Botanic Superlatives: The Desert's Only Self-Watering Plant

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Botanic Superlatives: The Desert's Only Self-Watering Plant

April 28, 2011
04:00pm
Photo by: Ori Fragman Sapir

Among the valleys and foothills in Israel's Negev desert is a plant that can water itself, in a manner of speaking. A study of desert plants is a study of adaptive behaviors—the dry, hot climate demands it—but the desert rhubarb (Rheum palaestinum) is the only known desert-dwelling species to have evolved a self-irrigating mechanism.

DesertRhubarb

Photo credit: Prof. Gidi Ne'eman, University of Haifa 

By all appearances, the rhubarb is an anomaly in the landscape; most desert plants exhibit two hallmark design features: small leaves to minimize moisture loss, and a shallow but wide root system to absorb the rare rainfall before it evaporates when reaching the ground. The desert rhubarb's morphology is a design departure: each plant's rosette leaves (one to four) span a diameter of up to one meter each. A network of deep grooves channel water along the leaves' veins, funneling the accumulated moisture to a deep taproot. The leaves' topography mimics that of its mountainous habitat: carved canyons and peaks that drain water into sloping valleys. "That ignited our imagination," says Professor Simcha Lev-Yadun, a co-author of the paper.
 
In the Negev desrert, a scarce rainfall averages just 75 mm annually. The desert rhubarb's design assures that it receives more than its fair share: each plant irrigates about 4.2 liters of water each year, while the largest plant claims 43.8 liters. That's 16 times more than any other plant in the region. The desert rhubarb thrives by adopting the appearance of its harsh habitat—a design that allows it to live as if it were in the lush Mediterranean seaside.

Correction: The article has been updated to read "The Desert's Only Self-Watering Plant", rather than "The Only Self-Watering Plant."

Anna Laurent is a writer and producer of educational botanical media. Photographs from her forthcoming field guide to Los Angeles are available for exhibition and purchase at the author's shop.