1. a 1 9 8 7 12 11 10 4 5 6
Supplementary Figure S1 FTIR spectra of cell wall constituents in untreated (a) and treated (b) leaf blade (red), leaf sheath (green), and stem (blue).

2. a b c d
Supplementary Figure S2 Scanning electron micrographs of epidermis surface and underlying cells in untreated (a and b) and NaOH-treated (c and d) leaf blade incubated in the rumen for 24 h. Cuticle (a) of the untreated straw is intact and the underlying cells have rectangular angles and rigid cell walls completely adhering to one another (b). Alkaline treatment caused crimping in the silicified cuticle layer (c), detaching cells from epidermis (arrow), losing cell morphology (arrow), and disappearing cemented materials between cells (d).