Topic: Flower functions

Author: Elżbieta Szedzianis

Target group

Students of the 5th grade of an elementary school.

Core curriculum

5 ) Angiosperms - student:

b) observes the flowering plant (photographs, engravings, live specimens); recognizes its organs and determines their functions (root, stem, leaf, flower),

c) describes modifications of roots, stems and leaves as adaptation of angiosperms to life in specific environments,

d) presents methods of vegetative reproduction of plants and observes selected methods of vegetative reproduction.

The general aim of education

The students indicate male and female reproductive organs and describe their functions.

Criteria of success

• You will observe the flower's structure and make its model,

• You will show where sperm and egg cells are located in the flower.

Key competences

• communication in foreign languages;

• communication in the mother tongue;

• mathematical competence and basic competences in science and technology; 

• learning to learn.

Methods / techniques

Map of terms, direct observation, workshop method - model execution.

Individual work, work in groups.

Teaching aids

• abstract;

• interactive or traditional board;

• tablets/computers;

• A3 sheets;

• pens;

• tulip flowers;

• materials for building models: colored paper, skewers, creative wires, glue, rubber bands, adhesive tape, plasticine, drinking straws, bottle caps.

Lesson plan overview (Process)

Introduction

1. The teacher explains that the lesson will be devoted to a flower in which the sexual reproduction process of the plant takes place.

2. The teacher reminds the students that they have already learnt how plants reproduce asexually. The teacher divides the youth into groups, gives them A3 sheets and markers, and asks them to create maps illustrating asexual reproduction of plants from the terms and phrases written on the board. Terms to use: importance of reproduction, reproduction method, spores, mosses, ferns, roots, horseradish, underground stems, rhizomes, bulbs, potato, couch grass, runners, strawberry, seedlings, geraniums, leaves, African violet, increasing the number of specimens.

3. The teacher gives the student's criteria of success.

Realisation

1. The teacher divides the class into groups and gives them large entomophilous flowers, e.g. tulips. The teacher explains that she will discuss the structure of apple blossom based on illustrations in the abstract (illustration 1. Structure of a flower of a plant pollinated by insects), and the students have to look for relevant elements of the structure in the observed flower and indicate them. The teacher draws attention to the female and male parts of the flower, the occurrence of egg cells in the pistil and sperm cells in the pollen grains, indicates the stigma of the pistil.

2. The teacher asks the students to make a tulip flower model. The teacher gives the students necessary materials. Using coloured paper, the students cut out selected elements and using the sticks, coloured creative wires, glue, rubber bands, adhesive tape, plasticine, drinking straws, bottle caps with a hole in the middle, they design a flower model.

Before the students start to work, the teacher presents the model assessment criteria:

• in the model you can distinguish the stem, flower bed, crown petals, pistil and stamens,

• the model consists of the right number of petals, stamens and the stigma of the pistil in the right shape typical of a tulip,

• the egg cell and pollen grains were placed in the appropriate places of the model.

3. The teacher shows Video 2 (the second part) and explains how fertilization and the formation of flowers and fruits occur. The teacher asks the students to make a plasticine tulip fruit (enlarged pistil) with a few seeds.

4. The students do interactive exercise No. 1.

Summary

1. The students do interactive exercise No. 2.

2. The students read the definition of sexual reproduction: Sexual reproduction - reproduction of organisms with the participation of two reproductive cells (ovum and sperm), which are produced in the female and male reproductive organs. As a result of this reproduction a new organism is formed. Based on the definition, they explain if there is sexual reproduction in the tulip and the apple.

3. The students use coloured sheets to assess if they have achieved the criteria of success in the lesson.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Flower

A flower is a transformed shoot which green leaves of which conduct photosynthesis and have been modified and adapted to perform the sexual reproduction function. The flower is on a flower stalk that is called a pedicel, which expands upward to form a receptacle. All elements of the flower are placed on the receptacle. These include pistils, stamens and the perianth (calicle) that in entomophilous plants is divided into the calyx and the corolla.

The most external part of the flower pollinated by insects is the calyx built from several sepals. Usually, these are green leaves that protect the bud until the flower is opened and support the corolla when it is fully developed. The corolla is made of petals that protect the interior of the flower. Their role is also to lure insects or other animals.

The pistil is a female reproductive organ placed in the centre of the flower. It consists of an enlarged lower part – the ovary, and an elongated style topped with a stigma, which is adapted to receive pollen grains. In the ovary there are several integument‑covered ovules. The ovary wall protects them from the outside. These plants are called – angiosperms. The stigma of the pistil is often sticky or rough to stop pollen grains settling on it.

Stamens are male reproductive organs that grow around the pistil. A single stamen is made of a filament on which the head of the stamen is located. Each head consists of two anthers, and each anther has two pollen sacs. Pollen grains are produced in the sacs.

At the bottom of the flower there are nectaries producing sweet liquid which apart from pollen is food of animals pollinating flowers.

Flowers are most often androgynous(bisexual). This means that in one flower there are pistils and stamens. Unisexual flowers containing only pistils or only stamens are more seldom.

Unisexual flowers may be found on one plant, called monoecious, or on two separate plants, called dioecious.

Some flowers of angiosperms grow on the stem individually, other plants form clusters called inflorescences. One to several tens of thousands of flowers are then placed on one apical shoot. Thanks to placing such a great amount in one place, the insects do not have to look for more flowers at long distances. This increases the chance of pollination and thus the opportunity to release more seeds. Inflorescences differ in the way of shoots are branched, and the way flowers are placed on them.

Mature pollen grains are usually transferred from one flower to the stigmas of another flower of the same species. This process is called pollination. The carrier of pollen in angiosperms is the wind, few species use water for this purpose, but most often pollination takes place through animals, mainly insects.

Flowers of anemophilous plants do not have to lure insects. They do not have coloured petals, do not smell and do not produce nectar. Their perianths (calicles) are inconspicuous or absent, and male and female organs are often found on separate plants. The pistils have complex, feathery marks that capture wind‑shed pollen grains. The stamens produce huge amounts of fine and light pollen to increase the likelihood of reaching a female flower. Examples of plants that produce particularly large amounts of pollen are birch – a single inflorescence produces about 5.5 million, and rye – one ear is about 42 million anthers.

Flowers of plants pollinated by animals lure them with their scent, colour and shape. Colourful, magnificent petals of the corolla are often covered with lines and dots, and show insects the way to the interior of the flower. During the search for food, which is nectar produced in nectaries, the insect is dusted with pollen and moves it to the pistil of the next flower. There it leaves it on a sticky stigma of the pistil. Entomophilous plants are pollinated by insects of various species. The most well‑known pollinators are bees, but this group also includes bumblebees, wasps, flies and butterflies.

When a pollen grain gets to the stigma of the pistil, it germinates, producing a pollen tube that grows through the style of the pistil to the ovary. At the top of the tube there are two sperm cells. When along with the pollen tube they reach the ovule, fertilization takes place. One of the sperm cells connects to the egg cell, resulting in a zygote, and from it a embryo – a new plant anlage. After fertilization a flower transforms into a fruit; The pistils and the style with the stigma dry out, the flower dies out and disappears.

In the ovule the nutrient tissue is formed for the embryo, and its hardening shells change into a testa. The embryo together with the nutrient tissue and the testa form a seed. The ovarian wall transforms into a pericarp, which together with the seed creates a fruit. There can be one or many seeds in one fruit. After being released from the fruit, the seed germinates if it has favourable conditions. A seedling is formed, i.e. a young, immature plant. After reaching maturity, it will bloom and it will bear fruit and its development cycle will close.

• The organ of sexual propagation of seed plants is a flower.

• Pollen grains contain sperm cells.

• The ovule contains an egg cell.

• Pollination of a flower occurs by transferring pollen from the anther to the mark of the pistil.

• As a result of fertilization, i.e. the connection of a sperm cell with an egg ell, a germ of a new plant is formed in the ovule.