Physiological and molecular responses to magnesium nutritional imbalance in plants

Background Magnesium (Mg) is pivotal for many biochemical and physiological processes in plants. Mg biological functions include a key role in photosynthesis, in protein synthesis, as well as in nucleotide metabolism. However, Mg nutrition of plants remains little examined compared with other essential elements. Scope The review summarizes the current knowledge on physiological targets of Mg imbalances. Recently generated transcriptome profiles in response to Mg shortage and excess are also presented. Conclusions Sugar accumulation in source leaves is a major consequence of Mg shortage that can limit plant growth most probably by down regulation of photosynthesis activity. Newly identified molecular targets of Mg imbalance are appraised in relation to their potential contribution to Mg deficiency phenotypic emergence. In particular a potential role of the circadian clock and change in phytohormones concentration and/or signalling in the orchestration of the Mg deficiency response is possible. The development of markers for incipient Mg deficiency appears to be a challenging task.