Rice Seed Germination Improvement by Atmospheric Pressure Plasma Surface Modification With Water Buffer

Atmospheric pressure plasma (APP) treatment improves seed germination by introducing functional groups or etching to change its surface chemical characteristics. This study focuses on improving rice surface properties and reveals that water acting as a buffer plays a key role in APP treatment for the enhancement of seed germination. After a 150-s water buffer APP treatment, the germination percentage of rice seeds increased from 45% to 84% compared with the control group. This improvement can be attributed to the enrichment of surface polar functional groups resulting from the plasma treatment. Surface energy calculations revealed a remarkable increase in the polar component, leading to a substantial reduction in the water contact angle (WCA) from 105° to 40°. This indicates a significant enhancement in surface wettability, rendering it more hydrophilic. Consequently, water uptake from the seed surface also significantly increased. Moreover, X-ray photoelectron spectroscopy (XPS) showed that polar −NO functional groups were enhanced on the seed surface treated by APP with water buffer. The −NO functional groups were formed through a surface reaction between oxygen-excited species OH<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\ast }$ </tex-math></inline-formula> and N<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{2}^{+}$ </tex-math></inline-formula> ions or N<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{2}^{\ast }$ </tex-math></inline-formula> species on the seed surface, which can improve the wettability and provide additional nutrition to seed germination. Consequently, APP seed treatment with water buffer can potentially facilitate seed germination.