The Sodium and Potassium Balance in Plants: The Dose Makes the Poison

Authors

  • José M. Pardo Inst. Bioquímica Vegetal y Fotosíntesis, CSIC-Universidad de Sevilla

DOI:

https://doi.org/10.24310/enbio.17.192.2025.22852

Keywords:

sodium, potassium, salinity, nutrition, plants

Abstract

Although sodium (Na) and potassium (K) have similar abundances in the Earth’s crust, all living

organisms preferentially accumulate K within their cells while avoiding high levels of Na. In plants, Na toxicity is the

main harmful effect of salinity. To counteract this, plants possess a network of ion transporters, among which the SOS

(Salt Overly Sensitive) pathway stands out for its functional importance. This pathway promotes Na extrusion from

root cells into the medium or its loading into the xylem, allowing proper Na distribution to the shoots and dilution

through growth. Potassium uptake, on the other hand, relies on a complex and redundant system of ion transporters

that ensures adequate nutrition under widely varying K availability, often capturing all available K from the medium.

However, this strong affinity for K can lead to toxicity when uptake becomes uncoupled from its tissue distribution

or vacuolar storage. Furthermore, under K deficiency, many plants actively accumulate Na to substitute for K in

osmoregulatory functions. Thus, the distinction between nutrient and toxin becomes blurred, recalling Paracelsus’s

principle that “the dose makes the poison”.

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References

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Published

2026-01-24

Dimensions

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How to Cite

The Sodium and Potassium Balance in Plants: The Dose Makes the Poison. (2026). Encuentros En La Biología, 17(192), 28-30. https://doi.org/10.24310/enbio.17.192.2025.22852