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Improving the extraction and purification of leaf and phloem sugars for oxygen isotope analyses
Author(s) -
Lehmann Marco M.,
Egli Melanie,
Brinkmann Nadine,
Werner Roland A.,
Saurer Matthias,
Kahmen Ansgar
Publication year - 2020
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.8854
Subject(s) - phloem , chemistry , sugar , sucrose , extraction (chemistry) , composition (language) , chromatography , fraction (chemistry) , botany , food science , biology , linguistics , philosophy
Rationale The oxygen isotopic composition (here shown as the δ 18 O value) of soluble sugars in leaves and phloem tissue holds valuable information about plant functions in response to climatic changes. However, δ 18 O analysis of sugars is prone to error, and thoroughly tested methods are lacking. Methods We performed three experiments to test if sample preparation modifies the δ 18 O values of sugars. In experiment 1, we tested the effects of oven‐drying versus freeze‐drying, whereas in experiment 2 we focused on the extraction and purification of leaf sugars. In experiment 3, we investigated the exudation and purification of twig phloem sugars as a function of exudation time and different ethylenediaminetetraacetic acid (EDTA) exudation media. Results Freeze‐drying produced more consistent δ 18 O values than oven‐drying for sucrose but not for phloem sugars. The extraction and purification of leaf sugars can be performed without a significant modification of their δ 18 O values; yet the purified leaf and phloem sugars possessed higher δ 18 O values than the fraction of water‐soluble compounds. Moreover, the exudation time significantly modulated the δ 18 O values of phloem sugars, which is probably related to changes in the sugar composition. The addition of EDTA did not improve the determination of the δ 18 O values of phloem sugars. Conclusions We show that the sample preparation of plant sugars for the reliable determination of δ 18 O values requires a strict protocol, which is described in this paper. For phloem sugar, we recommend a maximum exudation time of 1 h to reduce the degradation of sucrose and minimise oxygen isotope exchange reactions between the resulting hexoses and water.