Elongation of the seedling radicle becomes the primary root, sustained by nutrition from the seed endosperm. Extension of hypocotyl towards light includes stem nodes as leaves are produced and eventually extended above the soil surface. Leaves thus produce the carbohydrates to fuel growth of roots from below ground nodes. These secondary roots initially extend laterally but geotropism takes over as the roots grow downwards. Environments and genetics affect the direction, volume and effectiveness of these roots in providing uptake of nutrients and water. These factors also affect the anchoring of the plants and ability to withstand strong winds. More lateral growth provides more strength against midseason lodging factors whereas deeper roots may provide better water uptake during drought periods.
Growth of roots is dependent upon a supply of carbohydrates moving from leaves to the root tips for production of new cells, for root cell growth, uptake of minerals into roots and the transport of minerals to the corn plant parts above the soil surface. Movement of glucose to the roots through the phloem is also an energy consuming process. Root growth competes with above-ground growth for carbohydrates. Distribution of this energy source is affected by genetics, especially those affecting hormone production by root tips.
Root volume tends to continue increasing until about two weeks after pollination. Carbohydrate translocation direction is affected by the hormones produced by kernel embryos, creating competition with the roots. Part of root cell function is a defense against the multiple soil organisms surrounding the roots. Reduction of carbohydrate supply begins to allow more saprophytic fungi to invade the root system. Increases in competition with developing kernels increases the deterioration of the root tissue. The next 40-50 days after pollination become critical to maintaining life in corn roots.
Visit us at the ASTA in Chicago, Dec 9-12 (booth G207)
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.