Anatomical features of the inner bark of three clones of urushi trees (Toxicodendron vernicifluum) with different amounts of lacquer production were investigated with light microscopy and ...cryo-scanning electron microscopy. All of trees showed a similar structure of inner bark. They formed longitudinal resin canals and traumatic resin canals close the cambium in the inner bark. Cryo-scanning electron microscopic images showed that all of longitudinal resin canals and traumatic resin canals were filled with resin. Trees of clone with higher amounts of lacquer production formed wider inner bark, higher number of resin canals and larger cross-sectional area of resin canals than those with lower amounts of lacquer production. In addition, trees of clone with higher amounts of lacquer production formed more traumatic resin canals close to the cambium than those with lower amounts of lacquer production. Our observations suggest that the structure of inner bark, in particular the quantity and size of resin canals, might be suitable anatomical index for the clonal selection of trees that produce higher amounts of lacquer.
Abstract
Resin canal discoloration (RCD) severely impacts the fruit quality of mango, diminishes consumer confidence, and reduces sales, but the biological cause is still unclear. Using ...next-generation sequencing, the overall microbial community composition of RCD+ and visually healthy mango fruits was determined for the first time to examine the possible role of bacterial and fungal pathogens in RCD. The diversity profile of bacterial and fungal communities was determined using primers targeting the 16S rRNA gene and Internal Transcribed Spacer (ITS) regions. Results showed that bacterial communities in healthy fruits are clustered together and significantly different from those in RCD+ fruits. Tatumella and Pantoea species were the most abundant bacterial taxa on RCD+ fruit, and both have been linked to disease outbreaks in a variety of fruit crops. Fungal communities were generally similar between RCD+ and normal samples, though non-pathogenic yeasts Meyerozyma and Naganishia tended to dominate the fungal communities on RCD+ fruit. The study indicates that bacteria rather than fungal organisms are more likely to be associated with RCD in mango. This finding will facilitate the isolation and confirmation of RCD-causing organisms and the development of control strategies to manage RCD problem in mango.
Irreversible xylem dysfunction is triggered by patchy cavitation of tracheids around the resin canals by pine wood nematodes.
Abstract
Physiological mechanisms of irreversible hydraulic dysfunction ...in seedlings infected with pine wilt disease (PWD) are still unclear. We employed cryo-scanning electron microscopy (cryo-SEM) to investigate the temporal and spatial changes in water distribution within the xylem of the main stem of 2-year-old Japanese black pine seedlings infested by pine wood nematodes (PWNs). Our experiment was specifically designed to compare the water relations among seedlings subjected to the following water treatment and PWN combinations: (i) well-watered versus prolonged drought (no PWNs); and (ii) well-watered with PWNs versus water-stressed with PWNs (four treatments in total). Cryo-SEM imaging observations chronicled the development of patchy cavitations in the xylem tracheids of the seedlings influenced by PWD. With the progression of drought, many pit membranes of bordered pits in the xylem of the main stem were aspirated with the decrease in water potential without xylem cavitation, indicating that hydraulic segmentation may exist between tracheids. This is the first study to demonstrate conclusively that explosive and irreversible cavitations occurred around the hydraulically vulnerable resin canals with the progression of PWD. Our findings provide a more comprehensive understanding of stressors on plant-water relations that may eventually better protect trees from PWD and assist with the breeding of trees more tolerant to PWD.
After mechanical wounding, callus tissue and tangential rows of traumatic resin ducts (TRDs) are formed in many conifer species. This reaction can be used to date past events of geomorphic processes ...such as rockfall, debris flow and snow avalanches. However, only few points are known about the tangential spread or the timing of callus tissue and TRD formation after wounding. We analyzed 19 Larix decidua Mill. (European larch) and eight Picea abies (L.) Karst. (Norway spruce) trees that were severely damaged by rockfall activity, resulting in a total of 111 injuries. Callus tissue appeared sparsely on the cross sections and was detected on only 4.2% of the L. decidua samples and 3.6% of the P. abies samples. In contrast, TRDs were present on all cross sections following wounding and were visible on more than one-third (34% in L. decidua and 36.4% in P. abies) of the circumference where the cambium was not destroyed by the rockfall impact. We observe different reactions in the trees depending on the seasonal timing of wounding. The tangential spread of callus tissue and TRDs was more important if the injury occurred during the growth period than during the dormant season, with the difference between seasons being more pronounced for callus tissue formation than for TRD formation. We observed an intra-annual radial migration of TRDs with increasing tangential distance from the wound in 73.2% of the L. decidua samples and 96.6% of the P. abies samples. The persistence of TRD formation in the years following wounding showed that only L. decidua trees produced TRDs 2 years after wounding (10.5%), whereas P. abies trees produced TRDs 5 years after wounding (> 50%).
Main conclusion
Spatial organization and connectivity of wood rays in
Pinus massoniana
was comprehensively viewed and regarded as anatomical adaptions to ensure the properties of rays in xylem.
...Spatial organization and connectivity of wood rays are essential for understanding the wood hierarchical architecture, but the spatial information is ambiguous due to small cell size. Herein, 3D visualization of rays in
Pinus massoniana
was performed using high-resolution μCT. We found brick-shaped rays were 6.5% in volume fractions, nearly twice the area fractions estimated by 2D levels. Uniseriate rays became taller and wider during the transition from earlywood to latewood, which was mainly contributed from the height increment of ray tracheids and widened ray parenchyma cells. Furthermore, both volume and surface area of ray parenchyma cells were larger than ray tracheids, so ray parenchyma took a higher proportion in rays. Moreover, three different types of pits for connectivity were segmented and revealed. Pits in both axial tracheids and ray tracheids were bordered, but the pit volume and pit aperture of earlywood axial tracheids were almost tenfold and over fourfold larger than ray tracheids. Contrarily, cross-field pits between ray parenchyma and axial tracheids were window-like with the principal axis of 31.0 μm, but its pit volume was approximately one-third of axial tracheids. Additionally, spatial organization of rays and axial resin canal was analyzed by a curved surface reformation tool, providing the first evidence of rays close to epithelial cells inward through the resin canal. Epithelial cells had various morphologies and large variations in cell size. Our results give new insights into the organization of radial system of xylem, especially the connectivity of rays with adjacent cells.
SUMMARY
Triterpenes (30‐carbon isoprene compounds) represent a large and highly diverse class of natural products that play various physiological functions in plants. The triterpene biosynthetic ...enzymes, particularly those catalyzing the late‐stage regio‐selective modifications are not well characterized. The bark of select Boswellia trees, e.g., B. serrata exudes specialized oleo‐gum resin in response to wounding, which is enriched with boswellic acids (BAs), a unique class of C3α‐epimeric pentacyclic triterpenes with medicinal properties. The bark possesses a network of resin secretory structures comprised of vertical and horizontal resin canals, and amount of BAs in bark increases considerably in response to wounding. To investigate BA biosynthetic enzymes, we conducted tissue‐specific transcriptome profiling and identified a wound‐responsive BAHD acetyltransferase (BsAT1) of B. serrata catalyzing the late‐stage C3α‐O‐acetylation reactions in the BA biosynthetic pathway. BsAT1 catalyzed C3α‐O‐acetylation of αBA, βBA, and 11‐keto‐βBA in vitro and in planta assays to produce all the major C3α‐O‐acetyl‐BAs (3‐acetyl‐αBA, 3‐acetyl‐βBA, and 3‐acetyl‐11‐keto‐βBA) found in B. serrata bark and oleo‐gum resin. BsAT1 showed strict specificity for BA scaffold, whereas it did not acetylate the more common C3β‐epimeric pentacyclic triterpenes. The analysis of steady‐state kinetics using various BAs revealed distinct substrate affinity and catalytic efficiency. BsAT1 transcript expression coincides with increased levels of C3α‐O‐acetyl‐BAs in bark in response to wounding, suggesting a role of BsAT1 in wound‐induced biosynthesis of C3α‐O‐acetyl‐BAs. Overall, the results provide new insights into the biosynthesis of principal chemical constituents of Boswellia oleo‐gum resin.
Significance Statement
Boswellia trees produce specialized oleo‐gum resin in response to wounding, which is enriched with a unique class of C3α‐epimeric pentacyclic triterpenes, known as boswellic acids that have received considerable attention as medicinal compounds, but the biosynthetic enzymes of boswellic acids are still largely unknown. Here, we report the identification and functional characterization of a wound‐responsive BAHD acetyltransferase which catalyzes regio‐selective acetylation of boswellic acids in the formation of principal chemical constituents of Boswellia oleo‐gum resin.
•The role of climate and soil water availability on resin yield was evaluated.•Resin yield increased with temperature, radiation and evapotranspiration values.•Resin yield and axial canal size were ...correlated with water deficit in spring.•Above a certain threshold of cumulated water deficit, summer rainfall favored resin yield.•Stand density and soil quality affected the relations between climate and resin yield.
In the last five years, sharp increases in the price of natural resins, accompanied by technological advances directed toward mechanization, have made resin tapping a strategic activity for rural development and forest conservation. The resin industry demands more efficient tapping methods and forest management plans as a way to increase competitiveness in a global market. Understanding the effects of environmental conditions on resin yield, especially under the current scenario of climate change, is key to improving techniques and plans in the resin industry. This study aims to evaluate the intra- and inter-annual effects of climate conditions and soil water availability on resin yield in tapped Pinus pinaster stands. The individual resin yield of 26 tapped trees growing at two locations with different stand densities and soil characteristics was measured fortnightly during the tapping season (June to October) for four years. The study was complemented with an analysis of changes in xylem anatomy over the four years, with a focus on axial resin canal traits, including 12 non-tapped trees as controls. Intra-annual variation in resin yield was strongly correlated with temperature, solar radiation, potential evapotranspiration and water deficit. Inter-annual variation in resin yield and resin canal abundance were correlated with temperature and water deficit in spring, but above a certain threshold of cumulated water deficit in summer rainfall favored resin yield. Under adverse climate scenarios where resource optimization is desirable, a reduced tapping season during the warmest months (June–September) would be advisable, assuming a very small production loss. Similarly, in years with a rainy summer and/or dry spring, a slightly longer tapping season could be suggested, as resin yield increases after these events.
Variations in the structure of plant leaves are mainly due to environmental variability. In many cases the way to acclimatize to unfavorable conditions. It is documented that in Cuba the anatomical ...and morphological characteristics of P. caribaea needles differ between ecotopes with different edaphoclimatic conditions. In this study, the effect of the position in the tree crown on the anatomy of the needles is analyzed. For this purpose, needles were collected from the lower, middle and upper part of 30 trees. The variables analyzed were thickness of the chlorophyll parenchyma, thickness of the transfusion parenchyma, height of the conduction tissue and width of the conduction tissue, cuticle thickness, epidermis thickness, hypodermis thickness, number of layers of hypodermis cells, number of channels and number of stomat. The results of the analyzes show a greater differentiation of the morphology of the needles towards the upper part of the tree, which is expressed by the increase in the thickness of the protective tissues and related to the greater exposure to the sun and lower relative humidity than they are exposed. The variables that contribute the most to differentiate the needles according to their position in the tree are the number of stomata and the number of cells in the hypodermis.
As variações na estrutura das folhas das plantas são devidas principalmente à variabilidade ambiental. Em muitos casos, é o caminho para a aclimatação a condições desfavoráveis. Está documentado que em Cuba as características anatômicas e morfológicas das agulhas de P. caribaea diferem entre ecótones com diferentes condições de solo e clima. Neste estudo, é analisado o efeito da posição do dossel sobre a anatomia das agulhas. Para este fim, as agulhas foram coletadas da parte inferior, média e superior de 30 árvores. As variáveis analisadas foram espessura do parênquima clorofila, espessura do parênquima transfusional, altura e largura do tecido de condução, espessura da cutícula, espessura da epiderme, espessura da hipoderme, número de camadas celulares da hipoderme, número de canais e número de estomas. Os resultados das análises mostram uma maior diferenciação na morfologia das agulhas em direção ao topo da árvore, que é expressa por um aumento na espessura dos tecidos protetores e está relacionada à maior exposição ao sol e à menor umidade relativa a que estão expostos. As variáveis que mais contribuem para diferenciar as agulhas de acordo com sua posição na árvore são o número de estômatos e o número de células na hipoderme.
Las variaciones de la estructura de las hojas de las plantas se deben fundamentalmente a la variabilidad ambiental. En muchos casos la vía para la aclimatación a condiciones desfavorables. Está documentado que en Cuba las características anatómicas y morfológicas de las acículas de P. caribaea difieren entre ecótopos con distintas condiciones edafoclimáticas. En este estudio, se analiza el efecto que tiene la posición en la copa del árbol en la anatomía de las acículas. Para esto se colectaron acículas de la parte inferior, media y alta a 30 árboles. Las variables analizadas fueron grosor del parénquima clorofílico, grosor del parénquima de transfusión, altura del tejido de conducción y ancho del tejido de conducción, grosor de la cutícula, grosor de epidermis, grosor de hipodermis, número de capas de células de la hipodermis, número de canales y número de estomas. Los resultados de los análisis muestran una mayor diferenciación de la morfología de las acículas hacia la parte superior del árbol, que se expresa por el aumento del grosor de los tejidos de protección y relacionado con la mayor exposición al sol y menor humedad relativa a la que están expuestas. Las variables que más contribuyen a diferenciar las acículas según la posición en el árbol son el número de estomas y el número de células de la hipodermis.
Introduction
Tree defense characteristics play a crucial role in modulating conifer bark beetle interactions, and there is a growing body of literature investigating factors mediating tree growth and ...resin-based defenses in conifers. A subset of studies have looked at relationships between tree growth, resin duct morphology and climate; however, these studies are almost exclusively from lower-elevation, moisture-limited systems. The relationship between resin ducts and climate in higher-elevation, energy-limited ecosystems is currently poorly understood.
Methods
In this study, we: (1) evaluated the relationship between biological trends in tree growth, resin duct anatomy, and climatic variability and (2) determined if tree growth and resin duct morphology of whitebark pine, a high-elevation conifer of management concern, is constrained by climate and/or regional drought conditions.
Results
We found that high-elevation whitebark pine trees growing in an energy-limited system experienced increased growth and defense under warmer and regionally drier conditions, with climate variables explaining a substantive proportion of variation (∼20–31%) in tree diameter growth and resin duct anatomy.
Discussion
Our results suggest that whitebark pine growth and defense was historically limited by short growing seasons in high-elevation environments; however, this relationship may change in the future with prolonged warming conditions.
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