Temporary Mount: Leaf Peel (Stomata) MCQs Quiz | Class 10

This quiz is designed for Class X Science (Code 086), focusing on Practicals (Unit II). The topic is “Temporary Mount: Leaf Peel (Stomata)”, covering its preparation, observation, and labeled diagram. Test your knowledge on this important practical by attempting the questions, then submit to check your score and download a detailed answer PDF for revision.

Educational Content: Temporary Mount of Leaf Peel (Stomata)

The temporary mount of a leaf peel is a fundamental practical in biology, allowing students to observe microscopic structures like stomata, guard cells, and epidermal cells. This experiment provides direct insight into plant anatomy and physiology, particularly gas exchange and transpiration.

I. Preparation of Temporary Mount: Leaf Peel

The process of preparing a temporary mount involves several crucial steps to ensure clear observation:

  1. Selecting a Healthy Leaf: Choose a fresh, healthy leaf, usually from a monocot like lily or dicot like Tradescantia, as their epidermal peels are relatively easy to remove. The lower surface often has more stomata.
  2. Peeling the Epidermis: Gently tear the leaf diagonally from the lower side. A transparent, thin membrane (epidermal peel) can often be pulled off using forceps. This peel is the focus of observation.
  3. Mounting in Water: Immediately place the peel in a watch glass containing water to prevent it from drying or curling.
  4. Staining (Optional but Recommended): Transfer the peel to a watch glass with a few drops of a stain like Safranin or Methylene Blue for about 1-2 minutes. This makes the cell structures, especially nuclei and chloroplasts in guard cells, more visible. Wash excess stain with water.
  5. Mounting on a Slide: Place a drop of glycerine or water in the center of a clean glass slide. Carefully transfer the stained peel to this drop using a brush, ensuring it lies flat without folds. Glycerine is preferred as it prevents drying and air bubbles.
  6. Cover Slipping: Gently lower a coverslip over the peel using a needle, starting from one edge. This technique helps to avoid trapping air bubbles, which can obstruct observation. Remove any excess water/glycerine with blotting paper.

II. Observation Under the Microscope

After preparation, the slide is observed under low and then high power of a compound microscope.

  • Epidermal Cells: These are the outermost, irregularly shaped (in dicots) or elongated (in monocots) cells that form the boundary of the leaf. They are tightly packed and typically lack chloroplasts.
  • Stomata: These are tiny pores on the leaf surface, essential for gas exchange. Each stoma is surrounded by two specialized kidney-bean shaped or dumbbell-shaped cells called guard cells.
  • Guard Cells: Unlike other epidermal cells, guard cells contain chloroplasts and are responsible for regulating the opening and closing of the stomatal pore. Their turgidity changes influence the stomatal aperture.
  • Chloroplasts: Observed specifically within the guard cells, these organelles are responsible for photosynthesis.

III. Labeled Diagram of Stomata

A well-labeled diagram of a stoma typically includes:

  • Stomatal Pore: The central opening.
  • Guard Cells: The two cells flanking the pore, showing their characteristic shape (kidney or dumbbell) and presence of chloroplasts.
  • Epidermal Cells: Surrounding the guard cells.
  • Chloroplasts: Small green dots within the guard cells.
  • Nucleus: Present in guard cells.

Understanding the structure helps explain the function of stomata in processes like transpiration and photosynthesis.

Quick Revision Points

  • Leaf peel reveals epidermal cells, stomata, and guard cells.
  • Stomata are microscopic pores for gas exchange.
  • Guard cells regulate stomatal opening/closing.
  • Safranin or Methylene Blue stains make structures more visible.
  • Glycerine is used as a mounting medium to prevent drying.
  • Dicot guard cells are kidney-shaped; monocot guard cells are dumbbell-shaped.

Comparison of Dicot and Monocot Stomata

Feature Dicot Stomata Monocot Stomata
Guard Cell Shape Kidney-shaped Dumbbell-shaped
Arrangement Scattered, irregular Often in rows
Number on Surfaces More on lower surface Often equal on both surfaces

Practice Questions

  1. Why is it important to prevent air bubbles while mounting the leaf peel?
  2. What is the primary function of stomata in a plant leaf?
  3. If you observe a leaf peel under a microscope and find dumbbell-shaped guard cells, what kind of plant is it likely from?
  4. Why do guard cells contain chloroplasts while most other epidermal cells do not?
  5. What would be the likely effect on a plant if its stomata remained permanently closed?