Modern Express News (Reporter Ariya) Angiosperms occupy most of the plant world and have always attracted the attention of botanists. A fossil of paleoplanet from 237 million years ago has a "cross-border" identity, posing challenges to traditional theory... Recently, a research result hosted by Wang Xin, a researcher at the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences - "Prestic Carpel from the Middle Triassic of Spain" was published in the internationally renowned academic journal "Plant", providing a new perspective for understanding the origin of angiosperms.
plants also play "cross-border"? Surprise in fossils
Angiosperm, also known as flowering plant , is the most prosperous and widely distributed group in the plant world today. "There are currently about 300,000 to 400,000 known angiosperms on the earth, accounting for more than 90% of the diversity of in the plant world." Wang Xin said that angiosperms are not only an important ecological factor for the origin of in , but also an important biological resource on which people rely for survival.
Imagine the ancient earth, even if there are lush forests everywhere on the land, no flower is blooming. One day about 100 million years ago, angiosperms arrived late. They decorate the earth with bright colors and a wide variety of flowers, which makes them particularly beautiful.
From gymnosperms to angiosperms is a very important "leap" in the history of plant evolution. However, despite the unremitting efforts of hundreds of years, the origin of angiosperms is still a difficult problem faced by botanists.
△ Triassic Transboundary pattern specimen
"This fossil with a length of about 38 mm comes from plant reproductive organs and its morphological structure is well preserved." Wang Xin told the Modern Express reporter that the fossil he has studied for many years is called "Triassic Crossover". It was discovered more than 20 years ago in the Triassic strata in Spain. The genital organs in this fossil have the appearance of the gymnosperm pine and cypress cones, and have an ovule-encapsulated state similar to that of angiosperm.
Wang Xin introduced that in terms of morphology, the fossil looks very similar to a cone of pine and cypress in gymnosperms more than 200 million years ago. But after careful observation, you will find that the "bud scales" of this "cone" almost completely wrap around the inverted ovule in its axilla. The reason why it is said to be "almost completely wrapped" is because " bud scale " has a slit on its ventral surface. This "slit" means that the reproductive organ has not yet wrapped its ovule to the extent that the angiosperm should have.
△Abdominal suture (arrow) of the lateral unit of the reproductive organ
This morphological structure is similar to the carpel that has not been completely closed in some primitive angiosperms, and the carpel is a structure unique to angiosperms and has never existed in gymnosperms.
challenges traditional theory and reveals the mysteries of plant evolution in multiple dimensions
Although researched for many years, Wang Xin still feels that the origin of angiosperms is a mystery and one of the important and complex scientific issues.
"Its origin process is very complicated, with many paths in the middle, and there may be many changes in each stage. We are tracing back the past with the purpose of knowing all the details of the origin of angiosperms, so there are many things to do." Wang Xin said that this process is like exploring the true nature of history and can be refined infinitely.
Angiosperms have an amazing successful evolution, mainly due to the formation of flowers. As a reproductive organ unique to angiosperms, flowers occupy an extremely important position in the life cycle of plants. In plant ontogeny, flower differentiation marks the transfer of plants from vegetative growth to reproductive growth . Only on the basis of good development of rhizomes and leaves, can they bloom and bear fruit smoothly when they reach a certain period of time.
For a long time, charming and ancient angiosperms have attracted the attention of many botanists like Wang Xin, who have their own opinions and opinions.
△ ovule in a lateral unit accompanied by
△, ventral; arrow points to its bead shank
"The organs on the above-ground part of the plant are generally divided into two categories, one is leaves and the other is branches. The development process of these two organs in modern plants is regulated by different genes."Wang Xin introduced that there are two schools of mainstream views in the academic community: one believes that ovules grow on the top of the branches, rather than on the leaves or the edges of the leaves; the other school believes that in essence, all plant organs evolve from leaves.
According to traditional theory, the basic unit of angiosperm pistils, the carpel, is formed by the macrospore leaves of ovules on the edges, which are longitudinally inclined. In recent years, Wang Xin proposed the "unified theory" that carpels are a composite structure formed by a branch wrapped by a leaf that wraps a long ovules. Previously, this theory has been supported by some fossil evidence and is also in line with the research results of current plant functional genes.
"'Triassic transboundary' is the species closest to angiosperms among gymnosperms, and is likely to be a transitional group between gymnosperms and angiosperms. Its ovule grows directly on the branches, not on the edge of the leaves. "Wang Xin said that the "Triassic Cross-border" fossils can help us reveal more mysteries of plant evolution. Because its morphological structure does not exceed the prediction range of the "unified theory", it is inconsistent with the predictions of previous traditional theories.
(Picture source: Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences)
