Sunday, December 26, 2010

Sea lover

I present to you one of the few ferns in the world that lives by the sea, Asplenium marinum. His attachment to the sea is so great that live saltwater that comes with the spray of the waves when waves hit the coastal rocks and sea air humidity that condenses on their fronds.

Asplenium marinum in May on the coast of Faial Island in the archipelago of the Azores a few meters from the sea.

Over millions of years has adapted to this habitat so peculiar, so that the salt does no harm as they have mechanisms to prevent osmotic its roots absorb and excretory system to remove the little that is able to penetrate into the tissues . The excretory system is very intelligent. Asplenium marinum sends all the accumulated salt in their tissues to the old fronds are almost withered and dry. This is a very clever manages to keep free of salt most tender fronds. What will kill the vast majority of ferns for him there is no problem.

Extending this picture with a double click you can see the curious grooves adorning his spine.

Its fronds are leathery or plastic, a vivid green color and a length of between 5 and 25 cms. The spine beam is crossed in its entirety by two grooves that channel moisture to the roots in their fronds condensed from the sea breeze each morning rises from the sea and covers everything wet. Thus, although it does not rain for months, get the necessary moisture to live.

Mature sori keen brown to mid-May.

On the underside of the pinnae is the reproductive system in the form of thick sori filled sporangia without indusium.

Sporangium of Asplenium marinum before spore dispersal.

Sporangium of Asplenium marinum filled with spores contained in a transparent bag, formed by a membrane in the photo is torn. The ring is partially deployed and for some reason has failed to disperse the spores.

A sporangium has a structure and functions similar to those of the uterus of mammals. Each of the sporangia that form a sorus is attached to the surface of a pinna with a kind of umbilical cord called sporangiophores, which is nothing more than a hollow tube of cells, where the sporangia gets the nutrients it provides the pinna.

Empty sporangia completely deployed appreciate that very well all the parts that form. To the left is the tube of hollow cells called sporangiophore, which the pinna nourishes the sporangium.

The nutrients pass into the ring of cells that serves as the placenta and embraces the spores contained in a transparent membrane in a pouch. Spores receiving nutrients through the ring and mature. Meanwhile, the ring, as well as a uterus surrounding the spores and feed as a placenta, accumulating power and standing in tension. When at last the spores are ripe and the fern detects that the conditions of humidity and temperature, the ring is displayed as a catapult with unusual force, the membrane of the bag is torn and the spores are thrown as far as possible , at the mercy of wind and water to find an ideal location for germination.

Spores rather small, as most diploid ferns.

The spores that manage to fall into a small crack in a coastal rock containing a small amount of substrate, they germinate and, after the union of gametes, the birth of a new fern love the sea.

Asplenium marinum tiny newborns. At this stage of its development are a single frond green heart-shaped, arising from the fertilized oosphere a gametophyte.

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