FTIR prediction of cell wall digestibility. (A) Distribution of cell wall digestibility (μg.mgDW-1.h-1) from a diverse collection of S. bicolor ecotypes grown under a range of different conditions and harvested at varying developmental stages. A fitted normal distribution has been overlaid. (B) PLS prediction of cell wall digestibility (D; μg.mgDW-1.h-1) in an independent test set. Predictions are plotted against the known reference values for each sample. Calibration samples (○) and independent validation samples (•) were overlaid on a target line (y = x). The coefficient of determination (R2) and root mean square error (RMSE) for each sample set are inset. DW, dry weight; FTIR, Fourier transform infrared; PLS, partial least squares; RMSE, root mean squared error.