| 查看: 486 | 回复: 5 | |||
[交流]
Everyday News-World's Oldest Wood
|
Talk about an old-growth forest. Newly described fossils push back the appearance of wood by at least 10 million years. The fossils, including one from 407-million-years-old rocks in France, preserve the remains of stems about 12 centimeters long. The size and arrangement of cells in the cores of the stems, and particularly the presence of long, thin cells (arrows) that span several rings of cells and extend like rays from the center toward the outer rims, are characteristic of wood, researchers report online today in Science. The plants' small size, as well as the presence of thick-walled cells elsewhere in the stems, suggests that wood evolved to efficiently transport water from the soil into the plant. At the time these plants lived, atmospheric concentrations of carbon dioxide were decreasing, which in turn decreased the water-use efficiency of the plants and boosted their need for water, the scientists say. Although the first plants sporting wood were small, subsequent species quickly took advantage of wood's structural strength: In just a few million years, some had attained treelike stature. |
回复此楼» 猜你喜欢
复试调剂
已经有8人回复
-
0831生医工第一轮调剂失败求助
已经有9人回复
-
283求调剂 086004考英二数二
已经有3人回复
-
生物学308求调剂（一志愿华东师大）
已经有6人回复
-
调剂求收留
已经有7人回复
-
272分材料子求调剂
已经有36人回复
-
275求调剂
已经有8人回复
-
一志愿211，化学学硕，310分，本科重点双非，求调剂
已经有20人回复
-
070300化学学硕311分求调剂
已经有19人回复
-
材料与化工调剂
已经有13人回复
★
小木虫(沙发+1，金币+0.5):恭喜抢个沙发，再给个红包
小木虫(沙发+1，金币+0.5):恭喜抢个沙发，再给个红包
 |
2楼2011-09-15 22:23:57
★
小木虫(金币+0.2):抢了个小板凳，给个红包
小木虫(金币+0.2):抢了个小板凳，给个红包
 |
3楼2011-09-15 22:24:01
4楼2011-09-15 22:24:35
gzrhubu
木虫 (正式写手)
- 应助: 0 (幼儿园)
- 贵宾: 0.041
- 金币: 3208.3
- 散金: 604
- 红花: 16
- 沙发: 21
- 帖子: 866
- 在线: 277.1小时
- 虫号: 1190372
- 注册: 2011-01-15
- 专业: 有机分子功能材料化学
5楼2011-09-15 22:25:27
 |
6楼2011-09-15 22:29:01
5