Research On Cold Resistance Characteristics Of Dendrobium Officinale And Related Bacteria

Dendrobium officinale Kimura et Migo is a rare traditional Chinese medicinal herb.With favored health benefits,more and more of its products were required.Therefore,imitation wild cultivation and cultivation in the North of China are developing quickly.Therefore,cold resistance lines of D.officinale are urgently needed.In this paper,two lines including cold resistance and cold irresistance were used to investigate the characteristics and mechansim of D.officinale resisting against cold.Firstly,the characteristics of the seedlings resisting against cold was investigated under artificial simulation of low temperature.As the results,the cold resistance Line MG1 resisted against-2? for 3d and against-7? for 32h.Treated under these low temperatures,the seedlings kept active and continued growing under normal conditions.However,the cold irresistance Line MG2 resisted agaist only-2? for 2d and against-7? for 8h.Otherwise,the seedlings lost the active and died.Next,the cold resistance and cold irresistance lines were cultived in different districts to investigate their resistance against coldness.As the result,the cold resistance Line MG1 in Huzhou showed the best height,stem diameter,and leaf thickness.At the same time,the thickness of sponge tissue,grid organization,and the membrance on the stem were higher in Line MG1 than those in Line MG2.As the resistant activity is concerned,the contents of MDA and Electroconductivity were lower in Line MG1 than those in Line MG2.For the water content ratio.the value in Line MG 1 was lower than that in Line MG2,indicating that higher water content ratio is harmful to cold resistance.However,the contents of proline and soluble sugar showed higher in Line MG 1 than that in Line MG2,which indicated that these molecules benefit for the cold resistance.According to the results of antioxidase,Line MG1 had higher activities of SOD than Line MG2 did.However,activites of CAT and POD in samples of Zhengzhou were higher than those in Huzhou.For the second metabolic products,the polysaccharide and alkaloids presented higher content in Line MG I than that in Line MG2.The content offlavonoids was higher in MG I of Zhengzhou than that in Huzhou.Thirdly,the bacterial communities for the cold resistance and cold irresistance lines cultived in different districts were investigated.Based on sequencing of 16S rRNA genes,the dorminant bacterial phylum was Proteobacteria,followed by Acidobacteria,Actinobacteria,Bacteroidetes and Verrucomicrobia.The dominat genus included Exiguobacterium(11.46%)and Buttiauxella(11.23%)in Line MG1 than that in Line MG2 Actinoplanes(4.98%)and Novosphingobium(6.32%).These specific genera in Line MG1 might play some roles on the cold resistance,which need further evidence.In conclusion,Line MG1 of D.officinale resist well agaisnt stress of low temperature.The possible mechanism agaist cold include the structure of leave,root and membrance,the content of osmotic regulatory molecules such as molecules,activies of SOD,CAT and POD,as well as contents of the polysaccharide,flavonoids,and alkaloids.In addition,some bacteria might also contribute to cold resistance.These results provide foundation for breeding excellent lines of cold resistance and also for novel cultivation technology against low temperature.