Corn (maize) is one of the world’s most widely grown crops, providing food for humans and livestock, as well as material for industry. Producing large, grain-filled ears depends on a precise sequence of structural development followed by reproductive events. Understanding how the kernels develop requires observing the chronological progression from a simple stalk to a complex reproductive structure.
Establishing the Structure of the Corn Stalk
The corn plant begins its life by building a robust physical support system, a process known as vegetative growth. The stalk is composed of segments called internodes, which are separated by swollen areas called nodes. Leaves emerge from these nodes, forming a dense canopy that functions as the plant’s food production factory through photosynthesis.
As the plant grows taller, the internodes elongate, pushing the growing point from below the soil surface to a position higher up the stalk, typically around the V6 stage. The nodes serve as attachment points for both the leaves and, later, the potential ears. Below-ground nodes develop the primary root system, while some above-ground nodes may produce brace roots that stabilize the tall plant. This structure must be established before the plant transitions its focus to the creation of reproductive organs.
Developing the Reproductive Components
The corn plant produces separate male and female flowers on the same individual, a characteristic known as monoecious. The male flower structure is the tassel, which emerges from the top of the stalk after the last leaf is fully extended. This structure is highly branched and is responsible for producing and shedding pollen.
The female flower structures, which become the ears of corn, develop lower down on the stalk at the leaf axils of certain nodes. Each potential ear is initially an ear shoot, protected by specialized leaves called the husk. Fine, hair-like strands known as silks grow outward from the ovules on the developing cob. These silks are the functional stigmas of the female flowers, and each silk is connected to a single ovule, which is the potential kernel.
The timing of these developments is coordinated; the tassel typically emerges and begins shedding pollen a few days before the silks emerge from the husk. The silks from the ovules nearest the base of the ear emerge first, with those from the ear tip emerging last. This difference in timing sets the stage for fertilization.
The Process of Pollination and Ear Formation
The culmination of the growth cycle is the transfer of pollen from the tassel to the silks, an event primarily driven by wind. The tassel releases millions of microscopic pollen grains, which drift down and are caught by the exposed, sticky silks. Pollination is successful only if a pollen grain lands on a silk within a short period after the silk emerges.
Once a pollen grain lands on a silk, it germinates and grows a tube down the length of the silk, a journey that can take 12 to 24 hours. This tube delivers the genetic material to the ovule at the base of the silk, resulting in fertilization and the creation of a kernel. Each silk must be pollinated individually to produce a developed kernel; missing kernels often indicate a pollination failure.
Following fertilization, the silk detaches from the ovule and begins to turn brown, signaling its job is complete. The fertilized ovule then begins kernel maturation, starting with the blister stage, where kernels appear white and contain a clear fluid. Next is the milk stage, where the inner fluid is starchy and milky white, which progresses to the dough stage as the fluid thickens. Finally, the dent stage occurs as the kernel dries down and a dimple forms at the crown. Physiological maturity is reached when a dark layer, called the black layer, forms at the base of the kernel, indicating maximum dry weight.