Buffalo, New York
Williamsville East HS
State University of New York
London, Ontario
University of Western Ontario
Taipei, Taiwan, Rep. of China
Melbourne, Australia
Swinburne University of Technology Stem development in na1/na1 and na2/na2 --Cheng, WY, Cheng, P-c, Gu, M, Gan, X, Chung, H-W, Walden, DB In contrast to the parallel arranged longitudinal vascular bundles commonly found in the internodes of wild type (a, e), na1/na1 appears poorly organized (b). However, cross-sectional views reveal that the vascular arrangements of the entire na1/na1 stem (f, g and h) resemble those found in the nodal region of a normal plant (d). Therefore, one may consider the entire na1/na1 stem comprises a single node (b). Similar to the main stem, the ear branch of na1/na1 also lacks a well-defined internode structure. It is important to point out that the elongation and vascular arrangement in the internodes of na1/na1 tassel are "normal". The branching of a vertically arranged vascular bundle (v) is evident in the series of optical sections (k, i, m and n) obtained by multi-photon fluorescence microscopy.

In contrast, na2/na2 stem has a "normal" stem appearance but the internode length is significantly shorter (c). The cross-sectional views of na2/na2 stem (i and j) reveal similar nodal and inter-nodal vascular arrangement, as found in the wild type (d and e). The elongation of tassel internodes occurs in na2/na2 (c).

Figures (previous page): (a) longitudinal section of a wild-type maize stem (Ohio43 inbred). (b) na1/na1 stem; (c) na2/na2 stem; (d and e) cross-sections at node (d) and internodes (e) from wild-type plant; (f, g and h) cross-sections at various levels of na1/na1 stem; (f) and (g) are physical sections while (h) is an MRI section; (i and j) cross-section of na2/na2 stem at node (i) and internodes (j). All the plants used in this study were grown at the field station of the University of Western Ontario, London, Canada in the summer of 2000. The specimens were fixed in methanol, serial sectioned with a razor blade using a specially made jig. The image was obtained by using a modified Acer 600CU flat-bed scanner (600dpi optical resolution, equipped with back-lighting) in liquid. (k-n) show a set of optical sections (cross-sections) from na1/na1 stem. The optical sections were obtained at various depths (0mm � 75mm) by two-photon florescence microscopy using 870nm near IR illumination. An Olympus Fluorview FL300 confocal microscope equipped with a Spectra-Physics Mai-Tai tunable Ti-sapphire laser was used for this study.
 
 

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