This opinion was concluded from in vitro experiments. In addition, Fe deficiency induced a decline of maximum potential PSII efficiency (Fv/Fm) of peach leaves (Eichert et al., 2010).
Plant vitality could be characterized by performance index (PI); PI reflects the functionality of both photosystems I and II and is a sensitive indicator of photosynthesis (Strasser et al., 2000, 2004).