Morphological Analysis And Theanine Metabolic Mechanism Of Grafted Plants Between Camellia Sinensis (L.) O.Kuntze And Camellia Oleifera Abel

Theanine,a typical free amino acid in tea,has a great impact on the tea quality,which was rarely reported in other plants.Its unique pharmacological and health promoting effects attracted a great deal of attention.However,the metabolic regulatory mechanism and specific biosynthetic tissues or organs in tea plants has not yet been studied well.In this study,grafted plants with Camellia sinensis as scions and Camellia oleifera as stocks were established by crown and root grafting.The leaf anatomical morphology analysis of scions(Camellia sinensis),grafted plants and stocks(Camellia oleifera)was detected by paraffin section and the relationship of three kinds of leaves was used to analyze by PCA.HPLC method was used to detect the content and composition of amino acids among scions(Camellia sinensis),the graft plants and stocks(Camellia oleifera)leaves.According to the results,we found the significant function of Camellia sinensis roots on the biosynthesis and accumulation of theanine.In order to carry out further research of theanine metabolism,Camellia sinensis and Camellia oleifera were hypocotyl grafted reciprocally,and self-graftings between Camellia sinensis and Camellia oleifera were carried out as controls.Four grafted plants:Camellia sinensis/Camellia oleifera,Camellia oleifera/Camellia sinensis,Camellia sinensis/Camellia sinensis,Camellia oleifera/Camellia oleifera were established,respectively.Likewise,HPLC method was used to detect the content and composition of amino acids in young leaves,mature leaves,stems and roots of the four grafted plants.Besides,the biosynthetic activity of theanine in leaves,stems and roots of the four grafted plants were studied by tracer experiment using 15N-ethylamine hydrochloride.It showed that the leaves and stems of grafted seedlings Camellia oleiferal Camellia sinensis and Camellia sinensis/Camellia sinensis,whose stocks were Camellia sinensis,contained high content theanine.However,theanine was almost not detected in grafted seedlings Camellia sinensis/Camellia oleifera and Camellia oleifera/Camellia oleifera,whose stocks were Camellia oleifera.Biosynthetic activity of theanine was investigated by isotopic tracer experiment.It was convinced that leaves,stems and roots in the four grafted plants except leaves of grafted seedling Camellia oleifera/Camellia oleifera were able to synthesize theanine.The biosynthetic activity of theanine in the roots of grafted seeding Camellia sinensis/Camellia sinensis occupied the first place,the roots of grafted seeding Camellia oleifera/Camellia sinensis comes second.The results showed that the leaves of grafted plant Camellia sinensis/Camellia oleifera were closer to scions(Camellia sinensis)in anatomical morphologically and somehow influenced by its stocks(Camellia oleifera).Graft changed content and composition of amino acids in the grafted plants.The leaves,stems,roots of Camellia sinensis were able to synthesize theanine,and roots were the main part for theanine biosynthesis.Moreover,some of theanine was accumulated in roots and the rest was transported to leaves by stems.It is noteworthy that Camellia oleifera didn't accumulate theanine although the stems,roots had weaker capability to synthesize theanine.In this study,grafting between Camellia sinensis and Camella oleifera reciprocally was carried.The grafted plants benefit germplasm innovation.Furthermore,the grafted plants provide ideal materials to study the metabolic mechanism of theanine.