'Christmas Trees' Water Secret Revealed
Rossella Lorenzi
Discovery News
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Christmas trees wouldn't be so popolar this time of the year if it weren't for microscopic valves 
scattered inside their woody trunks, U.S. researchers have discovered.
Conifers, including Christmas trees, dominate many of the world's ecosystems and include the tallest plants, sequoias, (Sequoia sempervirens) and the oldest living organisms, the bristlecone pine. (Pinus longaeva).
Yet these trees suffer a severe handicap: the "pipes," or conduits, that carry water up from the roots through the trunks are 10 times shorter than in angiosperms, or flowering trees. The trees make up for the handicap with unique, specialized, highly-efficient valves placed in "end walls" at both ends of the water conduits, John Sperry, a University of Utah biology professor, and colleagues reported in the current issue of Science. "Without these valves conifers would be much less common than they are, and conceivably their survival might be marginal," Sperry said Known technically as "pits," the valves are disk-shaped membranes.
In flowering trees they are homogeneous, and feature microscopic pores through which the water seeps. In conifers, the valve membranes boast what is known as "torus margo," a structure that resembles a bird's eye view of a circular trampoline.
"It's like a trampoline in that the torus is the mat, and the margo represents the supporting springs with holes between them. The margo holds the torus in place just like springs hold the trampoline in place," Sperry said.
Water cannot pass through the central torus, but easily flows through the margo pores, which are about 100 times larger than those in flowering tree valves.
Rossella LorenziDiscovery News
____________
Christmas trees wouldn't be so popolar this time of the year if it weren't for microscopic valves
scattered inside their woody trunks, U.S. researchers have discovered.Conifers, including Christmas trees, dominate many of the world's ecosystems and include the tallest plants, sequoias, (Sequoia sempervirens) and the oldest living organisms, the bristlecone pine. (Pinus longaeva).
Yet these trees suffer a severe handicap: the "pipes," or conduits, that carry water up from the roots through the trunks are 10 times shorter than in angiosperms, or flowering trees. The trees make up for the handicap with unique, specialized, highly-efficient valves placed in "end walls" at both ends of the water conduits, John Sperry, a University of Utah biology professor, and colleagues reported in the current issue of Science. "Without these valves conifers would be much less common than they are, and conceivably their survival might be marginal," Sperry said Known technically as "pits," the valves are disk-shaped membranes.
In flowering trees they are homogeneous, and feature microscopic pores through which the water seeps. In conifers, the valve membranes boast what is known as "torus margo," a structure that resembles a bird's eye view of a circular trampoline.
"It's like a trampoline in that the torus is the mat, and the margo represents the supporting springs with holes between them. The margo holds the torus in place just like springs hold the trampoline in place," Sperry said.
Water cannot pass through the central torus, but easily flows through the margo pores, which are about 100 times larger than those in flowering tree valves.
