Vascular System of the Stem of the Wheat Plant. I. Mature State

Abstract

The courses of the various vascular bundles in the nodes of the main tiller of Triticum aestivum L. have been reconstructed from anatomical observations of con- secutive serial transverse sections. Of the bundles entering a node (n) from its attached leaf, the first-formed and largest, the median, passes directly through the node to the second node below (n-2), where it bifurcates and fuses with other strands. These continue to node n- 3 before fusing completely with the nodal plexus. The next six bundles to form (laterals) establish some links with bundles from higher leaves in the node of entry, much more extensive connections in node n- 1, and fuse completely with the nodal plexus in node n-2. The next four lateral bundles to differentiate are more extensively linked in node n and fuse completely with the nodal plexus in node n - I . The remaining 16-20 bundles from the leaf (intermediates) follow much the same course but develop more extensive connections with other bundles. The extensive plexus which develops in each node ensures vascular connections between most bundles. The significance of these in transport is briefly discussed.