Specificity of Ion Uptake and Homeostasis Maintenance During Acid and Aluminium Stresses

Abstract

AbstractLow pH (proton toxicity) and aluminium toxicity coexist in acid soils, affecting plant growth worldwide. Decades of research concluded that proton and aluminium toxicity mechanisms are complex and remain unclear. Among the Al tolerance mechanisms, exudation of organic acid anions received considerable attention, leading to the identification of novel genes involved in organic acid anion metabolism and transport. As a downside, the major focus on exudation of organic acid anions has overshadowed research on other potential Al tolerance mechanisms (e.g. reduced cell wall binding, rhizosphere alkalisation, phosphate exudation, enhanced uptake of essential nutrients) that may be operating. In this work, the current knowledge on how proton and aluminium toxicity and tolerance mechanisms are operating when plants are exposed to acid soils is reviewed. Special emphasis has been given to the question of how uptake and homeostasis of hydrogen, potassium, phosphorus, calcium, and magnesium ions in plants are affected and regulated during low-pH and aluminium stresses. There is enough evidence to suggest that low-pH and combined low-pH/aluminium stresses differentially affect root tissues and, consequently, the rhizosphere. Less disturbed phosphorus, calcium, and magnesium uptake and homeostasis maintenance help plants to cope with low-pH and combined low-pH/aluminium stresses.KeywordsH+ fluxesK+ fluxesCa2+ fluxesMg2+ fluxesIon homeostasisCytoplasmic pHCytoplasmic Ca2+ Cytoplasmic Mg2+