"In the struggle for existence, the conifers should have lost, because when angiosperms appeared, they had fancier valve jobs. That’s the feeling of a story introduced by Elizabeth Pennisi on Science Now.
“Those of us who celebrate Christmas tend to take fir and spruce trees for granted around the holiday season,” she quipped, “But without a special modification that allows these trees to efficiently transport water, we might be hanging our ornaments on a ficus instead, according to a new study.” She explained:
---In order for photosynthesis to occur,
---tall trees must supply their uppermost leaves with water,
---which is pulled up from the roots by evaporation.
Angiosperms such as oaks and willows accomplish this using a series of centimeters-long, tube-shaped cellular pipes.
Tiny valves made of cellulose membranes connect each “pipe” and help keep air bubbles out.
Christmas trees and other conifers have much shorter pipe cells, however, and therefore must use many more valves than angiosperms. This should create more resistance and make it harder for them to transport water. But they don’t have any trouble at all, says John Sperry, a plant biologist at the University of Utah in Salt Lake City.
Sperry’s team measured water flow in 18 conifers, including bald cypress, junipers and redwoods, and compared results with 29 species of angiosperms. There was no essential difference. Conifers hoisted the water with equal ease, despite the shorter pipe cells.
Q: How do they do it?
A: The reason, says [Jarmila] Pittermann, has to do with key.jpg)
differences in the valves.
Angiosperm valves are simple membranes full of miniscule pores.
In conifers, the valves consist of a circle of impermeable tissue surrounded by porous tissue. The conifer’s pores are 100 times larger than those in angiosperms and allow water to pass through relatively easily. This efficiency more than makes up for the additional valves on the way to the tree top, Pittermann says.
The researchers said that this helps scientists understand water
transport in wood. “But the work also points to how conifers, which predate angiosperms and are often considered primitive, were able to survive once angiosperms populated Earth,” Pennisi explains. Without these very special cells, one biologist claimed “there wouldn’t be any conifers anymore” – presumably because they could not compete against the angiosperms.
*In the paper, the authors did not explain how or when the unique structure of the conifer valve evolved. They just said that without the adaptation, angiosperms would have a 38-fold advantage in water transport:
Angiosperms such as oaks and willows accomplish this using a series of centimeters-long, tube-shaped cellular pipes.
Tiny valves made of cellulose membranes connect each “pipe” and help keep air bubbles out.
Christmas trees and other conifers have much shorter pipe cells, however, and therefore must use many more valves than angiosperms. This should create more resistance and make it harder for them to transport water. But they don’t have any trouble at all, says John Sperry, a plant biologist at the University of Utah in Salt Lake City.
Sperry’s team measured water flow in 18 conifers, including bald cypress, junipers and redwoods, and compared results with 29 species of angiosperms. There was no essential difference. Conifers hoisted the water with equal ease, despite the shorter pipe cells.
Q: How do they do it?
A: The reason, says [Jarmila] Pittermann, has to do with key
.jpg)
Angiosperm valves are simple membranes full of miniscule pores.
In conifers, the valves consist of a circle of impermeable tissue surrounded by porous tissue. The conifer’s pores are 100 times larger than those in angiosperms and allow water to pass through relatively easily. This efficiency more than makes up for the additional valves on the way to the tree top, Pittermann says.
The researchers said that this helps scientists understand water
transport in wood. “But the work also points to how conifers, which predate angiosperms and are often considered primitive, were able to survive once angiosperms populated Earth,” Pennisi explains. Without these very special cells, one biologist claimed “there wouldn’t be any conifers anymore” – presumably because they could not compete against the angiosperms.
*In the paper, the authors did not explain how or when the unique structure of the conifer valve evolved. They just said that without the adaptation, angiosperms would have a 38-fold advantage in water transport:
"The superior hydraulics of the conifer pit are crucial for minimizing sapwood resistivity. If conifer tracheids had the pit resistance of angiosperms, their sapwood resistivity would increase by 38-fold…. This, added to the narrow diameter range of tracheids, would make it much more difficult for conifers to compete effectively with angiosperms….
We conclude that the evolution of the torus-margo membrane within the gymnosperm lineage from homogenous pits was equivalent to the evolution of vessels within the angiosperms. The towering redwoods and the sweep of the boreal coniferous forest exist in no small part because of this clever microscopic valve."
Q: What did evolution have to do with this story, really?
the tree?
---The results were not what evolutionists expected.
Conifers ruled the Jurassic forests, then along come angiosperms with superior plumbing, and there should have been no contest. Those old, primitive conifers should have gone the way of the dinosaurs, and our Christmas trees would look very different.
Q: Sweep away the Darwinian mythology, and what remains?
A: Two well-designed, highly successful groups of plants."
CEH
