New research reveals that plants can absorb essential minerals directly from dust and ash that land on their leaves—a discovery that could change the face of agriculture in an era of climate change.
By Guy Britzman, Angle - a news agency for science and the environment
Amidst the dust clouds of the Israeli desert, in research greenhouses in the south of the country, a scientific journey has been underway for the past decade that reveals an important phenomenon: plants that not only nourish themselves through the air, but do so through dust and ash particles that land on their leaves.
In the study, conducted in the laboratory of Dr. Avner Gross at Ben-Gurion University of the Negev in collaboration with Dr. Daniel Falchan from Ariel University, and presented In the 53th Annual Conference on Science and the Environment, the researchers are examining the phenomenon. "The big innovation in the study is that we are looking at the plant's ability to absorb minerals not only through the roots, but also to absorb nutrients found in ash and dust – such as phosphorus, iron, manganese and copper – directly from the air, through its leaves," explains Anton Lokshin, a doctoral student in the lab. "When dust and ash land on the leaves, they stay there for a long time, and almost without competition with microorganisms, as happens with absorption from the soil. This way they have time to be absorbed."
Lokshin and his colleagues' discovery reveals a nutrient pathway that has been largely ignored in plant science: direct uptake from the air. In a world where climate change is altering soil composition and local climate, understanding the ability of plants to absorb nutrients from the air may play a significant role in future agriculture.
Dust from the Negev desert and ash from the volcano in Sicily
As part of the study, the researchers examined the phenomenon using chickpea plants grown under controlled conditions, alongside those grown in a field experiment at a research station located at the foot of the Mata settlement near Beit Shemesh. In one series of experiments, the plants were exposed to desert dust collected from the Negev, as well as volcanic ash taken from Mount Etna in Sicily. The researchers sprinkled the dust directly on the leaves, and separately, also on the soil around the roots. The results were not long in coming: the plants that received the dust on their leaves showed a significant increase in biomass – that is, their size, and an increase in the content of essential minerals, primarily phosphorus, iron and manganese.
The researchers realized that the reason for this is that plants that feed through their leaves enjoy several unique advantages in this form of absorption: "The problem is that in the soil, when the dust settles, processes of competition with microorganisms, erosion, seepage, and problems with mineral availability in the soil begin. Many of the minerals in the dust do not reach the roots at all," explains Lokshin. "But on the leaves? There is no such competition."
As part of the experiments, the researchers discovered That the polar path – i.e. direct absorption from the leaves – was the main efficient route for absorbing minerals from the dust; the contribution from the roots was much smaller. Furthermore, when the chickpeas were grown under elevated carbon dioxide levels (850 ppm) – i.e. simulating the climate crisis conditions predicted for the future – another problem was revealed: although the plants grew faster and produced more biomass, the concentration of essential minerals in the plant decreased. The result: nutritional dilution of the plant.
"The plant does more photosynthesis when it receives more carbon dioxide, and manages to accumulate more biomass. But then there is a dilution in the concentration of minerals within the plant tissues," explains Lokshin. "That is, if you eat hummus as a source of protein and iron, you will have to eat much more hummus in the future to get the same amount of protein and minerals."
This is where the potential importance of dust and ash comes into play. As carbon dioxide levels rise due to Climate crisisAlthough plants grow faster, they suffer from a depletion of essential minerals that are important for human health and ecosystems. The researchers wanted to test whether dust and ash particles that land on leaves and contain concentrated minerals can serve as a nutritional supplement and replenish some of these deficiencies. The results showed that when the dust sticks to the leaves, the plant is able to absorb the phosphorus and iron from them, thereby improving the mineral values again, even under conditions of high carbon dioxide concentration.
The significance of this discovery goes far beyond the question of plant nutrition alone. Dust and ash, it turns out, also play an important role in the oceans, and the significance is global. Ash and dust particles coming from the deserts of Africa and the Arabian Peninsula are carried on winds and reach the oceans. There, the ash, rich in phosphorus, iron and manganese, is a powerful fertilizer for microscopic algae.
"When there are volcanic eruptions that release huge amounts of dust and ash, they reach the oceans and often lead to algal blooms," Lokshin explains. "Algae, like land plants, photosynthesize; they absorb carbon dioxide and solar energy and use it for nutrition and construction. When they die, some of them sink to the bottom and lead to what is called carbon fixation: the carbon dioxide in the body of the alga – which it absorbed during its life – remains on the ocean floor for many years, which contributes to lowering the levels of carbon in the atmosphere and therefore reducing its contribution to global warming."
This means that ash and dust particles have many contributions: not only do they provide a source of minerals for plants, but they also trigger processes that help reduce carbon dioxide levels in the atmosphere, through its fixation by algae on the ocean floor. Carbon fixation in the oceans is one of the natural mechanisms currently known to slow climate change, and the study by Lokshin and his colleagues highlights the possible contribution of dust and ash to this process.
Intentional fires for the sake of plants
The results of the study convey another important point, concerning the influence Fires On the vegetation. During and after a fire, the plants in the area are exposed to a large amount of ash and dust, which may, of course, harm some of the vegetation in the immediate term – but can also help some of it. Understanding the importance of fire as part of the natural ecosystem is not new. In the forests of Northern Europe (where there is an especially high ability to prevent natural fires), for example, fires are sometimes started deliberately. "In Finland, for example, they create deliberate and controlled fires to redistribute nutrients in the soil," says Lokshin. "They realized that if there is no fire, it will disrupt the natural process of dispersing nutrients in the soil." The results of the study help us understand that plants also know how to absorb nutrients directly through the foliage, and not just through the soil.
When a plant burns, most of the carbon in it evaporates into gas, but the minerals accumulate in the ash, where they are in much higher concentrations than in living tissue. "When a fire occurs, most of the plant's biomass—composed of carbon and water—evaporates, leaving only a few percent of the plant's initial weight as ash. This ash contains most of the minerals that the plant has accumulated over its life, only in a concentrated form that is ten times or more concentrated than the concentration in the original plant before the fire," explains Lokshin. "In this way, we can calculate the intensity of the fire. When it comes to ancient seeds found in archaeological sites, we can estimate what the biomass was before the fire, even in very ancient events."
The understanding that plants are able to utilize dust and ash directly from their leaves opens the door to thinking in new directions: for example, developing varieties that are better adapted to a changing world, developing new fertilization methods, and possibly even strategies for dealing with mineral-poor soils. Understanding how to leverage this ability may allow crops to grow even under difficult conditions, such as those expected due to the climate crisis and declining soil fertility.
"Ultimately, we're showing a kind of global life cycle here: plant photosynthesis, burning, carbon dioxide release, dust dispersion, return to the land and sea, feeding new plants," concludes Lokshin. "The minerals don't disappear, they just migrate. And if we better understand the ways in which plants absorb them, we can better deal with the challenges that lie ahead."
