A stem consists of nodes, internodes,
and axillary bud. Nodes are regions where leaves and axillary
buds attach to stems, and internodes are the parts of stems
between nodes. Stems perform three important
Support – stems support the aerial structures of the plant. Leaves, flowers and fruit
Storage – stems can store large amounts of starch and water.
Conduction – stems transport water, sugar and minerals between different parts of the plant. In herbaceous(non-woody) plants, stems are green and photosynthetic.
Young stems are surrounded by a
transparent epidermis that is usually one cell thick and often bears
trichomes. The xylem and phloem (the “plumbing system”)
are located in vascular bundles. Phloem forms on the outside
of the bundle, whereas xylem forms on the inside (towards the stems
centre). A group of fibers (sclerenchyma) is often found next to
each vascular bundle, with each fiber surrounded by a thick cell
wall. In dicots, vascular bundles occur in a ring surrounding a pith
composed of parenchyma cells on the inside, and cortex external to the ring. A layer of meristematic cells is
sandwiched between the xylem and phloem within each vascular bundle
of a dicot stem, called the vascular cambium. These vascular
tissues are produced during secondary growth, as the plant's
stem grows thicker.