Pigment dynamics and autumn leaf senescence in a New England deciduous forest, eastern USA

The leaves of woody plants at Harvard Forest in Central Massachusetts, USA, changed color during senescence; 70% (62/89) of the woody species examined anatomically contained anthocyanins during senescence. Anthocyanins were not present in summer green leaves, and appeared primarily in the vacuoles of palisade parenchyma cells. Yellow coloration was a result of the unmasking of xanthophyll pigments in senescing chloroplasts. In nine red-senescing species, anthocyanins were not detectable in mature leaves, and were synthesized de novo in senescence, with less than 20 m g cm - 2 of chlorophyll remaining. Xanthophyll concentrations declined in relation to chlorophyll to the same extent in both yellow- and red-leaved taxa. Declines in the maximum photosystem II quantum yield of leaves collected prior to dawn were only slightly less in the red-senescing species, indicating no long-term protective activity. Red-leaved species had significantly greater mass/area and lower chlorophyll a / b ratios during senescence. Nitrogen tissue concentrations in mature and senescent leaves negatively correlated to anthocyanin concentrations in senescent leaves, weak evidence for more efficient nitrogen resorption in anthocyanic species. Shading retarded both chlorophyll loss and anthocyanin production in Cornus alternifolia , Acer rubrum , Acer saccharum , Quercus rubra and Viburnum alnifolium . It promoted chlorophyll loss in yellow-senescing Fagus grandifolia . A reduced red : far-red ratio did not affect this process. Anthocyanins did not increase leaf temperatures in Q. rubra and Vaccinium corymbosum on cold and sunny days. The timing of leaf-fall was remarkably constant from year to year, and the order of senescence of individual species was consistent.

Global Capitalism, Immigrant Labor, and the Struggle for Justice

Around the world borders are militarized, states are stepping up repressive anti-immigrant controls, and native publics are turning immigrants into scapegoats for the spiraling crisis of global capitalism. The massive displacement and primitive accumulation unleashed by free trade agreements and neo-liberal policies, as well as state and “private” violence has resulted in a virtually inexhaustible immigrant labor reserve for the global economy. State controls over immigration and immigrant labor have several functions for the system: 1) state repression and criminalization of undocumented immigration make immigrants vulnerable and deportable and therefore subject to conditions of super-exploitation, super-control and hyper-surveillance; 2) anti-immigrant repressive apparatuses are themselves ever more important sources of accumulation, ranging from private for-profit immigrant detention centers, to the militarization of borders, and the purchase by states of military hardware and systems of surveillance. Immigrant labor is extremely profitable for the transnational corporate economy; 3) the anti-immigrant policies associated with repressive state apparatuses help turn attention away from the crisis of global capitalism among more privileged sectors of the working class and convert immigrant workers into scapegoats for the crisis, thus deflecting attention from the root causes of the crisis and undermining working class unity. This article focuses on structural and historical underpinnings of the phenomenon of immigrant labor in the new global capitalist system and on how the rise of a globally integrated production and financial system, a transnational capitalist class, and transnational state apparatuses, have led to a reorganization of the world market in labor, including deeper reliance on a rapidly expanding reserve army of immigrant labor and a vicious new anti-immigrant politics. It looks at the United States as an illustration of the larger worldwide situation with regard to immigration and immigrant justice. Finally, it explores the rise of an immigrant justice movement around the world, observes the leading role that immigrant workers often play in worker’s struggles and that a mass immigrant rights movement is at the cutting edge of the struggle against transnational corporate exploitation. We call for replacing the whole concept of national citizenship with that of global citizenship as the only rallying cry that can assure justice and equality for all.