The structure of each plant organ is due to the performance of certain functions. And each of them performs a certain role, which is very important for them.
What is an organ?
An organ is a part of an organism that has a certain structure, occupies a certain position, and performs certain functions. It must necessarily consist of several types of tissue. For example, the heart consists of muscle and connective, and the sheet consists of integumentary, conductive and basic.
Vegetative and generative organs of plants
Depending on the functions performed, there is a certain classification of these parts of the plant organism. So, generative organs are called organs in which germ cells develop - gametes. They are female (ovum) and male (sperm). The latter differ from sperm cells in that they are not able to move independently. For fertilization, they need wind or water.
Generative organs carry out the function of sexual reproduction. Vegetative, which include the root and shoot, provide growth, nutrition of mineral and organic substances.
Escape and its modifications
The aerial part of any plant is called the shoot. First of all, it is represented by the axis - the stem. The shoots are varied in shape: erect, creeping, curly, clinging ... Leaves are attached to the axis. To perform additional functions, such as water supply, protection, vegetative propagation, in some plants, the shoot can be modified. Examples of such structures are iris rhizome, garlic bulb, Jerusalem artichoke tuber or thorns of thorns.
Vegetative and generative organs carry out their functions in a friendly tandem. Indeed, for the development of seeds and fruit ripening, nutrients are needed that are photosynthesized in the leaves and absorbed from the ground by the root.
Root
This underground organ reliably fixes the plant and is responsible for mineral nutrition. The water located between the soil particles contains valuable metal ions and acid residues. They are a prerequisite for the growth of a plant organism. These substances through the conductive tissue flow up - to the stem and leaves. This movement is called upward current. But the glucose that forms in the leaves moves to the root. This current is called downstream.
The underground organ also forms modifications. So, carrot root and asparagus tuberous root store the necessary substances. Ivy trailers allow it to grow on an absolutely vertical surface, and the respiratory roots of an orchid can absorb moisture directly from the air.
Generative organs of flowering plants
Bright and beautiful flowers have long been a favorite decoration and a gift for any holiday. In addition to visual appeal, they carry out the process of sexual reproduction of plants. The generative organs of plants are also seeds. They contain an embryo, which over time turns into an adult plant.
Since the organs in which germ cells develop are called generative, the fetus also belongs to this group. It is he who protects the seeds from the influence of adverse conditions, temperature differences, contributes to their distribution.
Flower
Generative organs appear from the kidney of the same name. Its development begins in the spring, when the duration of daylight increases significantly. Moreover, the flowers appear before the leaves.
The generative organs of a flower, or rather its parts, are represented by a pestle and stamen. It is in them that female and male gametes develop, respectively. Bright petals, the totality of which is called the corolla, are necessary to attract insects that carry out the pollination process. The lower, expanded part of the flower is the receptacle. Carpels are attached to it. Their combination is called a cup.
The flowers are quite diverse in structural features, which depend on the characteristics of pollination. If it occurs with the help of wind, they most often do not have a perianth - a corolla and calyx. Or is he very small. This is a special device that is aimed at capturing pollen. And the flowers themselves are small, nondescript, odorless and aroma of nectar. Their pollen is light, loose, in large quantities develops in the wind. Flowers are collected in long inflorescences swaying in the wind.
If pollination occurs with the help of insects, on the contrary, bright coloration, large inflorescences and an enticing aroma are necessary for their attraction.
As a result of flowering, fruits are formed. They are classified according to the number of seeds and the structure of the pericarp. For example, an apple is multi-seeded and juicy, and a nut is dry and single-seeded. Each type of fruit has a specific device for the distribution of seeds. Ash and maple lionfish are carried by the wind; in the fall, oak and chestnut seeds bounce off. With the help of animals, tasty and juicy fruits are distributed.
What is double fertilization
Fertilization is the process of fusion of gametes. A feature of this process in flowering (angiosperms) plants is that it is preceded by pollination - transfer of pollen from the anther of the stamen to the stigma of the pestle. It can be natural - with the help of wind or insects - or artificial - with the help of man.
Once on the stigma of the pestle, two sperm with the help of the germinal tube descend into its lower expanded part - the ovary. One of them fertilizes the egg. The result of this process is an embryo. It possesses all the features of an adult organism and consists of a germinal root, kidney, stem and leaflet.
The second sperm fertilizes the central germ cell, and a reserve nutrient appears - endosperm. It surrounds the embryo and forms a seed with it. When favorable conditions occur, it sprouts.
Seed and its structure
Generative organs are organs in which gametes develop, and the seed is the result of gamete fusion. Therefore, it also belongs to this group. The vegetative and generative organs of plants are formed precisely from it.
According to the peculiarities of the structure of the seed, all flowering plants are combined in two classes: monocotyledonous and dicotyledonous. The sign underlying this classification is the number of cotyledons in the seed germ. Monocotyledons include all members of the cereal and onion families . The second group is more numerous. These are rosaceae, nightshade, legumes, cruciferous, aster and others. In addition to the structure of the seed, these classes differ in the structure of the root system, the type of leaves, the presence of lateral educational tissue, and life forms.
Evolutionary paths
Not all plants have seeds. The most primitive - algae - are able to form only spores - asexual reproduction cells . In higher spores, an alternation of generations is observed in the life cycle. Sexual reproduction cells are located in special organs - gametangia. The plant on which they are located is the sexual generation. Merging in pairs, they form a zygote - a fertilized egg. Sporophyte develops from it - an asexual generation that forms unicellular spores. And so it is repeated throughout the life of the plant.
Based on the fact that the organs in which gametes develop are called generative, cones are such formations in gymnosperms . Moreover, the male contains pollen, and the female contains the egg. In this cone, the formation and development of seeds occurs. When the bump matures, it opens. In plants of temperate latitudes, this usually occurs in winter. Seeds fall directly on the snow, and they have few chances to germinate.
The situation is different in angiosperms (flowering) plants. The process of fertilization in them takes place in a flower in which seeds and pericarp are formed. It serves as a reliable protection and source of nutrition for the future adult body. This is the most perfect system that currently exists in nature. That is why representatives of this group of plants are most numerous.
So, the generative organs of a plant are a flower, a fruit, and a seed. Their appearance is very important. Indeed, thanks to the ability to reproduce sexually, organisms acquire new traits that help them adapt to new, constantly changing environmental conditions.