Nighttime in a cornfield

By John Brien, AgriGold Agronomist, CCA
While sleeping comfortably in our beds being cooled by a fan or air conditioning, we forget about our cornfields and what is happening while we sleep. The human body requires rest in order to survive, but a corn plant does not. While we sleep, corn plants continue growing and repairing themselves throughout the night. Corn growers see and witness the happenings of the corn plant during the daylight, but the cover of darkness leaves a couple questions that need answered.
To begin uncovering the dark secrets of a corn plant, understanding what happens during the daylight will help understand what occurs in the darkness. The main theme of daylight activity is photosynthesis. Photosynthesis is the complex processes where the corn plant takes carbon dioxide, water and energy from the sun and makes carbohydrates (sugars and starches). The carbohydrates will then be used to grow the leaves, roots, stalks, tassels, ears, grain, etc. of the corn plant.
Photosynthesis is the engine of the corn plant and the speed of that engine depends on the amount of heat and water that is available. The more warmth and moisture that is available the faster the engine runs and the more carbohydrates are manufactured. But, when temperatures begin to climb above 86 degrees F, the rate of photosynthesis declines and fewer carbohydrates are produced. The same conclusion can be drawn for moisture, as moisture becomes limiting photosynthesis begins to slow as well.
Just as darkness is the complete opposite of light so is the activity of a corn plant during the day and night. During the day sugars and starches are produced and stored and at night they are consumed by the cells to perform several important functions. The process that runs during the night is called dark respiration. Respiration means to “burn.”
Oxygen is used by the plant to burn the stored carbohydrates with in the plant to perform two critical functions. The first function of dark respiration is for cell growth. Corn plants continue to grow during the darkness with the aid of the stored carbohydrates. The second function is for cell maintenance and cooling. Cells continually need repaired and energy is required to fix the cells and maintain a strong healthy plant. Dark respiration uses the carbohydrates that were produced by photosynthesis to produce the energy the plant needs to carry out the two functions of dark respiration.
Similar to photosynthesis, dark respiration is also impacted by temperatures. When nighttime temperatures are below 70° F, the entire system runs smoothly and highly efficient. As temperatures increase more energy is required by the plant to stay alive and remain cool. Dark respiration begins to rapidly accelerate as the nightly temperatures begin to climb above the mid 70’s. As dark respiration speeds up a large amount of energy is consumed by the corn plant.
The goal of growing corn is to produce the most grain possible and large amounts of carbohydrates will be needed to meet this goal. Therefore, the corn plant needs to be able to both maximize photosynthesis and minimize dark respiration in order to maximize yield. While the main focus of grain production is often solely on the daylight hours, but the nighttime hours are just as critical to the success of the corn plant. Dark respiration is an important function of the corn plant. Growth and maintenance continues to improve the corn plant. The balancing act between efficiently using and burning carbohydrates is done while the moon hangs over our head. Just because it is night and many corn growers are sound asleep, remember the corn plants are still hard at work.

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