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Stems Stems

Stems. Stems 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

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Page 1: Stems. Stems 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

StemsStems

Page 2: Stems. Stems 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

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.

Page 3: Stems. Stems 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

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.

Page 4: Stems. Stems 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

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

Page 5: Stems. Stems 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

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.

Page 6: Stems. Stems 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

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

Page 7: Stems. Stems 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

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.

Page 8: Stems. Stems 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

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.

Page 9: Stems. Stems 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

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.

Page 10: Stems. Stems 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

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)

Page 11: Stems. Stems 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

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)

Page 12: Stems. Stems 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

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)