PIZZOLATO, THOMPSON D.1 and MARSHALL D. SUNDBERG2.* 1Department of Plant and Soil Sciences, University of Delaware, Newark DE 19717-1303; 2Department of Biological Sciences, Emporia State University, Emporia KS 66801-5087. - Initiation of the vascular system in the shoot of Zea mays L (Poaceae). 1) The procambial nodal plexus.
All procambial strands in six contiguous nodes below the tassel
primordium of a young maize plant were traced from serial transections
to reveal the pattern of vascular development. Each node consists of a
disk of insertion and it's subtended leaf primordium. Within each disk
of insertion, concentric, successive waves of isolated procambial
strands are generated by a peripheral primary thickening meristem.
These discrete traces become linked into sympodial leaf traces by
merging with procambial traces from the subtended leaf primordia and
with procambia of adjacent waves of their own and of adjacent disks of
insertion. Median leaf traces, major lateral leaf traces, bud traces
and intermediate leaf traces penetrate the disks of insertion to
respectively decreasing depths. In addition, some procambia in the
successive waves within a disk of insertion persist with blind ends.
The nodal plexus arises as ground parenchyma adjacent to these blind
endings dedifferentiates and forms horizontal procambial strands.
Key words: anatomy, development, node, procambium, Zea