Plant - SpeedyLook encyclopedia

Principal characteristics

Main features of the plants

the plants are organization S Autotrophe S, i.e. they produce their clean Organic matter starting from Rock salt drawn from the ground and of carbon dioxide, assimilated by the sheets thanks to the solar energy: it is the mechanism of Photosynthèse. They owe him, by the means of the Chlorophylle contained in the Chloroplaste S, the Couleur Verte of the plants.
the plants are organizations fixed on the ground by their roots (but there are exceptions), which makes them very dependant on the conditions of their Environnement; this state is dependant on cellulose nature cellular walls , on fabrics of support of the plant (Collenchyme and Sclérenchyme) and on some particular Molécule S as the Lignine which makes fabrics rigid.
the plants are differentiated organizations little . One distinguishes little from types of fabric S or differentiated Organe S, which involves particular properties: a potentially indefinite growth, a capacity of important Regeneration (from where the possibility of vegetative Multiplication).
the plants need various elements gathered to survive and push. The first is the light, useful for the process of photosynthesis, which brings energy. Then water and the ground come from where the nutrients are drawn, and the air from which they extract carbon dioxide, also allowing photosynthesis. The exact conditions vary according to the type of plant.

The plants are organizations which belong to the vegetable kingdom, whereas the plants are, among the plants, the organizations which have roots and an air part.

Vegetable organization

One distinguishes, according to their degree of differentiation, three great types of organization:

the Thallophyte S: live plants in moist environments, characterized by a Thallus, vegetative apparatus little differentiated in form from Blade - Alga S, Lichen S;
the Bryophyte S: they are the foams and the Hépatique S, from which the vegetative apparatus starts to be different in Tige and Feuille. They constitute a new stage towards the passage of the Aquatic life to the terrestrial Vie;
the Tracheophyta (in the past called Cormophyte S): they are the vascular plants or Rhizophyte S, which includes/understands the Ptéridophyte S (Fougère S) and the Spermaphyte S (plants with seeds). The vegetative apparatus is now well differentiated in root, Tige, sheet and especially conducting vessels of Sève (Phloème and Xylème). It is thanks to these conducting vessels and with their drawn up and rigid port (by synthesis of the Cellulose in the intercellular space of these vessels, for the construction of a skeleton of Bois) that these plants are adapted to the terrestrial environment.

Classification of the plants

The first known classification is the work of Théophraste (370-285 av. J. - C.) which classified 480 plants according to their port (Arbre, Arbuste or Herbe) and certain floral characteristics.

At the 16th century, Botanist S, in particular the brothers Jean and Gaspard Bauhin, will start a reflection on the classification of the plants. They seek to establish natural groups of plants starting from their resemblance. Indeed the discovery of new plants made a new classification necessary. It should be known that hitherto, the plants were classified according to their size, of the place where they pushed or of their resemblance.

John Ray (1628 - 1705), English naturalist, proposes to establish a new system of classification having for base the greatest possible number of characters of the Fleur, the Fruit or the sheet.

Then, Pierre Magnol (1638 - 1715), inventor of the term family, indexes 76 family S of plants.

Joseph Pitton de Tournefort (1656 - 1708) establishes a classification of the plants according to the structure of the Fleur S and introduced the concepts of Espèce and kind.

Lastly, Carl von Linné (1707 - 1778), Botanist of the King of Sweden, codifies the nomenclature binominale plants and animals. This system uses two names in Latin: the first indicates the kind and the second, the species of the plant or the animal. On the other hand, its “sexual system” based on the number of cheesecloth S, does not make progress the classification of the plants.

See also the list of the Botanists.

Systematic classification known as “traditional”

According to the authors, the limits between the Vegetable kingdom ( Plantae ) and that of the Protiste S ( Protista ) vary:

for some (Raven, 1992), the reign of Protistes extends from the heterotrophic protists very close to the Champignon S or the animal to the green algas very close to the terrestrial plants; the vegetable kingdom including/understanding only these last still called Embryophyte S ( Embryophyta );
of other authors (Bremer, 1985) gathers the green algas and the terrestrial plants in the taxon monophyletic of the house plants ( Chlorobionta );
the ITIS for its part gathers the whole of the algae and the terrestrial plants in the vegetable kingdom.

Belong to this reign:

The Alga S

Traditionally, only the green algas, or Chlorophytes, were regarded as plants, and thus did not form a under-reign. The classification of the other algae in the reign of the plants is an introduction of the scientific classification started since the XIXe century. Previously, they were classified in a variable way with the protists. Progress in the research of phylogeny still changes the things, since certain classes disappear and that bringings together morphologiquement astonishing take place in classification.

Bryophytes

In traditional or traditional classification, the under-reign of the Bryophyte S ( Bryophyta lato sensu ) includes/understands three divisions (or junctions) or of nonvascular terrestrial plants:

the division of Hépaticophytes ( Hepaticophyta ): 6 000 species of plants Hepatic S;
the division of Anthocérotophytes ( Anthocerotophyta ): 100 species of Anthocérote S;
the division of Bryophytes ( Bryophyta strictly speaking ): 9 500 foam species.

Vascular plants

The under-reign of Trachéobiontes ( Tracheobionta or Tracheophyta ) is made up, according to a traditional classification:

of Ptéridophytes ( Pteridophyta ), or Fern S lato vascular sensu , plants Cryptogam S (with Spore S and Thallus S):

Psilophytes ( Psilophyta ): 17 species;
Lycopodiophytes ( Lycopodiophyta ): 1 000 species, of which the Lycopod S;
Équisétophytes ( Equisetophyta ): 15 alive species of which the Prêle S;
Filicophytes ( Filicophyta ): 11 000 species of Fern S strictly speaking ;

of Spermatophytes ( Spermatophyta vascular , plants Phanérogame S (with Seed S):

Gymnospermes ( Gymnospermae ), the plants phanérogames with cone S;
Angiospermes ( Magnoliophyta ), the plants phanérogames with Fleur S: approximately 235 000 species.

The figures show the domination which exert today Angiospermes ( Magnoliophyta ) among the terrestrial plants.

Phylogenetic classification

to see the articles Archaeplastida (phylogenetic classification) and Chlorophyta (phylogenetic classification)

Classification according to the size and the type of the stem

A great division is often made between the herbaceous plants and the woody plants (those which form Bois).

Classification according to the climate according to W. Köppen

One finds plants almost everywhere on the ground: in the desert, under water, in the tropical forests, and even in the Arctic. However, their distribution on the surface of the ground is function of the ic conditions Climat.

Thus, to give an account of the independent groups of plants, a climatologist and German botanist, Köppen established a classification of the climates. This classification, published for the first time in 1901, and altered on several occasions since, is oldest and most known.

The classification of Köppen includes/understands five groups of climates themselves divided into five climatic types. The contour of each group corresponds to the satisfaction of a criterion related to the temperature of the air or combining at the same time the temperature of the air and the level of precipitations.

Plants of the tropical areas

The tropical zone extends on both sides from the equator between the tropic of Cancer (23°27' of northern latitude) and the tropic of Capricorn (23°27' of southern latitude). It represents one of the great climatic zones born from the general circulation of the atmosphere and its seasonal displacement. It should be noted that this zone covers approximately 45% of the total surface of the forests. The average temperature of the coldest month is higher than + 18° Celsius. The corresponding vegetation is the Tropical forest or the Savane.

Plants of the dry and desert areas

Primarily characterized by the presence of shrubs and grasses which adapted to the ic environment Désert and which, by a system of underground roots not very deep but wide near surface (booklet), manage to collect a quantity of sufficient water to their growth. The Végétation is very little developed and recovers little space. The species are called Xérophyte S (of the Greek xero = dry, and phytos = plant), one finds there Cactus, plants with cuticule thick to limit the evapotranspiration, plants in bearings, the succulent ones ( example family of Crassulassées, of which Sedum or the Joubarbe). The majority of the chlorophyllian plants of these areas function thanks to photosynthesis in C4.

Plants of the moderate areas

In Europe, this forest extends from the northern forest to the Mediterranean forest (between 40° and 55° northern). The thermal mode is moderated with in winter a little freezing on the upper part of the grounds, and a moderately hot summer. One can distinguish three dominant species.

Plants of the cold or subarctic areas

One distinguishes two great types of vegetation in polar and sub-polar medium:

the Tundra: located between 55° and 70° northern, it is a vegetation dominated by grasses and the foams, often associated with various shrubs. It is a continuous and low vegetable formation with the absence of trees because of an in-depth cold ground permanently, the Pergélisol (temperature lower than 0° C). The absence of trees is also due to a shortening of the growing period (the summer lasts sometimes only one to two months).
the Taïga: northern forest large Coniferous S, typical of Siberia and Canada. The winters are longer and more rigorous and the summer months are hotter (higher temperature with 10° C). It is considered that represents the limit between taïga and the tundra. The underwood consists of several conifers with needles and ferns.

In the southern hemisphere, this vegetable formation is more reduced (in the islands of the Antarctic, the tundra in tufts dominates the area).

Plants of the polar regions

Plants of the areas of high mountains

Classification of the biological types of Christen Christiansen Raunkiær

References

Random links:

Electrophoresis of proteins | Ghyslain Tremblay | Let' S Knife | Woluwe-Saint-Etienne | Anamorph (film)