Jul 28, 2010
High Temps Increases Dark Respiration in U.S. Corn, Which Could Limit Yields
Author: Michael Cordonnier/Soybean & Corn Advisor, Inc.
High daytime and nighttime temperatures can put stress on corn plants that could limit the yield potential of the plant. The sugars produced by the corn plant during photosynthesis are used by the plant for cell growth, but they are also consumed by the plant at night during a process called dark respiration. There are two types of dark respiration, the first of which is for cell growth and cellular expansion. The second type of dark respiration is for cellular maintenance, which is the energy needed to keep the cells alive. If you take the sugars produced during photosynthesis and subtract the sugars consumed during dark respiration, what is left over are the sugars that the plant stores in the form of carbohydrates which are used later for grain fill. If too much of the sugars are consumed for dark respiration, then there are less sugars left over for grain filling.
The problem in this equation arises when the temperatures during the growing season are excessively hot. If daytime temperatures exceed 86 degrees, photosynthesis starts to decline and fewer sugars are produced. Therefore, there is no advantage for the corn plant if daytime temperatures exceed 86 degrees. Likewise, as temperatures increase, so too does the rate of dark respiration, which means that the plant is burning more sugar to stay alive and keep cool. As temperatures go up, dark respiration shifts more from cell growth to cell maintenance. If nighttime temperatures are in the mid-70s or warmer, the plant shifts into overdrive and consumes more of the sugars just to maintain cellular activity. This leaves fewer sugars left over for eventual grain filling.
The bottom line is that excessively high temperatures during the day and at night can limit the plant's yield potential. Hot temperatures accompanied by adequate moisture, can result in good corn yields, trend line to a little above trend line, but the possibility of blowing away the old yield record is low. The worst scenario of course would be if the high temperatures were accompanied by a lack of moisture.