Seminal root emerges
Corn embryo cells are stimulated with imbibition as chemical energy in the form of ATP, allows for the production of complex molecules for elongation of existing cells and production of new ones. The radicle, located near the tip of the kernel, breaks through the pericarp to form the non-branching, seminal root. It is attached to the scutellum at a node. As this seminal root pushes away from the kernel, tropism from gravity, causes the root to go downward.
As the stem apical meristem elongates to form the first leaf tissue, the node at the base of the coleoptile, remaining in the soil, allows the growth of the lateral seminal roots. These roots branch, forming branches of a fibrous system. These lateral seminal roots also turn downwards because of tropism.
Energy for growth of seminal roots mostly comes via the scutellum from the endosperm. These carbs are moved to mitochondria for ATP production and to other cell organelles to form the new cytoplasm contents and cellulose cell walls as these roots grow. Residual carbs and ATP in the embryo are sufficient to get some germination, however, as shown when embryos excised from the endosperm germinate. The growth is limited, however, unless carbs are supplemented by artificial media.
Seminal roots absorb water and minerals from the soil further supplying the early growth of the seedling. After the apical meristem pushes the green leaf tissue through the soil surface, allowing photosynthesis to produce the carbohydrates, new nodal roots develop at base of the first several leaves. With this development, the seminal roots stop growing and start to senescence. Dependence on the stored carbohydrates in the endosperm ends as new sources are now available. Nodal roots now take over the role of water and mineral absorption for the plant.
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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.