Practical Assignment: Longitudinal Section (L.S.) of Sphagnum

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Aim

To study the longitudinal section (L.S.) of Sphagnum stem and leaf under the microscope and understand the structural features.

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Introduction

Sphagnum, commonly known as peat moss, is a genus of bryophytes. It plays a significant role in the formation of peat bogs and acts as a water reservoir due to its high water retention capacity. A longitudinal section (L.S.) of Sphagnum helps us observe the internal structure of the stem and leaves that support these functions.

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Materials Required

• Fresh or preserved Sphagnum specimen
• Compound microscope
• Razor blade
• Glass slides and coverslips
• Stains (e.g., safranin or glycerine)
• Forceps
• Brush
• Dropper

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Procedure

1. Take a fresh or preserved specimen of Sphagnum.
2. Use a razor blade to cut a thin longitudinal section (L.S.) of the stem and leaf.
3. Place the section on a glass slide with a drop of water or stain (safranin or glycerine) to improve visibility.
4. Gently place a coverslip over the section to avoid air bubbles.
5. Observe the prepared slide under the compound microscope.
6. Draw diagrams of what you observe and record the structural details.

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Observations

1. Stem (L.S.)

• The stem shows the following features:
• Cortex: Outer layer made up of large, dead hyaline cells (empty and capable of storing water).
• Central conducting strand: Inner layer consisting of narrow, living cells that transport water and nutrients.
• Stem surface: May have rhizoids, which aid in water absorption and attachment to surfaces.

2. Leaf (L.S.)

• The leaf exhibits a unique network structure:
• Hyaline cells: Large, empty cells with pores, facilitating water absorption and retention.
• Chlorophyllous cells: Small, living cells with chloroplasts, found between the hyaline cells, responsible for photosynthesis.
• Arrangement: The chlorophyllous cells form a network between hyaline cells, ensuring both photosynthesis and water storage.

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Comment

Sphagnum has a unique structure, adapted for both water storage and photosynthesis. The hyaline cells in the stem and leaf contribute to its ability to retain large amounts of water, helping it thrive in bogs. Meanwhile, the chlorophyllous cells allow photosynthesis to continue efficiently. These features explain Sphagnum’s ecological importance, such as in peat formation and water regulation in ecosystems.

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Conclusion

The longitudinal section of Sphagnum reveals a specialized structure comprising hyaline cells for water retention and chlorophyllous cells for photosynthesis. These features allow Sphagnum to survive in moist, boggy environments and play a crucial role in regulating water balance in ecosystems.

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