Procambial Initiation for the Vascular System in the Spikelet of Wheat

Development of the procambial system of the spikelet of wheat is described from serial transections of successively older primordia selected before anthesis. The procambial median traces of the two glumes merge into the procambial system already in the rachis. More distally in the spikelet primordium, the procambial median traces of the first two lemmas, and then the major lateral traces of the two glumes differentiate in isolation and merge successively with the glume median traces linked to the rachis. Such mergers establish the procambial paired sympodia, which will become the junction of all procambial strands developing distally in the spikelet with the vascular system of the rachis. The paired sympodia form an arc opposite the rachis traces. The first procambial traces from the distal regions of the spikelet to augment the paired sympodia by basipetal mergers are the major laterals of the lemmas of the first two florets. The major lateral traces of all lemmas of the spikelet become interconnected by...