4.4 Plant organs: flowers

Natural sciences

Grade 9

Plants

Module 29

Plant organs: flowers

Flowering plants (Angiosperms) are the most prolific and successful group of plants on earth. Their secret is partly related to the way in which they are propagated. The key to this secret lies in the structure of the flowers and in how they operate. The fact that propagation is SEXUAL , adds to their success.

The flower is a structure that contains both the male and female structures of the plant. Male and female structures do sometimes occur in separate plants, but they mostly occur in a single bisexual (gynandrous) flower.

Activity 1:

To describe flowers as structures for propagation

[lo 2.2, 2.3]

Assignment 1:

1. Take a flower and make a lengthwise cut through it to divide it in two. The Petunia is a good example to use. Make a drawing of the flower, showing all its parts (without labels).

Name the functions of each of the following (find the answers yourself or enlist the educator's help):

1. Try to identify all the parts listed in no. 2, in your sketch for no. 1.

4. Answer the following questions:

What is the term we use to refer to the group of plants that bear flowers?

Are all types of flowers equally colourful? Provide an explanation.

Are all flowers fragrant? Provide an explanation.

What is the function of all flowers?

Assessment: Sketches

Were you able to distinguish the basic differences?

[LO 2.2; LO 2.3]

Activity 2:

To describe pollination as a necessary process for the propagation of flowering plants

[lo 1.1, 1.2, 13, 2.4]

Pollination is the process by which a mature (ripe) grain of pollen lands on the mature pistil of a similar plant.

Assignment 1:

1. Why must the grain of pollen be mature?

2. Why should the pistil be mature and receptive?

3. Why must the plant that is pollinated be similar to the one from which the pollen is derived?

The pollen of each type of plant has a unique structure and are microscopically different from the pollen of the plants. This means that a grain of pollen has to fit like onto the pistil like a key in a lock.

A ripe grain of pollen will begin to germinate as soon as it has landed on an appropriate surface.

Assignment 2:

Undertake an investigation to obtain information about the pollen and pistils of different kinds of plants.

Assemble a sheet of sketches of the different kinds of pollen and pistils that you discover.

Assessment: Investigation

Were you able to distinguish basic differences?

[LO 1.1; 1.2; 1.3]

Assignment 2:

Design a flower of your own with the help of the following guidelines:

Your flower is of a very rare, exotic type. It grows in the upper reaches of mountains where there are hardly any insects. It has to rely on wind for pollination. The mechanism by which pollination occurs will be the absolute deciding factor for what the flower's structure will be like.

Assessment: Flower design

Were you able to distinguish basic differences?

[LO 2.4]

Activity 3:

To describe fertilisation as a necessary process for the propagation of flowering plants

[lo 2.1, 2.2]

We have mentioned that two main processes during reproduction occur, namely pollination and fertilisation. We know what pollination is, and that the ultimate goal of the grain of pollen is to reach the mature ovule to fertilise it.