Fibre maceration and morphometric measurements
Culm samples from the lower, middle, and upper regions were taken and split to separate the outer rind and inner core portions. Thin slivers of 1mm thickness were cut, boiled in water, and then cooled to remove the air bubbles. Slivers were processed separately for maceration (Johansen 1940). The macerated fibres were washed several times with distilled water and stained in 0.05% toluidine blue ‘O’ for 10-20 min or with sappan for 30 min, washed, and mounted in water for observations and microphotography.
Morphometric measurements such as length, width, wall thickness, and lumen width of the macerated fibres of the rind and core regions from the three parts of C. pangorei were made. For each region, twenty-five fibres were randomly chosen for measurements and the mean was taken. Morphometric measurements were made using an ocular micrometer under 10x and 40x magnification of the light microscope. Based on wall thickness and lumen width, the fibres were classified as follows (Metcalfe 1971):
Very thick-walled (vtkf)
Very thin-walled (vtnf)
lumen almost completely closed
lumen less than the thickness of wall
lumen more than the thickness of the wall
lumen much greater than the thickness of wall
Derived values such as slenderness ratio (SR), flexibility ratio (FR), and Runkel ratio (RR) were calculated from the above data as suggested by Tamolong et al. (1957).
Slenderness ratio (SR)= length of fibre / diameter of the fibre
Flexibility ratio (FR) = 100 X lumen width of fibre / diameter of fibre
Runkel ratio (RR) = 2 x wall thickness / lumen width
Chemical analysis of fibres
The processed and split culm strands were used to characterize the chemical properties of fibres for lignin, alpha cellulose, hemicellulose, total waxes, and moisture content following the method of Doree (1950).
One gram of the dewaxed and defatted sample was taken and to this was added 12.5 ml of 72% sulphuric acid. The mixture was incubated at RT for 15 h. The sample was then diluted with water to an acid concentration of 3% and boiled for 2 h, washed, filtered (G3 filter), and neutralized with Ammonia (NH3) solution. It was washed again several times with water until the filtrate was neutral, dried, and weighed. The concentration of lignin was estimated using the following formula.
Lignin (% on dry basis) = 100 x Residue / dry material wt
Benazir et al. (2010). “Sedge fibers and strands,” BioResources 5(2), 951-967.