Growned plants are a fairly old group of plants (in most evergreen), the appearance of which belongs to the upper Devonian (almost 400 million. years ago). Focusing on the name, we can understand that it indicates the main distinctive feature of this group: a counterweight from coatedseeded ones, their seeds (and then already seeds) do not have a closed container familiar to all plants. T.e. their seeds are openly located on the surface of scales.
And it is the seeds, their presence, are a huge advantage of this group over the same spores, because the seeds have a supply of useful substances, and the embryo itself, located inside the seed, is perfectly protected from the influence of the external environment.
Description of gymnosperms
Department of gymnosperms ancient senior seed species. Their heyday was observed about 200 million years ago at that time they were the Lords of the ground plants of the planet. Their seeds do not have a closed shell: the ovary of such plants has the form of a conventional scales on which seeds are located (one or more). This group of plants is quite extensive it includes about 1100 various species of plants, almost 90 genera and 14 families.
Interestingly, the concept of “Gymnospermae” was proposed two hundred years ago (1825) by the Scotsman Brown (it was he who was the discoverer of the famous “Brownian” movement). He first discovered and described the significant differences between the two departments of plants gagseed and coveredseeded. And the term “gymnosperm” was most likely introduced by Professor Beketov.
Classes of gymnosperms
Modern gymnosperms have mainly wood shape, in exceptional cases shrub or vine. Moreover, grassy plants in this group are absent.
And the main difference of this group of plants is the foliage, which is distinguished not only in shape and volumes, but also by other morphological and anatomical characteristics. Most types of needles are needleshaped or scaly.
Grownseeds, which have more than a thousand species, are distributed throughout the earth’s surface and on all continents (with the exception of Antarctica). Their important environmentforming role is played by a significant function in the ecosystem of the famous coniferous forests the plains of the temperate zone, which are famous for the northern hemisphere. And not only here but also in the forest belt any of the latitudes.
Modern systematics subjected strict doubts the issue of the unity of the origin of plants of this department. Now gymnosperms are a group of unsystematized specialized plants:
This includes several extinct groups:
In its main part, ginking are the remains of plants that dominated the planet during the Mesozoic era. Surprisingly, they survived dinosaurs, and were preserved in remote places of the planet.
The only representatives of this class that have reached us is a twoblade gingko, which is distributed only in certain areas of China. Its original foliage has gained popularity in the gardens of subtropics and parks. It must be emphasized that all other representatives of the specified type died out during the ice age.
The nestshaped, forming a department included in the outfit of gymnosperms, contain only one class shellshred or nesting. This includes several families of this species:
This department is close to the saga, if you rely on its life cycle, however, it is characterized by a more complex system of reproductive organs. It is thanks to her that this department can be safely brought closer to flower groups.
The only genus in the nesting family is the oppression, and it consists of more than four dozen species of trees. The most famous of them, the oppression of the Gnemon, is grown in the territory of Southeast Asia, due to its edible fruits and is distinguished by the presence of a vascular system.
Sagovniks formed huge territories of forests 60 million years ago, and now they are common only in the tropics. Usually sagroty resembles palm trees mainly, in its height (up to 15 m.).
They are distinguished by a thick barrel, which is surrounded by a shell from the bases of a dead foliage. Their foliage has two features:
Plants are dioecious, but female individuals do not form compact strobils. For both the Sagovnikovs and for ginges, a characteristic feature is the presence of mobile spermatozoa and this is recognized as a primitive characteristic.
Coniferous are the most common among gymnosperms; They can be found both in the temperate and subtropical climatic zone. As a rule, they do not have a vascular system, but there are tracheids, because these plants are characterized by abundant release of resin and the formation of resin moves.
The leaves of this group of plants turned into needles with a reduced leaf plate with bent edges and a groove with small mouths. Such a tail helps reduce the evaporation of water and this helped the coniferous assimilated in both subtropics and in the northern regions.
It is this type that includes the highest trees on the planet sequoia. Their height sometimes reaches hundreds of meters, and the width is up to 12 meters. Their age is also surprising more than a few thousand years. According to some reports, their life expectancy may exceed 6 thousand years but this information has not been confirmed by scientifically.
Signs of gymnosperms
Of the modern species of gymnosperms, conifers are most widely known, which are widespread in many countries, in t.h. and ours: pine, cypress, fir, juniper, spruce.
The main sign of such plants is the needles: narrow, needle leaves characteristic of most coniferous. Such leaves have a dense skin that is covered with a special waxy substance. That is why such plants are distinguished by poor evaporation of water, and, on the other hand, excellent adaptability to a variety of adverse conditions.
The main features of plants of the Graceful group include:
It was the presence of seeds that served as a significant evolutionary jerk, which allowed g glorying plants to use their significant advantages. A sufficient number of ancient species have been preserved among such plants: for example, the most important and significant of them are conifers.
Development of gymnosperms
The sexual development of gymnosperms is marked by the formation of seeds, which usually consist of several components:
An important fact is that the autonomic method of propagation in plants of this department is extremely rare.
Features of gymnosperms
Adult plants of gymnosperms can be called sporophytes, t.e. There is a development of dispute that ripen in sporangias located in female cones. In the spring, male disputes are spilled out and pollinated by female cones they include air cells and are very easily tolerated by the wind.
Female cones are characterized by a more intensive coloring of red color, and their disputes do not fly out, but germinate in the bump, inside the sporangia. Thus, the sprouted female dispute forms a embryo equipped with two archegonias the socalled gametophyte. Male gametophyte is a pollen (as in the case of a pine) sperm, or male gametes are being built from its cell.
Characteristics of gymnosperms
The general characteristic of plants of this department can be attributed:
Propagation of gymnosperms
The main feature that distinguishes gymnosperms from others is a propagation system, specifically the presence of seeds. Unlike flowering plants familiar to everyone, gym seeds do not form the fetus.
In the spring, two types of cones ripen on plants female, located at the top, and male, collected at the foundations of shoots. The bump consists of an axis and scales: two seeds with gametes, or eggs, are formed on female cones.
Male cones are equipped with several pollen bags and from them pollen spreads by the wind and fertilizes female cones. After the pollination process, scales close and glue.
The structure of gymnosperms
All plants of the gymnosperm department have a wood or shrub form. Some of them are very branching and form a large number of small leaves in the main of the scales. And others do not differ in great branchiness and form large sheet forms.
Most gymnosperms do not form a vascular system in xylene and satellite cells-in Floem. But they are all characterized by a complex fabric structure, in contrast to fernlike.
Glassseeds are plants with different disputes, and microsporophylls differ significantly in shape and structure from macrosporophyll. As a rule, in these plants they are on strokes short shoots.
Microspores are called dust and are formed in a pollen bag; The wind transfers them to female gametophyte, where they germinate in megasporangia, or seven. Megaspor develops there and after the fertilization of the seeds, the seed forms. The nutritional supply in the seed is absorbed by the zygota during germination and, the most interesting thing is that the seeds can be at rest until the necessary conditions occur.
Graduate plants do not form fruits, but their seeds form a variety of devices to alleviate the process of their distribution.
Gymnosperms (in t.h. and coniferous) have a shape of trees or shrubs and the stems of these plants are characterized by anatomically continuous structure (not beam).
A distinctive feature of the stems of plants of this department is the presence of a resinseparating system: it is usually formed by a large number of branched resin moves in a variety of stem zones (usually core and core rays).
It is this feature that is a specialty of gymnosperms resin helps plant stability against infections.
Most of the plant of the gymnosperms of the foliage form needles, each of which has existed for several years. Thanks to this, the area of the leaf, accessible to photosynthesis, but at the same time (and based on this structure), the photosynthesis process can last all year round year. Due to this structure of foliage, the evaporation process decreases and the fitness of the plant increases.
The main feature that the plant considers to be a squad of gymnosperms is a complete absence of fruits as such. It is open not only the seeds are located the seeds are also in the public domain, usually on the inside of the needle or in the bump; In such plants, the ovary is simply absent.
The ancestors of the plants of this department were fern, but if we take into account the latest genetic studies, then the option is possible that they had a completely different ancestor.
The main fabrics of any plants can be safely called several types:
The parttime department is distinguished by the development of all types of fabric. In addition, they have a photosynthetic and stocking fabric.
The value of gymnosperms
Growning plant play an important role in the entire natural cycle, the environment and the life of a person as a whole. Such a fundamental role is associated with their widespread distribution, high qualities of their wood and even the nutritional value of their seeds.
It is the plants of this department that are formed by forests, in the conditions of which the life of numerous species of fauna passes and new types of flora appear.
It is in such forests that there is a nutritious environment and the conditions for the existence of many animal species. And this, without taking into account the ability of forests to enrich the environment and atmosphere of oxygen, perform cleansing functions through the absorption of carbon dioxide.