Plants play a very important role in nature as they are capable of photosynthesis. This is a process in which a plant receives nutrients from carbon dioxide, water and solar energy for itself and releases oxygen into the atmosphere. Therefore, it is thanks to plants that animals and we can exist on Earth.
Classification of plants
The entire plant kingdom is divided into ten divisions:
- Brown algae.
- Green algae.
- Blue-green algae.
- Red algae.
- Mossy.
- Ferns.
- Horsetails.
- Lycopterids.
- Angiosperms.
- Gymnosperms.
Among these plants, depending on the complexity of the structure, two groups can be distinguished:
- lower;
- supreme.
The lower ones include all divisions of algae, since they lack tissue differentiation. The body has no organs. It is called thallus.
Higher plants depending on the method of reproduction can be divided into:
- spore;
- seed.
The spores include ferns, lycopsids, bryophytes, horsetails.
Gymnosperms and angiosperms are classified as seminal.
We will talk about gymnosperms in more detail in this article.
Classification of gymnosperms
The next taxon that stands out in all departments of the kingdom "Plants" is a class. Gymnosperms are divided into four classes:
- Gnetovye.
- Ginkgo.
- Cycadaceae.
- Conifers.
We will talk about the representatives and features of each class later. And now the common features of all gymnosperms, their physiology and biology will be considered.
Gymnosperms: plant structure
This department belongs to higher plants. This means that their body is made up of organs that are built from different types of tissue.
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 the ground shoot.
The root system consists of many roots, among which one main and many lateral roots can be distinguished. In addition, the plant may have additional roots.
The root has the following functions:
- Fixing the plant in the soil.
- Absorption of water with dissolved micro-and macronutrients.
- Transportation of water and minerals dissolved in it to ground organs.
- Sometimes - storage of nutrients.
Escape is also an organ system. It consists of a stem, leaves and buds.
Functions of escape organs:
- Stem: supporting and transport functions, providing a link between roots and leaves.
- Leaves: photosynthesis, respiration, gas exchange, temperature regulation.
- Buds: 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 ensure the reproduction of the organism. In angiosperms, it is a flower. But the plants of the department "Gymnosperms" for the most part have such generative organs as cones. The clearest examples are spruce and pine cones.
Cone structure
She is a modified shoot covered in 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 representatives of gymnosperms in which both male and female plants are on the same plant. They are called singletons. There are also dioecious gymnosperms. They have male and female cones on different species. However, the plants of the "Gymnosperms" department are mostly monoecious.
On the scales of female cones there are two ovules, on which female gametes - eggs are formed.
On the scales of male cones are pollen sacs. They form pollen, which contains sperm - male germ cells.
When we have already considered the structure of gymnosperms, let's talk about their reproduction.
How a pine tree grows from a cone
Reproduction of gymnosperms occurs with the help of seeds. They, unlike the seeds of flowering plants, are not surrounded by a fruit.
Reproduction of gymnosperms begins with the fact that in plants in a certain period, modified shoots 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 female cones. From them, then, new representatives of the gymnosperms are formed.
What tissues are organs made of?
Plants of the department "Gymnosperms", like all higher plants, consist of various tissues.
There are these types of plant tissues:
- Integuments. These tissues perform a protective function. They are divided into epidermis, cork and crust. The epidermis covers all parts of plants. It has stomata for gas exchange. It can also be covered with an additional protective layer of wax. The cork is formed ontrunk, roots, branches and bud scales. The crust is an integumentary tissue consisting of dead cells with stiff shells. It consists of the bark of gymnosperms.
- Mechanical. This tissue provides strength to the stem. It is divided into collenchyma and sclerenchyma. The first is represented by living cells with thickened membranes. Sclerenchyma, on the other hand, consists of dead cells with stiffened 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 basic tissue is assimilation. It forms the basis of the leaves. The cells of this tissue contain a large number of chloroplasts. This is where photosynthesis takes place. Also in the organs of gymnosperms there is such a type of main tissue as storage. It collects nutrients, resins, etc.
- Conductive fabric. Divided into xylem and phloem. Xylem is also called wood, and phloem is also called bast. They are found 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 fabrics. All other gymnosperm tissues are formed from them, from which all organs are then built. They are divided into apical, lateral and intercalary. Apical are located at the top of the shoot, as well as at the tip of the root. Lateral educational tissues are also called cambium. Helocated in the trunk of a tree between wood and bast. Interstitial educational tissues are located at the base of the internodes. There are also wound educational tissues that occur at the site of injury.
So we looked at the structure of the 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. Next, representatives of the various classes that are included in the "Gymnosperms" department will be described.
Gnetovye class
Plants of the department "Gymnosperms" of the class "Gnetovye" are divided into three families
- Velvichia family.
- Gnetovye family.
- The "Ephedra" family.
Let's look at the brightest representatives of these three plant groups.
So, Velvichia is amazing.
This is the only representative of the Velvichi family. This representative of the 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 that 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 off. They are constantlygrow at the base, but periodically die off at the ends. Constantly renewing in this way, these leaves live as long as the velvichia itself (specimens are known that have lived for more than 2 thousand years).
Gnetovy family contains approximately 40 species. These are mainly shrubs, lianas, less often - trees. They grow in the tropical forests of Asia, Oceania, Central Africa. In their appearance, gnetovye are more reminiscent of angiosperms. Examples of representatives of this family are melinjo, broad-leaved gnetum, ribbed gnetum, etc.
The coniferous family includes 67 species of plants. In terms of life form, these are shrubs and semi-shrubs. They grow in Asia, the Mediterranean and South America. Members of this family have scaly leaves. Examples of conifers include American ephedra, horsetail ephedra, cone-bearing ephedra, green ephedra, etc.
Ginkgo class
This group includes one family. Ginkgo biloba is the only member of this family. This 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 Cycads
These are also gymnosperms. Examples of plants of this class: Rumfa cycad, drooping cycad, Tuara cycad, etc. They all belong to the same family - "Cycads".
They grow in Asia, Indonesia, Australia,Oceania, Madagascar.
These plants look like palm trees. Their height ranges from 2 to 15 meters. The trunk is usually thick and short when compared to the thickness. So, in a drooping cycad, its diameter reaches 100 cm, while its height is 300 cm.
Class "Coniferous"
This is perhaps the most well-known class of the gymnosperms. He is also the most numerous.
This class consists of one order - "Pine". Previously, there were three more orders of the coniferous class on Earth, but their representatives became extinct.
The above order consists of seven families:
- Capitaceous yew.
- Yew.
- Sciadopitis.
- Podocarps.
- Araucariaceae.
- Pine.
- Cypress.
The yew family includes 20 representatives. These are evergreen shrubs and trees. The needles are located in a spiral. They differ from yews in that their cones mature much longer, and they also have larger seeds.
The yew family includes about 30 species of shrubs and trees. All plants in this family are dioecious. Examples of representatives of this family include the Pacific yew, Florida, Canadian, European yews, etc.
The Sciadopitisaceae family includes evergreen trees that are often used as ornamental trees.
Examples of representativesfamilies of podocarps can be called 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 already during the Jurassic and Cretaceous periods. Examples include southern agathis, agathis dammara, Brazilian araucaria, Chilean araucaria, noble wollemia, etc.
The pine family includes such well-known trees as spruce, pine, cedar, larch, hemlock, fir, etc. All plants in this family grow in the Northern Hemisphere in temperate climates. Gymnosperms of this family are often used by humans in medicine and other industries due to their resins and essential oils.
