Carbon dot-embedded hydrogels promote maize germination and growth under drought stress

Abstract

Herein, tannic acid-derived carbon dots (TACDs) embedded gelatin hydrogels (GTACDs) were formed by hydrogen bonding and electrostatic interactions. TACDs (10 ppm) improved the swelling ratio, water retention ratio, modulus (G′ and G′′) and compressive stress of gelatin hydrogels. GTACDs (10 ppm) coated maize seeds (Zea may L.) could increase the germination rate by 19% and the shoot and radicle lengths of maize seedlings (6th day) by 19%, 139.0% (p < 0.001) and 32.2% (p < 0.001), respectively. Also, the fresh weight of shoots and roots (30th day) increased by 124.0% (p < 0.01) and 124.2% (p < 0.05) and increased the dry weight of shoots and roots by 106.3% and 181.9%, respectively. The net photosynthetic rate (A), stomatal conductance (Gs) and transpiration rate (E) increased by 111.9%, 141.0% and 132.7% (p < 0.05), respectively. In the early stages of germination, GTACDs (10 ppm) as seed coating could absorb soil moisture and release TACDs entering seeds and up-regulate the expression of aquaporin (AQP) genes of the radicles. Meanwhile, TACDs eliminated ROS produced from roots and transported to leaves to improve photosynthesis under drought stress. Furthermore, GTACDs had a positive impact on soil biochemical properties, significantly increased the rhizosphere soil of TC, TN, TIC and TOC, and the relative abundance of beneficial rhizosphere microorganisms. These results demonstrated that GTACDs can promote maize germination and growth with low environmental risk. Therefore, GTACDs would be a prospective measure for environmentally friendly agricultural technology in response to drought stress.