Morphological and Anatomical Variations among Barley Cultivars Influence Straw Degradability

Differences in organization at morphological, anatomical, and molecular levels can influence overall fiber degradability of plant material by rnmen microorganisms. The morphological composition (leaf blade, leaf sheath, and stem content) of straw from three barley (Hordeum vulgare L.) cultivars was determined, and various quantitative anatomical measures, including the proportion of internode area occupied by specific tissues, cell number per unit area, and cellwall thickness, were made on stem sections using scanning electron microscopy (SEM) coupled with image analysis. Values obtained were related to the neutral detergent fiber (NDF) degradability the straws and their botanical fractions. The greater degradability of Doublet compared with Golden Promise and Klaxon was related to its higher leaf content (blade and sheath), and the inherently greater degradability of its leaf and stem fractions. Their differences in stem degradability were also more pronounced than those in leaf degradability. Substantial degradation of the internode tissue was observed, with disruption and erosion of the ground parenchyma cells, and thinning of sclerenchyma cell walls. Although the proportion of tissue area was similar for all cultivars, Doublet and Klaxon had a higher number of ground parenchyma cells per unit area than Golden Promise; Golden Promise, in contrast, had a higher number of sclerenchyma cells. Klaxon had thicker epidermis cell alls than the other cultivars, and thinner ground parenchyma cell walls than Doublet. These observations suggest that the differences in NDF degradability were closely related to variations in the composition and degradability of straw fractions, variations in the number and cell-wall thickness of specific cell types, and the inherent differences in the degradability of different cell types. This research was supported in part by a 1989 Scientific Grant of the Ito Memorial Foundation.