If you are reading this, corn has touched your life in some way. We eat corn, animals eat corn, cars eat corn (well, it can be used as a biofuel), and we even can eat corn out of a container made from corn (think: bioplastics). It is projected that the U.S. corn yield will reach over 14 billion bushels. However, what do you know about the corn plant itself? Did you, for example, know that corn is a grass and not a vegetable?
The Seed: The Beginnings Of The Corn Plant
Look at a corn cob - you will see the seeds! The kernels that you eat can also be used as the seed source to start new plants. Don't worry; the corn kernels that you eat won't grow in your stomach. Specific corn plants are set aside to provide seed.
Corn Growth Stages
The corn plant's growth stages are broken down into vegetative and reproductive stages.
- The vegetative growth stages are VE (emergence of the plant), V1 (first fully expanded leaf), V2 (second fully expanded leaf), etc. up to however many leaves appear. The last stage is called VT, referring to when the tassel fully emerges.
- The reproductive stages are noted as R1 through R6. R1 refers to when the corn silks are first visible outside the husks and pollination occurs. (This process will be explained more fully later in the article.) During the other stages, the kernels are developing. At the final (R6) stage, the kernels have reached their maximum dry weight.
Seedlings are dependent on kernel reserves up until about the V3 leaf stage when they become dependent on the roots to take up nutrients.
Corn plants are unusual in that they have two distinct sets of roots: regular roots, called seminal roots; and nodal roots, which are above the seminal roots and develop from the plant nodes.
- The seminal root system includes the plant's radicle (the first root emerging from the seed). These roots are responsible for taking up water and nutrients, and for anchoring the plant.
- The second root system, the nodal roots, is formed about an inch or so below the soil surface, but above the seminal roots. The nodal roots are formed at the base of the coleoptile, which is the primary stem that emerges from the ground. The nodal roots are visible by the V2 stage of development. The seminal roots are important to the survival of the seedling, and damage can delay emergence and stunt development. This is because the corn plant depends on the nutrients present in the seed until the nodal roots are developed. As soon as the coleoptile emerges from the soil, the seminal roots cease to grow.
Nodal roots that form above the ground are called brace roots, but they function similarly to the nodal roots below the ground. Sometimes brace roots actually penetrate the soil and take up water and nutrients. These roots may be needed for water uptake in some cases, as the crown of a young corn plant is only about 3/4" below the soil surface! Therefore, corn can be vulnerable to dry soil conditions as they don't have a deep root system.
Corn Stalk And Leaves
Corn grows on a single stem called a stalk. Stalks can grow up to ten feet tall. The plant's leaves emerge from the stalk. A single corn stalk can hold between 16 and 22 leaves. The leaves wrap around the stalk, rather than having a stem. The part of the leaf that wraps around the stem is called the node.
Corn Reproductive Structures: The Tassel, Flowers, and Ears
The tassel and the corn ears are responsible for reproduction and formation of the corn kernels. The tassel is the "male" part of the plant, which emerges from the top of the plant after all of the leaves have developed. Many male flowers are on the tassel. The male flowers release pollen grains which contain the male reproductive cells.
The female flowers develop into the corn's ears, which contain the kernels. The ears contain the female eggs, which sit on the corn cob. Silks - long strands of silky material - grow from each egg and emerge from the top of the ear. Pollination occurs when pollen is carried from the tassels to the exposed silks on the ear of corn, which is the female flower on the plant. The male reproductive cell goes down to the female egg contained within the ear and fertilizes it. Each strand of fertilized silk develops into a kernel. The kernels are arranged on the cob in 16 rows. Each ear of corn averages about 800 kernels. And, as you learned in the first section of this article, each kernel can potentially become a new plant!