The structure of each organ of plants 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 hasa certain structure, occupies a certain position and performs certain functions. It must consist of several types of tissues. For example, the heart consists of the muscular and connective, and the sheet - from the integumentary, conducting and basic.
Vegetative and generative organs of plants
Depending on the functions performed, there is aa certain classification of these parts of the plant organism. Thus, generative organs are called in which gametes are developing sex cells. They are female (ovule) and male (sperm). The latter differ from spermatozoa in that they are unable to move independently. For fertilization they need wind or water.
Generative organs carry out the function of sexual reproduction. Vegetative, which include root and shoot, provide growth, nutrition of mineral and organic substances.
Escape and its modifications
The aerial part of any plant is calledescape. First of all, it is represented by an axis - a stalk. Shoots are diverse in form: erect, creeping, curly, clinging ... To the axis are attached leaves. To perform additional functions, for example, water supply, protection, vegetative propagation, in some plants, the shoot can be modified. Examples of such structures are the rhizome of irises, a bulb of garlic, a tuber of Jerusalem artichoke or thorns.
Vegetative and generative organs carry outtheir functions in a friendly tandem. After all, for the development of seeds and the ripening of fruits, nutrients are needed that are photosynthesized in the leaves and absorbed from the ground by the root.
Root
This underground organ reliably fixes the plantand is responsible for mineral nutrition. Water between the soil particles contains ions of valuable metals and acid residues. They are a prerequisite for the growth of the plant. These substances along the conductive tissue come up - to the stem and leaves. This motion is called an ascending current. But glucose, formed in the leaves, moves to the root. This current is called descending.
The subterranean organ also forms modifications.So, the root vegetables of carrots and tuberous asparagus store the necessary substances. Ivy trailers allow it to grow on an absolutely vertical surface, and the respiratory roots of the orchid are able to absorb moisture directly from the air.
Generative organs of flowering plants
Bright and beautiful flowers have long been a favoritedecoration and a gift for any holiday. In addition to visual appeal, they carry out the process of sexual reproduction of plants. Plant generative organs are also seeds. They contain an embryo, which over time turns into an adult plant.
Since generative organs are called, inwhich develop sex cells, the fetus also belongs to this group. It is he who protects seeds from the influence of unfavorable conditions, the temperature drop, and promotes their spread.
Flower
Generative organs appear from the same kidney. Its development begins in the spring, when the duration of a light day increases significantly. And the flowers appear before the leaves.
Generative organs of the flower, or rather its part,are represented by a pistil and a stamen. It is in them that female and male gametes develop respectively. Bright petals, the aggregate of which is called a whisk, is necessary to attract insects, which carry out the process of pollination. The lower, enlarged part of the flower is the flower-root. Carpels are attached to it. Their totality is called a cup.
Flowers are quite diverse in featuresThe structures that depend on the characteristics of pollination. If it occurs with the help of wind, they most often do not have a perianth - corolla and calyx. Or he is very small. This is a special device that is aimed at catching pollen. And the flowers themselves are small, inconspicuous, without the smell and aroma of nectar. Their pollen is light, loose, and develops in large quantities in the wind. The flowers are collected in long inflorescence, which swing in the wind.
If pollination occurs with the help of insects, on the contrary, bright coloration, large inflorescences and an attractive aroma are needed to attract them.
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 one-seeded. Each type of fetus has a specific device for spreading the seeds. The lionfish of ash and maple are carried by the wind, with the fall bounce off the seeds of oak and chestnut. With the help of animals, tasty and juicy fruits spread.
What is double fertilization?
Fertilization is the process of fusion of gametes.A feature of this process in flowering (angiospermous) plants is that it is preceded by pollination - the transfer of pollen from the anther of the stamen on the stigma of the pistil. It can be natural - with the help of wind or insects - or artificial - with the help of a person.
Once on the stigma of a pistil, two sperm withUsing the embryonic tube drop into its lower dilated part - the ovary. One of them impregnates an egg. The result of this process is the fetus. It has all the features of an adult organism and consists of an embryonic root, a kidney, a stalk and a leaf.
The second sperm fertilizes the centralgerm cell, and there is a reserve nutrient - endosperm. It surrounds the embryo and together with it forms a seed. When favorable conditions come, it sprouts.
Seed and its structure
Generative refers to the bodies in whichgametes develop, and the seed is the result of the fusion of gametes. Therefore, he is also referred 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 floweringplants are combined into two classes: monocotyledonous and dicotyledonous. The attribute underlying this classification is the number of cotyledons in the seed germ. All members of the cereal and onion family are monocots. The second group is more numerous. These are Rosaceae, Solanaceae, Legumes, Cruciferae, Astros 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 a lateral educational tissue, life forms.
Paths of evolution
Not all plants have seeds.The most primitive - algae - are able to form only spores - cells of asexual reproduction. The higher spore in the life cycle is observed alternation of generations. Cells of sexual reproduction are in special organs - gametangia. The plant on which they are, and there is a sex generation. Pairing together, they form a zygote - a fertilized egg. Sporophyte is developed from it - asexual generation forming unicellular spores. And so it repeats throughout the life of the plant.
Proceeding from the fact that generative organs are called,in which gametes develop, in gymnosperms such formations are cones. And the male contains pollen, and the female contains the egg. In this cone, the formation and development of seeds takes place. When the cone ripens, it opens. In plants of temperate latitudes this usually occurs in winter. Seeds fall directly on the snow, and the chances of germinating from them are not so many.
In the angiosperm(flowering) plants. The process of fertilization 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 organism. This is the most perfect system, currently existing in nature. That is why representatives of this group of plants are the most numerous.
So, the generative organs of the plant areflower, fruit and seed. Their appearance is very important. Because of the ability to reproduce sexually, organisms acquire new signs that help them adapt to new, ever-changing environmental conditions.
