How do lichens eat? Features of lichens, their structure and reproduction

The world of nature is unique and inconceivably diverse. Every year, scientists make more and more discoveries that reveal to us the extraordinary prospects of studying the world around us. But quite familiar living organisms, which the person knows from time immemorial, are still capable of surprising. Take, for example, lichens. They are simple, but the features of their life activity are very unusual.

Do you know how lichens eat? This is really a unique process, which is worth describing in detail.

Difficulties in knowing

In general, they are quite difficult to study, because they represent a symbiosis of completely different organisms. Each lichen is formed by the symbiosis of autotrophic algae and heterotrophic fungus. It is clear that first we have to study the biochemistry and vital activity of each organism separately. Such a method of studying their physiology gives many errors and errors, and therefore scientists have a huge number of questions, not all of which have answers. However, the researchers still managed to identify common patterns.

Internal structure

In general, the whole body of a lichen is a massive interlacing of fungal hyphae, inside of which there are colonies of autotrophic algae. Today in science distinguish the following types of lichens:

• Homeome varieties (Collema). The cells of the photobiont colonies (algae) are scattered along the body in a chaotic manner.
• Heteromeric (Peltigera canina). In the transverse section, it is possible to clearly see the layers of thaloma (hyphae) and algae.

Most of all there are lichens, the structure of which is based on the last principle. In this case, the entire top layer is formed by a particularly dense mesh of mushroom tissue, which protects the lichen body from the negative effects of the external environment. In addition, the fungus prevents excessive drying quickly (but it does not always help).

The next layer contains a colony of autotrophic algae. In the center is the core of the lichen, which is a tight cord of interwoven hyphae of the fungus and the autotrophic colony. This "rod" has a dual function: on the one hand, the lichen stores water in the core. On the other hand, it is a peculiar skeleton of a given organism. In the lower part there are rhizins. This is a kind of anchorage, by means of which the lichen clings to the substrate. It should be remembered that the full set is not found in all species.

Some species of lichens (cyanolipers) are characterized by the fact that in their structure there are highly localized colonies of cyanhydrate. In these species, the division into layers is particularly well pronounced. So how do lichens eat? The answer to this question is directly related to the peculiarities of the process of photosynthesis in them.

On the process of photosynthesis

There are thousands of studies that are devoted specifically to the characteristics of photosynthesis in these symbiotic organisms. Since about 10-15% of their volume is occupied by alga, which gives them practically all the nutrients, there are many questions about the intensity of the process. Strange as it may seem, the simplest measurements have unequivocally shown that the intensity of photosynthesis in lichens is much lower when compared with higher autotrophic plants. So, when making an analogy with ordinary potatoes, the ratio will be 1:16.

But how to explain quite comfortable life in such spartan conditions? In general, nothing particularly complicated in this. The fact is that autotrophic higher plant organisms are "awake" for most of their life, while lichens in some localities almost all year are in a half-dried state, in anabiosis. Of course, they have enough miserable amounts of nutrients to support life.

Here's how to eat lichens. 7th grade in biology schools can study this topic in more detail, but in this case the standard educational program does not provide answers to many important questions. For example, when the process of formation of organic substances for food is slower, and when - a little faster?

What determines the intensity of photosynthesis in lichens?

It should be noted that the intensity of this process depends on a variety of very diverse factors. It is also important that chloroplasts, when covered with a dense layer of hyphae, receive much less light than similar formations in higher autotrophic plants and even algae. In principle, the difference is not so significant.

It should be noted that the maximum value of the process of photosynthesis is observed when the illumination is within 4000-23000 lux. This can be found in the main habitats of lichens: tundra, forest-steppe, light northern forests. In those areas where the intensity of illumination is much higher, intensive production of dark organic pigment (parietin) begins in the body of the symbiotic organism, as well as substances specific for lichens (atranorin, for example).

The organic substances obtained as a result of photosynthesis are completely analogous to those of higher plants. They are used for trophic purposes. Here's how to eat lichens. 7th grade of the general education school studies the processes of their life activity very superficially, although this topic is large and extremely interesting. We bring to your attention extended information that may not only be interesting, but also useful.

The process of breathing

It is easy to guess that the production of nutrients directly depends on the breath. In contrast to photosynthesis in lichens, it is intense: 0.2-2.0 mg CO₂ per hour produces only one gram of symbiotic organism. If you carefully read the information at the top of the article, you probably understood that about 85-90% of the lichen's mass is in the weight of the mycobiotic. To put it simply, in oxygen, the fungal part is more in need than the autotrophic alga. Since lichens eat under normal conditions not too regularly (the cause is severe climatic conditions), a large part of the nutrients are stored in their tissues.

Like photosynthesis, the process of breathing directly depends on the percentage of water.

You should know that the minimum level of breathing, which is necessary to get some amount of energy from nutrients, the lichen retains almost under any conditions (suitable for life, of course). This process is possible with the following temperature ranges: -15 to +30, +50 ° C. But the optimum temperature regime is in the range from +15 to +20 ° С. With the cooling, the use of oxygen begins to predominate. And when the temperature is raised above +35 degrees, both processes are approximately equalized.

There is a known case where a lichen (a photo of this species is in the article), brought to one of the Moscow museums by an expedition of the Royal Archaeological Society, quietly restored its vital activity, being placed by one of the employees in a flower pot with slightly damp earth. But by that time he had been in an absolutely dry, closed box for exhibits for almost 90 years and most of the time he was deprived of even light!

It is not surprising that modern biology is so interested in these organisms. Lichens probably have many more secrets, the disclosure of which, perhaps, will significantly stimulate the development of medicine.

Scientists have proved that the basic principles of breathing lichens are subject to the same patterns as in the case of higher autotrophic plants. But there are also differences, the main one of which is a slightly different priority between the absorption of oxygen and the release of carbon dioxide. In addition, they are phenomenally resistant to the effects of drying, low and high temperatures. Not without reason mosses and lichens can grow even in Arctic conditions.

Temperature conditions

The most favorable temperature for photosynthesis in lichens is from +10 to +25 degrees Celsius. But the ability to absorb carbon dioxide in them is maintained up to -25 degrees. This is a very remarkable feature of lichens, which distinguishes them from higher plants and even algae. At a temperature from -5 to -10 degrees, the intensity of assimilation of carbon dioxide is almost more than in more comfortable conditions. In many plants, in this case, ice forms in the intercellular space, which simply ruptures the cells.

In contrast, lichens on trees, whose trunks literally breaks the severe northern climate (cracking frosts), feel great at the onset of a warm season.

Features of water exchange

Researchers came to the conclusion that lichens differ in a special, highly specific type of water exchange. The fact is that the water in their body is contained in spaces between strong hyphae. When it freezes, it does not bring much harm, and the process of photosynthesis and nutrition continues to occur. However, even with an increase in temperature to +35 degrees Celsius or more, the process of photosynthesis practically stops, which crucially distinguishes lichens from plants.

The amount of water that will be enough for normal life depends on the family. Thus, bushy lichens are capable of photosynthesis and the production of organic substances for food almost completely dehydrated. The thicker the body, the more it can accumulate moisture, the less it evaporates.

This is especially important for lichens, as in most cases they grow in very difficult conditions, when more or less regular water supply is absolutely not guaranteed. Under such conditions, any plant would have died. Lichen also feels good even in conditions of real deserts and the Arctic.

Regulation of liquid exchange

One can understand that the regulatory function of water metabolism in these organisms is arranged in a completely different way than in higher plants. Since they have virtually no specialized systems for this. For example, the absorption of water in them occurs extremely quickly, but only due to its usual absorption by the entire surface of the body. You can conduct a simple experiment: pour a small amount of water on the table and put a piece of tissue or toilet paper on the puddle.

As you can see, the water instantly absorbed, since the paper structure has a good adsorbing ability. The same happens in the case of lichens. So, we considered the episode with a long-dried out specimen, which was once brought by the expedition. When the employee put the lichen in a flower pot, he simply instantly absorbed such a volume of liquid, which he had enough to restore life.

Some bushy lichens are able to absorb a huge amount of liquid, the weight of which is up to 300% of their own. Other types (colleges, leptogiums) increase in size by 400-3900%! If we talk about the minimum water content, it is approximately 2% of the dry matter weight of the lichen. Such a lichen (the photo you will find in this material) does not look like a living organism at all.

About the rate of water release

As in the case of toilet paper, the body gives the body a symbiotic body pretty quickly. In just an hour, the lichen, which has just absorbed almost a liter of liquid, can dry up to a fragile state. Thus, the "productivity" of these organisms is extremely cyclical: the development of trophic substances can drastically change not only during the season, but also for one or two hours!

In recent years, scientists have learned that some species of lichens living in the tundra (Evernia prunastri) can literally use "crumbs" of sunlight, occasionally breaking through a layer of snow. Simply put, they do not end with photosynthesis even in winter.

Reproduction of lichens

In addition, the features of lichens consist in the presence of three ways of reproduction:

• Vegetative.
• Sexual.
• Asexual.

A fungus, that is, a mycobiotic, can reproduce in all ways, whereas algae is capable only of autonomic division. Spores of the fungus are located in special bags. Ascomycete lichens use two main groups of fruit bodies for the reproduction process: apothecia and perithecy. Their characteristics are as follows:

• Apothecia is an ordinary bed of round shape. On it are bags, which are located in between normal, endless hyphae. This open layer is called the Hymenium.
• Peritetium is similar to the almost completely closed structure of a spherical shape. Spores are released through special holes that are located on the surface of the fruit sphere.

Some species can also form asexual spores, pycnospores (pycnoconidia). The place of their formation is pycnidia. These pouches are spherical or somewhat pear-shaped, which are highly specialized hyphae. Picnidia is easy to recognize, as they look like black dots on a bed.

When spores wake up, under suitable conditions they quickly give rise to new hyphae, which form the body of a new lichen. They (hyphae) also penetrate into cells of autotrophic algae, after which the formation of a new organism actually ends.

Value

In general, mosses and lichens are of enormous importance. In the tundra and the arctic desert, they are often the only autotrophic organisms that can accumulate nutrient organic substances under extremely unfavorable conditions. Simply put, it is these organisms that are the source of food for those few herbivores that can live in such harsh places. In addition, only lichens on trees, even in conditions of our climate, often allow us to survive the winter, for example, moose and roe deer.