Isolation of anatomically defined cell walls from fodder kale, and their contributions to determining the in vitro cellulase digestibility of the whole plant

Abstract

SUMMARYVascular and non-vascular cell walls were isolated separately from leaves, upper stems and lower stems of 12 kale (Brassica oleracea L.) cultivars, by a sieving technique. The digestible organic matter in the dry matter (DOMD) of the cell walls and of the whole plants was determined by pepsin-cellulase digestion. The measured whole-plant DOMD correlated closely with the DOMD predicted by adding together the amounts of non-digested material derived from all the plant's component cell-wall fractions. Differences in DOMD between cultivars were determined primarily by the amount of vascular cell walls in the stems, particularly the lower stems; that is, by the stem anatomy. The vascular cell walls of the upper stems had a wider range of DOMD values and a higher mean DOMD than the vascular cell walls of the lower stems. Thus cell-wall composition made some contribution to determining the whole-plant DOMD, although it contributed less than the anatomy of the stem.