Phosphorus (P) scarcity constrains plant growth in many ecosystems worldwide. The common paradigm proposes that plants acquire P exclusively from the soil and adjust to P limited conditions by numerous modifications of their rhizosphere. Apart of the soil, terrestrial ecosystems can gain P from external sources through atmospheric deposition. Among atmospheric P sources, desert dust is by far the most dominant, with average P concentrations that are far higher than in most soils. In many ecosystems that are nearby or downwind to major dust sources, dust P inputs can be higher than the soil P pools and increase the supply of P to plants. However, no attempts have be made to study the effects of dust P on plant nutrition and whether plants can adopt specialized physiological mechanisms to exploit dust P. We studied the effects of dust P on the nutrition and growth of wheat and chickpea, two widespread native species to the Middle East where dust storms are a common phenomenon, and on maize that originated in Central America, a region that is rarely affected by desert dust. The plants were grown at two P levels in a controlled greenhouse and were supplied with desert dust through manual dispersion on their leaves.
Results/Conclusions
Our findings show that P starved plants can sustain their nutrition through foliar uptake of P from desert dust captured on their leaves. We found that the foliar uptake of dust P enhanced the growth of P starved chickpea and wheat, plants that originated in ecosystems downwind of deserts, by 115 % and 150 %. Starved maize plants, originated far away from dust sources, showed marginal responses to dust. In chickpea and wheat but not maize, P starvation stimulated the formation of denser trichomes, which increased their dust holding capacity. Furthermore, acidic leaf surface pH and increased exudation of organic acids in P starved chickpea and wheat plants promoted P solubilization. Lastly, leaf structural modifications induced by P starvation enhanced leaf permeability to solutes. Our results suggest that plants that originated from dusty regions acclimate to P poor conditions by adopting foliar physiological traits that facilitate dust P acquisition. As both P limitation and dust deposition are projected to increase due to global environmental changes, plants that exploit dust P would gain competitive advantage over other species.