Summarizing Stems


The stem of a plant bears the leaves, flowers, and fruits. Stems are characterized by the presence of nodes (the points of attachment for leaves or branches) and internodes (regions between nodes).

Plant organs are made up of simple and complex tissues. The stem has three tissue systems: dermal, vascular, and ground tissue. Dermal tissue is the outer covering of the plant. It contains epidermal cells, stomata, guard cells, and trichomes. Vascular tissue is made up of xylem and phloem tissues and conducts water, minerals, and photosynthetic products. Ground tissue is responsible for photosynthesis and support and is composed of parenchyma, collenchyma, and sclerenchyma cells.

Primary growth occurs at the tips of roots and shoots, causing an increase in length. Woody plants may also exhibit secondary growth, or increase in thickness. In woody plants, especially trees, annual rings may form as growth slows at the end of each season. Some plant species have modified stems that help to store food, propagate new plants, or discourage predators. Rhizomes, corms, stolons, runners, tubers, bulbs, tendrils, and thorns are examples of modified stems.


apical bud

bud formed at the tip of the shoot

axillary bud

bud located in the axil: the stem area where the petiole connects to the stem


tough, waterproof, outer epidermal layer of cork cells


modified underground stem that consists of a large bud surrounded by numerous leaf scales

collenchyma cell

elongated plant cell with unevenly thickened walls; provides structural support to the stem and leaves

companion cell

phloem cell that is connected to sieve-tube cells; has large amounts of ribosomes and mitochondrion


rounded, fleshy underground stem that contains stored food


ground tissue found between the vascular tissue and the epidermis in a stem or root


single layer of cells found in plant dermal tissue; covers and protects underlying tissue

guard cells

paired cells on either side of a stoma that control stomatal opening and thereby regulate the movement of gases and water vapor


region between nodes on the stem


opening on the surface of mature woody stems that facilitates gas exchange


point along the stem at which leaves, flowers, or aerial roots originate

parenchyma cell

most common type of plant cell; found in the stem, root, leaf, and in fruit pulp; site of photosynthesis and starch storage


outermost covering of woody stems; consists of the cork cambium, cork cells, and the phelloderm


ground tissue found towards the interior of the vascular tissue in a stem or root

primary growth

growth resulting in an increase in length of the stem and the root; caused by cell division in the shoot or root apical meristem


modified underground stem that grows horizontally to the soil surface and has nodes and internodes


stolon that runs above the ground and produces new clone plants at nodes

sclerenchyma cell

plant cell that has thick secondary walls and provides structural support; usually dead at maturity

secondary growth

growth resulting in an increase in thickness or girth; caused by the lateral meristem and cork cambium

sieve-tube cell

phloem cell arranged end to end to form a sieve tube that transports organic substances such as sugars and amino acids


modified stem that runs parallel to the ground and can give rise to new plants at the nodes


modified stem consisting of slender, twining strands used for support or climbing


modified stem branch appearing as a sharp outgrowth that protects the plant


xylem cell with thick secondary walls that helps transport water


hair-like structure on the epidermal surface


modified underground stem adapted for starch storage; has many adventitious buds

vessel element

xylem cell that is shorter than a tracheid and has thinner walls

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