Chapter 4 118 length to brushing 100 μM IAA on internode or leaf 1, (h) internode 1 diameter to brushing 100 μM IAA on internode or leaf 1, (i) first leaf area (oldest leaf) to brushing 100 μM IAA on internode or leaf 1, (j) second leaf area brushing 100 μM IAA on internode or leaf 1. The data are presented as mean ± SEM, and different letters indicate significant differences between treatments based on ANOVA analysis with Tukey’s post hoc test (P<0.05). There were 6-9 biological replicates, and the experiment was repeated twice. Picture (a) was created with Biorender. 4.2.4 The elongation of internode 1 did not show IAA dose dependency Next, we wanted to investigate if the IAA concentration we were applying was either too high or too low to induce the full FR-like internode 1 elongation. We applied a range of IAA concentrations through brushing on Internode 1 by three applications during one week (length of the FR treatment). We observed that the elongation of internode 1 did not change in response to the IAA concentration (Figure 4.6a). Surprisingly, at both 5 μM and 200 μM IAA, the elongation level of internode 1 remained virtually the same. This suggests that IAA-responsive internode 1 elongation is not dose-dependent on IAA concentration and that our lowest IAA treatment already induced the maximal response possible by IAA alone (Figure 4.6, S4.4). Figure 4.6. Internode responses to different IAA concentrations. We treated 14 day-old tomatoes with different concentration IAA by brushing onto internode 1. Brush were applied 3 times over one week treatment period. The data includes measurements of (a) Internode1 length. (b) Internode1 diameter. Data are presented as mean ± SEM, and different letters indicate significant differences between treatments based on ANOVA analysis with Tukey’s post hoc test (P<0.05). There are 12 biological replicates, and the experiment was repeated twice. We also quantified internode 1 cellular morphology in response to IAA treatments by microscopy to collect clues on how different cell types respond to IAA. In our microscopy analysis of IAA treatment on internode 1, we observed that all cell lengths
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