The secret of Dracaena Dracaena, a pharmacist in the plant kingdom

Recently, researchers from Xishuangbanna Tropical Botanical Garden of Chinese Academy of sciences have discussed the historical dynamic changes of Cambodian Dracaena population from the perspective of population genetics and genealogy According to reports, Cambodian Dracaena is the first material to test two hypotheses about the origin of biodiversity in the tropics Cambodian Dracaena, as a national second-class protected plant, its resin is a treasure - Dracaena Dracaena made in China However, it is such a "pharmacist" in the plant world, and all kinds of questions about it are still debated by people today Not long ago, researchers from the research group of plant systems and conservation biology of Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, discussed the historical dynamic changes of Cambodian Dracaena population from the perspective of population genetics and genealogy This study has made a breakthrough in further understanding the origin of biodiversity in the tropics So, what secrets does this research tell us about Dracaena? Why does dragon blood tree bleed? What is the special distribution pattern of Cambodian Dracaena? What is the current living environment? How can we protect it Li Qiaoming, an associate researcher at Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, explains these questions for readers Why does dragon blood tree bleed? There is a legend in the Folk: when the dragon and the elephant fight, the dragon blood sprinkles the earth, and the dragon blood tree is born out of the soil When the dragon tree is injured, it does not flow out of transparent liquid or white emulsion like ordinary trees, but is dark red like plasma mucus, which is considered to be dragon blood in legend Dragon blood tree gets its name "When the epidermis of Dracaena Dracaena is' injured ', it will produce a kind of secretion, which will form a red clot like clot under the action of microorganisms In fact, this is a self-protection mechanism of Dracaena Li Qiaoming said that when the body of the dragon blood tree is damaged, the red grease will overflow from the damaged part and cover the wound tightly, so that the damaged part will slowly self heal "As a special group of monocotyledons, Dracaena's phloem can grow secondary." It is precisely because of this self-protection function that Dracaena will live forever and is known as a living fossil in plants According to the data, the growth of Dracaena is very slow It takes hundreds of years to grow into a tree, and only once in decades What's more precious is that the red fat liquid from Dracaena Dracaena is the raw material for extracting the precious traditional Chinese medicine, Dracaena Dracaena Dragon's blood is a kind of precious south medicine Li Shizhen called it "the holy medicine of promoting blood circulation" in compendium of Materia Medica It is a commonly used medicine of promoting blood circulation, dispersing stasis and hemostasis Why does dragon blood tree like to survive in the cracks? According to Li Qiaoming, Cambodian Dracaena is mainly distributed in the South and southwest of Yunnan, southwest of Guangxi and south of Hainan It grows on limestone with an altitude of 950-1700m It is a cold resistant and calcium loving tree species It is also distributed in Cambodia, Thailand, Vietnam and Laos It is suitable for limestone crevice habitat, and is the dominant species in limestone local area Plants growing in tropical limestone mountains are sensitive to climate change, so Cambodian Dracaena is the first choice to test the hypothesis of origin of biodiversity in tropical areas There are two main hypotheses about the origin of biodiversity in the tropics, one is the product of long-term stable environment, the other is the product of Quaternary climate change Why does dragon blood tree choose to live in the "crack"? "According to our observation, it may be related to the water storage function of stem," Li Qiaoming said Although dragon's blood has been used for at least 1500 years in traditional medicine in China, when no domestic dragon's blood tree was found before 1972, the blood used has been imported from Southeast Asia and Africa, and the price is very expensive In 1973, Cambodian Dracaena was first found in Menglian, Cangyuan, Mengla and other counties in South Yunnan, which added a new domestic raw material variety to the production of Chinese medicine According to the reasons for the present distribution pattern of Cambodian Dracaena, Li Qiaoming's research team analyzed that: "when its seeds are spread to various places by birds, because of the collision between the Indian plate and the Eurasian plate, there is an orogenic movement, which forms an isolation barrier for the migration of Cambodian Dracaena and hinders the gene flow between populations, and then the climate change of Quaternary glacial period is further improved The isolation between populations was increased In some small areas, it is also related to human destruction Our current data cannot predict the original distribution pattern of Cambodian Dracaena What should we do to protect Dracaena? Cambodian Dracaena has been listed as the second class rare and endangered plant by the state since 2001, and listed in the Chinese plant red book rare and endangered plants "At present, the survival of Cambodian Dracaena is mainly threatened by two aspects." Li Qiaoming said that on the one hand, driven by economic interests, the wild Cambodian Dracaena trees have been dug and felled in disorder In addition, their natural regeneration capacity is poor, and the vegetation in the production area is constantly damaged, which seriously threatens their survival On the other hand, it is the impact of climate change In response to the phenomenon of man-made felling, Li Qiaoming said that through the establishment of some reserves, such as the menglianlong Mountain Nature Reserve, known as the dragon blood tree paradise, is a good example, which effectively protects this endangered species In the long run, we should strengthen education and let people develop the consciousness of protecting nature, not only the dragon blood tree Increase the development and utilization of Dracaena: through artificial propagation, large-scale production, when the artificial propagation of Dracaena occupies the market, the wild Dracaena may be protected As for whether Cambodian Dracaena can adapt to future climate change, Li Qiaoming said that it is impossible to predict at present, and further comprehensive research should be carried out in combination with physiological ecology, molecular biology and other disciplines - wired expert science and Technology Daily: "Cambodian Dragon Blood Trees in the north of the Indochina Peninsula and Hainan Island come from the south of the Indochina Peninsula" How can we draw this conclusion? Li Qiaoming: through extensive population sampling, using two chloroplast segments and six microsatellite markers, using molecular clock, genetic drift, genetic bottleneck and other models, we found this conclusion The figure on the right shows the haplotype network of Cambodian Dracaena "Outgoups" is based on the previous studies of phylogeny, selecting the primitive groups of Dracaena Cambodian The closer to "outgoups", the more primitive the haplotype The haplotypes connected with "outgoups" are all located in the south of Indochina Peninsula At the same time, haplotypes in other areas are derived from h14 Therefore, we speculate that "Cambodian Dracaena in the north of Indochina Peninsula and Hainan island comes from the south of Indochina Peninsula" Science and Technology Daily: how does this study come to the conclusion that "the recent common ancestor of Cambodian Dracaena began to differentiate in the tertiary, and the time of rapid intraspecific differentiation is in the Quaternary"? Li Qiaoming: since the formation and extinction of the lineage of Cambodian Dracaena continue to occur in the evolution process, we can only trace back to the nearest ancestor according to the existing lineage and ancestor tracing model The point where the nearest ancestor begins to differentiate and form the next lineage is the time point when it begins to differentiate Due to the influence of the dramatically changing geological history or climate, some genealogies may be concentrated in a certain period, which is the stage of rapid intraspecific differentiation, which is later than the time point of initial differentiation In order to calculate these two time points, we take the relative genera of Dracaena with known differentiation time as exotaxa, and estimate them by molecular clock model The initial differentiation time is in the late Tertiary, and the rapid differentiation time in the species is in the Quaternary Science and Technology Daily: the research results point out that "the differentiation of Cambodian Dracaena is affected by the uplift of the Qinghai Tibet Plateau and the Quaternary climate change" What are the specific impacts? Li Qiaoming: This is only speculation These effects include the formation of geographic isolation and intraspecific differentiation - a thousand year old God tree similar to UFO is isolated by the African continent in Socotra island in 1800 There is a mysterious plant called dragon blood tree, which has an average age of 8000 years and looks like an alien flying saucer Dracaena is one of the most vital tree species on the earth Because there are thousands of rare animals and plants on Socotra that do not exist in other areas, it is known as the most alien like place on earth Among them, the most peculiar shape is the dragon blood tree that looks like a flying saucer, so it is also regarded as sacred by the local people In addition, the prickly leaves of Dracaena Dracaena are not only like grooves, but also can guide the rainwater to the roots along the branches and trunk trees, and reduce the water loss like wax, so that the rainfall can flow to the roots quickly.