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[Science] Why do the world’s largest trees have some of the smallest leaves? [Copy link] 中文

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Post time 2017-4-6 15:12:31 |Display all floors
(From Science by Katherine Kornei)--

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Conifers are the world’s tallest, widest, and oldest trees. But they have some of the smallest leaves in the plant kingdom, with most never growing beyond 6 centimeters. To find out why, scientists mathematically modeled how liquid nutrients move through the needlelike leaves of conifers, including redwoods and cedars. They focused on sugars, which are produced in the leaves by photosynthesis(光合作用) and transported through tubes 20 times narrower than a human hair to roots and new shoots. But moving fluid through such a narrow space requires a lot of pressure—provided by water-filled cells lining the tube—and there’s an upper limit to how much water can enter those cells. By comparing the pressure necessary to pump sugars with the maximum pressure provided by the cells, the scientists showed that sugars couldn’t be efficiently moved through tubes any longer than about 5 centimeters, they will report in a forthcoming issue of Physical Review E. This length is consistent with data from more than 500 conifer species, with a few exceptions. Species with unexpectedly large leaves, like some pine trees, may have evolved to optimize light capture or gas exchange for photosynthesis, the researchers note. Among trees, the new findings are limited to conifers, whose needlelike leaves help shed snow. But they may extend well beyond the plant kingdom to help researchers understand other processes, like fluid transport in kidneys.

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Post time 2017-4-6 16:58:50 |Display all floors
No flowers either

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Post time 2017-4-10 23:02:01 |Display all floors
The largest tree in the world is a giant sequoia (Sequoiadendron giganteum) in California's Sequoia National Park. Called General Sherman, the tree is about 52,500 cubic feet (1,487 cubic meters) in volume.Apr 29, 2013
Anger is an acid that can do more harm to the vessel in which it is stored than to anything on which it is poured. Mark Twain

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Post time 2017-4-10 23:04:20 |Display all floors
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Anger is an acid that can do more harm to the vessel in which it is stored than to anything on which it is poured. Mark Twain

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Post time 2017-4-10 23:05:36 |Display all floors
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Anger is an acid that can do more harm to the vessel in which it is stored than to anything on which it is poured. Mark Twain

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Post time 2017-4-11 04:42:23 |Display all floors
Saul Post time: 2017-4-10 23:05

Very beautiful

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Post time 2017-4-11 13:45:38 |Display all floors
Saul Post time: 2017-4-10 23:05

nice pics

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