Lesson Overview
This lesson is an introduction to flowers. It covers the basic flower parts and their functions.
Goals for this lesson
- understand the different parts and structures of a flower
- understand the functions of the basic flower parts
Tasks
- read the information below
- complete the worksheet using the samples in the greenhouse
- turn the worksheet into your folder
Vocabulary (note: while it is not necessary to submit written definitions of these
words for this lesson, you are responsible for knowing what they mean.) pollination,
fertilization, sepals, petals, stamen, pistil, filament, anther, stigma, style, ovary,
Reading
Most people enjoy the beauty of a flower. From the flower's perspective this beauty is necessary to attract insects. Most plants rely on insects or other animals for pollination. Pollination is the process in which pollen cells are transferred to the female plant parts and the eggs are fertilized. This is the beginning of fruit and seed production in a plant. In order for plants to be assured a continued existence the flowers and the processes of pollination and fertilization must be perpetuated.
Parts of the Flower
Flowers differ in such features as size, shape, and color but all flowers contain the same basic parts. These parts are necessary for the production of seeds. Seeds are the most common way that plants are propagated. Seeds are produced by a sexual process called fertilization with a male and a female parent involved. A complete flower has both male and female parts and only one parent is needed. An incomplete flower has either male or female parts but not both. Plants with incomplete flowers require two parents. The complete flower contains four main parts: sepals, petals, stamen, and pistil as shown in the diagram below.
The sepals are green leaflike parts of a flower that cover and protect the flower bud before it opens.
The petals are actually leaves but are generally known as the most colorful and striking part of the flower. The bright colors of the petals are present to attract pollinators to the flower.
The stamen is the male reproductive part of the flower. Each stamen consists of a short stalk called a filament and a saclike structure on top of the filament called the anther. The anther contains pollen, which is the male sex cell.
The pistil, located in the center of the flower, is the female reproductive part. It produces the female sex cells, the eggs (ovules). These eggs, if fertilized, become seeds. The pistil has three main parts: a sticky stigma on top to catch pollen and a style, a tube that leads to the third part, the ovary. The egg cells develop in the ovary. After fertilization, the ovary grows to become a fruit or a seed coat depending on the type of plant.
The flower is constructed so that insects attracted to it for nectar must first climb over the anther and brush pollen on the hairy surface of their bodies. As they climb onto the center of the flower for nectar, part of the pollen is brushed onto the stigma of the pistil. This allows the fertilization process to begin. The pollen grain sprouts like a seed and sends a long stalk down the style to the ovary and egg cells. The pollen sperm cell then fertilizes the egg cells and seeds begin to develop. The ovary enlarges into a fruit or seed coat.