Multiple reaction monitoring mass spectrometry is a powerful tool to study glycerolipid composition in plants with different level of desaturase activity.

In plants, two lipid desaturation pathways exist. A so-called prokaryotic pathway is active in plastids and responsible for unsaturation of 16 carbon fatty acids. An eukaryotic one, in the endoplasmic reticulum, acts on 18 carbon fatty acids. Desaturase activities are affected in stressed plants, and conversely, they have an impact on the capability of plants to adapt to stress. So knowing lipid unsaturation is important for physiological studies. Analysis of lipids by mass spectrometry, in the multiple reaction mode, gives access to the molecular species present in each membrane lipid class. We illustrate the powerfulness of this technique by applying it to phospholipids and galactolipids extracted from plants where the desaturation pathways are present at variable level.