Algae and lichens do not have much in common. But this is only at first glance. The most important of them is how their body is structured - the thallus.
Types of Multicellular Organisms
It would seem, how can organisms consisting of a dozen or more cells differ? However, depending on the features, their body can have a fundamentally different structure. For example, in higher plants, cells similar in structure and function are combined into groups to form tissues. Each of them has its own structural features, which are closely interconnected with the functions performed. For example, a leaf of plants is formed by integumentary, main storage and photosynthetic, conductive and mechanical tissues.
But the Volvox organism is also formed by many cells. However, each of them functions separately. These cells are not specialized. They are surrounded by a common shell, forming colonies.
What is a thallus
The thallus is a structure that also consists of many cells. They are identical in structure, and each works as a separate organism. Thallus cells are tightly adjacent to each other, so visually their combination creates the appearance of an organism consisting of tissues and organs. In fact, only representatives of higher plants with leaf-stem structure have these structures.
Types of thalli
Tall, slan, thallus - these are all the names of the vegetative body, consisting of cells of the same type. They differ in a rather wide variety. Filamentous thalli are divided in one plane. They represent one or more rows of cells. Similar structures are characteristic of cyanobacteria and various departments of algae - green, brown and ochrophyte. If individual threads grow together, a false-tissue thallus is formed. It is quite voluminous and is found in representatives of brown and red algae. But in fungi, mycelial thalli are most often observed. They consist of separate threads - hyphae. Their combination forms the whole fruiting bodies of mushrooms. The yeast-like thallus consists of individual cells or their decaying chains. This structure determines its ability to bud.
There are unicellular thalli. So scientists call monadic or flagellate cells of zoospores of algae and animal sex cells. Amoeboid thalli are widespread in nature. This group includes cells of some groups of algae that can form pseudopodia or pseudopods.
What organisms have a thallus?
As you can see, the talln structure is characteristic only for individual representatives of wildlife. These include all departments of algae, lichens and mushrooms.
Thalli also have higher spore plants at the stage of the overgrowth. For example, in fern-shaped, it has the appearance of a small plate on which germ cells develop over time. When they merge, a zygote is formed - a fertilized egg. From it, a green leafy plant develops, which is an asexual generation of fern-shaped.
Tall mushrooms, algae and lichens are characterized by their individual level of organization and functioning. Let's consider each of them in more detail.
Algae thallus
Algae are the very first plants on the planet. Inhabited in water, they do not need real tissues. These are typical thallic organisms that are widely distributed on Earth and have a wide range of uses. In addition to the thallus, algae has another multicellular structure. These are rhizoids, partially fulfilling the function of roots, but also not forming tissues. A typical organism with such a structure is kelp - thallus, reviews and descriptions of which are known to everyone. In everyday life, this seaweed is also called seaweed and is consumed due to valuable nutritional qualities.
Types of Lichen Thallus
These thallic organisms are a unique symbiosis of fungi and blue-green algae. The structure of the thallus of the lichen is represented by individual hyphae, between which cyanobacterial cells are scattered. A crust forms above and below this formation. This is a compacted layer of fungal hyphae. Depending on the shape of the thallus, lichens are leafy, scale-like or bushy. Moreover, this type can easily be determined with the naked eye. So, scale lichens are crusts that grow tightly together with the substrate. Most often they grow on stones or rocks. Leafy lichens have a lamellar body with a wavy edge. Their thallus is attached to the substrate, which may be wood, stones or soil, using a short leg. Bushy lichens usually have branched thalli. They can grow both on the soil and on the branches of large trees and on a rocky base. The color of lichens is very diverse: white, yellow, blue and even black.
Features of life
The thallus is primarily a vegetative body of organisms that implements the process of their asexual reproduction. In many species of algae, a process of alternation of generations is observed. Moreover, sporophyte prevails in their life cycle. This is a generation that propagates asexually by dividing cells and separating parts of the thallus. The nutrition of thalli of different types depends on the features of their structure. For example, in a lichen, fungal hyphae absorb water with dissolved nutrients from the soil, and cyanobacterial cells are capable of photosynthesis. Algae are also autotrophs. But the fungi carry out only soil nutrition, absorbing water with the help of hyphae.
The value of thalli
The structural features of thalli make its owners quite unpretentious and widespread organisms, which often have valuable properties. For example, kelp. Thalli, reviews of which are known to everyone, are valuable fruiting bodies of mushrooms and thalli of lichens. They are a source of food for many species of animals and even humans, as they are rich in proteins and trace elements. There is an opinion that even the manna from heaven, which the Almighty sent to people, is nothing but a type of lichen.
The main function of this structure for organisms is vegetative propagation. Individual parts of the thallus can separate, giving rise to young organisms. With the help of the thallus, the nutrition process also occurs. The thalli of algae and lichens provide them with organic substances that are formed during photosynthesis. They are also important suppliers of oxygen on the planet. Myths of mushrooms are able to enter into mutually beneficial cohabitation with the roots of trees, which is called mycorrhiza. Bright examples of such organisms are boletus and boletus. The amazing fact is that a plant with mycorrhiza receives several times more water from the soil than the same tree without it.
So, the thallus is a structure that forms the body of algae, fungi and lichens. It consists of individual cells and does not form specialized tissues. Therefore, the body of these organisms is not divided into separate organs. In algae, the root function is performed by rhizoids, which also do not form tissues, and by the thallus of fungi it is formed by separate threads - gifs. The main function of the thallus is asexual reproduction and nutrition of organisms.