Linear relationships between shoot magnesium and calcium concentrations among angiosperm species are associated with cell wall chemistry

Abstract

This article argues that, in plants that do not exhibit 'luxury' accumulation of Mg or Ca, (1) distinct stoichiometric relationships between [Mg]shoot and [Ca]shoot are exhibited by at least three groups of angiosperm species, namely commelinid monocots, eudicots excluding Caryophyllales, and Caryophyllales species; (2) these relationships are determined by cell wall chemistry and the Mg/Ca mass quotients in their cell walls; (3) differences between species in [Mg]shoot and [Ca]shoot within each group are associated with differences in the cation exchange capacity (CEC) of the cell walls of different species; and (4) Caryophyllales constitutively accumulate more Mg in their vacuoles than other angiosperm species when grown without a supra-sufficient Mg supply.

Variation in the angiosperm ionome

“…Commelinid monocots also have smaller leaf Mg concentrations than other angiosperms and this has been attributed to the same structural origin (Fig. ; White et al ). By contrast, members of the Caryophyllales order generally have larger leaf Mg concentrations than other angiosperm species (White et al ).…”

“…A; Garten , Thompson et al , Sterner and Elser , Broadley et al , Wright et al , Kerkhoff et al , Niklas , Fyllas et al , Elser et al , Reich et al , Veneklaas et al ) and (2) linear relationships between leaf Ca concentration and leaf Mg concentration among specific groups of angiosperms (Fig. B, C; Garten , Thompson et al , Broadley et al , Watanabe et al , Fyllas et al , White , White et al , , Hao et al , Verboom et al ).…”

“…It has been argued that distinct linear relationships between leaf Ca concentration and leaf Mg concentration are exhibited by commelinid monocots, non‐commelinid monocots, eudicots excluding Caryophyllales and Caryophyllales species (Fig. B, C; White et al ). The gradients of these relationships appear to be determined by cell wall chemistry and the Mg/Ca mass quotients in cell walls of the different groups of species (White et al ).…”

“…The gradients of these relationships appear to be determined by cell wall chemistry and the Mg/Ca mass quotients in cell walls of the different groups of species (White et al ). Differences in leaf Mg concentration and leaf Ca concentration between species within each group can be attributed to differences in the cation exchange capacity of their cell walls (White and Broadley , White et al ). The relatively large leaf Mg concentrations of Caryophyllales species have been attributed to their ability to accumulate more Mg in their vacuoles than other species when grown without a supra‐sufficient Mg supply (White et al ).…”

“…The ionome of a particular plant, organ, tissue, cell or subcellular structure is affected by the phytoavailability of elements in the environment, transport processes into and within the plant, plant metabolism and the requirements of specific extracellular and intracellular structures (White and Brown , Baxter ). The ionome differs between plant species growing in the same environment (Broadley et al , White et al , Watanabe et al ), organs, tissues and cells of an individual plant (Sorreano , Cakmak et al , Conn and Gilliham , Subramanian et al , Baxter et al , Eggert and von Wirén , Zhao et al , He et al , Persson et al , Thomas et al , Watanabe et al , de la Fuente et al , White and Pongrac ) and extracellular and intracellular compartments (Sterner and Elser , Hawkesford et al , Broadley et al , , White et al ). Ultimately, differences in the ionomes of plants growing under identical conditions reflect differences in their genomes and gene expression that have evolved through mutation and the selection of adapted phenotypes.…”