Aim At a coarse scale, the treelines of the world's mountains seem to follow a common isotherm, but the evidence for this has been indirect so far. Here we aim at underpinning this with facts. ...Location We present the results of a data-logging campaign at 46 treeline sites between 68° N and 42° S. Methods We measured root-zone temperatures with an hourly resolution over 1-3 years per site between 1996 and 2003. Results Disregarding taxon-, landuse- or fire-driven tree limits, high altitude climatic treelines are associated with a seasonal mean ground temperature of 6.7 °C (±0.8 SD; 2.2 K amplitude of means for different climatic zones), a surprisingly narrow range. Temperatures are higher (7-8 °C) in the temperate and Mediterranean zone treelines, and are lower in equatorial treelines (5-6 °C) and in the subarctic and boreal zone (6-7 °C). While air temperatures are higher than soil temperatures in warm periods, and are lower than soil temperatures in cold periods, daily means of air and soil temperature are almost the same at 6-7 °C, a physics driven coincidence with the global mean temperature at treeline. The length of the growing season, thermal extremes or thermal sums have no predictive value for treeline altitude on a global scale. Some Mediterranean (Fagus spp.) and temperate South Hemisphere treelines (Nothofagus spp.) and the native treeline in Hawaii (Metrosideros) are located at substantially higher isotherms and represent genus-specific boundaries rather than boundaries of the life-form tree. In seasonal climates, ground temperatures in winter (absolute minima) reflect local snow pack and seem uncritical. Main conclusions The data support the hypothesis of a common thermal threshold for forest growth at high elevation, but also reflect a moderate region and substantial taxonomic influence.
Paradigm shift in plant growth control Körner, Christian
Current opinion in plant biology,
June 2015, 2015-Jun, 2015-06-00, 20150601, Letnik:
25
Journal Article
Recenzirano
•Source activity (photosynthesis) depends on sink activity (tissue growth).•Environmental stress constrains sink activity before it affects source activity.•Under drought, low temperature or nutrient ...limitation, growth controls photosynthesis.•Priority in models needs to shift from source activity to sink activity.
For plants to grow they need resources and appropriate conditions that these resources are converted into biomass. While acknowledging the importance of co-drivers, the classical view is still that carbon, that is, photosynthetic CO2 uptake, ranks above any other drivers of plant growth. Hence, theory and modelling of growth traditionally is carbon centric. Here, I suggest that this view is not reflecting reality, but emerged from the availability of methods and process understanding at leaf level. In most cases, poorly understood processes of tissue formation and cell growth are governing carbon demand, and thus, CO2 uptake. Carbon can only be converted into biomass to the extent chemical elements other than carbon, temperature or cell turgor permit.
Forest canopies play a major role in biosphere—atmosphere interaction. Their actual temperature may deviate substantially from ambient atmospheric conditions as reported by weather stations. While ...there is a long tradition of false-colour imagery, new digital technologies in combination with IR transmission lenses and autocalibration routines permit unprecedented insight into the actual temperature regimes in canopies. We report canopy leaf temperature distribution over space and time assessed over a 35
m tall mixed deciduous forest in NW Switzerland by means of a construction crane and a high resolution thermal camera. At an air temperature of 25
°
C, conifers (
Picea abies, Pinus sylverstris and
Larix decidua) and deciduous broad-leaved trees with exceptionally high transpiration (
Quercus petraea) or very open, low density canopies (
Prunus avium) exhibited mean canopy leaf temperatures close to air temperature (0.3–2.7
K above ambient) and the maximum amplitude within a given crown reached 6–9
K. In contrast, broad-leaved deciduous species with dense canopies (
Fagus sylvatica,
Carpinus betulus and
Tilia platyphyllos) were 4.5–5
K warmer than air temperature and showed within canopy temperature amplitudes of 10–12
K. Calculated leaf boundary resistance was clearly lower for conifers (3–24
m
s
−1) than for broad-leaved trees (33–64
m
s
−1). The study illustrates that mean leaf temperatures in forest trees are not adequately explained by either stomatal conductance or leaf dimensions, but strongly depend on canopy architecture (leaf area density, branching habits) in combination with leaf traits. Aerodynamic leaf and canopy characteristics lead to strongly enhanced vapour pressure gradients (evaporative forcing) and leaf temperatures vary enormously over short distances, calling for statistical temperature models (frequency distribution) rather than the use of means in any flux calculations. The presence/absence of certain tree taxa plays a key role in forest surface temperature.
Mitochondria are organelles with a complex architecture. They are bounded by an envelope consisting of the outer membrane and the inner boundary membrane (IBM). Narrow crista junctions (CJs) link the ...IBM to the cristae. OMs and IBMs are firmly connected by contact sites (CS). The molecular nature of the CS remained unknown. Using quantitative high‐resolution mass spectrometry we identified a novel complex, the mitochondrial contact site (MICOS) complex, formed by a set of mitochondrial membrane proteins that is essential for the formation of CS. MICOS is preferentially located at the CJs. Upon loss of one of the MICOS subunits, CJs disappear completely or are impaired, showing that CJs require the presence of CS to form a superstructure that links the IBM to the cristae. Loss of MICOS subunits results in loss of respiratory competence and altered inheritance of mitochondrial DNA.
The outer and inner mitochondrial membranes are physically linked. Quantitative high resolution mass spectrometry now identifies the molecular nature of the Mitochondrial Contact Site complex (MICOS). MICOS is required for crista junctions formation, respiration and mitochondrial DNA inheritance.
The global treeline phenomenon follows a common seasonal mean temperature (isotherm) of about 6°C. When the isotherm moves upslope because of rapid climatic warming, trees are left behind and are ...absent from the climatic tree limit. This commentary recalls the discrepancy between the actual uppermost position of trees and the potential (climatic) treeline. Temperature‐based models can predict the potential treeline only (comment to Camarero et al., Global Change Biology, 27, 1879–1889, 2021). The photograph shows a treeline situation in SW New Zealand.
X‐ray investigations on single crystals of a series of terminally dicyanovinyl‐substituted quaterthiophenes and co‐evaporated blend layers with C60 give insight into molecular packing behavior and ...morphology, which are crucial parameters in the field of organic electronics. Structural characteristics on various levels and length scales are correlated with the photovoltaic performance of bulk heterojunction small‐molecule organic solar cells.
Congenital disorders of glycosylation type I (CDG-I) form a growing group of recessive neurometabolic diseases. Identification of disease genes is compromised by the enormous heterogeneity in ...clinical symptoms and the large number of potential genes involved. Until now, gene identification included the sequential application of biochemical methods in blood samples and fibroblasts. In genetically unsolved cases, homozygosity mapping has been applied in consanguineous families. Altogether, this time-consuming diagnostic strategy led to the identification of defects in 17 different CDG-I genes. Here, we applied whole-exome sequencing (WES) in combination with the knowledge of the protein N-glycosylation pathway for gene identification in our remaining group of six unsolved CDG-I patients from unrelated non-consanguineous families. Exome variants were prioritized based on a list of 76 potential CDG-I candidate genes, leading to the rapid identification of one known and two novel CDG-I gene defects. These included the first X-linked CDG-I due to a de novo mutation in ALG13, and compound heterozygous mutations in DPAGT1, together the first two steps in dolichol-PP-glycan assembly, and mutations in PGM1 in two cases, involved in nucleotide sugar biosynthesis. The pathogenicity of the mutations was confirmed by showing the deficient activity of the corresponding enzymes in patient fibroblasts. Combined with these results, the gene defect has been identified in 98% of our CDG-I patients. Our results implicate the potential of WES to unravel disease genes in the CDG-I in newly diagnosed singleton families.
1. Rapidly increasing atmospheric CO₂ is not only changing the climate system but may also affect the biosphere directly through stimulation of plant growth and ecosystem carbon and nutrient cycling. ...Although forest ecosystems play a critical role in the global carbon cycle, experimental information on forest responses to rising CO₂ is scarce, due to the sheer size of trees. 2. Here, we present a synthesis of the only study world-wide where a diverse set of mature broadleaved trees growing in a natural forest has been exposed to future atmospheric CO₂ levels (c. 550 ppm) by free-air CO₂ enrichment (FACE). We show that litter production, leaf traits and radial growth across the studied hardwood species remained unaffected by elevated CO₂ over 8 years. 3. CO₂ enrichment reduced tree water consumption resulting in detectable soil moisture savings. Soil air CO₂ and dissolved inorganic carbon both increased suggesting enhanced below-ground activity. Carbon release to the rhizosphere and/or higher soil moisture primed nitrification and nitrate leaching under elevated CO₂; however, the export of dissolved organic carbon remained unaltered. 4. Synthesis. Our findings provide no evidence for carbon-limitation in five central European hardwood trees at current ambient CO₂ concentrations. The results of this long-term study challenge the idea of a universal CO₂ fertilization effect on forests, as commonly assumed in climate-carbon cycle models.
Efficient synthesis of a series of terminally dicyanovinyl (DCV)‐substituted oligothiophenes, DCVnT 1–6, without solubilizing side chains synthesized via a novel convergent approach and their ...application as electron donors in vacuum‐processed m‐i‐p‐type planar and p‐i‐n‐type bulk heterojunction organic solar cells is described. Purification of the products via gradient sublimation yields thermally highly stable organic semiconducting materials in single crystalline quality which allows for X‐ray structure analysis. Important insights into the packing features and intermolecular interactions of these promising solar cell materials are provided. Optical absorption spectra and electrochemical properties of the oligomers are investigated and valuable structure–property relationships deduced. Photovoltaic devices incorporating DCVnTs 4–6 showed power conversion efficiencies up to 2.8% for planar and 5.2% for bulk heterojunction organic solar cells under full sun illumination (mismatch corrected simulated AM 1.5G sunlight). The 5.2% efficiency shown here represents one of the highest values ever reported for organic vacuum‐deposited single heterojunction solar cells.
A series of A‐D‐A‐type oligothiophenes have been developed as efficient donor materials for application in vacuum‐processed organic solar cells. Due to their promising optoelectronic properties and molecular packing in the bulk, these oligomers show high power conversion efficiencies up to 2.8% in planar heterojunction and record efficiencies of 5.2% in bulk heterojunction solar cells prepared by vacuum deposition.
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