The root and shoot systems of plants usually look quite different. This is partly because they form different kinds of structures.

For example, root systems consist generally of only one type of structure: roots. Main root axes may branch to form branch root axes and these, in turn, may also branch to form a root system that is typically ramified throughout the soil in the area where the plant is growing.

In contrast, the shoot systems of seed plants tend to have much greater morphological complexity than root systems. Shoot systems are constructed of two basic morphological components: stems and leaves. The stem is typically a cylindrical axis, such as we find in asparagus. Leaves are attached to stems at regions called nodes. We can readily find the nodes on asparagus stems by locating where the small triangular leaves are attached. The portion of the stem between two adjacent nodes is called an internode.

Asparagus

Nodes of asparagus stem

Stems can take various forms among the seed plants. We need only think about the differences between the trees and the grass in yards to recognize the great diversity of stems that are possible. Using our grocery store vegetables, we can compare the typical stem of asparagus to the more distinctive kohlrabi.

Kohlrabi

Swollen storage stem of kohlrabi

Kohlrabi produces stems that are nearly spherical. They are like carrots in some ways because they are specialized for nutrient storage: The stems of kohlrabi expand outward as much as upward during their growth because sugars made by photosynthesis in the leaves are transported to the stem, where they are stored. Because of the relatively limited growth in the length of the kohlrabi stem, we find that its internodes are very short and the nodes, where leaves are positioned, are close together.