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STRUCTURE OF STEM

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1. Nodes:

Points on the stem where leaves, branches, or other structures are attached.

Serve as attachment points for leaves, branches, flowers, or other organs.

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2. Internodes:

The regions between two consecutive nodes.
Contribute to the overall lengthening of the stem.

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3. Stem Buds:

Small, undeveloped shoots that can give rise to leaves, branches, or flowers.

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Types: Apical Bud

Located at the tip of the stem; responsible for primary growth.

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Axillary Bud

Found in the axil (angle between the leaf and the stem); can develop into branches or flowers.

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4. Leaves:

Attached to nodes along the stem.

Primary sites for photosynthesis, contributing to the production of carbohydrates.

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5. Leaf Scars:

Marks left on the stem after a leaf falls off.
Indicate the former attachment point of a leaf and serve as a site for new bud development.

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6. Lenticels:

Small, raised areas on the stem's surface.
Facilitate gas exchange, allowing the exchange of oxygen and carbon dioxide between the internal tissues and the external environment.

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7. Stipules:

Small, leaf-like structures at the base of the petiole (leaf stalk).

Provide support and protection for the developing bud.

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8. Bark:

Outer protective covering of the stem.
Layers:
Cork (Periderm): Secondary protective layer produced by the cork cambium.
Phloem: Vascular tissue responsible for the transport of organic nutrients.

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9. Bud Scales:

Protective scales covering buds during winter or dormancy.

Shield the delicate bud from harsh environmental conditions.

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10. Thorns and Prickles:

Modified stems that are sharp-pointed.
Keep herbivores away and safeguard the plant.

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11. Stem Color

Stems can vary in color, ranging from green to brown or woody.
Reflects the presence of chlorophyll in green stems, which can contribute to photosynthesis.

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12. Stem Surface:

Texture and features on the stem's surface, such as grooves or ridges can influence water runoff, gas exchange, and provide structural support.

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FUNCTIONS OF PLANT STEM

Plant stems aid in the elevation and support of leaves, fruits and flowers.
The stems give the plant a place to hold its flowers and fruits and also keep the leaves in the light.
The stem tendrils of cucumber, grapevine and watermelon are used as support structures.

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It is also a nutrient-storing structure.
Tuber (potato), rhizome (ginger), bulb (onion), and corm (colaqocasia) are stem modifications for food storage.

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It also helps in the transportation of minerals and water between the xylem and phloem in the roots and the branches.

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Stems also play a vital role in protecting the plant.
Citrus and Bougainvillaea stem axillary buds grow into sharp thorns as a defence.
They guard the plants against animals.

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It functions in creating new living tissue.

Plant cells typically last one to three years.

Meristem cells found in stems produce new living tissue every year.

Likewise, the lateral branches of jasmine, mint and the underground grass stems function as vegetative reproductive structures.

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Another notable function of plant stem is food assimilation.

The flattened stem of the opuntia performs photosynthesis and contains chlorophyll.