This dissertation describes a variety of plant studies by laser ablation electrospray ionization mass spectrometry imaging. (LAESI MSI). During the LAESI process, a plant sample is ablated when a laser is fired at it. The resultant neutral plume is ionized and enters the mass spectrometer by an electrospray stream. In all experiments an ultraviolet (UV; 355 Nd:YAG) laser was used. Once ions enter the mass spectrometer and are detected, a spectrum is produced for a particular area on the plant. The rest of the plant is ablated and spectra are combined for image creation.

Unlike other forms of mass spectrometry, MSI allows for chemical and spatial information which can help understand the diversity of plants, where one cell may contain different chemicals compared to its neighboring cell. Plants studied in this dissertation included peonies, coleus, and Arabidopsis thaliana. A variety of metabolites were imaged, including flavonoids, anthocyanins and lipids. Analyte images allowed further insight into biological processes, such as the malonylshisonin pathway in coleus leaves, and effects of lipids during autophagy in Arabidopsis thaliana. LAESI MSI was also shown in this dissertation to be a potentially faster more sensitive technique than other forms of mass spectrometry.