations analyzed. Significant differences were found between the two groups, with for-profit operations indicating more severe problems in all but one behavior category.

Hypertension, poor glycemic control, and microalbuminuria in Cuban Americans with type 2 diabetes

Purpose: To investigate to what degree the presence of hypertension (HTN) and poor glycemic control (GC) influences the likelihood of having microalbuminuria (MAU) among Cuban Americans with type 2 diabetes (T2D).Methods: A cross-sectional study conducted in Cuban Americans (n = 179) with T2D. Participants were recruited from a randomly generated mailing list purchased from KnowledgeBase Marketing, Inc. Blood pressure (BP) was measured twice and averaged using an adult size cuff. Glycosylated hemoglobin (A1c) levels were measured from whole blood samples with the Roche Tina-quant method. First morning urine samples were collected from each participant to determine MAU by a semiquantitative assay (ImmunoDip).Results: MAU was present in 26% of Cuban Americans with T2D. A significantly higher percentage of subjects with MA had HTN (P = 0.038) and elevated A1C (P = 0.002) than those with normoalbuminuria. Logistic regression analysis showed that after controlling for covariates, subjects with poor GC were 6.76 times more likely to have MAU if they had hypertension compared with those without hypertension (P = 0.004; 95% confidence interval [CI]: 1.83, 23.05). Conclusion: The clinical significance of these findings emphasizes the early detection of MAU in this Hispanic subgroup combined with BP and good GC, which are fundamentals in preventing and treating diabetes complications and improving individuals’ renal and cardiovascular outcomes.