Chapter 4 126 Figure 4.12. IAA concentration in internode 1 in response to 1-hour, 2-hour, and 6-hour FR treatments. We also assessed the circadian influence through 1-hour far-red treatment initiated in morning and afternoon. 4.2.8 A high concentration of GA can completely recapitulate the elongation induced by FR. Given that the application of auxin did not yield as strong an elongation response as we observed in supplemental FR-treated plants, we proceeded to investigate the impacts of other hormones. GA-related gene expression was affected in FR-enriched stems (Figure 4.2), and also GA is known to play a role in FR-responsive elongation in Arabidopsis (DjakovicPetrovic et al., 2007; Kohnen et al., 2016b). So, we next investigated the role of gibberellin (Figure 4.13) and the combined influence of gibberellin and auxin (Figure 4.14). Figure 4.13. Stem response to different GA3 concentrations. We brushed the first internode of 14 -day-old tomatoes with different concentration GA (or mock) in WL or FR conditions over one week FR treatment. Brush were applied 3 times over one-week treatment period. The data includes measurements of (a) First internode length (b) First internode 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.
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