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Theanine is an important quality parameter referring to tea quality. Applying N fertilizers is one strategy to improve the level of theanine, however, the effect of plant growth promoting rhizobacteria on theanine synthesis in tea roots has been less studied. In this study, the bacteria isolated form Qimen County with the maximum K solubilization were identified as Bacillus by biochemical and molecular analyses. We show that tartaric and pyruvic acids produced by Bacillus were important components related to K solubilization in vitro. Pot experiments and enzymatic assays in vitro showed that inoculation with Bacillus-secreted organic acids increased the level of available potassium in the soil. The increased K level activated recombinant CsTSI activity (theanine biosynthesis enzyme) and increased ethylamine content (the synthesis precursor of theanine), resulting in promoted theanine synthesis in tea roots. Therefore, our study indicates that Bacillus can be a potential bioinoculant for biofortification of tea.

K+ availability is important for growth and quality of tea (Camellia sine sis L.). K solubilising bacteria convert insoluble K to available K. This study was conducted to screen K solubilising bacteria isolated from tea rhizosphere soil in Qimen county, Anhui province, China. The maximum K solubilisation colony (the ratio of diameter halo/colony was 2.54) was identified as Burkholderia sp. (storage number: M2021105) by biochemistry and molecular analysis. Pot experiments (Laterite) showed that the inoculation of Burkholderia sp. significantly improved tea plant height (Zhongcha108, 1 year old) and total polyphenols content by 21.14% and 21.58% compared with the control, respectively. Higher polyphenol level promoted the formation of theaflavin in the fermentation experiments. Further experiments showed that tartaric acid and pryuvic acid produced by Burkholderia sp. are important components associated with K solubilisation in vitro. Burkholderia sp. significantly increased soil available K by 15.12%; however, there was no significant difference in available N and P, and Cu, Mg, Zn and Ca compared with the control. K content in inoculated tea roots and leaves was significantly higher (50% and 10%, respectively) than the control. Compared with the control, exogenous supply of 60 mg kg−1 K significantly increased levels of polyphenol (53.97%), theaflavin (16.31%), theaflavin-3-gallate (20%), theaflavin 3′-gallic acid ester (32.24%) and theaflavin 3,3′-gallic acid ester (40.95%). Due to its ability to enable higher available soil K, ur study indicated that Burkholderia sp. have potential to increase total polyphenols content be a bio-inoculant for biofortification of tea.

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Based on the experimental study of the gravel layer under the horizontal vibration load, and the variation of particles response behavior according to experimental phenomenon, we study the distribution of the shear along the depth direction, propose the main factors which affect particle moves and dynamic stiffness and their distribution in the granular packs. Then deduce the probability distribution model under horizontal vibration by the stochastic theory, and discuss the prediction method.