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The Comitán Valley
A thousand years ago, the Comitán Valley, in the Mexican state
of Chiapas, was the western edge of the Maya world. Far from the
famous power centers of the Classic period, the valley has been
neglected even by specialists. Here, Caitlin C. Earley offers the
first comprehensive study of sculpture excavated from the area,
showcasing the sophistication and cultural vigor of a region that
has largely been ignored.
Supported by the rulers of the valley's cities, local artists
created inventive works that served to construct civic identities.
In their depictions of warrior kings, ballgames, rituals, and
ancestors, the artists of Comitán made choices that reflected
political and religious goals and distinguished the artistic
production of the Comitán Valley from that of other Maya locales.
After the Maya abandoned their powerful lowland centers, those in
Comitán were maintained, a distinction from which Earley draws new
insights concerning the Maya collapse. Richly illustrated with
never-before-published photographs of sculptures unearthed from key
archaeological sites, The Comitán Valley is an
illuminating work of art historical recovery and
interpretation.
eBook
An Arabidopsis Soil-Salinity—Tolerance Mutation Confers Ethylene-Mediated Enhancement of Sodium/Potassium Homeostasis
High soil Na concentrations damage plants by increasing cellular Na accumulation and K loss. Excess soil Na stimulates ethylene-induced soil-salinity tolerance, the mechanism of which we here define via characterization of an Arabidopsis thaliana mutant displaying transpiration-dependent soil-salinity tolerance. This phenotype is conferred by a loss-of-function allele of ETHYLENE OVERPRODUCER1 (ETO1; mutant alleles of which cause increased production of ethylene). We show that lack of ETO1 function confers soil-salinity tolerance through improved shoot Na/K homeostasis, effected via the ETHYLENE RESISTANT1—CONSTITUTIVE TRIPLE RESPONSE1 ethylene signaling pathway. Under transpiring conditions, lack of ETO1 function reduces root Na influx and both stelar and xylem sap Na concentrations, thereby restricting root-to-shoot delivery of Na. These effects are associated with increased accumulation of RESPIRATORY BURST OXIDASE HOMOLOG F (RBOHF)—dependent reactive oxygen species in the root stele. Additionally, lack of ETO1 function leads to significant enhancement of tissue K status by an RBOHF-independent mechanism associated with elevated HIGH-AFFINITY K + TRANSPORTER5 transcript levels. We conclude that ethylene promotes soil-salinity tolerance via improved Na/K homeostasis mediated by RBOHF-dependent regulation of Na accumulation and RBOHF-independent regulation of K accumulation.
Journal Article
Root anatomy and biomechanical properties: improving predictions through root cortical and stele properties
Purpose
Quantifying the stability of individual plants or their contribution to soil reinforcement against erosion or landslides requires an understanding of the tensile properties of their roots. This work developed a new analytical model to understand the tensile stress–strain behaviour of a single root axis, which is the first to incorporating root anatomical features, in order to reduce the existing uncertainty in predictions.
Methods
The root was modelled as a linear elastic stele connected to a surrounding linear elastic cortex by means of a linear elastic stele–cortex interface. By solving for force equilibrium, an analytical solution for the full tensile stress–strain behaviour — including any intermediate brittle failures of the stele, cortex and/or interface — was obtained. This model was compared to tensile tests and laser ablation tomography for maize roots.
Results
The new modelling approach demonstrated that the root tensile strength is fully determined by the strength of the stele alone, which was an order of magnitude larger than that of the cortex while also 3–4 times stiffer. The reduction in root stiffness beyond the yield point was linked to continuing fracturing of the cortex and debonding along the stele–cortex interface. A larger proportion of the variation in experimentally measured biomechanical characteristics could be explained compared to root diameter power-law fitting methods typically applied in the literature.
Conclusion
Stele and cortex biomechanical properties are substantially different, affecting the tensile behaviour of plant roots. Accounting for these anatomical traits increased the accuracy root biomechanical properties from tensile tests.
Journal Article
Genealogy and Status
By shedding light on a long-forgotten epigraphic genre that flourished in North China during the Mongol Empire, or Yuan Dynasty (1271-1368), Genealogy and Status explores the ways the conquered Chinese people understood and represented the alien Mongol ruling principles through their own cultural tradition. This epigraphic genre, which this book collectively calls \"genealogical steles,\" was quite unique in the history of Chinese epigraphy.Northern Chinese officials commissioned these steles exclusively to record a family's extensive genealogy, rather than the biography or achievements of an individual. Tomoyasu Iiyama shows how the rise of these steles demonstrates that Mongol rule fundamentally affected how northern Chinese families defined, organized, and commemorated their kinship. Because most of these inscriptions are in Classical Chinese, they appear to be part of Chinese tradition. In fact, they reflect a massive social change in Chinese society that occurred because of Mongol rule in China.The evolution of genealogical steles delineates how local elites, while thinking of themselves as the heirs of traditional Chinese culture, fully accommodated to Mongol imperial rule and became instead one of its cornerstones in eastern Eurasia.
eBook
A retrotransposon in an HKT1 family sodium transporter causes variation of leaf Na+ exclusion and salt tolerance in maize
Soil salinity is one of several major abiotic stresses that constrain maize productivity worldwide. An improved understanding of salt-tolerance mechanisms will thus enhance the breeding of salt-tolerant maize and boost productivity. Previous studies have indicated that the maintenance of leaf Na+ concentration is essential for maize salt tolerance, and the difference in leaf Na+ exclusion has previously been associated with variation in salt tolerance between maize varieties.
Here, we report the identification and functional characterization of a maize salt-tolerance quantitative trait locus (QTL), Zea mays Na
+
Content1 (ZmNC1), which encodes an HKT-type transporter (designated as ZmHKT1).
We show that a natural ZmHKT1 loss-of-function allele containing a retrotransposon insertion confers increased accumulation of Na+ in leaves, and salt hypersensitivity. We next show that ZmHKT1 encodes a plasma membrane-localized Na+-selective transporter, and is preferentially expressed in root stele (including the parenchyma cells surrounding the xylem vessels). We also show that loss of ZmHKT1 function increases xylem sap Na+ concentration and causes increased root-to-shoot Na+ delivery, indicating that ZmHKT1 promotes leaf Na+ exclusion and salt tolerance by withdrawing Na+ from the xylem sap.
We conclude that ZmHKT1 is a major salt-tolerance QTL and identifies an important new gene target in breeding for improved maize salt tolerance.
Journal Article