The frequency of the fibrovascular bundle increases from the lower region to the upper region, and the average size in terms of R/T ratio is inverse to the frequency. The frequency of fibrovascular bundles in the middle region is 20.2 with an average size in terms of R/T ratio of 1.93. The vascular bundles without the fibre sheath connection also have an equal frequency, with an average of 1.98. In the lower-most regions the frequency of vascular bundles without fibre sheath is highly reduced, with an average of 0.25.
Fig. C. Transverse section stained with TBO, where the fibrous sheaths are interrupted and attached to the vascular bundles (girders) towards the inner side. Epidermal cells are tooth-like and covered with a thick cuticle, X 400; Fig. D: Section stained with a natural dye obtained from sappan wood. Lignin rich regions appear yellow to orange in colour. X 100; Fig. E: Core fibrovascular bundle stained with sappan dye. Lignin rich regions appear yellow to orange. Cellulose rich regions appear pink to red, one of the metaxylem is partitioned, X 200; Fig. F: Developing fibre sheath near the vascular bundle stained with fast green, thick walls of sclerenchymatous cells are darkly stained, X 1000.
Histochemistry of Cell Wall Substances
Lignin, which is an important component of the cell wall, stained bright red with safranin, and appeared blue to bluish green on staining with Toluidine blue 'O', a metachromatic dye (Fig. C). Staining with the histochemical reagents revealed that the fibres in close association with the vascular strand were thick walled, while the fibres away from it were thin walled. Staining with Acridine orange and Coriphosphene ‘O’ indicated that different kinds of lignin might be present (Fig. G, J and H). Highly lignified cells appeared greenish yellow, while less lignified cells appeared bright yellow. Sappan, a natural dye, also stained lignified cells. Highly lignified cells appeared yellow,
Benazir et al. (2010). “Sedge fibers and strands,” BioResources 5(2), 951-967.