Regulation Mechanisms of Nitrogen-Doped Carbon Dots in Enhanced Maize Photosynthesis under Drought Stress
Chuanxi Wang, Yusong Yao, Le Yue, Feiran Chen, Xuesong Cao, Jing Li, Hanyue Yang, Nan Zhang, Tianxi Liu, Zhenyu Wang, Baoshan Xing
Abstract
Herein, greenhouse experiments were designed to reveal the role of nitrogen-doped carbon dots (N-CDs) in enhancing maize drought tolerance. Two humidity conditions were created: adequate watering (soil moisture, 75%) and drought stress (soil moisture, 35%). Corn seedlings were harvested after spraying the N-CD solution (5 mg·L –1 ) on maize leaves for 5 days. The results indicated that foliar application of N-CDs increased the net photosynthesis rate (28.6%) of maize, and the fresh and dry weights of roots and shoots increased by 224.5, 360.0, 230.8, and 63.3% under drought stress, respectively. N-CDs showed high reactive oxygen species (ROS)-scavenging activity, resulting in enhanced superoxide dismutase activity (26.7%) and reduced malondialdehyde enzyme activity (18.9%). Besides, N-CDs could be used as light-harvesting materials to improve the light utilization efficiency, upregulate psbA gene expression (81.7-fold), and promote fast synthesis of the D1 protein, which could repair photosystem II under drought stress. Therefore, foliar-sprayed N-CDs could improve photosynthesis through multiple pathways under drought stress: light harvesting, photoprotection, and light repairing. Then, N-CD exposure reduced the corn yield loss under drought by nearly 30% compared with those of the control groups in a full life cycle study. Therefore, this study found for the first time that N-CD-enabled nanoagriculture could ensure crop growth and yield under drought stress, which would be important for global crop cultivation and a promising alternative to deal with the global climate change.