Aecie

Schematic drawing of a leaf infected by rust fungi in cross section. You can see different forms of aecia ( per - peridermium; ae - bursting aecidium) and spermogonia ( sp ) of the secondary fruit form (I) as well as uredo ( un ) and teliospores ( pucc ) of the main fruit form .

Cup-shaped aecia (so-called aecidia) of Puccinia sessilis on the underside of the leaf of a spotted arum

The aecie or the aecium is a form of spore storage that occurs in the byproduct form of rust fungi (Pucciniales), which grow as endoparasites of vascular plants . It is a mycelium with binuclear cells that form so-called aeciospores through constriction . They form the first two- nucleus phase in the life cycle of a rust fungus and arise when the single- nucleus receptive hyphae of the spermogonia take up a nucleus of a sperm of the same species and then form a dikaryotic mycelium. Their aeciospores usually germinate to form parts or uredia on another or the same host. Depending on the shape of their Aecien be rust fungi whose perfect state is not known, in different form genera divided: Caeoma for easy Aecien without peridia (vessel walls), Aecidium for cup-shaped spore bearing with the top side open peridia, Peridermium for Aecien with first dome-enclosed walls and Roestelia for those Species that form grid-like peridia. The designation for the respective Aecia forms corresponds to that of the anamorphic genus .

Origin and structure

Aecia are made up of a basic layer of binuclear basal cells. They arise from a mycelium that grows from the spermogonia mostly from one side of the host leaf to the other. It primarily serves to pass on cell nuclei that the recipient types have received from the spermatia and is a prerequisite for bisexual cells to be able to form at the base of the developing aecia. The binuclear basal cells can on the one hand tie off peridial cells through division, which serve to stabilize the spore bed, on the other hand they can also form aeciospores through long, pearl-like cell chains. The latter, like the mother mycelium, each have two different nuclei and serve to spread the fungus. Wherever they fall on a suitable host, they can penetrate through its stomata and there form either uredia or telia , with which the transition from the minor to the main fruit form is completed.

Importance for the taxonomy

Even if the morphology of the Aecien does not provide any information about the genetic relationships of different species, it was and is used in mycology to classify the anamorphs of rust fungi. This classification is particularly important where the main fruit form of a species is not known and a preliminary description should nevertheless be made. The rust fungi are usually divided into four different anamorphic genera:

• Caeoma - simple aecia without peridia (caeomania with caeomaspores)
• Aecidium - cup-shaped aecidia with open peridial tissue on the top (aecidia with aecidiospores)
• Peridermium - Aecien with initially closed walls like a dome (peridermia with peridermiospores)
• Roestelia - Aecien with grid-like wall structures (Roestelien with Roesteliosporen)

swell

• Heinrich Dörfelt , Gottfried Jetschke (Ed.): Dictionary of mycology. 2nd Edition. Spectrum Academic Publishing House, Heidelberg / Berlin 2001, ISBN 3-8274-0920-9 .