Microchemical analysis of laser-microdissected stone cells of Norway spruce by cryogenic nuclear magnetic resonance spectroscopy.
Stone cells (sclereids) in Norway spruce (Picea abies) bark have been reported to be highly lignified tissues that are important in physical defence against bark beetle invasion. Microchemical analyses of the low-molecular weight compounds in the stone cells of Norway spruce were carried out using laser microdissection in combination with cryogenic nuclear magnetic resonance and mass spectrometry (LMD/NMR/MS). Two phenolic compounds, the stilbene astringin and the dihydroflavonol dihydroxyquercetin 3'-O-beta-D-glucopyranoside, were identified indicating that stone cells are more than just repositories for lignin. Both of these compounds were also found to be present in other phloem tissue at a higher level than in the stone cells based on quantification by cryogenic 1H NMR. Our results suggest that stone cells may be involved in chemical as well as physical defense against bark beetles and their associated microorganisms. This paper reports on the identification of secondary plant metabolites from a single laser-microdissected population of plant cells offering a sensitive new way to determine the chemical profile of specific plant cell types with a high degree of precision.