Trees use exogenous sugars for growth, but excess triggers negative feedback reducing photosynthetic carbon gain.

Plants' non structural carbohydrates (NSCs) serve as their capital for growth, reproduction, defense and survival. To increase the NSC availability of carbon-limited trees, a recent study revealed the possibility of adding exogenous soluble sugars to carbon-starved trees. This provides an opportunity to investigate carbon allocation between source and sink, as well as the growth and physiological responses to external sugars.

Decreasing Stem Growth in Common European Tree Species Despite Earlier Growth Onset.

Recent findings suggest that global warming is altering the timing of trees' phenological activities, including earlier emergence from winter dormancy. While early-season warming can boost carbon uptake, tree growth does not seem to benefit. The underlying mechanisms and the altered intra- and inter-annual growth dynamics, as well as their interaction with environmental factors, remain poorly understood.

Contrasting photosynthetic, stomatal and mesophyll mechanisms drive common reductions in leaf water-use efficiency under blue light.

Forests experience complex light environments, yet the detailed roles of photosynthetic, stomatal, mesophyll and biochemical responses to dynamic blue light remain unclear in tree species. We measured the blue-light responses of leaf gas exchange, online isotope discrimination, photorespiration and chlorophyll fluorescence in grey alder and holm oak, and investigated the underlying biochemical and physiological mechanisms. With increasing blue light, differing photosynthetic and stomatal responses consistently led to a decrease in water-use efficiency (WUE) in the two species.

Exogenous sugar addition can exacerbate root carbon limitation in trees.

In most tree species, roots serve as major carbon (C) sinks, where C is depleted first when C assimilation is limited. Recent methodological advancements in sugar infusion allow for a better understanding of physiological processes alleviating root C limitation. We conducted a glasshouse experiment with maple (Acer pseudoplatanus L.

Age-Dependent Variations in Xylem Hydraulic Efficiency and Safety of Abies fabri.

The impact of aging on the hydraulic functions of entire trees is crucial for accurately forecasting the productivity and expansion of mature forests. Nevertheless, it is not well understood whether and how the hydraulic properties of subalpine conifers evolve as they age. To investigate this, we evaluated the hydraulic and embolic properties of the roots and stems of Abies fabri at three different stand ages and assessed their safety and efficiency tradeoffs and vulnerability segmentation.

Tracing Oxygen and Hydrogen Isotope Signals From Water Sources to Tree-Ring Compounds.

Stable oxygen (δO) and hydrogen (δH) isotope compositions of tree-ring compounds preserve information about environmental waters; however, our understanding of their isotopic relationships is hampered by the lack of long-term data sets. We investigated correlations using unique 17-year (2006-2022) δO and δH time series of bi-weekly measured soil solution, modelled precipitation and xylem water, along with those of tree-ring α-cellulose and lignin methoxy groups from Norway spruce (Picea abies) across three Swiss forest sites. We show that tree-ring cellulose δO preserves water source information more effectively than δH, making it better suited for ecohydrological reconstructions.

Rainwater uptake in conifer twigs: five experiments tell a story of absorption, storage, and transport.

While evidence supports the idea that a portion of the many raindrops that fall onto a forest canopy may be directly absorbed by the twigs they land on, we do not know how much is absorbed, how it enters the twig, or what internal path it might take on its way to the xylem. Using a diverse series of five experiments encompassing isotopic labelling, fluorescent tracers, rehydration kinetics, synchrotron-based X-ray tomographic microscopy, and thermal imaging, we follow the fate of rainwater from initial contact with the twig to its distribution to adjacent tissues. We provide conclusive, multi-pronged evidence of surface water-absorption into the xylem of 1-year-old conifer twigs with incomplete bark development.

Dealing With Two Stresses: Impact of a Damaging Spring Frost Followed by a Summer Drought on Saplings of Four Temperate Tree Species.

Global warming increases the likelihood that temperate tree species will face damaging late spring frost (LSF) and severe summer drought during the same growing season. However, the interactive effects of these two stresses are barely explored. We investigated the physiological and growth responses of Acer campestre, Fagus sylvatica, Quercus robur and Quercus petraea saplings to artificially induced LSF and drought, focusing on stomatal gas exchange, carbon partitioning, nonstructural carbohydrates (NSCs), phenology and tree growth.

Global increase in the occurrence and impact of multiyear droughts.

Persistent multiyear drought (MYD) events pose a growing threat to nature and humans in a changing climate. We identified and inventoried global MYDs by detecting spatiotemporally contiguous climatic anomalies, showing that MYDs have become drier, hotter, and led to increasingly diminished vegetation greenness. The global terrestrial land affected by MYDs has increased at a rate of 49,279 ± 14,771 square kilometers per year from 1980 to 2018.

The memory of past water abundance shapes trees 7 years later.

Premise: Tree structure and function are constrained by and acclimate to climatic conditions. Drought limits plant growth and carbon acquisition and can result in "legacy" effects that last beyond the period of water stress. Leaf and twig-level legacy effects of past water abundance, such as that experienced by trees that established under wetter conditions are unknown.

Does optimality partitioning theory fail for belowground traits? Insights from geophysical imaging of a drought-release experiment in a Scots Pine forest.

We investigate the impact of a 20-yr irrigation on root water uptake (RWU) and drought stress release in a naturally dry Scots pine forest. We use a combination of electrical resistivity tomography to image RWU, drone flights to image the crown stress and sensors to monitor soil water content. Our findings suggest that increased water availability enhances root growth and resource use efficiency, potentially increasing trees' resistance to future drought conditions by enabling water uptake from deeper soil layers.

Stable Isotope Labelling Reveals Water and Carbon Fluxes in Temperate Tree Saplings Before Budbreak.

Despite considerable experimental effort, the physiological mechanisms governing temperate tree species' water and carbon dynamics before the onset of the growing period remain poorly understood. We applied H-enriched water during winter dormancy to the soil of four potted European tree species. After 8 weeks of chilling, hydrogen isotopes in stem, twig and bud water were measured six times during 2 consecutive weeks of forcing conditions (Experiment 1).

Dry inside: progressive unsaturation within leaves with increasing vapour pressure deficit affects estimation of key leaf gas exchange parameters.

Climate change not only leads to higher air temperatures but also increases the vapour pressure deficit (VPD) of the air. Understanding the direct effect of VPD on leaf gas exchange is crucial for precise modelling of stomatal functioning. We conducted combined leaf gas exchange and online isotope discrimination measurements on four common European tree species across a VPD range of 0.

Green Routes: Exploring Protein-Based Virus-like Nanoparticle Transport and Immune Activation in for Biotechnological Applications.

Viral, bacterial, fungal, and nematode infections cause significant agricultural losses, with limited treatment options, necessitating novel approaches to enhance plant defense systems and protection against pathogens. Virus-like nanoparticles (VLPs), extensively used in animal and human therapies (e.g.

Hydrogen isotope fractionation in plants with C, C, and CAM CO fixation.

Measurements of stable isotope ratios in organic compounds are widely used tools for plant ecophysiological studies. However, the complexity of the processes involved in shaping hydrogen isotope values (δH) in plant carbohydrates has limited its broader application. To investigate the underlying biochemical processes responsible for H fractionation among water, sugars, and cellulose in leaves, we studied the three main CO fixation pathways (C, C, and CAM) and their response to changes in temperature and vapor pressure deficit (VPD).

Uptake and physiological impacts of nanoplastics in trees with divergent water use strategies.

Anthropogenic contaminants can place significant stress on vegetation, especially when they are taken up into plants. Plastic pollution, including nanoplastics (NPs), could be detrimental to tree functioning, by causing, for example, oxidative stress or reducing photosynthesis. While a number of studies have explored the capacity of plants to take up NPs, few have simultaneously assessed the functional damage due to particulate matter uptake.

The marriage between stable isotope ecology and plant metabolomics - new perspectives for metabolic flux analysis and the interpretation of ecological archives.

Even though they share many thematical overlaps, plant metabolomics and stable isotope ecology have been rather separate fields mainly due to different mass spectrometry demands. New high-resolution bioanalytical mass spectrometers are now not only offering high-throughput metabolite identification but are also suitable for compound- and intramolecular position-specific isotope analysis in the natural isotope abundance range. In plant metabolomics, label-free metabolic pathway and metabolic flux analysis might become possible when applying this new technology.

Legacy effects of premature defoliation in response to an extreme drought event modulate phytochemical profiles with subtle consequences for leaf herbivory in European beech.

Extreme droughts can have long-lasting effects on forest community dynamics and species interactions. Yet, our understanding of how drought legacy modulates ecological relationships is just unfolding. We tested the hypothesis that leaf chemistry and herbivory show long-term responses to premature defoliation caused by an extreme drought event in European beech (Fagus sylvatica L.

Different responses of oxygen and hydrogen isotopes in leaf and tree-ring organic matter to lethal soil drought.

The oxygen and hydrogen isotopic composition (δ18O, δ2H) of plant tissues are key tools for the reconstruction of hydrological and plant physiological processes and may therefore be used to disentangle the reasons for tree mortality. However, how both elements respond to soil drought conditions before death has rarely been investigated. To test this, we performed a greenhouse study and determined predisposing fertilization and lethal soil drought effects on δ18O and δ2H values of organic matter in leaves and tree rings of living and dead saplings of five European tree species.

Species-specific responses of C and N allocation to N addition: evidence from dual C and N labeling in three tree species.

Soil nitrogen (N) availability affects plant carbon (C) utilization. However, it is unclear how various tree functional types respond to N addition in terms of C assimilation, allocation, and storage. Here, a microcosm experiment with dual C and N labeling was conducted to study the effects of N addition (i.