Comprehensive Plant Cell Wall Fractionation

The plant tissues were dried at 65 °C until a constant weight was reached, and mechanical crushed using a knife‐mill. Plant cell wall fractionations were extracted as described previously (Li et al., 2015; Peng et al., 2000) with minor modifications.
For crystalline cellulose extraction, samples (0.1 g) were suspended in 5.0 mL acetic acid–nitric acid–water (8 : 1 : 2, v/v/v) and heated for 1 h in a boiling water bath with stirring every 10 min. After centrifugation, the pellet was washed several times with 5.0 mL water and dissolved in 67% H₂SO₄. Total hexoses in 67% H₂SO₄ were regarded as cellulose.
For pectin extraction, the dry biomass powder samples (0.1 g) were treated by potassium phosphate buffer (pH 7.0), chloroform–methanol (1:1, v/v) and DMSO–water (9:1, v/v) to remove soluble sugar, lipids and starch. The remaining pellets as crude cell wall was suspended in 0.5% (w/v) ammonium oxalate (5.0 mL) and heated for 1 h in a boiling water bath, and the supernatants were total pectin.
For hemicelluloses monosaccharide analysis, the pellet after pectin extraction was dissolved by 1.0 mL 2 m TFA to release free monosaccharides in the sealed tube at 121 °C in autoclave (15 psi) for 1 h. The supernatants extracted from TFA reaction were separately transferred into 5 mL screw‐cap test tubes. Myo‐inositol (200 μg) was added as the internal standard. The supernatant was dried under vacuum at 38 °C to remove TFA, then were neutralized, dialysed and lyophilized according to the method described by Xu et al. (2012).