As we look for those first seedlings poke up to reach the light it is easy to miss the amazing feat that has been accomplished. Breeder efforts is selecting genetics, seed producers care during production, and growers efforts with soil preparation and care in seed planting results in the biology of each seedling pushing the shoot up and root down. A cooperative effort by all results in a uniform emergence.
The first appearance of corn seedling tissue emerging from the imbibed seed is the new root. This young seedling primary root can be considered as three regions: meristem, elongation and mature. The cell elongation area provides the main initial force for pushing through the kernel pericarp. Cell elongation and maturation involves production of many new molecules composing the cell walls as they grow. The pectins, hemicelluloses and celluloses that compose the new cell walls are composed of several sugar-related molecules joined together through specific reactions, assisted by enzymes, heat energy and chemical energy such as from ATP.
Energy and components for the biosynthesis of these cell wall components comes mostly from the endosperm. Starch in the endosperm is broken down with enzymes into sucrose molecules, moved to root cell cytoplasm where other enzymes break down the sucrose into glucose and fructose. With other enzymatic action, the fructose is made into more glucose. Modification of these sugars allows other new carbohydrate based molecules that become linked to form the more complex polysaccharides such as pectin, hemicellulose and cellulose for the new cell walls.
We see what looks like a rather simple process- seed swells, root protrude and a few days later the stem emerges from the seed. What we don’t see is a complex utilization of stored energy, production of complex proteins some of which act as enzymes assisting in linking molecules together and thus giving outer strength to cells. Also, unseen is production of anti-microbial compounds to ward off the many organisms attracted to the very molecules stored and manufactured in the seed. We don’t witness the genetics that programs for these processes. Humans successfully selected for these features from a wild plant species, adapting it to worldwide growing environments. The complexity of corn seed germination still can be challenged in a cold, wet spring such as being experienced in the central U.S.A. spring, but it is amazing that these processes work even under tough environments
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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.