Plants play a very important role in nature, as they are capable of photosynthesis. This is a process in which a plant from carbon dioxide, water and solar energy receives nutrients for itself and releases oxygen into the atmosphere. Therefore, it is thanks to plants on Earth that animals and we can exist.
Plant classification
The whole kingdom of plants is divided into ten departments:
- Brown algae.
- Green algae.
- Blue-green algae.
- Red algae.
- Mossy.
- Fern-shaped.
- Horsetail.
- Lap-like.
- Angiosperms.
- Gymnosperms.
Among these plants, depending on the complexity of the structure, two groups can be distinguished:
The lower ones include all departments of algae, since they lack tissue differentiation. The body has no organs. It is called tall.
Higher plants, depending on the method of propagation, can be divided into:
Spore-related fern-shaped, fluvoid, bryophyte, horsetail-shaped.
The divisions are gymnosperms and angiosperms.
We will talk about gymnosperms in more detail in this article.
Gymnosperm classification
The next taxon that stands out in all departments of the kingdom "Plants" is the class. Gymnosperms are divided into four classes:
- Oppressive.
- Ginkgo.
- Cygnus (Cycadic).
- Conifers.
We will talk about the representatives and features of each class later. And now we will consider the general features of all gymnosperms, their physiology and biology.
Gymnosperms: plant structure
This department belongs to higher plants. This means that their body consists of organs that are built from different types of tissues.
The organs of gymnosperms
Depending on the location of the organs, they can be divided into underground and ground. Given their functions and structure, vegetative and generative organs can be distinguished.
Vegetative organs: structure and functions
This group of organs includes the underground root system and ground shoot.
The root system consists of many roots, among which one can distinguish one main and many lateral roots. In addition, the plant may have additional roots.
The root has the following functions:
- Fixing plants in the soil.
- Absorption of water with micro and macro elements dissolved in it.
- Transportation of water and minerals dissolved in it to ground organs.
- Sometimes - stocking up nutrients.
Escape is also a system of organs. It consists of a stem, leaves and buds.
Escape organs functions:
- Stem: supporting and transport functions, providing communication between roots and leaves.
- Leaves: photosynthesis, respiration, gas exchange, temperature regulation.
- Kidneys: new shoots form from them.
Gymnosperms and angiosperms have the same vegetative organs, but their generative organs are different.
Generative organs of gymnosperms
Generative organs are those that provide the reproduction of the body. In angiosperms, this is a flower. But the plants of the gymnospermous plant department for the most part possess such generative organs as cones. The most striking visual examples are spruce and pine cones.
Cone structure
It is a modified shoot covered with scales. There are male and female cones in which male and female sex cells (gametes) are formed, respectively.
Male and female pine cones as an example can be seen in the photo below.
There are such representatives of gymnosperms, in which both male and female plants are on the same plant. They are called monoecious. There are also dioecious gymnosperms. They have male and female cones in different forms. However, the plants of the gymnosperms department are mostly monoecious.
Two ovules are located on the scales of the female cones, on which female gametes - eggs are formed.
On the scales of male cones are pollen bags. They form pollen, which contains sperm - male germ cells.
When we have already examined the structure of gymnosperms, let’s talk about their reproduction.
How a pine grows from a cone
Gymnosperms are propagated by seed. They, unlike the seeds of flowering plants, are not surrounded by the fruit.
The reproduction of gymnosperms begins with the fact that in plants at a certain period modified buds are formed from the buds - male and female cones. Further, pollen and eggs are formed on them, respectively.
Pollination of female cones occurs with the help of wind.
After fertilization, seeds develop from the ovules, which are located on the scales of the female cones. From them, then, new representatives of gymnosperms are formed.
What tissues do organs consist of?
Plants of the gymnosperms department, like all higher ones, are composed of various tissues.
There are such types of plant tissues:
- Coverslips. These tissues perform a protective function. They are divided into epidermis, cork and peel. The epidermis covers all parts of the plants. It has stomata for gas exchange. It can also be coated with an additional protective layer of wax. A cork is formed on the trunk, roots, branches, and kidney scales. Crust is an integument consisting of dead cells with woody membranes. It consists of gymnosperm bark.
- Mechanical This fabric provides strength to the stem. It is divided into collenchyma and sclerenchyma. The first is represented by living cells with thickened membranes. The sclerenchyma consists of dead cells with woody membranes. Mechanical fibers are part of the conductive tissues contained in the stems of gymnosperms.
- Main fabric. It is she who forms the basis of all organs. The most important type of underlying tissue is assimilation. It forms the basis of the leaves. In the cells of this tissue is a large number of chloroplasts. This is where photosynthesis takes place. Also in the organs of gymnosperms there is such a kind of basic tissue as storage. It collects nutrients, resins, etc.
- Conductive fabric. It is divided into xylem and phloem. Xylem is also called wood, and phloem is called bast. They are in the trunk and branches of the plant. The xylem of gymnosperms consists of vessels. It provides transportation of water with substances dissolved in it from the root to the leaves. The phloem of gymnosperms is represented by sieve tubes. The bast is designed to transport substances from the leaves to the root.
- Educational tissue. All other gymnosperm tissues are formed from them, from which all organs are then built. They are divided into apical, lateral and insertion. Apicals are located at the top of the shoot, as well as at the tip of the root. Lateral educational tissue is also called cambium. It is located in a tree trunk between wood and bast. Inset educational tissue located at the base of the internodes. There are also wound educational tissues that occur at the site of damage.
So we examined the structure of gymnosperms. Now let's move on to their representatives.
Gymnosperms: examples
When we already know how the plants of this department are arranged, let's look at their diversity. Representatives of various classes that are part of the gymnosperms department will be described below.
Class "Oppressive"
Plants of the gymnosperms department of the Oppressive class are divided into three families
- Family "Velvichievye".
- Family "Oppressive".
- Family "Ephedra".
Let's look at the brightest representatives of these three groups of plants.
So, the welwitch is amazing.
This is the only representative of the Velvich family. This representative of gymnosperms grows in the Namib desert, as well as in other deserts of South West Africa. The plant has a short but thick trunk. Its height is up to 0.5 m, and its diameter reaches 1.2 m. Since this species lives in the desert, it has a long main root, which goes 3 m deep. The leaves that grow from the trunk of Velvichia are a real miracle. Unlike the leaves of all other plants on Earth, they never fall. They constantly grow at the base, but periodically die off at the ends. Constantly updated in this way, these leaves live as long as velvichia itself (specimens known for over 2 thousand years are known).
The oppressive family contains approximately 40 species. These are mainly shrubs, creepers, less commonly trees. They grow in the tropical forests of Asia, Oceania, Central Africa. By their appearance, oppressive resemble angiosperms more . Examples of representatives of this family are melinjo, broadleaf oppression, ribbed oppression, etc.
The conifer family includes 67 plant species. In terms of life, these are shrubs and shrubs. They grow in Asia, the Mediterranean and South America. Representatives of this family have scaly leaves. Examples of conifers include American ephedra, horsetail, coniferous conifers, green conifers, etc.
Class "Ginkgo"
This group includes one family. The only representative of this family is ginkgo bilobate. It is a tall tree (up to 30 meters) with large fan-shaped leaves. This is a relic plant that appeared on Earth 125 million years ago! Ginkgo extracts are often used in medicine to treat vascular diseases, including atherosclerosis.
Class "Cycas"
This is also gymnosperms. Examples of plants of this class are: Rumph's Cypress, Suspending Cycas, Tuar Cypress, etc. They all belong to the same family - "Cycas".
They grow in Asia, Indonesia, Australia, Oceania, and Madagascar.
These plants look like palm trees. Their height is from 2 to 15 meters. The trunk is usually thick and short, when compared with the thickness. So, in a cygnus, its drooping diameter reaches 100 cm, while its height is 300 cm.
Class "Conifers"
This is perhaps the most famous class of gymnosperms. It is also the most numerous.
This class consists of one order - "Pine". Earlier on Earth, there were three more orders of the coniferous class, but their representatives became extinct.
The order mentioned above consists of seven families:
- Capitate.
- Yew.
- Sciadopitis.
- Subcarpous.
- Araucariaceae.
- Pine trees.
- Cypress.
The capitate family includes 20 representatives. These are evergreen shrubs and trees. The needles are arranged in a spiral. They differ from yew capitals in that their cones ripen much longer, and they also have large seeds.
The yew family includes about 30 species of shrubs and trees. All plants of this family are dioecious. Examples of representatives of this family include the Pacific yew, Florida, Canadian, European yew, etc.
The family of sciadopitis includes evergreen trees, which are often used as ornamental.
Examples of representatives of the podocarp family are dacridium, phyllocladus, podocarp, etc. They grow in humid areas: in New Zealand and New Caledonia.
The Araucariaceae family unites about 40 species. Representatives of this family existed on Earth during the Jurassic and Cretaceous periods. Examples are southern agatis, agathis dammar, Brazilian araucaria, Chilean araucaria, noble vollemia, etc.
The pine family includes such well-known trees as spruce, pine, cedar, larch, tsuga, fir, etc. All plants belonging to this family grow in the Northern Hemisphere in a temperate climate. Gymnosperms of this family are often used by humans in medicine and other industries due to their resins and essential oils.