First root to emerge from the germinating corn seed is the radical extension of the embryo. It is mostly unbranched and growing downwards. Next are the seminal roots emerging from the tissue between the radical and the mesocotyl where the scutellum is connecting the endosperm to the growing embryo. Those roots often are branched. The radical and seminal roots are essential to collecting water and minerals for a few weeks as the mesocotyl pushes upwards to the soil surface.
With the light penetrating a short distance below soil surface, the tip of mesocotyl forms the first node and the coleoptile pushes upwards. The base of coleoptile forms the first stem node. Within the coleoptile is the first leaf connecting to the stem at the second node. By the time the first leaf is fully expanded, and the 2nd and 3rd leaves exposed, all connected to the underground stem, the crown, lateral nodal roots extend. These nodal roots grow laterally first but eventually gravity effect on the cell elongation causes these roots to point downwards. Lateral roots may develop from crown nodes 1-5 and eventually above ground nodes as well.
Lateral roots become the main source of water and mineral absorption as the mesocotyl is cut off from the energy from photosynthesis in the leaves. Seminal roots served their functions to support the early emergence of the shoot. Genetics and environment now become the major influences on the direction and branching of the main root system of the corn plant.
An interesting summary of root development of young corn can be found at http://www.kingcorn.org/news/timeless/Roots.html
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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.