This question is influened by the trees growing straight debate…
When a tree grows from a seed, let’s say an acorn, what happens to the acorn? Does the acorn literally grow into the tree, or does the tree grow out of it? If the latter, can the acorn still be found underneath the mighty Oak, perhaps warped and twisted out of recognition but with it’s original atoms still grouped together as they were when they first dropped from their parent tree?
My guess is that it is used as a nutrient base to feed the seedling. Whatever is left over after feeding the seedling and establishing a root base to feed from the soil, it would probably just decompose.
My WAG.
The tree grows out of the acorn. When a seed germinates the outer coat splits open and a stem and roots emerge. The nutrients necessary for this growth are contained in the inner part of the seed (the cotyledon(s) or endosperm, depending on the seed type) and that inner part does, in a sense, become the plant. The outer part of the seed, the part that makes it look like an acorn, a bean, a pea, or a sunflower seed, has served its purpose-protecting the inner parts-and falls away to decompose.