Science Diary: Redwoods - Straw: The Pulse of the Planet daily radio program offers free legal online mp3 downloads, exploring the world of sound in nature, culture and science, with audio adventures, world music, extraordinary sound portraits, science diaries, and nature ring-tones; an amazing sonic experience.



Airdate: Aug 11, 2008
Scientist: Steve Sillett

Click for more shows on...
 PLANTS ,Forest ,Trees ,water


Science Diary: Redwoods - Straw

Buy button
Imagine sucking water through a 300-foot straw; giant redwoods do this, in effect, every day.
Transcript:

music; ambience drinking straw sucking water; forest ambience

Thats the sound of water being sucked through an 8-inch drinking straw. Well now, imagine being on a balcony 30 stories high and using a 300-foot straw to drink from a water glass on the ground. Well, giant redwood trees routinely pull groundwater into their 300-foot crowns, and thats a lot of suction power. So much power, in fact, that it can shut down the growth of a tree. Welcome to Pulse of the Planets Science Diaries, a glimpse of the world of science from the inside.

As trees get taller, they've had to pull water further from the source at the ground. And that imposes water stress on the leaves and on the conduits that are moving that water. And it's imposing restrictions on photosynthesis.

Thats physiologist George Koch, who made this recording high up in the canopy of a California redwood forest, in the company of buzzing insects. As you may remember from school, photosynthesis is the process by which plants turn sunlight into sugar, and carbon dioxide into oxygen. And its the engine that drives the growth of a tree. But if the worlds tallest trees overdo the suction, it can actually shut down their growth.

You know, if you suck super-hard on a weak straw, the straw collapses. And then you can't pull anything through it anymore. And although the tree's straws, so to speak, they don't collapse, they do fail and if there's enough suction pressure on them, an air bubble can be pulled in, and that blocks the flow of water through those conduits. And that's one of the problems that we think these tall trees encounter. And the only way to completely avoid that is for the tree to close down the little pores in the leaves that allow water out and carbon dioxide in. They have to limit their photosynthesis. And that may be why these trees grow more slowly as they grow taller.

Pulse of the Planets Science Diaries are made possible by the National Science Foundation. Im Jim Metzner.

music







 
Science Diary: Redwoods - Straw