Improve Plant Photosynthesis by a New Slow-Release Carbon Dioxide Gas Fertilizer

In the natural state, the concentration of carbon dioxide in the atmosphere is about 300 μmol mol^-1. Plants need a suitable balance of CO₂ to achieve optimal growth. The optimum CO₂ content corresponding to a high photosynthesis rate is between 0.1 and 1.0% by volume. However, air has only a CO₂ content of 0.03% by volume, so plants cannot use all of their growth potential. The use of fertilizer to assist in the supply of CO₂ increases the rate of photosynthesis. In this work, a slow-release CO₂ gas fertilizer inspired by polyphenol chemistry was prepared to provide sustainable CO₂ that could improve plant photosynthetic capacity and get a higher crop yield. The core-shell structure was designed to confer gas fertilizers slow-release property. Micron-sized calcium carbonate particles with uniform particle size and regularity morphology, as carbon sources for plant photosynthesis, was a core, and tannic acid was coated on it as a shell via oxidative oligomerization and cross-linked by polyetherimide. The structure and morphology of fertilizers were characterized by scanning electron microscopy, X-ray energy dispersive spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. In vitro experiments, the prepared fertilizers were proved to have slow-release properties. And then through net photosynthesis rate, chlorophyll fluorescence parameters, chlorophyll content, leaf area, leaf mass per area, and dry matter to study the effects of slow-release CO₂ gas fertilizers on plant physiology of Brassica chinensis. The results revealed that the slow-release CO₂ gas fertilizers not only had good slow-release properties but also can well improve plant photosynthesis.