Response Mechanisms Of Polysaccharide In Root Cell Wall Of Tea Plant(Camellia Sinensis L.)to Lead Stress

Tea is one of the most important economic crops in China.Pb is one of the most important indicators of its quality and safety monitoring. The relevant research suggests that Pb content in tea products has shown an increasing trend year by year. Recent research which was mostly focused on the resistance mechanism of plants to heavy metals was limited to short growing herbs. Reports on the study of woody plants to heavy metal stress are very rare. On the basis of these conditions, tea plant was selected as research subject. The objective of the present study is to find out the resistancemechanism of cell wall in tea plant rootsto Pb stress and also the inhibitionmechanismof root growth caused by Pb.Firstly we determine the difference in functional groups which can interact with Pb2+between different CW components as well as the adsorption ability of different CW components to Pb. Cellulose in the CW of plant roots has a greater ability to accumulate Pb as compared to pectin, Hemi-cellulose1and Hemi-cellulose2. The results of the adsorption kinetics study were indicatedthat the vast majority of Pb (68.42%) was adsorbed in the cellulose, followed by pectin (26.31%). Pb2+was fixed through interactions with functional groups like-OH and-COOH in pectin meanwhile the main functional groups in HC1and HC2was-COOH and-OH respectively. While it was found thatall these functional groups in cellulose were not fully responsible for Pb adsorption to CW. Combined with the cellulose’s physical structure which is porous and containinglarge specific surface area, it can beinferredthat the Pbwas adsorbedto CW mainlythrough the physical way.Pb2+stress on the CW of root brings a corresponding change in the CW polysaccharides. Our results showed that Pb2+increased the content of pectin, HC1and HC2. In addition,Pb stress increasedarabinose and galactose in pectin.