The meristematic dome is present at the tip of the ear indicating the developing ear is still producing new rows of ovules along the length of the ear. The upper two-thirds of the ear shows a series of single rows of developing ovules. These ovules eventually divide to produce a pair of rows from each single row. This paired formation is visible near the base of the ear. This division explains why a corn ear always has an even number of kernel rows around the ear.
Placement of the primary ear varies with corn genetics. The corn pictured in Figure 1 is 103 CRM, and the primary ear (the ear to be harvested) is located on the V14 node. In general, corn lines varying from approximately 103 to 118 CRM produce the primary ear on the V13 or V14 node. Corn lines of earlier maturity will place the primary ear on a lower node, such as the V12 node, while corn lines of longer maturity may place the primary ear on a higher node.
The node of primary ear placement is an excellent reference point to determine when ear initiation starts. A general guideline is to determine the node containing the primary ear and then subtract seven. This V stage is approximately when the number of kernel rows around the ear is being established. For example, the corn line in Figure 1 positions the primary ear at the V14 node; thus, the number of kernel rows around the ear is being established at or very near the V7 stage.
Establishment of the number of kernel rows around the ear is a critical event in the life cycle of a corn plant. If a particular corn line normally has 16 or 18 kernel rows around the ear and the ear in question has less than the normal number, then some sort of stress was present at or just before this critical stage. From a diagnostic perspective, if an ear has 12 kernel rows around instead of the normal 16, then the stress factor that caused this event was present at approximately V7. This information helps to establish a “time window” in looking for the environmental event that caused ear response to occur.
The maximum number of ovules that the entire corn ear will produce is determined by the time the corn plant passes through approximately 4 more V stages.