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StemsStems
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StemsStems
• A stem is the other structural axis for the plant after roots.
• It is composed of nodes and internodes.
• Nodes hold buds which can grow into leaves, flowers, cones, branches, etc…
• Internodes are the spaces between nodes.
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StemsStems
• A shoot is not the same as a stem! Shoots are any new plant growth, not just new stems.
• Stems are usually located above the surface, but there are some plants with underground stems.
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Stem functionsStem functions
• Stems have four main functions:
1) Support and elevation for leaves, flowers and fruits
2) Transport of materials between the roots and the shoots
3) Nutrient Storage
4) Annual, lateral, plant growth
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Types of StemsTypes of Stems
• Herbaceous: softer texture stems that die at the end of the growing season; non-woody.
• Woody: hard textured stems with secondary xylem
• Woody stems longer than 5m with a trunk make the plant a tree.
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Dicot StemsDicot Stems
• Pith in the center• Outside of stem is still
the epidermis• Lateral growth is due
to the vascular bundles in a ring
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Dicot StemsDicot StemsIF WOODY STEM:
• Each vascular bundle has a meristem between the xylem and phloem
• Secondary xylem grows to the inside, while secondary phloem grows to the outside
• The epidermis and cortex get destroyed as the secondary xylem and phloem grow.
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Dicot StemsDicot StemsThe plant produces a cork
cambium layer on the outside which replaces the epidermis.
• The outer region develops into the bark which protects the outside of the woody dicot.
• Secondary Xylem is known as heartwood, while secondary phloem is known as sapwood.
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Monocot StemsMonocot Stems
• Have vascular bundles throughout, though usually concentrated near the edge.
• Rarely produce secondary growth as they are rarely woody.
• Grow laterally due to anomalous growth.
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Specialized StemsSpecialized Stems
• Bulb: short underground stem with fleshy leaves attached (tulip, onion, daffodil)
• Climbing: stems that cling to or wrap around other plants or structures (ivies, vines)
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Specialized StemsSpecialized Stems
• Corm: short, enlarged, underground stem (gladiolus, crocus)
• Rhizome: a horizontal, underground stem used mainly in reproduction, but also in storage (ferns, iris)
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Specialized StemsSpecialized Stems
• Stolons/Runners: horizontal, above ground stems to produce new rooted plantlets when they touch the surface (strawberries, spider plants)
• Tuber: swollen, underground stems used for storage (potatoes)