Fibers beyond structure: do they contribute to embolism reversal after drought relief in poplar?

Short-term recovery from drought-induced vessel embolism is an energy-dependent biological process that requires a water source and solutes, both likely supplied by parenchyma cells. Despite fibers primarily providing structural support, their functional role as a reservoir of unbound water during and after stress remains unclear. In this study, Populus nigra plants were exposed to two drying regimes (slow and fast developing stress).

Prescribed burning has negligible effects on the plant-soil system in Pinus sylvestris L. forests of the European Alps.

The current increase in large wildfires is a socio-economic and ecological threat, particularly in populated mountain regions. Prescribed burning is a fuel management technique based on the planned application of fire to achieve land management goals; still, little is known about its potential impacts on tree physiology and soil properties in the European Alps, where it has never been applied. In spring 2022, we tested the effects of prescribed burning for fire hazard reduction in a dry conifer forest dominated by Scots pine (Pinus sylvestris L.

Response of native (Quercus robur L.) and alien (Quercus rubra L.) species to water stress and nutrient input in European temperate ecosystems.

Drought and nutrient-poor soils can increase the invasive potential of non-native species, further changing the ecosystems they invade. The high adaptability of these alien species, especially in their efficient use of resources, improves their resilience against abiotic stress. Here, we evaluated the response of the North American Quercus rubra L.

Grafting with non-suckering rootstock increases drought tolerance in Corylus avellana L. through physiological and biochemical adjustments.

Physiological and molecular mechanisms underpinning plant water stress responses still need deeper investigation. Particularly, the analysis of rootstock-mediated signals represents a complex research field, offering potential applicative perspectives for improving the adaptation of fruit crops to environmental stresses. Nonetheless, fundamental knowledge on this subject needs to be widened, especially in some woody species, including European hazelnut (Corylus avellana L).

Contrasting Responses of Two Grapevine Cultivars to Drought: The Role of Non-structural Carbohydrates in Xylem Hydraulic Recovery.

Xylem embolism is one of the possible outcomes of decreasing xylem pressure when plants face drought. Recent studies have proposed a role for non-structural carbohydrates (NSCs) in osmotic pressure generation, required for refilling embolized conduits. Potted cuttings of grapevine Grenache and Barbera, selected for their adaptation to different climatic conditions, were subjected to a drought stress followed by re-irrigation.

Alkaline soil primes the recovery from drought in Populus nigra plants through physiological and chemical adjustments.

Perennial plants are frequently exposed to severe and prolonged drought, and when the balance between water transport and transpirational demand is compromised trees are in danger of embolism formation. To maintain the physiological balance, plants can rely on mechanisms to quickly recover the lost xylem hydraulic capacity and reduce the prolonged impact on photosynthetic activity upon rehydration. Among factors helpful for plants to sustain acclimation and adaptation responses to drought and promote recovery, maintaining an optimal nutritional status is crucial for plant survival.

Responses to Drought Stress in Poplar: What Do We Know and What Can We Learn?

Poplar ( spp.) is a high-value crop for wood and biomass production and a model organism for tree physiology and genomics. The early release, in 2006, of the complete genome sequence of was followed by a wealth of studies that significantly enriched our knowledge of complex pathways inherent to woody plants, such as lignin biosynthesis and secondary cell wall deposition.

The C4 protein of tomato yellow leaf curl Sardinia virus primes drought tolerance in tomato through morphological adjustments.

Viruses can interfere with the ability of plants to overcome abiotic stresses, indicating the existence of common molecular networks that regulate stress responses. A begomovirus causing the tomato yellow leaf curl disease was recently shown to enhance heat tolerance in tomato and drought tolerance in tomato and and experimental evidence suggested that the virus-encoded protein C4 is the main trigger of drought responses. However, the physiological and molecular events underlying C4-induced drought tolerance need further elucidation.

Do the ends justify the means? Impact of drought progression rate on stress response and recovery in Vitis vinifera.

Plants are frequently exposed to prolonged and intense drought events. To survive, species must implement strategies to overcome progressive drought while maintaining sufficient resources to sustain the recovery of functions. Our objective was to understand how stress rate development modulates energy reserves and affects the recovery process.

A new protein hydrolysate-based biostimulant applied by fertigation promotes relief from drought stress in Capsicum annuum L.

Recently, biostimulants have been used in sustainable agriculture as priming agents able to increase crop tolerance to abiotic stressors. Here, a soil application of GHI_16_VHL, a plant protein hydrolysate-based biostimulant, was tested for its capability to mitigate severe water stress effects on Capsicum annuum at flowering time. The biostimulant influence on plant physiological status was monitored upon stress and its relief, by measuring chlorophyll levels, stomatal density, stem water potential, leaf gas exchanges and plant growth.

Grapevine TPS (trehalose-6-phosphate synthase) family genes are differentially regulated during development, upon sugar treatment and drought stress.

Trehalose-6-phosphate synthase (TPS) performs the first step in the biosynthetic pathway of trehalose-6-phosphate and trehalose. These two molecules play key roles in the control of carbon allocation and of stress responses in plants. We investigated the organization of the TPS gene family and its developmental and environmental expression regulation in grapevine, a major horticultural crop.

Chemical inhibition of xylem cellular activity impedes the removal of drought-induced embolisms in poplar stems - new insights from micro-CT analysis.

In drought-stressed plants a coordinated cascade of chemical and transcriptional adjustments occurs at the same time as embolism formation. While these processes do not affect embolism formation during stress, they may prime stems for recovery during rehydration by modifying apoplast pH and increasing sugar concentration in the xylem sap. Here we show that in vivo treatments modifying apoplastic pH (stem infiltration with a pH buffer) or reducing stem metabolic activity (infiltration with sodium vanadate and sodium cyanide; plant exposure to carbon monoxide) can reduce sugar accumulation, thus disrupting or delaying the recovery process.

Priming xylem for stress recovery depends on coordinated activity of sugar metabolic pathways and changes in xylem sap pH.

Some plant species are capable of significant reduction of xylem embolism during recovery from drought despite stem water potential remains negative. However, the functional biology underlying this process is elusive. We subjected poplar trees to drought stress followed by a period of recovery.

Dissecting interplays between Vitis vinifera L. and grapevine virus B (GVB) under field conditions.

Plant virus infections are often difficult to characterize as they result from a complex molecular and physiological interplay between a pathogen and its host. In this study, the impact of the phloem-limited grapevine virus B (GVB) on the Vitis vinifera L. wine-red cultivar Albarossa was analysed under field conditions.

The pitfalls of in vivo imaging techniques: evidence for cellular damage caused by synchrotron X-ray computed micro-tomography.

Synchrotron X-ray computed micro-tomography (microCT) has emerged as a promising noninvasive technique for in vivo monitoring of xylem function, including embolism build-up under drought and hydraulic recovery following re-irrigation. Yet, the possible harmful effects of ionizing radiation on plant tissues have never been quantified. We specifically investigated the eventual damage suffered by stem living cells of three different species exposed to repeated microCT scans.

Acclimation of Pistacia integerrima trees to frost in semi-arid environments depends on autumn's drought.

Main conclusion Cold acclimation is revealed through induced stem respiration during pre-winter frost of native Pistacia integerrima trees in continental semi-arid environments. Semi-arid environments challenge vegetation by simultaneous abiotic stresses. In this study, we examine the combined effects of water stress and frost on the physiology of Pistacia integerrima stems.

The functional role of xylem parenchyma cells and aquaporins during recovery from severe water stress.

Xylem parenchyma cells [vessel associated cells (VACs)] constitute a significant fraction of the xylem in woody plants. These cells are often closely connected with xylem vessels or tracheids via simple pores (remnants of plasmodesmata fields). The close contact and biological activity of VACs during times of severe water stress and recovery from stress suggest that they are involved in the maintenance of xylem transport capacity and responsible for the restoration of vessel/tracheid functionality following embolism events.

Accumulation of sugars in the xylem apoplast observed under water stress conditions is controlled by xylem pH.

Severe water stress constrains, or even stops, water transport in the xylem due to embolism formation. Previously, the xylem of poplar trees was shown to respond to embolism formation by accumulating carbohydrates in the xylem apoplast and dropping xylem sap pH. We hypothesize that these two processes may be functionally linked as lower pH activates acidic invertases degrading sucrose and inducing accumulation of monosaccharides in xylem apoplast.

Changes in Air CO₂ Concentration Differentially Alter Transcript Levels of NtAQP1 and NtPIP2;1 Aquaporin Genes in Tobacco Leaves.

The aquaporin specific control on water versus carbon pathways in leaves is pivotal in controlling gas exchange and leaf hydraulics. We investigated whether Nicotiana tabacum aquaporin 1 (NtAQP1) and Nicotiana tabacum plasma membrane intrinsic protein 2;1 (NtPIP2;1) gene expression varies in tobacco leaves subjected to treatments with different CO₂ concentrations (ranging from 0 to 800 ppm), inducing changes in photosynthesis, stomatal regulation and water evaporation from the leaf. Changes in air CO₂ concentration ([CO₂]) affected net photosynthesis (Pn) and leaf substomatal [CO₂] (Ci).

Frost Induces Respiration and Accelerates Carbon Depletion in Trees.

Cellular respiration depletes stored carbohydrates during extended periods of limited photosynthesis, e.g. winter dormancy or drought.

The tomato plastidic fructokinase SlFRK3 plays a role in xylem development.

Plants have two kinds of fructokinases (FRKs) that catalyze the key step of fructose phosphorylation, cytosolic and plastidic. The major cytosolic tomato FRK, SlFRK2, is essential for the development of xylem vessels. In order to study the role of SlFRK3, which encodes the only plastidic FRK, we generated transgenic tomato (Solanum lycopersicon) plants with RNAi suppression of SlFRK3 as well as plants expressing beta-glucoronidase (GUS) under the SlFRK3 promoter.

Threats to xylem hydraulic function of trees under 'new climate normal' conditions.

Climate models predict increases in frequency and intensity of extreme environmental conditions, such as changes to minimum and maximum temperatures, duration of drought periods, intensity of rainfall/snowfall events and wind strength. These local extremes, rather than average climatic conditions, are closely linked to woody plant survival, as trees cope with such events over long lifespans. While the xylem provides trees with structural strength and is considered the most robust part of a tree's structure, it is also the most physiologically vulnerable as tree survival depends on its ability to sustain water supply to the tree crown under variable environmental conditions.

Down-regulation of plasma intrinsic protein1 aquaporin in poplar trees is detrimental to recovery from embolism.

During their lifecycles, trees encounter multiple events of water stress that often result in embolism formation and temporal decreases in xylem transport capacity. The restoration of xylem transport capacity requires changes in cell metabolic activity and gene expression. Specifically, in poplar (Populus spp.

Relationship between hexokinase and the aquaporin PIP1 in the regulation of photosynthesis and plant growth.

Increased expression of the aquaporin NtAQP1, which is known to function as a plasmalemma channel for CO₂ and water, increases the rate of both photosynthesis and transpiration. In contrast, increased expression of Arabidopsis hexokinase1 (AtHXK1), a dual-function enzyme that mediates sugar sensing, decreases the expression of photosynthetic genes and the rate of transpiration and inhibits growth. Here, we show that AtHXK1 also decreases root and stem hydraulic conductivity and leaf mesophyll CO₂ conductance (g(m)).

The physiological response of Populus tremula x alba leaves to the down-regulation of PIP1 aquaporin gene expression under no water stress.

In order to study the role of PIP1 aquaporins in leaf water and CO2 transport, several lines of PIP1-deficient transgenic Populus tremula x alba were generated using a reverse genetic approach. These transgenic lines displayed no visible developmental or morphological phenotypes when grown under conditions of no water stress. Major photosynthetic parameters were also not affected by PIP1 down regulation.