Chapter 2 44 2.2.7 No vascular bundle responses to FR were found The effects of WL+FR treatment on the vascular bundle structure was also investigated. Cross sections of the stem of plants grown in WL and WL+FR were made. These sections were stained using 0.02% Toluidine and 3% Phloroglucinol and imaged using a light microscope (Figure 2.19). In both tomato cultivars, far-red enrichment did not lead to an increase or decrease in the percentage that xylem contributes to the vascular bundles (Figure 2.19). WL MM WL+FR MM WL M82 WL+FR M82 0 10 20 30 40 Xylem area/vascular bundle area*100% ns (a) (b) Figure 2.19. Quantification of vascular bundles of the first internode after 7D of treatment. (a) Illustration of xylem under microscopy. Xylem stains purple at the center of the bundle while the phloem cells are on the outward edge of the vascular bundle. (b) Percentage of xylem in the vascular bundles. Both tomato cultivars were treated with WL or WL+FR for 7 days. Error bars represent SEM (n=8). Different letters indicate a significant difference between means (p < 0.05). 2.3 DISCUSSION Crops often develop in resource-limited environments, and one common limiting resource is light at high planting densities. The SAS (shade avoidance syndrome) is a common response, and there are many commercial crops such as raspberry, apples and corn (Maughan et al., 2017) that suffer from light shortage-related yield loss. And tomato is one of these plants. In the earlier study conducted by Bush and colleagues(Bush et al., 2015), the stem elongation phenotype was clearly observed, but a comprehensive analysis of cellular anatomy was not carried out. To address this gap,
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