scholarly journals Metabolism is the major driver of hydrogen isotope fractionation recorded in tree-ring glucose of Pinus nigra

2021 ◽  
Author(s):  
Thomas Wieloch ◽  
Michael Grabner ◽  
Angela Augusti ◽  
Henrik Serk ◽  
Ina Ehlers ◽  
...  
Keyword(s):  
Tree Ring ◽  
Hydrogen Isotope ◽  
Pinus Nigra ◽  
Widespread Application ◽  
Physiological Processes ◽  
Environmental Controls ◽  
Main Driver ◽  
Leaf Level ◽  
Response Change ◽  
Isotope Variation

- Stable isotope abundances convey valuable information about plant physiological processes and underlying environmental controls. Central gaps in our mechanistic understanding of hydrogen isotope abundances impede their widespread application within the plant and Earth sciences. - To close these gaps, we analysed intramolecular deuterium abundances in glucose of Pinus nigra extracted from an annually resolved tree-ring series (1961 to 1995). - We found fractionation signals at glucose H1 and H2 introduced by closely related metabolic processes. These signals (and thus metabolism) respond to drought and atmospheric CO2 concentration beyond a response change point. They explain ≈60% of the whole-molecule deuterium variability. Altered metabolism is associated with below-average yet not exceptionally low growth. - We propose the signals are introduced at the leaf-level by changes in sucrose-to-starch carbon partitioning and anaplerotic carbon flux into the Calvin-Benson cycle. In conclusion, metabolism can be the main driver of hydrogen isotope variation in plant glucose.

scholarly journals The Link between VAPB Loss of Function and Amyotrophic Lateral Sclerosis

Cells ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1865
Author(s):  
Nica Borgese ◽  
Nicola Iacomino ◽  
Sara Francesca Colombo ◽  
Francesca Navone
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Motor Neurons ◽  
Adaptor Proteins ◽  
Loss Of Function ◽  
Membrane Contact Sites ◽  
Physiological Processes ◽  
Main Driver ◽  
Single Allele ◽  
Induced Pluripotent ◽  
Lateral Sclerosis

The VAP proteins are integral adaptor proteins of the endoplasmic reticulum (ER) membrane that recruit a myriad of interacting partners to the ER surface. Through these interactions, the VAPs mediate a large number of processes, notably the generation of membrane contact sites between the ER and essentially all other cellular membranes. In 2004, it was discovered that a mutation (p.P56S) in the VAPB paralogue causes a rare form of dominantly inherited familial amyotrophic lateral sclerosis (ALS8). The mutant protein is aggregation-prone, non-functional and unstable, and its expression from a single allele appears to be insufficient to support toxic gain-of-function effects within motor neurons. Instead, loss-of-function of the single wild-type allele is required for pathological effects, and VAPB haploinsufficiency may be the main driver of the disease. In this article, we review the studies on the effects of VAPB deficit in cellular and animal models. Several basic cell physiological processes are affected by downregulation or complete depletion of VAPB, impinging on phosphoinositide homeostasis, Ca2+ signalling, ion transport, neurite extension, and ER stress. In the future, the distinction between the roles of the two VAP paralogues (A and B), as well as studies on motor neurons generated from induced pluripotent stem cells (iPSC) of ALS8 patients will further elucidate the pathogenic basis of p.P56S familial ALS, as well as of other more common forms of the disease.

scholarly journals Tree Vitality and Forest Health: Can Tree-Ring Stable Isotopes Be Used as Indicators?

2021 ◽  
Author(s):  
Paolo Cherubini ◽  
Giovanna Battipaglia ◽  
John L. Innes
Keyword(s):  
Air Pollution ◽  
Stable Isotopes ◽  
Tree Ring ◽  
Forest Decline ◽  
Forest Health ◽  
Stress Factors ◽  
Tree Vitality ◽  
The Past ◽  
Physiological Processes

Abstract Purpose of Review Society is concerned about the long-term condition of the forests. Although a clear definition of forest health is still missing, to evaluate forest health, monitoring efforts in the past 40 years have concentrated on the assessment of tree vitality, trying to estimate tree photosynthesis rates and productivity. Used in monitoring forest decline in Central Europe since the 1980s, crown foliage transparency has been commonly believed to be the best indicator of tree condition in relation to air pollution, although annual variations appear more closely related to water stress. Although crown transparency is not a good indicator of tree photosynthesis rates, defoliation is still one of the most used indicators of tree vitality. Tree rings have been often used as indicators of past productivity. However, long-term tree growth trends are difficult to interpret because of sampling bias, and ring width patterns do not provide any information about tree physiological processes. Recent Findings In the past two decades, tree-ring stable isotopes have been used not only to reconstruct the impact of past climatic events, such as drought, but also in the study of forest decline induced by air pollution episodes, and other natural disturbances and environmental stress, such as pest outbreaks and wildfires. They have proven to be useful tools for understanding physiological processes and tree response to such stress factors. Summary Tree-ring stable isotopes integrate crown transpiration rates and photosynthesis rates and may enhance our understanding of tree vitality. They are promising indicators of tree vitality. We call for the use of tree-ring stable isotopes in future monitoring programmes.

scholarly journals Different climate sensitivity for radial growth, but uniform for tree-ring stable isotopes along an aridity gradient in Polylepis tarapacana, the world’s highest elevation tree-species

2021 ◽  
Author(s):  
Milagros Rodriguez-Caton ◽  
Laia Andreu-Hayles ◽  
Mariano S Morales ◽  
Valérie Daux ◽  
Duncan A Christie ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Carbon Source ◽  
Tree Ring ◽  
Tree Growth ◽  
Carbon Sink ◽  
Growing Season ◽  
Wood Formation ◽  
Aridity Gradient ◽  
Leaf Level ◽  
Δ13c And Δ18o

Abstract Tree growth is generally considered to be temperature-limited at upper elevation treelines. Yet, climate factors controlling tree growth at semiarid treelines are poorly understood. We explored the influence of climate on stem growth and stable isotopes for Polyepis tarapacana, the world’s highest elevation tree-species found only in the South American Altiplano. We developed tree-ring width index (RWI), oxygen (δ18O) and carbon (δ13C) chronologies for the last 60 years at four P. tarapacana stands located above 4,400 meters in elevation, along a 500-km latitude-aridity gradient. Total annual precipitation decreased from 300 to 200 mm from the northern to the southern sites. We used RWI as a proxy of wood formation (carbon sink) and isotopic tree-ring signatures as proxies of leaf-level gas exchange processes (carbon source). We found distinct climatic conditions regulating carbon-sink processes along the gradient. Current-growing season temperature regulated RWI at wetter-northern sites, while prior-growing season precipitation determined RWI at arid-southern sites. This suggests that the relative importance of temperature to precipitation in regulating tree growth is driven by site-water availability. In contrast, warm and dry growing-seasons resulted in enriched tree-ring δ13C and δ18O at all study sites, suggesting that similar climate conditions control carbon-source processes. Site-level δ13C and δ18O chronologies were significantly and positively related at all sites, with the strongest relationships among the southern-drier stands. This indicates an overall regulation of intercellular carbon dioxide via stomatal conductance for the entire P. tarapacana network, with greater stomatal control when aridity increases. The manuscript also highlights a coupling and decoupling of physiological processes at leaf level versus wood formation depending on their respectively uniform and distinct sensitivity to climate. This study contributes to better understand and predict the response of high-elevation Polylepis woodlands to rapid climate changes and projected drying in the Altiplano.

scholarly journals Contrasting Signals of the Westerly Index and North Atlantic Oscillation over the Drought Sensitivity of Tree-Ring Chronologies from the Mediterranean Basin

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 644 ◽  
Author(s):  
Pablo Casas-Gómez ◽  
Raúl Sánchez-Salguero ◽  
Pedro Ribera ◽  
Juan C. Linares
Keyword(s):  
North Atlantic Oscillation ◽  
Tree Ring ◽  
North Atlantic ◽  
Tree Species ◽  
Ring Width ◽  
Pinus Nigra ◽  
Western Mediterranean ◽  
Drought Severity ◽  
Drought Sensitivity ◽  
Westerly Index

Extreme drought events are becoming increasingly frequent and extended, particularly in Mediterranean drought-prone regions. In this sense, atmospheric oscillations patterns, such as those represented by the North Atlantic Oscillation (NAO) index and the Westerly Index (WI) have been widely proven as reliable proxies of drought trends. Here, we used the Standardized Precipitation–Evapotranspiration Index (SPEI), as a reliable indicator of drought, to investigate the drought sensitivity of tree-ring width data (TRW) from several long-lived tree species (Abies borisii-regis, Abies cilicica, Abies pinsapo, Cedrus atlantica, Cedrus libanii, Pinus nigra, Pinus heldreichii). NAO and WI relations with TRW were also investigated in order to identify potential non-stationary responses among those drought proxies. Our temporal and spatial analyses support contrasting Mediterranean dipole patterns regarding the drought sensitivity of tree growth for each tree species. The spatial assessment of NAO and WI relationships regarding SPEI and TRW showed on average stronger correlations westward with non-stationary correlations between annual WI index and TRW in all species. The results indicate that the drought variability and the inferred drought-sensitive trees species (e.g., C. atlantica) are related to the NAO and the WI, showing that TRW is a feasible proxy to long-term reconstructions of Westerly Index (WI) variability in the Western Mediterranean region. Spatial variability of drought severity suggests a complex association between NAO and WI, likely modulated by an east–west Mediterranean climate dipole.

Tree vitality and forest health: any better indicators?

2021 ◽  
Author(s):  
Paolo Cherubini ◽  
Giovanna Battipaglia ◽  
John L. Innes
Keyword(s):  
Stable Isotopes ◽  
Tree Ring ◽  
Forest Health ◽  
Ring Width ◽  
Sampling Bias ◽  
Stress Factors ◽  
Tree Vitality ◽  
The Past ◽  
Physiological Processes ◽  
The Impact

<p>Forest health, although not yet unanimously defined, has been monitored in the past forty years assessing tree vitality, trying to estimate tree photosynthesis rates and productivity. Used in monitoring forest decline in Central Europe since the 1980s, crown foliage transparency has been commonly believed to be the best indicator of tree condition in relation to air pollution, although annual variations appear more closely related to water stress. Although crown transparency is not a good indicator of tree photosynthesis rates, defoliation is still one of the most used indicators of tree vitality. Tree rings have been often used as indicators of past productivity. However, long-term tree-growth trends are difficult to interpret because of sampling bias, and ring-width patterns do not provide any information about tree physiological processes. In the past two decades, tree-ring carbon and oxygen stable isotopes have been used  to reconstruct the impact of past climatic events, such as drought. They have proven to be useful tools for retrospectively understanding physiological processes and tree response to  stress factors. Tree-ring stable isotopes integrate crown transpiration rates and photosynthesis rates and may enhance our understanding of tree vitality. They are promising indicators of tree vitality. We call for the use of tree-ring stable isotopes in future monitoring programmes.</p>

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