From a botanical point of view, lichens do not form an independent taxonomic unit, but are described as a symbiosis of algae and fungi. Each of these organisms is assigned tasks in this connection.The fungus creates the inner body of the growth and protects the algae against drying and mechanical damage.Algae, in turn, create sugar (in the process of photosynthesis), and thus provide food.
Lichens do not have roots through which they can absorb water and are not protected in any way from drying out. They absorb water like a sponge from rain or fog, and later, when needed, turn it into a mist and survive difficult moments in hibernation. This is, in a way, the secret of the lichen's longevity, because by adopting the aforementioned tactic, they can survive for several dozen years.
Of course, as you can easily guess, the growth rate of lichens is very slow. However, time does not play any role for them, as evidenced by, inter alia, the fact that these are organisms that inhabit almost all places on Earth since primitive times.
Lichens are pioneering organisms, because they grow in conditions in which other organisms have no chance.They can be found on trees, rocks, concrete. They are growing on old fences and roofs, at first glance resembling a shell or even mold.
Sometimes they disfigure a covered object, sometimes they make it more beautiful, it is certain that they do not cause any harm to the plants. Because lichens are not parasites, they do not suck water or nutrients from host plants.Some species of lichens prefer sour bark of spruce, birch or alder, others prefer alkaline bark of maples or elderberry.
Lichens are reliable bioindicators of air pollution. They are very sensitive especially to sulfur compounds, i.e. pollutants emitted by industry and the automotive industry.Therefore, these organisms are almost absent in highly industrialized agglomerations and city centers.Our country is inhabited by about 1600 species of lichens, many of which are under strict protection.
How lichens acquire new lands
Lichens form thalluses composed of densely interwoven threads protecting the algae. Underneath the algae there is a core which is a layer of loosely tied fungi.At the very bottom of the lichen there are sticky hairs that connect the body with the substrate.Interestingly, lichens can reproduce sexually and asexually.
If the lichen is multiplied asexually, the lichen particles are dispersed by wind or rain. For this purpose, the growth creates special structures on the surface. These are isidias, i.e. small cone-shaped outgrowths that, when detached, can form a new organism,and soredia (aka bluffs), i.e. single algae cells entwined with mycelial hyphae, in the form of a powder. They are carried by the wind.
