2.5.3. Lignin content
Lignin content was determined using the thioacidoglycolysis
method, modified from Bruce and West (1989). Twenty-five grams
of each fresh tissue (tip and base) was homogenized individually
using 95% ethanol for 5 min then
filtered using Whatman No.
4
filter paper under vacuum. The residue was washed with 17 mL of
ethanol and dried at 50 C for 24 h. Approximately 0.25 g of the
dried residue was mixed with 7.5 mL of 2 N HCl (Merck KGaA,
Germany) and 0.5 mL of thioglycolic acid (Carlo Erba Reagenti SpA.,
Italy), then boiled in a water bath for 4 h.