R. L. (Bob) Nielsen, Extension Agronomist,
Department of Agronomy, Purdue University
Germination is the renewal of enzymatic activity that results
division and elongation and, ultimately, embryo emergence through
coat. Germination is triggered by absorption of water (imbibition)
the seed coat. Uneven seed-to-soil contact can interfere with imbibition
result in uneven germination.
The visual indicators of germination occur in a distinct sequence.
radicle root emerges first, near the tip end of the kernel, within
three days in warm soils with adequate moisture. In cooler or drier
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
depending on soil temperature. The coleoptile initially negotiates
toward the dent end of the kernel by virtue of the elongation of
mesocotyl. The coleoptile is a rigid piece of plant tissue that
encloses the four to five embryonic leaves (plumule) that formed
grain development of the seed production year. The plumule leaves
enlarge and eventually cause the coleoptile to split open as it
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
The first set of so-called “permanent” roots begins
approximately the V1 leaf stage (1 leaf with visible leaf collar)
clearly visible by V2.
For more information on germination and emergence, browse these
Germination Events in Corn
The Emergence Process in Corn
for Uniform Germination and Emergence of Corn