Effect of root zone pH and form and concentration of nitrogen on accumulation of quality-related components in green tea
Green tea quality is greatly influenced by concentrations of free amino acids, polyphenols (mainly catechins) and caffeine. The present study investigated the principal relationship between selected nutritional factors (form and concentration of N supply, root zone pH) and accumulation of these qual...
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Published in | Journal of the science of food and agriculture Vol. 87; no. 8; pp. 1505 - 1516 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Chichester, UK
John Wiley & Sons, Ltd
01.06.2007
Wiley John Wiley and Sons, Limited |
Subjects | |
Online Access | Get full text |
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Summary: | Green tea quality is greatly influenced by concentrations of free amino acids, polyphenols (mainly catechins) and caffeine. The present study investigated the principal relationship between selected nutritional factors (form and concentration of N supply, root zone pH) and accumulation of these quality‐related components of tea (Camellia sinensis (L.)) plants. Tea plants were hydroponically cultured with NH$_{4}^{+}$, NO$_{3}^{-}$ and NH$_{4}^{+} +$ NO$_{3}^{-}$ at pH 4.0, 5.0 and 6.0 in one experiment and supplied with varying N concentrations (0.75, 2.0 and 4.5 mmol L−1, NH$_{4}^{+}$/NO−3 = 3:1) in another experiment. Concentrations of free amino acids were considerably higher in NH$_{4}^{+}$‐ than in NO$_{3}^{-}$‐fed plants. This was attributed to the much greater absorption of NH$_{4}^{+}$ compared with NO$_{3}^{-}$. Furthermore, the relative allocation of absorbed N to free amino acids, particularly theanine and glutamine, was substantially increased by NH$_{4}^{+}$ nutrition, suggesting that NH$_{4}^{+}$ was more readily assimilated than NO$_{3}^{-}$ into theanine. The concentration of caffeine was increased in NH$_{4}^{+}$‐ and (NH$_{4}^{+} +$ NO$_{3}^{-}$)‐supplied plants, whereas concentrations of catechins were reduced in (NH$_{4}^{+} +$ NO$_{3}^{-}$)‐fed plants. Root zone pH did not influence concentrations of most free amino acids in young shoots, with the exception of theanine, which increased at low pH (4.0) irrespective of N form; this likely stemmed from an accumulation effect, as growth decreased more strongly than N absorption. Raising the N supply increased plant N allocation to free amino acids. The increase was most striking for arginine, while theanine was only marginally affected. This may have adverse consequences for green tea quality, as less favourable taste characteristics have been attributed to arginine. Copyright © 2007 Society of Chemical Industry |
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Bibliography: | ark:/67375/WNG-BB23QLHR-H German Research Foundation - No. DFG Sa 359/22 ArticleID:JSFA2875 Dedicated to Professor Dr B Sattelmacher, who passed away on 21 November 2005 during the preparation of this paper istex:E4ED2DA20B16CF65EB9D0E38DF3F72D14BDFAA88 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0022-5142 1097-0010 |
DOI: | 10.1002/jsfa.2875 |