Why some stems are red: cauline anthocyanins shield photosystem II against high light stress

Red-stemmed plants are extremely common, yet the functions of cauline anthocyanins are largely unknown. The possibility that photoabatement by anthocyanins in the periderm reduces the propensity for photoinhibition in cortical chlorenchyma was tested for Cornus stolonifera. Anthocyanins were induced in green stems exposed to full sunlight. PSII quantum yields (ФPSII) and photochemical quenching coefficients were depressed less in red than in green stems, both under a light ramp and after prolonged exposures to saturating white light. These differences were primarily attributable to the attenuation of PAR, especially green/yellow light, by anthocyanins. However, the red internodes also had less chlorophyll and higher carotenoid:chlorophyll ratios than the green, and when the anthocyanic periderm was removed, small differences in the ФPSII of the underlying chlorenchyma were retained. Thus, light screening by cauline anthocyanins is important, but is only part of a set of protective acclimations to high irradiance. Hourly measurements of ФPSII on established trees under natural daylight indicated a possible advantage of red versus green stems under sub-saturating diffuse, but not direct sunlight. To judge the wider applicability of the hypothesis, responses to high light were compared for red and green stems across five further unrelated species. There was a strong, linear, interspecific correlation between photoprotective advantage and anthocyanin concentration differences among red and green internodes. The photoprotective effect appears to be a widespread phenomenon

Simulated reduction in upwelling of tropical oxygen minimum waters in a warmer climate

Waters of the Atlantic and Pacific tropical oxygen minimum zones (OMZs), located in the poorly ventilated shadow zones of their respective ocean basins, reach the sea surface mostly in the eastern boundary and equatorial upwelling regions, thereby providing nutrients sustaining elevated biological productivity. Associated export of sinking organic matter leads to oxygen consumption at depth, and thereby helps to maintain the tropical OMZs. Biogeochemical feedback processes between nutrient-rich OMZ waters and biological production in the upwelling regions and their net impact on the evolution of the OMZs depend on the strengths of the flow pathways connecting OMZs and the upper ocean, because even though water has to be isolated below the mixed layer for some time in order for OMZs to develop, it has to be brought up to the surface mixed layer eventually in order to exchange properties with the atmosphere. Here, we investigate the connections between OMZs and the surface mixed layer, and their sensitivity to global warming with a coupled ocean–atmosphere general circulation model by analyzing the fate of simulated floats released in the OMZs. We find that under present-day climate conditions, on decadal time scales a much larger portion of the model's OMZ waters reaches the surface ocean in the Pacific than in the Atlantic Ocean: within 20 years, 75% in the Pacific and 38% in the Atlantic. When atmospheric CO2 is doubled, the fraction of modeled OMZ waters reaching the upwelling in the same time decreases by about 25% in both oceans. As a consequence, feedback between biogeochemical processes in OMZs and in the surface ocean is likely to be weakened in the future

Crimean-Congo hemorrhagic fever: epidemiological trends and controversies in treatment

Crimean-Congo hemorrhagic fever (CCHF) virus has the widest geographic range of all tick-borne viruses and is endemic in more than 30 countries in Eurasia and Africa. Over the past decade, new foci have emerged or re-emerged in the Balkans and neighboring areas. Here we discuss the factors influencing CCHF incidence and focus on the main issue of the use of ribavirin for treating this infection. Given the dynamics of CCHF emergence in the past decade, development of new anti-viral drugs and a vaccine is urgently needed to treat and prevent this acute, life-threatening disease

Contextualising Apartheid at the End of Empire: Repression, ‘Development’ and the Bantustans

This article examines the global dynamics of late colonialism and how these informed South African apartheid. More specifically, it locates the programmes of mass relocation and bantustan ‘self-government’ that characterised apartheid after 1959 in relation to three key dimensions. Firstly, the article explores the global circulation of idioms of ‘development’ and trusteeship in the first half of the twentieth century and its significance in shaping segregationist policy; secondly, it situates bantustan ‘selfgovernment’ in relation to the history of decolonisation and the partitions and federations that emerged as late colonial solutions; and, thirdly, it locates the tightening of rural village planning in the bantustans after 1960 in relation to the elaboration of anti-colonial liberation struggles, repressive southern African settler politics and the Cold War. It argues that, far from developing policies that were at odds with the global ‘wind of change’, South African apartheid during the 1960s and 1970s reflected much that was characteristic about late colonial strategy