Journal of Food, Agriculture and Environment

Bioactive ingredient levels of tea leaves are associated with leaf Al level interactively influenced by acid rain intensity and soil Al supply

Author(s):

Xiaohua Duan ^{1, 2}, Xiaofei Hu ³, Fusheng Chen ³, Zeyuan Deng ¹*

Recieved Date: 2012-07-04, Accepted Date: 2012-10-02

Abstract:

The present study aimed to investigate the effects of acid rain (pH 3.0, 4.5 and 6.0) and soil available  aluminium  (Al) levels (adding  0,  0.5  and  1.0 g kg^-1 Al into soil in the form of Al₂(SO₄)₃ solution) on Al cycling in soil-tea plant continuum and the levels of main bioactive ingredients of tea leaves using a pot experiment. Five Al forms in soil were extracted using a sequential extraction procedure, and the Al contents were determined by the inductively coupled plasma-atomic emission spectrometry (ICP-AES). Tea polyphenols, caffeine and amino acids were determined by methods of ferric tartrate, lead acetate precipitation, and ninhydrin colorimetry, respectively, and flavonoids were measured with aluminium chloride colorimetric assay. Two forms of easily absorbable Al including exchangeable Al (E-Al) and organic Al complexes (O-Al) showed higher contents in rhizosphere soil than in bulk soil and their contents in rhizosphere and bulk soils were higher for treatments of simulated acid rains at pH 4.5 and pH 3.0 than for irrigation with normal water at pH 6.0, and higher for treatments added with Al 0.5 and 1.0 g kg^-1 in soil than without Al addition. Al assimilation and accumulation in plants were slightly promoted by acid rain with addition of 0.5 g kg^-1 Al in soil, while inhibited with addition of 1.0 g kg^-1 Al in soil. Al levels in tea shoots, leaves and roots were higher in the treatments with elevated Al level than without Al addition. The contents of tea polyphenols, caffeine and amino acids in tea leaves were higher at pH 4.5 in comparison to the other two pH values, and they increased with increasing Al supply. However, the contents of tea polyphenols, caffeine and amino acids in tea leaves were highest at the leaf Al content of 7~8 mg g^-1. It is therefore concluded that the amount of bioactive ingredients in tea leaves is closely related to leaf Al level, which is interactively influenced by acid rain intensity and soil Al supply. It is feasible to produce tea with reasonable quantity of the bioactive ingredients and a safe Al level by adjusting the acidity and contents of Al in soil. 

Keywords:

Acid rain, Al level, hilly red soil, tea quality

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Journal: Journal of Food, Agriculture and Environment
Year: 2012
Volume: 10
Issue: 3&4
Category: Environment
Pages: 1197-1204

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