Botanists have counted more than 360 thousand species among flowering plants. And this account is not over. Flowers are found from the tropics to the tundra - in all climatic zones of the planet. They are everywhere: in deserts, in forests, steppes, swamps and lakes, on sea coasts and in high mountains. It is the flowering plants that make up the bulk of the plant matter of the biosphere. Thanks to them, plant foods are formed - cereals, most vegetables and fruits, berries and nuts.
The most important element of angiosperms (the second name of flowering plants) is a flower. The main parts of a flower are the pistil and stamens. Thanks to the most complex processes of pollination and fertilization with their participation, seeds are formed - the continuation of the life and evolution of plants on the planet.
Flower: structure and functions
Higher plants consist of a root, a stem with leaves and flowers, which are shortened and modified stems. The root, stem and leaves are the vegetative parts that are responsible for the growth of the plant. Flower -generative element, reproductive organ. Usually the flowers are attached to the pedicels - this is the name of the thin part of the stem without leaves. Some plants have no pedicels or they are barely pronounced. These are sessile flowers. Pedicel expands into receptacle.
Let's list from bottom to top, starting from the pedicel, the main parts of the flower. This is a receptacle, which is the foundation for placing the rest of the elements of the flower. The receptacle can be of various shapes: from conical, like a magnolia, to flat (chamomile) and even concave (rose hip), starting from the calyx, which is formed by the sepals. They are usually green, but can be brightly colored. The calyx may be single row or with a subcalyx formed from the second circle of sepals. Next - the corolla of the flower, made up of petals. The variety of flower corollas is great: by color, color intensity, size, quantity, shape, mutual arrangement, cleavage of petals.
Together, the sepals and petals make up the perianth - the cover of the flower. Some flowering plants do not have petals or are indistinguishable from sepals. In such cases, the perianth will be simple; it is called double if there is a sepal and petals. The perianth is a sterile appendage of a flower. The functions of the flowers assigned to the perianth are the protection of the carpel (pistil or carpel) and the guarantee of pollination. The bright colors of the corolla and the attractive smell ensure that the plants are visited by insects.
In the perianth arespore-bearing, no less important parts of the flower. This is a gynoecium, more simply - a pistil, in which the ovules develop with a receptacle for the gametophyte (megaspores). It is the female reproductive organ of the flower. The perianth also contains the male reproductive organ, the structural unit of which is the stamen. Collectively, the stamens are called the androecium. Microspores are formed in the staminate anthers. They produce a pollen grain - the male gametophyte.
The main parts of a flower
The pistil and stamens are the most important elements, as they are the suppliers of female and male reproductive cells. These are gametophytes, substances from the fusion of which the seed and fruit of flowering plants are born. The pistil (it is more correct to call it a carpel) consists of an ovary, a style (some flowering plants do not have one) and a stigma. The ovary contains an embryo sac containing ovules. The top of the style ends with a stigma on which pollen lingers. It is formed in stamens (microspores). A typical stamen consists of two parts: a filament (sterile, sterile part) and an anther with a fertile (fertilizing) function.
Single and dual house
About 75% of angiosperm species have bisexual (hermaphroditic) flowers - they have both stamens and pistils. These plants are monoecious (an example is corn). There are plants in which some individuals have only staminate flowers, while others have only pistillate ones. They are called dioecious (cannabis is an example).
Pollination process
The essence of pollination is getting on the stigmapollen from stamens. This may be self-pollination, a classic example of which is observed in non-opening flowers (some types of violets, peanuts, barley). The second way is cross-pollination, which occurs in most flowering plants. Some pollen vectors: wind, water, insects, ants, birds.
Double fertilization
When a male gamete (sperm) fuses with a female gamete (ovum), fertilization occurs. To do this, it is necessary that stamen pollen germinate on the stigma of the pistil, moistened with a sticky sweet liquid. A pollen tube begins to grow at a germinated dust grain - very long and very thin. It penetrates into the ovary close to the ovules. Two sperm are attached to the end of the tube.
Seeds, consisting of cells, develop inside the ovary. The egg is located close to the pollen passage, into which the pollen tube penetrates. Another cell, secondary, is located in the center of the ovary. The pollen tube bursts and both sperm come out of it. One of them penetrates the cytoplasm and merges with the nucleus of the egg, and the other penetrates into the secondary cell. Fertilization occurs, and the egg begins to divide multiple times, due to which the embryo of the plant develops. The secondary cell is also fertilized and begins to divide with the formation of the endosperm - a storehouse of nutrition for the embryo. This is how the seed is formed.
Briefly about the function of flowers
Flowering plants in the flora of the planet occupy a dominant place in their development, just like mammals among the fauna. purposeof all living things - to prolong their kind, to create their continuation. This is also what the flowers are striving for. Their reproductive organs, which perform the function of reproduction, are flowers. The main parts of the flower are the gynoecium (pistil) and androecium (stamens), which form the sex cells - gametes. In flowers, after pollination, sexual intercourse takes place - copulation of gametes. As a result of double fertilization, seeds in the skin with a supply of nutrients develop from the ovules of the ovary. This is the beginning of a new life for subsequent generations in the flowering families.
