In the conditions of a considerable change in the Ancient Earth, it was necessary to develop new strategies to keep organisms. Nearly 30 million years ago, around half a million years ago, the concentration of carbon dioxide in the atmosphere declined by about one-third to about half a million years before the middle of the orchogen. At that time, the appearance of a new type of photosynthesis was found in plants, C4. The C4 pathways that compacted the plants complemented the former C3 photosynthetic pathway, which means that these species now use two different strategies to collect the energy from the sun.
Researchers believe that the decline in carbon dioxide levels has led to the emergence of plants with this innovation for a long time, but Proceedings of the National Academy of Sciences, Biochemical modeling of the team led by biologists from the University of Pennsylvania and Purdue University's paleoclimate modeling can be an important factor in the emergence of C4 plants.
"The initial origin of C4, which is still very high atmospheric carbon dioxide, is due to the limitation of water," says Haoran Zhou, graduate student of the Faculty of Arts and Biology and the first author in the article. "Later, 5-8 million years ago, there was an increase in C4 meadows because carbon dioxide was low and declining, while carbon dioxide and light intensity were at the same time favorable for C4."
Edol Akchai, a biologist at the Penthouse, said: "We have shown that water efficiency in C4 is sufficient to provide the primary environmental advantage in relatively dry environments." If you only watch the temperature and carbon dioxide, you may not miss the role of water and light. «
According to researchers, C4 factories predict that carbon dioxide levels in the atmosphere will still be competitive, even at the last Oligocene C3.
"C4 could have developed earlier than we thought it was," said Brent Hellicer, a biological scientist who worked with Penn's "Jones Consultant along with Money." "It supports molecular clocks during C4 development."
The first stable compounds that produce photosynthesis in plants with C3 photosynthesis have three carbon atoms; The C4 plants contain four carbon atoms. The C3 pathways are first developed and operate efficiently when the atmosphere is rich in carbon dioxide. However, C4 plants are developed almost a decade from the C3 plants, helping to compress the carbon from the carbon black to the inner layer, thanks to an additional process in the process, capable of effective photosynthesis, regardless of the low carbon level. the cycle is performed. The photosynthetic devices launch this "closed" system that is not directly interacting with outer air, and C4 photosynthesis can reduce the flow of plants less C3 than the C3.
Today, about a quarter of the planet's vegetation is composed of C4 plants. Several important plant species, including corn and sugar cane, have C4. The findings of excavation and isotope research have helped scientists to evaluate this pathway, but these estimates were later than the molecular clock data from the various phylogenetic analyzes of plants, which led to some confusion as to the emergence of certain pathways and dominated by certain ecosystems.
For a closer look at the factors that can support the spread of photosynthetic C4, we have created a multi-layered model of Zhou, Money and Helliker. They refer to variations affecting photosynthesis and variables affecting the hydraulic system, where plants decide to consume more energy in the roots to obtain water, or form a large number of leaf substances that help to absorb light and carbon dioxide, resulting in the loss of white water. In addition, plants can determine the optimal balance of carbon and water loss. The combination of these two systems involves four factors that scientists can use in C3 or C4: concentrations of carbon dioxide, light, temperature and water.
According to their model evolution C4 appeared in two stages. When the carbon dioxide was still high, C4 was formed in warm and dry areas of the globe. But he did not get the competitive advantage of C3 plants several million years later, and when the carbon dioxide was very low, the expansion of the meadows provided bright lighting. In these areas C4 breeding grounds were expanded and C3 hayfields were replaced.
To see how this model interacted with Paleoclimate in the early days of C4 plants, Penn worked with Pearson University's Matthew Hübert, a Paleoclimate model financed by the National Science Foundation for Mycology Climate Modeling and with Associate Professor Ashley Dicks. Using the Paleoclimate data, including climate model release and carbon dioxide levels, temperature and precipitation, researchers have predicted geographical division of C4-C4 plants from the oligocene to the early myocene period of about 30-5 million years ago. They found two areas not previously identified, thanks to the first evolution of C4 plants, especially with the effectiveness of water in the north-west of Africa and Australia.
"These C4 plants have an ecological advantage and are actually two unrecognized two pockets in the world," says Akchay.
"When the Penn team supported us," says Huber, "this is a really new use of Paleoclimate samples, the climatic models are past and future climates and geologically-tested specimens.
Although the research does not explore what might happen in the future due to increased levels of atmospheric carbon dioxide, it can help to understand how plants can respond to current and future conditions.
"Climatic conditions that existed during the modern C4 evolution are likely to be important today," said Hellicer. "If the C4 plant network develops because of the high water content of the carbon dioxide, then these plants can now be found in dry environments, and if their carbon dioxide leads to their evolution and domination, they can be found today in wetlands."
In addition, some scientists believe that, like rice, other important agricultural species can engineer and help increase the production of C4 photosynthesis, the model can help predict the optimal growth of these plants.
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Haoran Zhou et al, C4 photosynthesis and optimistic climate lenses, Proceedings of the National Academy of Sciences (2018). DOI: 10.1073 / pnas.1718988115