Figure 3.

Salt stress decelerates and modifies root development of Col-0 seedlings. A, The growth rates of individual RSA parameters were calculated for control conditions as well as two different salt stress conditions. The bars represent the average growth rate calculated from 24 replicates. Error bars represent the se. The differences between the growth rates at different conditions were tested with one-way ANOVA with Tukey’s post hoc test of significance. Different letter codes represent distinct groups with a significance level of 0.05. B, The relative effect of salt stress on growth of individual parameters was calculated. The severity of growth reduction caused by salinity stress could be compared over the individual RSA components. Different letter codes represent distinct groups with a significance level of 0.05 as tested with Tukey’s post hoc test. To identify the changes in root mass distribution between the MR and LRs, MR and aLRL were calculated as a ratio of TRS for different growth conditions. C, The ratio between MRL and TRS changed over time as more LRs developed (blue line). This transition was delayed in plants grown at 75 and 125 mm NaCl (red and green lines, respectively). D, The ratio of aLRL to TRS was more dynamic, because initially elongating LRs increased the portion of TRS ascribed to individual LRs; however, when new LRs started to emerge, the aLRL ratio per TRS decreased (blue line). A similar pattern with a slight shift in time and maximum was observed for 75 mm NaCl (red line). This delay in maximum reach and increase in maximum height were more pronounced for the seedlings grown at 125 mm NaCl (green line). The ratios were calculated using the quadratic model for three different salt stress concentrations.