Effects Of Different Environmental Factors Combination On Growth And Active Component Contents In Dendrobium Candidum

Dendrobium candidum Wall.ex Lindl.,belongs to Dendrobium（Orchidaceae）,is a rare traditional Chinese medicine.It has significant anti-hyperglycemic,anti-tumor and immunity-improving activities.In recent years,wild resources of D.candidum are on the verge of exhaustion for excessive collection.As a result,artificial cultivation is of great significance for the protection of wild resources and the demand of markets.The difference of active components（total polysaccharides,total alkaloids and total flavonoids）of D.candidum in different ages,and the effects of different habitat factors（light,temperature,moisture,nutrients）on growth,photosynthetic characteristics and active components of D.candidum were measured in this paper to provide a scientific basis for the artificial large-scale cultivation.The results are showed below.1.Effects of total polysaccharides,total alkaloids and total flavonoids contents in stems and leaves of different age D.candidum.Total polysaccharides are mainly in the stems with high content（57%⁷4%）.Total alkaloids and flavonoids are mainly in the leaves with relatively low contents.Two years old stems of D.candidum had the highest total polysaccharide（35.32%）,the half year old leaves had highest total flavonoids（0.104%）,and annual leaves had the highest total alkaloids（0.036%）.If consider the biomass,active ingredients production,growth cycle and the cost together,the artificial cultivation of D.candidum should be born in 3 years no need to be more than 4 years.2.Studies on chlorophyll fluorescence of photosynthetic characteristics of D.candidum.in different habitat factor combination treatments Hight temperature（20.5℃）and low levels of light（7200 Lx²400 Lx）were good for improving the contents of chlorophyll a and chlorophyll b.When the relative humidity was 82.5%,the ETR_maxax and Ik of D.candidum higher,but When the relative humidity bellowed 62.5%,the growth of D.candidum was under stress.The test group B（light 21600 lx,daily average temperature of 20.5℃,daily average humidity of 72.5%,0.05%nutrient）and test group C（light 2400 lx,daily average temperature of 16.5℃,daily average humidity of 72.5%,0.1%nutrients）habitat factors in combination has improved the photosynthetic efficiency of D.candidum with higher content of chlorophyll and more optimized values of ETR_max,FV/Fm and Y（II）.3.Effets of growth characteristics of D.candidum.in different habitat factor combination treatments Plant height,stem diameter,leaf number,tiller number and biomass of D.candidum were different for treatments of different habitat factors.By the analysis of variance,effects of growth parameters of D.candidum were:temperature>light>relative humidity>nutrient.By using the biomass as reference index,the combination of habitat factors with high light（21600 Lx）,high temperature（20.5℃）,relative humidity（72.5%）and low nutrient（0.05%）can increase the biomass.4.Effets of total polysaccharides,alkaloids and flavonoids of D.candidum.in different habitat factors combined treatments Habitat factors of light,temperature,moisture and nutrients had significant effects on polysaccharides,flavonoids and alkaloids,and the effects were different.By the analysis of variance,lihgt had significant effects on the percentage content of total polysaccharides;temperature had effects on the percentage content total alkaloids and total flavonoids;relative humidity had great effects on content of total polysaccharides,total alkaloids and total flavonoids;the influence of nutrients to each component contents was not obvious.Total polysaccharide is the most critical standard for the quality evaluation of D.candidum,and light intensity are the most important factors.Test group A,with low light（2400Lx）,high temperature（20.5℃）,high humidity（82.5%）and high nutrient（0.2%）,is beneficial to the improvement of total polysaccharide in D.candidum.