Effects of Carbohydrate Components of Fungus S7 on Seed Germination of Dendrobium officinale
OBJECTIVE To investigate the effects of carbohydrate components of fungus S7(Tulasnella sp.)on seed germina-tion of Dendrobium ofiicinale.METHODS The polysaccharides of S7 mycelia(MP)and of S7 fermentation broth(FP)were pre-pared by water extraction and alcohol precipitation.MP and FP were hydrolyzed by trifluoroacetic acid to obtain hydrolysates,MPH and FPH.The monosaccharide composition of MP and FP were determined by PMP-HPLC.MP,FP,MPH,FPH,and the unique and mixed monosaccharide of MP were added to water agar(WA)and 1/2 MS media respectively to study the effects of carbohydrate on the seed germination of Dendrobium officinale.RESULTS The germination rate of WA medium group(WACK1)was(88.65± 4.71)%,and seeds germinated to stage 3(protocorm).Compared with WACK1,adding MP and MPH had no significant effect on germination rate(P>0.05),and seeds could germinate to stage 4(having one leaf),while adding FPH could significantly reduce germination rate(P<0.05).MP was composed of glucose,galactose,glucuronic acid,xylose,mannose,fucose,ribose and arabi-nose in a molar ratio of 15.05∶1.00∶0.70∶0.35∶0.30∶0.29∶0.13∶0.13.FP was composed of arabinose,galactose,xylose and glucu-ronic acid in a molar ration of 1.22∶1.00∶0.71∶0.47.Fucose was the unique monosaccharide component of MP.The germination rate and stage 5(having two leaves)germination rate of 1/2 MS medium group(MSCK)was(98.10±0.46)%and(50.97±4.33)%,respectively.Compared with MSCK,adding 0.20-20 mg·L-1 fucose had no significant effect on germination rate(P>0.05),while significantly increased stage 5 germination rate(P<0.05),which was 1.36-1.47 times that of MSCK.CONCLUSION MP and MPH promote the development of protocorm of D.officinale.Fucose is an active component in MPH that could promote the further dif-ferentiation and development of seeds after germination.