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Lax midrib1-O, a Systemic, Heterochronic Mutant of Maize
Denise E. Schichnes and Michael Freeling
American Journal of Botany
Vol. 85, No. 4 (Apr., 1998), pp. 481-491
Published by: Botanical Society of America, Inc.
Stable URL: http://www.jstor.org/stable/2446431
Page Count: 11
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Lxm1-O, a dominant EMS (ethyl methanesulfonate) induced mutation in maize (Zea mays, Poaceae), was originally reported to affect the blade/sheath boundary over the midrib region of the leaf. Here we present a more extensive analysis of the Lxm phenotype in nine different inbred lines. Lxm leaves are longer and narrower, and can initiate ectopic leaves. Additionally, Lxm1-O affects all plant organs observed. Compared to wild-type siblings, Lxm plants have fewer nodes, basal displacement of reproductive structures, and advance more quickly to the reproductive phase. We address questions as to whether Lxm1-O abbreviates a specific developmental phase, using hair, wax, and ear node data. We found that each phase was affected, although to varying degrees, depending on the inbred line. We interpret Lxm1-O to be a heterochronic mutation, causing the developmental acceleration of each phase of the shoot. Lxm1-O is novel, since other systemic heterochronic maize mutants prolong the juvenile phase, thereby extending shoot development. We discuss the importance of heterochronic mutations in the context of morphological evolution.
American Journal of Botany © 1998 Botanical Society of America, Inc.