Representatives of the plant world can be found everywhere. Algae live on the seabed, and mosses are found on the mountain peaks. A variety of flowering plants occupy vast spaces on the continents, the most important for the life and economy of the population.
Material Content:
Types and varieties of angiosperms
The flora of the Earth is rich and diverse, with more than 500 thousand species. Angiosperms - the most numerous and highly developed group of plants. It consists of classes of dicotyledons and monocotyledons, subclasses of orders and families. In total, 418 families are known, about 199,000 dicotyledonous species; 125 families, about 60,000 species of monocotyledonous plants.
Species are living organisms with similar characteristics. Groups of species that differ from others but are similar to each other are combined into genera.
Distinctive features of monocotyledons: the presence of one cotyledon in the seeds, fibrous root system, arc or parallel venation of leaves. The structure of a flowering plant from the class of dicotyledons is distinguished by the rod form of the root, cirrus or palmate venation. Seeds consist of two cotyledons.
In accordance with the current rules, each species has a scientific name, consisting of two parts: the name of the genus and species. For example, the genus Apple tree unites more than 60 species. Four species - low, forest, Chinese, berry apple trees - served as a material for the cultivation of modern varieties.
A cultivar or variety combines cultivated plants that differ from others in their characteristic characteristics: shape, color, crop ripening time, resistance to low temperatures, and diseases. During reproduction, typical characteristics are retained.
The structure of a flowering plant, description
The vegetative organs of a flowering plant — the root, stem, and leaves — vary in size. The diameter of duckweed leaves reaches 5–8 mm. The stem of a giant eucalyptus grows 100 m in height.
Vegetative and generative organs
The hairs on the root surface absorb water and salts dissolved in it, which penetrate through the conducting vessels into the aerial part. Some plants store nutrients in underground organs.
The stem connects all the parts into a single whole. At the very tip is the apical kidney. The part of the stem with leaves and buds that has grown during one growing season is called an shoot. Some species store nutrients in rhizomes, bulbs and tubers. Such modified shoots have lily of the valley, onion, tulip, potatoes.
Leaf is a vegetative organ that performs the functions of photosynthesis, gas exchange, and water evaporation. It consists of a leaf blade and petiole, which is attached to the stem. Spines in cacti, tendrils in peas, succulent onion scales — modified leaves.
A flower is an organ of seed propagation. The expanded part or receptacle serves as a place of attachment of sepals and petals, stamens and pistils. Green sepals form a cup, colored petals - a corolla. Stamens with anthers, pistils with ovaries and ovules are the main parts of the flower.
In pollen grains, male sex cells (sperm) are formed, which are necessary for the fertilization of female sex cells in the ovaries. Seeds - ripened ovules enclosed in the fruit. These organs contain protein, sugar, starch, fats, water and minerals.
How pollination occurs
The essence of this process is the transfer of pollen from anthers to the stigma of a pestle. There are self-pollination and cross-pollination by wind, insects, birds or other animals. You can transfer pollen from the stamens to the pistils with a brush, brush. Artificial pollination is carried out by humans to breed new varieties and increase productivity.
Why is flowering called double fertilization
First, the pollen grain sprouts, a tube is formed, directed towards the ovary. Through this channel, two sperm penetrate the seminal germ, where fertilization should occur after pollen enters the stigma of the pestle. One male reproductive cell fuses with the egg, forming the embryo of a new plant. Another sperm fuses with the secondary nucleus. An endosperm is formed - the nourishing tissue of the seed.
Not only the egg is fertilized, but also the secondary nucleus. This is double fertilization in flowering plants. Subsequently, a seed develops from the seed germ in which there is an embryo and nutrient tissue. From other parts of the flower, a fruit is formed.
Propagation of flowering plants
The formation of a young plant can occur from leaf cells, stem, root, shoot and its modifications. Lily of the valley and wheat grass breed rhizomes; lilies, tulips and daffodils - bulbs; strawberries and saxifrage - mustache. Parts of the root breed sow thistle, dandelion. Branches of willow, poplar root, falling into moist soil. The roots grow from the leaves of the uzambara violet, begonia.
Seed or sexual reproduction of flowering plants - the formation of a new organism from the germ cells of a flower.In indoor floriculture, agriculture, seeds and all methods of vegetative propagation are used, including division of a bush, rhizomes, and tubers.
They root part of the shoot without separating from the mother plant. So propagated by layering. Cuttings are cut from shoots, stems, roots of the mother plant, planted in raw sand and covered with a transparent plastic glass or plastic bag. After some time, the separated areas take root.
Vital activity of angiosperms
Living cells in the composition of the organs feed, breathe, multiply. The root system and the aerial part grow, qualitative changes occur. The whole body grows in size, develops.
Perennial grasses, shrubs and trees are capable of repeated reproduction. The aerial part dies at the end of the growing season or after seed maturation in grassy annuals, biennials and perennials. The latter retain renewal buds on rhizomes, tubers, and bulbs.
Annuals in one season of vegetation manage to start and complete the formation of all organs from one seed. For several months they completely go through the life cycle. In the first year, biennials form a rosette of leaves. The next year, the stems grow, flowers bloom, the seeds ripen, after which the plant dies.
Growing Features
Different types adapt to certain environmental parameters. In relation to light, shade-loving, shade-tolerant and photophilous plants are distinguished. There are drought tolerant and hygrophilous species (with respect to water). Heat-loving plants prefer temperatures above 18 ° C. Cold-resistant and frost-resistant species are able to tolerate lower temperatures of air and soil.
In agriculture and ornamental floriculture, varieties and hybrids prevail, which differ in large fruits with good taste. Such plants need to create optimal conditions: the intake of all nutrients, sufficient moisture, pests and diseases.
It is also necessary to take into account that winter crops germinate from seeds in autumn and winter in the form of a rosette of leaves. In the spring, the shoot starts to grow, flowering and fruiting begins earlier than in spring annuals.
The value of plants in the ecosystem
Angiosperms are found in almost all natural areas: from the cold tundra in the north to tropical deserts and jungles near the equator. They dominate on land among other parts of the plant world and form the basis of most ecological systems.
Angiosperms are an important component of the biosphere, they are necessary for the life of terrestrial animals and humans.
Environmental Impact:
- enrichment of the atmosphere with oxygen;
- carbon dioxide absorption;
- increase in air humidity;
- soil structure improvement;
- soil consolidation;
- climate mitigation.
Angiosperms have amazing environmental plasticity, can adapt to various habitats. However, changes in the environment negatively affect the life of organisms. It is necessary to protect flowering plants - “green lungs”, the basis of natural zones, decoration of any corner of the Earth.
