New Nanocarrier Helps Keep Iron on Leaves After Rainfall

Iron is essential for plants, but in alkaline soils, ferrous iron (Fe2+) becomes poorly soluble and difficult for plant roots to absorb. Applying iron directly to leaves can bypass this problem, but foliar iron treatments face other issues: Fe2+ is easily oxidized, droplets do not spread well on the waxy surface of leaves, and rain washes away much of the treatment.

In a study published in Carbon, a research team led by Prof. WU Zhengyan and Prof. ZHANG Jia from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences developed a carbon dot-stabilized and coordination-gated nanocarrier formulation (NFCT), which helps protect iron from oxidation and keep it on plant leaves after rainfall.

The newly developed NFCT loads Fe2+ and carbon dots into porous silica particles and is covered with a thin coordination layer made from tannic acid and iron. This structure helps protect the iron during storage and control its release on leaf surfaces. The outer layer improves spreading and helps the treatment remain on leaves after wetting.

NFCT improved the stability of Fe2+ during storage. After simulated rainfall equivalent to 70.7 mm, it retained 72% of the iron deposited on leaves, compared with 26% for commercial EDTA-Fe. Besides, the treatment improved iron uptake in Fe-deficient rice, with leaf iron content reaching 160 μg per gram of dry weight and improvements in chlorophyll levels, biomass and fine-root development.

In a single-site, single-season field trial, NFCT and commercial EDTA-Fe showed no statistically significant differences in the agronomic traits measured under the same iron-equivalent application program. In the rice and adult zebrafish tests included in the study, no evident acute adverse effects from the carrier alone was found.

"The technology shows promise for more effective foliar iron delivery," said Prof. WU. "Further field trials will help us optimize its performance under different conditions."