title: Occurrence of interactions between individual Sr²⁺- and Ca²⁺-effects on maize root and shoot growth and Sr²⁺, Ca²⁺ and Mg²⁺ contents, and membrane potential: consequences on predicting Sr²⁺-impact.
abstract: Occurrence of functional interactions between Sr(2+) and Ca(2+) were investigated on maize plants grown under hydroponic conditions in presence of various mixtures of SrCl2 [0-0.01-1-10 mM] and CaCl₂ [0-0.2-2-20 mM]. External [Ca(2+)] modulated the effect of Sr(2+) on the plant dry weight, and on the Sr(2+), Ca(2+) and Mg(2+) contents of roots and shoots. An intermediary functional step between external [Sr(2+)] and [Ca(2+)], and organ ion content, occurred at the plasma membrane of cortical root cells where Sr(2+) and Ca(2+) could influence ion uptake by acting on membrane potential. The decrease of the Sr(2+)-evoked membrane depolarization induced by Ca(2+) could not solely be attributed to the Ca(2+)-effect on the resting membrane potential. Most of the time the individual effects of Sr(2+) and Ca(2+) were not additive, as these two ions clearly interacted with each other to jointly affect the plant physiology. In spite of these interactions, both [Sr(2+)](ext) or [Sr(2+)](ext)/[Ca(2+)](ext) ratio values seemed to enable a correct prediction of the Sr(2+)-effects on the plant. However using the [Sr(2+)](ext)/[Ca(2+)](ext) ratio improved significantly the adequacy of prediction compared to the use of [Sr(2+)](ext) alone, as it increased up to 25% the proportion of variability accounted for by the model.
authors.affiliation: Laboratoire de Chrono-Environnement UMR6249, Université de Franche-Comté, Place Leclerc, 25000 Besançon, France. christelle.moyen@univ-fcomte.fr
authors.forename: Christelle
authors.initials: C
authors.lastname: Moyen
authors.forename: Gabriel
authors.initials: G
authors.lastname: Roblin
mesh_terms: D000704:Analysis of Variance; D001673:Biodegradation, Environmental; D002118:Calcium / Q000032:analysis* / Q000737:chemistry; D002462:Cell Membrane / Q000187:drug effects; D007477:Ions; D008274:Magnesium / Q000032:analysis* / Q000737:chemistry; D008564:Membrane Potentials / Q000187:drug effects*; D008670:Metals; D018517:Plant Roots / Q000187:drug effects*; D018520:Plant Shoots / Q000187:drug effects*; D025341:Principal Component Analysis; D012044:Regression Analysis; D012989:Soil Pollutants; D013054:Spectrophotometry, Atomic; D013324:Strontium / Q000032:analysis* / Q000737:chemistry; D013997:Time Factors; D003313:Zea mays / Q000187:drug effects*
chemical_list: D007477:Ions; D008670:Metals; D012989:Soil Pollutants; D008274:Magnesium; D002118:Calcium; D013324:Strontium
keywords: Ion uptake and translocation; Membrane potential (ΔΨ); Metal contaminant; Strontium/calcium interactions; Zea mays growth