New Insights Into The Hidden Origins Of Flowering Plants
Read new research from OSGF president Sir Peter Crane on the origins of angiosperms, recently published in Nature.
New Insights into the Hidden Origins of Flowering Plants
A new treasure trove of beautifully preserved plant fossils discovered in China, which date from 125-million-years before present, provide new insights into the origins of flowering plants (angiosperms). These discoveries were presented in a new study published in Nature on Wednesday, May 26th, 2021.
In flowering plants, the embryo develops inside the seed, which has a two layered seed coat early in its development. The inner of these two layers is thought to be equivalent to the single layer that forms the seed coat in all other seed plants, but the outer layer — the second integument — is a characteristic feature of angiosperms that is not seen in other plants. Explaining how this second integument arose is a vital for understanding the evolutionary origin of angiosperms.
Examination of a large number of exquisitely preserved fossil seed-bearing structures from Inner Mongolia, China, which date from the Early Cretaceous epoch, suggest that the recurved cupule in which the seeds are borne are directly equivalent to the second integument in angiosperms, including in their unusual, recurved structure. Comparison of these fossils with the seed-bearing structures of other fossil seed plants from the ‘Age of Dinosaurs’ suggests that similar recurved cupules are seen in a broad group of now extinct, plants and that the variation in cupule form and the number of seeds in each cupule most likely reflects variation related to the biology of pollination and seed dispersal in these ancient plants.
More information is needed from other well-preserved fossils to further resolve the origin of angiosperms, but the new fossil material from Inner Mongolia is an important step forward that helps focus further research, including on how other characteristic features of flowering plants arose, especially the carpel, the structure that ultimately develops into the fruit wall and in which the seeds are borne.
This video, created using X-ray computed tomography, shows progressive longitudinal sections through single seed-bearing structure isolated from the Inner Mongolia chert. As the video proceeds two seeds become visible suspended from the apex of the enclosing seed-bearing structure. Zhahanaoer Chert, Inner Mongolia, China, ca. 126 million years before present.
Bract green; cupule blue; seed brown. Zhahanaoer Chert, Inner Mongolia, China, ca. 126 million years before present.
This research was supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences (2017359), the US National Science Foundation grant DEB-1748286, the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB26000000), the National Natural Science Foundation of China (41790454) and the Oak Spring Garden Foundation.
Additional images of other fossils from the chert in Inner Mongolia, China, and also from lignites in Mongolia, which are of similar age and contain some similar plant fossils can be seen here.