Abstract
The morphological components (leaf blade, leaf sheath, and culm content) of straw from 26 rice (Oryza sativa L.) cultivars was determined, and various quantitative anatomical features, including the proportion of internode area occupied by specific tissues and staining reactions for lignin, were made using scanning electron microscopy coupled with image analysis and light microscopy. Values obtained were related to the dry matter degradability of the straws and their botanical fractions. The greater degradability of rice straw was related to its higher culm content, and the inherently greater degradability of its culm fraction. The differences in culm degradability were also more pronounced than those in leaf degradability. Substantial degradation of the internode tissue was observed with disruption and erosion of less-lignified ground parenchyma cells, but more lignified vascular bundle remained intact. The proportion of tissue area occupied by ground parenchyma was positively related to the culm degradability, while negatively related to that of vascular bundle. These observations suggest that the differences in dry matter degradability were closely related to variations in the composition and degradability of stem fraction, variations in tissue area of specific cell types, and the inherent differences in the degradability of different cell types.
