Cell elongation in the area of the apical meristem results in the upward growth of the area between the seed and seminal roots and eventual emergence of the first leaf from within the coleoptile. That mesocotyl tissue functions as a passage for energy (glucose) and minerals supplied by the seed endosperm and seminal roots to the newly forming upper tissue.
Mesocotyl growth continues until the coleoptile emerges from the surface of the soil where reactions from light, especially the blue wavelengths, results in more lignin deposition in the cell walls of the mesocotyl, essentially stopping its elongation. The mesocotyl continues to function as a conduit to supply the development and emergence of the first leaves developing in the tightly wrapped coleoptile.
Metabolism in the mesocotyl cells is greatly affected by heat energy. Growth is slower in colder soils and could also be slowed with low oxygen supply when in fully water saturated soils. Heavily encrusted soil surfaces may also interfere with ability of mesocotyl ability to cause the coleoptile to emerge, resulting in twisted mesocotyl and even leaves to push through the tip of coleoptile before emergence.
The secondary roots, also called nodal roots, form at the base of the coleoptile just below the soil surface as it releases the first new leaves. This new source of carbohydrates along with the minerals and water absorbed the new roots as the utility of the kernel, seminal roots and mesocotyl is reduced. The relatively short performance of these seedling parts is essential in establishing timely starts to the crop affecting not only number of plants but also the uniformity of the crop.
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.