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Cork is the most valuable non-wood product of the cork oak (Quercus suber L.). However, the cork oak sector may be at risk due to climatic and economic pressures on cork oak forests, affecting both the quantity and technological quality of products. At some sites, irrigation may present a solution for stimulating cork growth and thereby increasing production. This study presents an initial approach to characterizing cork grown in a forest stand associated with a specific water regime, by comparing cork growth on two plots—irrigated and a traditional rainfed—over an initial five-year period. Samples of cork tissue were analysed and several parameters were set: cell area, diameter, cell-wall thickness, number of cells, porosity, growth, and density. Irrigation plot samples showed on average: 25.83 ± 3.74 mm thickness, 5.17 ± 1.49 mm cork-ring width, 0.149 ± 0.041 g.cm−3 density, 13 ± 3.4% porosity coefficient in the tangential plane, 407.58 ± 268.22 µm2 cell area in the tangential plane and 887.80 ± 449.14 µm2 in the transverse plane, a total number of cells of 1232 ± 147 per mm2, and 1.03 ± 0.30 µm cell-wall thickness; whereas traditional rainfed plot samples presented: 21.33 ± 5.48 mm thickness, 3.08 ± 1.44 mm cork-ring width, 0.167 ± 0.068 g.cm−3 density, 10 ± 3.5% porosity coefficient in the tangential plane, 304.31 ± 205.83 µm2 cell area in the tangential plane and 752.45 ± 398.94 µm2 in the transverse plane, a total number of cells of 1481 ± 153 per mm2, and 1.204 ± 0.327 µm cell-wall thickness. As regards irrigation, two parameters, ring width and porosity coefficient, proved to be statistically significant, in contrast to density.

The dioxane lignin was isolated from extractives- and suberin-free cork (Quercus suber L.) by a modified acidolytic procedure and submitted to structural analysis by permanganate oxidation, analytical pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC-MS), liquid- and solid-state nuclear magnetic resonance (NMR) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The molecular weight (Mw = 2500 Da) was assessed by size exclusion chromatography (SEC). The results obtained show that the cork lignin is of syringyl (S)/guaiacyl (G) type with a small proportion of p-hydroxyphenyl (H) units (S:G:H molar ratio of 23:72:5). Among a dozen detected lignin structures, those linked by ether bonds, such as β-O-4' (38 mol %) and 4-O-5' (5 mol %), were the most abundant. The frequency of occurrence of β-5', β-β', 5-5', tetrahydrofuran type, and structures arising from the condensation with concomitant procyanidins was assessed. Ferulates were the only cinnamic structure detected in the cork dioxane lignin.

Fruits of the plant Ficus Lacor Buch. Ham. were used traditionally for treatment of diabetes mellitus. The present study was undertaken to evaluate the antidiabetic potential of the plant using in vitro approach. Effect of Ficus Lacor Buch. Ham. was evaluated using α/β -glucosidase, α-amylase and lipase enzyme inhibition assay methods. The glucose absorption in intestine was evaluated using everted rat jejunum while glucose uptake was evaluated using isolated rat hemidiaphragm. Fruit and cork ethanolic extract was prepared by using soxhlation extraction method. In vitro assay of α-glucosidase showed that IC50 value of fruit extract was 83.03 µg/ml and cork extract 88.32 µg/ml when compared with control group acarbose. β-glucosidase enzyme was inhibited by fruit and cork extract of plant with IC50 value of fruit and cork extract 132.71 µg/ml and 171.93 µg/ml. The extracts further quantify α-amylase inhibitory activity of fruit (IC50 77.93 µg/ml) and cork (IC50 111.94 µg/ml) extract. Lipase inhibitory assay indicated the effect of plant extract on lipase enzyme was not prominent when compared to orlistat. Absorption of glucose through everted rat jejunum was reduced significantly (P ? 0.05) when compared with standard metformin. Effect of fruit and cork extract on rat hemidiaphragm exhibited significant (P ? 0.05) increase in glucose uptake when compared with standard metformin. Result suggests Ficus Lacor Buch. Ham. is effective in inhibiting carbohydrate metabolizing enzymes α/β –glucosidase and α-amylase while lipase enzyme was not affected. Fruit and cork extract of the plant was found to reduce significantly glucose absorption in everted rat jejunum. The significant increase in glucose uptake was observed in isolated rat diaphragm. The result reveals that Ficus Lacor Buch. Ham. acts by inhibiting carbohydrate metabolizing enzymes, reducing glucose absorption in intestine and increasing glucose uptake in hemidiaphragm.

In Mediterranean forests, besides the conflict between forest managers and local populations who are often poor and dependent on livestock for survival, the cost of raw materials used in animal feed is increasingly a burden for farmers. There is growing recognition that wise use of acorns can reduce feed costs and enhance sustainable participatory governance of these woodlands. This paper aimed to carry out a quantitative, qualitative and economic evaluation of acorn potential in a cork oak forest in north-western Tunisia and to investigate the impact of their post-dispersal on natural regeneration. Quantities were estimated in November and February, respectively for acorns collected directly from trees and from the ground. Time-dependent monitoring of acorn quality and numbers of new seedlings was also conducted from autumn 2014 to spring 2015. The results show a significant decrease in acorn quantity from 5.28 ± 4.61 t/ha in November to 0.684 ± 0.1 t/ha in February. However, this loss did not put the early stages of natural cork oak regeneration at risk since the percentage of acorns not able to germinate was estimated at only 37% in late February. Furthermore, the average number of new seedlings was estimated in April at 40,000 seedlings/ha. A model was fitted to predict tree acorn production and to establish the best agroforestry system to optimize acorn use. Based on acorn quantity and quality data, earlier acorns should be directed to nursery and livestock production and the later acorns to wildlife and natural regeneration.

Agonandra brasiliensis, ivory wood, is a tree species from the Brazilian cerrado with a bark featuring a thick cork layer. The present study aimed to describe the cellular features and chemical composition of this cork. The cork was investigated regarding cellular structure and biometry, as well as summative chemical composition. The results were compared with those of corks from Quercus suber, as a reference commercial cork, and Kielmeyera coriacea and Plathymenia reticulata, which are native Cerrado cork species. The periderm of A. brasiliensis develops continuously around the stem with a thick cork layer. The cork has the typical characteristics of cork tissues with a compact structure of prismatic cells, stacked base to base in the radial direction without intercellular spaces. Cell walls were heavily corrugated and growth rings were present with a distinction of earlycork and latecork cells. A. brasiliensis cork cells are larger (49.1 µm prism height and 5.5 × 10–5 cm2 base area) than those from the reference Quercus suber cork, the number of cells per unit volume is smaller as well as the fraction of solid volume (7.6%), contributing to a lower density of cork. Chemically A. brasiliensis cork is characterized by a low suberin content of 5.6%, and a high lignin content of 45.5%, and includes 13.6% extractives. The ethanol–water extracts have low phenolic content and weak antioxidant activity. The cork of A. brasiliensis differs considerably from those of Q. suber, P. reticulata and K. coriacea, namely regarding its suberization level, which will impact the mechanical properties and limit the range of commercial applications, that should be directed towards insulation and low-density products.

Plusieurs subéraies du Nord-Est algérien sont sujettes à une invasion par le pin maritime. Cette dynamique forestière qui a débuté dans les années 1980 est souvent citée parmi les facteurs de dégradation des subéraies algériennes mais n’a encore jamais fait l’objet de recherche. L’objectif de notre étude, qui porte sur le cas de la subéraie de Haddada (wilaya d’El-Tarf), était d’identifier les déterminants de l’invasion par le pin maritime, Pinus pinaster Ait., en recourant à une cartographie chorologique de facteurs tels que la pente, l’exposition et les surfaces incendiées en 1994, ainsi qu’une cartographie de la subéraie avant et après l’invasion. L’élaboration des cartes a suivi une approche géomatique complétée par des enquêtes sur le terrain. La cartographie montre que les parties envahies par le pin maritime sont celles qui ont été le plus touchées par l’incendie de 1994, ce qui correspond aussi aux pentes fortes et très fortes. La faible résilience du chêne-liège, Quercus suber, dans ces conditions a permis au pin maritime de le supplanter. Cette dynamique illustre bien le paradigme patch dynamics dans une forêt méditerranéenne, et nous renseigne aussi sur le potentiel invasif du pin maritime, s’agissant d’une espèce se révélant également invasive ailleurs dans le monde. Le changement climatique risque d’accentuer ces processus d’invasion.

Although forest areas have been growing in Europe, some forest types have been declining regionally. Since the 1980 s, there have been reports of defoliation and mortality in evergreen oak woodlands of the Iberian Peninsula. However, long-term and large-scale trends of Iberian oak decline are still poorly understood. We quantified trends in canopy cover for cork oak (Quercus suber) and holm oak (Q. rotundifolia) woodlands in mainland Portugal for a 50 year period (1965 to 2015). We considered loss of canopy cover a proxy of forest degradation and asked how it changed over time, in association with human activity and climate. Between 1965 and 2015, both cork oak and holm oak canopy cover showed declining trends (57.9% and 71.1% of sampling points, respectively). Canopy cover dynamics, however, differed across time. Between 1965 and 1990, canopy cover gains (over 35% of sampling points) prevailed over losses (under 20%), with larger differences for cork oak than holm oak. Between 1990 and 2015, canopy cover losses (over 70% of sampling points) were much higher than gains (under 9%). Oak canopy cover decrease was associated with flatter areas (usually having more intensive land use) for both oak species, higher cattle numbers (holm oak only) and higher mean temperature (cork oak only). Contrastingly, loss of holm oak canopy cover seems to have occurred in less hot and dry regions that enable more intensive land uses. Active restoration is urgently needed to reverse the current decline in canopy cover in Mediterranean evergreen oak woodlands.

Vascular plants with secondary growth develop a periderm mostly composed of dead suberized cork cells to face environmental hostile conditions. Cork oak has a highly active and long-living phellogen forming a remarkably thick periderm that is periodically debarked for industrial purposes. This wounding originates the quick formation of a new traumatic periderm, making cork oak an exceptional model to study the first periderm differentiation during normal development in young sprigs and traumatic (wound) periderm formation after debarking. Here, we studied the poorly known first periderm differentiation steps that involve cell wall suberization, polyphenolic accumulation and programmed cell death (PCD) by combining transmission electron microscopy, histochemical and molecular methods in periderms from young sprigs. These processes were further compared with traumatic periderms formed after wounding using molecular and histochemical techniques, such as the polyphenolic accumulation. In the first periderms from young sprigs, four distinct differentiation stages were defined according to the presence of PCD morphological features. First young and traumatic periderms showed an upregulation of genes related to suberin biosynthesis, proanthocyanidins biosynthesis and transport, autophagy, and PCD. Traumatic periderms revealed an overall upregulation of these genes, likely resulting from ontogeny differences and distinct phellogen origin associated with a faster metabolism, highlighting the impact of wounding on phellogen activity after debarking. First periderms from young sprigs showed gradual accumulation of proanthocyanidins in the vacuoles throughout PCD stages until total filled lumens, whereas in traumatic periderms, these compounds were found cell wall linked in already empty cells. This work enabled a comprehensive overview of the cork cells differentiation processes contributing to deepening the knowledge of the fundamental ontogenic program of this protective tissue, which is also a unique forest product, constituting the basis of a sustainable and profitable industry.

"Published online 17 February 2021", Polyphenols have been extensively exploited in the biomedical field because of their wide range of bioactive properties and historical use as traditional medicines. They typically present antioxidant, antimicrobial, antiamyloidogenic, and/or antitumor activities. In particular, cork water extracts and their components, have been previously reported to present antioxidant and antiamyloidogenic properties. On the basis of this knowledge, we tested cork water extract (CWE), cork water enriched extract (CWE-E), vescalagin/castalagin (two of the main polyphenols present in CWE and CWE-E) for their antibacterial activity against four bacterial strains, namely, methicillin-resistant Staphylococcus epidermidis (MRSE), Staphylococcus aureus (SA), methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa (PA). Vescalagin and castalagin presented bactericidal activity against all the tested bacterial strains, in particular toward the methicillin-resistant ones, i.e., MRSA and MRSE, as well as the ability to inhibit the formation of biofilms and to disrupt preformed ones. Moreover, vescalagin/castalagin seem to modulate the normal assembly of the peptidoglycans at the bacteria surface, promoting the disruption of their cell wall, leading to bacterial cell death. We also demonstrate that vescalagin/castalagin can be loaded into alginate hydrogels to generate antibacterial biomaterials that are not toxic to eukaryotic cells., We acknowledge the financial support from the EC (FORECAST 668983 and MEPHOS 872648). A.R.A. acknowledges the “Programa Operacional Regional do Norte”, “Fundo Social Europeu”, and Norte2020 TERM&SC, for her PhD grant (NORTE-08-5369-FSE-000044).

L’absence d’outils nécessaires pour l’estimation des productions, la gestion et l’aménagement des peuplements de chêne-liège (Quercus suber L.) en Tunisie constitue un handicap pour le développement et la conservation de la suberaie dans le pays. Les objectifs de ce travail étaient de préciser l’impact de l’intensité de démasclage des arbres de chêne-liège sur la croissance et la production du liège, d’élaborer des modèles d’estimation de la croissance et la biomasse du liège à l’échelle de l’arbre, et enfin de vérifier des coefficients de démasclage appliqués en Tunisie et leur impact sur la production nationale de liège. Les données collectées proviennent d’un essai multisites de démasclage et de deux inventaires réalisés dans différents chantiers de démasclage durant deux campagnes successives de récolte de liège. Trois sites expérimentaux représentatifs des forêts productives de chêne-liège en Tunisie ont fait l’objet d’un même essai où trois coefficients de démasclage ont été appliqués sur des arbres appartenant à trois classes de diamètre. Des mesures de l’épaisseur du liège à hauteur de poitrine ont été effectuées annuellement durant une rotation de 12 ans, à la fin de laquelle le liège produit sur chaque arbre a été récolté et pesé. Les résultats obtenus ont montré un effet « coefficients de démasclage » non significatif et un effet « classes de diamètre » très hautement significatif sur la croissance en épaisseur du liège. Le poids de liège récolté est affecté significativement par les coefficients de démasclage et les classes de diamètre. Deux modèles de croissance et de biomasse de liège ont été développés à l’échelle de l’arbre avec des précisions respectives de 96 % et 93 %. Les coefficients de démasclage réellement appliqués en Tunisie varient de 0,6 à 3,6 avec une valeur moyenne de 1,7. Les pertes dans les quantités de liège récolté issues des deux inventaires ont été respectivement estimées, en cas d’application des coefficients de démasclage étudiés (2, 2,5 et 3), à 14 %, 32 % et 50 %.

Cork oak decline and mortality are increasingly prevalent in the Mediterranean basin. This require particular attention due to the great economic value of this plant species. Biscogniauxia mediterranea is one of the most common pathogens highly associated to cork oak decline. However, documentation on its incidence is still scarce, especially in Tunisia. In this context, our research aimed at detecting its presence in Tunisian natural cork oak forests and assessing factors influencing its occurrence. Investigations were carried out in six forests in northwestern Tunisia. Dendrometric parameters of trees, ecological factors (rainfall, temperature, and altitude), and the presence of B. mediterranea as pathogen were determined. The endophytic presence of this fungus was also established. It was detected in all investigated forests, with significantly different frequencies, and was reported to be related to the dendrometric structure of the cork oak trees. On the other hand, the presence of B. mediterranea as pathogen was only detected in Ain Beya and Ain Sarouia forests. It was very limited with 4% of trees per site showing the disease signs. In conclusion, measures to prevent the dispersal of B. mediterranea throughout other cork oak forests shall be implemented in order to conserve such valuable forest resources.

Cork is a renewable resource mainly produced in Mediterranean countries thanks to sustainable management of cork oak (Quercus suber) stands. The infection caused by the ascomycete fungus Diplodia corticola promotes the occurrence of cankers that reduce cork regeneration devaluating the stands. In this article, we tested the hypothesis that the trees are susceptible to the fungus during a limited period of time after debarking. Five mature cork oaks were subjected to eight reiterative inoculations of D. corticola (from the day of debarking to 35 days after) in an experimental plot located in Catalonia (North-Eastern Spain). The time until first symptom appearance as well as the severity of necrosis were assessed for each inoculation treatment. A generalized linear mixed model was fitted showing that the time of symptoms appearance varied among the assayed times of inoculation. In contrast to the foresters-assumed idea of high susceptibility immediately after debarking, earlier inoculations were neither related to higher severity nor to earlier occurrence of canker. This study represents the first approach to this etiological issue in cork oak canker pathosystem.

The phytocenotic variability of the cork oak forests present in the northwesternmost Iberian Peninsula was studied through the analysis of a dataset of 145 new and 39 previously published relevés. The results allowed the recognition of four associations: (1) Arenario montanae-Quercetum suberis ass. nova: thermotemperate xerophytic forests of the Navia River valley (Galice/Asturias boundary); (2) Hedero hibernicae-Quercetum suberis stat. nov.: thermo-(meso-)temperate forests with oceanic influence of the Galician-Portuguese and Inland Galician territories; (3) Physospermo cornubiensis-Quercetum suberis: forests of the mesomediterranean territories of the Sil valley and Lower Bierzo, more thermic and less oceanic than the aforementioned communities; (4) Junipero lagunae-Quercetum suberis: mesomediterranean forests of areas of dry ombroclimate in the NE Portugal. Based on these results, a new interpretation is suggested for the Portuguese cork oak forests that have been considered as belonging to the typical subassociation of Physospermo cornubiensis-Quercetum suberis. The first two associations are part of the phytocenotic transition between the northernmost Mediterranean cork oak forests of the Iberian Peninsula and those present at the SW end of France. The new associations increase the knowledge of the phytosociological variability of habitat type 9330 of Annex I of CD92/43/EEC in the EU.

The uneven presence of the cork oak (Quercus suber L.) within its distribution range is not only determined by its climatic requirements but also by specific edaphic needs. Although most of the natural populations thrive in acidic soils deriving from metamorphic or volcanic rock outcrops, some cork oak populations are found growing in soils deriving from calcareous bedrock, which are considered less suitable. We carried out a multidisciplinary investigation at the south eastern edge of the Q. suber distribution range (Mountains of Palermo, NW Sicily), including soil, floristic, and vegetation surveys, aimed at: (i) assessing the native or introduced origin of some peculiar cork oak populations; (ii) describing the associated plant communities and soils; (iii) identifying the ecological factors which could explain the local adaptation to soils deriving from calcareous bedrock; (iv) discussing the ecological role played by this species in the study area and within its distribution range. The collected information suggest that the detected cork oak stands are native to these areas. We hypothesized that the co-occurrence of high fire frequency, high soil calcium content and erosion, which caused the intermixing of different parent materials, might favor its competitive interactions with other Mediterranean tree species, thus accounting for the local presence of Q. suber. The study of cork oak populations thriving in peculiar substrates at the driest end of the range could be of great importance for the future conservation of this species, which is expected to face growing threats in the coming decades.

Pyrolysis kinetics of Quercus cerris cork was investigated using thermogravimetric analysis with heating rates of 10, 20, 50, and 100 °C min−1. The activation energies and chemical compositions of cork components were determined by different model-fitting methods, isoconversional Kissinger-Akahira-Sunose (KAS) method, and Lorentzian multi-peak fitting. Wet chemical analysis of cork was conducted to compare with the chemical compositions predicted by the kinetic models and Lorentzian multi-peak fitting. The results show that pyrolysis of Quercus cerris cork possibly follows nth-order kinetics, and best fits to the experimental data were obtained by three-halves kinetics followed by first-order and contracting sphere models. The fit qualities of the different models were close implying that the first order models could be used for practical applications. Six pseudo-components approximation used in these models suggested that while cork hemicelluloses and cellulose undergo thermal decompositions similar as in wood, cork suberin decomposes in two distinct steps, i.e., cellulose-like and lignin-like decompositions. Isoconversional KAS method showed that the average activation energy of Quercus cerris cork is approximately 298 kJ mol−1. The reconstructed mass loss curves after Lorentzian multi-peak fitting resulted in smaller activation energies for cork components.

Waste cork and phloem fractions from the bark of Turkey oak (Quercus cerris) were subject to low-temperature pyrolysis between 250 and 325 °C and residence times of 30 or 60 min. The fuel, leaching, and methylene blue adsorption properties of the produced biochars were evaluated for the first time. The results indicate that cork and phloem containing bark fractions have a promising potential for the production of biochars. The pyrolysis process reduces the bark wastes and contributes to their efficient use. The cork and phloem biochars produced above 300 °C showed promising H/C and O/C atomic ratios that were comparable with lignite. Methylene blue adsorption on cork and phloem biochars was inversely affected by pyrolysis temperature and residence time. Activated carbons for soil amendment applications may be produced from the biochars via a steam activation method with optimum temperature and residence time of approximately 300 °C and 30 min in order to harness the nutrient release while avoiding the potential of toxicity from phenolic leaching.

Wildfires may have serious and long-lasting impacts in Mediterranean Basin oak forests. Although cork oak (Quercus suber L.) is usually considered a highly fire-resistant tree species, post-fire recovery is not guaranteed. We assessed the mortality and regeneration of 729 cork oak trees that burned and were cut in six sites with the objective of identifying the main factors affecting the short- to medium-term post-fire recovery. We used linear mixed models to investigate potential relationships among tree stump status at the end of the second and fifth growing seasons and several tree- and site-level variables. Overall tree mortality in the second year was 44% and was negatively affected by bark thickness and positively affected by root exposure, trunk injuries, and diameter, in decreasing order of importance. Between the second and fifth years, mortality increased to 53%, but this increase was only observed in sites with high grazing pressure. Grazing also had a strong negative impact on the growth of basal resprouts, thereby compromising tree recovery. The results give useful information on the need for application of adequate forest management practices (particularly avoiding debarking injuries, soil erosion, and grazing pressure) to increase the resilience of these ecosystems and reduce the negative economic and ecological impacts of wildfires.

The thickness of bark (cork) is of utmost importance for its industrial processing and, therefore, for the sustainable management of cork oak (Quercus suber L.) woodlands. Cork thickness has been reported to decrease from the stem base upwards but, to our knowledge, prediction models have not yet been presented. This study intended to develop reliable models to predict stem profiles of cork thickness. We addressed the relationship between bark thickness and stem height by measuring stem diameters and cork thickness at various stem heights in 76 trees. Through a repeated measure ANOVA, we selected the bark thickness response variables, cork-ring width and cork thickness. A mixed-effect modelling approach was used to fit linear bark thickness curves with stem height. Our results showed that the equations that performed better for cork thickness were functions of the stem relative height and cross-sectional cork area increment. The decreasing trend upwards the stem might lead to underestimation of cork thickness at the base, more than overestimate it at upper stem parts, in relation to the values at breast height, which are generally used to estimate the thickness of the whole cork plank. Furthermore, cork thickness curves were tree size-related, with larger trees exhibiting a steeper reduction in cork thickness upwards the stem.

The structural features of macromolecular components of cork (suberin, lignin, cellulose and hemicelluloses) from Quercus suber L. used for the production of stoppers were assessed after their isolation and purification. Suberin is the major component of cork (ca. 44%) and is constituted mainly by hydroxy fatty acids (C14–C26). Cork lignin was found to be highly condensed (16.2%) and revealed a syringyl:guaiacyl:p-hydroxyphenyl (S:G:H) ratio of 26:71:3 with predominant β-O-4′ (0.38%), β-5′, β-β and tetrahydrofuran (THF) type (totally ca. 27%) structures. Cork lignin also has a remarkable amount of ferulic acid structures, which are considered the binding point between lignin and suberin. The cellulose of cork cells (17.2%) is a typical cellulose I polymorph with a degree of crystallinity (DC) of 70.3% and an average crystallite width of 3.5 nm. The major hemicellulose of cork is glucuronoxylan (near 6.0%) possessing a molar Xylp:MeGlcpA ratio of 14:1.

The aim of this study was to assess the effects on root deformations in Mediterranean cork oaks Quercus suber L. of container size and radicle length at the time of sowing. Acorns at five sowing methods – intact acorns, acorns that had germinated during storage, acorns that had germinated after moist stratification and acorns with radicles (R) less than 5 mm in length, 7 mm to 12 mm in length and more than 15 mm length – were planted individually in WM type containers of 400 cm3, 800 cm3 and 1,200 cm3. At the end of the nursery growth period, the roots of the 1,080 sampled seedlings were examined for root deformities. The experiment results showed that root deformation affected almost half (49%) of the container-grown cork oak seedlings and that the germination status of acorns at the time of planting had a significant effect on root deformations, whereas container volume had no clear effect. The largest number of deformed roots (91%) was observed in seedlings grown from germinated acorns, as compared to 9% of seedlings grown from intact acorns. Planting germinated acorns with radicles 15

In the present study, we tested the effect of amino acids on secondary somatic embryogenesis of Moroccan cork oak (Quercus suber L.). Secondary mature and immature somatic embryos were obtained from primary somatic embryos cultured in N30K medium supplemented with nineteen amino acids. Stimulation of embryogenesis was dependent on the type and concentration of amino acid in the medium. Thus, L-glutamine and L-asparagine at 3.42 mM have been proved to be the most favorable for the formation of functional somatic embryos and the induction of secondary somatic embryos.

Phellodendron amurense is a broad-leaved tree; its outer bark and cork layers are removed and used as a crude medicinal agent known as Phellodendri Cortex. These trees are cultivated for approximately 15 to 20 years, harvested by felling, and processed by separating the outer and inner bark. Conventionally, parts other than the inner bark (i.e., fruit, leaves, and heartwood) remain unused. However, the revenue earned from by-products could contribute to continued cultivation of Phellodendron amurense. Herein, we examined the extraction condition and investigated the content of chlorogenic acid in the leaves of domestic Phellodendron amurense, which possesses antioxidant activity.

Cork cambium (or phellogen) is a secondary meristem responsible for the formation of phelloderm and phellem/cork, which together compose the periderm. In Quercus suber L., the phellogen is active throughout the entire life of the tree, producing a continuous and renewable outer bark of cork. To identify specific candidate genes associated with cork cambium activity and phellem differentiation, we performed a comparative transcriptomic study of Q. suber secondary growth tissues (xylem and phellogen/phellem) using RNA-seq. The present work provides a high-resolution map of all the transcripts identified in the phellogen/phellem tissues. A total of 6013 differentially expressed genes were identified, with 2875 of the transcripts being specifically enriched during the cork formation process versus secondary xylem formation. Furthermore, cork samples originating from the original phellogen (`virgin’ cork) and from a traumatic phellogen (`amadia’ cork) were also compared. Our results point to a shortlist of potentially relevant candidate genes regulating phellogen activity and phellem differentiation, including novel genes involved in the suberization process, as well as genes associated to ethylene and jasmonate signaling and to meristem function. The future functional characterization of some of the identified candidate genes will help to elucidate the molecular mechanisms underlying cork cambium activity and phellem differentiation.

Introduction: Forest management is necessary for forest conservation and the security of natural assets and people; however, forest management can have negative effects on some soil properties. Objective: To determine whether forest management in a Mediterranean forest basin, consisting of Quercus suber L. and Pinus halepensis Mill., causes increased runoff and eroded material at slope level. Materials and methods: Seven land-use units were selected: a) dense forest (no management); b) recently managed cork oak forest, c) recently managed pine forest; d) cork oak forest with two years of management, e) pine forest with two years of management, f) bare terrain with herbaceous vegetation and (g) a forest road. In each area, four rainfall simulations were carried out from a height of 2 m, at a pressure of 1.7 kg·cm-2, equivalent to a rainfall intensity of 60 mm·h-1. An ANOVA was performed and significant differences were verified (post-hoc Tukey test, P Results and discussion: The forest road and the bare terrain, areas devoid of vegetation, produced more runoff (4 to 12 %) than more vegetated areas ( Conclusion: There is no difference in the generation of runoff and erosion in the managed areas, both pine and cork oak, compared to dense or unmanaged forest.

Biscogniauxia mediterranea is a xylariaceous ascomycete responsible for ‘charcoal disease’, the most frequent disease of cork oak in the Mediterranean basin. However, little is known regarding this fungus in North Africa. This is the first report on the morphological and genetic diversity of B. mediterranea populations in Tunisia. A total of forty-eight isolates from cork oak trees, corresponding to three different sites and three tree parts, were identified as B. mediterranea based on morphological and molecular diagnosis. Variability among the isolates was evaluated using morphological traits and microsatellite-primed PCR (MSP-PCR). B. mediterranea isolates showed high variability in culture, specifically in colony color. A high level of genetic diversity within populations and within tree parts was detected (H = 0.417, I = 0.605, and H = 0.415, I = 0.601 respectively). Significant genetic differentiation among populations (GST = 0.116 and ΦST = 0.137; p

Traditional farming landscapes in South and Central Portugal, known as montados, are affected by global socio-economic and biophysical pressures, putting the sustainability of the systems in jeopardy. Cork oak trees (Quercus suber L.) are characteristic features of these complex agro-silvo-pastoral agroforestry systems, delivering a globally important product, cork. The increasingly distant, global scale of decision making and trade can consequently be observed on the local, landscape, scale. In this study, we use a value chain approach to test the concept that landscape products can ensure sustainable management of the landscape of origin. We interviewed agents—cork producers, intermediaries, industrial transformers, and winemakers—about the challenges they perceived in the business and how these were connected to the landscape of origin. We illustrate the network of agents and sub-actors involved in the sector and highlight the most prominent concerns. We conclude that this approach can reveal the major points for determining the future of the montado, and we suggest that collaboration amongst value chain agents can be a pathway to landscape sustainability.

Plant growth promoting rhizobacteria (PGPR) are in increasing demand due to their role in promoting sustainable practices, not only in agriculture but also in forestry. Keeping in mind the future application of PGPR for increasing cork oak sustainability, the aim of this study was to find cork oak PGPR isolates with increased nutrient solubilisation traits, able to promote root morphological changes and/or antagonize cork oak bark phytopathogens. Soils from three cork oak forests with distinct bioclimates (humid, semi-humid and semi-arid) were used for isolating bacteria. From the 7634 colony-forming units, 323 bacterial isolates were biochemically assayed for PGPR traits (siderophores production, phosphate solubilizing and organic acids production), and 51 were found to display all these traits. These PGPR were able to induce root morphological changes on Arabidopsis thaliana, like suppression of primary root growth, increase of lateral roots or root hairs formation. However, the most proficient PGPR displayed specific ability in changing a single root morphological trait. This ability was related not only to bacterial genotype, but also with the environment where bacteria thrived and isolation temperature. Bacteria from semi-arid environments (mainly Bacillus megaterium isolates) could hold a promising tool to enhance plant development. Other isolates (Serratia quinivorens or B. cereus) could be further explored for biocontrol purposes., This work was supported by FEDER funds through COMPETE (Programa Operacional Factores de Competitividade) and by national funds by FCT (Fundação para a Ciência e a Tecnologia) in the framework of the projects SuberControl (PTDC/ASP-SIL/28635/2017), BioISI (UIDB/04046/2020) and CIMO (UIDB/00690/2020).

Foliar water uptake (FWU) occurs in plants of diverse ecosystems; however, the diversity of pathways and their associated FWU kinetics remain poorly resolved. We characterized a novel FWU pathway in two mangrove species of the Sonneratia genus, S. alba and S. caseolaris. Further, we assessed the influence of leaf wetting duration, wet-dry seasonality and leaf dehydration on leaf conductance to surface water (Ksurf ). The symplastic tracer dye, disodium fluorescein, revealed living cells subtending and encircling leaf epidermal structures known as cork warts as a pathway of FWU entry into the leaf. Rehydration kinetics experiments revealed a novel mode of FWU, with slow and steady rates of water uptake persistent over a duration of 12 h. Ksurf increased with longer durations of leaf wetting and was greater in leaves with more negative water potentials at the initiation of leaf wetting. Ksurf declined by 68% between wet and dry seasons. Our results suggest that FWU via cork warts in Sonneratia sp. may be rate limited and under active regulation. We conclude that FWU pathways in halophytes may require ion exclusion to avoid uptake of salt when inundated, paralleling the capacity of halophyte roots for ion selectivity during water acquisition. This article is protected by copyright. All rights reserved.

Cork porosity, due to lenticular channels, varied along the stem of Quercus suber L. Lenticular channels’ area, rather than their number, decreased upwards along the stem. Area decrease was observed regardless of tree size and of its intrinsic porosity. The cork of Quercus suber L. is radially crossed by lenticular channels, defining cork’s natural porosity. It has been suggested that porosity decreases from the stem base upwards, but studies on such variation have not yet been presented. Three main research questions were addressed: (i) how large is the variation of cork porosity upwards along the stem; (ii) how does porosity variation relate with porosity traits, namely the size and number of lenticular channels and (iii) how much does porosity vary with stem height and between trees. We set up a study at tree level to quantify the porosity of cork samples from fixed stem heights. Our statistical modelling approach was based on linear mixed-effects models, given the nested structure of the data. In the model fitting, porosity was described as a function of tree stem height, while the random effects explained the source of variability introduced by different tree size (as given by stem diameter at breast height, Dbh) and porosity (as given by intrinsic porosity, CPbh). The lenticular channels’ area rather than their number consistently decreased up the stem. The area proportion of the lenticular channels in the cork tissue (i.e. porosity coefficient) decreased by about 1.4% per metre upwards along the stem, regardless of tree size and of its porosity. Our findings highlight that the lenticular channels’ traits greatly vary among trees, much more than within-tree, which may be an important clue to predict variations in cork properties, for decision-making on cork oak management.

‘Akituki’ (Pyrus pyrifolia Nakai.) is a very popular and profitable pear cultivar in China. However, its high susceptibility to cork spot disorder has limited its expansion of cultivated area. The mechanisms of cork spot disorder have been discussed extensively, focusing on Ca2+ deficiency, yet no consensus has been made. In this study, we applied nitrendipine (NI) as a Ca2+ uptake inhibitor to explore the role of calcium in cork spot disorder occurrence. Results showed that NI treatment on the fruit remarkably increased the incidence of cork spot disorder, alteration of mineral contents happened at the early developmental stage of the fruit, especially on the outer flesh and the peel of the fruit, and this gap was filled gradually along with the expansion of the fruit. Significant differences in the expression levels of Ca2+ transport-related genes were found in the inner flesh, outer flesh and peel during the fruit growth period. The observation of free Ca2+ localization indicated the intracellular imbalance of Ca2+ in the NI-treated fruit. In conclusion, NI treatment reduced the calcium content in the fruit at an early developmental stage, altered the related expression of genes and influenced the cellular Ca2+ balance in the fruit, which prompted the occurrence of cork spot disorder. Measures for the prevention and control of cork spot disorder should be taken at the early stage of the fruit development in the field.

Research Highlights: Raffaelea quercina sp. nov. is an ophiostomatoid fungus isolated from the ambrosia beetle Platypus cylindrus. The species occurs in symptomatic Portuguese cork oak trees, (Quercus suber L.), exhibiting vegetative decline. Background and Objectives: Quercus suber L. is a species restricted to the Mediterranean basin, of special economic importance as it constitutes the crucial raw material for the cork production industry, in particular for Portugal, the world’s leading producer. Over the last three decades a progressive and alarming decline of cork oak trees has been observed across its distribution area, including Portugal. The ambrosia beetle Platypus cylindrus, commonly known as the oak pinhole borer, establishes symbiotic relationships with fungi from which it depends for survival and for oak colonization. Some of these fungi are ophiostomatoid species of the Raffaelea genus, known as ambrosia fungi associated with ambrosia beetles. Some Raffaelea species exhibit phytopathogenic activity causing wilting and/or death of trees. The objective of the present study is to identify the association between P. cylindrus and Raffaelea species in Portuguese cork oak stands showing symptoms of disease and decline. Materials and Methods: A total of 300 adult insects were collected as they emerged from cork oak logs, sampled from symptomatic trees. Axenic isolates of Raffaelea species were obtained from the beetles and their galleries in the trunks and identified based on morphological features and molecular analysis of the SSU and LSU rDNA regions. Results: Two Raffaelea species were identified, i.e., R. montetyi and a novel Raffaelea species closely related to R. canadensis. The novel species is morphologically and genetically characterized in this study, and erected as Raffaelea quercina M.L. Inácio, E. Sousa &amp, F. Nóbrega, sp. nov. Raffaelea quercina constitutes a new phytopathogenic fungal species associated with P. cylindrus and cork oak trees exhibiting symptoms of vegetative decline. Conclusions: Raffaelea species appear to have a significant role in cork oak decline. Future research on the association between P. cylindrus and Raffaelea species, encompassing the trans-European and North African wide-range of cork oak stands, would further clarify the relationships between ambrosia beetles, associated fungi and cork oak decline, contributing to a better understanding of the phenomena and for strategies aiming to halt the continuous decline of the unique cork oak stands enclosed in the Mediterranean basin.

Cork oak forests (Quercus suber L.) are one the most interesting forest ecosystems in the western Mediterranean Basin. The aim of this technical note is the presentation of the results of a recent survey carried out in the Calabria region (southern Italy) on the current distribution of cork oak forests. At present, there are few isolated forest stands, often small, on both coasts and in some inland areas of the region. In the past the cork oak forests in Calabria were much more widespread; however, the results here presented can support suitable conservation, management and, where possible, the economic valorization of the remaining cork oak stands.

The presence of Cistus and Cytisus in Portugal is a potential source of an autochthonous renewable energy form. Portugal is also a main cork producer leading to large amounts of cork powders and residues, which can be incorporated in new fuel products. The present work studies the combustion of chars from hybrid pellets in a bubbling fluidized bed reactor. The hybrid pellets, made from blends of Cytisus with cork residues, Cistus with Eucalyptus and Cytisus with Cistus, were subsequently carbonized in nitrogen atmosphere at 800 °C, and later cut into smaller and more uniform particles with average lengths of 4.5, 7.5 and 11.5 mm approximately. Combustion tests were carried out at three different bed temperatures, 700, 800 and 900 °C. From the evolution of the overall combustion resistance of batches of these char pellets, kinetic and diffusive data were obtained. Contrary to the standard expected trend, a clear decrease of the overall combustion resistance with temperature increase, the results show that there are some unexpected approximations on the evolution of these overall combustion resistances. This is due to the influence of some ash components upon the combustion kinetics and that in some circumstances such influence overrides the standard temperature dependency.

Assessing the vulnerability of forest ecosystems in the climate change context is a challenging task as the mechanisms that determine this vulnerability cannot be directly observed. Based on the ecological interrelationships between forests and climate, the present review focused on providing current information about vulnerability assessments of cork oak (Quercus suber L.) forests in the Mediterranean basin, especially, in the Kroumirie region (northwest Tunisia), currently under historic extreme drought conditions. From comparing recent findings in this region, we synthesized data on cork oak decline and mortality collected during the historic drought years 1988–1995 period. Climate change impacts cork forest decline, with special interest shown in elevated temperatures and drought; cork oak forest regeneration, and the adaptation of the Kroumirie forest to climate change, are reviewed herein. The studied region has been influenced largely by frequent prolonged drought periods, especially from 1988 to 1995. Droughts were found to consistently have a more detrimental impact on the growth and mortality rates of cork oak populations. Cork oak mortality was recorded for up to 63,622 trees. In the future, more research studies and observational data will be needed, which could represent an important key to understand ecosystem processes, and to facilitate the development of better models that project climate change impacts and vulnerability. The study is useful for researchers and forestry decision makers to develop the appropriate strategies to restore and protect ecosystems, and to help anticipate potential future droughts and climate change.

‘Akizuki’ (Pyrus pyrifolia Nakai) is a dominant Asian pear cultivar with gradually increasing cultivation area in Shandong province. However, this cultivar is found susceptible to cork spot disorder in recent years. In this study, we explored the physiological-biochemical mechanism of cork spot disorder in pear fruit, and investigated the effectiveness of spraying calcium (Ca), boron (B) solution or prohexadione calcium (P-Ca) on cork spot incidence. Cork spotted fruit had the characteristics of significantly larger fruit size with shorter fruit pedicels. Compared with normal fruit, cork spotted fruit had lower content of total soluble solids, soluble and reducing sugar, and vitamin C. In addition, cork spotted fruit accumulated much higher levels of N and Mg, and lower levels of K and P. However, Ca deficiency was not observed in cork spotted fruit, on the contrary, we determined high concentrations of Ca and free Ca2+ in disordered fruit. At the same time, the ratios of K/Ca, Mg/Ca, and (K+Mg)/Ca were significantly lower in cork spotted fruit as compared with normal fruit. Among all treatments, spraying with 3500 times dilution of P-Ca at 15-day intervals from 30 to 90 days after full bloom showed promise for reducing cork spot incidence in ‘Akizuki’ pear without affecting fruit quality attributes. This research herein reveals the physiological-biochemical characteristic of cork spot disorder, and implicates P-Ca as a potential tool to reduce cork spot incidence in Asian pear cultivar Akizuki.

Climate scenarios in the Mediterranean region predicts raising temperatures and more frequent and extreme drought conditions. Cork oak is a Mediterranean species with a large distribution in Portugal from which cork is extracted in a sustainable way and mainly used as the raw material for cork stoppers and insulating materials. To study the response of cork oak to drought and the effect of phellogen age on that response we examined cork growth from a 30-year chronology of trees from 12 sites in the main Portuguese cork oak production area. For the first time in cork, a components resilience study was performed. The research confirmed that drought reduces cork growth and provided extra knowledge on the responses of cork oak to drought: more severe droughts correspond to higher decrease of cork growth and more trees affected but to greater recovery performance. Moreover, cork oak is very tolerant and resilient to extreme droughts. Nevertheless, there are other factors that affect cork growth during and after drought, namely site, tree and the age of the phellogen. In fact, in the first 2 years and in the last 2 years of the production cycle the effects of drought on growth are more pronounced than in the middle of the cycle. The age of the phellogen is significant in the recovery, resistance and resilience but not in the relative resilience. The most noticeable differences occurred in the recovery for phellogen under 3 years (17% lower than that for phellogen with 3 to 6 years of age). Moreover, under drought conditions, there is a strong evidence that forest managers should enlarge debarking rotations, namely if drought occurs in the first 2 years of the production cycle and/or establish new cork oak stands in more humid areas, namely, in higher latitudes than the actual species distribution area.

To investigate the role of seeds origin in drought tolerance, the response to water deprivation of cork oak seedlings differing in climatic conditions at their geographical origin was compared. Gafour is the provenance from the driest site and Feija is the provenance from the wettest site. Net photosynthesis (An), stomatal conductance (gs) and leaf water potential were measured during dehydration. A delayed decrease in leaf water potential is observed after water withholding in Gafour as compared to Feija leaves. At the onset of dehydration, An and gs were higher in Feija. After withholding watering, Gafour leaves were able to maintain a higher An and gs than Feija leaves. Most likely, drought tolerance in Gafour leaves is associated to their lower gs under well-hydrated conditions. The stomatal density (Ds) and specific leaf area (SLA) were not different in well-watered leaves but, leaf hydraulic conductance was lower in Gafour leaves when compared to Feija leaves. Our results suggested that lower stomatal and hydraulic conductances of Gafour leaves could be involved in bringing about the better resistance to dehydration.

Cork powder, an abundant, natural, and cheap byproduct of the cork stopper industry was explored, either in its natural form or after improvement of their adsorption properties by simple physicochemical treatments, as a new sustainable wine fining agent for removing negative volatile phenols (VPs), responsible for one of the most frequent and widespread aroma defects in red wine known as “Brett character”. Cork adsorptive performance improvement by removal of cork extractives, air removal, and ethanol impregnation allowed us to obtain 41% to 62% of 4-ethylphenol (4-EP) and 50% to 53% of 4-ethylguaiacol (4-EG) removal from red wine. Performance of the optimized cork powder on removing the negative sensory phenolic defect and recovery of the positive fruity and floral sensory attributes was not significantly different from activated carbon and chitosan, two of the most efficient treatments currently available. Optimized cork powder can be a good solution for VPs removal without impacting negatively on wine ...

Quercus suber forests are very important, both economically and ecologically, in countries from the Mediterranean basin. Quercus suber bark or cork is obtained from the outer bark of this tree and it is the base of many commercial and profitable products. The industry around cork extraction and transformation leads to the production of considerable amounts of by-products, some of them considered as waste. Cork and its by-products can be an important source of multiple bioactive components, such as phenolic acids, terpenoids and tannins. These natural products present a wide variety of relevant properties, namely antioxidant, anti-inflammatory, antiaging, radical scavenger and depigmenting activity. Thus, cork and its by-products can be reused as promising ingredients in topical products. They may be used in different pharmaceutical and cosmetic applications, such as skin ageing prevention and skin depigmenting activity or as complements in acne treatment and skin inflammatory processes. The heterogeneity of its chemical composition and its extraordinary properties make cork a material with a lot of potential and considerable importance. Reusing and valorising cork by-products in the cosmetic field fits with the current sustainable perspective. In this literature review, the different cork by-products and their bioactive compounds are presented and the promising application of these wastes as cosmetic and pharmaceutical ingredients is analysed.

Quercus suber (cork oak tree) is an excellent epicormic resprouter that can keep cambium alive after high-intensity fires because of its plan traits, mainly its thick cork. Although tree bark harvesting is an important source of income, it may reduce protection against wildfires. This study aims to identify stem and cork characteristics that affect the probability of reaching lethal cambial temperature and hence the probability of survival of living tissues. Cork flammability was analyzed using a sample set comprised of 120 cork specimens and 120 cork pieces. Five experimental fires were used to test the results obtained at bench scale. Bench-scale flammability experiments could not simulate the real heat spread and presence of highly volatile isoprenoids. The results revealed differences in cambial temperature and lethal temperature rate (LTR) at both scales according to corkback roughness and cork quality. Peak cambial temperature and LTR show an increase in stems characterized by maximum roughness and worse cork quality. The LTR measurements showed a 30% difference between bench and field scales (0.35 mm s−1 and 0.5 mm s−1, respectively). The findings indicate that corkback roughness, cork thickness, cork porosity and cork quality could influence the vulnerability of cork oak forests to wildfires. A negative correlation was found between total thickness and cambial temperature. A total thickness of over 3.7 cm prevented reaching lethal cambial temperature. Forest managers can use this information to define silviculture and design forest treatments with a view to reducing fire severity and mitigating the ecological and socioeconomic impacts of fire in cork oak forests.

Ponytail palm (Beaucarnea recurvata Lemaire) is a succulent plant indigenous to Mexico frequently used as an ornamental plant throughout the world. The mature trees develop a thick corky outer bark that was studied here for the first time and compared with cork of Quercus suber Linnaeus (cork oak) and other species. The anatomical structure of ponytail palm cork showed a typical honeycomb structure in the tangential section and a brick-wall layer in the transverse section. The cells were larger and had thicker cell walls than those of Q. suber cork. Ponytail palm cork had a distinct growth ring pattern but the cell wall undulation lacked the regular wave pattern as in Q. suber cork. Fiber-like cellular structures were present protuberating from the lenticular channels. Ponytail palm cork chemically differs from Q. suber and other corks by a much lower content of suberin and enhancement of the lignocellulosic nature (18.2% extractives, 11.8% suberin, 29.7% lignin and 39.0% polysaccharides). Although in general similar to that of Q. suber cork, suberin composition of ponytail palm cork has specific features namely regarding the ratio of ɑ,ω-diacids and ω-substituted hydroxyacids and presence of higher amounts of alkanoic acids. The lignin of ponytail palm cork is a HGS-type of lignin (1:12:5) with a S/G ratio of 0.4. These results add to data showing that monomeric composition of suberin and lignin of corks are species’ specific. The lipophilic extractives included mainly saturated alkanoic acids and sterols while the polar extractives showed overall low amount of phenolics and unremarkable antioxidant properties.