P&PDL Picture of the Week for
April 21, 2008

Corn Germination

R. L. (Bob) Nielsen, Extension Agronomist, Department of Agronomy, Purdue University

Germination is the renewal of enzymatic activity that results in cell division and elongation and, ultimately, embryo emergence through the seed coat. Germination is triggered by absorption of water (imbibition) through the seed coat. Uneven seed-to-soil contact can interfere with imbibition and result in uneven germination.

The visual indicators of germination occur in a distinct sequence. The radicle root emerges first, near the tip end of the kernel, within two to three days in warm soils with adequate moisture. In cooler or drier soils, the radicle root may not emerge until one to two weeks after planting.

The coleoptile (commonly called the “spike”) emerges next from the embryo side of the kernel within one to many days of the appearance of the radicle, depending on soil temperature. The coleoptile initially negotiates its way toward the dent end of the kernel by virtue of the elongation of the mesocotyl. The coleoptile is a rigid piece of plant tissue that completely encloses the four to five embryonic leaves (plumule) that formed during grain development of the seed production year. The plumule leaves slowly enlarge and eventually cause the coleoptile to split open as it nears the soil surface.

The lateral seminal roots emerge last, near the dent end of the kernel. Even though these and the radicle root are technically nodal roots, they do not comprise what is typically referred to as the permanent nodal root system. The first set of so-called “permanent” roots begins elongating at approximately the V1 leaf stage (1 leaf with visible leaf collar) and is clearly visible by V2.

For more information on germination and emergence, browse these on-line articles:

Germination Events in Corn

The Emergence Process in Corn

Requirements for Uniform Germination and Emergence of Corn

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Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service