That wilted corn plant, often surrounded by green plants with carbohydrates still being transported to the grain, did not have sufficient supply of carbohydrates available to meet the draw to the ear. This may have been due to reduced photosynthesis because of leaf tissue destruction from leaf disease or hail, shading from adjacent plants, insufficient potassium available or dark cloudy days.
Movement of carbs to the grain is directed by hormones produced in growing points, each embryo having an apical meristem producing auxins to direct the flow. Genetics affects the amount per day and number of meristems affects the total flow per day. If daily photosynthesis in leaves is insufficient to meet this demand, reserves stored in the corn stalk are drawn upon. Sugars that are being stored in grain are also required to maintain life in the root cells. Depletion of stalk sugar reserves available to roots, eventually weakening those cells ability to resist invasion by soil microbes.
Eventually, root rot reduces water uptake and transport that water availability to transpiring leaves causes desiccation of all plant tissue. All leaves on this plant show the wilting symptom by a gray appearance and pointing downwards. Wilting also causes the pith tissue, previously attached to the inner layer of the rind tissue to shrink away from that attachment. Stalk cells die. Chloroplasts in the outer rind cells die, resulting in the lower stalk tissue turn from a green color to yellow-green and eventually brown, while adjacent plants continue to have a green color.
Abscission layers form at base of all leaf tissues immediately after tissue wilting. That includes the formation of black layer at base of each kernel. Consequently, these kernels will not have as complete grain fill as the adjacent green plants that continue to receive the flow for the 55 days after pollination. If the major cause of the early wilt was from producing more kernels than the adjacent green plants, the total grain weight on the wilted plant may not be much different although the weight per kernel will be less.
Cause and effect of wilting corn plants is dynamic with multiple interactions between the corn biology and environments. Assessment of these potential causes when they occur could be useful in preventing significant yield and harvest problems in the future.
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.