ONTOGENY OF THE VASCULAR BUNDLES AND CONTIGUOUS TISSUES IN THE BARLEYLEAF BLADE

The initiation and development of the major and minor veins and contig uous tissues in the leaf blade of barley (Hordeum vulgare cv. Morex) f ollow similar patterns. Both bundle types are associated with two bund le sheaths, an outer parenchymatous bundle sheath (PBS) and an inner m estome sheath (MS). In both major and minor veins, the procambial stra nd arises in the median layer of cells and gives rise to both the vasc ular tissues and the MS. The PBS and mesophyll, by contrast, originate in all three cell layers of the ground meristem. Development of the v ascular bundles and contiguous tissues in the barley leaf is essential ly similar to that of their counterparts in the leaf of Festuca arundi nacea, another C-3 grass (Dengler et al. 1985). Most differences are r elated to a difference in blade thickness between the two species at t he time of vein initiation.