The Mineral Assemblage of Caves Within Şălitrari Mountain (Cerna Valley, SW Romania): Depositional Environment and Speleogenetic Implications

Eighteen minerals belonging to eight chemical groups were identified from three caves within Şălitrari Mountain, in the upper Cerna River basin (Romania) by means of scanning electron microscopy, electron microprobe analysis, and X-ray powder diffraction. One passage in the Great Cave from Şălitrari Mountain, the largest cave investigated, exhibits abnormal relative humidity and temperature ranges, allowing for a particular depositional environment. The cave floor is covered by alluvial sediments (ranging from cobble, sand, and clay to silt-sized material), bear bones, bat guano, and rubble. These materials reacted with percolating meteoric water and hydrogen sulfide-rich hypogene hot solutions, precipitating a variety of secondary minerals. Most of these minerals are common in caves (e.g. calcite, gypsum, brushite), however, some of them (alunite, aluminite, and darapskite) require very particular environments in order to form and persist. Cave passage morphologies suggest a complex speleogenetic history that includes changes from phreatic to vadose conditions. The latter was punctuated by a sulfuric acid dissolution/precipitation phase, partly overprinted by present-day vadose processes. The cave morphology and the secondary minerals associated with the alluvial sediments in these caves are used to unravel the region’s speleogenetic history

RESEARCH ARTICLE Body-size structure of Central Iberian mammal fauna reveals semidesertic conditions during the middle Miocene Global Cooling Event

We developed new quantitative palaeoclimatic inference models based on the body-size structure of mammal faunas from the Old World tropics and applied them to the Somosaguas fossil site (middle Miocene, central Iberian Peninsula). Twenty-six mammal species have been described at this site, including proboscideans, ungulates, carnivores, insectivores, lagomorphs and rodents. Our analyses were based on multivariate and bivariate regression models correlating climatic data and body-size structure of 63 modern mammal assemblages from Sub-Saharan Africa and the Indian subcontinent. The results showed an average temperature of the coldest month higher than 26ÊC for the Somosaguas fossil site, a mean annual thermal amplitude around 10ÊC, a drought length of 10 months, and an annual total precipitation greater than 200 mm per year, which are climate conditions typical of an ecotonal zone between the savanna and desert biomes. These results are congruent with the aridity peaks described over the middle Aragonian of Spain and particularly in the local biozone E, which includes Somosaguas. The aridity increase detected in this biozone is associated with the Middle Miocene Global Cooling Event. The environment of Somosaguas around 14 Ma was similar to the current environment in the Sahel region of North Africa, the Horn of Africa, the boundary area between the Kalahari and the Namib in Southern Africa, south-central Arabia, or eastern Pakistan and northwestern India. The distribution of modern vegetation in these regions follows a complex mosaic of plant communities, dominated by scattered xerophilous shrublands, semidesert grasslands, and vegetation linked to seasonal watercourses and ponds.Peer reviewe

Brassinosteroid Sensing and Signaling in Plants

In 1979, a growth-promoting hormone was isolated from rape pollen (Grove et al. 1979). Its crystal structure revealed a hydroxyprolinated steroid featuring a B-ring lactone with structural similarities to the insect molting hormone ecdysone (Fig. 9.1a, b). It was named brassinolide and since its discovery dozens of related brassinosteroids, which can promote cell elongation, division, and differentiation, have been reported from different plant species (Bajguz 2007). Using synthetic brassinolide, brassinosteroid-deficient and -insensitive mutants were identified in forward genetic screens in the model plant Arabidopsis. In this way, the core biosynthetic pathway for the hormone and many components of the brassinosteroid signal transduction cascade were defined. One of the first genes to be cloned was BRI1 (Clouse et al. 1996; Li and Chory 1997), a plasma-membrane-localized recep- tor kinase with an extracellular leucine-rich repeat (LRR) domain, a single membrane spanning helix and a cytoplasmic kinase domain (Li and Chory 1997) (Fig. 9.2). BRI1 is one of ~200 LRR receptor kinases found in the Arabidopsis genome (Shiu and Bleecker 2001). BRI1 acts as receptor for brassinosteroids and binds the steroid hormone using its LRR-domain (Wang et al. 2001; Kinoshita et al. 2005)