Abstract Detail

Anatomy and Morphology

Gladish, Daniel K. [1], Saito, Susumu [2], Niki, Teruo [2].

Comparison of the root apex anatomy of maize and teosinte and reassessment of their promeristem structure and its role in metaxylem histogenesis.

Zea mays primary root apical meristems have specified "closed organization", and it has been proposed that it conforms to predictable rules in the differentiation of metaxylem vessels. Despite being conspecifics, we speculated that root apical meristem organization of a wild subspecies of Z. mays (ssp. mexicana, a teosinte) would differ from a domestic sweetcorn cultivar ('Honey Bantam') and may deviate from the previously proposed rules. An understanding of such differences could contribute to our understanding how evolutionary processes and domestication of maize have affected root development in this species.
Root tips of seedlings were prepared and sectioned for light microscopy. Many of the sections were treated with RNase before staining with toluidine blue to increase contrast between walls and cytoplasm to facilitate measurements and analysis. Longitudinal and serial transverse sections were cut at 1.5 micrometers, photographed with a digital camera, and analyzed using computer imaging to precisely determine the position and timing of key developmental events.
Metaxylem development in this teosinte differed from the 'Honey Bantam' sweetcorn only in that the numbers of late metaxylem in the latter are typically two-fold greater and the number of cells in transverse sections of procambium were greater in the latter, but cell sizes were the same. Promeristems of both were nearly identical in size and organization, but did not operate quite as previously described. We observed that the promeristems of both subjects had four histogen layers rather than three as typically interpreted in the past. Mitotic activity was rare in the quiescent centers, but occasionally a synchronized pulse of mitoses was observed there, contrary to previous reports.
Neither the wild subspecies nor the cultivar in our study conformed to the previously proposed rules well. Our reinterpretation of histogen theory and procambium development should be useful for future detailed studies of regulation of development, and its evolution, in Zea mays.

1 - Miami University, Department of Biology, 1601 University Blvd., Hamilton, OH, 45011, USA
2 - Takushoku University, Department of Biotechnology/Faculty of Engineering, Tatemachi 815-1, Hachiojishi, Tokyo, 193-0985, Japan

Keywords:
root development
metaxylem
procambium
histogen
teosinte
Zea mays.

Presentation Type: Oral Paper
Session: 13, Anatomy and Morphology II
Location: 113/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 2:30 PM
Number: 13005
Abstract ID:285
Candidate for Awards:None