During the last day, I participated in a little Field Trip to the Ruhr-University in Bochum (Western Germany). The topics of this field trip were Bryophytes and Lichens; some of the lesser organisms of nature. However, both are very interesting lifeforms and in this article, I want to give you a small introduction towards Lichens and Bryophytes. It's a very complicated topic, so my goal is to explain you some basic information about these two types of organisms and show you some species, which we've founded during the Field trip.
Lichens are a very unique type of life. In fact, they're composite organisms, a symbiosis between a Fungus and a photosynthetic partner like an alga or a cyanobacterium. The purpose of this connection is to improve the living conditions of both organisms. However, the fungi benefit a lot more of this symbiosis. Through the photosynthesis of the alga (or cyanobacterium), the fungus has a completely new source of nutrients. But the alga has also an advantage, because the mycelium of the fungus is a good, moist habitat, which protects also from sun radiation. Thereby, Lichens are very undemanding and are able to settle on many different places like rocks, walls but also on wood, stems and so on. To colonize such places is the main advantage of lichens towards over organisms.
Lichens are classified by their habitus and the way they grow. The main types of lichens are
- crustos: The lichens has a very flat form like a crust with a scurfy, rough surface. Crustos lichens are typical lichens of walls and Rocks.
- Leafy: Leafy lichens grows area and have a leaf-like thallus (name). The purpose of this habitus is to created a big photosynthetic area like the leaves of the higher plants. Leafy lichens are rich in forms.
- Branched: Branched Lichens have a shrubby habitus with long “branches”. They often hang from trees and other places.
- gelatinous: The Thalli (bodies) of these lichens are spongy and swollen. This is a side effect of the symbiosis with cyanobacteria; so gelatinous lichens have often a black or dark blue color.
The first Layer (A) is the outer bark. It's a dense web of hyphae, which protects the lichen from outer influence. Below the first layer is a loose web of hyphae (B). Here, the algae have settled within the cavities between the hyphae. The third layer (C) is also very loose layer of hyphae but without any symbiont. Finally, the last layer is again a dense web of hyphae and forms the inner bark (D), which lies on the substrat. The Rhizines (E) are root-like hyphae (no real roots). Their function is to anchor the plant on the substrate.
Bryophytes belong to the lesser plants; developed from green algae over 450 Million years ago as one of the first tries of vegetable life to settle on land. However, the main difference between Bryophytes and the Higher Plants (Tracheophyta) is the lack of any vessels. The Bryophytes also have no real leaves, stems or roots, but similar organs called Phylloidae (leaflets), Cauloidae (stem-like structures) and Rhizoidae (root-like structures).
Because of this, Bryophytes cannot control their water cycle and habe no protection against evaporation. However, Bryophytes have the ability to dry out and renature again by wetness. In Biology, this ability is called Poikilhydry
All Bryophytes producing spores as main way of reproduction. The life of a Bryophte is divided into two stages.(s. Picture). The haploid stage is the Gametophyte and the diploid stage the Sporphyte.
In short, the diploid Sporophyte creates spores through meiosis. These spores are located within a spore capsule. After spreading, the spores germinate and form the haploid Gametophyte, which is also the “green part” of the Bryophytes. On this Gametophyte, the Gametangia (the sex organs) are located. There are male and female Gametangia and Bryophytes can also be monoecious or dioecious. The male sex organ creates sperms, which fertilize the female sex organs. Through their fusion, the diploid stage will be started and the sporphyte grows directly on the Gametophyte. In the most cases, the sporophyte is only a brown, inconspicuous structure in comparison to the Gametophyte. This domination of the haploid stage over the diploid is also another different between Bryophytes and higher plants.
In classic taxonomy, the Bryophytes are subdivided into three divisions
- Liverworts (Marchantiophyta): The habitus (Thallus) of the Gametophyte is lobed to ribbon-like and very small (often only a few millimeters). The Sporophyte is short-lived and inconspicuous. The Thallus is also very oily.
- Mosses (Bryophyta): the “classic” Bryophytes. The Gametophyte looks like a small plant with leaflets, a stem-like and a root-like structure. The Sporophyte is brown with a long stalk (Seta) and a spore capsule. This capsule is often locked by a hat (Calyptra). The Bryophyta has know oil glands.
- Hornworts (Anthocerotophyta): Thallus of the Gametopyhte similar to the liverworts with a lobed habitus. Also very small. However, the main difference is the creation and location of the sex organs and the Sporophyte. They are formed endogenously and don't sit on the Gametophyte. Because of this, the mature Sporphytes looks like the horns or funnels of the Gametophyte.
The field trip was held at the Campus of the Ruhr-University in Bochum (Western Germany). It was founded in 1962. With 30.000 students, the Ruhr-University belongs to the Top 10 of Germany's biggest Universities today. The total area of the Campus is 4,5 km² (450 ha). Many buildings on the campus are made of concrete. Concrete consists of many different kinds of stone, so it's a good surface for lichens and Mosses. Another important factor are the exhaust of the cars, which help the spores to spread.
Campus of the RUB
So, the Campus of Ruhr-University is a good place to find many different species. On this field trip, the focus is on three locations of the Campus: the walls, a rooftop and last but not least some park trees.
rooftop are good places for lichens
Caloplaca citrina (lichen)
Amblystegium serpens (Moss)
Asplicia calcaria (white) & Caloplaca citrina (yellow) (lichens)
Atrichum undulatum (Moss)
Brachythecium undulatum (Moss)
Flavoparmelia caperata (lichen)
Cladonia cariosa (lichen)
Cladonia digitata (lichen)
Cladonia furcata (lichen)
Evernia prunastris (grey-green) & Xanthoria parietina (Yellow) (both lichens)
Orthothrichum affine (Moss)
Hypnum cupressiforme (Moss)
Hypogymnia physodes (lichen)
Lecanora muralis (Lichen)
Lunularia cruciata (Liverwort)
Rhytidiadelphus squarrosus (Moos)
Peltigera rufescens (lichen)
Lecanora caesia (white) & Xanthoria parietina (yellow)
Physcia tenella (lichen)
Polytrichum formosum (Moss)
Xanthoria parietina (lichen)
Sacrogyne regularis (lichen) - white spot on the left
Grimmia pulvinata (left) & Tortula ruralis (right)
Verrucaria muralis (lichen)
Pleas note: This time, I've mentioned no determiner, because some names would be to long. If you want the full name check literature or site like wikispecies.