Accumulation Of Chemical Components Related To Taste And Analysis Of Lignin Monomer Types In Stems Of Dendrobium Officinale

Dendrobium officinale Kimura et Migo belongs to Dendrobium of orchidaceae,a perennial herbaceous plant,is a traditional Chinese medicine.The amount of"the dregs of chewing"in the stems of Dendrobium officinale,which is the homology of medicine and food,is an important evidence for civil evaluation of the quality of Dendrobium.In this study,the stems of D.officinale in different years(one year,two years,three years)were used as materials.The distribution and the contents changes of chemical components in the stems of D.officinale were studied,and the multiple linear regression analysis was conducted of them.Meanwhile,the correlation of polysaccharides and lignin metabolism related enzymes gene expression levels of D.officinale was analyzed.Furthermore,the m(?)ule staining and FTIR and ~1H-NMR techniques were used to analyze and identify the types of lignin monomers in D.officinale stems.These results provided important references for further study on soluble polysaccharides accumulation,quality detection and the harvesting and processing of D.officinale stems.The main results are as follows:1.The polysaccharides in D.officinale stems were stored in parenchyma cells with granular form,which had relatively high levels in two years.The lignin and cellulose were distributed in vascular bundles in D.officinale stems.With the increase of years,the thickness vascular thick-walled cells were increased of D.officinale stems,the lignin staining was deeper,and the lignification degree increased.2.The contents of polysaccharides,mannose and glucose of D.officinale showed a trend of increasing first and then decreasing with the increase of years,the contents in two years was the highest.And the ratio of mannose to glucose decreased with the increase of years.The polysaccharides contents(37.03%),mannose contents(30.28%)and the ratio of mannose to glucose(4.52)in two years were in line with the range prescribed by pharmacopoeia.The main compositions in residue of D.officinale stems were lignin and cellulose.The contents of lignin increased with the increase of years.It had no had no significant difference in stems of one year and two years,but increased significantly in stems of three years.The contents of cellulose increased first and then decreased with the increase of years.3.The accumulation of lignin displayed significantly negative correlation with the contents of polysaccharides,mannose,and the ratio of mannose to glucose,respectively.These results suggest that the accumulation of polysaccharides was influenced by the deposition of lignin that lignin is an important factor to affecting the taste and quality of D.officinale.It is suggested to harvest the stems of D.officinale in two years for fresh food and processing materials.4.The polysaccharides contents were negatively correlated with the expression levels of glucose catabolism related genes(Do MAN、Do DHAPS)and lignin anabolism related genes(Do C3H、Do4CL、Do CCR).The mannose contents were negatively correlated with the expression levels of glucose catabolism related genes(Do MAN、Do G6PDH)and lignin anabolism related genes(Do4CL、Do CCR).The lignin contents was positively correlated with the expression levels of glucose catabolism related genes(Do G6PDH)and lignin anabolism related genes(Do4CL、Do CCR).And the expression levels of Do G6PDH,Do4CL and Do CCR were negatively correlated with polysaccharides accumulation,and positively correlated with lignin deposition.5.The stems of D.officinale mainly contained guaiacyl lignins(G lignin)and syringyl lignin(S lignin),as well as trace hydroxyl-phenyl lignins(H lignin).Meanwhile,there are three major chemical bonding types in the lignin of D.officinale stems,includingβ-5,β-O-4 andβ-β.G lignin were mainly distributed in the xylem of the vascular bundle of the stems,while S lignin were mainly distributed in the thick-wall cells of the vascular bundle sheath.The S/G ratio in stems of D.officinale was on the rise with years increasing.The lignin contents was positively correlated with S%and S/G in stems of D.officinale,and the ratio of mannose to glucose was significantly negatively correlated with S%and S/G.