stems

• Butcher's broom (*Ruscus aculeatus*)
• Stems are the “central axis” of the plant where all the other parts are attached and are connected to the leaves and roots.
• The primary functions of stems include axial support, holding other organs in place, and serving as conduits or channels of fluids.
• Secondary functions of stems include food storage, asexual reproduction, site of photosynthesis, additional support, and protection or defense.
• Monocot plants may have obvious nodes, such as those seen in bamboo, and have a smooth epidermis with some of the leaf sheaths visible.
• Dicot plants have a thick, wrinkled periderm outside the stem and retain marks of the previous year’s growth.
• Woody stems have parts such as secondary xylem, which is responsible for water and nutrient transportation, and summer wood, an area of dark wood in a ring formed during the summer when the xylem cells are smaller in diameter.
• Spring wood is light colored wood formed during the spring when the xylem cells are larger in diameter (vessel elements).
• Sapwood, also known as functioning xylem, is lighter in color and is found closest to the vascular cambium.
• Heartwood is the older xylem, can be recognized by its darker color, and is found mostly towards the center of the stem.
• Vascular cambium is a layer of meristematic tissue that produces the secondary xylem inside and secondary phloem outside in a process called secondary growth.
• Bark is all the living tissues surrounding the xylem of the woody stems.
• Periderm is an armor protecting the plant's inner tissues from biotic and abiotic stress.
• Modern club mosses (Lycopodiopsida) are an example of Plectosteles.
• Ectophloic Siphonosteles have phloem to the exterior of xylem, for example, the royal fern (*Osmunda* sp.) rhizome.
• Periderm Layers include Cuticle, Epidermis, Phellem (Cork), Cork Cambium (Phellogen), Phelloderm, and Cortex.
• Siphonosteles have the central pith and have a pith in the center of their stems, surrounded by a cylinder of various designs containing the vascular tissue.
• Types of Stele include Protosteles, Actinosteles, Plectosteles, and Siphonosteles.
• Plectosteles have interconnected plate-like regions of xylem surrounded by and immersed in phloem tissue.
• Solenostele is the most basic of siphonosteles, with a central core of pith enclosed in a cylinder of vascular tissue.
• Amphiphloic Siphonosteles have phloem both interior and exterior to the xylem, for example, the maidenhair fern (*Adiantum pedatum*) rhizome.
• Types of Protosteles include Haplostele and Actinostele.
• Stele is the cylinder of vascular tissue in the center of a root or stem, and there is significant variation in the arrangement of xylem and phloem.
• The cell differentiation of the meristematic cells gives the phelloderm (inner part) and the phellem (outside part).
• Dictyostele is a variation of the solenostele caused by multiple leaves and short internodes, for example, the fern (*Polypodium* sp.) rhizome.
• Secondary Phloem is the vascular tissue produced by the vascular cambium outside of the meristematic tissues.
• Types of Siphonosteles include Solenostele, Amphiphloic, and Dictyostele.
• Cork Cambium (Phellogen) is a meristematic tissue that produces some of the cork cells.
• Protosteles have no central pith and have xylem located as a solid mass in the center with no pith.
• Eudicots have a eustele with a ring of bundles.
• Discrete vascular bundles are arranged in a field of pith; eudicots have a eustele with a ring of bundles.
• Examples of plants with actatostele include red clover (*Trifolium pratense*) and greenbrier (*Smilax* sp.).
• Actatostele is the most common stelar arrangement in stems of monocot seed plants.
• Stems are the central axis of the plant where all the other parts are attached or connected, including the leaves and roots.
• The primary functions of stems include axial support and conduction of fluids.
• Secondary functions of stems include food storage, asexual reproduction, and site of photosynthesis.
• Stem morphology can vary depending on the type of plant, for example, a monocot plant may have obvious nodes, such as those seen in bamboo, while a dicot plant has a thick, wrinkled periderm outside the stem.
• A woody stem bud is a small lateral or terminal protuberance on the stem of a vascular plant that may develop into a flower, leaf, or shoot.
• Thorns: Sharp modified stems subtended by a leaf; e.g. Bougainvillea, Rosa.
• Suckers: Horizontal growth under the soil that emerges upwards; e.g. Banana, Bamboo.