Marchantiales

Well liverwort ( Marchantia polymorpha )

The Marchantiales are an order of mosses within the liverworts, with around 180 species.

Features

Structure of the thallus

The Marchantiales, are complex thalloid, ie surface Sprouting liverworts. When the thallus can be a top and a bottom make. There are unicellular root-like structures called rhizoids at the Thallusunterseite. The rhizoids attach the thallus to the soil causing him water, but are not related ( homologous ) to the roots of higher plants. Furthermore, can be found at the bottom of multicellular abdominal or Ventralschuppen. Both rhizoids and Ventralschuppen, have the function of water absorption.

The thallus itself can be vertically divided into two layers. The base contains so-called oil cells that store lipids, water-storage cells and chlorophyll- poor parenchymal cells. In the upper half can be found regularly arranged large Interzellularäume, in the " pins " a few cells, so-called extend and partially come close " assimilators ," to the upper epidermis. These are rich in chloroplasts and are mainly used in photosynthesis. This arrangement of the assimilators in the air-filled intercellular spaces ( air chambers ) is used for efficient gas exchange. The Interzellularparzellen each have a Atempore that is simple Thallusöffnung or a complex barrel- shaped structure. In the latter, the cell collapse upon drying, thereby closing the Atempore and prevent further loss of water.

The thalli generally have only weak midrib at the Marchantiopsida. The Marchantiales there are only three genera with vegetative propagation, including Marchantia. This form brood cup, in which a large number of propagules are formed. These occur standing in the incubator cups, so do not have top and bottom. Only after the distribution develops from a dorsiventral thallus. Spread is through raindrops hurl the propagules from the incubator cup (splash -cup mechanism).

Gametangia

The gametangia ( tissue for the formation of gametes) are located at the Marchantiales on typical umbrella-like stalked Gametangienständern ( Gametangiophore ), which are usually dioecious. So there are male and female Gametangiophore. The male Antheridiophore bear the antheridia on the top, where they sunk into the often lobed eight times weak, disc- shaped stand sitting. The archegonia are formed at the bottom of schirmchenförmigen Archegoniophoren, where they are in radial rows.

If the sperm are mature, then begin the lining cells to become congested with moisture and swell, so that the sperm are forced out. When it rains, the sperm are injected under the umbrella of Archegoniophoren. Hence the lower than the Antheridiophoren Archegoniophoren. There are also sessile Gametangiophoren, here takes place the transport of spermatozoa through the rain water on the Thallusoberfläche. Regarding the height of the Gametangiophoren there is between the seated and 10 inches of height all intermediate stages.

Sporophyte

The sporophyte is, as in the Marchantiopsida generally typical, long hidden in the Archegonienhülle. The few days after fertilization, the developing embryo grows from a small Sporogon which is phytosynthetisch active, but is physiologically completely dependent on the mother plant. The Sporogon is as good as sessile and very small compared to the gametophyte, compared to all other groups moss. It sits at the bottom of the Archegoniophors and opens with four to six longitudinal cracks. The spores are then spread by the wind. In some genera ( eg Corsinia ) the Sporogon remains embedded in the thallus, so that the spores are released only after Fester of the gametophyte.

Antheridienständer

Female gametophyte and sporophyte

Thallus in plan and cross section

Occurrence

The species have occupied a wide range of ecological niches. There are representatives in alpine Schneetälchen (Aster Ella lindenbergiana, Sauteria alpina), types of stream banks ( Conocephalum conicum ) and in swamps ( Marchantia aquatica ), but also in arid and semi- desert locations ( Targionia hypophylla, Plagiochasma rupestre ). The species on dry sites roll in a drying their thallus. The then upturned Ventralschuppen provide radiation protection.

System

The order includes four sub-orders with twelve families and a total of 180 species:

• Subordination Marchantiineae Family Aytoniaceae
• Family Cleveaceae
• Family Conocephalaceae Cone head Moos ( Conocephalum conicum )

• Family Corsiniaceae
• Family Cyathodiaceae

• Family Monocarpaceae

• Family Targioniaceae

The moon cup moss ( Lunularia cruciata ) has long provided to the Marchantiales applies since molecular studies but as a separate ( monotypic ) order.