Hormone interplay in the regulation far-red-responsive stem elongation in tomato 4 131 0 25 50 100 0 0 20 40 60 80 BR concentration(μM) Stem length(mm) WL WL+FR a a ab bc c 0 25 50 100 0 0 10 20 30 40 50 BR concentration(μM) Hypocotyl length(mm) WL WL+FR a a b b ab 0 25 50 100 0 0 5 10 15 20 BR concentration(μM) Internode 1 length(mm) WL WL+FR a bc c a ab 0 25 50 100 0 0 1 2 3 BR concentration(μM) Hypocotyl diameter(mm) WL WL+FR ns 0 25 50 100 0 0.0 0.5 1.0 1.5 2.0 2.5 BR concentration(μM) Internode 1 diameter(mm) WL WL+FR ns (a) (b) (c) (d) (e) Figure 4.16. Stem responses to different concentration BR. We brushed the first internode of 14 day-old tomatoes with different concentration BR (or mock) in WL or FR conditions over one-week treatment. Brushing was applied 3 times over one week treatment period. Data includes measurements of (a) Stem length, (b) Hypocotyl length, (c) Internode 1 length, (d) Hypocotyl diameter, (e) Internode 1 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 followed this up by testing the combined effects of GA and BR at a concentration of 100 μM (Figure 4.18). We observed that BR alone was able to induce internode elongation similar to the supplemental FR treatment. We found that GA resulted in significantly greater elongation than supplemental FR unlike in our previous experiment (Figure 4.14). The combination of GA and BR did not show a further increase in elongation compared to GA alone. Additionally, we investigated the effects of GA and BR on stem diameter. Both GA and BR were found to induce an increase in diameter, with GA inducing a greater increase compared to BR when tested individually. To summarize, GA induces greater internode elongation than FR or BR, and the combined effects of BR and GA are not additive.
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