SEMESTER 3 Practical Science 1

Experiment 7

Topic : Investigating the structure of flowers, Angiospermatophyta.

Purpose :

A. To investigate the morphology of the Flame of the Forest (Delonix regia) flower and its relation to its functions

Theory:

A flower consists of whorls of modified leaves which collectively produce, protect and ensure the union of the gametes. The whorls are attached to a receptacle, the expanded end of the flower stalk. The parts of the flower from the outside to inside are calyx, corolla, androecium, and gynoecium.

There is a wide variation in flower structure. Flowers of different species may differ in the numbers, arrangement and the degree of the fusion of the component parts.

Radially symmetrical flowers are called actinomorphic and bilaterially symmetrical flowers are called zygomorphic flowers.

Floral diagram provides a plan of the flower as viewed from above. It looks like a diagrammatic cross-section.

If a bract, a leaf-like structure immediately beneath the flower, is present it should be facing you, the flower stalk should be furthest away and the main stem of the plant should be at the top of the flower. You will probably cut a cross-section of the ovary so that you can show the position of the ovules on the diagram. If the petals, sepals or stamens are joined, link them with simple brackets. If the stamens arise from the petals, link them with radial lines.

Figure 8.1: The two tpyes of symmetry found in flowers. The dotted lines indicated the planes through which the flowers can be cut so as to give two equal and opposite halves.

Figure 8.2: Three representations of the structure of the same flower

Apparatus and Materials

Flame of the Forest flowers A sharp scalpel/razor bladeHand lens

ProcedureCut the flower into two equal halves using a sharp scalpel. Make a large labeled drawing of the dissected flower as well as the floral diagram. State the scale of your drawing.

Drawing

Flame of the Forest flower

Scale …………………………B. To investigate the morphology of the orchid flower (Dendrobium) and its relation to

its function.

Apparatus and Materials

Orchid flowers A sharp scalpelHand lens

ProcedureCut the flower into two equal halves using a sharp scalpel. Make a large labeled drawing of the dissected flower as well as the floral diagram of the flower. State the scale of your drawing.

Drawing

Orchid flower

Scale …………………………

Questions

1. State the family, type of ovary, and the symmetry of both flowers being investigated.

Flame of the Forest Orchid

FamilyType of ovarySymmetry of flower

2. What are the special features, which both flowers have to ensure the success of their fertilization process?

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