Among the current Plant S, the bryophytes are those which preserved the most characters of the first plants having colonized the dry land. Their ancestors seem to be green algas Charophycée S. Même if certain anatomical structures enable them to resist the Dessication, the bryophytes are still extremely dependant on moist environments, or in any case of a minimal Hygrométrie.
Taken with the broad direction the term bryophyte applies to the three junctions of terrestrial plants which do not have a true vascular system whereas the junction of the Bryophyta relates to only the foam S with the strict botanical direction.
Situation of the bryophytesAs for all the Alga S and the house plants, one observes an alternation of Sporophyte S and from Gamétophyte S, but, as for all the Embryophytes, the Anthérozoïde S (or Spermatozoïde S) are protected by Anthéridie S and the Oosphère S by Archégone S (characters shared with the vascular plants). Fecundation is watery (oogamy), the Anthérozoïde S (or Spermatozoïde S) ciliés must find a means of joining the oospheres. The embryo which results from it is nourished and protected by the Gamétophyte (Matrotrophie). The Sporophyte never becomes independent of this one. The haploid gamétophyte is thus the stage dominating under which the plant meets. The Spore S are surrounded by a wall containing of the Sporopollénine which protects them during the dissemination.
Bryophytes do not have of Xylème and Phloème (conducting fabrics of water and food) which appears only at the vascular plants. Some however have specialized conducting fabrics but which are not lignified: leptoïdes and hydroïdes.
The pseudophylles do not have the Histologie true sheets.
There do not exist bodies comparable with the roots at the bryophytes but of rhizoid mono or pluricellular which fix them at the substrate.
most of the life cycle is carried out in the form of Gamétophyte S males or females (in red). In certain cases, in particular at the anthocérotes, the gamétophytes are bisexués and nourish then many Sporophyte S.
water is essential at the time of fecundation so that the Anthérozoïde S (or Spermatozoïde S) ciliés can reach the oospheres.
After fecundation, the embryo matotrophe is carried by the gamétophyte female and gives a sporophyte often formed of a silk and a Sporange (in green).
the sporange releases from the male and female spores (except in the case of the bisexués gamétophytes) which, in foams primarily, develop in the form of Protonéma before producing the gamétophytes.
the mobile stages (in yellow) are mainly the spores for which foams developed mechanisms ensuring their dispersion (explosive capsule of the Sphaigne S, slits of déhiscence of the Andréale S, Péristome of true the foam S) and the Anthérozoïde S (or Spermatozoïde S) before fecundation.
the bryophytes can multiply in a vegetative way by fragmentation. Some Hépatique S developed special structures dispersing of the “propagules”. Particular structures also exist in certain foams.
Bryophyte, Environment and pollution…Bryophytes, and foams in particular draw the essence of their food from the air and the nutrients brought by the rain or the deposits of particles.
Ils for this reason plays a big role in the air-cleaning, but also accumulation of certain pollutants (Heavy metals and Radionucléide S in particular). They are also organizations pioneers important in the ecological processes of Résilience.
The species most sensitive to the acid pollutants and the pesticides conveyed by the air and the pesticides sometimes disappeared from whole or part of their natural habitat. Certain species could be regarded as bioinidcateurs, as regards thermohygrometric quality of the air in particular. From their natural resistance to many pollutants they do not make goods Bioindicateur S of pollution, but like Bioaccumulateur S, they can make it possible to chart the pollution present and of a recent past. Were used they for example to chart pollution by the Plomb or the Cadmium.
Classification of the bryophytes
- Hepaticophyta (Hepatic S), the junction with the characters most primitive (6000 species surroundings)
- Marchantiopsida (hepatic with thallus complexes)
- Jungermanniopsida (hepatic with simple thallus or sheet; approximately 4000 species)
- Anthocerotophyta (Anthocérote S) small junction close to hepatic (a hundred species) the
- Bryophyta (foam S), nearly 10000 species in 3 classes
- Sphagnopsida (sphaignes)
- Andreaeopsida (andréales)
- Bryopsida (true foams)
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