Shoot apical meristem in corn
Cell division after union of the pollen nucleus with the ovule nucleus in corn begins about 2 days after pollination. One of those two cells is destined to become the scutellum part of the embryo and the other the shoot and root. Over the next 45-50 days further cell division in the shoot portion results in cells destined to be the first 5 or 6 leaves and 2 layers of only a few cells at the tip that, although dormant from desiccation, remain as stem cells. These cells remain undifferentiated, that is not committed to any distinct plant part. This is the shoot apical meristem (SAM). With imbibition, water into the seed, cell division of these cells continues. Plant hormones such as cytokinins and gibberellic acid are involved in the rate and continual division of these stem cells at the tip of the shoot as it is near ground level while most leaves are now several inches above the surface. As the new cells do become committed to leaf tissue formation and axillary meristems with potentials to form ears.
Each corn cell includes a nucleus with the same 10 chromosomes and the same 32000 genes as the stem cells of the meristem but have become committed to produce specific tissue. Apical meristem cells in corn continue to produce more cells and resulting leaves and stem structure until special flowering hormones produced in the leaves are transmitted to the apical meristem cells to now produce those that become the tassel. That completes the life cycle of the apical meristem of corn.
This is how it works when all goes as we want. Some plant pathogens can interact with this system to mess up the plan.
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About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.