1. Introduction
Potassium (K+) is a major nutrient required by higher plants
to complete their life cycle, its concentration surpassed only by
that of structural nutrients such as carbon, oxygen, hydrogen and
nitrogen [1]. K+ plays a relevant role as an osmoticum, and contributes
to the charge balance across the membranes as well as
to the proper activity of more than 50 enzymes [2–6]. Recent evidence
has demonstrated that the presence of functional inward
K+ transporters is required for the progression of the cell cycle
[7,8] and that a decrease in K+ concentration is necessary [9–11]
and sufficient [12] to induce a cell death program in cell walled
eukaryotic organisms. Moreover, K+ plays an alleviating role when
these organisms are faced with several abiotic stresses [13,14]. In
agreement with these pivotal functions, long-term K+ deprivation
leads to visible injuries which are preceded by physiological and
biochemical changes