Carry out investigation related to reproduction in flowering plants (flower structure and embryo)

Investigation: Reproductive Structures of a Flowering Plant

Aim: To identify and draw the male and female reproductive parts of a flower and locate the ovule (where the embryo develops).

Materials and Apparatus:

• A fresh Hibiscus flower (or any complete flower)
• Razor blade or sharp knife
• Forceps
• Hand lens (magnifying glass)
• White paper
• Microscope (if available)
• Digital device (for ICT simulation)

Safety Note: Handle the razor blade carefully to avoid cuts. Always cut away from your body.

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Method (Practical Work)

Part 1: Observing the External Features

1. Place the flower on the white paper.
2. Use the hand lens to observe the flower.
3. Identify and note the following parts:
   • Sepals: Green leaf-like parts at the base (calyx).
   • Petals: The bright colored parts that attract insects (corolla).
   • Stamens: The male reproductive organs. They consist of a stalk (filament) and a yellow tip (anther). The anther produces pollen grains.
   • Pistil (Carpel): The female reproductive organ in the center. It has a sticky top (stigma), a tube (style), and a swollen base (ovary).

Part 2: Making a Longitudinal Section (L.S.)

1. Use the forceps to hold the flower steady.
2. With the razor blade, carefully cut the flower lengthwise through the center of the ovary and style.
3. Place one half on the paper.
4. Observe the cut surface with a hand lens.
5. Identify: The ovary contains small bean-shaped structures called ovules. The ovules are attached to the ovary wall.

Part 3: Making a Cross Section (C.S.)

1. Cut the ovary of the other half of the flower horizontally.
2. Observe the cut surface.
3. You will see the arrangement of the ovules inside the ovary.

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Observations and Labelled Diagrams

When investigating biologically, you must record what you see.

• Drawing: Draw a clear outline of the longitudinal section of the flower. Use single, unbroken lines. Do not shade.
• Labels: Label the following: Petal, Sepal, Stamen, Anther, Filament, Stigma, Style, Ovary, Ovule.

What to look for:

• The Stamen is the male part (produces pollen).
• The Pistil is the female part (contains the ovules).
• The Ovule is located inside the Ovary.

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Understanding the Embryo

The competency requires you to investigate the embryo.

1. The ovule you observed in the ovary is the structure that becomes the seed after fertilization.
2. Inside each ovule is the embryo sac. During fertilization (after pollen lands on the stigma), a male gamete fuses with the egg cell to form a zygote.
3. This zygote divides repeatedly to form the embryo. The embryo consists of the plumule (young shoot), radicle (young root), and cotyledons (seed leaves).
4. To see the embryo clearly: You would need to slice open a mature ovule (seed) under a microscope. In a fresh flower, focus on identifying the ovule correctly as the site where the embryo will develop.

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ICT-Based Learning (Extension)

If a microscope is not available, or for deeper understanding:

1. Access a digital simulation of a flower dissection (search for "flower structure virtual lab" or use educational apps).
2. Use the simulation to zoom inside the ovule to observe the embryo sac and the position of the egg cell.
3. Compare the digital image with your hand-lens drawing to ensure your identification of parts is accurate.

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Real-life application

Understanding flower structure is vital for Tanzanian farmers and gardeners. For example, when growing papaya or pawpaw, knowing that these plants often have separate male and female flowers (unisexual) helps a farmer plant enough seedlings to ensure cross-pollination and fruit set. Similarly, understanding that the embryo develops inside the ovule helps in seed selection for planting.