We, contemporaries, know very little about the first representatives of the plant world. Unfortunately, few of their fossil remains have been found. However, scientists, using fossilized prints left by ancient plants, still restored their appearance, and also examined the structural features of plants that became the first inhabitants of the land.
A science that studies the structural and vital features of fossil plants is called paleobotany. It is paleobotanists who are engaged in the search for answers to questions of the origin of the plant world.
Spore Plant Classification
The first plants on Earth bred using spores. Among modern representatives of the flora, there are also spore plants. According to the classification, all of them are united in one group - “higher spore plants”. They are represented by Riniophytes, Zosterophilophytes, Trimsrophytes, Psilotophytes, Bryophytes (Mossy), Lycopodiophytes (Arachnoid), Equisetophytes (Horsetail) and Polypodiophytes (Fern-shaped). Among these departments, the first three are completely extinct, while others include both extinct and existing groups.
Riniophytes - the first sushi plants
The first land plants were representatives of the flora, who mastered the Earth about 450 million years ago. They grew near various bodies of water or in places of shallow water, which were characterized by periodic flooding and drying.
All plants that have mastered land have a common attribute. This division of the body into two parts - aboveground and underground. Such a structure was also characteristic of the Riniophytes.
The remains of ancient plants were first discovered in the second half of the XIX century on the territory of modern Canada. But for unknown reasons, this find did not interest botanists. And in 1912, near the Scottish village of Rainey, the local village doctor found several more fossilized plants. He did not know that he was holding the remains of the first land inhabitants, but, being very curious, he decided to thoroughly study an interesting find. Having made a cut, he discovered well-preserved plant remains. The stem was very thin, bare, and oblong-shaped processes (similar to elongated balls) with very thick walls were attached to it. Information about the find quickly reached paleobotanists, who found out that the remains found were the first land plants. There were doubts about the name of these ancient remains. But as a result, they decided to go along the simplest path and named extinct plants by the Riniophytes by the name of the village near which they were found.
Structural features
The external structure of the Riniophytes is very primitive. The body branched out according to the dichotomous type, that is, into two parts. They did not have leaves and true roots. Attachment to the soil was carried out using rhizoids. As for the internal structure, on the contrary, it was quite complex, especially in comparison with algae. So, the integumentary tissue had a stomatal apparatus, with the help of which gas exchange and water evaporation processes were carried out. Due to the lack of mechanical tissues, the first plants on Earth were relatively small in height (not more than 50 cm) and stem diameter (about 0.5 cm).
Paleobotanists believe that all modern terrestrial plants are descended from Riniophytes.
Psilophytes are the first land plants. Is this true?
More likely no than yes. The name "psilophytes" really appeared in 1859. This is the American paleobotanist Dawson named one of the plants found. He chose this option, since in translation this word means "bare plant". Until the beginning of the 20th century, the genus of the oldest plants was called Psilophytes. But according to the results of subsequent revisions, this genus ceased to exist, and the use of this name became unauthorized. At the moment, the most fully described genus Rinia gives the name to the entire department of the oldest representatives of terrestrial flora. Consequently, the first land plants were Riniophytes.
Typical representatives of the first land plants
Presumably, the first land plants were tuxonium and rhinium.
One of the oldest representatives of the flora was kuchsonia, which had the appearance of a small bush with a height of not more than 7 cm. The marsh lowlands were a favorable growth medium for it. Petrified remains of kuksonia and its related species were found in the Czech Republic, the United States of America and in some areas of Western Siberia.
Closely related, rhinium is much better studied than kuchsonia. Her body was more massive: a plant could reach a height of 50 cm in height, and a stem diameter of 5 mm. At the end of the stalk of Rini there was a dome in which there were disputes.
The ancient representatives of the genus Rinia gave rise to many plants of the tropics and subtropics. According to modern classification, they are united in the department of Psilophytes. It is very small, because it includes about 20 species. In some ways, they are very similar to their ancient ancestors. In particular, both of them have dichotomous branching. The approximate growth of Psilophytes is from 25 to 40 cm.
Modern finds
Until recently, paleontologists found in sediments older than 425 million years only the remains of primitive triplet spores with a smooth shell. Such findings were found in Turkey. They are attributed to the Upper Ordovician. The found specimens could not shed light on the information about the time of occurrence of vascular plants, since they were single and it was completely incomprehensible to which representatives of the plant species belonged to smooth spores.
But not so long ago, authentic remnants of triletic spores with an ornamented shell were discovered in Saudi Arabia. It was determined that the age of the samples found varies from 444 to 450 million years.
The flowering of vascular plants after glaciation
In the second half of the Ordovician, present Saudi Arabia and Turkey formed the northern part of the Gondwana supercontinent . This, apparently, was the original habitat of vascular plants. For a long historical period, they lived only in their “evolutionary cradle”, while the planet was inhabited by representatives of primitive mossy with their cryptospores. Most likely, the massive resettlement of vascular plants began after the great glaciation that occurred at the border of the Ordovician and Silurian.
Telome theory
During the study of the Riniophytes, the so-called telome theory appeared, which was created by the German botanist Zimmermann. It revealed the structural features of the Riniophytes, which by that time had been recognized as the first land plants. Zimmerman also showed the proposed pathways of formation of important vegetative and reproductive organs of higher plants.
According to the German scientist, the body of the Riniophytes consisted of radially symmetrical axes, the final branches of which Zimmerman called telomes (from the Greek. Telos - "end").
Through evolution, telomes, having undergone numerous changes, became the main organs of higher plants: stems, leaves, roots, sporophylls.
So, now we can unequivocally answer the question "What were the first terrestrial plants called?" Today the answer is obvious. These were the Riniophytes. They were the first to get to the surface of the Earth and became the progenitors of the representatives of the modern flora, despite the fact that their external and internal structure was primitive.