Salinity responses of Populus alba L. clone 'Marte' were evaluated using a split-root system to simulate the heterogeneous soil conditions in the field and to assess the salinity tolerance of clone 'Marte'. During the 26 days of experiment, we measured morpho-physiological parameters as well as the mineral content in substrate and plant organs in split-root plants watered with no salt on both sides of the system (0/0 mM - S1), salt on one side (0/100 mM - S2) and salt on both sides (100/100 mM - S3). Shoot elongation, stem diameter increase, and number of new leaves were not significantly different among and within each salt treatment. Leaf relative chlorophyll content and chlorophyll a fluorescence did not show any difference, while there was a decrease of 85% in terms of net photosynthesis (Pn) and 88% in stomatal conductance (g(s)) in S3 plants compared to S1. Na, absorbed by one side of the 0/100 mM plants, was equally distributed in all aerial organs and reached a concentration in-between the other two groups, as a confirmation of the physiological results obtained. An increase in Mn concentrations in woody cutting, stems and leaves of S2 and S3 system compared to S1 group was observed. Moreover, S3 plants showed an increase of K concentration in leaves. In 'Marte' poplar, Na increment was only translated in a reduction of photosyntetic performances, and the increase of some key mineral elements at leaf level such as K and Mn suggested an attempt to overcome the stress.

Several biotic and abiotic interactions will contribute to riparian ecosystem changes. The impact of Eurasian beaver (Castor fiber) on woody vegetation is still unknown for theMediterranean biogeographical area. Through a replicable approach applied on a cluster of three rivers, we studied how the tree layer of Mediterranean riparian sites is impacted by the beaver's recent come -back. For each site, we collected data (e.g., stem diameter, species, distance from riverbank) for all standing trees and additio- nal information only for gnawed trees at plot level. Data elaboration allowed to characterise impacts on riparian vegetation. Salix spp. and Populus spp. are the main gnawed species, but sporadically other species can be selected based on their size and spatial distribution (e.g., Alnus glutinosa). Diameter means of gnawed trees are significantly lower than the not gnawed ones. Most of the selected trees have low diameter classes (< 12 cm), even if diameter preferences may vary on the basis of overall stand tree size range and distribution. Over 90% of the gnawed trees are entirely harvested, with stumps as the remaining standing element. Main changes on the overall forest stand occurred in the first ten metres from the riverbank, as beaver gnawing acti- vity is significantly influenced by the interaction among tree distance from the river and diameter size. Our approach can be used as a model system to be implemented in other Mediterranean sites where beaver is expanding, with the aim of predicting mid-term riparian forests vegetation changes.

Water scarcity in agriculture can limit crop production and trigger the need for more effective water resource management. As a result, it is critical to identify new crop genotypes that are more drought tolerant and perform better under low irrigation or even rain-fed conditions. The olive tree is a high-value crop that is well adapted to dry Mediterranean conditions. However, different genotypes may have developed different mechanisms of tolerance to water stress. To investigate such mechanisms, we examined three Italian olive cultivars ('Giarraffa', 'Leccino', and 'Maurino') grown in a greenhouse under drought stress. We found that single genotypes responded differently to the drought, though not all parameters revealed significant differences. The first major difference among the cultivars was in transpiration: the lower stomatal density and stomatal conductance of 'Giarraffa' allow this cultivar to use water more conservatively. In parallel with the reduction in stomatal and mesophyll conductance, the drought-stressed group of 'Giarraffa' maintained the electron transport rate and effective efficiency levels of photosystem II similar to those of the control until the fourth week of stress. The fluorescence parameters revealed the earlier closure of reaction photosynthetic centres in 'Leccino'. Finally, the higher rate of electrolyte leakage in 'Maurino' indicated a significant ions loss in this cultivar when it was subjected to the drought. Both water management under stress conditions and the effect of drought on photosynthesis make 'Giarraffa' interesting to researchers studying its use in breeding or water-saving programmes.

Despite growing interest in predicting plant phenological shifts, advanced spring phenology by global climate change remains debated. Evidence documenting either small or large advancement of spring phenology to rising temperature over the spatio-temporal scales implies a potential existence of a thermal threshold in the responses of forests to global warming. We collected a unique data set of xylem cell-wall-thickening onset dates in 20 coniferous species covering a broad mean annual temperature (MAT) gradient (-3.05 to 22.9°C) across the Northern Hemisphere (latitudes 23°-66° N). Along the MAT gradient, we identified a threshold temperature (using segmented regression) of 4.9 ± 1.1°C, above which the response of xylem phenology to rising temperatures significantly decline. This threshold separates the Northern Hemisphere conifers into cold and warm thermal niches, with MAT and spring forcing being the primary drivers for the onset dates (estimated by linear and Bayesian mixed-effect models), respectively. The identified thermal threshold should be integrated into the Earth-System-Models for a better understanding of spring phenology in response to global warming and an improved prediction of global climate-carbon feedbacks.

Automatic analysis of point dendrometer time series (DTS) registering radial stem variations of trees is of relevant interest to study tree water use and growth. Unfortunately, data from such sensors are often characterized by a large amount of noise that needs to be distinguished by sensors responses induced by biological processes (signal) and irregular fluctuations due to elecrtical disturbances, malfunctions, or external inputs (noise) such as stem flow, perturbation induced by animals, stem temperature and humidity variations. Although some algorithms have been developed to adjust jumps and correct peaks in DTS, it is nowadays challenging to extract biological signals after a large number of corrections and artifacts introduced during denoising processes. In this study, we present an alternative methodology consisting of the first attempt to automatically identify days in which the dendrometers are registering information related to the activity of the tree and relevant for a specific study (days-of-signal). Through (i) per-day temporal segmentation of different stem behaviors, (ii) daily temporal features extraction, and (iii) automatic days-of-signal and days-of-noise discrimination, we automatically analyzed 19 million DTS records acquired during three years by 12 dendrometers installed on xylem and bark at different stem heights from the collar, at the bottom and top-level, of Pinus sylvestris trees. To train and assess the performance of the model, we constructed a reference dataset by labelling 600 daily DTS into days-ofsignal or days-of-noise. As a result of our model application, we detected 3,534 days-of-signal among the altogether 13,152 measurement days with a per sensor overall accuracy, calculated using the reference dataset, ranging between 100% and 82%. Finally, we showed the trend of stem shrinkage and swelling over the three years study period. The large accuracies obtained over the different sensors suggest that our method is versatile and generalizable.

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Grapevine grafting is essential in viticulture, and bench grafting techniques have been developed to mechanize nursery processes and increase yields of viable cuttings. Bench grafting can affect the quality of propagation material and may have a role in young vine decline associated with grapevine trunk diseases. Some authors report that grafting can also influence leaf symptom development in Esca complex of diseases. This study assessed whether three bench grafting methods: omega graft, mechanical technique; whip and tongue graft, manual technique; or full cleft graft, semi-mechanical technique, affected these phenomena. The different methods were compared for their effects on anatomical development of grafting points and xylem function, considering two factors: cultivar (Cabernet Sauvignon, Glera or Teroldego) and scion/rootstock diameter (thin or large). Light microscopy observations of anatomical evolution were correlated with the grafting methods and the investigated varieties. Differences between cultivars and/or grafting methods were detected for areas of necroses on the grafted tissues. Cultivar differences in xylem parameters were also detected, while grafting type had no significant effects. However, graft type affected the intrinsic growth rate. These results confirm the potential for lesions and dysfunctionalities related to grafting method, which could induce decline of grafted vines in vineyards, due to the necrotic area detected on the grafted tissue

The morphological and chemical conformation of wood microstructures is characteristic of individual species and strongly influences the macromechanical properties of the material, as well as its sensitivity to deterioration factors. Noninvasive techniques enabling the visualization of wood microstructures, while simultaneously providing compositional information, can significantly facilitate the analysis of wooden artworks for conservation purposes. In this paper, we present the application of combined two-photon excited fluorescence (TPEF) and second-harmonic generation (SHG) imaging as a versatile diagnostic tool for the microcharacte- rization of three hardwood species never analyzed by this method. Multimodal mapping of the molecular constituents based on the detected nonlinear signals provides useful information for studying the biological and biochemical deterioration of wood, opening a new field of application for a well-established and widely used imaging technology.

Recent climate projections predict a more rapid increase of winter temperature than summer and global temperature averages in temperate and cold environments. As there is relatively little experimental knowledge on the effect of winter warming on cambium phenology and stem growth in species growing in cold environments, the setting of manipulative experiments is considered of primary importance, and they can help to decipher the effect of reduced winter chilling and increased forcing temperatures on cambium reactivation, growth and xylem traits. In this study, localized stem heating was applied to investigate the effect of warming from the rest to the growth phase on cambium phenology, intra-annual stem growth dynamics and ring wood features in Picea abies (L.) H.Karst. We hypothesized that reduced winter chilling induces a postponed cambium dormancy release and decrease of stem growth, while high temperature during cell wall lignification determines an enrichment of latewood-like cells. The heating device was designed to maintain a +5 °C temperature delta with respect to air temperature, thus allowing an authentic scenario of warming. Continuous stem heating from the rest (November) to the growing phase determined, at the beginning of radial growth, a reduction of the number of cell layers in the cambium, higher number of cell layers in the wall thickening phase and an asynchronous stem radial growth when comparing heated and ambient saplings. Nevertheless, heating did not induce changes in the number of produced cell layers at the end of the growing season. The analyses of two-photon fluorescence images showed that woody rings formed during heating were enriched with latewood-like cells. Our results showed that an increase of 5 °C of temperature applied to the stem from the rest to growth might not influence, as generally reported, onset of cambial activity, but it could affect xylem morphology of Norway spruce in mountain environments.

The ongoing climatic change is forcing animal species to cope with global warming and to use different resources to improve their survival. Several species have been favoured by global warming, particularly the alien ones adapted to thrive in tropical and subtropical areas. As to Italian mammals, the crested porcupine Hystrix cristata, a large rodent of tropical African origin, has increased its range in the last 50 years, conquering most of the Northern regions, where it was historically absent. The species usually dig to find its main food, i.e. underground storage plant organs (roots, bulbs, tubers, and rhizomes). Cold months in 2021-2022 have been characterized by a severe drought in Central Italy which prevented porcupines from digging for food search. In this note, we showed that porcupines may adapt to local drought by using a food resource which is commonly avoided, i.e. tree barks. In particular, in Central Italy, the crested porcupine mostly debarked black elders, which show soft barks with medical properties.

Grapevine grafting is an essential practice in viticulture and over the years, various bench grafting techniques have been developed to mechanize the nursery process and to increase the yield in number of viable cuttings. Bench grafting is a fundamental nursery practice that can potentially affect the quality of propagation material also in young decline associated to grapevine trunk diseases and has been recently reported to influence leaf symptoms development associated with diseases of Esca complex. The study aimed to investigate how three bench grafting methods [i.e., (i) Omega graft as mechanical technique, (ii) Whip and Tongue graft as manual technique and (iii) Full Cleft graft as semi-mechanical technique] can influence these phenomena. Specifically, the different methods were compared for their effect on the anatomical development of the grafting point and the functionality of the xylem, also considering two factors: the grapevine cultivar (Cabernet Sauvignon, Glera and Teroldego) and the scion/rootstock diameter (thin and large). Observations by light microscopy on the anatomical evolution and measurements on the xylem morphology and hydraulic traits were correlated with the grafting methods and the investigated varieties. The anatomical observations revealed that the mechanical (Omega) and semimechanical (Full Cleft) grafting methods have a faster callusing response while the manual technique (Whip and Tongue) has a slower but greater vascularization of the differentiated callus. Significant differences between cultivars and/or grafting types were also detected in necrotic area on the grafted tissues. Statistical analysis of the grapevine vessels suggested differences in xylem parameters between cultivars, while grafting type had no significant effects. On the other hand, the grafting type significantly affected the intrinsic growth rate. The study confirms the potential incidence of lesions and dysfunctionalities correlated with the grafting method applied, which can potentially induce grafted vine declines in vineyards due to the necrotic area detected on the grafted tissues.

The global change scenarios highlight the urgency of clarifying the mechanisms driving the determination of wood traits in forest trees. Coniferous xylem is characterized by the alternation between earlywood (EW) and latewood (LW), on which proportions the wood density depend, one of the most important mechanical xylem qualities. However, the molecular mechanisms triggering the transition between the production of cells with the typical features of EW to the LW are still far from being completely elucidated. The increasing availability of omics resources for conifers, e.g., genomes and transcriptomes, would lay the basis for the comprehension of wood formation dynamics, boosting both breeding and gene-editing approaches. This review is intended to introduce the importance of wood formation dynamics and xylem traits of conifers in a changing environment. Then, an up-to-date overview of the omics resources available for conifers was reported, focusing on both genomes and transcriptomes. Later, an analysis of wood formation studies using omics approaches was conducted, with the aim of elucidating the main metabolic pathways involved in EW and LW determination. Finally, the future perspectives and the urgent needs on this research topic were highlighted.

Arundo donax has been recognized as a promising crop for biomass production on marginal lands due to its superior productivity and stress tolerance. However, salt stress negatively impacts A. donax growth and photosynthesis. In this study, we tested whether the tolerance of A. donax to salinity stress can be enhanced by the addition of 5-aminolevulinic acid (ALA), a known promoter of plant growth and abiotic stress tolerance. Our results indicated that root exposure to ALA increased the ALA levels in leaves along the A. donax plant profile. ALA enhanced Na+ accumulation in the roots of salt- stressed plants and, at the same time, lowered Na+ concentration in leaves, while a reduced callose amount was found in the roottissue. ALA also improved the photosynthetic performance of salt-stressed apical leaves by stimulating stomatal opening and preventing an increase in the ratio between abscisic acid (ABA) and indol-3-acetic acid (IAA), without affecting leaf methanol emission and plant growth. Supply of ALA to the roots reduced isoprene fluxes from leaves of non-stressed plants, while it sustained isoprene fluxes along the profile of salt-stressed A. donax. Thus, ALA likely interacted with the methylerythritol 4-phosphate (MEP) pathway and modulate the synthesis of either ABA or isoprene under stressful conditions. Overall, our study highlights the effectiveness of ALA supply through soil fertirrigation in preserving the young apical developing leaves from the detrimental effects of salt stress, thus helping of A. donax to cope with salinity and favoring the recovery of the whole plant once the stress is removed.

The need to understand the carbon sequestration ability of trees under current and future climatic scenarios is fundamental to predict the role of forest in counterbalancing the global warming. In this study, we investigated the carbon sequestration ability of Pinus sylvestris L. in a setting of pure and mixed forests with Quercus petraea (Matt.) Liebl. in Central Poland. Beside the traditional growth measures, i.e., Ring Width, Basal Area Increment, and wood density, we utilized also a new Index called BAIden, which combines Basal Area Increment and mean ring wood density to depict the carbon sequestration ability of trees. Pinus sylvestris showed different sensitivity to climatic variability depending on tree admixture, while the Basal Area Increment and wood density presented few differences between pure and mixed forests. According to the BAIden index, carbon accumulation in P. sylvestris showed similar sensitivity to climatic variability in pure and mixed forests. The new index was also informative on the main climatic drivers of carbon sequestration. Considering future climatic scenarios, the carbon sequestration ability of P. sylvestris will be facilitated by rising temperatures in late winter-early spring and reduced by decreasing precipitation and rising temperatures during summer. Finally, we discussed the perspective and applicability of BAIden for further studies on carbon sequestration ability under climate change.

The morphological and chemical conformation of wood microstructures is characteristic of individual species and strongly influences the macromechanical properties of the material, as well as its sensitivity to deterioration factors. Noninvasive techniques enabling the visualization of wood microstructures, while simultaneously providing compositional information, can significantly facilitate the analysis of wooden artworks for conservation purposes. In this paper, we present the application of combined two-photon excited fluorescence (TPEF) and second-harmonic generation (SHG) imaging as a versatile diagnostic tool for the microcharacterization of three hardwood species never analyzed by this method. Multimodal mapping of the molecular constituents based on the detected nonlinear signals provides useful information for studying the biological and biochemical deterioration of wood, opening a new field of application for a well-established and widely used imaging technology.

The recent climate projections predict that the intensity and frequency of extreme events will increase as a result of overall increasing mean temperature and reduced precipitations in the temperate regions of the Northern Hemisphere. How these changes will influence the harshness of the environment and the performances of trees growing under natural conditions remains an open question. In this commentary article, we would like to look at the concept of suboptimal growth conditions, widening its application from the traditional in vitro manipulation to trees growing in open air, addressing the main limitations and strengths of the upscaling results from cell to tree. We believe that the traditional single dose-effect approach is not suitable to explain the complex interactions between genotype and environment, occurring in open field or forest stands, where the intensity and frequency of the events are uncontrolled and unpredictable. As forests provide a wide range of ecosystem services, new parameters should be considered in the definition of the response thresholds in addition to growth. Thus, within this Special Issue, we stimulate the discussion over the development of new approaches and technologies that are able to define suitable threshold responses of trees under suboptimal natural conditions, with the aim to furnish new insights on the acclimation and adaptation processes in woody species under global change.

In the present study, a cheese whey agro-industrial byproduct was utilized as a natural feedstock for bioplastic production. The bioprocess consisted of a fermentative lactic acid production (step 1) and a following photofermentative poly(3-hydroxybutyrate) production (step 2). During step 1, the bacterium Lactobacillus sp. converted lactose (contained in cheese whey) into lactic acid. During step 2, the marine bacterium Rhodovulum sulfidophilum DSM-1374 converted lactic acid, contained in the cheese-whey fermented effluent (CWFE), in bioplastic. In this investigation, the CWFE produced during step 1 showed a lactic acid content of 29.5 ± 1.3 g/L. When, for feeding Rhodovulum sulfidophilum DSM-1374, was utilized CWFE diluted with water (50 %, v/v) the highest poly(3-hydroxybutyrate) content (67 ± 3.1 % of bacterial dry-biomass) was observed. Both bioprocess steps can significantly contribute to realize a circular bioeconomy able to cut down the costs of bioplastic production and reduce the environmental impact caused by the intensive human feed and food productions.

In their Letter, Elmendorf and Ettinger (1) question the dominant role of photoperiod in driving secondary growth resumption (hereafter referred to as xylem formation onset) of the Northern Hemisphere conifers, recently reported by Huang et al. (2). Their opinions are grounded on the following three aspects, including 1) the seasonality of the photoperiod, 2) the dependence of the predictor variables (e.g., photoperiod, forcing, and chilling) on the response variable (the date of onset of xylem formation, day of the year [DOY]), and 3) the limited value of the obtained models for interannual forecasting. We think they bring up an interesting issue that deserves further discussion and clarification.

Wood formation consumes around 15% of the anthropogenic CO2 emissions per year and plays a critical role in long-term sequestration of carbon on Earth. However, the exogenous factors driving wood formation onset and the underlying cellular mechanisms are still poorly understood and quantified, and this hampers an effective assessment of terrestrial forest productivity and carbon budget under global warming. Here, we used an extensive collection of unique datasets of weekly xylem tissue formation (wood formation) from 21 coniferous species across the Northern Hemisphere (latitudes 23 to 67°N) to present a quantitative demonstration that the onset of wood formation in Northern Hemisphere conifers is primarily driven by photoperiod and mean annual temperature (MAT), and only secondarily by spring forcing, winter chilling, and moisture availability. Photoperiod interacts with MAT and plays the dominant role in regulating the onset of secondary meristem growth, contrary to its as-yet-unquantified role in affecting the springtime phenology of primary meristems. The unique relationships between exogenous factors and wood formation could help to predict how forest ecosystems respond and adapt to climate warming and could provide a better understanding of the feedback occurring between vegetation and climate that is mediated by phenology. Our study quantifies the role of major environmental drivers for incorporation into state-of-the-art Earth system models (ESMs), thereby providing an improved assessment of long-term and high-resolution observations of biogeochemical cycles across terrestrial biomes.

The impact of global changes on forest ecosystem processes is based on the species-specific responses of trees to the combined effect of multiple stressors and the capacity of each species to acclimate and cope with the environment modification. Combined environmental constraints can severely affect plant and ecological processes involved in plant functionality. This study provides novel insights into the impact of a simultaneous pairing of abiotic stresses (i.e., water and ozone (O3) stress) on the responses of oak species. Water stress (using 40 and 100% of soil water content at field capacity--WS and WW treatments, respectively) and O3 exposure (1.0, 1.2, and 1.4 times the ambient concentration--AA, 1.2AA, and 1.4AA, respectively) were carried out on Quercus robur L., Quercus ilex L., and Quercus pubescens Willd. seedlings, to study physiological traits (1. isotope signature [?13C, ?18O and ?15N], 2. water relation [leaf water potential, leaf water content], 3. leaf gas exchange [light-saturated net photosynthesis, Asat, and stomatal conductance, gs]) for adaptation strategies in a Free-Air Controlled Exposure (FACE) experiment. Ozone decreased Asat in Q. robur and Q. pubescens while water stress decreased it in all three oak species. Ozone did not affect ?13C, whereas ?18O was influenced by O3 especially in Q. robur. This may reflect a reduction of gs with the concomitant reduction in photosynthetic capacity. However, the effect of elevated O3 on leaf gas exchange as indicated by the combined analysis of stable isotopes was much lower than that of water stress. Water stress was detectable by ?13C and by ?18O in all three oak species, while ?15N did not define plant response to stress conditions in any species. The ?13C signal was correlated to leaf water content (LWC) in Q. robur and Q. ilex, showing isohydric and anisohydric strategy, respectively, at increasing stress intensity (low value of LWC). No interactive effect of water stress and O3 exposure on the isotopic responses was found, suggesting no cross-protection on seasonal carbon assimilation independently on the species adaptation strategy.