Bark Formation Research Articles

ModelBark: a toy model to study bark formation in woody species

Abstract The study of growth of woody species is a challenging issue, primarily due to the complexity of the involved processes, which span broad spatial and temporal scales. Very often, this latter aspect almost precludes complete experimentation, thereby hindering the comparison between theoretical predictions and real-world observations. Computer simulations offer an alternative approach, allowing for data collection based on theoretical assumptions, and has been applied to the analysis of different features in plant development, as the production of secondary vascular tissues, xylem and phloem, in woody plants. However, the simulation of bark development faces added difficulties, due to the scarcity of experimental observations to base the model on. In this paper, we introduce a computer model designed to simulate bark formation based on mechanical stimuli acting on the various types of cells comprising this tissue. Our model can be conceptualized as a cellular automaton of variable size with non-local updating rules. By adjusting the parameters defining the model, we investigate the most influential factors in bark development, obtaining the most common bark types observed in trees. Furthermore, we provide an intuitive interface, making it suitable for educational purposes as well.

Genome-wide analysis of the bZIP gene family in Cinnamomum camphora ('Gantong 1') reveals the putative function in anthocyanin biosynthesis

Basic leucine zipper (bZIP) transcription factors (TFs) regulate plant development, growth, and secondary metabolism. The formation of red bark of new ornamental cultivar 'Gantong 1' is regulated mainly by anthocyanin anabolism. However, it is unclear whether and which bZIP TFs are involved in this process. We identified 89 genes encoding CcbZIP TFs in Cinnamomum camphora genome that could be divided into 14 subfamilies with similar gene structures and conserved motifs. CcbZIP38 and CcbZIP57 were highly conserved compared to HY5 in Arabidopsis thaliana and they were highly expressed in the bark and leaves of 'Gantong 1' at different stages. The target gene enrichment analysis showed that indicating indirect involvement of CcbZIP38 and CcbZIP57 in the regulation of anthocyanin synthesis. Our study contributes to understanding the molecular mechanism of anthocyanin synthesis regulation by CcbZIP TFs and provides a theoretical basis for genetic improvement of ornamental traits in C. camphora.

Morpho-anatomy and habitat characteristics of Xanthostemon verdugonianus Náves ex Fern.-Vill. (Myrtaceae), a threatened and endemic species in the Philippines

A study provided insights on morphoanatomy of Xanthostemon verdugonianus, an endemic and vulnerable species in the Philippines. Sampling was conducted in its natural habitat with presence of dominant vegetation and rehabilitated sites of the species. In a purposive manner, quadrats were established to collect samples and describe the morpho-anatomy, associated species, and soil particle characteristics. The leaf is opposite with a distinct reddish color when young in shoot terminal. The leaf cuticle is distinctly thick, hypostomatic with presence of paracytic stomata, and the compact spongy layer could be an adaptation to xeric conditions. The stem and roots contain tissues manifesting secondary growth having secondary xylem and formation of outer bark. Inflorescence is corymb, complete flower is bright red, with prominent cup-shaped hypanthium, persistent lobe-shaped calyx, and inferior ovary. Fruit is globular capsule round-ovoid in shape with a woody texture. Placental seeds are visible upon splitting of matured fruits which are flattened and deltoid to semicircular shape. A total of 31 species under 18 flora families are associated with X. verdugonianus with the mean abundance of 8 species per plot. Ultramafic substrate was dominantly composed of medium sand particles, and the reddish color indicating oxidation of metallic elements in the soil. Analyzing the morpho-anatomical features can help to explain its endemicity, survival in the wild, and adaptation to climate change.

Age-related pattern in bark formation of Betula ermanii growing in volcanic environments from southern Sakhalin and Kuril Islands (Northeast Asia)

Age-related pattern in bark formation of Betula ermanii growing in volcanic environments from southern Sakhalin and Kuril Islands (Northeast Asia)

The Siberian spruce (Picea obovata L.) stem formation in the Yenisei Range

The present research investigated the Siberian spruce stem formation features, basing on materials from 15 sample plots, where we cut and measured 160 model trees. We indicated that the stem form factor is 12-17% less than the average in current volume tables, which entails errors in determining stem and growing stock volumes. We established features of the spruce bark formation at different relative lengths. We did not reveal any influence of bark on the stem shape. We also made some recommendations for the inventory assessment of spruce stands in the study area.

Slag Formation during Entrained Flow Gasification: Calcium-Rich Bark Fuel with KHCO3 Additive

Slag property management is of utmost importance for successful operation of entrained flow gasifiers. The present study investigates the influence of potassium introduced as KHCO3 on the ash and slag formation of softwood bark, a calcium-rich fuel, during entrained flow gasification. The bark contained only minor mineral inclusions causing the ash composition to be dominated by calcium and potassium. Wood bark with and without KHCO3 additive was gasified between 850 and 1400 °C at O2 stoichiometric ratio (λ) 0.6. The ash particles collided with a flat impact probe inside the hot reactor at particle impact angles set to 90°, 60°, and 30°. The reactor and probe allowed long-distance microscope data collection close to the probe surface. Particle deposition was optically monitored and resulting deposits were analyzed by SEM-EDS and XRD. Thermodynamic equilibrium and viscosity calculations were used to assist interpretation of experimental results. The predicted temperature window for liquid carbonate formation was experimentally verified, but the melt fraction of the deposit was too low to cause efficient flow and removal of ash from the probe under the prevailing experimental conditions. At higher temperatures, spherical particles indicated lower ash melting temperatures than expected from the bulk ash composition, and a detailed mechanism was proposed.

Areole Changes During Bark Formation for Columnar Cactus Species

Bark coverage occurs on stems of more than twenty species of columnar cacti. This report documents characteristics of areoles and spines from central Mexico with bark coverage percentages on five columnar cactus species (Cephalocereus columna-trajani, Neobuxbaumia macrocephala, N. mezcalaensis, N. tetetzo, and Pachycereus hollianus). Older cacti (more than 4 m tall) had fewer original spines than younger cacti (less than 2 m tall). For cacti taller than 4 m, loss of the original spines was positively correlated with bark coverage. For three species, loss of the original spines occurred with about 75% for bark coverages. Four of the five species studied produced hair-like spines at areoles. Three of the five species produced emergent spines. Most emergent spines were associated with hair-like spines. The presence of hair-like and emergent spines (spines that emerged on mature cactus surfaces) was not well correlated with percentages of bark coverage. Hair-like spines have been noted previously, but no function has been attributed to them. This is the first report with a description of emergent spines on tall, long-lived columnar cactus species.

Areole Changes during Bark Formation on Saguaro Cacti

Spines are an important component of cactus species. Besides providing protection from predation, they reduce heat loading, reduce transpiration, and aid dispersal of stem segments for vegetative propagation among others. Bark formation occurs on surfaces of more than twenty species of columnar cacti in the Americas. For all species tested, bark formation is related to direct sunlight exposure. Extensive bark coverage leads to premature death for saguaro cacti (Carnegiea gigantea). Preliminary evidence indicates that changes in areoles with spines occurred during the bark formation on C. gigantea. Four hundred, sixty-one paired photographic images of areoles of north- and south-facing surfaces of shoots with bark percentages on adjacent troughs in 2017 were analyzed to determine differences between north- and south-facing surfaces. As in past studies, south-facing surfaces had higher bark percentages (mean bark coverage 62%) than north-facing surfaces (mean bark coverage 19%). For north and south areoles, mean numbers of central spines were 2.70/1.55; radial spines 3.20/1.50; and apex spines 1.81/1.13, respectively. When data were pooled to compare numbers of central, radial and apex spines as well as spine color and spine thickness, all were significantly related with bark percentages. Decreases in numbers and characteristics of spines precede bark formation on adjacent troughs. Overall, the results show that crests deteriorate faster than adjacent troughs. To our knowledge, this is the first report to document changes in spine numbers and characteristics with bark coverage on a cactus species.

The bark anatomy of Ningxiaites specialis from the Permian of China

Bark is an important functional structure in woody plants. However, fossil tree axes are commonly decorticated. The development of bark during the evolutionary history of fossil plants thus remains poorly understood. Here, we describe exceptionally well-preserved extraxylary tissues of the Lopingian (Late Permian) conifer Ningxiaites specialis Feng, including vascular cambium and bark, from the Sunjiagou Formation (Changhsingian) of northern China. The vascular cambium bears one or two layers of cambial cells. The bark comprises secondary phloem and periderm. The secondary phloem consists of rays, axial parenchyma and sieve cells. The rays of the secondary phloem are uniseriate and continuous from the rays of the xylem. They are more frequently present in the inner zone of the secondary phloem. Axial parenchyma cells are vertically aligned and appear more regularly distributed in the outer zone of the secondary phloem. Elliptical or subcircular sieve areas are placed on the radial walls of the sieve cells. The periderm located outside the secondary phloem is composed of imbricate flattened cork cells. The cork cells show suberised cell walls and are generally filled with dark contents. Remains of the secondary phloem present between layers of periderm indicate the formation of rhytidome-type bark. This is the first detailed report of the bark anatomy of a conifer from the upper Palaeozoic of Cathaysia, and shed light on the early diversity of bark structure during the evolutionary history of conifers.

Sunlight-induced bark formation in long-lived South American columnar cacti

Previous research has shown that sunlight-induced bark formation (epidermal browning) on vertical surfaces of tall, long-lived columnar cactus species leads to premature death of entire plants. The bark cambium that produces bark for cactus species has been shown to involve proliferation of epidermal cells only. The purpose of this research was to understand (1) the characteristics of cuticles, epidermal and hypodermal cells, (2) the process of sunlight-induced bark formation, and (3) changes in hypodermal cells during the bark formation process for many species of long-lived, columnar cacti from South America. A wide diversity of epidermal and hypodermal cells occurred among the species studied. Epidermal depths ranged from 8.7 to 49.7μm and involved one to several epidermal cells while the thickness of hypodermal cell layers ranged from 42.7 to 661μm among the species studied. During bark cambium formation, each epidermal cell underwent at least one anticlinal cell division prior to numerous periclinal cell divisions since lengths of initially produced bark cambium cells were half the lengths of uninjured epidermal cells. Some cactus species exhibited hypodermal cell injuries during bark formation. This study reports: (1) quantitative measurements of cuticles, epidermal and hypodermal layers, (2) the presence of anticlinal cell divisions of epidermal cells to produce the bark cambium, and (3) the destruction of hypodermal cells during bark formation for columnar cactus species of South America. Possibly these results are specific for sunlight-induced bark formation for cactus species while other types of injuries may result in bark production by other means.

Predicting morbidity and mortality ofCarnegiea gigantea1

Abstract Research has shown that older plants of more than 20 species of tall, long-lived cacti of the Americas have surface bark injuries. This bark is caused by sunlight exposures over several decades. This bark formation (which first appears on south-facing surfaces) leads to premature morbidity and eventually premature mortality (rates of 2.3% per year for Carnegiea gigantea. Current research was aimed at changes in C. gigantea bark formation over a 4-yr period. Of the 89 C. gigantea analyzed, 35% died. Among survivors, surface areas with bark increased by 20% over the 4-yr period. Rib troughs of a more southerly orientation had more bark injuries (up to 15% more) than troughs with a more northerly orientation. Over time, the amount of bark on north-facing troughs becomes similar to bark levels on south-facing troughs. Machine learning techniques that used 18 parameters of bark percentages on cactus surfaces had an 84% probability of predicting cactus death with two independent methods. Machine learni...

Sunlight-induced bark formation on current-year stems of Euphorbia plants from South Africa

Species of Euphorbia from South Africa have sunlight-induced bark injuries on stems visually identical to sunlight-induced injuries on more than twenty species of long-lived columnar, candelabra cactus species of the Americas. Injury ratios on stems on both groups of plants were similar to ratios of direct sunlight exposure on stem surfaces averaged throughout the annual cycle at many latitudes. Injuries on Euphorbia species occurred on current-year stem tissues. Stem tissues of Euphorbia species have a single-celled epidermis. Some species had a 2- to 3-celled hypodermis. Sunlight-induced bark formation only involved anticlinal followed by periclinal cell divisions of epidermal cells. No other cells were involved in bark formation. Many Euphorbia species have crests and troughs while others have prominent tubercles. Experimental results showed that prominent crests provided shading to concave troughs on some Euphorbia species and these species had less sunlight-induced barking. In contrast, other Euphorbia species that do not have prominent crests have little self-shading and these species had more sunlight-induced barking. Sunlight-induced bark formation occurred during a one year of sunlight exposure on Euphorbia stems while similar barking injuries occur on cactus stems only after several decades of sunlight exposure. These sunlight-induced injuries on young stem tissues of Euphorbia stems may result since current-year stems of Euphorbia plants had thinner cuticles and thinner epidermal/hypodermal layers compared with stem surfaces of cactus plants.

Susceptibility to Apple Ring Rot Infection of Apple Branches of Different Ages and Preventive Effect of Fungicides on Wart Bark Formation

Susceptibility to Apple Ring Rot Infection of Apple Branches of Different Ages and Preventive Effect of Fungicides on Wart Bark Formation

Analyses of early rough bark phenotype found in seedlings of a cross between the European pear ‘Bartlett’ and the Chinese pear ‘Yali’

One of the morphological symptoms of old age in trees is the development of rough bark on trunks and branches. Here we characterized pear seedlings with a unique phenotype, early rough bark (ERB). Eight-year-old normal and ERB seedlings from a cross between the European pear (Pyrus communis) cultivar ‘Bartlett’ and the Chinese pear (Pyrus bretschneideri) cultivar ‘Yali’ were used for morphological analyses and the determination of carbohydrates and lignin. Many rough surface patches were observed on the stems of 2-year-old ERB shoots, and most stem surfaces were covered by rough bark in 3-year-old ERB shoots while most stem surfaces were smooth in 2- and 3-year-old normal shoots. ERB plants also displayed rough-barked trunks, and the trunk surface was relatively smooth in normal plants. The content of lignin, one of the major components of cork tissues, was higher in ERB plants than in normal plants. The levels of starch and sucrose, which play roles in storage and translocation of carbon, were higher in ERB plants than that in normal plants, suggesting that the rate of carbon use is low in ERB plants. The novel phenotype ERB may enable future research on the formation of rough bark in fruit trees.

De novo assembly and characterization of bark transcriptome using Illumina sequencing and development of EST-SSR markers in rubber tree (Hevea brasiliensis Muell. Arg.)

BackgroundIn rubber tree, bark is one of important agricultural and biological organs. However, the molecular mechanism involved in the bark formation and development in rubber tree remains largely unknown, which is at least partially due to lack of bark transcriptomic and genomic information. Therefore, it is necessary to carried out high-throughput transcriptome sequencing of rubber tree bark to generate enormous transcript sequences for the functional characterization and molecular marker development.ResultsIn this study, more than 30 million sequencing reads were generated using Illumina paired-end sequencing technology. In total, 22,756 unigenes with an average length of 485 bp were obtained with de novo assembly. The similarity search indicated that 16,520 and 12,558 unigenes showed significant similarities to known proteins from NCBI non-redundant and Swissprot protein databases, respectively. Among these annotated unigenes, 6,867 and 5,559 unigenes were separately assigned to Gene Ontology (GO) and Clusters of Orthologous Group (COG). When 22,756 unigenes searched against the Kyoto Encyclopedia of Genes and Genomes Pathway (KEGG) database, 12,097 unigenes were assigned to 5 main categories including 123 KEGG pathways. Among the main KEGG categories, metabolism was the biggest category (9,043, 74.75%), suggesting the active metabolic processes in rubber tree bark. In addition, a total of 39,257 EST-SSRs were identified from 22,756 unigenes, and the characterizations of EST-SSRs were further analyzed in rubber tree. 110 potential marker sites were randomly selected to validate the assembly quality and develop EST-SSR markers. Among 13 Hevea germplasms, PCR success rate and polymorphism rate of 110 markers were separately 96.36% and 55.45% in this study.ConclusionBy assembling and analyzing de novo transcriptome sequencing data, we reported the comprehensive functional characterization of rubber tree bark. This research generated a substantial fraction of rubber tree transcriptome sequences, which were very useful resources for gene annotation and discovery, molecular markers development, genome assembly and annotation, and microarrays development in rubber tree. The EST-SSR markers identified and developed in this study will facilitate marker-assisted selection breeding in rubber tree. Moreover, this study also supported that transcriptome analysis based on Illumina paired-end sequencing is a powerful tool for transcriptome characterization and molecular marker development in non-model species, especially those with large and complex genomes.

Taxonomy of Wiborgiella (Crotalarieae, Fabaceae), a Genus Endemic to the Greater Cape Region of South Africa

Abstract A taxonomic revision of the recently described genus Wiborgiella is presented. Nine species are recognized within the genus, two of which are newly described, W. dahlgrenii and W. vlokii . The genus is endemic to the Cape region of South Africa and most species are highly localized and rare. Wiborgiella species can be distinguished from other genera in the tribe Crotalarieae by a combination of brown young branches (early formation of bark in the stems of the perennial species), laminar trifoliolate leaves, glabrous petals, a 4 + 6 anther arrangement, and oblong, wingless, inflated fruit. Anatomical studies revealed that all species of the genus have dorsiventral leaves (mesophyll differentiated into palisade parenchyma adaxially and spongy parenchyma abaxially) with mucilage cells in the epidermis which distinguishes Wiborgiella from other closely related genera, such as Calobota which has isobilateral leaves without mucilage cells. The fruits of Wiborgiella species are all thin-walled, have hig...

Stem CAM in arborescent succulents

Stem CAM with a peripheral chlorenchyma in stem succulents growing up to arborescent sizes and life forms appears to be a unique evolution as it requires delayed and reduced bark formation and stem stomata. However, stem succulence as a convergent morphotype and with it the stem CAM physiotype evolved polyphyletically in many divergent taxa of the dicotyledonous angiosperms. Controlling water budgets is the main ecophysiological benefit of stem succulence and CAM, where the cooperation of a peripheral photosysnthetically active chlorenchyma and a central water storing hydrenchyma is co-ordinately regulated. Thus, a major factor important for performance of stem CAM succulents at the community level is water or drought. Although this implies fitness under osmotic stress, CAM performing stem succulents are not adapted to salinity and are salt stress avoiders where they occur in saline habitats. Notwithstanding the low overall productivity of CAM plants in general, stem CAM plants can show very high productivity under certain circumstances and may also respond to elevated environmental atmospheric CO2 concentrations with increased growth.

Basal cactus phylogeny: implications of Pereskia (Cactaceae) paraphyly for the transition to the cactus life form

The cacti are well-known desert plants, widely recognized by their specialized growth form and essentially leafless condition. Pereskia, a group of 17 species with regular leaf development and function, is generally viewed as representing the "ancestral cactus," although its placement within Cactaceae has remained uncertain. Here we present a new hypothesis of phylogenetic relationships at the base of the Cactaceae, inferred from DNA sequence data from five gene regions representing all three plant genomes. Our data support a basal split in Cactaceae between a clade of eight Pereskia species, centered around the Caribbean basin, and all other cacti. Two other Pereskia clades, distributed mostly in the southern half of South America, are part of a major clade comprising Maihuenia plus Cactoideae, and Opuntioideae. This result highlights several events in the early evolution of the cacti. First, during the transition to stem-based photosynthesis, the evolution of stem stomata and delayed bark formation preceded the evolution of the stem cortex into a specialized photosynthetic tissue system. Second, the basal split in cacti separates a northern from an initially southern cactus clade, and the major cactus lineages probably originated in southern or west-central South America.

Book Reviews

Book reviewed in this article: Winter Garden Glory. Adrian Bloom Gardening with Perennials Month by Month. Joseph Hudek Flora Europaea. Volume 1, second edition, Psilotaceae to Platanaceae. Edited by T. G. Tutin, N. A. Burgess, A. O. Chater, J. R. Edmondson, V. H. Heywood, D. M. Moore, D. H. Valentine, S. M. Walters and D. A. Webb, assisted by J. R. Akeroyd and M. E. Newton Bark. The Formation, Characteristics and Usefulness of Bark around the World. Ghillean Tolmie Prance and Anne E. Prance

Ontogenetic mechanisms and the evolution of Cactaceae

Abstract The ancestors of cacti were leafy trees that had hard, woody trunks. The development of the cactus body is controlled by ontogenetic mechanisms that have evolved, and now they produce a body that is leafless, succulent and has a photosynthetic cortex. Specific changes include: bark formation is postponed and the epidermis and stomata function for many years; the outer cortex is a palisade cortex with intercellular spaces; there are cortical bundles that resemble leaf veins but which have secondary xylem and phloem. Wood development has changed dramatically such that water storage is maximized (increased ray parenchyma) and danger of water stress is minimized (increased paratracheal parenchyma, loss of fibers). Several genera have polymorphic wood: the plants produce one type of wood for several years, then later they produce a different type. It is possible that the extensive evolutionary changes have resulted from mutations in the controller regions of genes, not in the structural regions.