Ontogeny of the vascular bundles and contiguous tissues in the barley leaf blade

The initiation and development of the major and minor veins and contiguous tissues in the leaf blade of barley (Hordeum vulgare cv. Morex) follow similar patterns. Both bundle types are associated with two bundle sheaths, an outer parenchymatous bundle sheath (PBS) and an inner mestome sheath (MS). In both major and minor veins, the procambial strand arises in the median layer of cells and gives rise to both the vascular tissues and the MS. The PBS and mesophyll, by contrast, originate in all three cell layers of the ground meristem. Development of the vascular bundles and contiguous tissues in the barley leaf is essentially similar to that of their counterparts in the leaf of Festuca arundinacea, another C-3 grass (Dengler et al. 1985). Most differences are related to a difference in blade thickness between the two species at the time of vein initiation.