CORN DRY DOWN OR DIE DOWN
The individual plant that wilted and prematurely died because of root rot but is surrounded by living corn plants does not necessarily have drier grain at harvest time. Grain moisture replacement by starch formation in grain stops when the abscision layer (black layer) forms at the base of the kernel. In most corn plants this happens between 55-60 days after pollination at about 30% moisture in grain. Those prematurely dead plants that wilted earlier form abscision layers about a day after the wilting, at a higher moisture percentage.
Grain drying in the field after this time is an evaporation process. Moisture must travel through the pericarp of the kernel at a rate determined by the relative humidity surrounding the grain. Pericarp thickness must be a factor but also plant structures such as cob volume and husk leaves length, thickness and adherence to the grain are major factors.
‘Water runs down hill’ as Professor Loomis in my plant physiology class of 1960 would say to emphasize that it goes from a high concentration to a low one. Grain evaporation rate is very much dependent on relative humidity immediately surrounding the kernels. Transpiration from the senescing, but green, leaves in plants for a time after kernel black layer contribute to higher humidity in the field, including the area surrounding that single dead plant. Eventually, senescence of these plants halts transpiration, leaving the ear structures as the only barrier to response to atmospheric factors such as relative humidity and wind affecting the dry-down of the grain. The individual plant that wilted and prematurely died because of root rot but is surrounded by living corn plants does not necessarily have drier grain at harvest time. (Corn Journal, 9/22,2016)
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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.