Search

Quercus pyrenaica Willd thrives in the intermediate zone between the Mediterranean sclerophyllous and the temperate deciduous forest. In December 2022, the presence of the bacteria Xylella fastidiosa (Xf) was confirmed in samples collected from a Quercus pyrenaica located in Sabrosa, Vila Real, Portugal. Following Xf infection, the transport of water and nutrients is hindered due to the occlusion of xylem vessels. This loss of hydraulic conductivity may lead to vessel blockage and subsequent embolism formation. The objective of this study was to investigate the interaction between Xf and Quercus pyrenaica tissues, as well as the mechanism by which the bacteria can spread through the plant's xylem vessels, ultimately resulting in the formation of vascular plugs. At the time of the sample collection (10 months post-detection), symptoms of Bacterial Leaf Scorch (BLS) began to appear. Examination of xylem vessels using both light and scanning electron microscopy (SEM) revealed the presence of various types of occlusions, predominantly tyloses. Additionally, fibrillar networks, gums, starch grains, and crystals were observed. The stem vessels exhibited significantly more occlusions compared to the leaves. Furthermore, individual bacterial cells were observed to be attached to the vessel wall. This implies that occlusions were primarily induced by tyloses and gums as a defensive response to the invasion of vascular pathogens, in addition to the pathogen itself. This study highlights the presence of starch grains in stems, which may function as a refilling mechanism, thereby preventing the loss of hydraulic conductivity in plants and potentially acting as a means to entrap the bacteria. These mechanisms exemplify the constitutive defense systems of the plant against Xf. Understanding the interaction between Xylella fastidiosa and Quercus pyrenaica is crucial, given that the latter species occupies nearly 95% of the natural distribution area of Portugal.

The study was conducted on eleven Calamus species viz., C. acanthospathus, C. erectus, C. flagellum, C. floribundus, C. gracilis, C. inermis, C. khasianus, C. latifolius, C. leptospadix, C. nambariensis and C. nambariensis subsp. arunachalensis collected from three districts of Arunachal Pradesh with an aim to investigate their anatomical characteristics. Five matured stems of each species were randomly collected and anatomical characteristics were studied at bottom, middle and top positions of the stems. Lumina shape was rectangular in C. acanthospathus, tubular in C. floribundus and C. nambariensis subsp. arunachalensis, irregular in C. erectus and C. flagellum, drop shape in C. gracilis, C. leptospadix and C. nambariensis, club shape in C. inermis, conical in C khasianus and conical and rectangular in C. latifolius. Type-b vascular bundles in C. acanthospathus, C. floribundus, C. gracilis, C. inermis, C. latifolius and C. nambariensis; Type-b and c vascular bundles in C. nambariensis subsp. arunachalensis; Type-b and d vascular bundles in C. erectus and C. khasianus; Type-d vascular bundles in C. flagellum and C. leptospadix were observed. Parenchyma was Type-A in C. acanthospathus, C. erectus, C. flagellum, C. gracilis, C. inermis, C. khasianus, C. latifolius and C. nambariensis; Type-B in C. floribundus, C. leptospadix and C. nambariensis subsp. arunachalensis. Parenchyma and fibre percentage were highest in C. flagellum and C. nambariensis respectively. Vessel percentage was highest in C. acanthospathus. All the anatomical characteristics exhibited significant variations within and among selected species and can be used for identification of the Calamus species. [ABSTRACT FROM AUTHOR]

Quercus pyrenaica Willd thrives in the intermediate zone between the Mediterranean sclerophyllous and the temperate deciduous forest. In December 2022, the presence of the bacteria Xylella fastidiosa (Xf) was confirmed in samples collected from a Quercus pyrenaica located in Sabrosa, Vila Real, Portugal. Following Xf infection, the transport of water and nutrients is hindered due to the occlusion of xylem vessels. This loss of hydraulic conductivity may lead to vessel blockage and subsequent embolism formation. The objective of this study was to investigate the interaction between Xf and Quercus pyrenaica tissues, as well as the mechanism by which the bacteria can spread through the plant's xylem vessels, ultimately resulting in the formation of vascular plugs. At the time of the sample collection (10 months post-detection), symptoms of Bacterial Leaf Scorch (BLS) began to appear. Examination of xylem vessels using both light and scanning electron microscopy (SEM) revealed the presence of various types of occlusions, predominantly tyloses. Additionally, fibrillar networks, gums, starch grains, and crystals were observed. The stem vessels exhibited significantly more occlusions compared to the leaves. Furthermore, individual bacterial cells were observed to be attached to the vessel wall. This implies that occlusions were primarily induced by tyloses and gums as a defensive response to the invasion of vascular pathogens, in addition to the pathogen itself. This study highlights the presence of starch grains in stems, which may function as a refilling mechanism, thereby preventing the loss of hydraulic conductivity in plants and potentially acting as a means to entrap the bacteria. These mechanisms exemplify the constitutive defense systems of the plant against Xf. Understanding the interaction between Xylella fastidiosa and Quercus pyrenaica is crucial, given that the latter species occupies nearly 95% of the natural distribution area of Portugal. [ABSTRACT FROM AUTHOR]

Riparian alder forests are threatened by Phytophthora across Europe. Comparative studies of the pathogenicity of Phytophthora species are crucial for developing effective management strategies. Although only a limited number of species, particularly P. × alni, lead to tree decline in natural environments, many species demonstrate pathogenicity in inoculation trials. Phytophthora species vary in their ability to infect different tissues, such as phloem and xylem, and trigger defence responses in the host through the formation of tyloses and callose. By comparing the histological responses of alder to various Phytophthora species, we can gain insights into the success of P. × alni and the potential damage that could be caused by other species. To investigate the defence strategies of black alder (Alnus glutinosa) against attack by Phytophthora and Halophytophthora species present in Catalonia (NE Spain), we conducted inoculation trials on saplings using nine potentially pathogenic species and compared the histological responses. Phytophthora × alni and P. plurivora were the most aggressive species followed by other exotic species such as P. × cambivora and P. cactorum. Phytophthora × alni and P. plurivora were equally damaging despite the higher prevalence of P. × alni in declining alders in natural settings. Although P. × alni mainly invaded the phloem, P. plurivora also invaded the xylem and triggered the production of tyloses. Histological analyses revealed a diverse range of plant responses to infection by Phytophthora species, providing a better understanding of their adaptability in natural environments compared with solely observing lesions. The low level of callose production in saplings inoculated with P. × alni compared with callose production in saplings inoculated with less pathogenic species suggests that P. × alni can evade recognition by the host and, hence, could partially explain its success. [ABSTRACT FROM AUTHOR]

Grapevines require pruning procedures to maintain plant morphology and ensure productivity, and these procedures cause wounds that induce physical and biological host defence mechanisms. Grapevine tissue reactions to wounding resulting from four different pruning methods were assessed. Rapid (immediate) defence reactions were detected in 1-year-old canes with preserved basal buds. Formation of tyloses (≈ 90% of xylem vessels) was observed 1 month later on canes where the basal buds were maintained and no short stubs were left (i.e. the pruning cuts preserved the buds). At 2 months after pruning, lignin was slightly increased in cortical parenchyma after pruning of 3-year-old grapevine wood. Neither callose nor suberin production was observed in healing wounds, as is known in other fruit or broadleaf trees. In 3-year-old canes, fungal hyphae were observed in the non-active wood below the pruning cut surfaces. Preliminary observations of desiccation cones within canes confirmed that the basal buds preserved the canes from desiccation, after comparing different pruning procedures on canes of the same age. After 9 months, the desiccation cones were greater in 3- than 1-year-old wounds. [ABSTRACT FROM AUTHOR]

Summary: Priming is an adaptive mechanism that fortifies plant defense by enhancing activation of induced defense responses following pathogen challenge. Microorganisms have signature microbe‐associated molecular patterns (MAMPs) that induce the primed state. The lipopolysaccharide (LPS) MAMP isolated from the xylem‐limited pathogenic bacterium, Xylella fastidiosa, acts as a priming stimulus in Vitis vinifera grapevines. Grapevines primed with LPS developed significantly less internal tyloses and external disease symptoms than naive vines.Differential gene expression analysis indicated major transcriptomic reprogramming during the priming and postpathogen challenge phases. Furthermore, the number of differentially expressed genes increased temporally and spatially in primed vines, but not in naive vines during the postpathogen challenge phase.Using a weighted gene co‐expression analysis, we determined that primed vines have more genes that are co‐expressed in both local and systemic petioles than naive vines indicating an inherent synchronicity that underlies the systemic response to this vascular pathogen specific to primed plants.We identified a cationic peroxidase, VviCP1, that was upregulated during the priming and postpathogen challenge phases in an LPS‐dependent manner. Transgenic expression of VviCP1 conferred significant disease resistance, thus, demonstrating that grapevine is a robust model for mining and expressing genes linked to defense priming and disease resistance. [ABSTRACT FROM AUTHOR]

Xylem anatomy may change in response to environmental or biotic stresses. Vascular occlusion, an anatomical modification of mature xylem, contributes to plant resistance and susceptibility to different stresses. In woody organs, xylem occlusions have been examined as part of the senescence process, but their presence and function in leaves remain obscure. In grapevine, many stresses are associated with premature leaf senescence inducing discolorations and scorched tissue in leaves. However, we still do not know whether the leaf senescence process follows the same sequence of physiological events and whether leaf xylem anatomy is affected in similar ways. In this study, we quantified vascular occlusions in midribs from leaves with symptoms of the grapevine disease esca, magnesium deficiency and autumn senescence. We found higher amounts of vascular occlusions in leaves with esca symptoms (in 27% of xylem vessels on average), whereas the leaves with other symptoms (as well as the asymptomatic controls) had far fewer occlusions (in 3% of vessels). Therefore, we assessed the relationship between xylem occlusions and esca leaf symptoms in four different countries (California in the USA, France, Italy and Spain) and eight different cultivars. We monitored the plants over the course of the growing season, confirming that vascular occlusions do not evolve with symptom age. Finally, we investigated the hydraulic integrity of leaf xylem vessels by optical visualization of embolism propagation during dehydration. We found that the occlusions lead to hydraulic dysfunction mainly in the peripheral veins compared with the midribs in esca symptomatic leaves. These results open new perspectives on the role of vascular occlusions during the leaf senescence process, highlighting the uniqueness of esca leaf symptoms and its consequence on leaf physiology. [ABSTRACT FROM AUTHOR]

Xylella fastidiosa is a Gram-negative bacterial plant pathogen with an extremely wide host range. This species has recently been resolved into subspecies that correlate with host specificity. This review focuses on the status of X. fastidiosa pathogenic associations in plant hosts in which the bacterium is either endemic or has been recently introduced. Plant diseases associated with X. fastidiosa have been documented for over a century, and much about what is known in the context of host-pathogen interactions is based on these hosts, such as grape and citrus, in which this pathogen has been well described. Recent attention has focused on newly emerging X. fastidiosa diseases, such as in olives.TaxonomyBacteria; Gammaproteobacteria; family Xanthomonadaceae; genus Xylella; species fastidiosa.Microbiological propertiesGram-negative rod (0.25-0.35 × 0.9-3.5 μm), non-flagellate, motile via Type IV pili-mediated twitching, fastidious.Host rangeXylella fastidiosa has a broad host range that includes ornamental, ecological and agricultural plants belonging to over 300 different species in 63 different families. To date, X. fastidiosa has been found to be pathogenic in over 100 plant species. In addition, it can establish non-symptomatic associations with many plants as a commensal endophyte. Here, we list the four distinct subspecies of X. fastidiosa and some of the agriculturally relevant diseases caused by them: X. fastidiosa ssp. fastidiosa causes Pierce's disease (PD) of grapevine (Vitis vinifera); X. fastidiosa ssp. multiplex causes almond leaf scorch (ALS) and diseases on other nut and shade tree crops; X. fastidiosa ssp. pauca causes citrus variegated chlorosis (CVC) (Citrus spp.), coffee leaf scorch and olive quick decline syndrome (OQDS) (Olea europaea); X. fastidiosa ssp. sandyi causes oleander leaf scorch (OLS) (Nerium oleander). Significant host specificity seemingly exists for some of the subspecies, although this could be a result of technical biases based on the limited number of plants tested, whereas some subspecies are not as stringent in their host range and can infect several plant hosts.Disease symptomsMost X. fastidiosa-related diseases appear as marginal leaf necrosis and scorching of the leaves. In the case of PD, X. fastidiosa can also cause desiccation of berries (termed 'raisining'), irregular periderm development and abnormal abscission of petioles. In olive trees affected with OQDS, leaves exhibit marginal necrosis and defoliation, and overall tree decline occurs. Plants with ALS and OLS also exhibit the characteristic leaf scorch symptoms. Not all X. fastidiosa-related diseases exhibit the typical leaf scorch symptoms. These include CVC and Phony Peach disease, amongst others. In the case of CVC, symptoms include foliar wilt and interveinal chlorosis on the upper surfaces of the leaves (similar to zinc deficiency), which correspond to necrotic, gum-like regions on the undersides of the leaves. Additional symptoms of CVC include defoliation, dieback and hardening of fruits. Plants infected with Phony Peach disease exhibit a denser, more compact canopy (as a result of shortened internodes, darker green leaves and delayed leaf senescence), premature bloom and reduced fruit size. Some occlusions occur in the xylem vessels, but there are no foliar wilting, chlorosis or necrosis symptoms . USEFUL WEBSITES: http://www.piercesdisease.org/; https://pubmlst.org/xfastidiosa/; http://www.xylella.lncc.br/; https://nature.berkeley.edu/xylella/; https://ec.europa.eu/food/plant/plant_health_biosecurity/legislation/emergency_measures/xylella-fastidiosa_en.

Key message: Relative susceptibility to laurel wilt among clonal, non-grafted avocado trees of different ecotypes is relate to the xylem vessel diameter, with larger vessels potentially allowing more rapid movement of fungal conidia in the transpiration stream, creating a potential for faster colonization of the vascular system by the pathogen. Laurel wilt, caused by the fungus Harringtonia lauricola, is a devastating vascular disease prevalent in avocado (Persea americana Mill.) orchards in Florida, where it has caused significant tree losses. Differential susceptibility to laurel wilt has been observed among grafted trees of three avocado ecotypes, Guatemalan (G), and West Indian (WI), and Mexican (M) with grafted WI cultivars reportedly the most susceptible. It has been suggested that differential susceptibility among ecotypes is related to the rate of xylem sap flow as affected xylem vessel size and density. This study compared laurel wilt susceptibility among representative clonally propagated, non-grafted cultivars of three ecotypes (G, WI, and M × G) in relation to xylem vessel anatomy, xylem sap flow rate, net CO2 assimilation (A), stomatal conductance (gs), transpiration (E), intrinsic water use efficiency (WUE), the leaf chlorophyll index (LCI), the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm) and hydraulic conductance (Kh). Laurel wilt negatively affected all physiological variables measured and caused a profuse development of tyloses that blocked the xylem vessels and inhibited xylem sap flow in trees of each ecotype. Differences in disease susceptibility were observed among ecotypes, which were related to xylem vessel size, xylem sap flow, and the development of tyloses in xylem vessels. Trees of the ecotype with the greatest inherent functional xylem vessel diameter and sap flow rates were more susceptibility to the disease after inoculation with H. lauricola. Trees of the M × G ecotype formed the most tyloses which blocked the xylem vessels resulting in a greater decrease in sap flow compared to trees of the other ecotypes. [ABSTRACT FROM AUTHOR]

This study was conducted to devise ways of promoting the use of deciduous trees that have increased in number with climate change. For six oak species commonly utilized to produce liquor barrels, normal wood and tension wood were classified by part. Then, both large vessel lumen area and tyloses were quantitatively assessed. The findings showed that in both normal and tension woods, large vessel lumen area was largest in sapwood, followed by heartwood and juvenile wood. Tyloses were found in both normal and tension woods of all the six species, but the number of tyloses varied according to species. It was heart wood that contained the highest amount in both normal and tension woods. It was also revealed that the number of tyloses decreased with the growing area of large vessel lumen. This study will provide fundamental data to decide oak tree species for the production of liquor barrels. [ABSTRACT FROM AUTHOR]

A taxonomic study carried out in Assam and recorded additional features in Calamus meghalayensis that included the length of the stem, nature of leaf, inflorescence branching order and the first report on extended bracts of inflorescence rachis. In stem anatomy, few metaxylem were observed with more than one vessels, and also found filled with tylose-like structure. [ABSTRACT FROM AUTHOR]

Abstract The purpose of this paper was to confirm the influence of pulsive pressure waves on the liquid penetration into wood in the semi-opened container. Wood block sample was irradiated by the pulsive pressure waves in the semi-opened container filled with water used as a liquid. The irradiation was also performed in the closed container for the comparison. The water penetration into the sample was promoted by the pressure-wave irradiation. There was little difference in the degree of the penetration between the closed and the semi-opened containers. It was presumed from the measured hydraulic pressure that the pressure-wave energy irradiated on the sample in the closed container was higher than that in the semi-opened container. It was also presumed that the cavitation generation was promoted in the semi-opened container. This indicates that the cavitation as well as the pressure waves themselves affected the liquid penetration into wood. The compressive deformation of the sample irradiated in the semi-opened container was slightly smaller than that in the closed container. This indicates that the pulsive pressure-wave irradiation in the semi-opened container promoted the liquid penetration into wood with less compressive deformation.

ABSTRACT Hydrological processes in forest stands are mainly influenced by tree species composition and morpho-physiological characteristics. Few studies on anatomical patterns that govern plant hydraulics were conducted in tropical forest ecosystems. Thus, we used dye immersion to analyze sapwood area patterns of 34 trees belonging to 26 species from a terra firme forest in the central Brazilian Amazon. The sapwood area was related with wood anatomy and tree size parameters (diameter-at-breast-height - DBH, total height and estimated whole-tree volume). Exponential allometric equations were used to model sapwood area using the biometrical variables measured. Sapwood area traits (cross-section non-uniformity and heartwood visibility) varied significantly among and within species even though all were classified as diffuse porous. DBH was strongly and non-linearly correlated with sapwood area (R 2 = 0.46, P < 0.001), while no correlation was observed with vessel-lumen diameter (P = 0.94) and frequency (P = 0.58). Sapwood area and shape were also affected by the occurrence of vessel obstruction (i.e., tyloses), hollow stems and diseases. Our results suggest that sapwood area patterns and correlated variables are driven by intrinsic species characteristics, microclimate and ecological succession within the stand. We believe that individual tree sapwood characteristics have strong implications over water use, hydrological stand upsaling and biomass quantification. These characteristics should be taken into account (e.g., through a multi-point sampling approach) when estimating forest stand transpiration in a highly biodiverse ecosystem.

Hydraulic failure has been extensively studied during drought-induced plant dieback, but its role in plant-pathogen interactions is under debate. During esca, a grapevine (Vitis vinifera) disease, symptomatic leaves are prone to irreversible hydraulic dysfunctions but little is known about the hydraulic integrity of perennial organs over the short- and long-term. We investigated the effects of esca on stem hydraulic integrity in naturally infected plants within a single season and across season(s). We coupled direct (k s ) and indirect (k th ) hydraulic conductivity measurements, and tylose and vascular pathogen detection with in vivo X-ray microtomography visualizations. Xylem occlusions (tyloses) and subsequent loss of stem hydraulic conductivity (k s ) occurred in all shoots with severe symptoms (apoplexy) and in more than 60% of shoots with moderate symptoms (tiger-stripe), with no tyloses in asymptomatic shoots. In vivo stem observations demonstrated that tyloses occurred only when leaf symptoms appeared, and resulted in more than 50% loss of hydraulic conductance in 40% of symptomatic stems, unrelated to symptom age. The impact of esca on xylem integrity was only seasonal, with no long-term impact of disease history. Our study demonstrated how and to what extent a vascular disease such as esca, affecting xylem integrity, could amplify plant mortality through hydraulic failure. [ABSTRACT FROM AUTHOR]

Xylem vascular wilt pathogens cause devastating diseases in plants. Proliferation of these pathogens in the xylem causes massive disruption of water and mineral transport, resulting in severe wilting and death of the infected plants. Upon reaching the xylem vascular tissue, these pathogens multiply profusely, spreading vertically within the xylem sap, and horizontally between vessels and to the surrounding tissues. Plant resistance to these pathogens is very complex. One of the most effective defense responses in resistant plants is the formation of physico-chemical barriers in the xylem tissue. Vertical spread within the vessel lumen is restricted by structural barriers, namely, tyloses and gels. Horizontal spread to the apoplast and surrounding healthy vessels and tissues is prevented by vascular coating of the colonized vessels with lignin and suberin. Both vertical and horizontal barriers compartmentalize the pathogen at the infection site and contribute to their elimination. Induction of these defenses are tightly coordinated, both temporally and spatially, to avoid detrimental consequences such as cavitation and embolism. We discuss current knowledge on mechanisms underlying plant-inducible structural barriers against major xylem-colonizing pathogens. This knowledge may be applied to engineer metabolic pathways of vascular coating compounds in specific cells, to produce plants resistant towards xylem colonizers. [ABSTRACT FROM AUTHOR]

Due to the physiological differences in the juvenile and adult phases of teak wood, differentiation occurs in the impregnation by extractive materials along the heartwood regions, assuming that there is also a significant variation in the permeability of this material. Thus, the study aimed to evaluate the influence of age on the heartwood / sapwood ratio (H/S), permeability, and extractives content of Tectona grandis L.f wood. Four ages (10, 12, 14, and 16 years) and four trees (repetitions) were evaluated, totaling 16 samples. The H/S ratio, extractive content, and wood permeability were determined, in addition to the average and maximum permeability among all ages selected for calculation of their porosity. The H/S ratio increased over the ages of 10 and 16, and the content of extractive materials increased until the age of 14. There was a high heterogeneity between the permeability values of the wood at all ages analyzed, and one of the possible explanations for this fact is the presence of tyloses in different places on the trunk and the arrangement of the pores around the growth rings. [ABSTRACT FROM AUTHOR]

Mango burl is an important disease affecting many mango plantations in India and causes great loss in yield and decrease of vigour. We carried out a diagnostic survey for burl disease (sometimes also referred to as crown gall) in different varieties of mango (Mangifera indica L., Anacardiaceae) throughout India during 2015 and 2016. More than 500 mango genotypes were screened for disease susceptibility and more than twenty-three mango genotypes in different parts of India were found susceptible to this disease. Burls initiate as small tumorous growths and become more pronounced as warty outgrowths with the increasing age of the individual tree. Samples of burl were collected from all popular varieties from different parts of the country and subjected to histological investigations. The present study confirms that mango burl disease is caused by Agrobacterium tumefaciens using evidence from the "carrot assay" and molecular identification of the presumed causal organism. The latter was isolated and inoculated on carrot disks to induce typical symptoms. The xylem of the burl tissue was deformed and showed no specific orientation of the wood cells. Dimensional details and morphology of xylem cells vary at different positions within the burl. In a 10 cm diameter burl, the marginal portion showed xylem cells in circular arrangement. Vessel elements and fibres were very short while rays were relatively low and biseriate rays were observed rarely. Orientation of the xylem tissue was lost and all three plains (i.e. transverse, tangential and radial view) were observed in the same section. Cells from the middle portion of the burl were isodiametric, oval to circular, thick-walled and lignified, in morphology not dissimilar from callus tissue. Tyloses were common in all the cell types viz. fibres, ray cells, tracheids, axial parenchyma cells, and vessel elements. [ABSTRACT FROM AUTHOR]

Morphological traits of the plant vascular system such as xylem vessel diameter have been implicated in many physiological processes including resistance to drought-induced xylem cavitation and vessel occlusion during infection with vascular wilt diseases. In both events, xylem vessels lose function because they become filled with air or tyloses and gels. Xylem cavitation has been well studied, whereas vessel occlusion remains purely descriptive even though it is a critical response to wounding injuries and compartmentalization of vascular pathogens. The timing of vessel occlusion is a key determinant to a successful compartmentalization of pathogens within the plant vascular system and we hypothesized that xylem vessel diameter is the driving variable. Using a dye injection method coupled with automated image analysis, we parameterized a model to investigate how xylem vessel diameter affects the speed of vessel occlusion in Vitis vinifera L. cv. Cabernet Sauvignon in response to wounding. Our dataset contains observations from 6,646 vessels at five kinetic points following stem pruning, over a time course of 1 week. Using this approach we provide evidence that the diameter of vessels is a key determinant of the timing of their occlusion. We discuss how these findings impact resistance to vascular wilt diseases in perennial woody hosts. [ABSTRACT FROM AUTHOR]

Fibre direction cylindrical specimens from the sapwood and heartwood areas of Paulownia wood were heat treated at 180, 190, and 200°C split in eight groups of ten specimens each. Air and water permeability were measured, thereafter. Results demonstrated that heat treatment had a positive effect on air permeability both in sapwood and heartwood specimens. That increase might be attributed to the development of cell wall micro-checks caused by thermal degradation and fracture of the vessel tyloses. Liquid permeability was significantly decreased as a result of heat treatment. [ABSTRACT FROM AUTHOR]

Abstract Information on whether tyloses in fossil angiospermic plants form specifically in response to infestation with pathogenic fungi has been lacking so far, and thus the evolutionary history of tylosis formation as a physical restraint strategy against the advancing fungi remains unresolved. Our study addresses this knowledge lacuna. Carbonized woods were recovered from the upper part of the Siwalik succession (Kimin Formation: late Pliocene to early Pleistocene) of Arunachal Pradesh, eastern Himalaya. Samples from different portions of the wood remains were prepared by using standard thin sectioning techniques and studied under transmitted light compound and scanning electron microscopes. The Plio-Pleistocene wood remains are attributed to Gmelina arborea Roxb. (Lamiaceae) as Gmelina siwalika Khan, Bera M et Bera S, sp. nov. Numerous well-preserved tyloses were found mainly in the central heartwood region of the fossil wood. Rare fungal remains indicative of early-stage colonization are characterized by septate fungal hyphae extending through the vascular ray system within the secondary xylem, and fungal spores. As tyloses are present in large numbers and formed before the spread of fungal remains, they served as an effective physical restraint to the spread of the fungi. We conclude that tylosis formation contributed to an antagonistic relationship between pathogenic fungi and Gmelina plant in Neogene paleoecosystems of the eastern Himalaya. This report also demonstrates that the development of this histological protrusion has been a significant process in woody plants since Cenozoic. Highlights • Occurence of numerous well-preserved tyloses in the Neogene angiospermic wood. • Rare fungal remains indicative of initial stage colonization within the xylem. • Tylosis served as an effective physical restraint to the spread of the fungi • Development of tylosis has been a significant process since Cenozoic. [ABSTRACT FROM AUTHOR]

Summary: Xylella fastidiosa is a Gram‐negative bacterial plant pathogen with an extremely wide host range. This species has recently been resolved into subspecies that correlate with host specificity. This review focuses on the status of X. fastidiosa pathogenic associations in plant hosts in which the bacterium is either endemic or has been recently introduced. Plant diseases associated with X. fastidiosa have been documented for over a century, and much about what is known in the context of host–pathogen interactions is based on these hosts, such as grape and citrus, in which this pathogen has been well described. Recent attention has focused on newly emerging X. fastidiosa diseases, such as in olives. Taxonomy: Bacteria; Gammaproteobacteria; family Xanthomonadaceae; genus Xylella; species fastidiosa. Microbiological properties: Gram‐negative rod (0.25–0.35 × 0.9–3.5 μm), non‐flagellate, motile via Type IV pili‐mediated twitching, fastidious. Host range: Xylella fastidiosa has a broad host range that includes ornamental, ecological and agricultural plants belonging to over 300 different species in 63 different families. To date, X. fastidiosa has been found to be pathogenic in over 100 plant species. In addition, it can establish non‐symptomatic associations with many plants as a commensal endophyte. Here, we list the four distinct subspecies of X. fastidiosa and some of the agriculturally relevant diseases caused by them: X. fastidiosa ssp. fastidiosa causes Pierce's disease (PD) of grapevine (Vitis vinifera); X. fastidiosa ssp. multiplex causes almond leaf scorch (ALS) and diseases on other nut and shade tree crops; X. fastidiosa ssp. pauca causes citrus variegated chlorosis (CVC) (Citrus spp.), coffee leaf scorch and olive quick decline syndrome (OQDS) (Olea europaea); X. fastidiosa ssp. sandyi causes oleander leaf scorch (OLS) (Nerium oleander). Significant host specificity seemingly exists for some of the subspecies, although this could be a result of technical biases based on the limited number of plants tested, whereas some subspecies are not as stringent in their host range and can infect several plant hosts. Disease symptoms: Most X. fastidiosa‐related diseases appear as marginal leaf necrosis and scorching of the leaves. In the case of PD, X. fastidiosa can also cause desiccation of berries (termed ‘raisining’), irregular periderm development and abnormal abscission of petioles. In olive trees affected with OQDS, leaves exhibit marginal necrosis and defoliation, and overall tree decline occurs. Plants with ALS and OLS also exhibit the characteristic leaf scorch symptoms. Not all X. fastidiosa‐related diseases exhibit the typical leaf scorch symptoms. These include CVC and Phony Peach disease, amongst others. In the case of CVC, symptoms include foliar wilt and interveinal chlorosis on the upper surfaces of the leaves (similar to zinc deficiency), which correspond to necrotic, gum‐like regions on the undersides of the leaves. Additional symptoms of CVC include defoliation, dieback and hardening of fruits. Plants infected with Phony Peach disease exhibit a denser, more compact canopy (as a result of shortened internodes, darker green leaves and delayed leaf senescence), premature bloom and reduced fruit size. Some occlusions occur in the xylem vessels, but there are no foliar wilting, chlorosis or necrosis symptoms . Useful websites: http://www.piercesdisease.org/; https://pubmlst.org/xfastidiosa/; http://www.xylella.lncc.br/; https://nature.berkeley.edu/xylella/; https://ec.europa.eu/food/plant/plant_health_biosecurity/legislation/emergency_measures/xylella-fastidiosa_en [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Xylem vessels transition through different stages during their functional lifespan, including expansion and development of vessel elements, transition to vessel hydraulic functionality, and eventual transition to post-functionality. We used information on vessel development and function to develop a model of vessel lifespan for woody plants. METHODS: We examined vessel functional lifespan using repeated anatomical sampling throughout the growing season, combined with active-xylem staining to evaluate vessel hydraulic transport functionality. These data were combined with a literature review. The transitions between vessel functional lifespans for several species are illustrated, including grapevine (Vitis vinifera L., Vitaceae), English oak (Quercus robur L., Fagaceae), American chestnut [Castanea dentata (Marshall) Borkh.; Fagaceae], and several arid and semi-arid shrub species. KEY RESULTS: In intact woody plants, development and maturation of vessel elements may be gradual. Once hydraulically functional, vessel elements connect to form a vessel network that is responsible for bulk hydraulic flow through the xylem. Vessels become nonfunctional due to the formation of gas emboli. In some species and under some conditions, vessel functionality of embolized conduits may be restored through refilling. Blockages, such as tyloses, gels, or gums, indicate permanent losses in hydraulic functional capacity; however, there may be some interesting exceptions to permanent loss of functionality for gel-based blockages. CONCLUSIONS: The gradual development and maturation of vessel elements in woody plants, variation in the onset of functionality between different populations of vessels throughout the growing season and differences in the timing of vessel transitions to post-functionality are important aspects of plant hydraulic function. [ABSTRACT FROM AUTHOR]

The impact of climate on xylem structure and function has been profusely studied for a variety of species in the last decades, but the ecological role of ring porosity under increasing levels of environmental stress has been scarcely assessed. In this study, we analyse the timing of earlywood vessels occlusions by tyloses in two ring-porous species with contrasting ecological strategies ( Quercus robur and Q. pyrenaica ) along a seasonal drought gradient, and relate it to variations in earlywood vessel diameter and radial growth obtained from tree-ring series. The number of trees showing tyloses increased in summer as a result of more frequent cavitation events under drier conditions, and was more reduced for the more drought-tolerant Q. pyrenaica , which had a higher hydraulic diameter ( D h ) but lower latewood increments. D h values decreased towards the wettest sites, and were negatively related to warm and rainy conditions in winter. Our results showed that large earlywood vessel diameters are not necessarily accompanied by high rates of tyloses formation or limited growth in summer. We hypothesize that trees in seasonal environments can take advantage from large earlywood vessels, because benefits from a more efficient hydraulic system during favourable periods are higher than the risk of xylem impairment in summer. [ABSTRACT FROM AUTHOR]

Among the main parameters contributing to the characterization of firewood exploitation modes, the age of the collected wood is very difficult to assess in anthracology. In this paper, we propose an original way to investigate the age of the exploited wood, the heartwood formation process which takes place in 20–25-year-old deciduous oak trees. The formation of tyloses in earlywood vessels is an important feature of the changeover of sapwood to heartwood. However, tylosis formation also occurs in sapwood. Therefore, the observation of the mere presence of tyloses in vessels, as routinely performed in anthracology, is not sufficient to distinguish sapwood from heartwood. The aim of this study was thus to use the proportion of vessels sealed by tyloses as a discriminating marker between sapwood and heartwood applicable to anthracology in order to characterize firewood exploitation in the past. The trunks and branches of ten deciduous oak trees ranging from 15 to 60 years old were sampled in three French sites. For an application to archaeological charcoal (tyloses are preserved until 800 °C), thresholds of less than 65% for sapwood and up to 85% for heartwood appear to be significant at the population level for deciduous oak ( Quercus petraea/robur ) in a temperate climate. Besides the indication of the minimal age ( ca. 25 years old in the case of deciduous oak), the variability of the proportion of vessels with tyloses in sapwood is explored as a good indicator of the vitality of the wood which opens new prospects for the exploitation of dendro-anthracological parameters, such as the discrimination of branch wood. [ABSTRACT FROM AUTHOR]

This paper presents the results of dendroanthracological analyses conducted on the anthracological assemblage retrieved from Neolithic and Chalcolithic occupations excavated at Çatalhöyük (central Anatolia, Turkey). Besides standard botanical identification of the charcoal macroremains, a range of anatomical features were also recorded including the presence of fungal decay, traumatic growth, tyloses and discontinuous growth rings. The qualitative assessment of growth ring curvature (following Marguerie and Hunot, 2007) was supplemented by quantitative estimations of minimum wood diameter (following Paradis et al., 2013) alongside sequential ring width measurements. Botanical identifications, dendroanthracological features and quantitative measurements obtained from individual charcoal fragments, were analysed using multivariate statistical techniques. These permitted assessing the relative importance of wood size, type and species in prehistoric fuel selection, and obtaining a detailed view of environmental and management impacts on prehistoric woodland growth conditions. The results of this work indicate the deep antiquity of woodland management practices in the semi-arid continental regions of Southwest Asia dating as early as the Neolithic period. [ABSTRACT FROM AUTHOR]

During vase life of cut flowers obstructions in stem xylem vessels develop. Such obstructions may restrict water uptake in stems and its transport towards flowers, thus lowering their ornamental value and longevity. Clematis is a very attractive plant which can be used as a cut flower in floral compositions. However, nothing is known about the histochemical or cytolo- gical nature of xylem blockages occurring in cut stems of this plant. Observations carried out on Clematis cv. 'Solidarność' proved that tyloses appeared as a principal source of xylem blockage in cut stems. The preservative composed of 200 mg × dm-3 8-HQC (8-hydroxyquinolin citrate) and 2% sucrose arre-sted development of xylem blockage, while the vessels in stems kept in water were filled with tyloses or an amorphic substance. PAS reaction proved that polysaccharides were present in the xylem occlusions, whereas no homogalacturonans were immunolocalized in tyloses using JIM 5 and JIM 7 antibodies. The present study provides new information on the origin of xylem occlusions in clematis and their development in two different vase solutions. Such information can be useful to develop pro- per postharvest treatments aiming to improve keeping qualities of this new cut flower.

Wood retains most of its anatomical characteristics when charred, but charring temperature determines the appearance of the resulting charcoal and this depends largely on the proportions and distribution of the constituent vessels, fibres and parenchyma, as well as moisture content. This study describes the structural changes in the charcoal of the wood of Croton sonderianus Muell. Arg. at two temperatures, 400 °C or 600 °C. This species is an important source of charcoal in the caatinga of the northeast part of Brazil. The samples were heated for ten minutes to reach treatment temperature, charred for two hours at either 400 °C or 600 °C and then left to cool to ambient temperature for 30 to 60 minutes. Our observations showed that most of the changes occurred when charcoal was produced at 600 °C, but the qualitative features necessary for identification were retained. At this temperature, cells lost their circular shape, became angular and occasionally amorphous, the middle lamella disappeared and the walls of adjacent cells coalesced, cell walls became thinner, and the prismatic crystals developed cracks and became porous. Our findings are compared with those for two previously studied Mimosa species which have an entirely different anatomy. [ABSTRACT FROM AUTHOR]

Background Different methods for bowel distension prior to magnetic resonance imaging (MRI) examinations were described in recent years. Purpose To compare orally administered psyllium or locust bean gum / mannitol (LBM) with tylose administered through a duodenal catheter for bowel distension in patients undergoing MRI examination of the small bowel. Material and Methods Three different methods of bowel distension prior to MRI were compared: tylose applied through a duodenal catheter and orally administered psyllium and LBM in three groups with 15 patients each. Datasets were blinded and reviewed independently by two experienced radiologists, who assessed the diagnostic value and the maximum luminal diameter. Results Tylose was superior to psyllium and LBM in the examination of the duodenum and proximal jejunum. LBM was superior to the other methods for distension of the ileum and terminal ileum. The greatest luminal diameter of the duodenum was achieved after tylose and distension of the terminal ileum was the best in patients receiving LBM. The psyllium group was inferior to the other two groups in all segments. Conclusion By using LBM as an oral method of bowel distension, many patients can avoid the unpleasant placement of a duodenal catheter without compromising the diagnostic value of the examination. [ABSTRACT FROM AUTHOR]

The transport and distribution of water in the plant body are essential for plant growth and development. Although the negative effects of long-term drought on xylem water transport are generally known, our knowledge of the impacts of short-term periodical changes in water availability on xylem structure and function remains limited. The aim of this study was to investigate the effects of limited water availability imposed as repeated periods of drought and rehydration on xylem structure and function in stems of a commercially important climber ( Humulus lupulus L.). To evaluate drought-induced changes in xylem characteristics, hydraulic measurements, silicone injection, and anatomical observations were performed in basal and apical regions of hop stems. We found that the total measured hydraulic conductivity ( K h ) was about 8.5 times lower in the basal regions of drought-treated plants compared to well-watered control plants, especially due to vessel clogging with tyloses. In contrast, K h of the apical parts of drought-treated plants was higher than in control plants as a result of the enhanced production of secondary xylem. We also observed differences in K h response to sap ionic composition, with the highest ionic effect in the apical segments of control plants. Greater variation of inner vessel diameter, which increased the transport lumen resistivity of individual vessels by 7%, was another important consequence of irregular watering. The results of our study indicate that periodical fluctuations in water availability induce a significant reduction in total stem transport efficiency and increased risk of vessel dysfunction and illustrate the negative effects of limited water availability for water transport in hop plant stems. [ABSTRACT FROM AUTHOR]

Grapevine trunk diseases ( GTD), caused by a wide range of different fungi, are responsible for decline and productivity losses in vines at all growth stages. Grapevine responses to fungal attack include morphological and physiochemical defence mechanisms in the vascular system to reduce fungal infections. However, the extent to which these responses could control further spread by GTD-fungi in the xylem vessels is poorly known. This study shows the formation of tyloses inside xylem vessels of diseased grapevines, as well as extracellular ligninolytic activities [lignin peroxidase, manganese peroxidase (MnP) and/or laccase] exhibited by some GTD-fungi isolated here from symptomatic grapevines. In particular, Botryosphaeriaceae spp. and Phaeoacremonium minimum showed all three lignin-degrading enzymatic activities. We also examined whether selected vine phenolic compounds, often located in the vascular system in response to fungal infection, could affect the lignin-degrading activity from those GTD-fungi as well as fungal colonisation. We found that phenolic compounds appeared to inhibit MnP activity, in addition to reducing fungal growth by causing anomalies in the hyphae morphology. Our results support that affected grapevines can initiate the tylosis formation in order to constrain fungi in the xylem vessels, while highlight the complementary action of the phenolic compounds to inhibit the fungi growth and colonisation. Phenolic compounds are therefore likely to have important role in alternative strategies for preventing trunk diseases. [ABSTRACT FROM AUTHOR]

The dielectric properties of tylose water pastes during microwave thawing and heating were measured over 300–3000 MHz and −30 to +60 °C, and the feasibility of their use as a frozen model food instead of frozen lean tuna was evaluated. The effects of salt (NaCl) content (0.5–2.0%, wb) on the dielectric properties were investigated. Although salt is a good additive for increasing the dielectric loss factor, higher salt addition increased the thawing time and non-uniformity through decreased penetration depth. A similar response to increasing temperature between frozen lean tuna and tylose paste was observed during MW thawing and heating at 2450 MHz, due to similarities in penetration depth. This was possible by an appropriate adjustment of the dielectric properties of tylose by salt addition (0.5% NaCl). This study confirmed the potential of frozen tylose paste as a model food in evaluating performance of microwave thawing of real foods. [ABSTRACT FROM AUTHOR]

Vessel occlusion through tyloses or gums is a natural phenomenon occurring with aging and heartwood formation, and in sapwood in response to vessel embolism. These types of vessel occlusion play a crucial role to limit the spread of pathogens and wood decay organisms, also as part of compartmentalization after wounding. In the sapwood, they can be considered to be an effective stress response. Here we review the literature on tyloses and gums in hardwoods, starting with the detailed 19th century account on tyloses by Hermine von Reichenbach. The structural diversity of tyloses (from thin-walled to sclerotic) and gum deposits is highlighted and illustrated. Our understanding of the development of vessel occlusions through vessel contact cells of the ray and axial parenchyma has greatly increased over the last decades, also thanks to ultrastructural and immunocytological studies. We critically discuss the postulated relationships between vessel-to-ray parenchyma pit size and vessel size and the incidence of either tyloses or gums and review the occurrence of these types of vessel occlusions in extant and fossil dicots. All factors identified in the literature as stimuli for vessel occlusion probably act through vessel embolism as a single direct trigger. Attempts in the literature to relate vessel occlusion with mechanisms of vessel refilling and embolism repair are controversial and invite more experimental research. [ABSTRACT FROM AUTHOR]

Ceratocystis manginecans is a destructive systemic fungus and a major cause of mango sudden decline. Heavy losses to the mango industry in Pakistan are due to this disease. This study was designed to evaluate the histological changes in mango seedlings inoculated with C. manginecans. The pathogenic fungus was inoculated to indigenous mango germplasm of Punjab, Azad Jammu and Kashmir. After one week of inoculation, plants started showing disease symptoms including gum exudation, wilting of leaves, discoloration of stem, and bark splitting. Discolored bark from diseased plants was peeled off and internal symptoms were studied and confirmed for C. manginecans infection. Diseased stems were transversely sliced and fixed in formaline acetic alcohol (FAA), double stained and examined under compound microscope. The epidermal tissues were found to be collapsed due to sclertization of xylem vessels, fungal hyphal growth, production of phenolics and tyloses. Deposition of phenolics and formation of tyloses in turns leads to the obstruction of water and minerals uptake, therefore, plants start wilting and then decline. [ABSTRACT FROM AUTHOR]

Background and Aims Tyloses and embolisms have been reported to impair water transport during the development of Pierce's disease ( PD), caused by the xylem-dwelling pathogen X ylella fastidiosa. This work investigates the relative importance of these xylem conduit obstructions in stems of inoculated V itis vinifera plants. Methods and Results After 18 weeks in a greenhouse, internodes from control and needle-inoculated Chardonnay vines were assessed for embolisms using non-destructive magnetic resonance imaging ( MRI). Tyloses were identified by subsequent destructive histology and light microscopy examination. Embolism of individual or small sectors of vessels was detected by MRI analysis of a control shoot, usually in the proximity of the pith; virtually no tyloses were observed in the corresponding histological sections. From a symptomatic (inoculated) shoot, MRIs revealed large areas of embolised vessels extending radially towards the epidermis in most of the internodes; several individual or groups of two to three vessels appeared to be occluded with tyloses. Conclusions In all assessed internodes, MRI-detected embolisms were found more frequently than tyloses, suggesting that over the course of PD embolism formation precedes tylose development. Significance of the Study Embolisms appear to be the first and predominant type of occlusion in stems during early PD progression; nevertheless, their importance for explaining water transport impairment has been overlooked in most studies. [ABSTRACT FROM AUTHOR]

Short vase life of cut lilac stems limits its commercial potential. Rapid wilting of cut lilac inflorescences is probably caused by blockage of water transport in stems. The purpose of this study was to recognize the nature of the occlusions blocking xylem vessels in cut stems of common lilac and to identify a relationship, if any, between the type of a holding solution, xylem blockages and vase life of lilacs flowering under different environmental conditions. The stems of the white flowering cultivar “Mme Florent Stepman” were harvested in Nov/Dec from shrubs forced from the beginning of November by a standard procedure involving treatment with 37 °C, in January from shrubs forced from the beginning of November under 15 °C, and in May from control shrubs, i.e., flowering naturally in the field. Cut stems were placed in distilled water, 8-HQC, a standard preservative composed of 8-HQC + 2% sucrose, nanosilver and nanosilver + 2% sucrose. Tyloses were observed in stem xylem vessels while practically no microorganisms were detectable. The incidence of blockage formation in the stems depended on the flowering date and the biocide used. The longest vase life was observed in January with 8-HQC or 8-HQC + S, but in all flowering periods the least xylem blockages were formed when NS was used as the biocide. Therefore, formation of tyloses does not appear to be directly related to the postharvest life of lilac and its vase life can be extended by standard florists’ preservatives irrespective of their effect of the xylem physical obstructions. [ABSTRACT FROM AUTHOR]

The circumscription of Bignoniaceae genera and tribes has undergone major changes following an increased understanding of phylogenetic relationships within the family. While DNA sequence data have repeatedly reconstructed major clades within the family, some of the clades recovered still lack diagnostic morpho-anatomical features, complicating their recognition. In this study we investigated the wood anatomy of all major lineages of Bignoniaceae (except Tourrettieae) in search for anatomical synapomorphies for clades. We sampled 158 species of Bignoniaceae, representing 67 out of the 82 genera currently recognized. Detailed descriptions of quantitative and qualitative wood anatomical features are presented for each clade and interpreted in the light of a molecular phylogeny for the family. Jacarandae are characterized by a paratracheal winged-aliform parenchyma, with the traditional subdivision of Jacaranda into sections Monolobos and Dilobos supported by the uniseriate and homocellular rays of Monolobos versus the wide and heterocellular rays of Dilobos. Tecomeae s.s. are characterized by scanty paratracheal parenchyma, septate fibers, and heterocellular rays, traits also found in Delostoma, a genus previously included in Tecomeae s.l., but recently shown to represent a separate lineage. Crescentiina includes two sub-clades, the Tabebuia alliance and the Paleotropical clade, which share abundant aliform parenchyma, short and mainly homocellular rays, less commonly with heterocellular rays with body procumbent and one row of marginal square cells. Members of the Tabebuia alliance and the Paleotropical clade can be distinguished from each other by the narrow vessels with a widespread storied structure found in members of the Tabebuia alliance, versus the vessels with medium to wide width and a non-storied structure found in members of the Paleotropical clade. Oroxyleae are characterized by a combination of simple and foraminate perforation plates and homocellular rays, while Catalpeae are characterized by scanty paratracheal parenchyma, abundant tyloses and vessel-ray pits simple to semi-bordered. Bignonieae differ from all other clades by a variant secondary growth and a typically lianoid wood anatomy. Overall, wood anatomical characters are not very labile within the family, being distributed across clades in a very predictive manner. Several anatomical characters represent good anatomical synapomorphies and provide further support to clades identified in molecular phylogenetic studies. [ABSTRACT FROM AUTHOR]

The name jarrah dieback has been used for two different disorders, leading to considerable confusion. It was coined in the 1940s to describe the sudden death of groups of jarrah ( Eucalyptus marginata) trees in south western Western Australia, which occurred on poorly drained sites, following exceptionally heavy rainfall. In the 1960s these sites were shown to be infested by Phytophthora cinnamomi and jarrah deaths were attributed to it, even though it was only isolated from 5 % of sampled trees. Also the definition of jarrah dieback was expanded to include deaths of many other plants on infested sites, from which P. cinnamomi was more readily isolated. Jarrah trees die from severe water deficiency, indicating problems with water conduction through roots. Xylem vessel diameters vary along roots, being narrow at the root collar, while distally they are larger, providing water storage. Jarrah transpires vigorously during summer, accessing water at depth on sites with deep soil, but being more dependent on internally stored water when root systems are shallower. Following waterlogging, sapwood vessels become blocked with tyloses, reducing both conductivity and potential water storage; such trees may have insufficient water reserves for summer survival. In jarrah P. cinnamomi is unlikely to cause water deficiency because sapwood invasion is rapidly contained in healthy roots. Recent investigations into P. cinnamomi invasion and host responses in other plants show that it can potentially cause a vascular wilt in Banksia spp. and chronic, symptomless infections in herbaceous plants. Susceptibility to waterlogging damage, and/or mortality resulting from infection by P. cinnamomi can only be clarified by detailed knowledge of the hosts and their vulnerabilities. This is essential for making diagnoses, devising management strategies, and avoiding the confusions of the past. [ABSTRACT FROM AUTHOR]

Shoot pruning could cause short-term damages to vines. In response to damage, tyloses develop in shoot xylem vessels interfering free water and mineral transportation. In this study, the tylosis development at different nodes of the current-year and perennial shoots of sixty three-year-old grapevines ( Vitis vinifera L.) after pruning was investigated. The results showed that tyloses at the nodes closest to the trunk developed rapidly; and tylosis development initiated at the time when the size of vessel-ray pit was greater than that of parenchyma cell-parenchyma cell pit. In current-year shoots, tyloses were formed in up to 87% of the vessels, and 40% of the vessels were completely blocked by tyloses. In wound-induced perennial shoots, 30% of the vessels were completely blocked by tyloses. When few vessels were blocked by tyloses, new vessels could differentiate, and water transportation system may be restored. However, when tyloses developed in a large number of vessels and the large number of the vessels were blocked, the original capability of water transport was decreased (the largest decrease was 21.1% in this study), resulting in dehiscence or shrinkage cracking in this area. The study proved that the tylosis formation in functional vessels limited the water transport efficiency. [ABSTRACT FROM AUTHOR]

Effects of three drying schedules on fluid flow were studied in the sapwood and heartwood of Paulownia wood (Paulownia fortunei). Boards with a commercial thickness of 5 cm were randomly dried to a final moisture content of 8 ± 2% using a mild (T6E3), a moderate (T6E4), and a severe (T7E4) drying schedule. Permeability measurement was carried out when specimens reached the final moisture content. Results showed a significant difference in the specific gas permeability as well as liquid permeability of the boards dried under the three drying schedules. Furthermore, a significant difference was observed in the gas permeability of sapwood and heartwood, dried under the different schedules, but not much significant difference was seen in the liquid permeability between sapwood and heartwood. T6E3had the highest liquid permeability; furthermore, it was reported to have resulted in the lowest warping and most homogeneous moisture profile. This mild schedule is therefore recommended for commercial drying of Paulownia wood when further preservation and impregnation processes are planned for the dried boards. In the meantime, it is concluded that the age and drying schedule have significant effects on the formation of tyloses, significantly affecting gas and liquid permeability in Paulownia wood. [ABSTRACT FROM AUTHOR]

The psammophilic genus Tylos Audouin, 1826 is represented within the Mediterranean basin as two species: T. ponticus Grebnicki, 1874, and T. europaeus Arcangeli, 1938, according to Taiti and Ferrara (1996). It is impossible to define precisely the current distribution of the two species, mainly because, in literature, both taxa have been described as subspecies of T. latreillii or even, in some cases, as T. latreillii sensu lato. The current study surveyed populations of Tylos spp. on sandy beaches along the coastline of Sicily, circum-Sicilian islands and the Maltese archipelago. The aims of this study are to fully and correctly identify all the sampled populations, pursuant to characterizing the current distribution of the two species, which occupy similar ecological niches, and to investigate any possible granulometric preferences by the two species. Data acquisition proceeded along three tiers: in situ sampling, manually and through the deployment of pitfall trap constellations, literature review and by analyzing preserved specimens of Tylos held within the 'Caruso' collection (University of Catania, Catania, Italy). Generally, T. europaeus showed a preference for fine sand, whilst T. ponticus showed a preference for fine-medium sand, although, statistically, differences in the distribution of the two species could not be explained in terms of median grain size. The two species were never recorded on the same beach. The degree of inter-specific morphological differentiation was also evaluated through a detailed morphological study of sampled Tylos spp. [ABSTRACT FROM AUTHOR]

Highlights: [•] We removed root apices of two rice cultivars with differential aluminum tolerance. [•] Tracheal elements without tylose permitted free aluminum movement into cell leaves. [•] Differential aluminum accumulations were observed in these leaves. [•] Toxic effect types were observed equally in mesophyll, chloroplasts and mitochondria. [ABSTRACT FROM AUTHOR]

Hundreds of cankers caused by Ceratocystis smalleyi are associated with hickory bark beetle-attacked bitternut hickory exhibiting rapid crown decline in the north-central and northeastern United States. Discolored sapwood colonized by the fungus commonly underlies the cankers. Field studies were conducted to test the hypothesis that C. smalleyi infections cause vascular system dysfunction in infected trees. Fifty C. smalleyi inoculations made at 1.8 to 3.8 m in height on stems of healthy bitternut hickory trees (13 to 28 cm in diameter at 1.4 m in height) resulted in extensive canker formation and sapwood discoloration 12 to 14 months after treatment compared with water-inoculated and noninoculated controls. Sap flow velocity (midday) was significantly lower in the infected trees compared with that in the controls. Sap flow velocity also was inversely correlated with the proportion of bark area with cankered tissues and with tylose abundance in the youngest two growth rings. Tylose formation in current-year vessels associated with C. smalleyi infections is likely responsible for much of the water transport disruption. It is hypothesized that multiple stem infections of C. smalleyi and the resulting xylem dysfunction contribute to crown wilt development in bitternut hickory exhibiting rapid crown decline. [ABSTRACT FROM AUTHOR]

Background and Aims Our knowledge of tylosis formation is mainly based on observations of extant plants; however, its developmental and functional significance are less well understood in fossil plants. This study, for the first time, describes a complete tylosis formation in a fossil woody conifer and discusses its ecophysiological implications. Methods The permineralized stem of Shenoxylon mirabile was collected from the upper Permian (Changhsingian) Sunjiagou Formation of Shitanjing coalfield, northern China. Samples from different portions of the stem were prepared by using the standard thin-sectioning technique and studied in transmitted light. Key Results The outgrowth of ray parenchyma cells protruded into adjacent tracheids through pits initially forming small pyriform or balloon-shaped structures, which became globular or slightly elongated when they reached their maximum size. The tracheid luminae were gradually occluded by densely spaced tyloses. The host tracheids are arranged in distinct concentric zones representing different growth phases of tylosis formation within a single growth ring. Conclusions The extensive development of tyloses from the innermost heartwood (metaxylem) tracheids to the outermost sapwood tracheids suggests that the plant was highly vulnerable and reacted strongly to environmental stress. Based on the evidence available, the tyloses were probably not produced in response to wound reaction or pathogenic infection, since evidence of wood traumatic events or fungal invasion are not recognizable. Rather, they may represent an ecophysiological response to the constant environmental stimuli. [ABSTRACT FROM PUBLISHER]