Studies On The Protocorm-like Bodies Of Dendrobium Candidum Under Suspension Culture

Dendrobium candidum Wall. ex Lindl has long been used as precious herb in traditional Chinese medicine in our country because of its ageing-resistance and ability to improve the immunity of human body. Now, D. candium has been enlisted as the rare and endangered plant species because of excessive collection of wild resources. The protocorm-like bodies(PLBs) of D.candium has the same physiological and biochemical metabolisms and morphogenesis as that of original plant, therefore which would be an alternative to wild resources of D. candium in the future.In this research, the seed-derived PLBs of D. candium were used as materials to optimize the protocol for PLBs culture through comparing the modes of liquid and solid cultures on the biomass and polysaccharides accumulation within PLBs, in addition, the effects of light intensity and Ca on PLBs growth were also investigated. The results are as follows:1. Liquid suspension culture was proved to be favorable for PLBs growth and polysaccharide accumulation, and its multiplication coefficient was1.5times that of solid culture. More important, the PLBs still remain strong abilities to proliferate and differentiate after transferred to solid medium from liquid-culture, and abnormal seedlings originated from the PLBs under liquid culture were not found.2. The optimal formula for PLBs growth and polysaccharide accumulation was:N6+1.0mg/LNAA+1.0mg/LKT, containing5%banana extract+5%potato extract, and40g/L of inoculums.3. The growth curve of PLBs displays a "S" type during the whole period of suspension culture, and polysaccharide contents declined at the early stage of culture, and then increased, however was reduced again at the late stage of culture. After30days of culture, the fresh weight arrived at its maximum of122.9g/L, then some PLBs became aging and even led to death, and the maximum polysaccharide content was up to24.2%by the25th day of culture.4. The best light intensity for growth of PLBs is15001x,stronger or weaker illumination were both unfavorable for PLBs culture. The maximum fresh weight, polysaccharide content were120.75mg/L and24.6%by the25th day, respectively, and the maximum soluble protein content was4.85mg/g by the20th day of culture, and chlorophyll content and chlorophyll a/b also maintained normal level. The chlorophyll content and chlorophyll a/b decreased in low light, and it was worth noting that chlorophyll content was reduced at high light at the late stage of culture.5. Addition of3.0mmol/L Ca2+into the culture, the maximum fresh weight and polysaccharide content were achieved by140.57g/L and25.9%,respectively, and the soluble protein content was up to5.31mg/g, and it was also tested to be suitable for chlorophyll biosynthesis in this case.