The leaf surface secretes a thin layer of organic acids that dissolve nutrients directly from the dust.
Instead of relying on the soil for their nutrients, plants can get some of these essential elements from airborne particles.
Leaf feeding is already well established in agriculture: farmers spray liquid nutrients onto crops. But some plants can also absorb nutrients from the dust that lands on their leavesthe researchers report on April 8 in New plant scientist. The team says this route could be an underestimated food source in dusty, nutrient-poor ecosystems.
“Plants are not like animals; they can’t move,” says Anton Lokshin, a plant biologist at Ben-Gurion University of the Negev in Beersheba, Israel. “They must therefore have strategies to absorb food and nutrients from the environment.
To study the contribution of foliar uptake, or uptake through leaves, Lokshin and his colleagues studied three species—pink cistus, Greek sage, and spotted germander—at a field station in the Judean Hills of Israel. This region receives a lot of dust from the Sahara and the Arabian Desert. Over three months, the team grew 12 plants of each species, treating six with volcanic dust directly on their foliage and leaving the rest untreated. The team chose volcanic dust because it contains a distinct signature of rare earth elements that allows researchers to distinguish nutrients derived from dust from those derived from soil.
Plants whose leaves had been dusted showed a spike in micronutrients such as iron, nickel, manganese and copper in the shoots. The team did not detect a net accumulation of phosphorus in plant tissues, but Lokshin explains that this is because phosphorus moves quickly through plants. His previous research showed that plants can indeed absorb phosphorus from dust through their leaves.
Mineral uptake in roots remained virtually unchanged, even in a parallel experiment where dust was applied directly to the soil. In soil, dissolved phosphorus and iron face immediate competition from microorganisms and minerals that chemically bind to these nutrients before roots can access them.
However, Lokshin says, such competition does not exist on the leaves. He said the leaf surface creates a distinct chemical environment by secreting organic acids that can help dissolve nutrients in the dust.
Combining field measurements with data on dust deposition and soil nutrients from other regions, the team estimates that foliar uptake could provide up to 17 percent of soil iron supply in the western United States and up to 12 percent of soil phosphorus supply in the eastern Amazon. According to the researchers, during Mediterranean dust storms, these atmospheric contributions can match or exceed what the soil provides.