Root characterization of A.thaliana demes under high pH and bicarbonate stress
The hydroponic cultivation of A1(c+),T6(c-) and Col-0 plants under control pH (pH 5.9), high pH (pH 8.3), or bicarbonate (bic, 10 mM NaHCO3, pH 8.3) conditions confirmed the higher tolerance of A1(c+) to both pH 8.3 and bic treatments. Col-0 exhibited an intermediate response, while T6(c-) was the most sensitive (Figure 1 & [38]). Root length was hardly affected by exposure to bic in A1(c+), the deme evolved on the calcareous soil. Contrastingly, root growth in T6(c-) was strongly inhibited by bic, but less affected by high pH (Figure 1A). In A. thaliana Col-0, used as a well-established reference genotype, root length was more inhibited by bicarbonate than A1(c+), but less than the sensitive deme T6(c-). In contrast to both natural demes, Col-0 did not show difference in root growth inhibition between high pH and the bic treatment (Figure 1A).
The standardized root mineral content revealed clear differences in response to high pH and bic among the three A. thaliana variants (Figure 1B). In deme A1(c+) both high pH and bic reduced root Fe, Cu, and Zn concentrations in comparison to the control treatment. However, bicarbonate stress enhanced the uptake of macronutrients such as Ca and P in A1(c+) and Col-0 (Figure S1). In general, high pH and bic reduced Fe contents in both organs in all plants. However, A1(c+) distinctively maintained higher Fe levels under bicarbonate exposure and the Fe translocation from roots to shoots was clearly enhanced in comparison to the control treatment (Figure 1C). Contrastingly, the sensitive T6(c-) had the lowest leaf Fe content despite having higher root Fe levels (Figure S1). Because of this, T6(c-) exhibited a clear inhibition by bicarbonate of Fe translocation from roots to shoots, while high pH strongly enhanced the Fe translocation in this sensitive deme (Figure 1C).