The Red of Autumn’s Leaves May Be a Stop Sign for Pests

In the latest development in the ongoing debate about why some leaves turn bright red in the fall, a new study suggests that the color is a signal to insect pests to stay away. Harvard biologist Marco Archetti sought to prove the theory, first put forth in 2001 by the late evolutionary biologist William Hamilton, that the red pigments, or anthocyanins, serve as a plant’s chemical defense. Archetti studied aphids’ survival rates in wild apple trees, which turn more red, compared with farmed trees, which produce more green and yellow leaves. He found that aphids don’t show up as frequently on apple trees that turn red in the fall [ScienceNews]. He also reports in the study, published in Proceedings of the Royal Society B, that once spring came, young aphids who had fed on red trees in the fall were less likely to grow to maturity than aphids placed in the green or yellow trees.

Archetti chose aphids for the study because fall is their mating season: They leave their summer plants to find a good tree for mating and egg laying. Aphids can damage trees in two ways, especially when the new generation hatches in the spring. The insects steal the sap and also spread diseases with their piercing mouthparts that end up as entomological dirty needles. So trees would do well to dodge aphids [ScienceNews]. To test whether the red signals a threat to the insects, Archetti placed nesting aphids in both red- and green-leaved apple trees in the fall of 2007, and found that the next spring, 60 percent of those in green trees had survived, compared with 29 percent in red trees. The reason behind this disparity is unclear, but Archetti’s and other studies suggest that the red leaves either have toxic chemical defenses or hold fewer nutrients for young aphids [ScienceNow Daily News].

Not everyone buys Archetti’s answer to the long-debated question. Environmental scientist David Wilkinson believes that leaves turn red for a different reason: “I think the most likely explanation is that these [anthocyanins] are effectively sunscreens that allow the photosynthesis to continue as the machinery of photosynthesis is broken apart in the autumn” [BBC], he says, while plant geneticist Andrew Flavell thinks that a genetic link between leaf color and fruit taste may be the cause. Florida scientist David Lee said, “The nice thing about this article is that it collects and reports important new data on the phenomenon.” … But he still questions some of the interpretations. And says the paper hasn’t wooed him away from his contention that anthocyanins protect leaf chemistry from light damage at cool temperatures [ScienceNews].

Clearly, the debate is far from over, but researchers all agree that trees must have a really good reason for producing the red pigment. The pigments that produce yellow and orange leaves in the fall are present year-round, and help protect chlorophyll, the molecule at the heart of photosynthesis, from sunlight damage; when chlorophyll is broken down in the autumn those yellows and oranges become visible. In contrast, the red anthocyanins are produced only in the fall. It is a costly job of molecule building for the plant and an enigma to scientists, since the leaves will at that point soon be dropped entirely [BBC News].

Invisibility Becomes More than Just a Fantasy

Two years ago a team of engineers amazed the world (Harry Potter fans in particular) by developing the technology needed to make an invisibility cloak. Now researchers are creating laboratory-engineered wonder materials that can conceal objects from almost anything that travels as a wave. That includes light and sound and—at the subatomic level—matter itself. And lest you think that cloaking applies only to the intangible world, 2008 even brought a plan for using cloaking techniques to protect shorelines from giant incoming waves.

Engineer Xiang Zhang, whose University of California at Berkeley lab is behind much of this work, says, “We can design materials that have properties that never exist in nature.”

These engineered substances, known as metamaterials, get their unusual properties from their size and shape, not their chemistry. Because of the way they are composed, they can shuffle waves—be they of light, sound, or water—away from an object. To cloak something, concentric rings of the metamaterial are placed around the object to be concealed. Tiny structures—like loops or cylinders—within the rings divert the incoming waves around the object, preventing both reflection and absorption. The waves meet up again on the other side, appearing just as they would if nothing were there.


The first invisibility cloak [subscription required], designed by engineers at Duke University and Imperial College London, worked for only a narrow band of microwaves. Xiang and his colleagues created metamaterials that can bend visible light backward—a much greater challenge because visible light waves are so small, under 700 nanometers wide. That meant the engineers had to devise cloaking components only tens of nanometers apart.

Xiang’s group also cleared another design hurdle. A competing team had devised a metamaterial to cloak visible light, but it was just one atom thick, too flimsy to deflect anything more than a single sheet of incoming light. Xiang’s new metamaterials have heft.

Last March José Sánchez-Dehesa and Daniel Torrent, physicists at the Polytechnic University of Valencia in Spain, presented a design that would allow a cloaked submarine to hide from sonar. This technology could also allow an orchestra patron sitting behind a cloaked column to hear music as clearly as one in an unobstructed spot.

In September French and British physicists presented a plan for using metamaterials to shield shorelines from the impact of massive waves. Their proposed device [subscription required] would look like a scaled-up acoustic cloak: concentric circles of posts surrounding a hidden object. When a wave hits them, the posts would redirect it around the object without ever breaking the wave. The researchers say that such a device could be used to protect isolated spots in the ocean—like drilling platforms or low-lying islands—or coastal regions vulnerable to tsunamis.

But the weirdest extension of the cloaking concept is undoubtedly the “matter” cloak described this past year by Shuang Zhang, a postdoctoral associate in Xiang’s lab. Subatomic particles like electrons travel as waves, and Shuang showed how metamaterials could be used to divert an atomic wave the same way the invisibility cloak re­directs a light wave. If such a device could be scaled up to the human-size world (far from certain, alas), it might be able to steer a bullet around a bulletproof cloak.

Too Strange to be True? Tree Found Growing in Man’s Lung

Remember being told when you were a kid that if you swallowed any of the seeds inside an apple, the fruit would start growing in your stomach? And then learning later that it was all a joke? Well…turns out that might not be so far from impossible. The Russian publication Mosnews.com is reporting that a 28-year-old patient was found to have a five-centimeter fir tree in his lung.

Doctors were performing a biopsy on the patient, Artyom Sidorkin, after he’d complained of intense chest pain and was coughing up blood. They suspected cancer, but instead of finding a tumor when they cut the lung tissue, they reportedly found green needles. They continued, in alleged disbelief, to remove an entire branch from inside Sidorkin’s body.

The medical team believes that the blood Sidorkin had been coughing up was a result of the needles poking the capillaries, and that the branch grew inside his body after he swallowed a small bud—since clearly, the branch was not swallowed whole.

Hoax? Or truth? We’ll keep you updated as the story, er, blooms.