Plumule

The plumule is an organ found in the embryo of vascular plants. It is the terminal bud of the embryonic shoot; it contains the apical meristem, which includes the leaf and bud primordia as they develop into the first leaves and buds. It is subsequently one of the most vital organs in the embryo during development.

The embryo has multiple ways of protecting the plumule during germination, though they differ between angiosperm clades:

• In eudicots, as the roots develop from the radicle, the plumule is pulled upwards and backwards between the cotyledons. The radicle curves downward, and the growing roots anchor into the soil, forming a “hook” shape in the exposed hypocotyl or root aboveground. The plumule eventually points up straight, allowing for the shoot to grow upwards.
• In monocots, the shoot develops directly upwards without the use of a “hook”. The plumule is enclosed by the coleoptile, protecting it as it emerges through the soil while the roots grow. The plumule is covered by the leaf sheath, created by the coleoptile, and by further leaves as they grow.