It not easy to correlate all environmental and genetic factors to predict time between pollination and formation of the abscission layer (black layer) at base of kernels when the season is as abnormal as 2019 in the USA corn belt. It is established that heat determines the differentiation of growing point into flowering structures instead of leaves in temperate corn hybrids. We mostly classify relative corn maturities among hybrids either by days to black layer or by total heat units, somewhat assuming that the difference between total heat units to black layer and heat units to flowering is the heat units needed to fill the grain.
But are heat units as important for that fill period as it was for determining differentiation of apical meristem? Photosynthesis rate is mostly constant and optimum when temperatures are between 72°F-82°F, slower at 55° and above 85° F, according to one study (Journal of Experimental Botany, Volume 28, Issue 3, June 1977, Pages 519-524).
General metabolism in the corn plant is affected by temperature but it generalized that the optimum is between 55° and 85° as calculated by the GDU’s. However, does that apply to the metabolism directly involved in translocation of carbohydrates from leaves and stem to the grain? Or is it simply about 55 days from pollination to end of grain fill even if cooler than usual for corn even when pollination was later in season in 2019>
Temperatures affecting grain fill during this late flowering seasons probably will give us new information concerning factors affecting black layer formation in corn.
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.