Joan Anton Barceló

Abscisic Acid Decreases Leaf Na+ Exclusion in Salt-Treated Phaseolus vulgaris L.

Previous results showed that in short-term NaCl-treated beans increased leaf abscisic acid (ABA) concentration was triggered by Na+ but not by Cl-. In this work, the specificity of ABA signaling for Na+ homeostasis was studied by comparing the plant’s responses to solutions that modified accumulation of ABA and/or Na+ uptake and distribution, such as supplemental Ca2+, increased nutrient strength, different isosmotic composition, application of exogenous ABA, fluridone (an ABA inhibitor) and aminooxiacetic acid (AOA, an ethylene inhibitor). After fluridone pretreatment, salt-treated beans had lower Na+ uptake and higher leaf Na+ exclusion capacity than non-pretreated plants. Moreover, Na+ uptake was increased and leaf Na+ exclusion was decreased by AOA and ABA. NaCl and KCl similarly increased leaf ABA and decreased transpiration rates, whereas supplemental Ca2+ and increased strength nutrient solution decreased leaf ABA and leaf Na+. These results show (1) a non-ion-specific increase in ABA that probably signaled the osmotic component of salt, and (2) increased ABA levels that resulted in higher leaf Na+ concentrations due to lower Na+ exclusion or increased root-shoot Na+ translocation.

Synchronous Environmental and Cultural Change in the Emergence of Agricultural Economies 10,000 Years Ago in the Levant

The commonly held belief that the emergence and establishment of farming communities in the Levant was a smooth socio-economic continuum during the Pre-Pottery Neolithic (ca. 12,000-9,000 cal BP) with only rare minor disruptions is challenged by recently obtained evidence from this region. Using a database of archaeological radiocarbon dates and diagnostic material culture records from a series of key sites in the northern Levant we show that the hitherto apparent long-term continuity interpreted as the origins and consolidation of agricultural systems was not linear and uninterrupted. A major cultural discontinuity is observed in the archaeological record around 10,000 cal BP in synchrony with a Holocene Rapid Climate Change (RCC), a short period of climatic instability recorded in the Northern Hemisphere. This study demonstrates the interconnectedness of the first agricultural economies and the ecosystems they inhabited, and emphasizes the complex nature of human responses to environmental change during the Neolithic period in the Levant. Moreover, it provides a new environmental-cultural scenario that needs to be incorporated in the models reconstructing both the establishment of agricultural economy in southwestern Asia and the impact of environmental changes on human populations.

Simulating Patagonian Territoriality in Prehistory: Space, Frontiers and Networks Among Hunter-Gatherers

In the last 40 years, the very idea of ethnicity has evolved from a static and essentialist classification of human groups according to their immutable “nature” to a relational frame of reference used by groups of people to consider themselves “similar” or to be explicitly differentiated by others. Nevertheless, the growing importance of variability analysis of mitochondrial DNA and other biological markers in modern prehistoric studies, with their emphasis on the identification of geographic patterns in genetic and phenotypic diversity of prehistoric populations is going in the opposite direction, as if the existence of genetic variability in the past would be comparable to what is inferred about cultural variation in the present. In this paper we have built a computer simulation of economic processes causing social aggregation, territoriality and ethnogenesis among Patagonian hunter-gatherers. We argue that cultural similarity and the constriction of groups to a restricted geographical area are not necessarily ethnic markers. Our model suggests that the more inter-generational knowledge transmission among socially aggregated individuals in the past, the greater the similarity in the social activity performed by agents in the present, and the same for their territoriality and the way frontiers and social networks were negotiated. Our computer simulation intends to answer the question “Why did human groups modify their traditional residence mobility and dispersal patterns?” In ancient Patagonia, at the extreme south of South America, from 12,000 BC until nineteenth century AD, this social transformation seems to coincide with slow changes in subsistence economy and technology. However, there are historical and archaeological sources that suggest this process was related with increased social complexity: wars and conflicts between different indigenous groups would have preceded this new scenario, even before European contact.