双语：化石研究新发现 带你解密古树成长之迷

英语自学网

　　A joint research project by scientists from China, the UK and the US has
discovered how the earliest trees on earth grew.
        　　中英美三国科学家发起的一项联合研究项目，发现了地球上最古老的树木是如何生长的。
        　　Cladoxylopsida, technically a species of fern, appeared around 390 million
years ago. Researchers from the Nanjing Institute of Geology and Palaeontology,
Cardiff University and the State University of New York conducted the research
based on well-preserved fossils of tree trunks unearthed in northwest China’s
Xinjiang Uygur Autonomous Region. The species became common more than 100
million years before dinosaurs existed. The density of carbon dioxide in the air
dropped at that time, allowing tetrapod vertebrates to transition to living on
land. The scientists found that the early tree trunks were composed of numerous
individual strands of xylem, the plant’s water-conducting cells. The structure
allowed the tree to have several sets of annual ring networks, compared to just
one set in modern trees.
        　　枝蕨纲确切地来说是蕨类植物的一种，存活于3.9亿年前。来自南京地质古生物研究所，加的夫大学和纽约州立大学的研究人员在西北维吾尔族自治区发现的、保存良好的树干化石基础上，展开了研究。早在一亿多年前恐龙存在时，这个物种就很常见了。研究进行时，空气中的二氧化碳浓度下降了，使得四足脊椎动物转移到陆地上生活。科学家发现，这个古老的树干是由很多单独的木质部组成的，木质部是植物运输水分的细胞。比起现代的树木只有一套年轮，这个结构让这棵树有几套年轮。