3.2 Root hair traits in maize
We further computed the root hair length and density for Tak Fa 1, Tak
Fa 2 and Tak Fa 3 under all four treatments (Figure 3, columns a,b,c).
In each replicate, which had more than one image, we calculated the mean
root hair length as the mean of all root hairs from all images and the
density as the total number of root hairs from all images divided by the
total length of the root edge from all images. Despite root hairs in the
Tak Fa 3 control group being on average 384.1μm long and thus, 73.7μm
and 58.0μm longer than Tak Fa 1 control and Tak Fa 2 control,
respectively, the difference was not statistically different. We further
did not observe significant differences in density between all three
genotypes, despite Tak Fa 2 being 69% and Tak Fa 3 44% denser than Tak
Fa 1. We did not observe any significant differences in density between
all treatments to the control group in Tak Fa 1 and Tak Fa 3. Only in
Tak Fa 2 we observed a decrease in root hair length by 112.0μm under
reduced nitrogen with weak significance (p =0.057).
To show how our results compare to standard manual root hair
measurements, for each image we correlated the mean root hair lengths of
all automatically extracted root hairs to the mean of the five
representative root hairs (Figure 3, column d). For all three genotypes
we obtained high correlations (Tak Fa 1:R 2=0.78, p <.001; Tak Fa 2:R 2=0.85, p <.001; Tak Fa 3:R 2=0.72, p <.001). Similarly,
we correlated root hair density from the automatic method to manual
measurement and obtained strong correlations as shown in Figure 3,
column e (Tak Fa 1: R 2=0.66,p <.001; Tak Fa 2: R 2=0.46,p <.001; Tak Fa 3: R 2=0.38,p <.001).