Negev Desert Rhubarb - a self-irrigating plant

Press Release
to IMRA
June 30, 2009

The wonders of evolution:
Desert rhubarb - a self-irrigating plant
*Researchers from the University of Haifa-Oranim have managed to decipher
the unique self-watering mechanism of this plant in the Negev desert, which
harvests 16 times more water than other plants in the region*

Researchers from the Department of Science Education-Biology at the
University of Haifa-Oranim have managed to make out the "self-irrigating"
mechanism of the desert rhubarb, which enables it to harvest 16 times the
amount of water than otherwise expected for a plant in this region based on
the quantities of rain in the desert. This is the first example of a
self-irrigating plant worldwide.

The desert rhubarb grows in the mountains of Israel's Negev desert, where
average precipitation is particularly low (75 mm per year). Unlike most of
the other desert plant species, which have small leaves so as to minimize
moisture loss, this plant is unique in that its leaves are particularly
large; each plant's rosette of one to four leaves reaches a total diameter
of up to one meter. Prof. Simcha Lev-Yadun, Prof. Gidi Ne'eman and Prof.
Gadi Katzir came across this unique plant growing in the desert while
studying the field area with students of the Department of Science
Education-Biology of the University of Haifa-Oranim, and noticed that its
leaves are unusually large and covered with a waxy cuticle. They observed an
exceptionally ridged structure on each leaf, forming a leaf structure that
resembles the habitat's mountainous topography.

The scientists explained that these deep and wide depressions in the leaves
create a "channeling" mountain-like system by which the rain water is
channeled toward the ground surrounding the plant's deep root. Other desert
plants simply suffice with the rain water that penetrates the ground in its
immediate surroundings.

The findings have shown that the natural selection process has resulted in
the evolution of this plant's extremely large leaves, which improved its
ability to survive in the arid climate of the desert. The results of
experiments and analysis of the plant's growth - in an area with an average
annual rainfall of 75 mm - 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. This is 16 times the amount of water
harvested by the small-leafed plants of the Negev desert region. When the
research team watered the plant artificially, they observed how the water
flows along the course of the leave's 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 experimental conditions, water penetrated
the ground only as deep as 1 cm.

"We know of no other plant in the deserts of the world that functions in
this manner," the researchers concluded.

Amir Gilat, Ph.D.
Communications and Media Relations
University of Haifa
Tel: +972-4-8240092/4