Cycads are open plants similar to palms in appearance, formed in the early part of the Permian, and for a very long time provided food for herbivores as forest shrubs. a new one, Nature ecology and evolution Research published in the journal examined the remains of ancient cycad leaves, and the results Duke University to explain.
The twilight of cycads came before the final collision with dinosaurs, but we lost most of their species by 66 million years. Currently, only a few of its species live in the tropics, they are rare and endangered, and not all species obtain nitrogen thanks to nitrogen-fixing bacteria that live in symbiosis with them in their modified roots. The researchers conducted compositional tests on the leaves of ancient cycad fossils, originally with the aim of obtaining information about the contemporary atmosphere. Since all modern cycads obtain nitrogen through symbiotic bacteria, the researchers thought that ancient cycads might have worked similarly. However, analysis of the messages showed otherwise!
Analysis of most fossils representing ancient cycads showed that these plants did not contain symbiotic nitrogen-fixing bacteria, as all of these species represented extinct cycads.
Plants accumulate other isotopes of nitrogen in their leaves when they extract it themselves, and others when this is done by bacteria that live in symbiosis with them. This type of symbiosis with bacteria has evolved in the plant world on several independent occasions. Plants provide their bacteria with sugars in exchange for valuable nitrogen.
Cycas Armstrongy – One of the few species of cycads alive today.
Source: Natural World
We obtained information about the ancient atmosphere mainly through chemical analysis of sediments and marine life. But recently, specialists are trying to obtain information by applying some of the methods used for these measurements to the remains of terrestrial plants. Dr. Michael Cape, head of the research, spent about 10 years conducting these tests. “When I started the project, there was no published data on nitrogen isotopes from leaf fossils.” It took him some time to adapt methods developed for marine life to land plants, and then he had to find fossils that museum collections were eager to get rid of. During testing, the tested piece is destroyed.
“The few fossils representing the ancestors of extant cycads that were not very old — 20 to 30 million years old — showed the same nitrogen data as extant cycads,” Kipp said. This means they lived with nitrogen-fixing bacteria, whereas based on fossils of ancient extinct cycads, they did not have symbioses.
It’s not entirely clear how nitrogen-fixing bacteria helped some cycads survive. They may have been better able to maintain their competitive edge among the fast-growing angiosperms that were already dominant at the time, or they may have survived dramatic climate change more easily.
