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Questions and Answers
What is the primary function of the pith in a plant stem?
Which type of cells provides flexibility in the stem?
Why do stems of plants not have an endodermis?
What role does the vascular bundle play in a plant stem?
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What can be inferred from counting the annual rings of a tree?
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What is the function of the cambium in the vascular bundle?
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Where are vascular bundles located in dicot stems?
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How do axillary buds contribute to plant growth?
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Which part of the stem is responsible for the plant's vertical growth?
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What is the primary role of lenticels in the stem?
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What determines where leaves attach to the stem?
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What leaves a mark on the stem after a leaf has fallen off?
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In what way do the internal structures of monocot and dicot stems differ?
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Study Notes
Importance of Stem
- Provides support for the plant
- Enables plant growth
- Conducts water and nutrients throughout the plant
Stem Development
- Stems develop from the plumule of the germinating seed.
- The plumule is the part of the seed embryo that becomes the shoot of the plant.
External Stem Structure
- Terminal Bud: Located at the stem's tip, it contains developing leaves and flowers. It's responsible for the vertical growth of the plant.
- Axillary Bud: Found at the junction of the leaf and stem. They're dormant buds and can develop into branches, flowers, or leaves.
- Node: Point on the stem where leaves or buds emerge. Important for leaf attachment and branching.
- Internode: Section of the stem between two nodes. Internode length affects the plant's overall height.
- Lenticel: Small, porous openings in the bark of woody stems, allowing gas exchange.
- Leaf Scar: Mark left on the stem after a leaf falls off, indicating where leaves were attached.
- Bundle Scar: Small marks inside the leaf scar, indicating the vascular bundles.
Internal Stem Structure
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Vascular Bundles: Contain vascular tissues (xylem & phloem) responsible for water and food transport.
- Monocot Stems: Vascular bundles scattered throughout the stem. Often found in both the periphery and central parts of the stem.
- Dicot Stems: Vascular bundles arranged in a ring near the periphery of the stem. The center has no vascular bundles.
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Cambium: Actively dividing cells found between the xylem and phloem. Produces new xylem and phloem cells for stem growth.
- The cambium produces xylem towards the center and phloem towards the outside of the stem.
- Epidermis: The outermost layer, protecting the plant from damage and water loss. Has a waxy coating called the cuticle, reducing water loss.
- Pith: The central part of the stem, made of soft, spongy parenchyma cells. Stores nutrients and water.
- Collenchyma Cells: Found under the epidermis, providing flexibility.
- Sclerenchyma Cells: Provide structural support by forming tough fibers that strengthen the stem.
- Cortex: Layer between the epidermis and vascular bundles, composed of parenchyma, collenchyma, and sclerenchyma cells depending on the plant.
- Parenchyma Cells: The most common plant cell type, found throughout the stem. Involved in photosynthesis and storage.
Stem Differences from Roots
- Stems do not have an endodermis.
- The vascular bundle and epidermis control water, nutrient transport, and protection in stems, making an endodermis unnecessary.
Determining Tree Age
- Count the annual rings. One ring represents one year of growth.
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Description
Explore the essential functions and structures of plant stems in this quiz. Learn about the role of the stem in providing support and conducting water and nutrients, as well as the various parts such as terminal and axillary buds, nodes, and internodes. Test your knowledge on how stems develop from germinating seeds.
