Stems are one of the three basic plant organs, and consist of an alternating system of nodes (where leaves attach) and internodes (regions of the stem that span between nodes).

Some plants have evolved to have stems with additional functions, such as the ability to store food or to participate in asexual reproduction. These modified stems include rhizomes, bulbs, tubers and stolons.  

A rhizome is a horizontal shoot of the plant that grows just below the surface. Vertical shoots (and resulting leaves) grow from axillary buds on the rhizome. Examples of plants with rhizomes include irises, hops, and asparagus. 

The root cap occurs on the end of any root. It protects the tip of a plant's root. Specifically, it protects the apical meristem of the plant, which lengthens the root and helps it grow. Also root cap secretes a polysaccharide slime called mucilage. The zone of elongation does occur in roots, but it is not contained to the root cap. The root cap grows towards the pull of gravity. The root cap occurs only on the tip of the root, not over the entire surface of the root. These cells only protect the root; they are not xylem cells, which function in transport of water and nutrients from the roots up to the leaves.

Roots are usually underground and not exposed to sunlight, do not usually contain chlorophyll, thus they do not perform photosynthesis. However, roots do provide stabiity, obtain water and nutrients from the soil, and store carbohydrates.

Parenchyma cells make up a type of ground tissue in plants. Parenchyma cells compose most of the soft tissues in plants including leaves, roots, stems, and seeds. The functions of parenchyma cells include photosynthesis, storage, and wound repair.

Meristem tissue contains undifferentiated cells and allows for plant growth. Apical meristems are found in areas of growth, which include the shoot and roots—cells in these tissues divide rapidly.

The vascular cambium is a type of secondary meristem tissue located between the xylem and phloem of the stems and roots. Secondary meristem tissues are responsible for lateral growth; more specifically, the vascular cambium is responsible for secondary xylem and phloem development.

The cork cambium is a type of secondary meristem tissue found in the periderm. Cork cambium controls lateral growth; specifically, it is the source of secondary epidermis growth.

Cutting into the trunk of a tree to create a horizontal cross section reveals rings, called annual growth rings. These rings show new vascular cambium growth over the course of a year. Differences in growth speed change the size of the growth rings.

The receptacle is the part of an angiosperm out of which the flower grows; thus, the receptacle is at the top of the stem.

The carpel is a part of the female angiosperm reproductive system. The carpel includes the ovary, ovules, style, and stigma. Flowers may have several carpels clustered into a pistil.