China's rare plants, dendrobium--英国Essay代写范文精选

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51due论文代写网精选essay代写范文：“China's rare plants, dendrobium”。石斛兰是一种药用价值很高的传统草本植物，素有“北有人参 南有枫斗（石斛）”之说。这种植物也被称为“可以救命的药草”。本篇论文通过对石斛的资源、药用价值、种植等多方面描述，让大家对这种珍贵的药草有深入了解。

Dendrobium is a kind of valuable traditional herbal plant in China and it has been recognized since ancient China with the saying “In Northern China, there’s ginseng; in Southern China, there’s Dendrobium”. This plant is also called as “herbal that can save life” by Chinese people. As a medicinal plant, dendrobium has been first recorded in Sheng Nong's herbal classic, and was classified as top grade herbal. There’re also other records that can be found in various well known traditional Chinese medicine classics, including Compendium of Materia Medica and Chinese medicine dictionary . Dendrobium has over 1500 subspecies, and about 50 of them have medicinal value according to the records. The most commonly seen subgroup includes Dendrobium huoshanense, Dendrobium officinale Kimura et Migo and Dendrobium devoninum Paxt.

Dendrobium huoshanense C.Z. Tang et S.J. Cheng (abbreviated to Dendrobium huoshanense) is recognized as highest grade of Dendrobium and the only specifically described medicinal Dendrobium in various medicinal classics. In the book of Supplements to Compendim of Materia Medica, written by Zhao Xuemin in Qing dynasty, the habitat, morphology, characteristics and effects of Dendrobium huoshanense were illustrated in detail. Dendrobium huoshanense is named after its growing area, which is located at Huoshan, Anhui province, the middle region of east coast in China. Bedsides, Dendrobium huoshanense has high requests for environment with proper climate, humidity, temperature and soil. So the distribution is very centralized in small areas. Studies have proved that Dendrobium huoshanense was effective in treating tumor, preventing cataract and protecting stomach and promoting saliva secretion. In recent years, due to the special growing condition and excessive collection, the wild plant resources of Dendrobium huoshanense are on the verge of extinction, despite the fact that research about the sustainable development of Dendrobium huoshanense has been carried out since 1950s.

1.Resource of Dendrobium huoshanense

Dendrobium huoshanense prefers cool shady humid place, usually together with moss and herba pyrrosiae. Dendrobium huoshanense absorbs the water in air by fibrous root that’s exposed. The light saturation point, light compensation point and net photosynthetic rate are low, and the opening of pore on the leaf and photosynthesis are easily affected by humidity (Xu Yun et al.,1993). The specific requirements of environmental condition directly limit Dendrobium huoshanense grow at narrow regions. Right now, Dendrobium huoshanense mainly distributes at Huoshan, Jinzai, Yuexi of Anhui province, and Nanzhao of Henan province(Wang Dequn, 1999). These areas locate within the region of Dabie Mountain, a very famous great mountain in the middle of China. Research also found that the seeds of Dendrobium huoshanense were tiny and contained little endosperm, thus the germination percentage of seeds were low in natural state (Wang Dequn ang Peng Husheng, 2004). The factors stated above result in the shortage of natural resource of Dendrobium huoshanense. According to Hoshan Diary in Anhui province, only about 1-5kg fresh Dendrobium huoshanense would be collected during 1950-1975. Another survey also reviewed that 4.4kg fresh herbal had been collected from only 3 spots in 1980s (Xu Yun et al.,1993). Survey about the wild resource in recent years can hardly find Dendrobium huoshanense. Besides, rare study about the genetic resources and diversity of Dendrobium huoshanense was reported or found because of the limited distribution of the resource and production. It’s been studied that the hybrid Dendrobium huoshanense showed obvious change in the growth curve, amount of chemical components and quality, compared with non hybrid ones, which provided a way of thinking to improve the genetic resource of Dendrobium huoshanense by enriching genetic polymorphism(Wang Shu, et al.,2006).

2. Components of Dendrobium huoshanense  http://www.51due.net/writing/essay/sample147.html

Dendrobium huoshanensein is a kind of rare plants with medicinal, health, food, and ornamental values. Among them, the medicinal value has greatly attracted the interest of scientists. It’s proved that there’re various micro chemical components in Dendrobium huoshanense, including alkaloid, sesquiterpenoids, coumarone, steroids, essence oils, et al. And still there’s much to be done for researches to go in depth.

Polysaccharide is the main component of Dendrobium huoshanens, which also was investigated at the very first in laboratory. HPS-1B23 was a kind of  such Polysaccharide that extracted from Dendrobium huoshanensein and had been testified to enhance immune vitality(Li Shengli, et al.,2015).

The total alkaloids of Dendrobium huoshanensei in different parts of the plant at different growth phase were also studied (Ding Yaping, et al.,1994). The result indicated that the amount of total alkaloids in Dendrobium huoshanense followed as the sequence from more to less as leaf, stem and root, and 3 year stem, 4 year stem, 2 year stem and 1 year stem. The same research group also analyzed the amount of micro elements, amino acid, soluble polysaccharide, soluble protein and vitamin C in Dendrobium huoshanense. By the statistics, researchers came to the conclusion that the leaf, stem and root contained similar components, while the best harvest time should be the third year.

3. Pharmacological Effect of Dendrobium huoshanense

The pharmacological effect of Dendrobium huoshanense has been recorded in Chinese works of materia medica in all ages. It’s been reported that Dendrobium huoshanense has functions as anti-oxidization, suppressing the progress of cataract and immunity enhancement. Scientists reported the antioxidation effect of extracted substance from Dendrobium huoshanense (Wang Shu, et al., 2009). They compared the capacity of eliminating free radicals between Dendrobium huoshanense and Dendrobium officinale Kimura et Migo, and the result indicated that Dendrobium huoshanense was more effective in preventing oxidation. Using the diabetic rat model, research also found that Dendrobium huoshanense could suppress the formation and development of cataract (Li Xiufang, et al.,2012). The mechanism lied in the down regulation of NO synthase and up regulation of the vitality of some antioxidant enzyme. The two steps coordinated to inhibit the process of protein degeneration in lens and slow down the development of cataract. There’re other researchers showed Dendrobium huoshanense could help to stimulate the megalophage and spleen cells in rat to release cytokine as TNF-a, IFN-g, IL-10 and thus enhance the immunity in body(Lan-Zhen Meng, et al.,2005).

From the classics, other effectiveness of Dendrobium huoshanense are also listed, including moisture of lung, maintenance of visceral, being good to brain and curing insomnia. Since Chinese people has a long history of treating illness and disease by herbals, it’s also their common practice to make the edible herbal into cuisine for the sake of health care. Thus unlike pills, Dendrobium huoshanense sometimes is more like a kind of top grade food rather than medicine.

4. Seeding and culture

In recent years, the seedling techniques with the tissue culture, as well as rapid propagation have achieved great progresses with the advances of biotechnology(Tan Yun, et al., 2005). The propagation, methods and breeding of Dendrobium huoshanense (also of other Dendrobium plants) in China were researched and the findings were summarized, including aseptic seed embryo culture, propagation in vitro, ramets propagation, layering propagation and cutting propagation. All these efforts are going to support an provide scientific basis for the development and use of Dendrobium huoshanense(Li Rui, et al., 2011).

5. Conclusion and Discussion

Over 50 years of research, great advances of growing Dendrobium huoshanense have been achieved. The investigation of the chemical components and the pharmacological effect also has favorable starts. For the harsh environment requirement of plantation of Dendrobium huoshanense, the artificial cultivation still remain in small trail stage and the resource is still in shortage. The government and public have realized the severity of over collection and the importance protection of Dendrobium huoshanense. Meanwhile, efforts have been put into the exploration of the techniques of artificial cultivation of Dendrobium huoshanense. However, there’re two major problems still need to be addressed as soon as possible.

5.1 From current research data and materials, there’s no technical barrier in rapid propagation of test-tube plantlet in laboratory stage, but the field transplant of  test-tube plantlet still remain to be the bottleneck of industrialization of Dendrobium huoshanense. Though there’s trial of transplantation, the percentage of success was rather low and almost impossible to realize the massive scale production. In addition, more studies are needed to investigate the physiological, biochemical and ecological factors that constitute the barrier to the field transplantation. Only after that, the large scale transplantation and sustainable development can be achieved.

5.2 Though Dendrobium huoshanense wins the great welcome of ordinary people that lots of relevant health products have been launched, the effective substance and the standard amount of such substance remains to be investigated specifically. That’s to say, the function of Dendrobium huoshanense are experimental just like other traditional Chinese medicinal herbal, rather than those western medicine that is carefully measured when studied. On the other hand, the standard to judge the quality of Dendrobium huoshanense is not reliable. Rough judging from the purchase price of Dendrobium huoshanense, the appearance seems to be the influencing factor. The fat and short and juice ones are more welcomed for they seem to have higher percentage of polysaccharose. Besides, judging from the quality and quantity of literature that could be collected, researches about the function of Dendrobium huoshanense are very simple and preliminary. Therefore, more in depth researches are required to be carried out to explore the composition, biological vitality, therapeutic effect of Dendrobium huoshanense.  -H

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