Water-soluble phenolic metabolites in lichens and their potential role in soil organic matter formation at the pre-vascular stageстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 8 сентября 2020 г.
Аннотация:Soil organic matter (SOM) is the largest reservoir of organic carbon in the biosphere. However, little is known about the processes of its formation at the prevascular stage. Lichens are among the pioneer colonizers on mineral substrates and are possible early land flora. This study is the first report on the identification and quantification of water-soluble phenolic compounds (PCs), potential precursors of humic substances, in epigeyic lichens from two systematic groups. Results show
(Folin–Denis assay) that cyanobiont-containing lichens (order Peltigerales) possess
three to five times more total soluble PCs than Lecanoralean lichens (Cladonia,
Cetraria spp.) and mosses. Soluble PCs in lichens occur in the conjugated form.
Alkali-hydrolysable compounds (esters) predominate over acid-hydrolysable ones
(glycosides). Phenolic complexes with N-containing compounds or reducing
sugars, or both, have been identified by thin layer chromatography (TLC). Benzoic
acid derivatives were most common among PCs, detected in lichens by reversedphase high-pressure liquid chromatography (RP-HPLC). Phenolic acids occur in the order (μg 100 g−1
): p-hydroxybenzoic (327–1,007) > syringic (87–361) > salycilic (135–210) > vanillic acid (12–19) (Peltigeralean lichens); salicylic (53–102) > p-hydroxybenzoic (45–54) > caffeic (29) > syringic (18) > vanillic acid (9–13) (Lecanoralean lichens). Protocatechuic, caffeic and p-coumaric acids
were rare; ferulic acid was not detected. Syringyl and vanillyl aldehydes and
ketones occur in much larger amounts than acids. Methoxy-substituted and orthosubstituted phenols, detected in lichens, are known for their high reactivity in soils
under lignified vegetation, suggesting their important roles in SOM formation
under a cryptogam cover.