Israeli scientists say they have discovered that plants native to desert regions can help themselves to food by catching dust on their leaves and extracting what they need, in a breakthrough that could help farmers to reduce the use of environmentally damaging chemical fertilizers.
Experiments show that native Israeli plants such as wheat and chickpeas grow more hairs on their leaves when they are short on phosphorus — a building block needed by all cells of living things. The hairs trap moisture, which makes them stickier and better able to catch dust particles from the air, and the leaves secrete acid that dissolves the phosphorus into a liquid form that the plant can absorb.
Dr. Avner Gross, a Ben-Gurion University of the Negev geographer, said he had a eureka moment during a walk outside his home at Neve Shalom, in the Judean Hills, outside of Jerusalem, immediately after a dust storm almost two years ago.
“I’ve been working on dust for six to seven years and have seen it contains various elements [needed for plant growth],” Gross told the Times of Israel. “It already seemed logical to me that plants would use it. Then in January last year, after a big dust storm, I went into the forest near my home and I noticed that dust had stuck to all the leaves. I wondered if there was more to this than met the eye.”
Gross, whose research has focused on the impact of climate change on the natural environment, approached Dr. Ran Erel of the Agriculture Ministry’s Volcani Agricultural Research Organization, who was initially skeptical but willing to experiment.
The two of them chose to look at phosphorus, which is so essential to plants and to the fertilizer industry. They took pots of lettuce, starved them of phosphorus, and then sprinkled desert dust on the leaves, ensuring that none touched the soil. The plants doubled in size.
Gross unveiled the discovery at this month’s online meeting of the American Geophysical Union, and is working on publishing his findings in a peer-reviewed journal. It was earlier reported on by The Economist.
He surmised that the discovery could help cut down on the use of fertilizers that rely on phosphates.
“This could be very interesting with great potential,” Gross said. “It raises agricultural and climate questions. This knowledge could lead to a way of reducing chemical phosphate use by dusting the leaves, as well as possibly recycling dust, rather than mining it by taking it from building sites or quarries,” he said.
While researchers believe the amount of dust created by human activity is increasing, scientists are unsure whether a warming planet will result in increased dust or less of it. Gross’s findings suggest that in a less dusty world, some plants will lose out.
“Climate change is causing the earth’s deserts to move away from the equator towards us. So in areas with more dust, like Israel, dust-adapted plants will have a big advantage, but in other areas, where the dust disappears, this might have an adverse effect on plants,” he said.
Farmers have known for some time that leaves can be sprayed with liquid phosphorus, but have assumed that the plants only absorb it after it has been extracted and industrially broken down with acid.
That certain plants can physically change their leaf surface when they need phosphorus and secrete the acid themselves to break it down is new to science — and apparently what plants in Israel and other dusty regions have been doing long before chemical fertilizers were invented.
The irony is that the source of the phosphorus for the dust and for the chemical fertilizers is the same — rocks found in parts of the Levant, including Morocco, Algeria and Israel (where Israel Chemicals Ltd extracts it from the Negev desert), as well as China and the US. The difference between sprinkling natural rock dust onto crops and producing industrial phosphorus is that phosphate mining is costly and produces mountains of toxic waste that can pollute the environment. It is also being mined in such quantities that it is expected to run out worldwide by the end of the century. Chemical fertilizers, meanwhile, can denude soil of nutrients.
After the initial experiments, Gross and Erel linked up with Dr. Ilana Shtein, an expert in plant anatomy from the Eastern R and D Center in the West Bank city of Ariel, and hired Dr. Sudeep Tiwari of the Volcani Center, who is carrying out the actual experiments.
Tiwari has been taking different kinds of phosphorus-enriched desert dust and sprinkling it on the leaves of several species of food plants that have been deprived of phosphorus in advance.
The results so far are that native plants, such as wheat and chickpeas, increase in size, compared to control plants which are also starved, but not given any dust. By contrast, corn, which hails from South America, is not evolved to deal with dust, and thus does not have the ability to pull out the phosphorous.
The tests have also shown that dusting the leaves generates more growth than dusting the roots. That may be because leaves have a larger surface area and can thus capture more dust particles, Gross said.
The experiments are now being expanded to tomatoes (native to non-dusty parts of central America), avocado (from tropical rainforests that receive Saharan Desert dust), and native Israeli trees, such as oaks.
The researchers are also looking at whether plants can extract other minerals from dust, such as iron, potassium, and zinc.
“From a genetic point of view, plants are more complex than people,” Gross said. “They must find whatever they need without moving.”