Distribution of molecules in plant tissue can provide an understanding of spatial metabolomics, plant-environment interactions, and aid compound screening. For example, location information of medically important compounds within a plant will strengthen fundamental understanding of their metabolic origins, as well as, improve their extraction. Mass spectrometry (MS) imaging provides a spatial distribution of a large variety of endogenous and exogenous analytes from plant surfaces without sample extraction or addition of any external label. Molecular images provided by MS are complementary to the structural information provided by optical microscopy.
Here, we share workflow for imaging of plant tissue using matrix-assisted laser desorption ionization (MALDI) or desorption electrospray ionization (DESI). As an example of a workflow, MS imaging was utilized to find molecular markers after mechanical stress in a plant, which is a typical problem throughout their life cycle. MS imaging of a leaf with mechanical damage showed localized molecules near the site of the tears that can shed insight into the protective wound-healing mechanism.