A team led by evolutionary biologist Prof. dr. Sven Gould of Heinrich Heine University Düsseldorf (HHU) has studied the current state of research into the plant colonization of land that took place some 500 million years ago. The findings of this illustrated review study, published by Dr. Mona Schreiber as lead author, have now appeared in the latest issue of the magazine Trends in plant science†
After the formation of the earth, some 4½ billion years ago, it took several hundred million years for the initially fiery globe to cool, allowing the first oceans and land masses to form. The land was barren rock for the next three billion years.
The blue planet with green continents that we know today did not exist as such at that time. For conditions on the continents were largely hostile to life, with much higher volcanic activity releasing toxic gases into the atmosphere, a weaker magnetic field than exists today, exposing the land more to cosmic rays, and a thinner ozone layer to filter out UV light.
This started to change about 500 million years ago when plants began to colonize land. The invasion catalyzed a metamorphosis of the hostile environment, accelerating the transformation of the atmosphere, to lay the foundation for the development of life on land as we know it today. All this could not happen until plants, which had lived only in the oceans and freshwater inland, conquered the continents.
Now Prof. dr. Sven Gould of the Institute of Molecular Evolution at HHU, Prof. dr. Stefan Rensing and Dr. Mona Schreiber, a bioinformatics specialist and artist from the University of Marburg, summarizes the current state of research on land plant colonization in the journal Trends in Plant Science. Their paper was written under priority program 2237 “MAdLand” (Molecular Adaptation to Land), funded by the German Research Foundation. The aim of the MAdLand program is to investigate the beginnings of the evolutionary adaptation of plant organisms to life on land.
The continents only started to turn green after a streptophyte alga moved from an aquatic habitat to coastal zones before transitioning completely to land more than 500 million years ago, in a process involving numerous molecular and morphological adaptations. During the constant changes of the earth, plants showed tremendous adaptability and changed the climate in a crucial way, mainly by sequestering carbon dioxide (CO2) on a large scale.
Terrestrial flora proliferated in a dominant feat, with flowering plants proliferating; today they comprise more than 90% of all known terrestrial plant species. In the history of our planet, land plants have caused several climatic changes, which time and again demonstrate enormous adaptability.
Researchers are studying the genomes of species of evolutionary importance related to terrestrization, including mosses, lycopods, ferns and certain algae, in an effort to advance our understanding of evolutionary processes and molecular adaptation. Their work aims to identify the mechanisms that served to mitigate the hostile living conditions on land that changed over the course of this evolution. Indeed, these may be relevant with regard to climate change, including for crop modification in response to shifting environmental conditions.
Regarding the role of humans in the evolution of the planet, the study’s lead author, Professor Gould, clarifies: “Humans, who have only a short history compared to plants, are indeed responsible for significant changes to the planet on their own and its climate.The extreme rate of those changes is a major problem because nature has little time to adapt.The pace of man-made change accelerated as humans developed agriculture and livestock, leading to steady population growth and freeing up more and more land for agriculture.” In this work, the collaborating authors analyze human influences on climate and discuss the adaptability of plant life to the changes occurring today.
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