The plumule eventually grows into the leafy portion of a plant. Within the plant embryo, three parts emerge: the radicle, the hypocotyl and the plumule. The radicle becomes the root, the hypocotyl becomes the stem and the plumule turns into the foliage, according to Botanical Online.
After an ovule undergoes fertilization, a seed develops, growing a protective layer known as the testa around the developing embryo. This embryo contains the three parts listed above. Within a short time after fertilization, the plumule becomes visible with at least two leaves that have a growing point held between them.
While the formation of a solid root system is important, the development of the plumule is also instrumental in the plant's eventual thriving or failure. If the plumule develops in a normal way, the shoot emerges from the seed and works its way up through the soil and into the atmosphere. A healthy plumule develops cotyledons, a special type of leaf that holds seeds; this is one of the most important ways that these plants germinate.
Because these seeds are crucial to the spread of that particular species, a plumule that fails to thrive not only threatens the health of that particular plant but the very existence of dozens, if not hundreds, more down the line.