Laboratory work number 6 - flower structure. Laboratory work: The structure and diversity of a flower. What are the types of flowers? Why are they called that?

Chapter 2. Diversity of flora

Flower- a modified shortened shoot that serves for seed propagation. Flowers develop both at the top of the stem and in the axils of the leaves. Like any shoot, a flower develops from a bud. The stem part of the flower is represented by the peduncle and receptacle, and the calyx, corolla, stamens and pistils are formed by modified leaves.

Flower structure

No matter how great the variety of flowers of the surrounding grassland species may be, similarities can be found in their structure (Fig. 57). Pistil and stamens- the main parts of a flower. Each stamen has an anther, inside which pollen ripens. The anther is located on the filament. The pistil has a stigma, styles and an ovary. The pistil is formed by one or more modified leaves - carpels. On the inner walls of the ovary there are one or more ovules from which seeds develop. The perianth is located around the stamens and pistil. In most plants, the perianth consists of two types of leaflets. The inner leaflets are the petals that make up whisk. The outer leaves - sepals - form cup.

In some plants (apple tree, cabbage), the corolla of the flower consists of unfused petals. In others (crystal, primrose), the petals grow together in the lower part into a tube. Therefore, a distinction is made between free-petalled and fused-petaled corollas. In some plants (carnation), the lower parts of the sepals grow together into a tube. In others (geraniums), the sepals do not grow together.

The thin stem on which the flower sits in most plants is called peduncle, and its upper, expanded part, which can take different shapes, - receptacle.

The perianth consisting of a calyx and corolla is called double. Apple trees, roses and many other plants have such a perianth. In some plants, mainly monocots (lily, tulip), all tepals are more or less the same. This perianth is called simple. In some plants, the tepals of a simple perianth are large and bright, for example, a tulip, while in others, for example, a rush plant, they are inconspicuous. Willow and ash flowers do not have a perianth. They are called naked.

6th grade

Laboratory work № 14, 15

“Structure and functions of a flower”

Target: consolidate knowledge about the structure of a flower as a plant reproductive organ.

Equipment: natural objects, replicas of plant flowers, drawings.

Progress

Exercise 1

Look at the picture showing the structure of a flower (handout)

Draw a picture in a notebook and label all parts of the flower.

Task 2

Examine a dummy flower (or drawing), count the number of petals, sepals, stamens, pistils; make a flower formula and fill out the table:

Plant name	Number of sepals	Number of petals	Number of stamens	Number of pestles	Flower formula

Task 3.

Flowers with which perianth are shown in the picture?

Task 4.

Answer the questions:

1 Option

Define flower.

Name female organ flower. What does it consist of?

Which flowers are called bisexual?

What flowers are called regular?

What flowers are called monoecious?

Option 2

Define flower.

Name male organ flower. What does it consist of?

What flowers are called dioecious?

What flowers are called irregular?

What flowers are called dioecious?

Laboratory work in biology grade 7 No. 6 - The structure of a flower

Consider the flowers offered to you. Find all the main elements of a flower - pedicel, receptacle, perianth, stamens and pistils.

Fill the table.

Sketch the flower and label its main parts.

Cut the ovary crosswise and examine it with the underside. (You can use a picture or table.) Find the ovules. What is formed from the ovule and the ovary of the pistil?

Ovule: seeds

Pistil ovary: fruits

Draw a conclusion.

What are the structural features of a flower?

The structure of a flower is associated with the functions it performs: there are organs for the formation of germ cells, attracting pollinators, and protection.

What are the types of flowers? Why are they called that?

They are bisexual - because they have a pistil and stamens on one flower; dioecious - since pistils and stamens are formed on different flowers.

What role do flowers play in the life of a plant?

Flowers are the reproductive organs of flowering plants.

How does a dioecious plant differ from a monoecious plant?

In dioecious plants, staminate and pistillate flowers develop on different plants.

Color of flowers in land and aquatic plants very diverse. Naturalists have long noticed that plants that bloom in the evening or at night most often have a flower corolla white. How can you explain this phenomenon?
The white corolla is easier to see in the dark for pollinating insects.

The structure and variety of a flower.

Flower is a modified shortened shoot adapted for the reproduction of angiosperms (flowering) plants. The exclusive role of the flower is due to the fact that it combines all the processes of asexual and sexual reproduction, while in lower and many higher plants they are disunited. In a bisexual flower, micro- and megasporogenesis, micro- and megagametogenesis, pollination, fertilization, and the formation of seeds and fruits take place. The structural features of the flower allow the above functions to be carried out with minimal costs plastic substances and energy.

Flower structure

A flower consists of a stem part (pedicel and receptacle), a leaf part (sepals, petals) and a generative part (stamens, pistil or pistils). The flower occupies an apical position, but at the same time it can be located either at the top of the main shoot or at the lateral one. It is attached to the stem by means of a peduncle. If the peduncle is greatly shortened or absent, the flower is called sessile (plantain, verbena, clover). The peduncle also contains two (in dicotyledons) and one (in monocotyledons) small preleaves - bracts, which may often be absent. The upper expanded part of the peduncle is called the receptacle, on which all the organs of the flower are located. The receptacle may have various sizes and shape - flat (peony), convex (strawberry, raspberry), concave (almond), elongated (magnolia). In some plants, as a result of the fusion of the receptacle, the lower parts of the integument and the androecium, a special

structure - hypanthium. The shape of the hypanthium can be varied and sometimes participate in the formation of the fruit (cynarrhodium - rose hip, apple). Hypanthium is characteristic of representatives of the rose, gooseberry, saxifrage, and legume families.

The parts of a flower are divided into fertile, or reproductive (stamens, pistil or pistils), and sterile (perianth). Perianth The perianth is the sterile part of the flower that protects the more delicate stamens and pistils. The elements of the perianth are called tepals, or perianth segments. In a simple perianth, all the tepals are the same; in a double perianth, all the tepals are differentiated. The green tepals of the double perianth form a calyx and are called sepals, the colored tepals of the double perianth form corollas and are called petals. The vast majority of plants have a double perianth (cherry, bell, carnation). A simple perianth can be cup-shaped (sorrel, beet) or (which happens more often) corolla-shaped (goose onion). In a small number of species, the flower is completely devoid of perianth and is therefore called coverless, or naked (whitewing, willow). The flower of one of the ranunculaceae - larkspur, with five blue sepals and a white eye formed by nectary petals and staminode petals.

The calyx consists of sepals and forms the outer circle of the perianth. The main function of the sepals is to protect the developing parts of the flower before it blooms. Sometimes the corolla is completely absent or greatly reduced, and the sepals take on a petal-like shape and are brightly colored (for example, in some ranunculaceae). The sepals can be separate from each other or fused together.

The request for "Corolla" is redirected here; see also other meanings.

Corolla formed varying amounts petals and forms a circle in the flower next to the calyx. The origin of the petals may be related to vegetative leaves, but in most species they are thickened and expanded sterile stamens. Near the base of the petals, additional structures are sometimes formed, which are collectively called the corolla. Like the sepals, the petals of the corolla can grow together at the edges (fused-petaled corolla) or remain free (free-petaled corolla). A special specialized type of corolla, the moth-type corolla, is observed in plants from the subfamily Mothaceae and the legume family.

The corolla, as a rule, is the most noticeable part of the flower; it differs from the calyx in its larger size, variety of colors and shapes. Usually it is the corolla that creates the appearance of the flower. The color of the corolla petals is determined by various pigments: anthocyanin (pink, red, blue, purple), carotenoids (yellow, orange, red), anthochlor (lemon yellow), antopheine (brown). The white color is due to the absence of any pigments and the reflection of light rays. There is also no black pigment, and very dark colors of flowers are very condensed dark purple and dark red colors.

The aroma of flowers is created by volatile substances, mainly essential oils, which are formed in the cells of the epidermis of petals and perianth leaves, and in some plants - in smophora (special various shapes glands containing secretory tissue). The released essential oils usually evaporate immediately.

The role of the corolla is to attract pollinating insects. In addition, the corolla, reflecting part of the spectrum of sunlight, protects the stamens and pistils from overheating during the day, and by closing at night, they create a chamber that prevents them from cooling or being damaged by cold dew.

Stamens (androecium)

Stamen - male reproductive organ of a flower angiosperms. The collection of stamens is called the androecium.

Most botanists believe that the stamens are modified microsporophylls of some extinct gymnosperms.

The number of stamens in one flower varies widely among different angiosperms, from one (orchids) to several hundred (mimosas). As a rule, the number of stamens is constant for a particular species. Often the stamens located in the same flower have a different structure (in the shape or length of the stamen filaments).

Stamens can be free or fused. Based on the number of groups of fused stamens, they distinguish different types androecium: monofraternal, if the stamens grow together into one group (lupine, camellia); difraternal, if the stamens grow together into two groups; polygamous, if numerous stamens grow together into several groups; fraternal - the stamens remain unfused.

The stamen consists of a filament, through which it is attached to the receptacle at its lower end, and an anther at its upper end. The anther has two halves (thecae), connected by a connective tissue, which is a continuation of the filament. Each half is divided into two nests - two microsporangia. Anther nests are sometimes called pollen sacs. The outside of the anther is covered with epidermis with cuticle and stomata, then there is a layer of endothecium, due to which, when the anther dries, the nests open. The middle layer runs deeper in the young anther. The contents of the cells of the innermost layer, the tapetum, serve as food for the developing mother cells of microspores (microsporocytes). In a mature anther, the partitions between the nests are most often absent, and the tapetum and middle layer disappear.

Two important processes occur in the anther: microsporogenesis and microgametogenesis. In some plants (flax, stork) some of the stamens become sterile. Such barren stamens are called staminodes. Often the stamens function as nectaries (blueberries, blueberries, cloves).

Carpels (gynoecium)

The inner part of the flower is occupied by carpels, or carpels. The collection of carpels of one flower forming one or more pistils is called the gynoecium. The pistil is the most essential part of the flower from which the fruit is formed.

It is believed that carpels are structures in which the leaf nature of origin can be traced. However, functionally and morphologically they correspond not to vegetative leaves, but to leaves bearing megasporangia, that is, megasporophylls. Most morphologists believe that in the course of evolution, longitudinally folded (conduplicate) carpels arose from flat and open ones, which then fused at the edges and formed a pistil. The pestle occupies central part flower. It consists of an ovary, a style and a stigma.

Laboratory work

Subject. Structure and variety of flowers.

Target: learn the structure of flowers, learn to identify the parts of a flower;

get to know the variety of flowers.

Equipment: flowers indoor plants,

Briefing on safety precautions and rules of use

laboratory equipment and handouts.

Progress:

Look at the proposed flower, identify its parts and label them in your notebook.

Fig 1.

Consider the proposed flower models in Fig. 2. Identify and write down the numbers (numbering may be repeated): a) which of them double perianth ; b) which ones - simple ; c) which flowers whisk lobed ; d) which ones - interpetalous.