Leaf senescence is the last step of leaf development and can be induced by many genetic and environmental factors. The chloroplast and many leaf pigments undergo a progressive degeneration. The leaf functionality is slowed down and several physiological processes are altered. The chlorophyll a fluorescence and its derivate indexes can be used to monitor leaf senescence. The loss of leaf functionality is tightly correlated with the photosynthetic activity. The chlorophyll a fluorescence and its derived parameters can be suggested as tool to monitor the leaf senescence. Natural and induced senescence such as dark incubation, detachment, salinity stress, ethylene exposure, heavy metal stress etc. will be taken in consideration. The physiological, biochemical and molecular basis connected with the photosynthesis and chlorophyll fluorescence will be described and discussed.