W.HEAT WASH one of the first plants to be domesticated and is now the most widely distributed crop in the world. So it sounds unlikely that there is still much to learn about what makes it thrive. Yet some 12,000 years after the relationship between humans and wheat began, a wheat plant has been caught doing something unexpected. It got itself a dose of much-needed phosphorus when its leaves took on a coating of desert dust.
The plant (or rather plants) in question were owned by Avner Gross of Ben Gurion University of the Negev, Israel. As Dr. Gross spoke of this year’s meeting of the American Geophysical Union, which took place online in the first half of December, his study was inspired by walks he had taken near Neve Shalom, his hometown in the Judean hills. . On it he often saw leaves of plants completely covered with dust and carried there by sandstorms from the Sahara.
He noticed that this dust might not be the light-blocking nuisance it seemed at first glance. On the contrary, it could be beneficial because of the growth promoting elements such as phosphorus it contains. Until then, botanists had assumed that phosphorus in dust deposited on a plant was of little value because it is contained in an insoluble mineral called apatite. This makes it unavailable for absorption. Dr. Gross, however, reasoned that plants that evolved near deserts, the source of nearly all naturally occurring dust in the atmosphere, may have developed a way to exploit it.
He and two colleagues, Sudeep Tiwari, also at Ben Gurion, and Ran Erel of the Gilat Research Center, began experimenting with a few varieties, wheat and chickpeas (the 17th most planted crop in the world), both of which are native to the Middle East. East came. East. As a control, they also grew some maize, a plant from America that developed in a much less dusty environment.
First, after establishing them as seedlings, they starved their charge of phosphorus until signs of deficiency emerged, such as yellow leaves. Then they scattered desert dust on the leaves of half of the specimens of each species, taking measures to keep it from reaching the ground. After this, although the dust-dosed corn continued to suffer from phosphorus deficiency, the wheat and chickpea plants brightened up and grew to more than double that of their raw lab mates. Moreover, these species were clearly ready for the arrival of the dust. As soon as a phosphorus shortage was announced, two things happened. Their leaves became hairier and therefore better at catching dust. And those leaves also began to secrete acidic liquids that could dissolve any incoming apatite, promoting phosphorus uptake.
The fact that plants can absorb phosphorus through their leaves is not in itself news to farmers – as this was established in the 1950s. But until now, the practical consequence of such knowledge has been to spray crops with liquid fertilizers derived in turn from apatite-containing rocks treated with acid. Leaf dusting could be an alternative and more efficient way to provide desert crops with the phosphorus they need, Dr. Gross said. And maybe not just that one. His next plan is to look at avocado and cocoa trees, which originated in tropical regions of America that regularly receive a useful transatlantic dose of Sahara dust carried west by the trade winds. It will be interesting to see if they have the same tricks as wheat and chickpeas.■
This article appeared in the Science and Technology section of the print edition under the heading ‘Good catch’