RESUMEN
Calcium is an essential element for plants' survival and ability to deal with environmental stresses. However, it can cause cell death due to cellular disequilibrium. Serpentine plants are sensitive to high concentrations of Ca2+, which induces lethal symptoms, especially under environmental stress. In this study, the direct effects of Ca2+ on cell death were investigated in cell cultures of Alyssum inflatum, a serpentine plant native to Western Iran, and results were compared to a non-serpentinitic congeneric species A. saxatile. The results were also compared to the effects of Mg2+ treatments in both species, as another determinative factor in serpentinite soil is high Mg2+ content. Plasma membrane permeability, reactive oxygen species (ROS), and malondialdehyde (MDA) production were measured as physiological cell injury indices. In A. inflatum higher levels of ROS and MDA were observed in Ca2+-treated cells (5 mM or more), while in A. saxatile they were measured in Mg2+-treated cells (5 mM or more). In serpentine species, results indicated that cell death by Ca2+ was more intensive than the cell death by Mg2+, which were observed with less intensity in non-serpentine plants. Microscopic studies showed that cell death occurred via apoptosis-like programmed cell death (AL-PCD). Therefore, Ca2+ sensitivity and AL-PCD as mechanistic reasons for their non-serpentine intolerance would be a crucial consideration in cellular researches concerning serpentine plants, which could be employed in green technologies such as phytoremediation.