Dragon Tree Research Articles

The Overfull Nine Dragon Tree Conjecture is True

The Overfull Nine Dragon Tree Conjecture is True

Chromosome-level and haplotype-resolved genome assembly of Dracaena cambodiana (Asparagaceae)

Dracaena cambodiana Pierre ex Gagn. (Asparagaceae) is the source plant of Dragon’s blood and has high ornamental values in gardening. Currently, this species is classified as the second-class state-protected species in the National Key Protected Wild Plants (NKPWP) of China. However, limited genomic data has hindered a more comprehensive scientific understanding of the processes involved in the production of Dragon’s blood and the related conservation genomics research. In this study, we assembled a haplotype-resolved genome of D. cambodiana. The haploid genomes, haplotype A and haplotype B, are 1,015.22 Mb and 1,003.13 Mb in size, respectively. The completeness of haplotype A and haplotype B genomes was 98.60% and 98.20%, respectively, using the “embryophyta_10” dataset. Haplotype A and haplotype B genomes contained 27,361 and 27,066 protein-coding genes, respectively, with nearly all being functionally annotated. These findings provide new insights into the genomic characteristics of D. cambodiana and will offer additional genomic resources for studying the biosynthesis mechanism of Dragon’s blood and the horticultural application of Dragon trees.

Correction to: New insight into secondary growth in roots of monocotyledons using the example of the dragon tree, Dracaena draco L.

Correction to: New insight into secondary growth in roots of monocotyledons using the example of the dragon tree, Dracaena draco L.

Identification of dragon trees and fruits in ham Thuan Bac growing areas, Phan Thiet city, Binh Thuan province, Vietnam

With the development of Computer Vision, we can effectively and accurately identify trees, fruit or object images. But to build a high-performance image dataset for tree identification problems in Agriculture is a challenge. Realizing that Vietnam is a country with strong agriculture with many tropical fruits grown widely such as Dragon fruit, Mangosteen, Mango, Orange, Lychee, Longan … We chose the Dragon Fruit tree for the data set. of my proposed images, all images will be collected using the close-up method, including tasks such as taking photos of Dragon Fruit trees from many angles and in different conditions (weather, temperature, light, …). In this article, we want to improve the data quality of the collected images so we have applied image processing techniques such as noise filtering (using Gaussian filter), image quality enhancement (image rotation), flip the image, zoom out, zoom in, etc.). From the collected Dragon Fruit tree data set, we will propose to use the Faster R–CNN model for this data set to build a tree and Dragon Fruit identification system.

New insight into secondary growth in roots of monocotyledons using the example of the dragon tree, Dracaena draco L.

New insight into secondary growth in roots of monocotyledons using the example of the dragon tree, Dracaena draco L.

Longevity Estimates of Canary Palms and Dragon Trees via Radiocarbon Dating: Initial Results.

Correctly estimating the maximum lifespan of plant species is a necessary component of demographic and life-history studies, which, in turn, are needed for understanding climatic impacts. Arboreal monocotyledons, which can grow to >30 m in height and >5 m in trunk perimeter, are difficult to age because they do not undergo seasonal dormancy; hence, their longevity has been estimated using various size-related methods. In this study, we tested radiocarbon (14C) dating with Accelerator Mass Spectrometry (AMS) as an additional tool for determining the age of two iconic monocotyledons: the Canary Island palm and the dragon tree. A total of 25 samples were collected from the basal stem of four palms and five dragon trees on Gran Canaria and Tenerife and then processed using the most advanced 14C-AMS analysis available. Calibration curves provided by the "IntCal group" were used to determine the oldest possible age of each sample, and 16 of them were found to be "modern", i.e., formed after the 1950s. Nine samples that were either collected from exterior, but lignified, palm tissues or from interior, and lignified, dragon tree tissues suggested ages > 300 years. Given the constant improvement of 14C-AMS tools, they can contribute to the further refinement of existing scientific knowledge on Macaronesian charismatic megaflora.

Germination niche of the endangered dragon tree Dracaena draco (L.) L. subsp. draco of the Macaronesian Islands

The Canary Islands dragon tree (Dracaena draco (L.) L. subsp. draco) is an endangered Tertiary relict species endemic to the Canary and Madeira archipelagos. Based on an ex-situ experiment under controlled conditions, we investigated its germination response to both constant and alternating temperatures, moisture levels (water potential), exposure to light, and desiccation. We found that suitable temperatures for germination (> 5 % of germinated seeds) range from 12.1 °C to 32.8 °C (thermal germination niche limits) and optimal temperatures (> 95 % of germinated seeds) range from 16.6 °C to 28.3 °C. Light exposure and water potential below 0 MPa drastically decreased germination performance while seed desiccation pre-treatments and alternating temperatures had slightly negative effects. Comparing the spatial projection of the thermal germination niche with actual occurrences of D. draco subsp. draco revealed that native populations are mainly distributed in areas where temperatures are colder than the optimum for germination. For native populations, germination rate is predicted to reach 78 % on average based on temperature requirements. Our results suggest that niche conservatism and adaptation are involved in shaping the germination requirements of the dragon tree.

The Strong Nine Dragon Tree Conjecture is True for $$d \le k + 1$$

The Strong Nine Dragon Tree Conjecture is True for $$d \le k + 1$$

Transcriptomic Analysis Reveals the Involvement of Flavonoids Synthesis Genes and Transcription Factors in Dracaena cambodiana Response to Ultraviolet-B Radiation

Ultraviolet-B (UV-B) radiation is a major abiotic stress that dragon trees are exposed to during their growth and development; however, it is also an environmental signal perceived by plants that affects the flavonoid pathway. Previous studies have demonstrated that amounts of flavonoids are contained in dragon tree resin, otherwise known as dragon’s blood. However, the traits and mechanism involved in the UV-B-mediated increase in flavonoids in dragon trees are still unknown. Here, we studied the response of Dracaena cambodiana under full solar UV-B radiation. The results showed that the contents of total flavonoids in D. cambodiana significantly increased after UV-B radiation exposure. Then, the transcriptome was used for determining the interactive mechanism of flavonoid accumulation and UV-B stress. Differential expression analyses identified 34 differentially expressed genes (DEGs) involved in flavonoid synthesis; specifically, 24 of the identified DEGs were significantly up-regulated after UV-B radiation exposure. In addition, 57 DEGs involved in Ca2+/kinase sensors, 58 DEGs involved in ROS scavenging and the plant hormone pathway, and 116 DEGs transcription factors in 5 families were further identified and analyzed. Finally, we deduced the potential mechanism of UV-B-promoting flavonoid formation to neutralize ROS damage derived from UV-B radiation in D. cambodiana based on the gene co-expression network and previous studies from other plants. Considering that wild dragon tree populations are currently highly threatened by anthropogenic and natural stressors, the interactive studies between D. cambodiana plants and UV-B radiation provide valuable information toward understanding the mechanism of dragon’s blood formation and help us reveal the evolution of D. cambodiana, with the eventual goal of aiding in the global conservation of this precious biological resource.

UAV Inventory of the Last Remaining Dragon Tree Forest on Earth

The last remaining Dragon Tree Forest on Earth survives on a small plateau (Roqeb di Firmihin) in Socotra Island (Yemen). The Socotran Dragon’s Blood Tree (Dracaena cinnabari Balf. f.) is endemic to the Socotra Archipelago UNESCO World Heritage Site. Being a culturally important and endangered tree species, its conservation is a priority. Despite this, a complete inventory of the Firmihin Dracaena forest (14.9 km2) has never been attempted before. We applied the use of unmanned aerial vehicles (UAVs) for the first time in conserving the Socotran Dragon’s Blood Tree. A pair of UAVs (small drones) were used during field surveys in 2021 to spatially describe individual tree positions, tree density, mortality, and the forest age structure. Aerial images were processed into a single orthophoto image of high spatial resolution (8 cm/pixel) used for detailed analysis. We applied image-enhancement techniques, used object-based classification, and corrected every entry manually during the inventory process. In total 35,542 individual living trees and 2123 uprooted trees were inventoried. The mean age of the forest, based on crown age (derived from crown size) was estimated at an average of ca. 300 years (291.5 years) with some individuals older than 500 years. Our analysis reveals that the trajectory of recent cyclones and the average direction of fallen trees in Firmihin are correlated, suggesting that intensified winds (as a result of global warming) catalyze the decline of the overmature forest. Our study illustrates the use of UAVs in collecting crucial data for the conservation and threat assessment of endangered tree species in Socotra, and regular drone inventories could be applied (e.g., after future cyclone events or landslides) to better evaluate the status of these vulnerable island ecosystems.

Prioritizing forest conservation strategies using a multi-attribute decision model to address concerns with the survival of the endangered dragon tree (Dracaena ombet Kotschy and Peyr.)

The globally endangered Dracaena ombet is one of the ten dragon multipurpose tree species in arid ecosystems. Anthropogenic and natural factors are now impacting the sustainability of the species. This study was conducted to prioritize criteria and alternative strategies for conservation of the species using the Analytical Hierarchy Process (AHP) model by involving all relevant stakeholders in the Desa'a dry Afromontane forest, northern Ethiopia. Information about the potential alternative strategies and the criteria for their evaluation were first collected from experts, personal experiences and literature reviews. Afterwards, they were validated using stakeholders' focus group discussions. Five candidate strategies with three evaluation criteria were considered for prioritization using the AHP techniques. The overall priority ranking value of the stakeholders showed that the ecological criterion was deemed as the most essential factor for the choice of the alternative strategies, followed by the economic and social criteria. The minimum cut-off strategy, combining exclosures with collection of only 5% of plant parts from the species, soil and water conservation and habitat protection management options, was selected as the best alternative strategy for sustainable D. ombet conservation. The livelihood losses due to the selected strategy should be compensated by the collection of non-timber forest products, poultry farming, home gardens, rearing small ruminants, beekeeping and agroforestry. This approach may be extended to study other dragon tree species and explore strategies for the conservation of other arid ecosystems.

Observations on Portuguese natural history by Leonhard Thurneysser zum Thurn (1531–1596), including the dyes derived from Kermes vermilio and Dracaena draco

In 1555, Leonhard Thurneysser zum Thurn (1531–1596), a young apothecary, alchemist, astrologer and healer from Basle in Switzerland, travelled to Portugal and stayed in Lisbon with Damião de Góis (1502–1574), the Portuguese humanist and diplomat. The principal purpose of Thurneysser’s visit was the study of natural history and the observations and information that he collected then and during a second trip about 1562. These observations were recorded in a manuscript that remained unnoticed until the twenty first century. Thurneysser’s manuscript, now held in the Staatsbibliothek zu Berlin, contains descriptions of animals, plants and of two economically important dyestuffs, kermes and dragon’s blood, the first obtained from the scale insect, Kermes vermilio (associated with Quercus coccifera, kermes oak), and the second from Dracaena draco (dragon tree). Thurneysser’s contributions to knowledge of these two products and their associated plants were innovative and reveal an observer endowed with exceptional insight. His main sources of information, in addition to his personal fieldwork, observation of goods sold in Lisbon markets and conversations with vendors and merchants, were the classics of Antiquity and contemporary works including two of Damião de Góis’s works, Hispania (1542) and Urbis Olisiponis descriptio (1554).

Digraph analogues for the Nine Dragon Tree Conjecture

AbstractThe fractional arboricity of a digraph , denoted by , is defined as . Frank proved that a digraph decomposes into branchings, if and only if and . In this paper, we study digraph analogues for the Nine Dragon Tree Conjecture. We conjecture that, for positive integers and , if is a digraph with and , then decomposes into branchings with . This conjecture, if true, is a refinement of Frank's characterization. A series of acyclic bipartite digraphs is also presented to show the bound of given in the conjecture is best possible. We prove our conjecture for the cases . As more evidence to support our conjecture, we prove that if is a digraph with the maximum average degree and , then decomposes into pseudo‐branchings with .

Theoretical considerations regarding the functional anatomical traits of primary and secondary xylem in dragon tree trunk using the example of Dracaena draco

Main conclusionIn Dracaena draco trunks, the primary and secondary xylem conduits co-function. Both are resistant to embolism; however, secondary conduits are mainly involved in mechanical support.Monocotyledonous dragon trees (Dracaena spp., Asparagaceae) possess in their trunks both primary and secondary xylem elements, organized into vascular bundles, that for dozens of years co-function and enable the plant to transport water efficiently as well as provide mechanical support. Here, based on the modified Hagen-Poiseuille’s formula, we examined the functional anatomical xylem traits of the trunk in two young D. draco individuals to compare their function in both primary and secondary growth. We provided analyses of the: (i) conduits surface sculpture and their cell walls thickness, (ii) conduit diameter and frequency, (iii) hydraulically weighted diameter, (iv) theoretical hydraulic conductivity, (v) area-weighted mean conduit diameter, as well as (vi) vulnerability index. The conduits in primary growth, located in the central part of the trunk, were loosely arranged, had thinner cell walls, larger mean hydraulically weighted diameter, and significantly larger value of the theoretical hydraulic conductivity than conduits in secondary growth, which form a rigid cylinder near the trunk surface. Based on the vulnerability index, both primary and secondary conduits are resistant to embolism. Taking into account the distribution within a trunk, the secondary growth conduits seems to be mainly involved in mechanical support as they are twisted, form structures similar to sailing ropes and have thick cell walls, and a peripheral localization. D. draco has been adapted to an environment with water deficit by distinctive, spatial separation of the xylem elements fulfilling supportive and conductive functions.

Endangered Dracaena ombet Population in the Red Sea Hills, Sudan, Recovers After Abrupt Change

The endangered and endemic Nubian dragon blood tree, Dracaena ombet, has been feared extirpated from core distribution areas in the Red Sea Hills, Sudan, after reported mass death events in the 20th century. Populations of dragon tree species are generally reported to be in decline, with a noticeable lack of recruitment and possible poor resilience. Rare recruitment events are, however, normal for species with remnant population dynamics, and when eventually occurring, such events can restore seemingly degraded populations. In response to recently reported observations of dracaena saplings in a historically core distribution area of the Red Sea Hills, we assess the status of this long-lived arboreal species. We describe a current realized niche, investigate a potential range shift by comparing the spatial distribution of saplings and older individuals, and assess population recovery based on pre-disturbance system identity derived from qualitative, historical observations. We document a beginning recovery of the dracaena population in the study area. Around half of the mapped population are individuals in the sapling stage, and they are in good health. Its current realized niche is described by higher altitudes, steeper slopes, more concave landscape forms and east-facing aspects compared to areas where dracaena individuals are absent. However, for the new generation of dracaena saplings we find signs of a leaning range shift where saplings are shifted towards higher altitudes near the mist-influenced escarpment. A full collapse and eventual extirpation of the endangered Dracaena ombet population may at best be averted, or at least delayed in the study area. Our resilience analysis indicates that a full recovery will be a slow process due to the inherent natural climate variability of arid lands, only allowing sporadic regeneration. Considering this species’ information legacy, saplings seem to be well equipped to survive such variability, but perhaps within a restricted safe operating space. Conservation measures should therefore be taken to secure the survival of the new generation along with broader spatial scale studies to confirm whether our findings reflect a regional phenomenon.

Циркадные ритмы температуры листьев драконова дерева и количество выпадающей на них росы

Циркадные ритмы температуры листьев драконова дерева и количество выпадающей на них росы

Revisiting the anatomy of the monocot cambium, a novel meristem

Main conclusionThe monocot cambium is semi-storied, and its cells do not undergo rearrangement.The monocot cambium is a lateral meristem responsible for secondary growth in some monocotyledons of Asparagales. It is an unusual meristem, not homologous with the vascular cambia of gymnosperms and non-monocotyledonous angiosperms. Owing to the limited information available on the characteristics of this meristem, the aim of this study was to survey the structure of the monocot cambium in order to clarify the similarities and dissimilarities of this lateral meristem to the vascular cambium of trees. Using the serial sectioning analysis, we have studied the monocot cambium of three species of arborescent monocotyledons, i.e., Quiver Tree Aloe dichotoma, Dragon Tree Dracaena draco, and Joshua Tree Yucca brevifolia, native to different parts of the world. Data showed that in contrast to the vascular cambium, the monocot cambium is composed of a single type of short initials that vary in shape, and in tangential view display a semi-storied pattern. Furthermore, the cells of the monocot cambium do not undergo rearrangement. The criteria used in identifying monocot cambium initial cell are also discussed.

Dragon Trees, Tertiary Relicts in Current Reality

Few of the about 190 species currently described in the plant genus Dracaena [...]

In vitro Propagation and Caulogenesis of Dracaena draco Plants

Dracaena draco is a monocot from family Asparagaceae. The dragon tree is a subtropical plant and features many botanic and Mediterranean gardens worldwide. D. draco has been categorized as vulnerable in Europe and endangered worldwide in the IUCN Red List of Threatened Species (IUCN, 1998). The aim of this study is to develop an efficient protocol for rapid in vitro propagation and caulogensis of D. draco Plants via enhanced axillary bud proliferation from single nodal explants cultured on full strength MS medium, 30g/l sucrose, 4g/l gelrite augmented with various concentrations of plant growth regulators as BA, NAA, IBA and their combinations. In general, the present study concluded that the best results for the initiation stage were recorded on MS medium fortified with NAA and BA at 2.00 and 1.00 mg/l, respectively. Meanwhile, supplemented medium with BA and NAA at 4.00 and 1.00 mg/l, respectively, gave rise to the best results for the multiplication stage. Regarding rhizogenesis stage, the best results were recorded when the neoformed shoots of the multiplication stage were divided singly and cultured on MS medium plus IBA and NAA at 1.00 and 0.50 mg/l, respectively which led to the highest mean number of roots formed per propagule. For callus induction, the internodal segments cultured into MS medium supplemented with BA and NAA at 0.50 and 2.00 mg/l, respectively, gave rise to the best results for the percentage of explants formed callus and callus size. Concerning the percentage of direct organogenesis and number of shoots formed per explants best results obtained from BA and NAA at 0.250 mg/l and 0.00 mg/l, respectively.Neoformed plantlets were acclimatized ex vitro and in vivo vigorously in a mixture of perlite and peat moss at (1:1) or (2: 2) or (2:3) and (3:3) consecutively, in addition to fixed volume (1 portion) of sterile sand; which resulted in the highest mean value of survival percentage/plant (100%) and showed true-to-type plants ex vitro.

Use of decayed wood for funerary practices: Archaeobotanical analysis of funerary wooden artefacts from Prehispanic (ca. 400–1500 CE) Gran Canaria (Canary Islands, Spain)

The island of Gran Canaria (Canary Islands, Spain) shows great potential for studying the wooden raw materials used by the indigenous population during the Prehispanic period based on xylological analyses from domestic and funerary contexts. This paper includes archaeobotanical data from wooden funerary artefacts recovered from several archaeological contexts of the island and deposited at El Museo Canario (Las Palmas de Gran Canaria, Spain). Our results provide pioneering data as only a few xylological and anthracological analyses have been carried out on this island. Thus, the preferential use of pinewood (Pinus canariensis) for the manufacture of most of the artefacts is suggested, although dragon tree wood (Dracaena sp.) has also been identified in some funerary boards. Wood selection criteria not focusing on healthy wood has been suggested based on a combination of the microscopic observation of fungal decay patterns and archaeoentomological data. In addition to this, morpho-technological analysis suggests extensive woodworking knowledge in a geographic context lacking metal ores. Further xylological and experimental research, including other islands of the archipelago, is needed to obtain a more comprehensive perspective of wood procurement and use during the Prehispanic period.