Chapter 2 40 indication of increased secondary growth in SAS (Figure 2.13) and we wanted to explore the radial growth and the cambium thickness change in more detail. Figure 2.13. Cambium thickness in WL and WL+FR. (a) Tomato internode 1 section indicating where the measurement was taken. (b) Cambium thickness of three-week-old M82 and Moneymaker after seven-day WL and FR+WL treatments. Data are presented as mean ± SEM, Significance between WL and WL+FR is denoted by asterisks (*** p≤0.001). Error bars represent ± SE. There are 18 biological replicates, and the experiment was repeated 3 times. In the 7-day FR treatment, both M82 and Moneymaker internode 1 developed more interfascicular cambium (Figure 2.13). This could be a sign that stem secondary growth was promoted after the FR treatment was applied. We hypothesized that the radial growth is activated by FR to provide support for the upcoming stem elongation. So, we wanted to explore the relationships of stem elongation with radial growth and interfascicular cambium thickness. We found that cambium was thicker in WL+FR in an agedependent fashion (Figure 2.14). We compared also how internode 1 length correlated with cambium thickness with data from various time points (Figure 2.15) and tried to resolve the relationship with statistics. The regression lines show the linear linkage between internode 1 length and cambium thickness, which indicates there is a potential relationship. In the WL+FR, the stem growth was promoted as was cambium thickness compared to WL, but overall the WL+FR internodes had much thinner cambium than WL internodes of comparable length. We had observed development of M82 and Moneymaker and seen that M82 in general grows quicker than MM in stem elongation, flowering, and aging (see Chapter 1, section 1.1.2). The increase in cambium thickness in M82 is also quicker than in Moneymaker (Figure 2.14), which reflects the cultivar-specific differences.
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