Plants produce oxygen by photosynthesis. By this same mechanism, plants transform mineral carbon into organic carbon usable by animals. Plants are autotrophic (self nourishing: producers) contrasting with the heterotrophic animals (consuming other living things: consumers). The plants are thus a paramount element of any food chain. Plants allow many animal species to live: either as being their host, or as food. It is thus possible to design food chains without animals but there are none without plants. Plants also facilitate the penetration of water into the soil and limit the run-off of rainwater. They make it possible under more arid climates to fight desertification. Plants, thanks to their roots, stabilise soil. See: dune, stranding, defense and soil conservation, landscape restoration. Plants are also important for the fertilization of soils (humus). Plants are source of life for Mankind. For people, plants provide nourishment (food, condiment plants), protection (fuel wood, houses), amenity (furniture, materials), and medicine (medicinal plants). Crop plants are bred to maximise yield and are genetically rather uniform compared to wild relatives. Wild plants potentially offer the genes of resistance to the crop diseases. Relatively few plants have been exploited for medicines. The whole plant kingdom presents a potential reservoir of medicinal uses (substances, drugs…). The vast genetic resources of the plant kingdom require conservation to protect biological diversity and secure the future of Mankind.
The following pictures show the 2 main categories of placentation : – when placentation is axile, placentas link seeds and fruit axis : example of a tomato (Lycopersiconesculentum, Solanaceae), – when placentation is parietal, placentas link seeds and fruit wall : example of a kiwano (Cucumismetuliferus, Cucurbitaceae). The following sketch explains the different evolution states from free carpels in an apocarpous gynaecium to fused carpels in a syncarpous gynaecium with axile or parietal placentations: – Axileplacentation. Carpel sides are fused together in septa (plural of septum). Carpel margins are found on the axis of the composed ovary. Ovary is plurilocular. Placentas (conducting tissue for ovules) and ovules are located along the ovary axis: placentation is axile. – Parietal placentation. Carpels are fused by their margins and placentas develop along the composed ovary wall. Ovary is unilocular.
Differentiated management is a concept of maintenance of the green areas which currently develops. It makes it possible to recreate biological diversity in the pleasure gardens.
Differentiated management consists in carrying out a maintenance different according to the zones from the garden. For example, shearings in a garden of French style will be more frequent than in an English garden where to the extreme in a meadow. One of the management tools differentiated is thus a precise cartography of space: the various zones are defined according to their use, their ecology like according to their biological, current or potential richness. For each zone, the means and the frequencies of maintenance are defined. Unlike reasoned agriculture for which, also, maintenance and the treatments are weakest possible, there is no concept of production in a pleasure garden except if one says that a differentiated management makes it possible “to produce” biological diversity. Continue reading Management differentiated in the gardens→
Ancestral land plants appeared about 410 million years ago. Compared to green algae, land plants are characterized by a waterproof cuticle limiting dehydration and protection of spores that are enclosed in a sac protected by an envelope. Ferns and related plants have conducting tissues which help to grow above the ground. The most derived taxa are heterosporous in order to statistically increase genetic intermixing. Among ferns, pollen grains do not exist and spores are the way of species propagation. More fragile than pollen, these spores will under favorable conditions (a moist and shady land), give birth to a flattened and green body, a prothallus. At this stage, gametes will be produced. Once fertilization is realized, a new fern will be formed. These stages, especially prothallus growth and fertilisation, needs a moist land or water (sperm swims in water to reach the female organ). —- Continue reading Flowering plants pollination (angiosperms)→
Methods of development of an herbarium General Principles After their determination and their identification, the plants are dried under press before being fixed by adhesive without acid on paper without acid. The boards are then gathered by family by respecting a phylogenic classification. Technical AdvisesDrying The plants are dried in newsprint which is changed regularly until complete drying (except, the sheet directly in contact with the plant). When a batch of plants is thick, it is recommended to place some boards of rigid paperboard to avoid the deformation of the plants. Pressing. It is not necessary that the plants are crushed. The press can be simple. For example, press can be easily made up of 2 grids of refrigerator maintained tightened by straps or various masses distributed uniformly on the surface of a board. Quality of the exsiccata. To obtain samples of quality, drying must start as soon as possible after harvest. It is often noted that the plants lose their color after drying, except those containing sulphur (example naturally: garlic). To cure this disadvantage, the plants can be put in the presence of sulphur vapor just after harvest. The sulphur pastilles used for the sterilization of the wine barrels are appropriate. However, this method is tiresome. Cost of development the size of the boards is, commonly, of approximately 45 cm X 28 cm. However, these dimensions do not constitute an obligatory standard. Thus, Fournier indicates in the Four flora of France (1977, republication) that the herbarium itself can extremely well be made up on small size, for example on paper folios with machine (to be written). The boards which I use measure 32 cm X 29 cm and more than have an unit cost partial (except labour) 10 times lower than that calculated for the traditional boards, while respecting the schedule of conditions according to: paper and adhesive without acid, grammage raised, translucent paper (Bray and Al, 1997). The adhesive used to fix the dried plants can be paste distributed with a glue gun or rubber cement. This last product is sold under various marks but will always have the same chemical composition, containing natural rubber. Labelling The label or the data-processing recording of each board must comprise following information: – a reference number, – the family, the kind, the specie and the possible names infra-species.These indications must respect the nomenclature in force, – abbreviation of the name of the specific author, – the possible synonym, – the date of collection, – the place of collection. The use of a system of total positioning is recommended. It will make it possible to specify the latitude and longitude. For altitude, taking into account the error of the apparatus, it is preferable to use an altimeter, – the name of the collector and/or the name of the identifier, – the description of the biotope or phytosociological association (this last indication can, possibly, not be present on the label if it already exists in the data base computerized). In the case of the first labelling, the label is placed in bottom and on the right. If it is about a label bringing of the corrections, it must be placed in bottom and on the left.
Botanical and biodiversity Window
Veuillez accepter l'utilisation des cookies pour vous permettre de disposer d'une navigation optimale. Plus d'infosJ'accepte