New Worlds: The desert rhubarb practically waters itself

Also in this issue: Cool clothes that change colors when affecetd by magnetism.

By JUDY SIEGEL-ITZKOVICH
desert rhubarb 248.88 (photo credit: University of Haifa)
desert rhubarb 248.88
(photo credit: University of Haifa)
University of Haifa-Oranim researchers have detected a unique mechanism in the Negev desert rhubarb plant. Its leaves collect 16 times more water from rain and dew than other plants in the region, so it virtually waters itself. The researchers from the science education/biology department say the species is the first example of a self-irrigating desert plant to be discovered. The species, called a desert rhubarb, grows in the Negev mountains where yearly precipitation totals only 75 mm. Unlike most desert plants, which have small leaves to minimize moisture loss, this plant is unique in that its leaves are particularly large; each rosette of one to four leaves reaches a diameter of up to one meter. Prof. Simcha Lev-Yadun, Prof. Gideon Ne'eman and Prof. Gad Katzir came across this unique plant while studying with students, and noticed that its leaves are unusually large and covered with a waxy cuticle. They observed an exceptional ridged structure on each leaf, resembling the region's mountainous topography. The scientists explained that these deep and wide depressions create a mountain-like system by which the rain water is channeled toward the ground surrounding the plant's deep root. Other desert plants simply make do with the rain water that penetrates the ground in their immediate vicinity. The findings have shown that natural selection resulted in the evolution of this plant's extremely large leaves, which improve its ability to survive in the arid desert climate. The results of experiments and analysis of the plant's growth showed that the desert rhubarb is able to harvest quantities of water that are closer to that of Mediterranean plants, reaching up to 426 mm per year. When the research team watered the plant, they observed how the water flowed along the leaves' depressed veins to the ground surrounding the plant's single root and then penetrates the ground to a depth of 10 cm or more. Under the same experimental conditions, water penetrated the ground only to a depth of one centimeter. "We know of no other plant that functions in this manner," the researchers concluded. HUE FOR YOU Imagine changing the color of your clothing by standing in a magnetic field. University of California-Riverside assistant professor Yadong Yin and colleagues have fabricated microscopic polymer beads that change color instantly when external magnetic fields act upon the microspheres. According to a UPI report, the beads (or magnetochromatic microspheres) have excellent structural stability and are highly compatible with various types of dispersion media such as water, alcohol, hexane and even polymer solutions. "Unlike many conventional approaches, the instantaneous color change occurs with no change in the structure or intrinsic properties of the microspheres themselves," said Yin. What changes instead are the magnetic fields acting externally on the orientation of these microspheres, these photonic crystals. Their work, added Yin, "provides a new mechanism for inducing color change in materials. Now, for the first time, stable photonic materials with tunable colors can be fabricated on a large scale." Their study was published in the online edition of the Journal of the American Chemical Society.