Enhanced leaf photosynthesis, grain yield, rice quality and aroma characteristics in rice grains (Oryza sativa L.) with foliar application of selenium nanoparticles

The potential of selenium nanoparticles application for rice with higher yield and quality, especially in great selenium bioavailability and rich aroma, is a crucial objective. In this study, a two-year field experiment was conducted to investigate the influence of selenium nanoparticles (Se NPs) foliar spraying on the grain yield, rice quality, selenium bioavailability and aroma formation. Our results demonstrated that Se NPs foliar application significantly increased the activities of peroxidase, superoxide dismutase and catalase (POD, SOD and CAT), and decreased the malondialdehyde (MDA) content to increase the SPAD value and net photosynthetic rate in flag leaves at 10-25 days after heading, which finally increased the grain yield by 1.3-3.7 % for improved grain filling, compared to CK. The increased grain filling also contributed to better rice quality, like higher taste value (2.4-6.9 %) and breakdown value (32.2-48.0 %), as well as lower amylose content (5.1-15.9 %), chalkiness grain rate (8.4-49.2 %) and degree (11.5-50.4 %). Meanwhile, Se NPs application improved the selenium bioavailability by increasing the selenium content and proportion in the rice edible parts. The further analysis indicated that the Se NPs application primarily enhanced the proline content and proline oxidase activity from heading to 10 days after heading, improving the initial synthesis of ^Δ1-pyrroline-5-carboxylic acid (P5C) for the vital 2-acetyl-1-pyrroline (2-AP) production during 10-25 days post-heading, which promoted the remarkable increase of the final 2-AP content (5.0-19.8 %). These findings showed that Se NPs can be practically applied as the foliar fertilizer for quality improvement, selenium bioavailability enhancement and aroma enrichment in rice grains.