Monday Science Links

This week's science:

• David Bradley at Sciscoop Science looks at why US leaves turn red (and read the "mores", too): The green of the leaves of deciduous trees in spring and summer is caused mainly by the presence of the pigment chlorophyll, which absorbs sunlight for photosynthesis. The change in color to reds and yellows in autumn is not caused by the leaves dying, but by a series of controlled biochemical processes. When the green chlorophyll in leaves diminishes, the yellow pigments that already exist become dominant and give their color to the leaves. Red autumn leaves result from a different process: As the chlorophyll diminishes, a red pigment, anthocyanin, which was not previously present, is produced in the leaf. These facts were only recently discovered and led to a surge of research studies attempting to explain why trees expend resources on creating red pigments just as they are about to shed their leaves.


• Brian at Laelaps gives us a great post on wooly mammoths dying in Virginia: The Saltville site has been studied on and off for about a hundred years, and much of the material dug out of it (especially in terms of plants and small mammals) has yet to be described. Even so, the site has long been known for producing the bones of large herbivorous Pleistocene mammals. American mastodon, mammoth, musk ox, bison, horse, and elk bones have all been found at the site, but there has been no sign of any carnivores. (Or, if there were any carnivore bones found at the site, no one took the trouble to describe them.)


• And Brian also looks at mammoths in Spain: Yet southern Spain in the time of the woolly mammoths was strikingly different from what it is like today. Not only was it colder about 30,000-40,000 years ago, but the landscape was a nearly treeless steppe. The spread of this open, grassland habitat created an edible highway for the woolly mammoths. Despite the fact that living elephants are mixed feeders that are browsers, woolly mammoths were grazers that fueled their large bodies with grass.


• At Skulls in the Stars, a look at the physics and optics of ghost imaging: Ghost imaging is in fact a fascinating and relatively new technique in which a detector can produce an image of an object that it cannot see! The physics behind this effect is somewhat subtle, and resulted in at least one minor controversy since its introduction. Let’s take a look at it...


• And at Zenobia: Empress of the East, Judith looks at Zenobia in autumn: Autumn colour isn't just for trees: Zenobia changes colour too. Zenobia pulverulenta, I mean. And she's a shrub.With nodding white bell-shaped flowers exuding an exotic, spicy, almost cinnamon-like Syrian scent. This Zenobia, however, is no native of Syria. The shrub grows wild only in the moist sandy areas and bogs of the south-east USA. Still, she's a true queen, with gracefully arching branches and blue-green leaves covered with a fine silvery down -- hence her nickname of "Dusty Zenobia". The leaves are now just changing into their autumn finery, a mix of orange, red, and purple colours.

Enjoy!