New evidence for the molecular–chemical diversity of potato plant rhizodeposits obtained by pyrolysis–field Ionisation mass spectrometry

Abstract

Detailed descriptions of the molecular-chemical diversity in plant rhizodeposits are scarce. The vast majority of our knowledge is derived from a priori methods of analysis, such as GC-MS and HPLC. To analyse the composition of rhizodeposits from the potato cultivar Solanum tuberosum L. cv. Albatros by pyrolysis -field ionisation mass spectrometry (Py-FIMS) and to explain differences in relation to plant growth stage and photoperiod. Potato (Solanum tuberosum L.) plants were grown in non-sterile, native soil under controlled environmental conditions (plant chamber). Rhizodeposit samples were collected by leaching during two different growth stages and after the physiological day- and night-cycle. All leachate samples were investigated by Py-FIMS. Mass spectrometric data were evaluated by multivariate statistics. Screening of the rhizodeposits by Py-FIMS revealed a broad range of m/z signals. Low-molecular-weight substances of m/z 15-56 (8.1-18.6%), alkylaromatics (12.0-15.9%), phenols and lignin monomers (8.8-13.1%) and carbohydrates (6.0-11.2%) comprised the largest proportions of total ion intensity (TII). Mass signals with significantly different abundance at the various sampling dates were assigned to compound classes of carbohydrates, phenols and lignin monomers, lignin dimers, lipids, N-containing compounds, sterols, peptides and free fatty acids; these were supplemented by marker signals for N-acetylmuramic acid from bacterial cell walls and signal molecules for the regulation of secondary pathways such as 4-hydroxycinnamic acid and linolenic acid. Py-FIMS was well suited to detect the molecular-chemical diversity of potato plant rhizodeposits and, compared with traditional a priori analytical methods, provided detailed evidence for significant differences in the composition of rhizodeposits depending on growth stage and diurnal period.