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They reveal new evidence about the first plants that inhabited the Earth

A CONICET researcher, together with a Swedish colleague, found signs that would promote a new paradigm about where and when
Science
14 September, 2019

A CONICETresearcher, together with a Swedish colleague, found signs that would promote a new paradigm about where and when life emerged from water and began to colonize continents.

A Swedish Argentineresearch team, in which a CONICETresearcher participated, discovered new evidence that would determine a new milestone in the origin and radiation of terrestrial vegetation. The finding was published in the journal of the Swedish Geological Society of the British publisher Taylor & Francis.

“ What we find are the oldest trilete spores in the world. Why are these spores so important? Because they would be from the group of vascular plants or their most immediate ancestors, that is the most related earlier plants, which did not yet have a well developed vascular system and would be between 6 and 8 million years older than those previously known from Saudi Arabia,” explainsClaudia Rubinstein. Principal researcher at the Argentine Institute of Nivology, Glaciology and Environmental Sciences (IANIGLA, Conicet-Uncuyo-Gob. Mza.).

The first steps of life out of water is one of the most important biotic events of all biological evolution because it produced profound and irreversible changes in continental and marine ecosystems; and in the climate, because plants are considered to have contributed to the reduction of carbon dioxide and a cooling that gave rise to origin to one of the most important glaciations in the history of the earth, at the end of the Ordovician. “Plants had a fundamental impact on changes in the composition of the atmosphere, making the land habitable and allowing the colonization of the continents by more evolved organisms. When and where these first plants appeared is fundamental to understanding the evolution of life and serves, among other things, to build phylogenetic trees and place the base where plants migrated from aquatic life to terrestrial life,” Rubinstein says.

There are few records about this event, there is no fossil evidence about these first terrestrial plants and therefore the reconstruction of this episode is carried out by specialists studying microscopic organisms called palinomorphs, which are the spores produced by the first plants and which are now found in rocks. sedimentary.

According to the researcher, the terrestralization of the vegetation took place in a staggered way, first embryophytes appeared, like the small and simple current liver plants, similar in their appearance to those we recognize today as mosses. These more primitive plants produced palinomorphs called cryptospores. Then, vascular plants emerged, the oldest records of which are recognized today by their trilete spores.

The finding represents a paradigm shift in the evolutionary history of plants since all the models interpreted up to now had the origin of terrestrial plants to the Paleocontinent Gondwana: “This is important because until today, both the oldest cryptospores, and the oldest trilete spores, had been found in what Gondwana was. But now, for the first time, we find this evidence in what was the paleocontinent Baltic, which included present-day Sweden, and we should think that the plants could have originated not in Gondwana but in another paleocontinent that was separated at the time,” he says.

The new data allowed the researchers to construct some hypotheses about what might have favored the plants to emerge from the water and begin to populate the continents: “We found the spores in a region of central Sweden, in 23 samples of a drilling that reached 71 meters deep. We know the age well because there are different groups of marine fossils that allow the strata to be accurately dated. In addition, there are layers of volcanic ash where dates are made with isotopes and are very precise. That is very important because we are relating these layers of volcanic ash with the appearance of terrestrial plants. In the sea that was surrounding what is now Sweden there was what is called a “super volcano” and we think that those huge masses of ash that were released probably contributed, because they were the suppliers of phosphates, nitrogen and other nutrients that were integrated into the soils that were forming, promoting the development of plants, ” concludes Rubinstein.

Source: conicet.gov.ar

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