As the flow of carbohydrates to the developing grain intensifies, cells in leaves begin senescence. Along with these changes in cellular metabolism it is probable that production of the chemicals associated with limiting microorganisms with potentially destroying cells as they feed on carbohydrates and protein contents. The nature of the battle between the living plant material and surrounding micro-organisms.
Vigorous cells of corn plants before pollination were only overcome by microbes with specific metabolites that overcome the resistance mechanisms. Senescing cells are overcome by others that are no longer inhibited. Definition of pathogens becomes more ambiguous as these organisms attack the tissue in senescing tissue. Some fungi such as Fusarium species may have been present in the plant for much of the season, but not destroying much tissue until natural senescence begins. At what point do we call it a pathogen and not just a saprophyte?
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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.