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A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence (flowers), cones or other stems etc. The internodes distance one node from another. The term shoots is often confused with stems; shoots generally refer to new fresh plant growth and does include stems but also to other structures like leaves or flowers. The other main structural axis of plants is the root. In most plants stems are located above the soil surface but some plants have underground stems.
Stems have four main functions which are:
•Support for and the elevation of leaves, flowers and fruits. The stems keep the leaves in the light and provide a place for the plant to keep its flowers and fruits.
•Transport of fluids between the roots and the shoots in the xylem and phloem.
•Storage of nutrients.
•The production of new living tissue. The normal life span of plant cells is one to three years. Stems have cells called meristems that annually generate new living tissue.
Stems are often specialized for storage, asexual reproduction, protection or photosynthesis, including the following:
•Acaulescent - used to describe stems in plants that appear to be stemless. Actually these stems are just extremely short, the leaves appearing to rise directly out of the ground, e.g. some Viola species.
•Arborescent - tree like with woody stems normally with a single trunk.
•Bud - an embryonic shoot with immature stem tip.
•Bulb - a short vertical underground stem with fleshy storage leaves attached, e.g. onion, daffodil, tulip. Bulbs often function in reproduction by splitting to form new bulbs or producing small new bulbs termed bulblets. Bulbs are a combination of stem and leaves so may better be considered as leaves because the leaves make up the greater part.
•Caespitose - when stems grow in a tangled mass or clump or in low growing mats.
•Cladophyll - a flattened stem that appears leaf like and is specialized for photosynthesis, e.g. asparagus, cactus pads.
•Climbing - stems that cling or wrap around other plants or structures.
•Corm - a short enlarged underground, storage stem, e.g. taro, crocus, gladiolus.
•Decumbent - stems that lie flat on the ground and turn upwards at the ends.
•Fruticose - stems that grow shrub like with woody like habit.
•Herbaceous - non woody, they die at the end of the growing season.
•Pseudostem - A false stem made of the rolled bases of leaves, which may be 2 or 3 m tall as in banana
•Rhizome - a horizontal underground stem that functions mainly in reproduction but also in storage, e.g. most ferns, iris
•Runner (plant part) - a type of stolon, horizontally growing on top of the ground and rooting at the nodes, aids in reproduction. e.g. strawberry, spider plant.
•Scape - a stem that holds flowers that comes out of the ground and has no normal leaves. Hosta, Lily, Iris.
•Stolon - a horizontal stem that produces rooted plantlets at its nodes and ends, forming near the surface of the ground.
•Spine (botany) - a modified leaf with a sharp point and rounded shape, used for protection against animals. e.g. honey locust, hawthorn.
•Thorn - a modified stem protruding from the axils of a plant. Used for protection against animals, though animals have adapted. (i.e. an animal will have a long tongue to reach past the thorns)
•Tree - a woody stem that is longer than 5 meters with a main trunk.
•Tuber - a swollen, underground storage stem adapted for storage and reproduction, e.g. potato.
•Woody - hard textured stems with secondary xylem
  • Last Modified: Saturday 16 February 2019, 08:37:10.